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Thermochromic Narrow Band Gap Phosphors for Multimodal Optical Thermometry: The Case of Y3+-Stabilized β-Bi2O3:Nd3+
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Thermochromic Narrow Band Gap Phosphors for Multimodal Optical Thermometry: The Case of Y3+-Stabilized β-Bi2O3:Nd3+
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Cite this: Chem. Mater. 2022, 34, 18, 8198–8206
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https://doi.org/10.1021/acs.chemmater.2c01262
Published September 11, 2022

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Abstract

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The design and development of effective luminescent thermal sensors have been driving technological progress in many different fields ranging from catalysis to biology and microelectronics, to name a few. The ratiometric concept of using the ratio between two luminescent emissions of lanthanide-doped phosphors allows overcoming some limitations resulting from the single emission-based thermometers. A fundamental requirement for the development of effective luminescent thermometers relies on efficient luminescence output, which is not always accessible. Therefore, alternative methods to probe the temperature in a reliable and simple way are still a challenge. Despite the conventional limits of using narrow band gap materials as hosts for lanthanoid ions, a smart design allows for the development of unusual phosphors with appealing properties. By taking advantage of the narrow band gap of Bi2O3 polymorphs, here we demonstrate the potential of the tetragonal Y-stabilized β-Bi2O3:Y3+,Nd3+ system as a multimodal thermometer combining the conventional Boltzmann thermometry based on Nd3+ together with the thermochromism of the host. With the aim of testing this new concept, the temperature dependence of the reflectance spectra was investigated. Moreover, from the application point of view, the chromaticity variations of the material described by means of simple thermometric parameters such as the ratio a*/b* and the hue angle hab are demonstrated to be particularly promising and already implemented in software commonly used worldwide. The results suggest the potential of the strategy of combining narrow band gap semiconductors with lanthanoid ions to design reliable and multimodal thermal sensors, paving the way to a new family of thermochromic and luminescent thermal sensors.

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Introduction

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Narrow spectral bands and long excited state lifetimes are two of the most relevant luminescence features of trivalent lanthanoid ions (Ln3+) exploited to develop unique optical materials for applications ranging from lasers (1) to bio-imaging, (2,3) from anti-counterfeiting (4) to temperature and pressure sensors, (5−7) to name a few.
The design of new Ln3+-activated phosphors with advanced properties also relies on the interaction of the luminescent ions with the matrix. In fact, despite the variety of Ln3+-activated insulator-based phosphors investigated and commercialized, new strategies to develop advanced phosphors implying unconventional materials are still a challenge. In this view, narrow band gap materials, conventionally avoided due to undesired interactions between their electronic band structure and the energy levels of the luminescent centers, have been recently demonstrated to be interesting matrixes for luminescent Ln3+ ions, paving the way to new opportunities. (8,9)
Among the potential narrow band gap hosts suitable to accommodate luminescent Ln3+ ions, bismuth oxide-based compounds are characterized by narrow band gap energies usually exploited in technological fields such as photocatalysis, (10,11) electronic and energy applications, (12,13) ferroelectrics, (12,14) scintillators, (15) topological insulators, (16,17) UV-filters, (18,19) and multiferroics. (13,20) Recently, the narrow band gap of Bi2O3 polymorphs (in the range of 1.5–3.8 eV depending on the polymorphs) was used to selectively tune the luminescent properties of upconverting (UC) lanthanide couples Bi2O3:Yb3+,Ln3+ (Ln = Er, Tm, and Ho) showing the possibility to get a single UC visible or NIR-to-NIR emission line. (8,9) The same strategy was also used to selectively achieve a single red emission in the case of BiVO4:Yb3+,Tm3+. (21) Moreover, it is worth noting that, theoretically, bismuth-based materials are particularly appealing hosts for effective phosphors due to their high refractive indexes, which directly influences the spontaneous emission probability of the luminescent centers.
In recent years, luminescent thermometers were demonstrated to be particularly intriguing to locally probe the intracellular temperature, (22−24) heating effects in microelectronic devices, (25) and also the phase transition temperatures (26,27) and the temperature of catalytic reactions. (28−31) In the field of optical thermometry, by taking advantage of the change with temperature of luminescent parameters such as the emission position, the band shape broadening, the emission intensity, the excited state lifetime, and so forth, many different techniques were adopted as thermal sensors so far. (5) Among them, the ratiometric concept of using the ratio of two luminescent signals (known as LIR, luminescent intensity ratio technique) is nowadays recognized as a successful self-reference method to overcome the lack of reliability of the thermometry based on a single emission band. Interesting strategies based on energy transfer between two luminescent ions, (32,33) the involvement of charge transfer bands, (34) or based on the use of excited state absorption (35,36) have been proposed. However, when two excited states from the same ion are thermally coupled by following the Boltzmann-distribution, the thermometers were demonstrated to be particularly reliable allowing precise temperature sensing, (37−41) with predictable behavior.
An intrinsic limit of all these techniques is the necessity of effective luminescence. In fact, strong luminescence leads to high signal-to-noise ratio, a necessary requirement for suitable thermal resolutions. Therefore, for many materials, the effectiveness of the thermometric performance is hampered by luminescence quenching.
Here, we introduce an alternative strategy to design multimodal thermometers based on thermochromic narrow band gap materials such as Bi2O3 doped with lanthanide ions. To achieve a high degree of reliability, the ratiometric concept is considered to describe different thermometric parameters. The β-Bi2O3:Y3+,Nd3+ system is proposed as a prototype to be used as a multimodal thermal sensor exploiting not only the luminescent properties of the lanthanoid ion (Nd3+) but also the relative properties of its absorptions with respect to that of the host by means of in situ reflectance spectra acquired through a simple setup. Moreover, taking advantage of the narrow band gap energy of the host, colorimetric parameters are discussed and proposed as potential thermometric parameters with the advantage of easy availability in common software daily used.

Results and Discussion

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Nd3+-Doped Narrow Band gap Y-Stabilized Tetragonal β-Bi2O3: Structural and Optical Properties

Bismuth oxide exists in six different polymorphs: (i) the room temperature-stable monoclinic α-phase, (ii) the tetragonal β-phase, the face-centered cubic δ-phase, the body-centered cubic γ-phase, the orthorhombic ε-phase, and the triclinic ω-phase. (42−44) By doping with suitable elements, it is possible to selectively stabilize some of the Bi2O3 polymorphs. In particular, by doping with different amounts of trivalent rare-earth ions (e.g., Y3+, Er3+, La3+etc.), the β- or δ-phase can be stabilized at room temperature. (42,43)
Figure 1a shows the X-ray powder diffraction (XRPD) patterns of the (Bi0.945Y0.05Nd0.005)2O3 system (labeled as β-Bi2O3:Y3+,Nd3+) along with the Rietveld refinement, confirming the stabilization of the pure β-phase. The cell parameters and the results of the Rietveld refinement are shown in Table S1. The tetragonal β-Bi2O3 structure (space group P42/nmc) is characterized by a single site (8g) for Bi3+ and the stabilizer Y3+, which proved to be particularly interesting when the single site is substituted with luminescent ions such as trivalent lanthanides Ln3+. Indeed, the presence of a single substituting site for the Ln3+ ions (in this case Nd3+) allows simplifying the interpretation of the results, thereby avoiding the misleading analyses resulting from signals of multi-site compounds. In addition, the depicted structure in Figure 1b and c evidences the low symmetry site (point group Cs) for Nd3+.

Figure 1

Figure 1. Crystalline and electronic structure of the tetragonal β-Bi2O3:Y3+,Nd3+ polymorph. (a) XRPD pattern along with Rietveld refinement and difference profile. (b) Crystalline structure and (c) local site of substitution for Nd3+ in β-Bi2O3:Y3+,Nd3+. (d) T-DOS and P-DOS projected onto each constituent element.

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To elucidate the origin of the top of the valence band (VB) and the bottom of the (CB), we conducted first-principles calculations using the CASTEP code. Focusing on the VB-top and CB-bottom, the partial density of state (P-DOS) and total density of state (T-DOS) of Y-stabilized β-Bi2O3 are plotted between −8 and 8 eV (Figure 1d). The top of the VB is mainly composed of O 2p orbitals, with a contribution of the Bi 6s and 6p orbitals, while the CB-bottom is mainly constituted by Bi orbitals. The analysis of the P-DOS of Bi evidences the overlap between Bi 6s and 6p orbitals at the top of the VB, a characteristic feature of the post-transition lone-pair metal compounds that can be considered as a fingerprint of the lone-pair asymmetric electron density. (45,46)
From the electronic structure point of view, bismuth oxide-based materials display narrow band gap energies that, from the one hand, can be detrimental for luminescent centers but, from the other hand, can be exploited to control the output emissions. (8,9) The picture of the pellet of the β-Bi2O3:Y3+,Nd3+ sample in Figure 2a clearly evidences the narrow band gap nature of the material. The reflectance spectra of the Nd3+-activated system (Figure 2a) show the typical f–f transitions of Nd3+ along with the edge of the band-to-band absorption of the host.

Figure 2

Figure 2. Electronic structure and optical properties of the narrow band gap β-Bi2O3:Y3+,Nd3+. (a) Reflectance and PLE spectra collecting at 1060 nm along with the picture of the sample. (b) Tauc plot of the Kubelka–Munk function F(R) for the estimation of the band gap energy. (c) Room temperature PL spectrum by exciting at 745 nm. (d) VRBE diagram for Nd3+ in β-Bi2O3:Y3+,Nd3+.

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The optical band gap energy of the material was estimated by the Tauc plot (47) of the Kubelka–Munk function (48) from the diffuse reflectance (R). Figure 2b shows the Tauc plot of the Kubelka–Munk function for both the cases of direct and indirect semiconductors from which the direct band gap nature of the material is clearly confirmed, in agreement with the literature. (49,50) By extrapolating the intercept of the fitted straight line at F(R) = 0 of the (F(R)•hν)2 versus the hν energy plot, a band gap energy Eg of 2.28 eV is estimated.
Together with the reflectance spectrum, Figure 2a compares the specular photoluminescence excitation (PLE) spectrum of Nd3+ collecting at 1060 nm. Even though the same f–f absorption peaks are characterized by the same position, the relative intensity is clearly different with a maximum excitation obtained by exciting through the 4F7/2/4S3/2 excited state at about 745 nm. Moreover, at wavelengths lower than 560 nm no excitation bands are detected, in correspondence with the energy gap of the host.
Figure 2c shows the photoluminescence (PL) spectrum of β-Bi2O3:Y3+,Nd3+ by exciting at 745 nm, characterized by the typical emissions due to the 4F3/2 → 4I9/2 (∼900 nm), 4F3/2 → 4I11/2 (∼1060 nm), and 4F3/2 → 4I13/2 (∼1350 nm) transitions. The decay curve of the PL collected at 1060 nm can be fitted by a single exponential (Figure S1) showing an 4F3/2 excited state lifetime of 80 μs. Such a short lifetime for Nd3+ can be understood by considering the high refractive index of bismuth-based compounds.
Lanthanide-doped luminescent materials are conventionally designed by substituting the luminescent ions into suitable sites of insulators (wide band gap materials). In the case of narrow band gap materials used as hosts, their electronic structure can influence the optical processes from the energy levels of luminescent centers giving rise to new opportunities. If from one hand, narrow band gap materials can strongly quench the luminescence of lanthanide ions due to the creation of non-radiative channels, on the other hand, the control of the relative position between the CB/VB of the host with respect to the energy levels of the luminescent centers can be used to design materials with new properties. For instance, by doping suitable (nano-)semiconductors characterized by direct band gaps with lanthanide ions, it is possible to take advantage of the large absorption cross section of the hosts to enhance the luminescence output from the f–f transitions. However, narrow band gap semiconducting materials that are not able to transfer electrons/holes to the luminescent ions can also be exploited to design smart materials in which this photons’ blocking ability is a real technological advantage.
In the case of narrow band gap materials, the relative position of the top of the VB and the bottom of the CB of the host with respect to the luminescent ion energy levels should be known on an absolute scale in order to properly discuss the optical processes involved. In this view, the vacuum referred binding energy (VRBE) diagram introduced by Dorenbos for a wide variety of materials with respect to the lanthanoid ions (51) was demonstrated to be particularly suitable also for bismuth-based compounds. (52,53) By considering the flatband potential of −4.53 eV of β-Bi2O3 (54) and the estimated optical band gap energy of 2.28 eV, the top of the VB can be fixed at EV = −6.81 eV, while the exciton energy EEX = 2.5 eV allows the CB-bottom at −4.31 eV to be fixed. Considering the average trend for the two polymorphs, (55) these values are consistent with the VRBE diagram reported for α-Bi2O3. (52) In addition, if we consider U(6,A) = 6.55, (52) the position of the energy levels of all the trivalent lanthanide ions can be fixed on the absolute scale, and the VRBE diagram of interest for Nd3+ in β-Bi2O3 is depicted in Figure 2d. The relative position of the energy levels of Nd3+ with respect to the top of the VB and the bottom of the CB shows how the excited states from which the luminescent transitions are originated (mainly 4F3/2 and 4F5/2) are quite far from the CB, excluding the possibility of a direct electron transfer from the excited state to the CB. Instead, the band gap energy estimated at about 2.28 eV well matched the lowest excited state detectable in the PLE spectrum, as evidenced by the vertical dashed line in Figure 2a, suggesting a direct effect of the host for photons with energy higher than its band gap.

Conventional NIR-to-NIR Nd3+-based Ratiometric Luminescent Boltzmann Thermometry

To evaluate the potential of the system as a luminescent thermometer for different applications and investigate the fundamental phenomena involved, the effect of temperature on the PL spectra was investigated in the temperature range of 100–600 K.
In the field of luminescent thermometry, the use of Boltzmann-based thermometers allows a unique degree of reliability. By considering the potential use of Nd3+-activated thermometers as bio-probes, (56−58) the excitation at 745 nm allows exploiting the first biological window in a NIR-to-NIR mode using the 4F3/2-4F5/2 couple as a reliable Boltzmann-based thermometer. In fact, the conventional NIR-to-NIR thermometry, based on Nd3+, is typically achieved by means of the 800 nm excitation (4I9/2 → 4F5/2/2H9/2 transition) exploiting the Kramers doublets of 4F3/2 induced by the crystal field splitting (conventionally labeled as Z1 and Z2) and characterized by a small energy gap with a consequent small value of relative sensitivity. (59,60)
Figure 3 summarizes the NIR-to-NIR thermometric performance of the β-Bi2O3:Y3+,Nd3+ system. The temperature dependence of the PL spectra in the first biological window is shown in Figure 3a evidencing the relative increase of the emission due to the 4F5/2 → 4I9/2 transition with respect to the 4F3/2 → 4I9/2 transition by increasing the temperature. The luminescence intensity ratio (LIR) between these two transitions can be used as a reliable thermal probe: . I5 and I3 are the intensity emissions of the 4F5/2 → 4I9/2 and 4F3/2 → 4I9/2 transitions. The range of validity of the Boltzmann behavior and the energy gap ΔEF between the 4F5/2 and 4F3/2 excited states can be estimated by plotting the logarithm of the LIR as a function of the inverse of the temperature 1/T (Figure 3b) and fitting the linear part through the general Boltzmann law:
where 2 and 1 refer to the general higher and lower excited states of the couple in thermal equilibrium, respectively. The thermometer follows the Boltzmann law in the 350–600 K range, and the value of ΔEF = 926 ± 9 cm–1, estimated from the fit, is in good agreement with the value obtained from the spectra (∼930 cm–1). Instead, by considering the ratio between the emissions from the two Kramers doublets of 4F3/2 (Z1 and Z2) to the higher-lying Stark level of 4I9/2 (), a good linearity of the plot is obtained from 240 to 600 K (Figure 3c), and a ΔEZ = 106 ± 2 cm–1, obtained from the fit, is in good agreement with the value estimated from the spectra (∼120 cm–1).

Figure 3

Figure 3. NIR-to-NIR Boltzmann thermometry. (a) Temperature dependence of the PL spectra in the 100–600 K range exciting at 745 nm spectra, normalized to the 4F3/2 → 4I9/2 emission. Boltzmann plot to calibrate the thermometers based on the ratio between 4F3/2 and 4F5/2 (b) and between the Kramers doublets Z-levels of 4F3/2 (c) with the corresponding linear fits. (d) Temperature dependence of the absolute (Sa) and relative (Sr) sensitivities and (e) repeatability (R).

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The thermometric performance of these conventional Boltzmann thermometers can be evaluated by considering the absolute (Sa) and the relative sensitivities (Sr), defined respectively as
where Q is the thermometric parameter (in this case LIRF and LIRZ).
Figure 3d,e summarizes the thermometric performance for both the thermometric parameters. Being directly proportional to the energy gap between the two thermally coupled excited states ΔE21, the values of Sr of the thermometer that uses the 4F5/2 and 4F3/2 states are higher than the one based on the Kramers doublets. Moreover, the values of Sr and Sa at 300 K agree with the general values of the Nd3+-based Boltzmann thermometers based on the Kramers doublets reported in the literature (summarized in the Supporting Information, Table S2 and Figure S2).
Moreover, a thermal cycling experiment consisting in recording the thermometric parameters of four consecutive heating–cooling cycles was performed, and the repeatability (R) was estimated by the following relationship:
where Qm is the mean thermometric parameter at each temperature and Qi is the result at each specific measurement. The reproducibility is higher than 99% for both the thermometers (Figure 3e).
The emission in the second biological window at about 1060 nm (4F3/2 → 4I11/2 transition) can also be used to design a NIR-to-NIR luminescent thermometer based on the Kramers doublets of 4F3/2 with a linearity in the 240–600 K range and a ΔEZ = 135 ± 3 cm–1 estimated from the fit (Figure S3). Also in this case, the thermometric parameters are quite promising, in agreement with the literature and with a high reproducibility.
It is interesting to note that these results suggest a strong potential of the β-Bi2O3:Y3+,Nd3+ system also in the field of anti-counterfeiting. Indeed, the optical security tags conventionally proposed are based on luminescent species (molecules or phosphors) storing a code linked to a specific spectrum, while the encoding system consists of specific luminescent emission patterns achieved by multi-tags for a higher capability. (4) Therefore, combining the NIR-to-NIR strategy for Nd3+ with the impossibility to excite the system in the UV/blue spectral range together with the Boltzmann-based thermometric performance and the colorimetric/thermochromic properties of the phosphor, it is possible to use the material as a tag with an extremely high encoding capacity.

Multimodal Thermometric Strategy: Exploiting the Temperature-Dependent Narrow Band gap Edge, f–f Transitions, and Colorimetric Parameters

Luminescence can be strongly quenched by many non-radiative processes influencing the reliability of the read-out temperature of the conventional LIR-based thermometers. In this view, the use of absorption (reflectance) instead of the luminescence could broaden the possibility to develop new families of thermometers with suitable performance and high reliability for specific applications.
With the aim of investigating this potential alternative strategy for temperature sensing, the temperature dependence of the reflectance spectra was investigated in the 300–640 K range (Figure 4a). A clear effect of the temperature on the host is evidenced by the change of the reflectance (absorption) edge with the band gap variation (Figure 4a,b). By considering the extrapolation of the optical band gap energy previously reported with the use of the Tauc plot of the Kubelka–Munk function for a direct band gap semiconductor (Figure 4c), the temperature dependence of the band gap energy was evaluated. As shown in Figure 4d, the decrease of the band gap energy with temperature can be fitted, resulting in a linear trend with a slope of (−6.2 ± 0.1)·10–4 eV/K. This behavior could be used as a thermal sensor, but from the application point of view, the automatic calculation of the Eg has some drawback. Instead, the value of reflectance at 650 nm can be used to follow the effect in a simpler way. In addition, to develop a ratiometric thermometer based on the reflectance spectra, the absorption due to the 4F5/2 + 2H9/2 is used. Therefore, we introduce the reflectance intensity ratio (RIR) between the reflectance at 650 and 810 nm as the thermal parameter
where R650 and R810 are the reflectance intensities at 650 and 810 nm, respectively.

Figure 4

Figure 4. New thermometric parameters based on the temperature dependence of the reflectance spectra and colorimetric parameters. Temperature dependence of (a) reflectance spectra (the vertical dashed lines represent the reflectance values used for the RIR parameter), (b) Kubelka–Munk function and (c) Tauc plot for the estimation of the optical band gap energy. (d) Temperature dependence of the band gap energy with the linear fit. (e) Reflectance intensity ratio (RIR) used as the thermal parameter along with the absolute (Sa) and relative (Sr) sensitivities and (f) sketch of the thermometric parameter introduced based on the narrow band gap and the Nd3+ f–f transitions. (g) Thermochromic variation based on the colorimetric parameters a* and b* as a function of the temperature in the a*b* space, (h) thermometric parameter a*/b*, (i) hue angle hab, and relative thermometric parameter values (j) Sa and (k) Sr.

