ACS Publications. Most Trusted. Most Cited. Most Read
Dual “Static and Dynamic” Fluorescence Quenching Mechanisms Based Detection of TNT via a Cationic Conjugated Polymer
More

OR SEARCH CITATIONS

My Activity
Publications

Figure 1Loading Img
Download Hi-Res ImageDownload to MS-PowerPointCite This:ACS Meas. Sci. Au 2022, 2, 1, 23-30
  • Open Access
Article

Dual “Static and Dynamic” Fluorescence Quenching Mechanisms Based Detection of TNT via a Cationic Conjugated Polymer
Click to copy article linkArticle link copied!

Open PDFSupporting Information (1)

ACS Measurement Science Au

Cite this: ACS Meas. Sci. Au 2022, 2, 1, 23–30
Click to copy citationCitation copied!
https://doi.org/10.1021/acsmeasuresciau.1c00023
Published September 8, 2021

Copyright © 2021 The Authors. Published by American Chemical Society. This publication is licensed under

CC-BY-NC-ND 4.0 .

Abstract

Click to copy section linkSection link copied!
High Resolution Image
Download MS PowerPoint Slide

A rare combination of dual static and dynamic fluorescence quenching mechanisms is reported, while sensing the nitroexplosive trinitrotoluene (TNT) in water by a cationic conjugated copolymer PFPy. Since the fluorophore PFPy interacts with TNT in both ground state as well as the excited states, a greater extent of interaction is facilitated between PFPy and the TNT, as a result of which the magnitude of the signal is amplified remarkably. The existence of these collective sensing mechanisms provides additional advantages to the sensing process and enhances the sensing parameters, such as LoD and highly competitive sensing processes in natural water bodies irrespective of the pH and at ambient conditions. These outcomes involving dual sensing mechanistic pathways expand the scope of developing efficient sensing probes for toxic chemical analyte and biomarker detection, preventing environmental pollution and strengthening security at sensitive locations while assisting in early diagnosis of disease biomarkers.

This publication is licensed under

CC-BY-NC-ND 4.0 .
  • cc licence
  • by licence
  • nc licence
  • nd licence
Copyright © 2021 The Authors. Published by American Chemical Society

Subjects

what are subjects

Keywords

what are keywords

Introduction

Click to copy section linkSection link copied!
In recent years, research and development on sensing of explosives has gained tremendous attention. (1) 2,4,6-Trinitrotoluene (TNT) is a well-known nitroaromatic compound (NAC) belonging to a secondary class of explosives. (2) Due to its relatively high solubility in water, i.e., 130 mg/L at 20 °C, and its wide use in military operation, land mines, terrorism, and industrial applications, it contaminates land, agricultural soil, and water reservoirs and enters into the food chain. (3) Thus, it has been recognized by US Environment Protection Agency (EPA) as a contaminant, whose maximum permissible limit has been set to 20 μg/L in drinking water. (3) Its consumption causes severe health hazards, leading to skin irritation, liver function abnormalities, cataracts, cancer, and mutagenic activity post metabolism. (3) Additionally, other NACs, which possess a similar electron-deficient nature, generally interfere with selective detection of TNT. Hence, it is challenging to design a selective and sensitive TNT sensor from the view of the environmental pollution and overall security threat.
Thus far, few analytical techniques have been utilized for detection of TNT, for example, surface-enhanced Raman spectroscopy (SERS), (4) liquid chromatography–mass spectrometry, (5) electrochemical methods, (6) energy-dispersive X-ray diffraction, (7) and capillary electrophoresis. (8) Having their own distinct advantages, these techniques have certain limitations such as high instrument costs, low sensitivity, time-consuming process, and complications in on-site detection. However, fluorescence has been utilized widely in the sensing of explosive TNT due to its superior sensitivity, better selectivity, and rapid on-site detection with a variety of multiple portable economical platforms. Hence, various fluorescent probes have been designed for TNT sensing, which include carbon quantum dots, metal nanoparticles, organic nanoaggregates, and nonconjugated and conjugated polymers (CPs). (9−21)
CPs have been explored for sensing many vital analytes. (22,23) It is their remarkable photophysical properties such as tunable broad absorption, high photoluminescence (PL) quantum yield, and ultrasensitivity due to the “Molecular Wire Effect”, which makes them ideal for sensing applications. (24) Hence, few CPs have been reported for TNT sensing. (15,16,25−27) Yet, many of them suffer from issues of sensitivity, selectivity, portability, and poor solubility in aqueous detection medium. Moreover, achieving a limit of detection (LOD) covering the safety limit of TNT in drinking water has also remained elusive.
Herein, a cationic pyridinium appended fluorescent CP (PFPy) was synthesized for the specific and ultrasensitive detection of TNT in water (Scheme 1). In order to enhance the solubility of TNT, a strategy of using an alkaline medium (pH = 12) was used to facilitate the formation of the anionic Meisenheimer complex intermediate, which effectively undergoes electrostatic interaction with cationic side chains of the PFPy selectively even in trace levels and generates a detectable output rapidly. PFPy, an alternating copolymer of fluorene and benzothidiazole monomers, provides a desired red shift in the photophysical properties, and required essentially for realizing the energy transfer process with the anioinic Meisenheimer complex of TNT. The cationic side chains of the PFPy also behave as receptors, and binds very efficiently with the oppositely charged analyte species. A careful step-by-step elucidation and analysis of the sensing mechanism revealed the involvement of both static as well as dynamic quenching for TNT detection for the first time to the best of our knowledge. Thus, PFPy is a very unique sensor for TNT detection in water with exceptionally high sensitivity, stability, and good selectivity via combination of both static and dynamic quenching mechanisms, providing high precision for TNT detection.

Scheme 1

Scheme 1. (a) 1,6-Dibromohexane, Tetrabutylammonium Iodide (TBAI), 50% NaOH(aq.), 70 °C, 4 h. (b) Tetrakistriphenylphosphine Palladium (0), 2,1,3-Benzothiadiazole-4,7-Bis(boronic acid pinacol ester), aq. K2CO3, THF, reflux, 24 h; (c) Pyridine, DMF, 70 °C, 24 h
High Resolution Image
Download MS PowerPoint Slide

Results and Discussion

Click to copy section linkSection link copied!

Synthesis and Characterization of PFPy

The synthesis of the desired copolymer PFPy is depicted in Scheme 1. The products (monomer and polymer) at each step were purified and well characterized (Figures S1–S5). PF acts as a precursor polymer for PFPy synthesis. Cationic pyridinium units, that work as key receptor sites for the analyte TNT binding, also making it soluble in polar solvents (water, DMSO, etc.), were strategically linked to the pendant chains to generate the final copolymer PFPy. The aqueous solution of PFPy displayed a UV–vis absorption peak at 430 nm and emission peak at 553 nm (excitation wavelength = 430 nm) (Figure S6) with a remarkable fluorescence quantum yield (Φs) of 0.59 in water. The fluorescence emission peak (553 nm) obtained for PFPy at pH = 12 was monitored to evaluate the sensing response of PFPy toward TNT (Figure S7).

Sensing Studies for TNT Detection

The cationic PFPy copolymer was highly fluorescent as visualized under UV light even at a very dilute concentration (6.66 × 10–6 M) (Figure S8) and was found to be very sensitive and highly selective to TNT (Figure S9). The PL intensity of PFPy is quenched by ∼39% after the first addition of 0.33 μM TNT solution (Figure 1a) and reduces by ∼97% at 3.3 μM TNT solution (Figures 1a and S8). As a result of this extraordinary sensitivity of PFPy toward TNT, an LOD of 4.94 fM was achieved (Figure S10), which is the best reported value for TNT detection (Table S2).

Figure 1

Figure 1. (a) PL spectra of PFPy (6.66 μM) at different concentration of TNT in water containing 10 mM NaOH. (b) Effect of various NACs (3.33 μM) on the PFPy (6.66 μM) intensity. (c) S–V plots (3D) obtained for various NACs. (d) Quenching (%) by various NACs (3.33 μM) before (blue) and after (red) addition of TNT (3.33 μM).

High Resolution Image
Download MS PowerPoint Slide

Selectivity Studies

Selectivity has always been a huge challenge in the development of efficient sensor platforms. Especially for the detection of nitroexplosive TNT, its most identical chemical analogue picric acid (PA) interferes in its detection, as can be noticed in the previous reports (Table S2). Therefore, keeping the same experimental conditions that were optimized for the detection of TNT, selectivity studies of PFPy were performed with various common interfering analytes such as 1,3-DNB, 4-NP, PA, 2,4-DNT, 2,4-DNP, toluene, 4-NT, 2,6-DNT, NB, 2-NP, and phenol. It was found that PFPy possesses high selectivity only toward TNT (Figures 1b and S11). The Stern–Volmer (S–V) plots obtained for all the interfering NACs confirmed the quenching efficiency values for various NACs to be negligible compared to that of TNT (Figure 1c) confirming that PFPy has extraordinary selectivity toward TNT as established via studies performed in a competitive environment with different NACs.
Further, 2,6-DNT (3.33 μM) was mixed with the above PFPy (6.66 μM) solution, so that 2,6-DNT could interact with the PFPy prior to the additional mixing of TNT (3.33 μM). It was observed that adding 2,6-DNT (3.33 μM) to the solution of PFPy caused an insignificant change in the PL intensity, while TNT caused substantial quenching of fluorescence even in the presence of 2,6-DNT (Figures 1d and S12). Since TNT forms the intermediate anionic Meisenheimer complex rapidly compared to 2,6-DNT, it selectively binds the cationic pyridinium receptors of PFPy even in the presence of 2,6-DNT. Similar competitive studies were done with other NACs, and identical results were obtained, indicating high selectivity of the PFPy sensing system for TNT even in the presence of interfering competitive NACs (Figures 1d and S13–S22). These studies confirm that the PFPy polymeric system is an exceptional sensor that provides a very sensitive, selective, and rapid detection of TNT even in a competitive environment.

Mechanism of Sensing

To analyze the very high sensing performance of the PFPy, it was necessary to precisely understand the mechanism of sensing among the many possibilities. (22,28−30) On analyzing the S–V plot for TNT titration, the best fitting for a second order of the polynomial curve was observed [Figure 2 (1a and 1b)]. This second-order polynomial curve of the S–V plot is evidence for the coexistence of both static and dynamic quenching mechanisms in any sensing system [Figure 2(1c)]. (31) In this polynomial equation (I) [Figure 2 (1c)], I and Io are the PL intensities of the PFPy with and without TNT, [Q] denotes the concentration of the quencher, i.e., [TNT], KD and KS are quenching constants for the corresponding dynamic and static quenching, respectively. Second, to confirm the involvement of dynamic quenching in the sensing process and determine the corresponding value of KD, TRPL studies of PFPy were performed at various concentrations of TNT and its fluorescence lifetime was monitored. Interestingly, there was a noteworthy decrease in the fluorescence lifetime of PFPy after addition of TNT (3.33 μM) [Figure 2 (2a) and Table S1]. This confirmed the presence of dynamic quenching during the sensing process. (28,31) Further, this change in fluorescence lifetime was plotted as τo/τ with respect to various concentrations of TNT [Figure 2 (2b)], where τ and τo are the average fluorescence lifetime with and without TNT, respectively. The linear fitting of the above plot (τo/τ vs [TNT]) yielded an equation of a straight line whose intercept is 1, and the slope of this equation represents the dynamic quenching constant (KD), which was found to be 2.06 × 105 M–1 [Figure 2 (2b)]. (31) This unusually high value of KD specifies high fluorescence quenching efficiency due to the dynamic quenching mechanism.

Figure 2

Figure 2. (1) Stern–Volmer (S–V) plot (2D) obtained for (a) all NACs and (b) second-order polynomial fitting of S–V plot for TNT. (c) S–V equation for both static and dynamic quenching. (2) (a) Time-resolved photoluminescence (TRPL) spectra of PFPy (6.66 μM) in the absence and presence of various concentration of TNT in water containing 10 mM NaOH. (b) Change in lifetime at various concentrations of TNT. (c) Equation (II) for dynamic quenching: where τ and τo are the average fluorescence lifetime with and without TNT, respectively. (3) (a) Spectral overlap between the normalized PL spectrum [0–0.1] of CP PFPy with absorbance of various NACs in water containing 10 mM NaOH. (b) Spectral overlapping region between the normalized emission spectrum of PFPy with TNT in water containing 10 mM NaOH. (c) Equations for RET parameters: (1) Equation (III)-where J denotes overlap integral value, FD(λ) represents the corrected fluorescence intensity from λ to Δλ with total fluorescence intensity for PFPy normalized to 1, and εA represents molar absorptivity of acceptor in M–1 cm–1. (2) Equation (IV)-where R0 represents Förster distance, Q denotes the fluoresence quantum yield of PFPy, η represents refractive index of the medium, and k2 signifies dipole orientation factor (0.667). (3) Equation (V)-where E% denotes RET efficiency, τDA and τD are the average fluorescence lifetime with and without quencher, i.e., TNT.

High Resolution Image
Download MS PowerPoint Slide
Additionally, there are various subtypes of dynamic quenching mechanisms that exist, which are due to either collisional interactions or the involvement of excited-state phenomena such as Förster resonance energy transfer (FRET) in the sensing process. Generally, FRET has three primary conditions for occurring in any donor (D) and acceptor (A) sensing system. First, there should be significant overlap between the absorbance of the acceptor and the fluorescence of the donor. Second, the distance between the donor and the acceptor, i.e., the Förster distance, should be <10 nm for an effective FRET. Third, they should have suitable relative dipole orientations for FRET to occur. (28) To verify this, UV–vis absorption spectra of all the NACs and the normalized emission spectrum of the PFPy were plotted together [Figure 2 (3a)]. It was found that among all the NACs only TNT had an effective spectral overlap with the emission spectrum of PFPy [Figure 2 (3b)]. Hence, a very high selectivity was achieved for TNT as compared to other NACs. Further, RET parameters were also calculated for TNT sensing using the equations shown in Figure 2 (3c), (28) where J represents the overlap integral [Figure 2 (3c); equation (III)], which governs the extent of RET and was found to be 3.0 × 1013 M–1 cm–1 nm4 (Table S3). The value obtained for the Förster distance (R0) [Figure 2 (3c); equation (IV)], was found to be 24.95 Å, which also fits in between the range of feasible FRET to occur. RET efficiency for this sensing system was found to be 35.68%, which further confirms the contribution of RET in the mechanism of sensing [Figure 2 (3c); equation (V)]. Additionally, like the RET, inner filter effect (IFE) is also governed by the spectral overlap. However, in the case of IFE, spectral overlap happens among the emission and/or the excitation spectrum of fluorophore (PFPy) with absorbance of quencher (TNT). (22) Hence, to check if IFE is present, IFE corrections were performed using previously established methods via eq VI. (29,31,32)
(VI)
where Icorr and Iobs signify PL intensities after and before IFE corrections, Aex and Aem are the absorbance of the sensing system at the excitation and emission wavelength of the fluorophores, i.e., PFPy. It was found that there is no significant change in the PL intensity as well as in the suppression efficiency after performing the IFE correction [Figure S23 and Table S4 (detailed data are listed here)]. These results clearly exclude the involvement of IFE in the mechanism of TNT sensing.
Furthermore, to prove the involvement of static quenching (ground-state complexation) in the mechanism of sensing and to calculate its corresponding quenching constant (Ks), the absorbance of PFPy (6.66 μM) was obtained in the presence of various amounts of TNT (Figure 3a). It was seen that there is a shift in the absorption peak of PFPy to 440 nm. This shift in the peak of cationic PFPy clearly indicated the formation of ground-state complex with anionic Meisenheimer complex of TNT, while the appearance of a new absorption band at around 460 nm corresponds to the formation of the intermediate Meisenheimer complex of TNT at pH 12 (Figure 3b and Figure S24). (33,34) However, the anionic Meisenheimer peak was not observed in water at neutral pH, and hence, fluorescence quenching did not occur in water at neutral pH conditions (Figures S26 and S27). These key observations further prove the involvement of the static quenching mechanism in the sensing process. Additionally, in order to calculate the value of KS, a plot of Kapp versus concentration of TNT was obtained (Figure 3c). This curve was linearly fitted where the slope of this linear curve represents the (KD × KS) value, which was 1 × 1012 M–2, and the intercept of this line represents the (KD + KS) value, and was found to be 3 × 106 M–1 (Figure 3c). Rearrangement of the aforementioned values yielded a quadratic equations (VII), whose solutions are shown in equation (VIII), i.e., KS = 26.1 × 105 M–1 or 3.8 × 105 M–1. Previously, from equation (II), the value of KD, i.e., 2.0 × 105 M–1 was already known. Therefore, the higher value was assigned for the static quenching constant (KS), i.e., 26.1 × 105 M–1 (Figure 3d, equation IX). The higher value of KS clearly indicated the dominance of the static quenching in the mechanism of sensing and that was also responsible for higher selectivity as well as ultrasensitivity of the PFPy sensing system for TNT.

Figure 3

Figure 3. (a) Absorbance of PFPy (6.66 μM) in the presence of various amounts of TNT in water containing 10 mM NaOH. (b) Absorbance of TNT in water containing 10 mM NaOH. (c) Plot of Kapp versus concentration of TNT in water containing 10 mM NaOH. (d) Equations and calculation for static and dynamic quenching constants, i.e., KS and KD, respectively.

High Resolution Image
Download MS PowerPoint Slide
Overall, PFPy possessed outstanding sensitivity and high selectivity toward TNT due to the strong static quenching mechanism along with remarkable dynamic quenching mechanism, which is exceptional and has been explored elaborately for the first time (Table S2). This combined dynamic and static quenching mechanism can be adopted to develop efficient fluorescent sensors, based on quenching of fluorophore via both collisional as well as complex formation with the same analyte/quencher. Interestingly, these results are very unique for an analyte/quencher like TNT. These collective sensing mechanisms can add extra advantage for enhancing the sensing parameters, such as LoD, competitive sensing, etc. As the fluorophore interacts with the quencher in both ground as well as excited states, this leads to a greater extent of interaction by the fluorophore with the analyte/quencher and hence the magnitude of signal is amplified remarkably (Figure 4).

Figure 4

Figure 4. Combined dynamic and static quenching of the same population of the fluorophore PFPy via quencher (Q), i.e., Meisenheimer complex of TNT.

High Resolution Image
Download MS PowerPoint Slide

Detection of TNT in a Natural Reservoir

To further evaluate the feasibility of PFPy in an open water reservoir, different samples of water were obtained from the “Serpentine Lake” (inside IIT Guwahati campus). These samples were filtered through membrane of size 0.2 μm and then tested for TNT sensing. It was found that the water samples did not cause any substantial change in the intensity of the PFPy, confirming the absence of TNT. These samples were spiked with a known amount of TNT and then tested under the same conditions (Table 1). Recoveries were found to be high, i.e., in the range of 90–100% with very minor RSD values. Therefore, PFPy can be used to detect TNT efficiently in natural water reservoirs and their concentrations can be estimated using PFPy.
Table 1. Detection of TNT in Reservoir
reservoiradded (10–9 M)found (10–9 M)recovery (%)RSD (%, n = 3)
Lake water9.008.6596.17.79
15.0014.2094.62.67
30.0027.3091.03.26

Sensing on Portable Testing Strips

For on-site contact-mode detection of TNT, a very simple methodology was adopted to prepare economical and convenient paper test device strips. For this purpose, Whatman filter paper (Grade I) was cut into a convenient size (1 cm × 1 cm) and desired shape (square in this case) and dipped into the PFPy solution (10–4 M) for solid-phase rapid on-site contact-mode detection. Subsequently, the paper devices were dried and then dipped in water containing 10 mM NaOH solution and further dried for final use for on-site detection of TNT. Fixed volumes (10 μL) of different concentrations of TNT solutions were spotted over the portable paper device strips, and fluorescence quenched marks were clearly observed on UV irradiation (Figure 5). The dark spots can be clearly visualized under the UV lamp up to 10 μL TNT solution (10–5 M), which is equivalent to 22.7 ng level and are best among the reported sensors (Table S2).

Figure 5

Figure 5. Photographs of portable paper strips under the UV emitting lamp of 365 nm wavelength after applying a fixed volume (10 μL) of different concentration of TNT solution.

High Resolution Image
Download MS PowerPoint Slide

Detection of TNT in Soil Samples

To determine the ability of polymer PFPy to detect traces of TNT in natural soil samples, we collected different samples of soil from three separate locations (Figures 6 and S25). Thereafter, 50 mg of each soil sample was spiked with known dissimilar concentrations of 10 μL of TNT solutions. Then, PFPy coated paper strips were brought in contact with the soil samples for ∼2 min. After that, the sensing strips were examined under the UV lamp (365 nm). It could be clearly observed that the contacted portion of the paper strips with the soil samples changed to a dark spot due to the quenching process. Thus, this study confirms that the PFPy can effectively detect trace TNT quantities (22.7 ng level) present in the soil samples. These experiments confirm that PFPy-based sensors can function both in solution as well as in a portable device for rapid on-site detection of TNT at very low concentrations, and the high sensitivity is because of the very rare multiple sensing mechanisms operating in the presence of TNT.