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The temperature dependence of the RIR is shown in Figure 4e along with the absolute and relative sensitivities estimated. The trend of the relative sensitivity shows a maximum of 0.21% K–1 at 550 K. Even though the values are not particularly high, it is important to underline that f–f transitions are only affected to a small extent by temperature in terms of the emission line position with a small error in the identification. Therefore, the use of the reflectance at 650 and 810 nm characterizes the band-to-band transition of the β-Bi2O3 and the Nd3+ absorption band, respectively (Figure 4f), with a consequent reliable thermometer based on reflectance measurements.
With the idea to develop an automatic analysis during the acquisition, the colorimetric parameters a* and b* of the CIELAB color space (CIE 1976 L*a*b* (61)) can be alternatively used. The a*-axis represents approximately the amount of red (positive) or green (negative), while the b*-axis is approximately the amount of yellow (positive) or blue (negative). Figure 4g shows the colorimetric parameters a* and b* as a function of the temperature.
The calculation of such parameters is conventionally implemented in most of the software commonly used in the lab, and they can be easily and automatically measured. The simple ratio between a* and b* is proposed as the thermometric parameter reflecting the effect of temperature on β-Bi2O3:Y3+,Nd3+ in terms of color (Figure 4h). Moreover, an additional promising colorimetric parameter of the CIELAB space suitable for temperature sensing (Figure 4i) is the hue angle hab, defined as:
The study of this parameter gives not only interesting values of relative sensitivity obtained at high temperatures (2%·K–1 at 650 K) but also promising values of absolute sensitivity (Figure 4j,k). The Sa values for the thermometer based on the hue angle hab are higher than 5·10–2 K–1 in the whole temperature range explored. This is particularly important considering the inverse proportionality between Sa and the thermal resolution. (62−64) The hue angle is demonstrated to be particularly promising also with respect to other the common colorimetric parameters calculated in the CIELAB color space (see the results for the chroma Cab* and the color difference ΔEab* in the Supporting Information, Figure S4).
It is worth mentioning that this strategy is particularly interesting in terms of reliability and easy accessibility, being already implemented in common software. Therefore, depending on the temperature range of interest for the specific application, this multimodal system allows the selection of the most suitable thermal sensing mode between the conventional LIR-based technique and the RIR/colorimetric techniques based on the thermochromic behavior of the material.

Conclusions

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In summary, we demonstrate the potential of the Y-stabilized β-Bi2O3:Nd3+ system as a prototype of lanthanide-doped narrow band gap materials for optical multimodal thermometry in which (i) the Nd3+ luminescence can be used to design NIR-to-NIR Boltzmann-based luminescent thermometers and (ii) a fundamental property of the host, such as the temperature dependence of the band gap edge (and corresponding colorimetric parameters) tuning, can be used to design reliable thermometric parameters to be probed by simple reflectance measurements.
The results of the conventional Boltzmann-based luminescence thermometers show interesting performances, in agreement with the literature. In situ analysis of the temperature dependence of the reflectance spectra demonstrates how, being an intrinsic property of the material, the temperature dependence of the band gap shifts along with the Nd3+ absorptions can be easily used to design a reliable thermometer. Moreover, among the common colorimetric parameters calculated in the CIELAB color space, the hue angle hab is demonstrated to be particularly promising in terms of relative sensitivity and reliability with an additional advantage of easy accessibility, being already implemented in software used in the worldwide laboratories. In this context, the approach paves the way for the design of a class of luminescent/thermochromic thermometers exploiting the simple experimental setup, and the performance of the prototype used to propose this approach could be improved by employing materials with larger band gap energy variations with temperature such as in the case of metal halide perovskites.

Experimental Section

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Chemical Reagents and Synthesis

(Bi0.945Y0.05Nd0.005)2O3 sample (labeled as β-Bi2O3:Y3+,Nd3+) was prepared by the solid-state reaction method. The chemical reagents Bi2O3 (99.99%), Y2O3 (99.99%), and Nd2O3 (99.99%) were used as starting materials, grounded in an alumina mortar to form a homogeneous fine powder mixture, and pressed into a pellet with a uniaxial loading of 50 MPa in a stainless steel molt. The pellet was fired at 780 °C for 6 h in an air atmosphere.

Materials Characterization

XRPD patterns were recorded at RT by means of a Philips diffractometer with a PW 1319 goniometer with Bragg–Brentano geometry equipped with Cu Kα radiation (λ = 1.54056 Å), a focusing graphite monochromator on the diffracted beam and with a proportional counter with an electronic pulse height discrimination. In order to improve the signal-to-noise ratio to perform Rietveld refinement, the data were collected with a step size of 0.05° in the preset-time mode (10 s) and at least three runs were measured.
The diffuse reflectance spectra were collected by a spectrophotometer (UV3600, Shimadzu) equipped with an integrating sphere and barium sulfate was used as standard. The in situ temperature dependence diffuse reflectance experiments were performed by means of a quadrifurcated 600 mm-core Low-OH-Silica reflectance fiber optic probe coupled with a CCD spectrometer blazed at 500 nm (QE-65Pro, Ocean Optics) and a tungsten halogen lamp (LS-1, Ocean Optics) as the light source.
Photoluminescence (PL) measurements were performed under excitation by means of a 745 nm laser (MDL-III-745-30 mW, Changchun New Industries Optoelectronics Tech. Co. Ltd.), and spectra were recorded with a Si CCD spectrometer (QE-65Pro, Ocean Optics) and an InGaAs-based spectrometer (NIRQuest512, Ocean Optics) for the NIR region, coupled to a double fiber. The PL excitation (PLE) spectrum was recorded by an InGaAs photodiode (IGA-030-H, Electro-Optical System Inc.) coupled with a short-cut (990 nm) and a longcut (1300 nm) filter, a monochromator (SpectraPro-300i, Acton Research Corporation) to tune the excitation wavelengths, and a 100 W halogen lamp (MHAA-100W, Moritex Corporation) as the excitation source. Time-resolved photoluminescence measurements were carried out at room temperature by exciting with a 590 nm pulsed LED (SpectraLED, Thorlabs) in a Horiba-Jobin Yvon Fluorolog 3 spectrofluorometer. The detection system consists of an iHR300 single grating monochromator coupled to a liquid N2-cooled R5509-73 Hamamatsu PMT operating in the IR region.
The temperature dependence of PL spectra and reflectance spectra were investigated with a temperature-controlled stage (10035 L, Linkam). The PL and PLE spectra were calibrated by means of a standard halogen lamp (DH-2000CAL, Ocean Optics) to obtain spectra on the photon flux scale and converted to photon flux per energy interval using the Jacobian transformation.

First-Principles Calculations

DFT calculations were performed using the plane wave pseudopotential technique implemented in the CASTEP module of the Materials Studio 2021 package to obtain the density of states (DOSs) of β-Bi2O3. The ionic core electrons were replaced by the on-the-fly ultrasoft pseudopotentials. The generalized gradient approximation with Perdew-Berke-Ernzerhof for solids (PBEsol) is used as the exchange–correlation energy term. Relativistic effects are taken into account at the level of the Koelling–Harmon approximation of the Dirac equation. The plane-wave basis cutoff energy and k-point grids were chosen as 630 eV and 2 × 2 × 3, respectively.

Supporting Information

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The Supporting Information is available free of charge at https://pubs.acs.org/doi/10.1021/acs.chemmater.2c01262.

  • Parameters obtained from the Rietveld refinement analysis, PL decay curve of the material, absolute sensitivity versus relative sensitivity plot and data for a series of Nd3+-activated Boltzmann thermometers, NIR-to-NIR Boltzmann thermometry in the second biological window (temperature dependence of PL spectra, Boltzmann plot, absolute sensitivity, relative sensitivity, and repeatability), thermometric parameters and performances based on chroma Cab* and the color difference ΔEab*, and colorimetric parameter values at different temperatures (PDF)

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  • Corresponding Authors
  • Authors
    • Jian Xu - Graduate School of Human and Environmental Studies, Kyoto University, Kyoto 606-8501, Japan;  International Center for Young Scientists (ICYS), National Institute for Materials Science (NIMS), Tsukuba 305-0044, Ibaraki, Japan;  Orcidhttps://orcid.org/0000-0002-1040-5090
    • Jumpei Ueda - Graduate School of Human and Environmental Studies, Kyoto University, Kyoto 606-8501, Japan;  Present Address: Materials Chemistry Frontiers, Japan Advanced Institute of Science and Technology (JAIST), 1–1, Asahidai, Nomi, Ishikawa 923-1292, Japan;  Orcidhttps://orcid.org/0000-0002-7013-9708
    • Alvise Benedetti - Department of Molecular Sciences and Nanosystems, Ca’ Foscari University of Venice, Venice-Mestre 30170, Italy
  • Author Contributions

    The manuscript was written through contributions of all authors. All authors have given approval to the final version of the manuscript.

  • Notes
    The authors declare no competing financial interest.

Acknowledgments

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The work by M.B. was financially supported by the Grant-In-Aid for JSPS Fellows (Grant no. 17F17761). This work was supported by the Grant-in-Aid for Scientific Research B (Grant no. 19H02798).

References

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This article references 64 other publications.