Figure 6

Figure 6. Photographs of three different locations and portable paper strips under UV light after being in contact with soil samples spiked with different concentration of TNT.

High Resolution Image
Download MS PowerPoint Slide

Conclusion

Click to copy section linkSection link copied!
In summary, a newly developed cationic conjugated copolymer PFPy was successfully employed for the selective detection of TNT in parts per trillion levels in water via an intermediate Meisenheimer complex formation. This copolymeric system displayed remarkable selectivity that works even in a highly competitive environment of various interfering NACs. These extraordinary results were achieved due to the presence of a combination of both static and dynamic fluorescence quenching mechanisms, allowing a conceptually unique process of both ground-state as well as excited-state interactions of the probe PFPy with the analyte TNT that provided a very high KS value of 26.1 × 105 M–1 and KD = 2.0 × 105 M–1. PFPy also displayed instant TNT sensing ability over the economical portable paper test strip devices in contact mode and can detect as low as 22.7 ng of TNT to offer an easy, straightforward, cost-effective, and rapid sensing platform in a competitive natural environment source.

Supporting Information

Click to copy section linkSection link copied!

The Supporting Information is available free of charge at https://pubs.acs.org/doi/10.1021/acsmeasuresciau.1c00023.

  • All the characterization data such as NMR spectra, GPC, UV–vis, and PL spectra, LoD plot, table of comparison, IFE and RET calculations, sensing photographs in solution and on paper (PDF)

Terms & Conditions

Most electronic Supporting Information files are available without a subscription to ACS Web Editions. Such files may be downloaded by article for research use (if there is a public use license linked to the relevant article, that license may permit other uses). Permission may be obtained from ACS for other uses through requests via the RightsLink permission system: http://pubs.acs.org/page/copyright/permissions.html.

Author Information

Click to copy section linkSection link copied!
  • Corresponding Author
    • Parameswar Krishnan Iyer - Department of Chemistry, Indian Institute of Technology Guwahati, Guwahati-781039, Assam, India;  Centre for Nanotechnology, Indian Institute of Technology Guwahati, Guwahati-781039, Assam, India;  Orcidhttps://orcid.org/0000-0003-4126-3774;  Email: [email protected]
  • Authors
    • Arvin Sain Tanwar - Department of Chemistry, Indian Institute of Technology Guwahati, Guwahati-781039, Assam, India;  Orcidhttps://orcid.org/0000-0003-0042-7306
    • Retwik Parui - Department of Chemistry, Indian Institute of Technology Guwahati, Guwahati-781039, Assam, India
    • Rabindranath Garai - Department of Chemistry, Indian Institute of Technology Guwahati, Guwahati-781039, Assam, India;  Orcidhttps://orcid.org/0000-0002-1339-8666
    • Moirangthem Anita Chanu - Department of Chemistry, Indian Institute of Technology Guwahati, Guwahati-781039, Assam, India
  • Notes
    The authors declare no competing financial interest.

Acknowledgments

Click to copy section linkSection link copied!

Department of Electronics & Information Technology, (Deity) No. 5(9)/2012-NANO (Vol. II), Department of Science and Technology (DST/CRG/2019/002614), and Max-Planck-Gesellschaft (IGSTC/MPG/PG(PKI)/2011A/48) are acknowledged for financial support. Authors thank CIF for instrument facilities and CoE-SusPol, IIT Guwahati funded by the Department of Chemicals and Petrochemicals (No. 15012/9/2012-PC.1) for GPC analysis.

References

Click to copy section linkSection link copied!

This article references 34 other publications.

  1. 1
    Sun, X.; Wang, Y.; Lei, Y. Fluorescence based explosive detection: from mechanisms to sensory materials. Chem. Soc. Rev. 2015, 44 (22), 8019– 8061,  DOI: 10.1039/C5CS00496A
    Google Scholar
    1
    Fluorescence based explosive detection: from mechanisms to sensory materials
    Sun, Xiangcheng; Wang, Ying; Lei, Yu
    Chemical Society Reviews (2015), 44 (22), 8019-8061CODEN: CSRVBR; ISSN:0306-0012. (Royal Society of Chemistry)
    The detection of explosives is one of the current pressing concerns in global security. In the past few decades, a large no. of emissive sensing materials have been developed for the detection of explosives in vapor, soln., and solid states through fluorescence methods. In recent years, great efforts have been devoted to develop new fluorescent materials with various sensing mechanisms for detecting explosives in order to achieve super-sensitivity, ultra-selectivity, as well as fast response time. This review article starts with a brief introduction on various sensing mechanisms for fluorescence based explosive detection, and then summarizes in an exhaustive and systematic way the state-of-the-art of fluorescent materials for explosive detection with a focus on the research in the recent 5 years. A wide range of fluorescent materials, such as conjugated polymers, small fluorophores, supramol. systems, bio-inspired materials and aggregation induced emission-active materials, and their sensing performance and sensing mechanism are the centerpiece of this review. Finally, conclusions and future outlook are presented and discussed.
  2. 2
    Sun, Y.; Wu, Y.; Yu, C.; Zhang, L.; Song, G.; Yao, Z. Self-Assembly of nanoscale induced excimers of 12-Pyren-1-yldodecanoic acid for TNT detection. ACS Appl. Nano Mater. 2019, 2 (6), 3453– 3458,  DOI: 10.1021/acsanm.9b00386
    Google Scholar
    2
    Self-Assembly of Nanoscale Induced Excimers of 12-Pyren-1-yldodecanoic Acid for TNT Detection
    Sun, Yanan; Wu, Yuwei; Yu, Chaoran; Zhang, Li; Song, Gang; Yao, Zhiyi
    ACS Applied Nano Materials (2019), 2 (6), 3453-3458CODEN: AANMF6; ISSN:2574-0970. (American Chemical Society)
    We report nanoscale pyrenyl excimers induced by the self-assembly of a pyrene-based fluorescent probe, 12-pyren-1-yldodecanoic acid (PyDA), for rapid detection of 2,4,6-trinitrotoluene (TNT) in aq. media. Under the optimized conditions, the sensing nanosystem exhibited fast response and high selectivity and sensitivity for the detection of TNT. Esp., it could distinguish TNT from TNP, which is the major interferent in most circumstances. The detection limit is as low as 5.0 × 10-9 M. It also can be used for qual. and quant. monitoring TNT in real samples.
  3. 3
    Agency for toxic substances and disease registry Toxicological profile for 2,4,6-trinitrotoluene ; 1995; https://wwwn.cdc.gov/TSP/ToxProfiles/ToxProfiles.aspx?id=677&tid=125.
    Google Scholar
    There is no corresponding record for this reference.
  4. 4
    Hakonen, A.; Andersson, P. O.; Stenbæk Schmidt, M.; Rindzevicius, T.; Käll, M. Explosive and chemical threat detection by surface-enhanced Raman scattering: a review. Anal. Chim. Acta 2015, 893, 1– 13,  DOI: 10.1016/j.aca.2015.04.010
    Google Scholar
    4
    Explosive and chemical threat detection by surface-enhanced Raman scattering: A review
    Hakonen, Aron; Andersson, Per Ola; Stenbaek Schmidt, Michael; Rindzevicius, Tomas; Kaell, Mikael
    Analytica Chimica Acta (2015), 893 (), 1-13CODEN: ACACAM; ISSN:0003-2670. (Elsevier B.V.)
    A review. Acts of terror and warfare threats are challenging tasks for defense agencies around the world and of growing importance to security conscious policy makers and the general public. Explosives and chem. warfare agents are two of the major concerns in this context, as illustrated by the recent Boston Marathon bombing and nerve gas attacks on civilians in the Middle East. To prevent such tragic disasters, security personnel must be able to find, identify and deactivate the threats at multiple locations and levels. This involves major tech. and practical challenges, such as detection of ultra-low quantities of hazardous compds. at remote locations for anti-terror purposes and monitoring of environmental sanitation of dumped or left behind toxic substances and explosives. Surface-enhanced Raman scattering (SERS) is one of todays most interesting and rapidly developing methods for label-free ultrasensitive vibrational "fingerprinting" of a variety of mol. compds. Performance highlights include attomolar detection of TNT and DNT explosives, a sensitivity that few, if any, other technique can compete with. Moreover, instrumentation needed for SERS anal. are becoming progressively better, smaller and cheaper, and can today be acquired for a retail price close to 10,000 US$. This contribution aims to give a comprehensive overview of SERS as a technique for detection of explosives and chem. threats. The authors discuss the prospects of SERS becoming a major tool for convenient in-situ threat identification and the authors summarize existing SERS detection methods and substrates with particular focus on ultra-sensitive real-time detection. General concepts, detection capabilities and perspectives are discussed to guide potential users of the technique for homeland security and anti-warfare purposes.
  5. 5
    Zhao, X.; Yinon, J. Characterization and origin identification of 2,4,6-trinitrotoluene through its by-product isomers by liquid chromatography–atmospheric pressure chemical ionization mass spectrometry. J. Chromatogr. A 2002, 946 (1), 125– 132,  DOI: 10.1016/S0021-9673(01)01533-3
    Google Scholar
    5
    Characterization and origin identification of 2,4,6-trinitrotoluene through its by-product isomers by liquid chromatography-atmospheric pressure chemical ionization mass spectrometry
    Zhao, Xiaoming; Yinon, Jehuda
    Journal of Chromatography A (2002), 946 (1-2), 125-132CODEN: JCRAEY; ISSN:0021-9673. (Elsevier Science B.V.)
    The byproducts of industrial 2,4,6-trinitrotoluene (TNT), including isomers of trinitrotoluene, dinitrotoluene, trinitrobenzene and dinitrobenzene were studied using liq. chromatog.-mass spectrometry (LC-MS), to build a profile for the characterization of TNT samples from various origins. LC-MS with atm. pressure chem. ionization, in the neg.-ion mode, is the most suitable method for this study. The characterization of TNT by the byproduct profile was demonstrated on a variety of TNT samples.
  6. 6
    Trammell, S. A.; Melde, B. J.; Zabetakis, D.; Deschamps, J. R.; Dinderman, M. A.; Johnson, B. J.; Kusterbeck, A. W. Electrochemical detection of TNT with in-line pre-concentration using imprinted diethylbenzene-bridged periodic mesoporous organosilicas. Sens. Actuators, B 2011, 155 (2), 737– 744,  DOI: 10.1016/j.snb.2011.01.039
    Google Scholar
    6
    Electrochemical detection of TNT with in-line pre-concentration using imprinted diethylbenzene-bridged periodic mesoporous organosilicas
    Trammell, Scott A.; Melde, Brian J.; Zabetakis, Daniel; Deschamps, Jeffrey R.; Dinderman, Michael A.; Johnson, Brandy J.; Kusterbeck, Anne W.
    Sensors and Actuators, B: Chemical (2011), 155 (2), 737-744CODEN: SABCEB; ISSN:0925-4005. (Elsevier B.V.)
    The authors examd. the adsorption and release of TNT using diethylbenzene-bridged (DEB) periodic mesoporous organosilica sorbents under varying conditions. The sorbents were applied for in-line target pre-concn. in conjunction with an electrochem. flow cell contg. a glassy carbon electrode. Square wave voltammetry was employed for TNT detection. TNT sample vols. between 2 and 480 mL at concns. ranging from 0.5 to 500 ppb were passed through the DEB sorbents (imprinted or not imprinted for TNT) at pH 6 (sodium acetate) or at pH 7.4 (PBS). Release of target was accomplished using solvent mixts. of methanol/water with sodium acetate as electrolyte or acetonitrile/water with PBS components as electrolyte. Under these conditions, the TNT was released in <200 μL of the solvent mixt., and pre-concn. factors of >3000 can be achieved when using large vols. of trace TNT samples. When sample vols. of 2 mL were used, the sensing system gave a linear response between 20 and 500 ppb with an estd. limit of detection of 13 ppb. When pre-concg. 480 mL of sample in either buffered soln. or seawater, detection of 0.5 ppb TNT was achieved with a signal to noise ratio of 20.
  7. 7
    Soldate, A. M.; Noyes, R. M. X-Ray diffraction patterns for identification of crystalline constituents of explosives. Anal. Chem. 1947, 19 (7), 442– 444,  DOI: 10.1021/ac60007a004
    Google Scholar
    7
    X-ray diffraction patterns for the identification of crystalline constituents of explosives
    Soldate, Albert M.; Noyes, Richard M.
    (1947), 19 (), 442-4CODEN: ANCHAM; ISSN:0003-2700.
    New powder-diffraction data, suitable for use as aids in the identification of constituents in unknown samples, are given for 18 org. compds. present in explosives. The data were obtained with Cu Kα radiation, filtered by Ni foil and collimated by a two-slit system. A form similar to that used by Hanawalt, Rinn, and Frevel (C.A. 32, 7841.8) for the presentation of x-ray powder data to be used for analytical purposes was used. Only the morphological forms of these compds. commonly occurring in the explosives under investigation were studied. Interplanar spacings and approx. intensities are given in tabular form for the following compds.: pentaerythritol tetranitrate, 2,4-dinitrotoluene, 2,4,6-trinitrotoluene, picric acid, guanidine picrate, ethylene-dinitramine, nitroguanidine, 2,2,5,5-tetrahydroxymethylcyclopentanone tetranitrate, dihydroxyethylnitramine dinitrate, hexahydro-1,3,5-trinitro-s-triazine, octahydro-1,3,5,7-tetranitro-s-tetrazine, 1-acetyloctahydro-3,5,7-trinitro-s-tetrazine, α, β-diethylcarbanilide, diphenylamine, N-nitrosodiphenylamine, 2-nitrodiphenylamine, 2,4'-dinitrodiphenylamine, 4,4'-dinitrodiphenylamine.
  8. 8
    Calcerrada, M.; González-Herráez, M.; García-Ruiz, C. Recent advances in capillary electrophoresis instrumentation for the analysis of explosives. TrAC, Trends Anal. Chem. 2016, 75, 75– 85,  DOI: 10.1016/j.trac.2015.08.005
    Google Scholar
    8
    Recent advances in capillary electrophoresis instrumentation for the analysis of explosives
    Calcerrada, Matias; Gonzalez-Herraez, Miguel; Garcia-Ruiz, Carmen
    TrAC, Trends in Analytical Chemistry (2016), 75 (), 75-85CODEN: TTAEDJ; ISSN:0165-9936. (Elsevier B. V.)
    Capillary electrophoresis (CE) is a well-established anal. sepn. technique. Owing to its high versatility, major advancements have been made with regard to the instrumental set-ups during the last years. New strategies have been proposed to develop high-sensitive methods, portable CE or miniaturized devices. These techniques are of great interest in the anal. of explosives, which generally requires a highly selective approach. This review provides a recent perspective (from the beginning of 2008 to March 2015) on the use of CE for the anal. of explosives. First, a general description of explosives is made, emphasizing the role of sepn. techniques and specifically CE. Next, the most recent works focused on the anal. of explosives by using conventional CE, portable CE and microchip CE are compared and critically discussed. Besides, other emerging techniques for the anal. of explosives are referred and compared to CE results. Finally, future perspectives for the anal. of explosives by CE are proposed.
  9. 9
    Senthamizhan, A.; Celebioglu, A.; Bayir, S.; Gorur, M.; Doganci, E.; Yilmaz, F.; Uyar, T. Highly fluorescent pyrene-functional polystyrene copolymer nanofibers for enhanced sensing performance of TNT. ACS Appl. Mater. Interfaces 2015, 7 (38), 21038– 21046,  DOI: 10.1021/acsami.5b07184
    Google Scholar
    9
    Highly Fluorescent Pyrene-Functional Polystyrene Copolymer Nanofibers for Enhanced Sensing Performance of TNT
    Senthamizhan, Anitha; Celebioglu, Asli; Bayir, Sumeyra; Gorur, Mesut; Doganci, Erdinc; Yilmaz, Faruk; Uyar, Tamer
    ACS Applied Materials & Interfaces (2015), 7 (38), 21038-21046CODEN: AAMICK; ISSN:1944-8244. (American Chemical Society)
    A pyrene-functional polystyrene copolymer was prepd. via 1,3-dipolar cycloaddn. reaction (Sharpless-type click reaction) between azide-functional styrene copolymer and 1-ethynylpyrene. Subsequently, nanofibers of pyrene-functional polystyrene copolymer were obtained by using electrospinning technique. The nanofibers thus obtained, found to preserve their parent fluorescence nature, confirmed the avoidance of aggregation during fiber formation. The trace detection of trinitrotoluene (TNT) in water with a detection limit of 5 nM was demonstrated, which is much lower than the max. allowable limit set by the U.S. Environmental Protection Agency. Interestingly, the sensing performance was found to be selective toward TNT in water, even in the presence of higher concns. of toxic metal pollutants such as Cd2+, Co2+, Cu2+, and Hg2+. The enhanced sensing performance was found to be due to the enlarged contact area and intrinsic nanoporous fiber morphol. Effortlessly, the visual colorimetric sensing performance can be seen by naked eye with a color change in a response time of few seconds. Furthermore, vapor-phase detection of TNT was studied, and the results are discussed herein. In terms of practical application, electrospun nanofibrous web of pyrene-functional polystyrene copolymer has various salient features including flexibility, reproducibility, and ease of use, and visual outputs increase their value and add to their advantage.
  10. 10