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    Formation and Controlled Growth of Bismuth Titanate Phases into Mesoporous Silica Nanoparticles: An Efficient Self-Sealing Nanosystem for UV Filtering in Cosmetic Formulation
    Zaccariello, Gloria; Back, Michele; Zanello, Marta; Canton, Patrizia; Cattaruzza, Elti; Riello, Pietro; Alimonti, Alessandro; Benedetti, Alvise
    ACS Applied Materials & Interfaces (2017), 9 (2), 1913-1921CODEN: AAMICK; ISSN:1944-8244. (American Chemical Society)
    The application of nanosized inorg. UV filters in cosmetic field is limited by their high photocatalytic properties that could induce the degrdn. or dangerous transformation of the org. mols. in sunscreen formulations. To overcome this problem and simultaneously enlarge the window of filter's absorption, we propose the growth of bismuth titanates BixTiyOz into mesoporous silica nanoparticles (MSN). We investigated the chem.-phys. properties by means of XRPD, TEM, UV-vis spectroscopy, N2 physisorption, XPS, and SF-ICP-MS anal., while the influence on the environment was evaluated through photocatalytic tests. The growing process of this new nanosystem is discussed underlining the key role of the Bi3+ ion that, acting as a low-m.p. agent for the silica framework, led to a self-sealing mechanism. The excellent UV shielding properties combined with a radical suppression of the photocatalytic activity make the proposed nanosystem a perfect candidate for the development of the next generation nanomaterials for sunscreen formulations.
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  19. 19
    Zaccariello, G. M.; Back, A.; Benedetti, P.; Canton, E.; Cattaruzza, H.; Onoda, A.; Glisenti, A.; Alimonti, B.; Bocca, P.; Riello, P. Bismuth titanate-based UV filters embedded mesoporous silica nanoparticles: Role of bismuth concentration in the self-sealing process. J. Colloid Interface Sci. 2019, 549, 1– 8,  DOI: 10.1016/j.jcis.2019.04.042
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    19
    Bismuth titanate-based UV filters embedded mesoporous silica nanoparticles: Role of bismuth concentration in the self-sealing process
    Zaccariello, Gloria; Back, Michele; Benedetti, Alvise; Canton, Patrizia; Cattaruzza, Elti; Onoda, Hiroaki; Glisenti, Antonella; Alimonti, Alessandro; Bocca, Beatrice; Riello, Pietro
    Journal of Colloid and Interface Science (2019), 549 (), 1-8CODEN: JCISA5; ISSN:0021-9797. (Elsevier B.V.)
    The development of new safe inorg. UV filters to effectively protect the skin from UV radiation effects is an emerging issue. Bismuth titanate-based UV filters embedded into mesoporous silica nanoparticles (MSN) represent a new class of inorg. sunscreens, with excellent UVA and UVB shielding properties. In addn., the presence of bismuth ions promotes a self-sealing process, allowing (i) the entrapment of the active phases in the deepest core of the system and (ii) the formation of an external glassy silica layer with a consequent suppression of the photocatalytic activity. In this work, aimed at studying in detail the self-sealing mechanism and accessing the role of bismuth ions in the formation of the system, a series of samples impregnated with a different amt. of bismuth were investigated. The self-sealing process already occurs at the lowest content of bismuth and the mechanism is demonstrated to be triggered by the ability of Bi to work as a low-m.p. agent for silica. Finally, a sunscreen formulation contg. the new UV filter was prepd. and the Sun Protection Factor (SPF), the pH and the viscosity were measured, demonstrating the potential of the proposed material for large-scale applications.
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  20. 20
    Chen, A.; Zhou, H.; Bi, Z.; Zhu, Y.; Luo, Z.; Bayraktaroglu, A.; Phillips, J.; Choi, E.-M.; MacManus-Discoll, J. L.; Pennycook, S. J. A new class of room-temperature multiferroic thin films with bismuth-based supercell structure. Adv. Mater. 2013, 25, 1028– 1032,  DOI: 10.1002/adma.201203051
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    20
    A New Class of Room-Temperature Multiferroic Thin Films with Bismuth-Based Supercell Structure
    Chen, Aiping; Zhou, Honghui; Bi, Zhenxing; Zhu, Yuanyuan; Luo, Zhiping; Bayraktaroglu, Adrian; Phillips, Jamie; Choi, Eun-Mi; MacManus-Driscoll, Judith L.; Pennycook, Stephen J.; Narayan, Jagdish; Jia, Quanxi; Zhang, Xinghang; Wang, Haiyan
    Advanced Materials (Weinheim, Germany) (2013), 25 (7), 1028-1032CODEN: ADVMEW; ISSN:0935-9648. (Wiley-VCH Verlag GmbH & Co. KGaA)
    In this study, the authors present a new class of room-temp. multiferroics based on two partially miscible phases of BiFeO3 and BiMnO3, with a new structure enabled by epitaxial strain. The new BFMO single phase shows a bismuth supercell (SC) structure on LaAlO3 (LAO) substrates and exhibits both ferrimagnetic and ferroelec. responses at room temp. More interestingly, this new phase can be formed on other substrates with a properly selected buffer layer. The XRD patterns and structure are described.
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  21. 21
    Huang, H.; Wang, Z.; Huang, B.; Wang, P.; Zhang, X.; Qin, X.; Dai, Y.; Zhou, G.; Whangbo, M.-H. Intense single red emission induced by near-infrared irradiation using a narrow bandgap oxide BiVO4 as the host for Yb3+ and Tm3+ ions. Adv. Opt. Mater. 2018, 6, 1701331,  DOI: 10.1002/adom.201701331
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    Okabe, K.; Inada, N.; Gota, C.; Harada, Y.; Funatsu, T.; Uchiyama, S. Intracellular temperature mapping with a fluorescent polymeric thermometer and fluorescence lifetime imaging microscopy. Nat. Commun. 2012, 3, 705,  DOI: 10.1038/ncomms1714
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    Intracellular temperature mapping with a fluorescent polymeric thermometer and fluorescence lifetime imaging microscopy
    Okabe Kohki; Inada Noriko; Gota Chie; Harada Yoshie; Funatsu Takashi; Uchiyama Seiichi
    Nature communications (2012), 3 (), 705 ISSN:.
    Cellular functions are fundamentally regulated by intracellular temperature, which influences biochemical reactions inside a cell. Despite the important contributions to biological and medical applications that it would offer, intracellular temperature mapping has not been achieved. Here we demonstrate the first intracellular temperature mapping based on a fluorescent polymeric thermometer and fluorescence lifetime imaging microscopy. The spatial and temperature resolutions of our thermometry were at the diffraction limited level (200 nm) and 0.18-0.58 °C. The intracellular temperature distribution we observed indicated that the nucleus and centrosome of a COS7 cell, both showed a significantly higher temperature than the cytoplasm and that the temperature gap between the nucleus and the cytoplasm differed depending on the cell cycle. The heat production from mitochondria was also observed as a proximal local temperature increase. These results showed that our new intracellular thermometry could determine an intrinsic relationship between the temperature and organelle function.
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    Piñol, R.; Zeler, J.; Brites, C. D. S.; Gu, Y.; Téllez, P.; Carneiro Neto, A. N.; da Silva, T. E.; Moreno-Loshuertos, R.; Fernandez-Silva, P.; Gallego, A. I.; Martinez-Lostao, L.; Martínez, A.; Carlos, L. D.; Millán, A. Real-time intracellular temperature imaging using lanthanide-bearing polymeric micelles. Nano Lett. 2020, 20, 6466– 6472,  DOI: 10.1021/acs.nanolett.0c02163
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    Real-Time Intracellular Temperature Imaging Using Lanthanide-Bearing Polymeric Micelles
    Pinol, Rafael; Zeler, Justyna; Brites, Carlos D. S.; Gu, Yuanyu; Tellez, Pedro; Carneiro Neto, Albano N.; da Silva, Thiago E.; Moreno-Loshuertos, Raquel; Fernandez-Silva, Patricio; Gallego, Ana Isabel; Martinez-Lostao, Luis; Martinez, Abelardo; Carlos, Luis D.; Millan, Angel
    Nano Letters (2020), 20 (9), 6466-6472CODEN: NALEFD; ISSN:1530-6984. (American Chemical Society)
    Measurement of thermogenesis in individual cells is a remarkable challenge due to the complexity of the biochem. environment (such as pH and ionic strength) and to the rapid and yet not well-understood heat transfer mechanisms throughout the cell. Here, the authors present a unique system for intracellular temp. mapping in a fluorescence microscope (uncertainty of 0.2 K) using rationally designed luminescent Ln3+-bearing polymeric micellar probes (Ln = Sm, Eu) incubated in breast cancer MDA-MB468 cells. Two-dimensional (2D) thermal images recorded increasing the temp. of the cells culture medium between 296 and 304 K shows inhomogeneous intracellular temp. progressions up to ~ 20 degrees and subcellular gradients of ~ 5 degrees between the nucleolus and the rest of the cell, illustrating the thermogenic activity of the different organelles and highlighting the potential of this tool to study intracellular processes.
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    Bednarkiewicz, A.; Drabik, J.; Trejgis, K.; Jaque, D.; Ximendes, E.; Marciniak, L. Luminescence based temperature bio-imaging: Status, challenges, and perspectives. Appl. Phys. Rev. 2021, 8, 011317,  DOI: 10.1063/5.0030295
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    Luminescence based temperature bio-imaging: Status, challenges, and perspectives
    Bednarkiewicz, A.; Drabik, J.; Trejgis, K.; Jaque, D.; Ximendes, E.; Marciniak, L.
    Applied Physics Reviews (2021), 8 (1), 011317CODEN: APRPG5; ISSN:1931-9401. (American Institute of Physics)
    A review. The only way to get thermal images of living organisms without perturbing them is to use luminescent probes with temp.-dependent spectral properties. The acquisition of such thermal images becomes essential to distinguish various states of cells, to monitor thermogenesis, to study cellular activity, and to control hyperthermia therapy. Current efforts are focused on the development and optimization of luminescent reporters such as small mols., proteins, quantum dots, and lanthanide-doped nanoparticles. However, much less attention is devoted to the methods and technologies that are required to image temp. distribution at both in vitro or in vivo levels. Indeed, rare examples can be found in the scientific literature showing technologies and materials capable of providing reliable 2D thermal images of living organisms. In this review article, examples of 2D luminescence thermometry are presented alongside new possibilities and directions that should be followed to achieve the required level of simplicity and reliability that ensure their future implementation at the clin. level. This review will inspire specialists in chem., physics, biol., medicine, and engineering to collaborate with materials scientists to jointly develop novel more accurate temp. probes and enable mapping of temp. with simplified tech. means. (c) 2021 American Institute of Physics.
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  25. 25
    van Swieten, T. P.; van Omme, T.; van den Heuvel, D. J.; Vonk, S. J. W.; Spruit, R. G.; Meirer, F.; Garza, H. H. P.; Weckhuysen, B. M.; Meijerink, A.; Rabouw, F. T.; Geitenbeek, R. G. Mapping elevated temperatures with a micrometer resolution using the luminescence of chemically stable upconversion nanoparticles. ACS Appl. Nano Mater. 2021, 4, 4208– 4215,  DOI: 10.1021/acsanm.1c00657
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    25
    Mapping Elevated Temperatures with a Micrometer Resolution Using the Luminescence of Chemically Stable Upconversion Nanoparticles
    van Swieten, Thomas P.; van Omme, Tijn; van den Heuvel, Dave J.; Vonk, Sander J. W.; Spruit, Ronald G.; Meirer, Florian; Garza, H. Hugo Perez; Weckhuysen, Bert M.; Meijerink, Andries; Rabouw, Freddy T.; Geitenbeek, Robin G.
    ACS Applied Nano Materials (2021), 4 (4), 4208-4215CODEN: AANMF6; ISSN:2574-0970. (American Chemical Society)
    Nanothermometry with high spatial resolns. at elevated temps. is realized using chem. stable upconversion nanoparticles and confocal microscopy. This method is tested on a microelectromech. heater, and the temp. homogeneity was studied. The expts. reveal distortions in the luminescence spectra that are intrinsic to high-resoln. measurements of samples with nanoscale photonic inhomogeneities. The spectra are affected by the high-power excitation as well as by scattering and reflection of the emitted light. The latter effect has an increasing impact at elevated temps. A procedure to correct these distortions is presented. The range of high-resoln. nanothermometry beyond 500 K was extended with a precision of 1-4 K. This work will improve the accuracy of nanothermometry not only in micro- and nanoelectronics but also in other fields with photonically inhomogeneous substrates.
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    Back, M.; Ueda, J.; Xu, J.; Murata, D.; Brik, M. G.; Tanabe, S. Ratiometric luminescent thermometers with a customized phase-transition-driven fingerprint in perovskite oxides. ACS Appl. Mater. Interfaces 2019, 11, 38937– 38945,  DOI: 10.1021/acsami.9b13010
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    Ratiometric Luminescent Thermometers with a Customized Phase-Transition-Driven Fingerprint in Perovskite Oxides
    Back, Michele; Ueda, Jumpei; Xu, Jian; Murata, Daisuke; Brik, Mikhail G.; Tanabe, Setsuhisa
    ACS Applied Materials & Interfaces (2019), 11 (42), 38937-38945CODEN: AAMICK; ISSN:1944-8244. (American Chemical Society)
    The development of non-contact thermometers with self-control to specific temps. to be used as control markers with an addnl. degree of reliability is a challenge in the field of thermal sensors. Herein, a strategy exploiting the wide tunability of an intrinsic feature of oxide perovskites such as the phase transition temp. to design a new class of ratiometric luminescent thermometers is introduced. The structural and optical response to the thermal stimuli of LaGaO3:Nd3+ system is used as a prototype to show the unprecedented opportunity to combine the processes of two different regimes in the same compd. leading to a reliable optical thermal sensor with an intrinsic tell-tale sign at specific temps. High relative sensitivity, low temp. uncertainty and good reproducibility, together with the need of a single calibration curve irresp. to the phase transition temp. and the doping effects, attest the goodness of the thermometric performances. This work demonstrates the control of the phase transition (orthorhombic ↔ rhombohedral) temp. Tc of lanthanum gallate in the 400-700 K range by carefully doping the perovskite structure, as proof of concept for the design of customized thermometers characterized by a spectral shape change acting as a self-fingerprint for the Tc.
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  27. 27
    Brites, C. D. S.; Zhuang, B.; Debasu, M. L.; Ding, D.; Qin, X.; Maturi, F. E.; Lim, W. W. Y.; Soh, D. W.; Rocha, J.; Yi, Z.; Liu, X.; Carlos, L. D. Decoding a percolation phase transition of water at ∼330 K with a nanoparticle ruler. J. Phys. Chem. Lett. 2020, 11, 6704– 6711,  DOI: 10.1021/acs.jpclett.0c02147
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    27
    Decoding a Percolation Phase Transition of Water at ~ 330 K with a Nanoparticle Ruler
    Brites, Carlos D. S.; Zhuang, Bilin; Debasu, Mengistie L.; Ding, Ding; Qin, Xian; Maturi, Fernando E.; Lim, Winnie W. Y.; Soh, De Wen; Rocha, J.; Yi, Zhigao; Liu, Xiaogang; Carlos, Luis D.
    Journal of Physical Chemistry Letters (2020), 11 (16), 6704-6711CODEN: JPCLCD; ISSN:1948-7185. (American Chemical Society)
    Liq. water, despite its simple mol. structure, remains one of the most fascinating and complex substances. Most notably, many questions continue to exist regarding the phase transitions and anomalous properties of water, which are subtle to observe exptl. Here, we report a sharp transition in water at 330 K unveiled through exptl. measurements of the instantaneous Brownian velocity of NaYF4:Yb/Er upconversion nanoparticles in water. Our exptl. investigations, corroborated by mol. dynamics simulations, elucidate a geometrical phase transition where a low-d. liq. (LDL) clusters become percolated below 330 K. Around this crit. temp., we find the sizes of the LDL clusters to be similar to those of the nanoparticles, confirming the role of the upconversion nanoparticle as a powerful ruler for measuring the extensiveness of the LDL hydrogen-bond network and nanometer-scale spatial changes (20-100 nm) in liqs. Addnl., a new order parameter that unequivocally classifies water mols. into two local geometric states is introduced, providing a new tool for understanding and modeling water's many anomalous properties and phase transitions.
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    Geitenbeek, R. G.; Nieuwelink, A.-E.; Jacobs, T. S.; Salzmann, B. B. V.; Goetze, J.; Meijerink, A.; Weckhuysen, B. M. In situ luminescence thermometry to locally measure temperature gradients during catalytic reactions. ACS Catal. 2018, 8, 2397– 2401,  DOI: 10.1021/acscatal.7b04154
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    In Situ Luminescence Thermometry To Locally Measure Temperature Gradients during Catalytic Reactions
    Geitenbeek, Robin G.; Nieuwelink, Anne-Eva; Jacobs, Thimo S.; Salzmann, Bastiaan B. V.; Goetze, Joris; Meijerink, Andries; Weckhuysen, Bert M.
    ACS Catalysis (2018), 8 (3), 2397-2401CODEN: ACCACS; ISSN:2155-5435. (American Chemical Society)
    Bandshape luminescence thermometry during in situ temp. measurements has been reported by prepg. three catalytically relevant systems, which show temp.-dependent luminescence. One of these systems was further investigated as a showcase for application. Microcryst. NaYF4 doped with Er3+ and Yb3+ was mixed with a com. zeolite H-ZSM-5 to investigate the Methanol-to-Hydrocarbons (MTH) reaction, while monitoring the reaction products with online gas chromatog. Due to the exothermic nature of the MTH reaction, a front of increased temp. migrating down the fixed reactor bed was visualized, showing the potential for various applications of luminescence thermometry for in situ measurements in catalytic systems.
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  29. 29
    Ravenhorst, I. K.; Geitenbeek, R. G.; Eerden, M. J.; Tijn van Omme, J. T.; Peréz Garza, H. H. P.; Meirer, F.; Meijerink, A.; Weckhuysen, B. M. In situ local temperature mapping in microscopy nano-reactors with luminescence thermometry. ChemCatChem 2019, 11, 5505– 5512,  DOI: 10.1002/cctc.201900985
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    Hartman, T.; Geitenbeek, R. G.; Whiting, G. T.; Weckhuysen, B. M. Operando monitoring of temperature and active species at the single catalyst particle level. Nat. Catal. 2019, 2, 986– 996,  DOI: 10.1038/s41929-019-0352-1
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    Operando monitoring of temperature and active species at the single catalyst particle level
    Hartman, Thomas; Geitenbeek, Robin G.; Whiting, Gareth T.; Weckhuysen, Bert M.
    Nature Catalysis (2019), 2 (11), 986-996CODEN: NCAACP; ISSN:2520-1158. (Nature Research)
    The development of improved catalysts requires insights into the relationship between catalytic activity and catalyst structure, including the underlying reaction mechanism. Here, we demonstrate a unique set of catalyst extrudate sensors that allow for the simultaneous detection of local temp. by luminescence thermometry, and of surface species by shell-isolated nanoparticle-enhanced Raman spectroscopy. This sensing approach was applied to the characterization of direct conversion of syngas into hydrocarbons and C2+ oxygenates over supported Rh and RhFe catalysts. Luminescence thermometry demonstrated a mismatch between the set temp. and the local catalyst temp., with variations up to 40 °C. Furthermore, by investigating the surface species on varying extrudate and catalyst compns., we identified tilted carbonyl species on the Rh/SiO2 interface that are probable precursors for the hydrogen-assisted CO dissocn. The implementation of extrudate catalyst sensors as a characterization tool provides a unique approach towards the further understanding of the relevant parameters in catalysis.
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    Back, M.; Ueda, J.; Nambu, H.; Fujita, M.; Yamamoto, A.; Yoshida, H.; Tanaka, H.; Brik, M. G.; Tanabe, S. Boltzmann thermometry in Cr3+-doped Ga2O3 polymorphs: The structure matters. Adv. Opt. Mater. 2021, 9, 2100033,  DOI: 10.1002/adom.202100033
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    31
    Boltzmann Thermometry in Cr3+-Doped Ga2O3 Polymorphs: The Structure Matters
    Back, Michele; Ueda, Jumpei; Nambu, Hiroshi; Fujita, Masami; Yamamoto, Akira; Yoshida, Hisao; Tanaka, Hiromitsu; Brik, Mikhail G.; Tanabe, Setsuhisa
    Advanced Optical Materials (2021), 9 (9), 2100033CODEN: AOMDAX; ISSN:2195-1071. (Wiley-VCH Verlag GmbH & Co. KGaA)
    The performance of luminescent Cr3+-doped thermometers is strongly influenced by the locally surrounding ligand field. A universal relationship between the thermometric performance and structural/chem. parameters is highly desirable to drive the development of effective Cr3+-based thermal sensors avoiding trial-and-error procedures. In this view, as prototypes, the electronic structure and the thermometric performance of Cr3+-doped α-Ga2O3 and β-Ga2O3 polymorphs are compared. Combining a detailed theor. and spectroscopic investigation, the electronic configuration and the crystal field (CF) acting on the Cr3+ in α-Ga2O3 are described for the first time and compared with β-Ga2O3:Cr3+ polymorph to discuss the thermometric behavior. A linear relationship between the 4T2-2E energy gap (directly linked to the relative sensitivity) and the CF strength Dq is demonstrated for a wide variety of materials. This trend can be considered as a first step to set guiding principles to design effective Cr3+-based Boltzmann thermometers. In addn., as a proof of concept, particles of β-Ga2O3:Cr3+ thermometer are used to locally measure in operando thermal variations of Pt catalysts on β-Ga2O3:Cr3+ support during a catalytic reaction of C2H4 hydrogenation in a contactless and reliable mode, demonstrating their real potentials.
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    Marciniak, L.; Bednarkiewicz, A.; Stefanski, M.; Tomala, R.; Hreniak, D.; Strek, W. Near infrared absorbing near infrared emitting highly-sensitive luminescent nanothermometer based on Nd3+ to Yb3+ energy transfer. Phys. Chem. Chem. Phys. 2015, 17, 24315– 24321,  DOI: 10.1039/c5cp03861h
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    32
    Near infrared absorbing near infrared emitting highly-sensitive luminescent nanothermometer based on Nd3+ to Yb3+ energy transfer
    Marciniak, L.; Bednarkiewicz, A.; Stefanski, M.; Tomala, R.; Hreniak, D.; Strek, W.
    Physical Chemistry Chemical Physics (2015), 17 (37), 24315-24321CODEN: PPCPFQ; ISSN:1463-9076. (Royal Society of Chemistry)
    A new type of near IR absorbing near IR emitting (NANE) luminescent nanothermometer is presented, with a phys. background that relies on efficient Nd3+ to Yb3+ energy transfer under 808 nm photoexcitation. The emission spectra of LiLa0.9-xNd0.1YbxP4O12 (x = 0.05, 0.1, 0.2, 0.3, 0.5) nanocrystals were measured in a wide 100-700 °C temp. range. The ratio between the Nd3+ (4F3/2 → 4I9/2) and Yb3+ (2F5/2 → 2F7/2) luminescence bands, and the thermometer sensitivity are strongly dependent on the Yb3+ concn. These phenomenol. relations were discussed in terms of the competition between three phenomena, (a) Nd3+ → Yb3+ phonon assisted energy transfer, (b) Yb3+ → Nd3+ back energy transfer and (c) energy diffusion between Yb3+ ions. The highest sensitivity of the temp. measurement was found for x = 0.5 (LiLa0.4Nd0.1Yb0.5P4O12), which was equal to 4 × 10-3 K-1 at 330 K. In stark contrast to conventional approaches, the proposed phosphate host matrix allows for a high level of doping, and thus, owing to the negligible concn. quenching, the presented luminophores exhibit a high absorption cross section and bright emission. Also, such optical remote thermometers, whose excitation and emission wavelengths are weakly scattered or absorbed and fall into the optical transmission window of the skin, may therefore become a practical soln. for biomedical applications, such as remote control of thermotherapy.
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    Marciniak, L.; Bednarkiewicz, A.; Drabik, J.; Trejgis, K.; Strek, W. Optimization of highly sensitive YAG:Cr3+,Nd3+ nanocrystal-based luminescent thermometer operating in an optical window of biological tissues. Phys. Chem. Chem. Phys. 2017, 19, 7343– 7351,  DOI: 10.1039/c6cp07213e
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    Optimization of highly sensitive YAG:Cr3+,Nd3+ nanocrystal-based luminescent thermometer operating in an optical window of biological tissues
    Marciniak, L.; Bednarkiewicz, A.; Drabik, J.; Trejgis, K.; Strek, W.
    Physical Chemistry Chemical Physics (2017), 19 (10), 7343-7351CODEN: PPCPFQ; ISSN:1463-9076. (Royal Society of Chemistry)
    Luminescent and temp. sensitive properties of YAG:Cr3+,Nd3+ nanocrystals were analyzed as a function of temp., nanoparticle size, and excitation wavelength. Due to numerous temp.-dependent phenomena (e.g. Boltzmann population, thermal quenching, and inter-ion energy transfer) occurring in this phosphor, four different thermometer definitions were evaluated with the target to achieve a high sensitivity and broad temp. sensitivity range. Using a Cr3+ to Nd3+ emission intensity ratio, the highest 3.48% K-1 sensitivity was obtained in the physiol. temp. range. However, high sensitivity was compromised by a narrow sensitivity range or vice versa. The knowledge of the excitation and temp. susceptibility mechanisms enabled wise selection of the spectral features found in luminescence spectra for a temp. readout, which enabled the preservation of relatively high temp. sensitivity (>1.2% K-1 max) and extended the temp. sensitivity range from 100 K to 850 K. The size of the nanophosphors had negligible impact on the performance of the studied materials.
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    Gao, Y.; Huang, F.; Lin, H.; Zhou, J.; Xu, J.; Wang, Y. A novel optical thermometry strategy based on diverse thermal response from two intervalence charge transfer states. Adv. Funct. Mater. 2016, 26, 3139– 3145,  DOI: 10.1002/adfm.201505332
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    A Novel Optical Thermometry Strategy Based on Diverse Thermal Response from Two Intervalence Charge Transfer States
    Gao, Yan; Huang, Feng; Lin, Hang; Zhou, Jiangcong; Xu, Ju; Wang, Yuansheng
    Advanced Functional Materials (2016), 26 (18), 3139-3145CODEN: AFMDC6; ISSN:1616-301X. (Wiley-VCH Verlag GmbH & Co. KGaA)
    In this work, a novel thermometry strategy based on the diversity in thermal quenching behavior of two intervalence charge transfer (IVCT) states in oxide crystals is proposed, which provides a promising route to design self-referencing optical temp. sensing material with superior temp. sensitivity and signal discriminability. Following this strategy, uniform Tb3+/Pr3+:NaGd(MoO4)2 micro-octahedrons are directionally synthesized. Originated from the diverse thermal responses between Tb3+-Mo6+ and Pr3+-Mo6+ IVCT states, fluorescence intensity ratio of Pr3+ to Tb3+ in this material displays excellent temp. sensing property in a temp. range from 303 to 483 K. The max. abs. and relative sensitivity reaches as high as 0.097 K-1 and 2.05% K-1, resp., being much higher than those of the previously reported optical thermometric materials. Excellent temp. sensing features are also demonstrated in the other Tb3+/Pr3+ codoped oxide crystals having d0 electron configured transition metal ions (Ti4+, V5+, Mo6+, or W6+), such as scheelite NaLu(MoO4)2 and NaLu(WO4)2, and monazite LaVO4 and perovskite La2Ti3O9, evidencing the universal validity of the proposed strategy. This work exploits an effective pathway for developing new optical temp. sensing materials with high performance.
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  35. 35
    Souza, A. S.; Nunes, L. A. O.; Silva, I. G. N.; Oliveira, F. A. M.; da Luz, L. L.; Brito, H. F.; Felinto, M. C. F. C.; Ferreira, R. A. S.; Júnior, S. A.; Carlos, L. D.; Malta, O. L. Highly-sensitive Eu3+ ratiometric thermometers based on excited state absorption with predictable calibration. Nanoscale 2016, 8, 5327– 5333,  DOI: 10.1039/c6nr00158k
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    Highly-sensitive Eu3+ ratiometric thermometers based on excited state absorption with predictable calibration
    Souza, Adelmo S.; Nunes, Luiz A. O.; Silva, Ivan G. N.; Oliveira, Fernando A. M.; da Luz, Leonis L.; Brito, Hermi F.; Felinto, Maria C. F. C.; Ferreira, Rute A. S.; Junior, Severino A.; Carlos, Luis D.; Malta, Oscar L.
    Nanoscale (2016), 8 (9), 5327-5333CODEN: NANOHL; ISSN:2040-3372. (Royal Society of Chemistry)
    Temp. measurements ranging from a few degrees to a few hundreds of Kelvin are of great interest in the fields of nanomedicine and nanotechnol. Here, we report a new ratiometric luminescent thermometer using thermally excited state absorption of the Eu3+ ion. The thermometer is based on the simple Eu3+ energy level structure and can operate between 180 and 323 K with a relative sensitivity ranging from 0.7 to 1.7% K-1. The thermometric parameter is defined as the ratio between the emission intensities of the 5D0 → 7F4 transition when the 5D0 emitting level is excited through the 7F2 (physiol. range) or 7F1 (down to 180 K) level. Nano and microcrystals of Y2O3:Eu3+ were chosen as a proof of concept of the operational principles in which both excitation and detection are within the first biol. transparent window. A novel and of paramount importance aspect is that the calibration factor can be calcd. from the Eu3+ emission spectrum avoiding the need for new calibration procedures whenever the thermometer operates in different media.