    Wu, X.; Hang, H.; Li, H.; Chen, Y.; Tong, H.; Wang, L. Water-dispersible hyperbranched conjugated polymer nanoparticles with sulfonate terminal groups for amplified fluorescence sensing of trace TNT in aqueous solution. Mater. Chem. Front. 2017, 1 (9), 1875– 1880,  DOI: 10.1039/C7QM00173H
    Google Scholar
    10
    Water-dispersible hyperbranched conjugated polymer nanoparticles with sulfonate terminal groups for amplified fluorescence sensing of trace TNT in aqueous solution
    Wu, Xiaofu; Hang, Hao; Li, Hua; Chen, Yonghong; Tong, Hui; Wang, Lixiang
    Materials Chemistry Frontiers (2017), 1 (9), 1875-1880CODEN: MCFAC5; ISSN:2052-1537. (Royal Society of Chemistry)
    Conjugated polymers (CPs) have been recognized as promising fluorescent sensing materials for 2,4,6-trinitrotoluene (TNT) vapor. However, their applications for TNT detection in aq. soln. are restricted because of their low sensitivity (detection limits >90 nM). Here we report highly sensitive detection of TNT by water-dispersible hyperbranched conjugated polymer nanoparticles (HCPN-S) with hydrophobic CP cores and hydrophilic sulfonate terminal groups. Based on efficient TNT encapsulation by numerous hydrophobic cavities inside the hyperbranched CP core, HCPN-S exhibits a quenching const. of 1.21 × 106 M-1, two to three orders of magnitude higher than those of CP analogs, allowing amplified detection of TNT with a detection limit of 0.8 ppb (3.7 nM), which is the best result for CP-based fluorescent sensors for TNT detection in water reported so far. Furthermore, HCPN-S can selectively detect TNT even in the presence of 2,4,6-trinitrophenol and other nitro compds.
  11. 11
    Xiao, S. J.; Zhao, X. J.; Hu, P. P.; Chu, Z. J.; Huang, C. Z.; Zhang, L. Highly photoluminescent molybdenum oxide quantum dots: one-pot synthesis and application in 2,4,6-trinitrotoluene determination. ACS Appl. Mater. Interfaces 2016, 8 (12), 8184– 8191,  DOI: 10.1021/acsami.5b11316
    Google Scholar
    11
    Highly Photoluminescent Molybdenum Oxide Quantum Dots: One-Pot Synthesis and Application in 2,4,6-Trinitrotoluene Determination
    Xiao, Sai Jin; Zhao, Xiao Jing; Hu, Ping Ping; Chu, Zhao Jun; Huang, Cheng Zhi; Zhang, Li
    ACS Applied Materials & Interfaces (2016), 8 (12), 8184-8191CODEN: AAMICK; ISSN:1944-8244. (American Chemical Society)
    As a well-studied transition-metal semiconductor material, MoOx has a wider band gap than molybdenum disulfide (MoS2), and its property varies dramatically for the existence of several different allotropes and suboxide phases of molybdenum oxides (MoOx, x < 3). In this manuscript, a one-pot method possessing the advantages of one pot, easily prepd., rapid, and environmentally friendly, has been developed for facile synthesis of highly photoluminescent MoOx quantum dots (MoOx QDs), in which com. molybdenum disulfide (MoS2) powder and hydrogen peroxide (H2O2) are employed as the precursor and oxidant, resp. The obtained MoOx QDs can be further utilized as an efficient photoluminescent probe, and a new turn-off sensor is developed for 2,4,6-trinitrotoluene (TNT) detn. based on the fact that the photoluminescence of MoOx QDs can be quenched by the Meisenheimer complexes formed in the strong alkali soln. through the inner filter effect (IFE). Under the optimal conditions, the decreased photoluminescence of MoOx QDs shows a good linear relationship to the concn. of TNT ranging from 0.5 to 240.0 μM, and the limit of detection was 0.12 μM (3σ/k). With the present turn-off sensor, TNT in river water samples can be rapidly and selectively detected without tedious sample pretreatment processes.
  12. 12
    Alizadeh, N.; Akbarinejad, A.; Ghoorchian, A. Photophysical diversity of water-soluble fluorescent conjugated polymers induced by surfactant stabilizers for rapid and highly selective determination of 2,4,6-trinitrotoluene traces. ACS Appl. Mater. Interfaces 2016, 8 (37), 24901– 24908,  DOI: 10.1021/acsami.6b08577
    Google Scholar
    12
    Photophysical Diversity of Water-Soluble Fluorescent Conjugated Polymers Induced by Surfactant Stabilizers for Rapid and Highly Selective Determination of 2,4,6-Trinitrotoluene Traces
    Alizadeh, Naader; Akbarinejad, Alireza; Ghoorchian, Arash
    ACS Applied Materials & Interfaces (2016), 8 (37), 24901-24908CODEN: AAMICK; ISSN:1944-8244. (American Chemical Society)
    The increasing application of fluorescence spectroscopy in development of reliable sensing platforms has triggered a lot of research interest for the synthesis of advanced fluorescent materials. Herein, we report a simple, low-cost strategy for the synthesis of a series of water-sol. conjugated polymer nanoparticles with diverse emission range using cationic (hexadecyltrimethylammonium bromide, CTAB), anionic (sodium dodecylbenzenesulfonate, SDBS), and nonionic (TX114) surfactants as the stabilizing agents. The role of surfactant type on the photophys. and sensing properties of resultant polymers has been investigated using dynamic light scattering (DLS), FT-IR, UV-vis, fluorescence, and energy dispersive X-ray (EDS) spectroscopies. The results show that the surface polarity, size, and spectroscopic and sensing properties of conjugated polymers could be well controlled by the proper selection of the stabilizer type. The fluorescent conjugated polymers exhibited fluorescence quenching toward nitroarom. compds. Further studies on the fluorescence properties of conjugated polymers revealed that the emission of the SDBS stabilized polymer, N-methylpolypyrrole-SDBS (NMPPY-SDBS), is strongly quenched by 2,4,6-trinitrotoluene mol. with a large Stern-Volmer const. of 59,526 M-1 and an excellent detection limit of 100 nM. UV-vis and cyclic voltammetry measurements unveiled that fluorescence quenching occurs through a charge transfer mechanism between electron rich NMPPY-SDBS and electron deficient 2,4,6-trinitrotoluene mols. Finally, the as-prepd. conjugated polymer and approach were successfully applied to the detn. of 2,4,6-trinitrotoluene in real water samples.
  13. 13
    Venkatramaiah, N.; Firmino, A. D. G.; Almeida Paz, F. A.; Tomé, J. P. C. Fast detection of nitroaromatics using phosphonate pyrene motifs as dual chemosensors. Chem. Commun. 2014, 50 (68), 9683– 9686,  DOI: 10.1039/C4CC03980G
    Google Scholar
    13
    Fast detection of nitroaromatics using phosphonate pyrene motifs as dual chemosensors
    Venkatramaiah, N.; Firmino, Ana D. G.; Almeida Paz, Filipe A.; Tome, Joao P. C.
    Chemical Communications (Cambridge, United Kingdom) (2014), 50 (68), 9683-9686CODEN: CHCOFS; ISSN:1359-7345. (Royal Society of Chemistry)
    A new class of dual fluorescent chemosensors (I, II) for nitroarom. compds. (NACs) based on phosphonated pyrene derivs. is reported, showing high selectivity towards trinitrotoluene (TNT). The strong intermol. interactions (π-π stacking and hydrogen bonding) allow high fluorescence quenching with visual detection in short response times.
  14. 14
    Yang, J.; Wang, Z.; Hu, K.; Li, Y.; Feng, J.; Shi, J.; Gu, J. Rapid and specific aqueous-Phase detection of nitroaromatic explosives with inherent porphyrin recognition sites in metal–organic frameworks. ACS Appl. Mater. Interfaces 2015, 7 (22), 11956– 11964,  DOI: 10.1021/acsami.5b01946
    Google Scholar
    14
    Rapid and Specific Aqueous-Phase Detection of Nitroaromatic Explosives with Inherent Porphyrin Recognition Sites in Metal-Organic Frameworks
    Yang, Jian; Wang, Zhe; Hu, Kaili; Li, Yongsheng; Feng, Jianfang; Shi, Jianlin; Gu, Jinlou
    ACS Applied Materials & Interfaces (2015), 7 (22), 11956-11964CODEN: AAMICK; ISSN:1944-8244. (American Chemical Society)
    Development of a rapid and effective method for the detection of 2,4,6-trinitrotoluene (TNT) in aq. phase has attracted great attention. In this work, the fluorescent porphyrin-based metal-org. frameworks (MOFs) of PCN-224 were successfully exploited as a fluorescent probe for the rapid and selective TNT detection in water media. This strategy combined the advantages of fluorescent porphyrin mols. and porous MOFs, which not only overcame the aggregation of hydrophobic tetrakis(4-carboxyphenyl)porphyrin (TCPP) recognition sites but also promoted TNT to interact with recognition sites in virtue of the high surface and intrinsic open structure of MOFs. As a result, a rapid response time of as short as 30 s was obtained for the elaborated fluorescent probe. Meanwhile, the bright red emission of porphyrin units in PCN-224 could be proportionally quenched in correlation with the applied TNT level through the formation of TNT-TCPP complex in the ground state. The specificity of the employed sensory platform for TNT recognition was scarcely affected by other possible coexistent interfering species. Furthermore, this fluorescent PCN-224 probe presented a much higher quenching efficiency for TNT than other structurally similar nitroarom. compds. and was successfully applied for the quant. detection of TNT in the mixed nitroarom. explosive samples. This prefigured their great potentials of practical TNT detection in water media for public safety and security.
  15. 15
    Yang, J.-S.; Swager, T. M. Fluorescent porous polymer films as TNT chemosensors: electronic and structural effects. J. Am. Chem. Soc. 1998, 120 (46), 11864– 11873,  DOI: 10.1021/ja982293q
    Google Scholar
    15
    Fluorescent Porous Polymer Films as TNT Chemosensors: Electronic and Structural Effects
    Yang, Jye-Shane; Swager, Timothy M.
    Journal of the American Chemical Society (1998), 120 (46), 11864-11873CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
    The synthesis, spectroscopy, and fluorescence quenching behavior of pentiptycene-derived phenyleneethynylene polymers, 1-3, are reported. The incorporation of rigid three-dimensional pentiptycene moieties into conjugated polymer backbones offers several design advantages for solid-state (thin film) fluorescent sensory materials. First, they prevent π-stacking of the polymer backbones and thereby maintain high fluorescence quantum yields and spectroscopic stability in thin films. Second, reduced interpolymer interactions dramatically enhance the soly. of polymers 1-3 relative to other poly(phenyleneethynylenes). Third, the cavities generated between adjacent polymers are sufficiently large to allow diffusion of small org. mols. into the films. These advantages are apparent from comparisons of the spectroscopic and fluorescence quenching behavior of 1-3 to a related planar electron-rich polymer 4. The fluorescence attenuation (quenching) of polymer films upon exposure to analytes depends on several factors, including the exergonicity of electron transfer from excited polymer to analytes, the binding strength (polymer-analyte interactions), the vapor pressure of the analyte, and the rates of diffusion of the analytes in the polymer films. Films of 1-3 are particularly selective toward nitro-arom. compds. The dependence of fluorescence quenching on film thickness provides an addnl. criterion for the differentiation of nitro-arom. compds. from other species, such as quinones. In short, thinner films show a larger response to nitro-arom. compds., but show a lower response to quinones. Such differences are explained in terms of polymer-analyte interactions, which appear to be electrostatic in nature. The rapid fluorescence response (quenching) of the spin-cast films of 1-3 to nitro-contg. compds. qualifies these materials as promising TNT chemosensory materials.
  16. 16
    Nie, H.; Zhao, Y.; Zhang, M.; Ma, Y.; Baumgarten, M.; Müllen, K. Detection of TNT explosives with a new fluorescent conjugated polycarbazole polymer. Chem. Commun. 2011, 47 (4), 1234– 1236,  DOI: 10.1039/C0CC03659E
    Google Scholar
    16
    Detection of TNT explosives with a new fluorescent conjugated polycarbazole polymer
    Nie, Heran; Zhao, Yang; Zhang, Ming; Ma, Yuguang; Baumgarten, Martin; Muellen, Klaus
    Chemical Communications (Cambridge, United Kingdom) (2011), 47 (4), 1234-1236CODEN: CHCOFS; ISSN:1359-7345. (Royal Society of Chemistry)
    A novel fluorescent poly(2,7-carbazole) with a 4-[tris-(4-octyloxyphenyl)methyl]phenyl side chain is used to detect the explosive compds. TNT and DNT. It shows high recycled fluorescence quenching sensitivity, which is due to its strong electron donating ability and weaker interaction between the polymer chains caused by the bulky side chain.
  17. 17
    Xu, B.; Wu, X.; Li, H.; Tong, H.; Wang, L. Selective detection of TNT and picric acid by conjugated polymer film sensors with donor–acceptor architecture. Macromolecules 2011, 44 (13), 5089– 5092,  DOI: 10.1021/ma201003f
    Google Scholar
    17
    Selective Detection of TNT and Picric Acid by Conjugated Polymer Film Sensors with Donor-Acceptor Architecture
    Xu, Bowei; Wu, Xiaofu; Li, Haibo; Tong, Hui; Wang, Lixiang
    Macromolecules (Washington, DC, United States) (2011), 44 (13), 5089-5092CODEN: MAMOBX; ISSN:0024-9297. (American Chemical Society)
    A strong donor-acceptor polymer P1 and two donor-only polymers P2 and P3 are designed and synthesized on the basis of the rational anal. of the electrostatic potential and the LUMO distribution for highly selective and sensitive detection of TNT and picric acid in aq. solns., resp. Although their emission in soln. states is very poor, spin-coating films of these AIE-active polymers exhibit bright emission. For the P1 film, the Stern-Volmer quenching const., Ksv of TNT (1.2 ×. 105 M-1) is almost 2 orders higher than that of picric acid (1.8 × 103 M-1), and the detection limit of TNT is about 23 ppb, while the emission of the P3 film can be selectively quenched by the picric acid with the Ksv const. 2.8 × 104 M-1 and the detection limit 2 ppb. These quenching effects of both TNT and picric acid on the P1 and P3 films are found to be reversible. In addn., it was also demonstrated that the emission of P1 and P3 films could be efficiently quenched by TNT and DNT vapors.