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  36. 36
    Trejgis, K.; Bednarkiewicz, A.; Marciniak, L. Engineering excited state absorption based nanothermometry for temperature sensing and imaging. Nanoscale 2020, 12, 4667– 4675,  DOI: 10.1039/c9nr09740f
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    Engineering excited state absorption based nanothermometry for temperature sensing and imaging
    Trejgis, K.; Bednarkiewicz, A.; Marciniak, L.
    Nanoscale (2020), 12 (7), 4667-4675CODEN: NANOHL; ISSN:2040-3372. (Royal Society of Chemistry)
    Current luminescence nanothermometry exploits either temp. dependent quenching, temp. dependent energy transfer or thermal equil. between two metastable emitting levels, which are quantified to convert spectral features into abs. temp. Although widely used and feasible, these methods are not always reliable enough in terms of flexibility, optimum temp. operating range and often require relatively complicated and expensive detection instrumentation, which may hinder wider adoption of luminescence based nanothermometry in technol. and biomedical sciences. Therefore, not only more sensitive, brighter and robust phosphors are sought, but also novel temp. sensing schemes, which may potentially simplify remote quantification and imaging of temp. In this work, we demonstrate the concept of contactless temp. readout and 2D temp. mapping by using excited state absorption (ESA) process instead of conventional approach based on ground state absorption (GSA) combined with multi-color emission. The anal. of the excitation spectra of LiLaP4O12:Eu3+ nanocryst. powders in a wide temp. range confirmed that the probability of populating higher levels of the ground 7FJ multiplet increases at increased temps. The Single Band Ratiometric Luminescent Thermometry (SBR-LT) opens new possibilities and offers luminescent thermometry at single emission band (5D0 → 7F1) under different excitation lines (7F2,3,4 → 5D0). In consequence, tech. simple, temp. range adjustable, fast and affordable optical temp. imaging can be performed with high sensitivity reaching over 2.17% per °C in an unprecedentedly wide temp. range from -150 to 400°C.
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    McLaurin, E. J.; Bradshaw, L. R.; Gamelin, D. R. Dual-emitting nanoscale temperature sensors. Chem. Mater. 2013, 25, 1283– 1292,  DOI: 10.1021/cm304034s
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    Dual-Emitting Nanoscale Temperature Sensors
    McLaurin, Emily J.; Bradshaw, Liam R.; Gamelin, Daniel R.
    Chemistry of Materials (2013), 25 (8), 1283-1292CODEN: CMATEX; ISSN:0897-4756. (American Chemical Society)
    A review. Sol. luminescent temp. probes are promising candidates for optical thermometry and thermog. applications requiring precise, passive, and spatially resolved temp. data. Dual-emitting temp. sensors overcome many of the obstacles encountered with abs. intensity-based luminescence sensors, including optical occlusion, concn. variation, or nonspecificity, by providing internally referenced (ratiometric) signals. The key mechanisms underpinning the dual emission of various nanostructures from recent literature are provided and their relation to optical thermometry discussed.
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    Back, M.; Trave, E.; Ueda, J.; Tanabe, S. Ratiometric optical thermometer based on dual near-infrared emission in Cr3+-doped bismuth-based gallate host. Chem. Mater. 2016, 28, 8347– 8356,  DOI: 10.1021/acs.chemmater.6b03625
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    Ratiometric Optical Thermometer Based on Dual Near-Infrared Emission in Cr3+-Doped Bismuth-Based Gallate Host
    Back, Michele; Trave, Enrico; Ueda, Jumpei; Tanabe, Setsuhisa
    Chemistry of Materials (2016), 28 (22), 8347-8356CODEN: CMATEX; ISSN:0897-4756. (American Chemical Society)
    Detailed spectroscopic anal. of the electronic configuration of Cr3+ in Bi2Ga4O9 is reported. The material exhibits unique luminescent properties arising from the crystal field experienced by Cr3+, with simultaneous strong sharp and broadband near-IR emissions from the 2E and 4T2 excited states, in a wide range of temp. The system displays dual near-IR emission characterized by a remarkable thermal sensitivity over the whole explored range of temps., reaching a value of 0.7%·K-1 in the physiol. range. Also, the possibility to absorb and emit in the 1st biol. window, allows 1 to consider the system as a new promising candidate for ratiometric fluorescent thermal sensing in biotechnol. applications.
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  39. 39
    Casagrande, E.; Back, M.; Cristofori, D.; Ueda, J.; Tanabe, S.; Palazzolo, S.; Rizzolio, F.; Canzonieri, V.; Trave, E.; Riello, P. Upconversion-mediated Boltzmann thermometry in double-layered Bi2SiO5:Yb3+,Tm3+@SiO2 hollow nanoparticles sensors. J. Mater. Chem. C 2020, 8, 7828– 7836,  DOI: 10.1039/d0tc01457e
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    Upconversion-mediated Boltzmann thermometry in double-layered Bi2SiO5:Yb3+,Tm3+@SiO2 hollow nanoparticles
    Casagrande, Elisa; Back, Michele; Cristofori, Davide; Ueda, Jumpei; Tanabe, Setsuhisa; Palazzolo, Stefano; Rizzolio, Flavio; Canzonieri, Vincenzo; Trave, Enrico; Riello, Pietro
    Journal of Materials Chemistry C: Materials for Optical and Electronic Devices (2020), 8 (23), 7828-7836CODEN: JMCCCX; ISSN:2050-7534. (Royal Society of Chemistry)
    Ratiometric optical thermometry is one of the most promising techniques for contactless temp. sensing. However, despite the efforts devoted in the last decades, the development of nanothermometers characterized by high reliability along with suitable sensitivity (Sr > 1% K-1) and thermal resoln. (δT < 0.5 K) in the physiol. temp. range is still a crit. challenge in the biol. field. Here, we propose uniform Yb,Tm co-doped cryst. Bi2SiO5@SiO2 hollow upconverting nanoparticles as red-NIR emitting nanophosphors for ratiometric optical thermometry. The synthetic procedure leads to double-layered Bi2SiO5:Yb,Tm@SiO2 hollow nanoparticles. The thermometric performances are investigated in a wide temp. range (80-800 K) demonstrating the reliability of the thermometer based on the emission ratio between the 1G4 → 3F4 (~ 650 nm) and 3F2,3 → 3H6 (~ 700 nm) transitions. Despite the impossibility to be in thermal equil. due to the large energy gap between 1G4 and 3F2,3 excited states, their relative populations are demonstrated to follow the Boltzmann distribution, reflecting, through the upconversion processes, the thermalization between the 3F2,3 and 3H4 excited states. Consequently, the system features high thermal sensitivity (Sr = 1.95% K-1 at 300 K) and excellent thermal resoln. (0.28 K at 300 K) for a highly reliable system following the Boltzmann-distribution. In addn., the superior performances of the investigated system in comparison with other NIR-to-NIR thermometers such as Nd3+-based ones and the biocompatibility of the NPs prove its potential in the physiol. temp. range.
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    Suta, M.; Meijerink, A. A theoretical framework for ratiometric single ion luminescent thermometers─Thermodynamic and kinetic guidelines for optimized performance. Adv. Theory Simul. 2020, 3, 2000176,  DOI: 10.1002/adts.202000176
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    A Theoretical Framework for Ratiometric Single Ion Luminescent Thermometers-Thermodynamic and Kinetic Guidelines for Optimized Performance
    Suta, Markus; Meijerink, Andries
    Advanced Theory and Simulations (2020), 3 (12), 2000176CODEN: ATSDCW; ISSN:2513-0390. (Wiley-VCH Verlag GmbH & Co. KGaA)
    Luminescence (nano)thermometry is an increasingly important field for remote temp. sensing with high spatial resoln. Most typically, ratiometric sensing of the luminescence emission intensities of two thermally coupled emissive states based on a Boltzmann equil. is used to detect the local temp. Dependent on the temp. range and preferred spectral window, various choices for potential candidates appear possible. Despite extensive exptl. research in the field, a universal theory covering the basics of luminescence thermometry is virtually nonexistent. In this manuscript, a general theor. framework of single ion luminescent thermometers is presented that offers simple, user-friendly guidelines for both the choice of an appropriate emitter and resp. embedding host material for optimum temp. sensing. The results show that the optimum performance (thermal response and sensitivity) around T0 is realized for an energy gap ΔE21 between thermally coupled levels between 2kBT0 and 3.41kBT0. Anal. of the temp.-dependent excited state kinetics shows that host lattices in which ΔE21 can be bridged by one or two phonons are preferred over hosts in which higher order phonon processes are required. Such a framework is relevant for both a fundamental understanding of luminescent thermometers but also the targeted design of novel and superior luminescent (nano)thermometers.
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    Yu, D.; Li, H.; Zhang, D.; Zhang, Q.; Meijerink, A.; Suta, M. One ion to catch them all: Targeted high-precision Boltzmann thermometry over a wide temperature range with Gd3+. Light Sci. Appl. 2021, 10, 236,  DOI: 10.1038/s41377-021-00677-5
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    One ion to catch them all: Targeted high-precision Boltzmann thermometry over a wide temperature range with Gd3+
    Yu, Dechao; Li, Huaiyong; Zhang, Dawei; Zhang, Qinyuan; Meijerink, Andries; Suta, Markus
    Light: Science & Applications (2021), 10 (1), 236CODEN: LSAIAZ; ISSN:2047-7538. (Nature Research)
    Abstr.: Ratiometric luminescence thermometry with trivalent lanthanide ions and their 4fn energy levels is an emerging technique for non-invasive remote temp. sensing with high spatial and temporal resoln. Conventional ratiometric luminescence thermometry often relies on thermal coupling between two closely lying energy levels governed by Boltzmanns law. Despite its simplicity, Boltzmann thermometry with two excited levels allows precise temp. sensing, but only within a limited temp. range. While low temps. slow down the nonradiative transitions required to generate a measurable population in the higher excitation level, temps. that are too high favor equalized populations of the two excited levels, at the expense of low relative thermal sensitivity. In this work, we extend the concept of Boltzmann thermometry to more than two excited levels and provide quant. guidelines that link the choice of energy gaps between multiple excited states to the performance in different temp. windows. By this approach, it is possible to retain the high relative sensitivity and precision of the temp. measurement over a wide temp. range within the same system. We demonstrate this concept using YAl3(BO3)4 (YAB):Pr3+, Gd3+ with an excited 6PJ crystal field and spin-orbit split levels of Gd3+ in the UV range to avoid a thermal black body background even at the highest temps. This phosphor is easily excitable with inexpensive and powerful blue LEDs at 450 nm. Zero-background luminescence thermometry is realized by using blue-to-UV energy transfer upconversion with the Pr3+-Gd3+ couple upon excitation in the visible range. This method allows us to cover a temp. window between 30 and 800 K.
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    Sammes, N. M.; Tompsett, G. A.; Näfe, H.; Aldinger, F. Bismuth based oxide electrolytes - Sructure and ionic conductivity. J. Eur. Ceram. Soc. 1999, 19, 1801– 1826,  DOI: 10.1016/s0955-2219(99)00009-6
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    Bismuth based oxide electrolytes-structure and ionic conductivity
    Sammes, N. M.; Tompsett, G. A.; Nafe, H.; Aldinger, F.
    Journal of the European Ceramic Society (1999), 19 (10), 1801-1826CODEN: JECSER; ISSN:0955-2219. (Elsevier Science Ltd.)
    Bismuth oxide systems exhibit high oxide ion cond. and have been proposed as good electrolyte materials for applications such as solid oxide fuel cells and oxygen sensors. However, due to their instability under conditions of low oxygen partial pressures there has been difficulty in developing these materials as alternative electrolyte materials compared to the state-of-the-art cubic stabilized zirconia electrolyte. Bismuth oxide and doped bismuth oxide systems exhibit a complex array of structures and properties depending upon the dopant concn., temp. and atm. In this paper we comprehensively review the structures, thermal expansion, phase transitions, elec. cond. and stability of bismuth oxide and doped bismuth oxide systems.
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    Drache, M.; Roussel, P.; Wignacourt, J.-P. Structures of oxide mobility in Bi-Ln-O materials: Heritage of Bi2O3. Chem. Rev. 2007, 107, 80– 96,  DOI: 10.1021/cr050977s
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    Structures and oxide mobility in Bi-Ln-O materials. Heritage of Bi2O3
    Drache, Michel; Roussel, Pascal; Wignacourt, Jean-Pierre
    Chemical Reviews (Washington, DC, United States) (2007), 107 (1), 80-96CODEN: CHREAY; ISSN:0009-2665. (American Chemical Society)
    A review is given on the crystal structures of the Ln-Bi-based oxides, which are related to the structure of the Bi2O3 polymorphs. First, the 6 polymorphs of Bi2O3 are presented, and their structural relationships are discussed. Then, the stable and metastable phases of LnxBi1-xO1.5 are described. Further phases being discussed here are: (i) the rhombohedral LnxBi1-xO1.5 phases of the Bi-Sr-O type with Ln = La-Er, Y, (ii) the orthorhombic Ln7Bi17O36-type phases with Ln = Tm-Lu, (iii) the ordered cubic Ln3Bi5O12-type phases with Ln = Sm-Yb, (iv) the triclinic LnBiO3-type phases with Ln = Dy-Lu, Y, and (v) the LnxBi1-xO1.5 phases with x ≥ 0.5 and Ln = La-Ho, Y. The synthesis conditions and the structural features are tabulated. The phase diagrams of LnxBi1-xO1.5 (x = 0-80%) are given, and the behavior of the elec. cond. is discussed.
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    Malavasi, L. C. A. J.; Fisher, M. S.; Islam, M. S. Oxide-ion proton conducting electrolyte materials for clean energy applications: structural and mechanistic features. Chem. Soc. Rev. 2010, 39, 4370– 4387,  DOI: 10.1039/b915141a
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    Oxide-ion and proton conducting electrolyte materials for clean energy applications: structural and mechanistic features
    Malavasi, Lorenzo; Fisher, Craig A. J.; Islam, M. Saiful
    Chemical Society Reviews (2010), 39 (11), 4370-4387CODEN: CSRVBR; ISSN:0306-0012. (Royal Society of Chemistry)
    This crit. review presents an overview of the various classes of oxide materials exhibiting fast oxide-ion or proton cond. for use as solid electrolytes in clean energy applications such as solid oxide fuel cells. Emphasis is placed on the relationship between structural and mechanistic features of the cryst. materials and their ion conduction properties. After describing well-established classes such as fluorite- and perovskite-based oxides, new materials and structure-types are presented. These include a variety of molybdate, gallate, apatite silicate/germanate and niobate systems, many of which contain flexible structural networks, and exhibit different defect properties and transport mechanisms to the conventional materials. It is concluded that the rich chem. of these important systems provides diverse possibilities for developing superior ionic conductors for use as solid electrolytes in fuel cells and related applications. Tn most cases, a greater at.-level understanding of the structures, defects, and conduction mechanisms is achieved through a combination of exptl. and computational techniques.
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    Walsh, A.; Watson, G. W.; Payne, D. J.; Edgell, R. G.; Guo, J.; Glans, P. A.; Learmonth, T.; Smith, K. E. Electronic structure of the α and δ phase of Bi2O3: A combined ab initio and x-ray spectroscopy study. Phys. Rev. B: Condens. Matter Mater. Phys. 2006, 73, 235104,  DOI: 10.1103/physrevb.73.235104
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    Electronic structure of the α and δ phases of Bi2O3: A combined ab initio and x-ray spectroscopy study
    Walsh, Aron; Watson, Graeme W.; Payne, David J.; Edgell, Russell G.; Guo, Jinghua; Glans, Per-Anders; Learmonth, Timothy; Smith, Kevin E.
    Physical Review B: Condensed Matter and Materials Physics (2006), 73 (23), 235104/1-235104/13CODEN: PRBMDO; ISSN:1098-0121. (American Physical Society)
    α-Bi2O3 is the thermodynamically stable phase of Bi2O3 at room temp. The authors have performed a theor. and exptl. study of its electronic structure using a combination of gradient cor. d. functional theory (DFT), along with x-ray photoemission and O-K shell x-ray absorption and emission spectroscopies. The authors examine the nature of bonding in α-Bi2O3 and in particular explore the nature of the stereochem. active Bi electron lone pair. The Bi 6s states are concd. at the bottom of the valence band but the states contributing to the lone pair on Bi are derived from the top of the valence band. Mixing between O 2p and Bi 6s states is crucial in producing the asym. d. on Bi. The role of the lone pair in the fast ion conductor δ-Bi2O3 is also studied, through calcn. of the electronic structure with <100>, <110>, and <111> alignment of O vacancies. Alignment of the vacancies along <100> results in the most energetically favorable configuration of the δ phase, contrary to previous force field calcns. and electrostatic arguments which favor the <111> alignment.
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    Walsh, A.; Watson, G. W. Polymorphism in Bismuth Stannate: A First-Principles Study. Chem. Mater. 2007, 19, 5158– 5164,  DOI: 10.1021/cm0714279
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    Polymorphism in Bismuth Stannate: A First-Principles Study
    Walsh, Aron; Watson, Graeme W.
    Chemistry of Materials (2007), 19 (21), 5158-5164CODEN: CMATEX; ISSN:0897-4756. (American Chemical Society)
    From the wide range of SnIV-based pyrochlores, Bi2Sn2O7 stands out as a material that deviates from the std. cubic-lattice symmetry. At low temps., Bi2Sn2O7 adopts a distorted monoclinic √2 × √2 × 2 expansion of the pyrochlore structure (α-phase) and only favors the cubic lattice (γ-phase) >900 K. The authors calc. and examine the electronic structure of both the α- and γ-phases of Bi2Sn2O7 and compare them to the results of two regular pyrochlore materials, La2Sn2O7 and Y2Sn2O7. The authors' anal. highlights the importance of covalent interactions between the electronic states of the metal with O 2p in Bi2Sn2O7, which are not present in the other oxides. The formation of an asym. electron d. on Bi is obsd. as the driving force behind the distorted geometry favored by Bi2Sn2O7.
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    Tauc, J.; Grigorovici, R.; Vancu, A. Optical properties and electronic structure of amorphous germanium. Phys. Status Solidi B 1966, 15, 627– 637,  DOI: 10.1002/pssb.19660150224
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    Optical properties and electronic structure of amorphous germanium
    Tauc, J.; Grigorovici, R.; Vancu, A.
    Physica Status Solidi (1966), 15 (2), 627-37CODEN: PHSSAK; ISSN:0031-8957.
    The optical consts. of amorphous Ge are detd. for photon energies 0.08-1.6 ev. From 0.08 to 0.5 ev., the absorption is due to k-conserving transitions of holes between the valence bands as in p-type crystals; the spin-orbit splitting is 0.20 and 0.21 ev. in nonannealed and annealed samples, resp. The effective masses of the holes in the 3 bands are 0.49 m (0.43 m), 0.04 m, and 0.08 m. An absorption band is observed below the main absorption edge (at 300°K. the max. of this band is at 0.86 ev.); the absorption in this band increases with increasing temp. This band is due to excitons bound to neutral acceptors, and these are presumably the same ones that play a decisive role in the transport properties, which are considered to be assocd. with vacancies. The absorption edge has the form ω2ε2 ∼ (ℏω - Eg)2 (Eg = 0.88 ev. at 300°K.). This suggests that the optical transitions conserve energy but not k vector, and that the ds. of states near the band extrema have the same energy dependence as in cryst. Ge. A simple theory describing this situation is proposed, and comparison of it with the exptl. results leads to an estimate of the localization of the conduction-band wave functions. 24 references.
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    Cheng, H.; Huang, B.; Lu, J.; Wang, Z.; Xu, B.; Qin, X.; Zhang, X.; Dai, Y. Synergistic effect of crystal and electronic structures on the visible-light-driven photocatalytic performances of Bi2O3 polymorphs. Phys. Chem. Chem. Phys. 2010, 12, 15468– 15475,  DOI: 10.1039/c0cp01189d
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    Synergistic effect of crystal and electronic structures on the visible-light-driven photocatalytic performances of Bi2O3 polymorphs
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    Physical Chemistry Chemical Physics (2010), 12 (47), 15468-15475CODEN: PPCPFQ; ISSN:1463-9076. (Royal Society of Chemistry)
    Three polymorphs of Bi2O3 were selectively synthesized via soln.-based methods. The phase structures of the as-prepd. samples were confirmed by x-ray powder diffraction (XRD) and XPS. UV-vis diffuse reflectance spectroscopy was employed to study the optical properties of Bi2O3 polymorphs, and the band gaps were estd. to be 2.80, 2.48, and 3.01 eV for α-Bi2O3, β-Bi2O3, and δ-Bi2O3, resp. The photocatalytic performances of the oxides were investigated by decompg. Methyl orange and 4-chlorophenol under visible irradn. at room temp. It was obsd. that β-Bi2O3 displayed much higher photocatalytic performance than N-doped P25. Among the three polymorphs of Bi2O3, the photocatalytic activities followed the order: β-Bi2O3 > α-Bi2O3 > δ-Bi2O3, which was in good accordance with the photoluminescence spectra measurement results. The synergistic effect of the crystal and electronic structures on the photocatalytic performances of Bi2O3 polymorphs was investigated. The much better photocatalytic activity of β-Bi2O3 was considered to be closely related to its smaller band gap, higher crystallinity and unique tunnel structure.
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    Crystal Growth & Design (2015), 15 (3), 1031-1042CODEN: CGDEFU; ISSN:1528-7483. (American Chemical Society)
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    Bismuth-based fluoride nanocryst. particles have recently attracted much attention as hosts for luminescent ions such as lanthanides (Ln) being proposed for lighting devices and biol. applications. However, a comprehensive investigation on the chem. properties of this family of materials, the growth of the nanoparticles, and information about the chem. and thermal stabilities are crit. to assess the real potential of nanosystems. In this view, a combined exptl. and theor. approach is employed to investigate the cryst. and electronic structure of BiF3 and NaBiF4. A detailed spectroscopic investigation allows us to measure the exciton peaks of these fluoride compds. for the first time and to design the vacuum referred binding energy level diagram of the lanthanide-doped fluorides with respect to the valence and conduction bands of the hosts in comparison with conventional fluorides. In addn., temp. and water effects on the chem. stability of NaBiF4 were addressed, evidencing detrimental limitations and envisaging possible solns. in view of biol. applications.
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    Near-IR (NIR) emitting contrast agents with integrated optical temp. sensing are highly desirable for a variety of biomedical applications, particularly when s.c. target visualization and measurement of its thermodn. properties are required. To that end, the possibility of using Nd3+ doped LiLuF4 rare-earth nanoparticles (RENPs) as NIR photoluminescent nanothermometers is explored. These RENPs are relatively small, have narrow size distribution, and can easily be core/shell engineered - all combined, these features meet the requirements of biol. relevant and multifunctional nanoprobes. The LiLuF4 host allows to observe the fine Stark structure of the 4F3/2 → 4I9/2, 4I11/2, and 4I13/2 optical transitions, each of which can then be used for single-band NIR nanothermometry. The thermometric parameter defined for the most intense Nd 3+ emission around 1050 nm, shows high temp. sensitivity (∼0.49% ° C -1), and low temp. uncertainty (0.3°C) as compared to the thermometric parameters defined for the 880 and 1320 nm Nd 3+ emissions. Addnl., transient temp. measurements through tissue show that these RENPs can be used to assess fast temp. changes at a tissue depth of 3 mm, while slower temp. changes can be measured at even greater depths. Nd 3+ doped LiLuF4 RENPs represent a significant improvement for Nd 3+ based single-band photoluminescence nanothermometry, with the possibility of its integration within more sophisticated multifunctional theranostic nanostructures.
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    Nanomaterials (2020), 10 (3), 543CODEN: NANOKO; ISSN:2079-4991. (MDPI AG)
    Herein, we demonstrate and discuss various pitfalls that can occur in Boltzmann thermometry if this particular LIR is used for physiol. temp. sensing. Both microcryst., dil. (0.1%) Nd3+-doped LaPO4 and LaPO4: x% Nd3+ (x = 2, 5, 10, 25, 100) nanocrystals serve as an illustrative example. Besides structural and optical characterization of those luminescent thermometers, the impact and consequences of the Nd3+ concn. on their luminescence and performance as Boltzmann-based thermometers are analyzed. At higher Nd3+ concns., cross-relaxation processes enhance the decay rates of the 4F3/2 and 4F5/2 levels making the decay faster than the equilibration rates between the levels. It is shown that the onset of the useful temp. sensing range shifts to higher temps., even above ~ 450 K for Nd concns. over 5%. A microscopic explanation for pitfalls in Boltzmann thermometry with Nd3+ is finally given and guidelines for the usability of this lanthanide ion in the field of physiol. temp. sensing are elaborated. Insight in competition between thermal coupling through non-radiative transitions and population decay through cross-relaxation of the 4F5/2 and 4F3/2 spin-orbit levels of Nd3+ makes it possible to tailor the thermometric performance of Nd3+ to enable physiol. temp. sensing.
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    Confined-Melting-Assisted Synthesis of Bismuth Silicate Glass-Ceramic Nanoparticles: Formation and Optical Thermometry Investigation
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    Bismuth-based (nano)materials have been attracting increasing interest due to appealing properties such as high refractive indexes, intrinsic opacity, and structural distortions due to the stereochem. of 6s2 lone pair electrons of Bi3+. However, the control over specific phases and strategies able to stabilize uniform bismuth-based (nano)materials is still a challenge. In this study, we employed the ability of bismuth to lower the m.p. of silica to introduce a new synthetic approach able to confine the growth of bismuth-oxide-based materials into nanostructures. Combining in situ temp.-dependent synchrotron radiation X-ray powder diffraction (XRPD) with high-resoln. transmission electron microscopy (HR-TEM) analyses, we demonstrate the evolution of a confined Bi2O3-SiO2 nanosystem from Bi2SiO5 to Bi4Si3O12 through a melting process. The silica shell acts as both a nanoreactor and a silicon source for the stabilization of bismuth silicate glass-ceramic nanocrystals keeping the original spherical shape. The exciton peak of Bi2SiO5 is measured for the first time allowing the estn. of its real energy gap. Moreover, based on a detailed spectroscopic investigation, we discuss the potential and the limitations of Nd3+-activated bismuth silicate systems as ratiometric thermometers. The synthetic strategy introduced here could be further explored to stabilize other bismuth-oxide-based materials, opening the way toward the growth of well-defined glass-ceramic nanoparticles.
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    The increasing interest in the development of ratiometric optical thermal sensors led to a wide variety of new systems with promising properties. Among them, singly-doped ratiometric thermometers were recently demonstrated to be particularly reliable. With the aim to discuss the development of an ideal optical thermal sensor, a combined exptl. and theor. insight into the spectroscopy of the Bi2Ga4O9:Cr3+ system is reported showing the importance of an insightful anal. in a wide temp. range. Low-temp. luminescence anal. (from 10 K) and the temp. dependence of the lifetime study, together with the crystal field anal. and the modeling of the thermal quenching process, allow the estn. of key parameters such as the Debye temp. (cutoff frequency), the Huang-Rhys parameter, and the energy barrier between 2Eg and 4T2g. Addnl., by considering the reliable class of singly-doped ratiometric thermometers based on a couple of excited states obeying the Boltzmann law, the important role played by the abs. sensitivity was discussed and the great potential of Cr3+ singly-activated systems was demonstrated. The results may provide new guidelines for the design of reliable optical thermometers with outstanding and robust performances.
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Cite this: Chem. Mater. 2022, 34, 18, 8198–8206
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https://doi.org/10.1021/acs.chemmater.2c01262
Published September 11, 2022

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  • Abstract

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    Figure 1

    Figure 1. Crystalline and electronic structure of the tetragonal β-Bi2O3:Y3+,Nd3+ polymorph. (a) XRPD pattern along with Rietveld refinement and difference profile. (b) Crystalline structure and (c) local site of substitution for Nd3+ in β-Bi2O3:Y3+,Nd3+. (d) T-DOS and P-DOS projected onto each constituent element.

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    Figure 2

    Figure 2. Electronic structure and optical properties of the narrow band gap β-Bi2O3:Y3+,Nd3+. (a) Reflectance and PLE spectra collecting at 1060 nm along with the picture of the sample. (b) Tauc plot of the Kubelka–Munk function F(R) for the estimation of the band gap energy. (c) Room temperature PL spectrum by exciting at 745 nm. (d) VRBE diagram for Nd3+ in β-Bi2O3:Y3+,Nd3+.

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    Figure 3

    Figure 3. NIR-to-NIR Boltzmann thermometry. (a) Temperature dependence of the PL spectra in the 100–600 K range exciting at 745 nm spectra, normalized to the 4F3/2 → 4I9/2 emission. Boltzmann plot to calibrate the thermometers based on the ratio between 4F3/2 and 4F5/2 (b) and between the Kramers doublets Z-levels of 4F3/2 (c) with the corresponding linear fits. (d) Temperature dependence of the absolute (Sa) and relative (Sr) sensitivities and (e) repeatability (R).

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    Figure 4

    Figure 4. New thermometric parameters based on the temperature dependence of the reflectance spectra and colorimetric parameters. Temperature dependence of (a) reflectance spectra (the vertical dashed lines represent the reflectance values used for the RIR parameter), (b) Kubelka–Munk function and (c) Tauc plot for the estimation of the optical band gap energy. (d) Temperature dependence of the band gap energy with the linear fit. (e) Reflectance intensity ratio (RIR) used as the thermal parameter along with the absolute (Sa) and relative (Sr) sensitivities and (f) sketch of the thermometric parameter introduced based on the narrow band gap and the Nd3+ f–f transitions. (g) Thermochromic variation based on the colorimetric parameters a* and b* as a function of the temperature in the a*b* space, (h) thermometric parameter a*/b*, (i) hue angle hab, and relative thermometric parameter values (j) Sa and (k) Sr.