  18. 18
    He, G.; Yan, N.; Yang, J.; Wang, H.; Ding, L.; Yin, S.; Fang, Y. Pyrene-containing conjugated polymer-based fluorescent films for highly sensitive and selective sensing of TNT in aqueous medium. Macromolecules 2011, 44 (12), 4759– 4766,  DOI: 10.1021/ma200953s
    Google Scholar
    18
    Pyrene-Containing Conjugated Polymer-Based Fluorescent Films for Highly Sensitive and Selective Sensing of TNT in Aqueous Medium
    He, Gang; Yan, Ni; Yang, Jiayu; Wang, Hongyue; Ding, Liping; Yin, Shiwei; Fang, Yu
    Macromolecules (Washington, DC, United States) (2011), 44 (12), 4759-4766CODEN: MAMOBX; ISSN:0024-9297. (American Chemical Society)
    Two poly(pyrene-co-phenyleneethynylene)s of different compns. (PyPE-1 and PyPE-2) were synthesized and characterized. The two polymers had been casted, sep., onto glass plate surfaces to fabricate films (film 1, film 2) for sensing performance studies. The fluorescence emissions of the two films are sensitive to the presence of 2,4,6-trinitrotoluene (TNT) in aq. phase. TNT shows little effect upon the emission of the parent polymer, poly(phenyleneethynylene) (PPE). The difference was explained by considering (1) the π-π interaction between pyrene moieties contained in the copolymers and the analyte, TNT, mols., and (2) more suitable matching of the LUMOs of the pyrene-contg. conjugated polymers with that of TNT mols. Further the sensing is reversible and rarely encounters interference from commonly found compds., including other nitroaroms. (NACs). Fluorescence lifetime measurements revealed that the quenching is static in nature. The smart performance of the films and the easiness of their prepn. guarantee that the films may be developed into sensor devices for the supersensitive detection of TNT in groundwater or seawater.
  19. 19
    Lee, J. Y.; Root, H. D.; Ali, R.; An, W.; Lynch, V. M.; Bähring, S.; Kim, I. S.; Sessler, J. L.; Park, J. S. Ratiometric turn-On fluorophore displacement ensembles for nitroaromatic explosives detection. J. Am. Chem. Soc. 2020, 142 (46), 19579– 19587,  DOI: 10.1021/jacs.0c08106
    Google Scholar
    19
    Ratiometric Turn-On Fluorophore Displacement Ensembles for Nitroaromatic Explosives Detection
    Lee, Ji Yoon; Root, Harrison D.; Ali, Rashid; An, Won; Lynch, Vincent M.; Bahring, Steffen; Kim, In Su; Sessler, Jonathan L.; Park, Jung Su
    Journal of the American Chemical Society (2020), 142 (46), 19579-19587CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
    There is a recognized need in the area of explosives detection for fluorescence-based sensing systems that are capable of not only producing a turn-on response but also generating a distinctive spectral signature for a given analyte. Here, several supramol. ensembles are reported displaying efficient fluorophore displacement that give rise to an increase in fluorescence intensity upon exposure to various nitroarom. compds. The synthetic supramol. constructs in question consist of a tetrathiafulvalene (TTF)-based pyrrolic macrocycle, benzo-TTF-calix[4]pyrrole (Bz-TTF-C4P), and fluorescent dyes, monomeric or dimeric naphthalenediimide (NDI) and perylenediimide (PDI) derivs., as well as chloride or hexafluorophosphate (PF6-) salts of rhodamine 6G (Rh-6G). In chloroform soln., these assemblies exist in the form of discrete supramol. complexes or oligomeric aggregates depending on the specific dye combinations in question. Each ensemble was tested as a potential explosive-responsive fluorescence indicator displacement assay (FIDA) by challenging it with a series of di- and trinitroarom. compds. and examg. the change in fluorescence spectral characteristics. Upon addn. of nitroarom. compds. (NACs), either a "turn-on" or a "turn-off" fluorescent response was obsd. depending on the nature of the constituent fluorophore and, where applicable, the counteranion. The FIDAs based on the PDI derivs. were found to display not only a ratiometric fluorescence enhancement but also analyte-dependent spectral changes when treated with NACs. The NAC-induced fluorescence spectral response of each ensemble was rationalized on the basis of various soln.-phase spectroscopic studies, as well as single-crystal X-ray diffraction analyses.
  20. 20
    Climent, E.; Biyikal, M.; Gröninger, D.; Weller, M. G.; Martínez-Máñez, R.; Rurack, K. Multiplexed Detection of Analytes on Single Test Strips with antibody-gated indicator-releasing mesoporous nanoparticles. Angew. Chem., Int. Ed. 2020, 59 (52), 23862– 23869,  DOI: 10.1002/anie.202009000
    Google Scholar
    20
    Multiplexed Detection of Analytes on Single Test Strips with Antibody-Gated Indicator-Releasing Mesoporous Nanoparticles
    Climent, Estela; Biyikal, Mustafa; Groeninger, Delia; Weller, Michael G.; Martinez-Manez, Ramon; Rurack, Knut
    Angewandte Chemie, International Edition (2020), 59 (52), 23862-23869CODEN: ACIEF5; ISSN:1433-7851. (Wiley-VCH Verlag GmbH & Co. KGaA)
    Rapid testing methods for the use directly at a point of need are expected to unfold their true potential esp. when offering adequate capabilities for the simultaneous measurement of multiple analytes of interest. Considering the unique modularity, high sensitivity, and selectivity of antibody-gated indicator delivery (gAID) systems, a multiplexed assay for three small-mol. explosives (TATP, TNT, PETN) was thus developed, allowing to detect the analytes simultaneously with a single test strip at lower ppb concns. in the liq. phase in <5 min using a fluorescence reader or a smartphone for readout. While the TNT and PETN systems were newly developed here, all the three systems also tolerated harsher matrixes than buffered aq. model solns. Besides a single-track strip, the outstanding modularity of the hybrid biosensor materials in combination with strip-patterning technologies allowed us to obtain a multichannel strip in a straightforward manner, offering comparable anal. performance while allowing to be tailored even more to the user's need.
  21. 21
    Wan, W.-M.; Tian, D.; Jing, Y.-N.; Zhang, X.-Y.; Wu, W.; Ren, H.; Bao, H.-L. NBN-doped conjugated polycyclic aromatic hydrocarbons as an AIEgen class for extremely sensitive detection of explosives. Angew. Chem., Int. Ed. 2018, 57 (47), 15510– 15516,  DOI: 10.1002/anie.201809844
    Google Scholar
    21
    NBN-Doped Conjugated Polycyclic Aromatic Hydrocarbons as an AIEgen Class for Extremely Sensitive Detection of Explosives
    Wan, Wen-Ming; Tian, Di; Jing, Ya-Nan; Zhang, Xiao-Yun; Wu, Wei; Ren, Hao; Bao, Hong-Li
    Angewandte Chemie, International Edition (2018), 57 (47), 15510-15516CODEN: ACIEF5; ISSN:1433-7851. (Wiley-VCH Verlag GmbH & Co. KGaA)
    A simple and efficient synthesis of NBN-doped conjugated polycyclic arom. hydrocarbons (such as diazaborinines) has been accomplished by a catalyst-free intermol. dehydration reaction at room temp. between boronic acid and diamine moieties with yields up to 99 %. Polycyclic arom. hydrocarbons with a six-membered NBN ring are a new class of aggregation-induced emissive luminogens. Extremely sensitive detection of ppb levels of TNT by Ph naphthodiazaborinine is straightforward. Visual detection of TNT is illustrated by fabrication of TNT test strips, which can detect as little as 100 ng of TNT powder. This simple and sensitive detection of TNT has potential applications in the area of public safety and security against terrorist activities.
  22. 22
    Tanwar, A. S.; Hussain, S.; Malik, A. H.; Afroz, M. A.; Iyer, P. K. Inner filter effect based selective detection of nitroexplosive-picric acid in aqueous solution and solid support using conjugated polymer. ACS Sens. 2016, 1 (8), 1070– 1077,  DOI: 10.1021/acssensors.6b00441
    Google Scholar
    22
    Inner Filter Effect Based Selective Detection of Nitroexplosive-Picric Acid in Aqueous Solution and Solid Support Using Conjugated Polymer
    Tanwar, Arvin Sain; Hussain, Sameer; Malik, Akhtar Hussain; Afroz, Mohammad Adil; Iyer, Parameswar Krishnan
    ACS Sensors (2016), 1 (8), 1070-1077CODEN: ASCEFJ; ISSN:2379-3694. (American Chemical Society)
    A new polyfluorene deriv., poly[4,4'-(((2-phenyl-9H-fluorene-9,9-diyl)bis(hexane-6,1-diyl))bis(oxy))dianiline)] (PFAM) was synthesized via the Suzuki coupling polymn. method in high yields for the rapid and specific recognition of nitroexplosive picric acid (PA) at 22.9 pg level on solid support using paper strips and at 13.2 ppb level in aq. soln. The polymer PFAM was well-characterized by means of NMR, UV-vis, fluorescence, time-resolved photoluminescence (TRPL) spectroscopy, and cyclic voltammetry. The amplified signal response exclusively for PA was achieved via a strong inner filter effect (IFE), a phenomenon different from the widely reported ground-state charge transfer and/or Forster resonance energy transfer (FRET) based probes for nitroaroms. detection. Pendant amine groups attached on the side chains of PFAM provide enhanced sensitivity and exceptional selectivity via protonation assisted photoinduced electron transfer (PET) even in the presence of most common interfering nitroexplosives, as well as other analytes usually found in natural water. Thus, the PFAM based platform was demonstrated for monitoring traces of PA at very low levels even in competitive environment in soln. as well as solid state.
  23. 23
    Kim, H. N.; Guo, Z.; Zhu, W.; Yoon, J.; Tian, H. Recent progress on polymer-based fluorescent and colorimetric chemosensors. Chem. Soc. Rev. 2011, 40 (1), 79– 93,  DOI: 10.1039/C0CS00058B
    Google Scholar
    23
    Recent progress on polymer-based fluorescent and colorimetric chemosensors
    Kim, Ha Na; Guo, Zhiqian; Zhu, Weihong; Yoon, Juyoung; Tian, He
    Chemical Society Reviews (2011), 40 (1), 79-93CODEN: CSRVBR; ISSN:0306-0012. (Royal Society of Chemistry)
    A review. Recently, fluorescent or colorimetric chemosensors based on polymers have attracted great attention due to several important advantages, such as their simplicity of use, signal amplification, easy fabrication into devices, and combination of different outputs, etc. This tutorial review will cover polymer-based optical chemosensors from 2007 to 2010.
  24. 24
    Thomas, S. W.; Joly, G. D.; Swager, T. M. Chemical sensors based on amplifying fluorescent conjugated polymers. Chem. Rev. 2007, 107 (4), 1339– 1386,  DOI: 10.1021/cr0501339
    Google Scholar
    24
    Chemical sensors based on amplifying fluorescent conjugated polymers
    Thomas, Samuel W., III; Joly, Guy D.; Swager, Timothy M.
    Chemical Reviews (Washington, DC, United States) (2007), 107 (4), 1339-1386CODEN: CHREAY; ISSN:0009-2665. (American Chemical Society)
    A review. In this review the authors restrict the discussions to purely fluorescence-based methods using conjugated polymers. Amplification, small ion sensing using amplifying fluorescent conjugated polymers (AFPs), AFPs for detection of explosives, conjugated polyelectrolytes as biosensors, AFPs for detection of small biomols., proteins, and DNA are discussed.
  25. 25
    Feng, L.; Li, H.; Qu, Y.; Lü, C. Detection of TNT based on conjugated polymer encapsulated in mesoporous silica nanoparticles through FRET. Chem. Commun. 2012, 48 (38), 4633– 4635,  DOI: 10.1039/c2cc16115j
    Google Scholar
    25
    Detection of TNT based on conjugated polymer encapsulated in mesoporous silica nanoparticles through FRET
    Feng, Lijuan; Li, Hui; Qu, Ying; Lue, Changli
    Chemical Communications (Cambridge, United Kingdom) (2012), 48 (38), 4633-4635CODEN: CHCOFS; ISSN:1359-7345. (Royal Society of Chemistry)
    Amine-functionalized mesoporous silica nanoparticles contg. poly(p-phenylenevinylene) provide a facile strategy to detect TNT through fluorescence resonance energy transfer (FRET). The obsd. linear fluorescence intensity change allows the quant. detection of TNT with the detection limit of 6 × 10-7 M.
  26. 26
    Novotney, J. L.; Dichtel, W. R. Conjugated porous polymers for TNT vapor detection. ACS Macro Lett. 2013, 2 (5), 423– 426,  DOI: 10.1021/mz4000249
    Google Scholar
    26
    Conjugated Porous Polymers For TNT Vapor Detection
    Novotney, Jennifer L.; Dichtel, William R.
    ACS Macro Letters (2013), 2 (5), 423-426CODEN: AMLCCD; ISSN:2161-1653. (American Chemical Society)
    A conjugated porous polymer (CPP) that exhibits fluorescence quenching when exposed to TNT vapor was synthesized via a Sonaogashira cross-coupling reaction. Two polymn. solvents, DMF and PhMe, and two activation procedures, evacuation and lyophilization, were evaluated to optimize the response of the CPP to TNT vapor. Key differences in surface area and absorption were seen as a function of polymn. solvent and activation procedure. The polymer synthesized in DMF and activated by lyophilization had the highest surface area and the strongest response to TNT vapor. This paper demonstrates the importance of growth and activation conditions in optimizing the porosity and sensing performance of CPPs.
  27. 27
    Adil, L. R.; Gopikrishna, P.; Iyer, P. K. Receptor-free detection of picric acid: a new structural approach for designing aggregation-induced emission probes. ACS Appl. Mater. Interfaces 2018, 10 (32), 27260– 27268,  DOI: 10.1021/acsami.8b07019
    Google Scholar
    27
    Receptor-Free Detection of Picric Acid: A New Structural Approach for Designing Aggregation-Induced Emission Probes
    Adil, Laxmi Raman; Gopikrishna, Peddaboodi; Krishnan Iyer, Parameswar
    ACS Applied Materials & Interfaces (2018), 10 (32), 27260-27268CODEN: AAMICK; ISSN:1944-8244. (American Chemical Society)
    A pristine aggregation-induced enhanced emission (AIEE) active monomer 2,5-bis((E)-4-bromostyryl)-3,4-diphenylthiophene (TPBZ) and its copolymer (PFTPBZ) with 9,9-dioctylfluorene-2,7-diboronic acid bis(1,3-propandiol) ester were synthesized via Suzuki coupling polymn. PFTPBZ that is devoid of any receptor showed AIEE property and demonstrated excellent and selective fluorometric recognition of 2,4,6-trinitrotoluene (TNT) in aggregated state (aq. medium) and picric acid (PA) in aggregated state and soln. state (org. solvent) as well as in vapor phase via PFTPBZ dip-coated Whatman filter paper on a solid-phase platform in 1.86 ng level (naked eye). Limit of detection (LOD) for TNT in 95% water fraction (fw) was 53.74 × 10-6 M, and at 40% fw, it was 14.26 × 10-7 M. PA detection in THF soln. was possible with a LOD of 28.16 × 10-7 M, 95% fw with LOD of 10.47 × 10-6 M, and in 40% fw with LOD of 47.39 × 10-8 M. As a unique example of structural design, the probe PFTPBZ surprisingly possesses no receptor, yet remarkably high selectivity was achieved via Forster resonance energy transfer (FRET) and photoinduced electron transfer from the copolymer PFTPBZ to PA and TNT. Detection of PA in the presence of various metal analytes and inorg. acids in real water samples (lakes, rivers, and sea water) was also demonstrated using this concept of receptor-free conjugated polymer probe.
  28. 28
    Tanwar, A. S.; Adil, L. R.; Afroz, M. A.; Iyer, P. K. Inner filter effect and resonance energy transfer based attogram level detection of nitroexplosive picric acid using dual emitting cationic conjugated polyfluorene. ACS Sens. 2018, 3 (8), 1451– 1461,  DOI: 10.1021/acssensors.8b00093
    Google Scholar
    28
    Inner Filter Effect and Resonance Energy Transfer Based Attogram Level Detection of Nitroexplosive Picric Acid Using Dual Emitting Cationic Conjugated Polyfluorene
    Tanwar, Arvin Sain; Adil, Laxmi Raman; Afroz, Mohammad Adil; Iyer, Parameswar Krishnan
    ACS Sensors (2018), 3 (8), 1451-1461CODEN: ASCEFJ; ISSN:2379-3694. (American Chemical Society)
    A novel conjugated cationic polyfluorene (polyelectrolyte) deriv., PFBT, was developed by means of simple and cost-effective oxidative coupling polymn. method. PFBT displayed dual state emission in DMSO as well as in water, a characteristic phenomenon of polyfluorene homopolymers, and tested for nitroexplosive analytes detection to observe a remarkable fluorescence quenching response for picric acid (PA) in the both solvents. The polymer PFBT demonstrated substantial selectivity and ultrasensitivity toward nitroexplosive PA in both the solvents (DMSO and H2O) with exceptional quenching const. values of 2.69 × 104 and 2.18 × 105 M-1 and a ultralow limit of detection of 92.7 nM (21.23 ppb) and 0.19 nM (43.53 ppt) in resp. solvents. Furthermore, economical portable test strip devices were prepd. for easy and fast on-site PA sensing, which can detect up to 0.22 ag level of PA. PA sensing in vapor phase was also established, that could detect up to 42.6 ppb level of PA vapors. Interestingly, the mechanism of sensing in DMSO solvent was attributed to substantial inner filter effect and photoinduced electron transfer, while in H2O the sensing occurs via possible resonance energy transfer and photoinduced electron transfer, which is exceptional and not reported earlier for a single probe.
  29. 29
    Tanwar, A. S.; Patidar, S.; Ahirwar, S.; Dehingia, S.; Iyer, P. K. Receptor free” inner filter effect based universal sensors for nitroexplosive picric acid using two polyfluorene derivatives in the solution and solid states. Analyst 2019, 144 (2), 669– 676,  DOI: 10.1039/C8AN01970C
    Google Scholar
    29
    "Receptor free" inner filter effect based universal sensors for nitroexplosive picric acid using two polyfluorene derivatives in the solution and solid states
    Tanwar, Arvin Sain; Patidar, Sourabh; Ahirwar, Saurabh; Dehingia, Sourav; Iyer, Parameswar Krishnan
    Analyst (Cambridge, United Kingdom) (2019), 144 (2), 669-676CODEN: ANALAO; ISSN:0003-2654. (Royal Society of Chemistry)
    Two receptor-free blue fluorescent conjugated polymers (CPs) of fluorene namely 9,9-bis(6-bromohexyl)-2-phenyl-9H-fluorene (PF1) and 9,9-bis(6-bromohexyl)-9H-fluorene (PF2) were synthesized using Suzuki cross coupling polymn. and oxidative coupling polymn. methods in high yields and well characterized by gel permeable chromatog., NMR, UV-vis, fluorescence and time-resolved photoluminescence (TRPL) spectroscopy. Both CPs explicitly recognized nitroexplosive picric acid (PA) and displayed a fluorescence quenching response in soln. and on a solid support via the inner filter effect (IFE) mechanism. Both CPs were highly selective and sensitive towards PA with high quenching const. values (Ksv) of 5.1 × 104 M-1 and 5.0 × 104 M-1 and remarkably low limit of detection (LOD) values of 110 nM and 219 nM. Contact mode detection of PA was also accomplished using economical and transportable fluorescent paper test strip devices for on-site sensing, which detect a min. of 22.9 fg of PA. The IFE mechanism for PA sensing (or for other analytes) is an interesting concept that can detect PA by just having blue fluorescence. Therefore, careful expts. for IFE correction were performed herein for PA detection to observe ∼77% suppression efficiency due to the IFE. These studies provide fundamentally important information on the IFE based mechanism for the detection of various analytes.
  30. 30
    Hussain, S.; Malik, A. H.; Afroz, M. A.; Iyer, P. K. Ultrasensitive detection of nitroexplosive – picric acid via a conjugated polyelectrolyte in aqueous media and solid support. Chem. Commun. 2015, 51 (33), 7207– 7210,  DOI: 10.1039/C5CC02194D
    Google Scholar
    30
    Ultrasensitive detection of nitroexplosive - picric acid via a conjugated polyelectrolyte in aqueous media and solid support
    Hussain, Sameer; Malik, Akhtar Hussain; Afroz, Mohammad Adil; Iyer, Parameswar Krishnan
    Chemical Communications (Cambridge, United Kingdom) (2015), 51 (33), 7207-7210CODEN: CHCOFS; ISSN:1359-7345. (Royal Society of Chemistry)
    Picric acid (PA) detection at parts per trillion (ppt) levels is achieved by a conjugated polyelectrolyte (PMI) in 100% aq. media and on a solid platform using paper strips and chitosan (CS) films. The unprecedented selectivity is accomplished via combination of ground state charge transfer and resonance energy transfer (RET) facilitated by favorable electrostatic interactions.
  31. 31
    Lakowicz, J. R. Principles of Fluorescence Spectrosopy, 3rd ed.; Springer: Singapore, 2010.
    Google Scholar
    There is no corresponding record for this reference.
  32. 32
    Tanwar, A. S.; Meher, N.; Adil, L. R.; Iyer, P. K. Stepwise elucidation of fluorescence based sensing mechanisms considering picric acid as a model analyte. Analyst 2020, 145 (14), 4753– 4767,  DOI: 10.1039/D0AN00732C
    Google Scholar
    32
    Stepwise elucidation of fluorescence based sensing mechanisms considering picric acid as a model analyte
    Tanwar, Arvin Sain; Meher, Niranjan; Adil, Laxmi Raman; Iyer, Parameswar Krishnan
    Analyst (Cambridge, United Kingdom) (2020), 145 (14), 4753-4767CODEN: ANALAO; ISSN:0003-2654. (Royal Society of Chemistry)
    A review. In most of the sensing systems, specific detection mechanisms are involved during the detection process for a certain analyte irresp. of probes. However, unlike that of various sensing analytes, the detection of the highly toxic and explosive picric acid (PA) analyte was found to involve significant types of distinct sensing mechanisms depending on the nature of probes. Moreover, in the past five years, apart from the plethora of fluorescent probes designed, a no. of unique org. small mols. and polymers have been strategically developed at our lab. for the detection of PA, wherein the involvement of several diverse mechanisms along with a few new mechanisms depending on the electronic and photophys. properties of the probes has been unveiled. This involvement of several distinct mechanisms for the detection of PA motivated us to compile a step-by-step guide for the elucidation of the fluorescence sensing mechanism by taking PA as a model analyte. This "tutorial review" summarizes all the common sensing mechanisms involved for the detection of PA hitherto and provides a step-by-step guide to design expts. for the elucidation of sensing mechanisms for any newly designed sensing system. In addn. to the appropriate classification of mechanisms involved for the fluorescence sensing of PA using various fluorescent systems developed at our lab., this tutorial review also includes most other possible mechanistic approaches studied previously. The present tutorial also provides a very unique method of a flow chart, which could help readers to elucidate the likely sensing mechanism via stepwise exptl. and theor. studies. Apart from the elucidation of the sensing mechanism for PA, this review presents an easy and distinct approach for the identification of all the involved mechanisms that would be of primary concern in the detection process of any analyte and could accurately help researchers in the easy and quick elucidation of sensing mechanisms in any kind of fluorophore-analyte system.
  33. 33
    Xu, S.; Lu, H.; Li, J.; Song, X.; Wang, A.; Chen, L.; Han, S. Dummy Molecularly Imprinted Polymers-Capped CdTe Quantum Dots for the Fluorescent Sensing of 2,4,6-Trinitrotoluene. ACS Appl. Mater. Interfaces 2013, 5 (16), 8146– 8154,  DOI: 10.1021/am4022076
    Google Scholar
    33
    Dummy Molecularly Imprinted Polymers-Capped CdTe Quantum Dots for the Fluorescent Sensing of 2,4,6-Trinitrotoluene
    Xu, Shoufang; Lu, Hongzhi; Li, Jinhua; Song, Xingliang; Wang, Aixiang; Chen, Lingxin; Han, Shaobo
    ACS Applied Materials & Interfaces (2013), 5 (16), 8146-8154CODEN: AAMICK; ISSN:1944-8244. (American Chemical Society)
    Molecularly imprinted polymers (MIPs) with trinitrophenol (TNP) as a dummy template mol. capped with CdTe quantum dots (QDs) were prepd. using 3-aminopropyltriethoxy silane (APTES) as the functional monomer and tetraethoxysilane (TEOS) as the cross linker through a seed-growth method via a sol-gel process (i.e., DMIP@QDs) for the sensing of 2,4,6-trinitrotoluene (TNT) from electron-transfer-induced fluorescence quenching. With the presence and increase of TNT in sample solns., a Meisenheimer complex was formed between TNT and the primary amino groups on the surface of the QDs. The energy of the QDs was transferred to the complex, resulting in the quenching of the QDs and thus decreasing the fluorescence intensity, which allowed the TNT to be sensed optically. DMIP@QDs generated a significantly reduced fluorescent intensity within <10 min upon binding TNT. The fluorescence-quenching fractions of the sensor presented a satisfactory linearity with TNT concns. at 0.8-30 μM, and its limit of detection could reach 0.28 μM. The sensor exhibited distinguished selectivity and a high binding affinity to TNT over its possibly competing mols. of 2,4-dinitrophenol (DNP), 4-nitrophenol (4-NP), phenol, and dinitrotoluene (DNT) because there are more nitro groups in TNT and therefore a stronger electron-withdrawing ability and because it has a high similarity in shape and vol. to TNP. The sensor was successfully applied to det. the amt. of TNT in soil samples, and the av. recoveries of TNT at three spiking levels ranged from 90.3 to 97.8% with relative std. deviations <5.12%. The results provided an effective way to develop sensors for the rapid recognition and detn. of hazardous materials from complex matrixes.
  34. 34
    Zhu, H.; Zhang, H.; Xia, Y. Planar Is Better: Monodisperse Three-Layered MoS2 Quantum Dots as Fluorescent Reporters for 2,4,6-Trinitrotoluene Sensing in Environmental Water and Luggage Cases. Anal. Chem. 2018, 90 (6), 3942– 3949,  DOI: 10.1021/acs.analchem.7b04893
    Google Scholar
    34
    Planar Is Better: Monodisperse Three-Layered MoS2 Quantum Dots as Fluorescent Reporters for 2,4,6-Trinitrotoluene Sensing in Environmental Water and Luggage Cases
    Zhu, Hui; Zhang, Hui; Xia, Yunsheng
    Analytical Chemistry (Washington, DC, United States) (2018), 90 (6), 3942-3949CODEN: ANCHAM; ISSN:0003-2700. (American Chemical Society)
    The authors present a simple but effective fluorescent system for highly sensitive and versatile sensing of 2,4,6-trinitrotoluene (TNT) using few layered planar MoS2 quantum dots (QDs) as reporters. Excitation-independent emitting MoS2 QDs were 1st fabricated by using the proposed ultrasonic-hydrothermal-based top-down method assisted by carbon-free hydroxylamine hydrochloride. The obtained pristine MoS2 QDs were then modified with cysteine for introducing amino groups as TNT binding sites. The as-prepd. MoS2 QDs possess a planar structure, which can more adequately interact with flat arom. TNT mols. due to π-π attraction and decreased steric effects, compared with traditional spherical/quasi-spherical QDs. As a result, they exhibit extremely high sensitivity for TNT sensing (1 nM and 2 ng for soln. and substrate assay, resp.). The common ions contg. in environmental water samples do not interfere with the sensing. Also, the QDs-decorated test paper shows an instantaneous (within 1 min) response to trace amts. of deposited TNT, and the fluorescence quenching can even be well-visualized by the naked eye. Because of favorable anal. performances, the proposed MoS2 QDs-based TNT sensing system has potential applications in both environmental water monitoring and security screening.