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      Rasche, Bertold; Isaeva, Anna; Ruck, Michael; Borisenko, Sergey; Zabolotnyy, Volodymyr; Buechner, Bernd; Koepernik, Klaus; Ortix, Carmine; Richter, Manuel; van den Brink, Jeroen
      Nature Materials (2013), 12 (5), 422-425CODEN: NMAACR; ISSN:1476-1122. (Nature Publishing Group)
      Commonly, materials are classified as either elec. conductors or insulators. The theor. discovery of topol. insulators has fundamentally challenged this dichotomy. In a topol. insulator, the spin-orbit interaction generates a non-trivial topol. of the electronic band structure dictating that its bulk is perfectly insulating, whereas its surface is fully conducting. The 1st topol. insulator candidate material put forward-graphene-is of limited practical use because its weak spin-orbit interactions produce a bandgap of ∼0.01 K. Recent reexamns. of Bi2Se3 and Bi2Te3, however, have firmly categorized these materials as strong 3D topol. insulators. We have synthesized the 1st bulk material belonging to an entirely different, weak, topol. class, built from stacks of 2D topol. insulators: Bi14Rh3I9. Its Bi-Rh sheets are graphene analogs, but with a honeycomb net composed of RhBi8 cubes rather than C atoms. The strong Bi-related spin-orbit interaction renders each graphene-like layer a topol. insulator with a 2,400 K bandgap.
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    17. 17
      Autès, G.; Isaeva, A. L.; Moreschini, J. C.; Johannsen, A.; Pisoni, R.; Mori, W.; Zhang, T. G.; Filatova, A. N.; Kuznetsov, L.; Forró, W.; Van den Broek, Y.; Kim, K. S. A novel quasi-one-dimensional topological insulator in bismuth iodide β-Bi4I4. Nat. Mater. 2016, 15, 154– 158,  DOI: 10.1038/nmat4488
      17
      A novel quasi-one-dimensional topological insulator in bismuth iodide β-Bi4I4
      Autes, Gabriel; Isaeva, Anna; Moreschini, Luca; Johannsen, Jens C.; Pisoni, Andrea; Mori, Ryo; Zhang, Wentao; Filatova, Taisia G.; Kuznetsov, Alexey N.; Forro, Laszlo; Van den Broek, Wouter; Kim, Yeongkwan; Kim, Keun Su; Lanzara, Alessandra; Denlinger, Jonathan D.; Rotenberg, Eli; Bostwick, Aaron; Grioni, Marco; Yazyev, Oleg V.
      Nature Materials (2016), 15 (2), 154-158CODEN: NMAACR; ISSN:1476-1122. (Nature Publishing Group)
      Recent progress in the field of topol. states of matter has largely been initiated by the discovery of bismuth and antimony chalcogenide bulk topol. insulators (TIs; refs. ,,,), followed by closely related ternary compds. and predictions of several weak TIs (refs. ,,). However, both the conceptual richness of Z2 classification of TIs as well as their structural and compositional diversity are far from being fully exploited. Here, a new Z2 topol. insulator is theor. predicted and exptl. confirmed in the β-phase of quasi-one-dimensional bismuth iodide Bi4I4. The electronic structure of β-Bi4I4, characterized by Z2 invariants (1;110), is in proximity of both the weak TI phase (0;001) and the trivial insulator phase (0;000). The authors' angle-resolved photoemission spectroscopy measurements performed on the (001) surface reveal a highly anisotropic band-crossing feature located at the M- point of the surface Brillouin zone and showing no dispersion with the photon energy, thus being fully consistent with the theor. prediction.
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    18. 18
      Zaccariello, G.; Back, M.; Zanello, M.; Canton, P.; Cattaruzza, E.; Riello, P.; Alimonti, A.; Benedetti, A. Formation and controlled growth of bismuth titanate phases into mesoporous silica nanoparticles: An efficient self-sealing nanosystem for UV filtering in cosmetic formulation. ACS Appl. Mater. Interfaces 2017, 9, 1913– 1921,  DOI: 10.1021/acsami.6b13252
      18
      Formation and Controlled Growth of Bismuth Titanate Phases into Mesoporous Silica Nanoparticles: An Efficient Self-Sealing Nanosystem for UV Filtering in Cosmetic Formulation
      Zaccariello, Gloria; Back, Michele; Zanello, Marta; Canton, Patrizia; Cattaruzza, Elti; Riello, Pietro; Alimonti, Alessandro; Benedetti, Alvise
      ACS Applied Materials & Interfaces (2017), 9 (2), 1913-1921CODEN: AAMICK; ISSN:1944-8244. (American Chemical Society)
      The application of nanosized inorg. UV filters in cosmetic field is limited by their high photocatalytic properties that could induce the degrdn. or dangerous transformation of the org. mols. in sunscreen formulations. To overcome this problem and simultaneously enlarge the window of filter's absorption, we propose the growth of bismuth titanates BixTiyOz into mesoporous silica nanoparticles (MSN). We investigated the chem.-phys. properties by means of XRPD, TEM, UV-vis spectroscopy, N2 physisorption, XPS, and SF-ICP-MS anal., while the influence on the environment was evaluated through photocatalytic tests. The growing process of this new nanosystem is discussed underlining the key role of the Bi3+ ion that, acting as a low-m.p. agent for the silica framework, led to a self-sealing mechanism. The excellent UV shielding properties combined with a radical suppression of the photocatalytic activity make the proposed nanosystem a perfect candidate for the development of the next generation nanomaterials for sunscreen formulations.
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    19. 19
      Zaccariello, G. M.; Back, A.; Benedetti, P.; Canton, E.; Cattaruzza, H.; Onoda, A.; Glisenti, A.; Alimonti, B.; Bocca, P.; Riello, P. Bismuth titanate-based UV filters embedded mesoporous silica nanoparticles: Role of bismuth concentration in the self-sealing process. J. Colloid Interface Sci. 2019, 549, 1– 8,  DOI: 10.1016/j.jcis.2019.04.042
      19
      Bismuth titanate-based UV filters embedded mesoporous silica nanoparticles: Role of bismuth concentration in the self-sealing process
      Zaccariello, Gloria; Back, Michele; Benedetti, Alvise; Canton, Patrizia; Cattaruzza, Elti; Onoda, Hiroaki; Glisenti, Antonella; Alimonti, Alessandro; Bocca, Beatrice; Riello, Pietro
      Journal of Colloid and Interface Science (2019), 549 (), 1-8CODEN: JCISA5; ISSN:0021-9797. (Elsevier B.V.)
      The development of new safe inorg. UV filters to effectively protect the skin from UV radiation effects is an emerging issue. Bismuth titanate-based UV filters embedded into mesoporous silica nanoparticles (MSN) represent a new class of inorg. sunscreens, with excellent UVA and UVB shielding properties. In addn., the presence of bismuth ions promotes a self-sealing process, allowing (i) the entrapment of the active phases in the deepest core of the system and (ii) the formation of an external glassy silica layer with a consequent suppression of the photocatalytic activity. In this work, aimed at studying in detail the self-sealing mechanism and accessing the role of bismuth ions in the formation of the system, a series of samples impregnated with a different amt. of bismuth were investigated. The self-sealing process already occurs at the lowest content of bismuth and the mechanism is demonstrated to be triggered by the ability of Bi to work as a low-m.p. agent for silica. Finally, a sunscreen formulation contg. the new UV filter was prepd. and the Sun Protection Factor (SPF), the pH and the viscosity were measured, demonstrating the potential of the proposed material for large-scale applications.
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    20. 20
      Chen, A.; Zhou, H.; Bi, Z.; Zhu, Y.; Luo, Z.; Bayraktaroglu, A.; Phillips, J.; Choi, E.-M.; MacManus-Discoll, J. L.; Pennycook, S. J. A new class of room-temperature multiferroic thin films with bismuth-based supercell structure. Adv. Mater. 2013, 25, 1028– 1032,  DOI: 10.1002/adma.201203051
      20
      A New Class of Room-Temperature Multiferroic Thin Films with Bismuth-Based Supercell Structure
      Chen, Aiping; Zhou, Honghui; Bi, Zhenxing; Zhu, Yuanyuan; Luo, Zhiping; Bayraktaroglu, Adrian; Phillips, Jamie; Choi, Eun-Mi; MacManus-Driscoll, Judith L.; Pennycook, Stephen J.; Narayan, Jagdish; Jia, Quanxi; Zhang, Xinghang; Wang, Haiyan
      Advanced Materials (Weinheim, Germany) (2013), 25 (7), 1028-1032CODEN: ADVMEW; ISSN:0935-9648. (Wiley-VCH Verlag GmbH & Co. KGaA)
      In this study, the authors present a new class of room-temp. multiferroics based on two partially miscible phases of BiFeO3 and BiMnO3, with a new structure enabled by epitaxial strain. The new BFMO single phase shows a bismuth supercell (SC) structure on LaAlO3 (LAO) substrates and exhibits both ferrimagnetic and ferroelec. responses at room temp. More interestingly, this new phase can be formed on other substrates with a properly selected buffer layer. The XRD patterns and structure are described.
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    21. 21
      Huang, H.; Wang, Z.; Huang, B.; Wang, P.; Zhang, X.; Qin, X.; Dai, Y.; Zhou, G.; Whangbo, M.-H. Intense single red emission induced by near-infrared irradiation using a narrow bandgap oxide BiVO4 as the host for Yb3+ and Tm3+ ions. Adv. Opt. Mater. 2018, 6, 1701331,  DOI: 10.1002/adom.201701331
      There is no corresponding record for this reference.
    22. 22
      Okabe, K.; Inada, N.; Gota, C.; Harada, Y.; Funatsu, T.; Uchiyama, S. Intracellular temperature mapping with a fluorescent polymeric thermometer and fluorescence lifetime imaging microscopy. Nat. Commun. 2012, 3, 705,  DOI: 10.1038/ncomms1714
      22
      Intracellular temperature mapping with a fluorescent polymeric thermometer and fluorescence lifetime imaging microscopy
      Okabe Kohki; Inada Noriko; Gota Chie; Harada Yoshie; Funatsu Takashi; Uchiyama Seiichi
      Nature communications (2012), 3 (), 705 ISSN:.
      Cellular functions are fundamentally regulated by intracellular temperature, which influences biochemical reactions inside a cell. Despite the important contributions to biological and medical applications that it would offer, intracellular temperature mapping has not been achieved. Here we demonstrate the first intracellular temperature mapping based on a fluorescent polymeric thermometer and fluorescence lifetime imaging microscopy. The spatial and temperature resolutions of our thermometry were at the diffraction limited level (200 nm) and 0.18-0.58 °C. The intracellular temperature distribution we observed indicated that the nucleus and centrosome of a COS7 cell, both showed a significantly higher temperature than the cytoplasm and that the temperature gap between the nucleus and the cytoplasm differed depending on the cell cycle. The heat production from mitochondria was also observed as a proximal local temperature increase. These results showed that our new intracellular thermometry could determine an intrinsic relationship between the temperature and organelle function.
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    23. 23
      Piñol, R.; Zeler, J.; Brites, C. D. S.; Gu, Y.; Téllez, P.; Carneiro Neto, A. N.; da Silva, T. E.; Moreno-Loshuertos, R.; Fernandez-Silva, P.; Gallego, A. I.; Martinez-Lostao, L.; Martínez, A.; Carlos, L. D.; Millán, A. Real-time intracellular temperature imaging using lanthanide-bearing polymeric micelles. Nano Lett. 2020, 20, 6466– 6472,  DOI: 10.1021/acs.nanolett.0c02163
      23
      Real-Time Intracellular Temperature Imaging Using Lanthanide-Bearing Polymeric Micelles
      Pinol, Rafael; Zeler, Justyna; Brites, Carlos D. S.; Gu, Yuanyu; Tellez, Pedro; Carneiro Neto, Albano N.; da Silva, Thiago E.; Moreno-Loshuertos, Raquel; Fernandez-Silva, Patricio; Gallego, Ana Isabel; Martinez-Lostao, Luis; Martinez, Abelardo; Carlos, Luis D.; Millan, Angel
      Nano Letters (2020), 20 (9), 6466-6472CODEN: NALEFD; ISSN:1530-6984. (American Chemical Society)
      Measurement of thermogenesis in individual cells is a remarkable challenge due to the complexity of the biochem. environment (such as pH and ionic strength) and to the rapid and yet not well-understood heat transfer mechanisms throughout the cell. Here, the authors present a unique system for intracellular temp. mapping in a fluorescence microscope (uncertainty of 0.2 K) using rationally designed luminescent Ln3+-bearing polymeric micellar probes (Ln = Sm, Eu) incubated in breast cancer MDA-MB468 cells. Two-dimensional (2D) thermal images recorded increasing the temp. of the cells culture medium between 296 and 304 K shows inhomogeneous intracellular temp. progressions up to ~ 20 degrees and subcellular gradients of ~ 5 degrees between the nucleolus and the rest of the cell, illustrating the thermogenic activity of the different organelles and highlighting the potential of this tool to study intracellular processes.
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    24. 24
      Bednarkiewicz, A.; Drabik, J.; Trejgis, K.; Jaque, D.; Ximendes, E.; Marciniak, L. Luminescence based temperature bio-imaging: Status, challenges, and perspectives. Appl. Phys. Rev. 2021, 8, 011317,  DOI: 10.1063/5.0030295
      24
      Luminescence based temperature bio-imaging: Status, challenges, and perspectives
      Bednarkiewicz, A.; Drabik, J.; Trejgis, K.; Jaque, D.; Ximendes, E.; Marciniak, L.
      Applied Physics Reviews (2021), 8 (1), 011317CODEN: APRPG5; ISSN:1931-9401. (American Institute of Physics)
      A review. The only way to get thermal images of living organisms without perturbing them is to use luminescent probes with temp.-dependent spectral properties. The acquisition of such thermal images becomes essential to distinguish various states of cells, to monitor thermogenesis, to study cellular activity, and to control hyperthermia therapy. Current efforts are focused on the development and optimization of luminescent reporters such as small mols., proteins, quantum dots, and lanthanide-doped nanoparticles. However, much less attention is devoted to the methods and technologies that are required to image temp. distribution at both in vitro or in vivo levels. Indeed, rare examples can be found in the scientific literature showing technologies and materials capable of providing reliable 2D thermal images of living organisms. In this review article, examples of 2D luminescence thermometry are presented alongside new possibilities and directions that should be followed to achieve the required level of simplicity and reliability that ensure their future implementation at the clin. level. This review will inspire specialists in chem., physics, biol., medicine, and engineering to collaborate with materials scientists to jointly develop novel more accurate temp. probes and enable mapping of temp. with simplified tech. means. (c) 2021 American Institute of Physics.
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    25. 25
      van Swieten, T. P.; van Omme, T.; van den Heuvel, D. J.; Vonk, S. J. W.; Spruit, R. G.; Meirer, F.; Garza, H. H. P.; Weckhuysen, B. M.; Meijerink, A.; Rabouw, F. T.; Geitenbeek, R. G. Mapping elevated temperatures with a micrometer resolution using the luminescence of chemically stable upconversion nanoparticles. ACS Appl. Nano Mater. 2021, 4, 4208– 4215,  DOI: 10.1021/acsanm.1c00657
      25
      Mapping Elevated Temperatures with a Micrometer Resolution Using the Luminescence of Chemically Stable Upconversion Nanoparticles
      van Swieten, Thomas P.; van Omme, Tijn; van den Heuvel, Dave J.; Vonk, Sander J. W.; Spruit, Ronald G.; Meirer, Florian; Garza, H. Hugo Perez; Weckhuysen, Bert M.; Meijerink, Andries; Rabouw, Freddy T.; Geitenbeek, Robin G.
      ACS Applied Nano Materials (2021), 4 (4), 4208-4215CODEN: AANMF6; ISSN:2574-0970. (American Chemical Society)
      Nanothermometry with high spatial resolns. at elevated temps. is realized using chem. stable upconversion nanoparticles and confocal microscopy. This method is tested on a microelectromech. heater, and the temp. homogeneity was studied. The expts. reveal distortions in the luminescence spectra that are intrinsic to high-resoln. measurements of samples with nanoscale photonic inhomogeneities. The spectra are affected by the high-power excitation as well as by scattering and reflection of the emitted light. The latter effect has an increasing impact at elevated temps. A procedure to correct these distortions is presented. The range of high-resoln. nanothermometry beyond 500 K was extended with a precision of 1-4 K. This work will improve the accuracy of nanothermometry not only in micro- and nanoelectronics but also in other fields with photonically inhomogeneous substrates.
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    26. 26
      Back, M.; Ueda, J.; Xu, J.; Murata, D.; Brik, M. G.; Tanabe, S. Ratiometric luminescent thermometers with a customized phase-transition-driven fingerprint in perovskite oxides. ACS Appl. Mater. Interfaces 2019, 11, 38937– 38945,  DOI: 10.1021/acsami.9b13010
      26
      Ratiometric Luminescent Thermometers with a Customized Phase-Transition-Driven Fingerprint in Perovskite Oxides
      Back, Michele; Ueda, Jumpei; Xu, Jian; Murata, Daisuke; Brik, Mikhail G.; Tanabe, Setsuhisa
      ACS Applied Materials & Interfaces (2019), 11 (42), 38937-38945CODEN: AAMICK; ISSN:1944-8244. (American Chemical Society)
      The development of non-contact thermometers with self-control to specific temps. to be used as control markers with an addnl. degree of reliability is a challenge in the field of thermal sensors. Herein, a strategy exploiting the wide tunability of an intrinsic feature of oxide perovskites such as the phase transition temp. to design a new class of ratiometric luminescent thermometers is introduced. The structural and optical response to the thermal stimuli of LaGaO3:Nd3+ system is used as a prototype to show the unprecedented opportunity to combine the processes of two different regimes in the same compd. leading to a reliable optical thermal sensor with an intrinsic tell-tale sign at specific temps. High relative sensitivity, low temp. uncertainty and good reproducibility, together with the need of a single calibration curve irresp. to the phase transition temp. and the doping effects, attest the goodness of the thermometric performances. This work demonstrates the control of the phase transition (orthorhombic ↔ rhombohedral) temp. Tc of lanthanum gallate in the 400-700 K range by carefully doping the perovskite structure, as proof of concept for the design of customized thermometers characterized by a spectral shape change acting as a self-fingerprint for the Tc.
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    27. 27
      Brites, C. D. S.; Zhuang, B.; Debasu, M. L.; Ding, D.; Qin, X.; Maturi, F. E.; Lim, W. W. Y.; Soh, D. W.; Rocha, J.; Yi, Z.; Liu, X.; Carlos, L. D. Decoding a percolation phase transition of water at ∼330 K with a nanoparticle ruler. J. Phys. Chem. Lett. 2020, 11, 6704– 6711,  DOI: 10.1021/acs.jpclett.0c02147
      27
      Decoding a Percolation Phase Transition of Water at ~ 330 K with a Nanoparticle Ruler
      Brites, Carlos D. S.; Zhuang, Bilin; Debasu, Mengistie L.; Ding, Ding; Qin, Xian; Maturi, Fernando E.; Lim, Winnie W. Y.; Soh, De Wen; Rocha, J.; Yi, Zhigao; Liu, Xiaogang; Carlos, Luis D.
      Journal of Physical Chemistry Letters (2020), 11 (16), 6704-6711CODEN: JPCLCD; ISSN:1948-7185. (American Chemical Society)
      Liq. water, despite its simple mol. structure, remains one of the most fascinating and complex substances. Most notably, many questions continue to exist regarding the phase transitions and anomalous properties of water, which are subtle to observe exptl. Here, we report a sharp transition in water at 330 K unveiled through exptl. measurements of the instantaneous Brownian velocity of NaYF4:Yb/Er upconversion nanoparticles in water. Our exptl. investigations, corroborated by mol. dynamics simulations, elucidate a geometrical phase transition where a low-d. liq. (LDL) clusters become percolated below 330 K. Around this crit. temp., we find the sizes of the LDL clusters to be similar to those of the nanoparticles, confirming the role of the upconversion nanoparticle as a powerful ruler for measuring the extensiveness of the LDL hydrogen-bond network and nanometer-scale spatial changes (20-100 nm) in liqs. Addnl., a new order parameter that unequivocally classifies water mols. into two local geometric states is introduced, providing a new tool for understanding and modeling water's many anomalous properties and phase transitions.
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    28. 28
      Geitenbeek, R. G.; Nieuwelink, A.-E.; Jacobs, T. S.; Salzmann, B. B. V.; Goetze, J.; Meijerink, A.; Weckhuysen, B. M. In situ luminescence thermometry to locally measure temperature gradients during catalytic reactions. ACS Catal. 2018, 8, 2397– 2401,  DOI: 10.1021/acscatal.7b04154
      28
      In Situ Luminescence Thermometry To Locally Measure Temperature Gradients during Catalytic Reactions
      Geitenbeek, Robin G.; Nieuwelink, Anne-Eva; Jacobs, Thimo S.; Salzmann, Bastiaan B. V.; Goetze, Joris; Meijerink, Andries; Weckhuysen, Bert M.
      ACS Catalysis (2018), 8 (3), 2397-2401CODEN: ACCACS; ISSN:2155-5435. (American Chemical Society)
      Bandshape luminescence thermometry during in situ temp. measurements has been reported by prepg. three catalytically relevant systems, which show temp.-dependent luminescence. One of these systems was further investigated as a showcase for application. Microcryst. NaYF4 doped with Er3+ and Yb3+ was mixed with a com. zeolite H-ZSM-5 to investigate the Methanol-to-Hydrocarbons (MTH) reaction, while monitoring the reaction products with online gas chromatog. Due to the exothermic nature of the MTH reaction, a front of increased temp. migrating down the fixed reactor bed was visualized, showing the potential for various applications of luminescence thermometry for in situ measurements in catalytic systems.
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    29. 29
      Ravenhorst, I. K.; Geitenbeek, R. G.; Eerden, M. J.; Tijn van Omme, J. T.; Peréz Garza, H. H. P.; Meirer, F.; Meijerink, A.; Weckhuysen, B. M. In situ local temperature mapping in microscopy nano-reactors with luminescence thermometry. ChemCatChem 2019, 11, 5505– 5512,  DOI: 10.1002/cctc.201900985
      There is no corresponding record for this reference.
    30. 30
      Hartman, T.; Geitenbeek, R. G.; Whiting, G. T.; Weckhuysen, B. M. Operando monitoring of temperature and active species at the single catalyst particle level. Nat. Catal. 2019, 2, 986– 996,  DOI: 10.1038/s41929-019-0352-1
      30
      Operando monitoring of temperature and active species at the single catalyst particle level
      Hartman, Thomas; Geitenbeek, Robin G.; Whiting, Gareth T.; Weckhuysen, Bert M.
      Nature Catalysis (2019), 2 (11), 986-996CODEN: NCAACP; ISSN:2520-1158. (Nature Research)
      The development of improved catalysts requires insights into the relationship between catalytic activity and catalyst structure, including the underlying reaction mechanism. Here, we demonstrate a unique set of catalyst extrudate sensors that allow for the simultaneous detection of local temp. by luminescence thermometry, and of surface species by shell-isolated nanoparticle-enhanced Raman spectroscopy. This sensing approach was applied to the characterization of direct conversion of syngas into hydrocarbons and C2+ oxygenates over supported Rh and RhFe catalysts. Luminescence thermometry demonstrated a mismatch between the set temp. and the local catalyst temp., with variations up to 40 °C. Furthermore, by investigating the surface species on varying extrudate and catalyst compns., we identified tilted carbonyl species on the Rh/SiO2 interface that are probable precursors for the hydrogen-assisted CO dissocn. The implementation of extrudate catalyst sensors as a characterization tool provides a unique approach towards the further understanding of the relevant parameters in catalysis.
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    31. 31
      Back, M.; Ueda, J.; Nambu, H.; Fujita, M.; Yamamoto, A.; Yoshida, H.; Tanaka, H.; Brik, M. G.; Tanabe, S. Boltzmann thermometry in Cr3+-doped Ga2O3 polymorphs: The structure matters. Adv. Opt. Mater. 2021, 9, 2100033,  DOI: 10.1002/adom.202100033
      31
      Boltzmann Thermometry in Cr3+-Doped Ga2O3 Polymorphs: The Structure Matters
      Back, Michele; Ueda, Jumpei; Nambu, Hiroshi; Fujita, Masami; Yamamoto, Akira; Yoshida, Hisao; Tanaka, Hiromitsu; Brik, Mikhail G.; Tanabe, Setsuhisa
      Advanced Optical Materials (2021), 9 (9), 2100033CODEN: AOMDAX; ISSN:2195-1071. (Wiley-VCH Verlag GmbH & Co. KGaA)
      The performance of luminescent Cr3+-doped thermometers is strongly influenced by the locally surrounding ligand field. A universal relationship between the thermometric performance and structural/chem. parameters is highly desirable to drive the development of effective Cr3+-based thermal sensors avoiding trial-and-error procedures. In this view, as prototypes, the electronic structure and the thermometric performance of Cr3+-doped α-Ga2O3 and β-Ga2O3 polymorphs are compared. Combining a detailed theor. and spectroscopic investigation, the electronic configuration and the crystal field (CF) acting on the Cr3+ in α-Ga2O3 are described for the first time and compared with β-Ga2O3:Cr3+ polymorph to discuss the thermometric behavior. A linear relationship between the 4T2-2E energy gap (directly linked to the relative sensitivity) and the CF strength Dq is demonstrated for a wide variety of materials. This trend can be considered as a first step to set guiding principles to design effective Cr3+-based Boltzmann thermometers. In addn., as a proof of concept, particles of β-Ga2O3:Cr3+ thermometer are used to locally measure in operando thermal variations of Pt catalysts on β-Ga2O3:Cr3+ support during a catalytic reaction of C2H4 hydrogenation in a contactless and reliable mode, demonstrating their real potentials.
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    32. 32
      Marciniak, L.; Bednarkiewicz, A.; Stefanski, M.; Tomala, R.; Hreniak, D.; Strek, W. Near infrared absorbing near infrared emitting highly-sensitive luminescent nanothermometer based on Nd3+ to Yb3+ energy transfer. Phys. Chem. Chem. Phys. 2015, 17, 24315– 24321,  DOI: 10.1039/c5cp03861h
      32
      Near infrared absorbing near infrared emitting highly-sensitive luminescent nanothermometer based on Nd3+ to Yb3+ energy transfer
      Marciniak, L.; Bednarkiewicz, A.; Stefanski, M.; Tomala, R.; Hreniak, D.; Strek, W.
      Physical Chemistry Chemical Physics (2015), 17 (37), 24315-24321CODEN: PPCPFQ; ISSN:1463-9076. (Royal Society of Chemistry)
      A new type of near IR absorbing near IR emitting (NANE) luminescent nanothermometer is presented, with a phys. background that relies on efficient Nd3+ to Yb3+ energy transfer under 808 nm photoexcitation. The emission spectra of LiLa0.9-xNd0.1YbxP4O12 (x = 0.05, 0.1, 0.2, 0.3, 0.5) nanocrystals were measured in a wide 100-700 °C temp. range. The ratio between the Nd3+ (4F3/2 → 4I9/2) and Yb3+ (2F5/2 → 2F7/2) luminescence bands, and the thermometer sensitivity are strongly dependent on the Yb3+ concn. These phenomenol. relations were discussed in terms of the competition between three phenomena, (a) Nd3+ → Yb3+ phonon assisted energy transfer, (b) Yb3+ → Nd3+ back energy transfer and (c) energy diffusion between Yb3+ ions. The highest sensitivity of the temp. measurement was found for x = 0.5 (LiLa0.4Nd0.1Yb0.5P4O12), which was equal to 4 × 10-3 K-1 at 330 K. In stark contrast to conventional approaches, the proposed phosphate host matrix allows for a high level of doping, and thus, owing to the negligible concn. quenching, the presented luminophores exhibit a high absorption cross section and bright emission. Also, such optical remote thermometers, whose excitation and emission wavelengths are weakly scattered or absorbed and fall into the optical transmission window of the skin, may therefore become a practical soln. for biomedical applications, such as remote control of thermotherapy.
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    33. 33
      Marciniak, L.; Bednarkiewicz, A.; Drabik, J.; Trejgis, K.; Strek, W. Optimization of highly sensitive YAG:Cr3+,Nd3+ nanocrystal-based luminescent thermometer operating in an optical window of biological tissues. Phys. Chem. Chem. Phys. 2017, 19, 7343– 7351,  DOI: 10.1039/c6cp07213e
      33
      Optimization of highly sensitive YAG:Cr3+,Nd3+ nanocrystal-based luminescent thermometer operating in an optical window of biological tissues
      Marciniak, L.; Bednarkiewicz, A.; Drabik, J.; Trejgis, K.; Strek, W.
      Physical Chemistry Chemical Physics (2017), 19 (10), 7343-7351CODEN: PPCPFQ; ISSN:1463-9076. (Royal Society of Chemistry)
      Luminescent and temp. sensitive properties of YAG:Cr3+,Nd3+ nanocrystals were analyzed as a function of temp., nanoparticle size, and excitation wavelength. Due to numerous temp.-dependent phenomena (e.g. Boltzmann population, thermal quenching, and inter-ion energy transfer) occurring in this phosphor, four different thermometer definitions were evaluated with the target to achieve a high sensitivity and broad temp. sensitivity range. Using a Cr3+ to Nd3+ emission intensity ratio, the highest 3.48% K-1 sensitivity was obtained in the physiol. temp. range. However, high sensitivity was compromised by a narrow sensitivity range or vice versa. The knowledge of the excitation and temp. susceptibility mechanisms enabled wise selection of the spectral features found in luminescence spectra for a temp. readout, which enabled the preservation of relatively high temp. sensitivity (>1.2% K-1 max) and extended the temp. sensitivity range from 100 K to 850 K. The size of the nanophosphors had negligible impact on the performance of the studied materials.
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    34. 34
      Gao, Y.; Huang, F.; Lin, H.; Zhou, J.; Xu, J.; Wang, Y. A novel optical thermometry strategy based on diverse thermal response from two intervalence charge transfer states. Adv. Funct. Mater. 2016, 26, 3139– 3145,  DOI: 10.1002/adfm.201505332
      34
      A Novel Optical Thermometry Strategy Based on Diverse Thermal Response from Two Intervalence Charge Transfer States
      Gao, Yan; Huang, Feng; Lin, Hang; Zhou, Jiangcong; Xu, Ju; Wang, Yuansheng
      Advanced Functional Materials (2016), 26 (18), 3139-3145CODEN: AFMDC6; ISSN:1616-301X. (Wiley-VCH Verlag GmbH & Co. KGaA)
      In this work, a novel thermometry strategy based on the diversity in thermal quenching behavior of two intervalence charge transfer (IVCT) states in oxide crystals is proposed, which provides a promising route to design self-referencing optical temp. sensing material with superior temp. sensitivity and signal discriminability. Following this strategy, uniform Tb3+/Pr3+:NaGd(MoO4)2 micro-octahedrons are directionally synthesized. Originated from the diverse thermal responses between Tb3+-Mo6+ and Pr3+-Mo6+ IVCT states, fluorescence intensity ratio of Pr3+ to Tb3+ in this material displays excellent temp. sensing property in a temp. range from 303 to 483 K. The max. abs. and relative sensitivity reaches as high as 0.097 K-1 and 2.05% K-1, resp., being much higher than those of the previously reported optical thermometric materials. Excellent temp. sensing features are also demonstrated in the other Tb3+/Pr3+ codoped oxide crystals having d0 electron configured transition metal ions (Ti4+, V5+, Mo6+, or W6+), such as scheelite NaLu(MoO4)2 and NaLu(WO4)2, and monazite LaVO4 and perovskite La2Ti3O9, evidencing the universal validity of the proposed strategy. This work exploits an effective pathway for developing new optical temp. sensing materials with high performance.
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    35. 35
      Souza, A. S.; Nunes, L. A. O.; Silva, I. G. N.; Oliveira, F. A. M.; da Luz, L. L.; Brito, H. F.; Felinto, M. C. F. C.; Ferreira, R. A. S.; Júnior, S. A.; Carlos, L. D.; Malta, O. L. Highly-sensitive Eu3+ ratiometric thermometers based on excited state absorption with predictable calibration. Nanoscale 2016, 8, 5327– 5333,  DOI: 10.1039/c6nr00158k
      35
      Highly-sensitive Eu3+ ratiometric thermometers based on excited state absorption with predictable calibration
      Souza, Adelmo S.; Nunes, Luiz A. O.; Silva, Ivan G. N.; Oliveira, Fernando A. M.; da Luz, Leonis L.; Brito, Hermi F.; Felinto, Maria C. F. C.; Ferreira, Rute A. S.; Junior, Severino A.; Carlos, Luis D.; Malta, Oscar L.
      Nanoscale (2016), 8 (9), 5327-5333CODEN: NANOHL; ISSN:2040-3372. (Royal Society of Chemistry)
      Temp. measurements ranging from a few degrees to a few hundreds of Kelvin are of great interest in the fields of nanomedicine and nanotechnol. Here, we report a new ratiometric luminescent thermometer using thermally excited state absorption of the Eu3+ ion. The thermometer is based on the simple Eu3+ energy level structure and can operate between 180 and 323 K with a relative sensitivity ranging from 0.7 to 1.7% K-1. The thermometric parameter is defined as the ratio between the emission intensities of the 5D0 → 7F4 transition when the 5D0 emitting level is excited through the 7F2 (physiol. range) or 7F1 (down to 180 K) level. Nano and microcrystals of Y2O3:Eu3+ were chosen as a proof of concept of the operational principles in which both excitation and detection are within the first biol. transparent window. A novel and of paramount importance aspect is that the calibration factor can be calcd. from the Eu3+ emission spectrum avoiding the need for new calibration procedures whenever the thermometer operates in different media.
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    36. 36
      Trejgis, K.; Bednarkiewicz, A.; Marciniak, L. Engineering excited state absorption based nanothermometry for temperature sensing and imaging. Nanoscale 2020, 12, 4667– 4675,  DOI: 10.1039/c9nr09740f
      36
      Engineering excited state absorption based nanothermometry for temperature sensing and imaging
      Trejgis, K.; Bednarkiewicz, A.; Marciniak, L.
      Nanoscale (2020), 12 (7), 4667-4675CODEN: NANOHL; ISSN:2040-3372. (Royal Society of Chemistry)
      Current luminescence nanothermometry exploits either temp. dependent quenching, temp. dependent energy transfer or thermal equil. between two metastable emitting levels, which are quantified to convert spectral features into abs. temp. Although widely used and feasible, these methods are not always reliable enough in terms of flexibility, optimum temp. operating range and often require relatively complicated and expensive detection instrumentation, which may hinder wider adoption of luminescence based nanothermometry in technol. and biomedical sciences. Therefore, not only more sensitive, brighter and robust phosphors are sought, but also novel temp. sensing schemes, which may potentially simplify remote quantification and imaging of temp. In this work, we demonstrate the concept of contactless temp. readout and 2D temp. mapping by using excited state absorption (ESA) process instead of conventional approach based on ground state absorption (GSA) combined with multi-color emission. The anal. of the excitation spectra of LiLaP4O12:Eu3+ nanocryst. powders in a wide temp. range confirmed that the probability of populating higher levels of the ground 7FJ multiplet increases at increased temps. The Single Band Ratiometric Luminescent Thermometry (SBR-LT) opens new possibilities and offers luminescent thermometry at single emission band (5D0 → 7F1) under different excitation lines (7F2,3,4 → 5D0). In consequence, tech. simple, temp. range adjustable, fast and affordable optical temp. imaging can be performed with high sensitivity reaching over 2.17% per °C in an unprecedentedly wide temp. range from -150 to 400°C.
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    37. 37
      McLaurin, E. J.; Bradshaw, L. R.; Gamelin, D. R. Dual-emitting nanoscale temperature sensors. Chem. Mater. 2013, 25, 1283– 1292,  DOI: 10.1021/cm304034s
      37
      Dual-Emitting Nanoscale Temperature Sensors
      McLaurin, Emily J.; Bradshaw, Liam R.; Gamelin, Daniel R.
      Chemistry of Materials (2013), 25 (8), 1283-1292CODEN: CMATEX; ISSN:0897-4756. (American Chemical Society)
      A review. Sol. luminescent temp. probes are promising candidates for optical thermometry and thermog. applications requiring precise, passive, and spatially resolved temp. data. Dual-emitting temp. sensors overcome many of the obstacles encountered with abs. intensity-based luminescence sensors, including optical occlusion, concn. variation, or nonspecificity, by providing internally referenced (ratiometric) signals. The key mechanisms underpinning the dual emission of various nanostructures from recent literature are provided and their relation to optical thermometry discussed.
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    38. 38
      Back, M.; Trave, E.; Ueda, J.; Tanabe, S. Ratiometric optical thermometer based on dual near-infrared emission in Cr3+-doped bismuth-based gallate host. Chem. Mater. 2016, 28, 8347– 8356,  DOI: 10.1021/acs.chemmater.6b03625
      38
      Ratiometric Optical Thermometer Based on Dual Near-Infrared Emission in Cr3+-Doped Bismuth-Based Gallate Host
      Back, Michele; Trave, Enrico; Ueda, Jumpei; Tanabe, Setsuhisa
      Chemistry of Materials (2016), 28 (22), 8347-8356CODEN: CMATEX; ISSN:0897-4756. (American Chemical Society)
      Detailed spectroscopic anal. of the electronic configuration of Cr3+ in Bi2Ga4O9 is reported. The material exhibits unique luminescent properties arising from the crystal field experienced by Cr3+, with simultaneous strong sharp and broadband near-IR emissions from the 2E and 4T2 excited states, in a wide range of temp. The system displays dual near-IR emission characterized by a remarkable thermal sensitivity over the whole explored range of temps., reaching a value of 0.7%·K-1 in the physiol. range. Also, the possibility to absorb and emit in the 1st biol. window, allows 1 to consider the system as a new promising candidate for ratiometric fluorescent thermal sensing in biotechnol. applications.
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    39. 39
      Casagrande, E.; Back, M.; Cristofori, D.; Ueda, J.; Tanabe, S.; Palazzolo, S.; Rizzolio, F.; Canzonieri, V.; Trave, E.; Riello, P. Upconversion-mediated Boltzmann thermometry in double-layered Bi2SiO5:Yb3+,Tm3+@SiO2 hollow nanoparticles sensors. J. Mater. Chem. C 2020, 8, 7828– 7836,  DOI: 10.1039/d0tc01457e
      39
      Upconversion-mediated Boltzmann thermometry in double-layered Bi2SiO5:Yb3+,Tm3+@SiO2 hollow nanoparticles
      Casagrande, Elisa; Back, Michele; Cristofori, Davide; Ueda, Jumpei; Tanabe, Setsuhisa; Palazzolo, Stefano; Rizzolio, Flavio; Canzonieri, Vincenzo; Trave, Enrico; Riello, Pietro
      Journal of Materials Chemistry C: Materials for Optical and Electronic Devices (2020), 8 (23), 7828-7836CODEN: JMCCCX; ISSN:2050-7534. (Royal Society of Chemistry)
      Ratiometric optical thermometry is one of the most promising techniques for contactless temp. sensing. However, despite the efforts devoted in the last decades, the development of nanothermometers characterized by high reliability along with suitable sensitivity (Sr > 1% K-1) and thermal resoln. (δT < 0.5 K) in the physiol. temp. range is still a crit. challenge in the biol. field. Here, we propose uniform Yb,Tm co-doped cryst. Bi2SiO5@SiO2 hollow upconverting nanoparticles as red-NIR emitting nanophosphors for ratiometric optical thermometry. The synthetic procedure leads to double-layered Bi2SiO5:Yb,Tm@SiO2 hollow nanoparticles. The thermometric performances are investigated in a wide temp. range (80-800 K) demonstrating the reliability of the thermometer based on the emission ratio between the 1G4 → 3F4 (~ 650 nm) and 3F2,3 → 3H6 (~ 700 nm) transitions. Despite the impossibility to be in thermal equil. due to the large energy gap between 1G4 and 3F2,3 excited states, their relative populations are demonstrated to follow the Boltzmann distribution, reflecting, through the upconversion processes, the thermalization between the 3F2,3 and 3H4 excited states. Consequently, the system features high thermal sensitivity (Sr = 1.95% K-1 at 300 K) and excellent thermal resoln. (0.28 K at 300 K) for a highly reliable system following the Boltzmann-distribution. In addn., the superior performances of the investigated system in comparison with other NIR-to-NIR thermometers such as Nd3+-based ones and the biocompatibility of the NPs prove its potential in the physiol. temp. range.
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    40. 40
      Suta, M.; Meijerink, A. A theoretical framework for ratiometric single ion luminescent thermometers─Thermodynamic and kinetic guidelines for optimized performance. Adv. Theory Simul. 2020, 3, 2000176,  DOI: 10.1002/adts.202000176
      40
      A Theoretical Framework for Ratiometric Single Ion Luminescent Thermometers-Thermodynamic and Kinetic Guidelines for Optimized Performance
      Suta, Markus; Meijerink, Andries
      Advanced Theory and Simulations (2020), 3 (12), 2000176CODEN: ATSDCW; ISSN:2513-0390. (Wiley-VCH Verlag GmbH & Co. KGaA)
      Luminescence (nano)thermometry is an increasingly important field for remote temp. sensing with high spatial resoln. Most typically, ratiometric sensing of the luminescence emission intensities of two thermally coupled emissive states based on a Boltzmann equil. is used to detect the local temp. Dependent on the temp. range and preferred spectral window, various choices for potential candidates appear possible. Despite extensive exptl. research in the field, a universal theory covering the basics of luminescence thermometry is virtually nonexistent. In this manuscript, a general theor. framework of single ion luminescent thermometers is presented that offers simple, user-friendly guidelines for both the choice of an appropriate emitter and resp. embedding host material for optimum temp. sensing. The results show that the optimum performance (thermal response and sensitivity) around T0 is realized for an energy gap ΔE21 between thermally coupled levels between 2kBT0 and 3.41kBT0. Anal. of the temp.-dependent excited state kinetics shows that host lattices in which ΔE21 can be bridged by one or two phonons are preferred over hosts in which higher order phonon processes are required. Such a framework is relevant for both a fundamental understanding of luminescent thermometers but also the targeted design of novel and superior luminescent (nano)thermometers.
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    41. 41
      Yu, D.; Li, H.; Zhang, D.; Zhang, Q.; Meijerink, A.; Suta, M. One ion to catch them all: Targeted high-precision Boltzmann thermometry over a wide temperature range with Gd3+. Light Sci. Appl. 2021, 10, 236,  DOI: 10.1038/s41377-021-00677-5
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      One ion to catch them all: Targeted high-precision Boltzmann thermometry over a wide temperature range with Gd3+
      Yu, Dechao; Li, Huaiyong; Zhang, Dawei; Zhang, Qinyuan; Meijerink, Andries; Suta, Markus
      Light: Science & Applications (2021), 10 (1), 236CODEN: LSAIAZ; ISSN:2047-7538. (Nature Research)
      Abstr.: Ratiometric luminescence thermometry with trivalent lanthanide ions and their 4fn energy levels is an emerging technique for non-invasive remote temp. sensing with high spatial and temporal resoln. Conventional ratiometric luminescence thermometry often relies on thermal coupling between two closely lying energy levels governed by Boltzmanns law. Despite its simplicity, Boltzmann thermometry with two excited levels allows precise temp. sensing, but only within a limited temp. range. While low temps. slow down the nonradiative transitions required to generate a measurable population in the higher excitation level, temps. that are too high favor equalized populations of the two excited levels, at the expense of low relative thermal sensitivity. In this work, we extend the concept of Boltzmann thermometry to more than two excited levels and provide quant. guidelines that link the choice of energy gaps between multiple excited states to the performance in different temp. windows. By this approach, it is possible to retain the high relative sensitivity and precision of the temp. measurement over a wide temp. range within the same system. We demonstrate this concept using YAl3(BO3)4 (YAB):Pr3+, Gd3+ with an excited 6PJ crystal field and spin-orbit split levels of Gd3+ in the UV range to avoid a thermal black body background even at the highest temps. This phosphor is easily excitable with inexpensive and powerful blue LEDs at 450 nm. Zero-background luminescence thermometry is realized by using blue-to-UV energy transfer upconversion with the Pr3+-Gd3+ couple upon excitation in the visible range. This method allows us to cover a temp. window between 30 and 800 K.
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    42. 42
      Sammes, N. M.; Tompsett, G. A.; Näfe, H.; Aldinger, F. Bismuth based oxide electrolytes - Sructure and ionic conductivity. J. Eur. Ceram. Soc. 1999, 19, 1801– 1826,  DOI: 10.1016/s0955-2219(99)00009-6
      42
      Bismuth based oxide electrolytes-structure and ionic conductivity
      Sammes, N. M.; Tompsett, G. A.; Nafe, H.; Aldinger, F.
      Journal of the European Ceramic Society (1999), 19 (10), 1801-1826CODEN: JECSER; ISSN:0955-2219. (Elsevier Science Ltd.)
      Bismuth oxide systems exhibit high oxide ion cond. and have been proposed as good electrolyte materials for applications such as solid oxide fuel cells and oxygen sensors. However, due to their instability under conditions of low oxygen partial pressures there has been difficulty in developing these materials as alternative electrolyte materials compared to the state-of-the-art cubic stabilized zirconia electrolyte. Bismuth oxide and doped bismuth oxide systems exhibit a complex array of structures and properties depending upon the dopant concn., temp. and atm. In this paper we comprehensively review the structures, thermal expansion, phase transitions, elec. cond. and stability of bismuth oxide and doped bismuth oxide systems.
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    43. 43
      Drache, M.; Roussel, P.; Wignacourt, J.-P. Structures of oxide mobility in Bi-Ln-O materials: Heritage of Bi2O3. Chem. Rev. 2007, 107, 80– 96,  DOI: 10.1021/cr050977s
      43
      Structures and oxide mobility in Bi-Ln-O materials. Heritage of Bi2O3
      Drache, Michel; Roussel, Pascal; Wignacourt, Jean-Pierre
      Chemical Reviews (Washington, DC, United States) (2007), 107 (1), 80-96CODEN: CHREAY; ISSN:0009-2665. (American Chemical Society)
      A review is given on the crystal structures of the Ln-Bi-based oxides, which are related to the structure of the Bi2O3 polymorphs. First, the 6 polymorphs of Bi2O3 are presented, and their structural relationships are discussed. Then, the stable and metastable phases of LnxBi1-xO1.5 are described. Further phases being discussed here are: (i) the rhombohedral LnxBi1-xO1.5 phases of the Bi-Sr-O type with Ln = La-Er, Y, (ii) the orthorhombic Ln7Bi17O36-type phases with Ln = Tm-Lu, (iii) the ordered cubic Ln3Bi5O12-type phases with Ln = Sm-Yb, (iv) the triclinic LnBiO3-type phases with Ln = Dy-Lu, Y, and (v) the LnxBi1-xO1.5 phases with x ≥ 0.5 and Ln = La-Ho, Y. The synthesis conditions and the structural features are tabulated. The phase diagrams of LnxBi1-xO1.5 (x = 0-80%) are given, and the behavior of the elec. cond. is discussed.
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    44. 44
      Malavasi, L. C. A. J.; Fisher, M. S.; Islam, M. S. Oxide-ion proton conducting electrolyte materials for clean energy applications: structural and mechanistic features. Chem. Soc. Rev. 2010, 39, 4370– 4387,  DOI: 10.1039/b915141a
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      Oxide-ion and proton conducting electrolyte materials for clean energy applications: structural and mechanistic features
      Malavasi, Lorenzo; Fisher, Craig A. J.; Islam, M. Saiful
      Chemical Society Reviews (2010), 39 (11), 4370-4387CODEN: CSRVBR; ISSN:0306-0012. (Royal Society of Chemistry)
      This crit. review presents an overview of the various classes of oxide materials exhibiting fast oxide-ion or proton cond. for use as solid electrolytes in clean energy applications such as solid oxide fuel cells. Emphasis is placed on the relationship between structural and mechanistic features of the cryst. materials and their ion conduction properties. After describing well-established classes such as fluorite- and perovskite-based oxides, new materials and structure-types are presented. These include a variety of molybdate, gallate, apatite silicate/germanate and niobate systems, many of which contain flexible structural networks, and exhibit different defect properties and transport mechanisms to the conventional materials. It is concluded that the rich chem. of these important systems provides diverse possibilities for developing superior ionic conductors for use as solid electrolytes in fuel cells and related applications. Tn most cases, a greater at.-level understanding of the structures, defects, and conduction mechanisms is achieved through a combination of exptl. and computational techniques.
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    45. 45
      Walsh, A.; Watson, G. W.; Payne, D. J.; Edgell, R. G.; Guo, J.; Glans, P. A.; Learmonth, T.; Smith, K. E. Electronic structure of the α and δ phase of Bi2O3: A combined ab initio and x-ray spectroscopy study. Phys. Rev. B: Condens. Matter Mater. Phys. 2006, 73, 235104,  DOI: 10.1103/physrevb.73.235104
      45
      Electronic structure of the α and δ phases of Bi2O3: A combined ab initio and x-ray spectroscopy study
      Walsh, Aron; Watson, Graeme W.; Payne, David J.; Edgell, Russell G.; Guo, Jinghua; Glans, Per-Anders; Learmonth, Timothy; Smith, Kevin E.
      Physical Review B: Condensed Matter and Materials Physics (2006), 73 (23), 235104/1-235104/13CODEN: PRBMDO; ISSN:1098-0121. (American Physical Society)
      α-Bi2O3 is the thermodynamically stable phase of Bi2O3 at room temp. The authors have performed a theor. and exptl. study of its electronic structure using a combination of gradient cor. d. functional theory (DFT), along with x-ray photoemission and O-K shell x-ray absorption and emission spectroscopies. The authors examine the nature of bonding in α-Bi2O3 and in particular explore the nature of the stereochem. active Bi electron lone pair. The Bi 6s states are concd. at the bottom of the valence band but the states contributing to the lone pair on Bi are derived from the top of the valence band. Mixing between O 2p and Bi 6s states is crucial in producing the asym. d. on Bi. The role of the lone pair in the fast ion conductor δ-Bi2O3 is also studied, through calcn. of the electronic structure with <100>, <110>, and <111> alignment of O vacancies. Alignment of the vacancies along <100> results in the most energetically favorable configuration of the δ phase, contrary to previous force field calcns. and electrostatic arguments which favor the <111> alignment.
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    46. 46
      Walsh, A.; Watson, G. W. Polymorphism in Bismuth Stannate: A First-Principles Study. Chem. Mater. 2007, 19, 5158– 5164,  DOI: 10.1021/cm0714279
      46
      Polymorphism in Bismuth Stannate: A First-Principles Study
      Walsh, Aron; Watson, Graeme W.
      Chemistry of Materials (2007), 19 (21), 5158-5164CODEN: CMATEX; ISSN:0897-4756. (American Chemical Society)
      From the wide range of SnIV-based pyrochlores, Bi2Sn2O7 stands out as a material that deviates from the std. cubic-lattice symmetry. At low temps., Bi2Sn2O7 adopts a distorted monoclinic √2 × √2 × 2 expansion of the pyrochlore structure (α-phase) and only favors the cubic lattice (γ-phase) >900 K. The authors calc. and examine the electronic structure of both the α- and γ-phases of Bi2Sn2O7 and compare them to the results of two regular pyrochlore materials, La2Sn2O7 and Y2Sn2O7. The authors' anal. highlights the importance of covalent interactions between the electronic states of the metal with O 2p in Bi2Sn2O7, which are not present in the other oxides. The formation of an asym. electron d. on Bi is obsd. as the driving force behind the distorted geometry favored by Bi2Sn2O7.
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      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD2sXhtV2hsbrI&md5=c72d7a8f1c2f80f597848e9f86729d95
    47. 47
      Tauc, J.; Grigorovici, R.; Vancu, A. Optical properties and electronic structure of amorphous germanium. Phys. Status Solidi B 1966, 15, 627– 637,  DOI: 10.1002/pssb.19660150224
      47
      Optical properties and electronic structure of amorphous germanium
      Tauc, J.; Grigorovici, R.; Vancu, A.
      Physica Status Solidi (1966), 15 (2), 627-37CODEN: PHSSAK; ISSN:0031-8957.
      The optical consts. of amorphous Ge are detd. for photon energies 0.08-1.6 ev. From 0.08 to 0.5 ev., the absorption is due to k-conserving transitions of holes between the valence bands as in p-type crystals; the spin-orbit splitting is 0.20 and 0.21 ev. in nonannealed and annealed samples, resp. The effective masses of the holes in the 3 bands are 0.49 m (0.43 m), 0.04 m, and 0.08 m. An absorption band is observed below the main absorption edge (at 300°K. the max. of this band is at 0.86 ev.); the absorption in this band increases with increasing temp. This band is due to excitons bound to neutral acceptors, and these are presumably the same ones that play a decisive role in the transport properties, which are considered to be assocd. with vacancies. The absorption edge has the form ω2ε2 ∼ (ℏω - Eg)2 (Eg = 0.88 ev. at 300°K.). This suggests that the optical transitions conserve energy but not k vector, and that the ds. of states near the band extrema have the same energy dependence as in cryst. Ge. A simple theory describing this situation is proposed, and comparison of it with the exptl. results leads to an estimate of the localization of the conduction-band wave functions. 24 references.
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    48. 48
      Kubelka, P.; Munk, F. Ein Beitrag Zur Optik Der Farbanstriche. Z. Tech. Phys. 1931, 12, 593– 601
      There is no corresponding record for this reference.
    49. 49
      Cheng, H.; Huang, B.; Lu, J.; Wang, Z.; Xu, B.; Qin, X.; Zhang, X.; Dai, Y. Synergistic effect of crystal and electronic structures on the visible-light-driven photocatalytic performances of Bi2O3 polymorphs. Phys. Chem. Chem. Phys. 2010, 12, 15468– 15475,  DOI: 10.1039/c0cp01189d
      49
      Synergistic effect of crystal and electronic structures on the visible-light-driven photocatalytic performances of Bi2O3 polymorphs
      Cheng, Hefeng; Huang, Baibiao; Lu, Jibao; Wang, Zeyan; Xu, Bing; Qin, Xiaoyan; Zhang, Xiaoyang; Dai, Ying
      Physical Chemistry Chemical Physics (2010), 12 (47), 15468-15475CODEN: PPCPFQ; ISSN:1463-9076. (Royal Society of Chemistry)
      Three polymorphs of Bi2O3 were selectively synthesized via soln.-based methods. The phase structures of the as-prepd. samples were confirmed by x-ray powder diffraction (XRD) and XPS. UV-vis diffuse reflectance spectroscopy was employed to study the optical properties of Bi2O3 polymorphs, and the band gaps were estd. to be 2.80, 2.48, and 3.01 eV for α-Bi2O3, β-Bi2O3, and δ-Bi2O3, resp. The photocatalytic performances of the oxides were investigated by decompg. Methyl orange and 4-chlorophenol under visible irradn. at room temp. It was obsd. that β-Bi2O3 displayed much higher photocatalytic performance than N-doped P25. Among the three polymorphs of Bi2O3, the photocatalytic activities followed the order: β-Bi2O3 > α-Bi2O3 > δ-Bi2O3, which was in good accordance with the photoluminescence spectra measurement results. The synergistic effect of the crystal and electronic structures on the photocatalytic performances of Bi2O3 polymorphs was investigated. The much better photocatalytic activity of β-Bi2O3 was considered to be closely related to its smaller band gap, higher crystallinity and unique tunnel structure.
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    50. 50
      Lu, Y.; Zhao, J.; Zhao, Y.; Song, Z.; Huang, F.; Gao, N.; Li, Y.; Li, Y. Induced aqueous synthesis of metastable β-Bi2O3 microcrystals for visible-light photocatalyst study. Cryst. Growth Des. 2015, 15, 1031– 1042,  DOI: 10.1021/cg500792v
      50
      Induced Aqueous Synthesis of Metastable β-Bi2O3 Microcrystals for Visible-Light Photocatalyst Study
      Lu, Yan; Zhao, Yan; Zhao, Jingzhe; Song, Yuehong; Huang, Zhifang; Gao, Fangfang; Li, Na; Li, Yawen
      Crystal Growth & Design (2015), 15 (3), 1031-1042CODEN: CGDEFU; ISSN:1528-7483. (American Chemical Society)
      Metastable β-Bi2O3 microcrystals were fast prepd. from Bi(NO3)3 by an aq. crystn. strategy without further calcination or other complex treatment. Powder X-ray diffraction, field emission SEM, and optical microscopy were used to characterize the obtained samples and reveal the evolution process of β-Bi2O3 crystals. It was found in the expts. that the introduction of cetyltrimethylammonium bromide (actually Br- ions) facilitated the formation of β-Bi2O3 crystals. Photocatalytic activities of metastable β-Bi2O3 samples under visible-light irradn. were investigated by taking the degrdn. of rhodamine B (RhB) as a probe reaction. The as-prepd. β-Bi2O3 crystals showed excellent photocatalytic efficiency of up to 77.9% (total removal 97.2%) in 2 h of irradn. under visible light; the efficiency underwent no noticeable redn. for four cycles of degrdn. A minor amt. of BiOCl crystallites appearing at the surface of β-Bi2O3 crystals during degrdn. process facilitated the photocatalytic properties of the catalysts. A combined photocatalytic mechanism of direct photoexcitation and indirect dye photosensitization was proposed in our work for RhB degrdn. under visible light.
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    51. 51
      Dorenbos, P. Determining binding energies of valence-band electrons in insulators and semiconductors via lanthanide spectroscopy. Phys. Rev. B: Condens. Matter Mater. Phys. 2013, 87, 035118,  DOI: 10.1103/physrevb.87.035118
      51
      Determining binding energies of valence-band electrons in insulators and semiconductors via lanthanide spectroscopy
      Dorenbos, Pieter
      Physical Review B: Condensed Matter and Materials Physics (2013), 87 (3), 035118/1-035118/8CODEN: PRBMDO; ISSN:1098-0121. (American Physical Society)
      Models and methods to det. the abs. binding energy of 4f-shell electrons in lanthanide dopants will be combined with data on the energy of electron transfer from the valence band to a lanthanide dopant. This work will show- that it provides a powerful tool to det. the abs. binding energy of valence band electrons throughout the entire family of insulator and semiconductor compds. The tool will be applied to 28 fluoride, oxide, and nitride compds. providing the work function and electron affinity together with the location of the energy levels of all divalent and all trivalent lanthanide dopants with an accuracy that surpasses that of traditional methods like photoelectron spectroscopy. The 28 compds. were selected to demonstrate how work function and electron affinity change with compn. and structure, and how electronic structure affects the optical properties of the lanthanide dopants. Data covering more than 1000 different halide (F, Cl, Br, I), chalcogenide (O, S, Se), and nitride compds. are available in the archival literature enabling us to routinely establish work function and electron affinity for this much wider collection of compds.
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    52. 52
      Dorenbos, P. Electronic structure of Bi-activated luminescent compounds and pure bismuth photocatalytic compounds. ECS J. Solid State Sci. Technol. 2021, 10, 086002,  DOI: 10.1149/2162-8777/ac19c6
      There is no corresponding record for this reference.
    53. 53
      Back, M.; Ueda, J.; Ambrosi, E.; Cassandro, L.; Cristofori, D.; Ottini, R.; Riello, P.; Sponchia, G.; Asami, K.; Tanabe, S.; Trave, E. Lanthanide-doped bismuth-based fluoride nanocrystalline particles: Formation, spectroscopic investigation, and chemical stability. Chem. Mater. 2019, 31, 8504– 8514,  DOI: 10.1021/acs.chemmater.9b03164
      53
      Lanthanide-Doped Bismuth-Based Fluoride Nanocrystalline Particles: Formation, Spectroscopic Investigation, and Chemical Stability
      Back, Michele; Ueda, Jumpei; Ambrosi, Emmanuele; Cassandro, Lorenzo; Cristofori, Davide; Ottini, Riccardo; Riello, Pietro; Sponchia, Gabriele; Asami, Kazuki; Tanabe, Setsuhisa; Trave, Enrico
      Chemistry of Materials (2019), 31 (20), 8504-8514CODEN: CMATEX; ISSN:0897-4756. (American Chemical Society)
      Bismuth-based fluoride nanocryst. particles have recently attracted much attention as hosts for luminescent ions such as lanthanides (Ln) being proposed for lighting devices and biol. applications. However, a comprehensive investigation on the chem. properties of this family of materials, the growth of the nanoparticles, and information about the chem. and thermal stabilities are crit. to assess the real potential of nanosystems. In this view, a combined exptl. and theor. approach is employed to investigate the cryst. and electronic structure of BiF3 and NaBiF4. A detailed spectroscopic investigation allows us to measure the exciton peaks of these fluoride compds. for the first time and to design the vacuum referred binding energy level diagram of the lanthanide-doped fluorides with respect to the valence and conduction bands of the hosts in comparison with conventional fluorides. In addn., temp. and water effects on the chem. stability of NaBiF4 were addressed, evidencing detrimental limitations and envisaging possible solns. in view of biol. applications.
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    54. 54
      Hou, J.; Yang, C.; Wang, Z.; Zhou, W.; Jiao, S.; Zhu, H. In situ synthesis of α-β phase heterojunction on Bi2O3 nanowires with exceptional visible-light photocatalytic performance. Appl. Catal. 2013, 142-143, 504– 511,  DOI: 10.1016/j.apcatb.2013.05.050
      54
      In situ synthesis of α-β phase heterojunction on Bi2O3 nanowires with exceptional visible-light photocatalytic performance
      Hou, Jungang; Yang, Chao; Wang, Zheng; Zhou, Weilin; Jiao, Shuqiang; Zhu, Hongmin
      Applied Catalysis, B: Environmental (2013), 142-143 (), 504-511CODEN: ACBEE3; ISSN:0926-3373. (Elsevier B.V.)
      Visible-light-responsive α-β phase heterojunction on Bi2O3 nanowire photocatalysts were prepd. via a facile in situ hydrothermal process in assistance with the post-heat treatment route. The as-prepd. samples were characterized by x-ray diffraction (XRD), electron microscope (EM), Brunauer-Emmett-Teller anal. (BET), XPS, and UV-visible diffuse reflectance absorption spectra (UV-vis). XRD patterns revealed that the α-β phase heterojunction over Bi2O3 composites with the monoclinic α-Bi2O3 and the tetragonal β-Bi2O3 structure were obtained and the relative ratios between α-Bi2O3 and β-Bi2O3 can readily be tailored by the control of the reaction temp. Within the hydrothermal temp. range, the morphol. of as-prepd. samples transformed progressively from two-dimensional β-Bi2O3 sheets to the α-/β-Bi2O3 nanowires junction. The exceptional photocatalytic performance of α-/β-Bi2O3 heterojunction for the degrdn. of cationic Rhodamine B and anionic Methyl orange under visible-light irradn. is superior over that of β-Bi2O3 sheets, which is ascribed to the efficient charge sepn. and transfer across the α-β phase junction. The phase-junction approach will open new avenues for the development of efficient photocatalysts for environmental remediation and energy conversion.
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    55. 55
      Gandhi, A. C.; Lai, C.-Y.; Wu, K.-T.; Ramacharyulu, P. V. R. K.; Koli, V. B.; Cheng, C.-L.; Ke, S.-C.; Wu, S.-Y. Phase transformation and room temperature stabilization of various Bi2O3 nano-polymorphs: effect of oxygen-vacancy defects and reduced surface energy due to adsorbed carbon species. Nanoscale 2020, 12, 24119– 24137,  DOI: 10.1039/d0nr06552h
      55
      Phase transformation and room temperature stabilization of various Bi2O3 nano-polymorphs: effect of oxygen-vacancy defects and reduced surface energy due to adsorbed carbon species
      Gandhi, Ashish Chhaganlal; Lai, Chi-Yuan; Wu, Kuan-Ting; Ramacharyulu, P. V. R. K.; Koli, Valmiki B.; Cheng, Chia-Liang; Ke, Shyue-Chu; Wu, Sheng Yun
      Nanoscale (2020), 12 (47), 24119-24137CODEN: NANOHL; ISSN:2040-3372. (Royal Society of Chemistry)
      We report the grain growth from the nanoscale to microscale and a transformation sequence from Bi → Bi2O3 with the increase of annealing temp. The room temp. (RT) stabilization of Bi2O3 nanoparticles (NPs) was attributed to the effect of reduced surface energy due to adsorbed carbon species, and oxygen vacancy defects may have played a significant role in the RT stabilization of Bi2O3 NPs. An enhanced red emission band was evident from all the samples attributed to oxygen-vacancy defects formed during the growth process in contrast with the obsd. white emission band from the air annealed Bi ingots. Based on our exptl. findings, the air annealing induced oxidn. of Bi NPs and transformation mechanism within various Bi2O3 nano-polymorphs are presented. The outcome of this study suggests that oxygen vacancy defects at the nanoscale play a significant role in both structural stabilization and phase transformation within various Bi2O3 nano-polymorphs, which is significant from theor. consideration.
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    56. 56
      Hemmer, E.; Benayas, A.; Légaré, F.; Vetrone, F. Exploiting the biological windows: Current perspectives on fluorescent bioprobes emitting above 1000 nm. Nanoscale 2016, 1, 168– 184,  DOI: 10.1039/c5nh00073d
      56
      Exploiting the biological windows: current perspectives on fluorescent bioprobes emitting above 1000 nm
      Hemmer, Eva; Benayas, Antonio; Legare, Francois; Vetrone, Fiorenzo
      Nanoscale Horizons (2016), 1 (3), 168-184CODEN: NHAOAW; ISSN:2055-6764. (Royal Society of Chemistry)
      With the goal of developing more accurate, efficient, non-invasive and fast diagnostic tools, the use of near-IR (NIR) light in the range of the second and third biol. windows (NIR-II: 1000-1350 nm, NIR-III: 1550-1870 nm) is growing remarkably as it provides the advantages of deeper penetration depth into biol. tissues, better image contrast, reduced phototoxicity and photobleaching. Consequently, NIR-based bioimaging has become a quickly emerging field and manifold new NIR-emitting bioprobes have been reported. Classes of materials suggested as potential probes for NIR-to-NIR bioimaging (using NIR light for the excitation and emission) are quite diverse. These include rare-earth based nanoparticles, Group-IV nanostructures (single-walled carbon nanotubes, carbon nanoparticles and more recently Si- or Ge-based nanostructures) as well as Ag, In and Pb chalcogenide quantum dots. This review summarizes and discusses current trends, material merits, and latest developments in NIR-to-NIR bioimaging taking advantage of the region above 1000 nm (i.e. the second and third biol. windows). Further consideration will be given to upcoming probe materials emitting in the NIR-I region (700-950 nm), thus do not possess emissions in these two windows, but have high expectations. Overall, the focus is placed on recent discussions concerning the optimal choice of excitation and emission wavelengths for deep-tissue high-resoln. optical bioimaging and on fluorescent bioprobes that have successfully been implemented in in vitro and in vivo applications.
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    57. 57
      Benayas, A.; del Rosal, B.; Pérez-Delgado, A.; Santacruz-Gómez, K.; Jaque, D.; Hirata, G. A.; Vetrone, F. Nd YAG near-infrared luminescent nanothermometers. Adv. Opt. Mater. 2015, 3, 687– 694,  DOI: 10.1002/adom.201400484
      57
      Nd:YAG Near-Infrared Luminescent Nanothermometers
      Benayas, Antonio; del Rosal, Blanca; Perez-Delgado, Alberto; Santacruz-Gomez, Karla; Jaque, Daniel; Hirata, Gustavo Alonso; Vetrone, Fiorenzo
      Advanced Optical Materials (2015), 3 (5), 687-694CODEN: AOMDAX; ISSN:2195-1071. (Wiley-VCH Verlag GmbH & Co. KGaA)
      In this work, the thermal sensing capability of Nd3+-doped Y3Al5O12 nanoparticles fabricated by combustion synthesis is reported. Under excitation at 808 nm, the relative intensity of the two spectrally isolated luminescence peaks located at around 940 nm (corresponding to a 4F3/2 →4I9/2 transition of the Nd3+ ions) is found to be markedly temp.-dependent allowing for ratiometric luminescence nanothermometry. The potential use of neodymium-doped yttrium aluminum garnet nanoparticles in nanothermometry has been successfully tested in a variety of systems including integrated microelectronics, optofluidic devices, and subtissue ex vivo expts.
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    58. 58
      Skripka, A.; Morinvil, A.; Matulionyte, M.; Cheng, T.; Vetrone, F. Advancing neodymium single-band nanothermometry. Nanoscale 2019, 11, 11322– 11330,  DOI: 10.1039/c9nr02801c
      58
      Advancing neodymium single-band nanothermometry
      Skripka, A.; Morinvil, A.; Matulionyte, M.; Cheng, T.; Vetrone, F.
      Nanoscale (2019), 11 (23), 11322-11330CODEN: NANOHL; ISSN:2040-3372. (Royal Society of Chemistry)
      Near-IR (NIR) emitting contrast agents with integrated optical temp. sensing are highly desirable for a variety of biomedical applications, particularly when s.c. target visualization and measurement of its thermodn. properties are required. To that end, the possibility of using Nd3+ doped LiLuF4 rare-earth nanoparticles (RENPs) as NIR photoluminescent nanothermometers is explored. These RENPs are relatively small, have narrow size distribution, and can easily be core/shell engineered - all combined, these features meet the requirements of biol. relevant and multifunctional nanoprobes. The LiLuF4 host allows to observe the fine Stark structure of the 4F3/2 → 4I9/2, 4I11/2, and 4I13/2 optical transitions, each of which can then be used for single-band NIR nanothermometry. The thermometric parameter defined for the most intense Nd 3+ emission around 1050 nm, shows high temp. sensitivity (∼0.49% ° C -1), and low temp. uncertainty (0.3°C) as compared to the thermometric parameters defined for the 880 and 1320 nm Nd 3+ emissions. Addnl., transient temp. measurements through tissue show that these RENPs can be used to assess fast temp. changes at a tissue depth of 3 mm, while slower temp. changes can be measured at even greater depths. Nd 3+ doped LiLuF4 RENPs represent a significant improvement for Nd 3+ based single-band photoluminescence nanothermometry, with the possibility of its integration within more sophisticated multifunctional theranostic nanostructures.
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    59. 59
      Suta, M.; Antić, Z.; Đord̵ević, V.; Kuzman, S.; Dramićanin, M. D.; Meijerink, A. Making Nd3+ a sensitive luminescent thermometer for physiological temperatures – An account of pitfalls in Boltzmann thermometry. Nanomaterials 2020, 10, 543,  DOI: 10.3390/nano10030543
      59
      Making Nd3+ a sensitive luminescent thermometer for physiological temperatures-an account of pitfalls in boltzmann thermometry
      Suta, Markus; Antic, Zeljka; Dordevic, Vesna; Kuzman, Sanja; Dramicanin, Miroslav D.; Meijerink, Andries
      Nanomaterials (2020), 10 (3), 543CODEN: NANOKO; ISSN:2079-4991. (MDPI AG)
      Herein, we demonstrate and discuss various pitfalls that can occur in Boltzmann thermometry if this particular LIR is used for physiol. temp. sensing. Both microcryst., dil. (0.1%) Nd3+-doped LaPO4 and LaPO4: x% Nd3+ (x = 2, 5, 10, 25, 100) nanocrystals serve as an illustrative example. Besides structural and optical characterization of those luminescent thermometers, the impact and consequences of the Nd3+ concn. on their luminescence and performance as Boltzmann-based thermometers are analyzed. At higher Nd3+ concns., cross-relaxation processes enhance the decay rates of the 4F3/2 and 4F5/2 levels making the decay faster than the equilibration rates between the levels. It is shown that the onset of the useful temp. sensing range shifts to higher temps., even above ~ 450 K for Nd concns. over 5%. A microscopic explanation for pitfalls in Boltzmann thermometry with Nd3+ is finally given and guidelines for the usability of this lanthanide ion in the field of physiol. temp. sensing are elaborated. Insight in competition between thermal coupling through non-radiative transitions and population decay through cross-relaxation of the 4F5/2 and 4F3/2 spin-orbit levels of Nd3+ makes it possible to tailor the thermometric performance of Nd3+ to enable physiol. temp. sensing.
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    60. 60
      Back, M.; Casagrande, E.; Trave, E.; Cristofori, D.; Ambrosi, E.; Dallo, F.; Roman, M.; Ueda, J.; Xu, J.; Tanabe, S.; Benedetti, A.; Riello, P. Confined-melting-assisted synthesis of bismuth silicate glass-ceramic nanoparticles: Formation and optical thermometry investigation. ACS Appl. Mater. Interfaces 2020, 12, 55195– 55204,  DOI: 10.1021/acsami.0c17897
      60
      Confined-Melting-Assisted Synthesis of Bismuth Silicate Glass-Ceramic Nanoparticles: Formation and Optical Thermometry Investigation
      Back, Michele; Casagrande, Elisa; Trave, Enrico; Cristofori, Davide; Ambrosi, Emmanuele; Dallo, Federico; Roman, Marco; Ueda, Jumpei; Xu, Jian; Tanabe, Setsuhisa; Benedetti, Alvise; Riello, Pietro
      ACS Applied Materials & Interfaces (2020), 12 (49), 55195-55204CODEN: AAMICK; ISSN:1944-8244. (American Chemical Society)
      Bismuth-based (nano)materials have been attracting increasing interest due to appealing properties such as high refractive indexes, intrinsic opacity, and structural distortions due to the stereochem. of 6s2 lone pair electrons of Bi3+. However, the control over specific phases and strategies able to stabilize uniform bismuth-based (nano)materials is still a challenge. In this study, we employed the ability of bismuth to lower the m.p. of silica to introduce a new synthetic approach able to confine the growth of bismuth-oxide-based materials into nanostructures. Combining in situ temp.-dependent synchrotron radiation X-ray powder diffraction (XRPD) with high-resoln. transmission electron microscopy (HR-TEM) analyses, we demonstrate the evolution of a confined Bi2O3-SiO2 nanosystem from Bi2SiO5 to Bi4Si3O12 through a melting process. The silica shell acts as both a nanoreactor and a silicon source for the stabilization of bismuth silicate glass-ceramic nanocrystals keeping the original spherical shape. The exciton peak of Bi2SiO5 is measured for the first time allowing the estn. of its real energy gap. Moreover, based on a detailed spectroscopic investigation, we discuss the potential and the limitations of Nd3+-activated bismuth silicate systems as ratiometric thermometers. The synthetic strategy introduced here could be further explored to stabilize other bismuth-oxide-based materials, opening the way toward the growth of well-defined glass-ceramic nanoparticles.
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    61. 61
      Witt, K. Understanding the CIE System. In Colorimetry; Schanda, J. C., Ed.; Wiley, 2007; Vol. 4.
      There is no corresponding record for this reference.
    62. 62
      Quintanilla, M.; Liz-Marzán, L. Guiding rules for selecting a nanothermometer. Nano Today 2018, 19, 126– 145,  DOI: 10.1016/j.nantod.2018.02.012
      62
      Guiding Rules for Selecting a Nanothermometer
      Quintanilla, Marta; Liz-Marzan, Luis M.
      Nano Today (2018), 19 (), 126-145CODEN: NTAOCG; ISSN:1748-0132. (Elsevier Ltd.)
      A review. Temp. is a basic parameter influencing the behavior of systems in physics, chem. and biol. From living cells to microcircuits, a wide range of cases require thermometry techniques that can be applied to reduced areas, offering sub-micrometric resoln. and high accuracy. Since traditional thermometers cannot be applied in such systems, alternative tools have been specifically designed to measure temp. at the nanoscale; including scanning thermal microscopy, non-contact optical techniques or various types of luminescent nanoparticles. Each option presents interesting advantages, but also limitations that need to be considered and understood. We provide here an overview of the main currently available nanothermometry tools, discussing their pros and cons toward potential applications.
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    63. 63
      Back, M.; Ueda, J.; Brik, M. G.; Lesniewski, T.; Grinberg, M.; Tanabe, S. Revisiting Cr3+-doped Bi2Ga4O9 spectroscopy: Crystal field effect and optical thermometric behavior of near-infrared-emitting singly-activated phosphors. ACS Appl. Mater. Interfaces 2018, 10, 41512– 41524,  DOI: 10.1021/acsami.8b15607
      63
      Revisiting Cr3+-Doped Bi2Ga4O9 Spectroscopy: Crystal Field Effect and Optical Thermometric Behavior of Near-Infrared-Emitting Singly-Activated Phosphors
      Back, Michele; Ueda, Jumpei; Brik, Mikhail G.; Lesniewski, Tadeusz; Grinberg, Marek; Tanabe, Setsuhisa
      ACS Applied Materials & Interfaces (2018), 10 (48), 41512-41524CODEN: AAMICK; ISSN:1944-8244. (American Chemical Society)
      The increasing interest in the development of ratiometric optical thermal sensors led to a wide variety of new systems with promising properties. Among them, singly-doped ratiometric thermometers were recently demonstrated to be particularly reliable. With the aim to discuss the development of an ideal optical thermal sensor, a combined exptl. and theor. insight into the spectroscopy of the Bi2Ga4O9:Cr3+ system is reported showing the importance of an insightful anal. in a wide temp. range. Low-temp. luminescence anal. (from 10 K) and the temp. dependence of the lifetime study, together with the crystal field anal. and the modeling of the thermal quenching process, allow the estn. of key parameters such as the Debye temp. (cutoff frequency), the Huang-Rhys parameter, and the energy barrier between 2Eg and 4T2g. Addnl., by considering the reliable class of singly-doped ratiometric thermometers based on a couple of excited states obeying the Boltzmann law, the important role played by the abs. sensitivity was discussed and the great potential of Cr3+ singly-activated systems was demonstrated. The results may provide new guidelines for the design of reliable optical thermometers with outstanding and robust performances.
      >> More from SciFinder ®
      https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1cXitVKiurrI&md5=61e0d295161e936dbf656e30ed4480a8
    64. 64
      Back, M.; Ueda, J.; Xu, J.; Asami, K.; Brik, M. G.; Tanabe, S. Effective ratiometric luminescent thermal sensor by Cr3+-doped mullite Bi2Al4O9 with robust and reliable performances. Ad. Opt. Mater. 2020, 8, 2000124,  DOI: 10.1002/adom.202000124
      There is no corresponding record for this reference.

  • Supporting Information

    Supporting Information

    The Supporting Information is available free of charge at https://pubs.acs.org/doi/10.1021/acs.chemmater.2c01262.

    • Parameters obtained from the Rietveld refinement analysis, PL decay curve of the material, absolute sensitivity versus relative sensitivity plot and data for a series of Nd3+-activated Boltzmann thermometers, NIR-to-NIR Boltzmann thermometry in the second biological window (temperature dependence of PL spectra, Boltzmann plot, absolute sensitivity, relative sensitivity, and repeatability), thermometric parameters and performances based on chroma Cab* and the color difference ΔEab*, and colorimetric parameter values at different temperatures (PDF)


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