Cited By

Click to copy section linkSection link copied!
Citation Statements
Explore this article's citation statements on scite.ai
powered by  Scite

This article is cited by 137 publications.

  1. Shenshen Li, Haihua Wang, Yana Guo, Yu Chen, Huan Chen, Qianqian Wang, Wenbing Kang. Oxygen Inhibition Suppression by Photoinduced Electron Transfer in Oxime Ester/Triarylalkylborate Photoinitiators. Macromolecules 2025, 58 (4) , 2053-2064. https://doi.org/10.1021/acs.macromol.4c02565
  2. Srestha Basu, Adi Hendler-Neumark, Gili Bisker. Role of Oxygen Defects in Eliciting a Divergent Fluorescence Response of Single-Walled Carbon Nanotubes to Dopamine and Serotonin. ACS Nano 2024, 18 (50) , 34134-34146. https://doi.org/10.1021/acsnano.4c10360
  3. Ram Prasad Bhatta, Ajeet Singh, Priya Bhandari, Tirupati Chander Sharma, Pramod Soni, Anindya Datta, Inamur Rahaman Laskar. Pyrene-Based AIEE-Active Vertically Grown Luminescent Material for Selective and Sensitive Detection of TNT Vapor. The Journal of Physical Chemistry C 2024, 128 (43) , 18365-18375. https://doi.org/10.1021/acs.jpcc.4c04823
  4. Bart Limburg. An Extension of the Stern–Volmer Equation for Thermally Activated Delayed Fluorescence (TADF) Photocatalysts. The Journal of Physical Chemistry Letters 2024, 15 (42) , 10495-10499. https://doi.org/10.1021/acs.jpclett.4c02609
  5. Jiko Raut, Rinchen D. Sherpa, Santosh K. Jana, Santi M. Mandal, Sukhendu Mandal, Subhra P. Hui, Prithidipa Sahoo. In Vivo Monitoring of GABA by N-Doped Carbon Quantum Dots. ACS Applied Nano Materials 2024, 7 (19) , 23278-23287. https://doi.org/10.1021/acsanm.4c05097
  6. Matthias Schmitz, Maria-Sophie Bertrams, Arne C. Sell, Felix Glaser, Christoph Kerzig. Efficient Energy and Electron Transfer Photocatalysis with a Coulombic Dyad. Journal of the American Chemical Society 2024, 146 (37) , 25799-25812. https://doi.org/10.1021/jacs.4c08551
  7. Nabajit Barman, Kangkan Jyoti Goswami, Nasrin Sultana, Neelotpal Sen Sarma. Functionalized Borophene Quantum Dots for Fluorescence Sensing of Folic Acid. ACS Applied Nano Materials 2024, 7 (15) , 17351-17363. https://doi.org/10.1021/acsanm.4c02335
  8. Shrodha Mondal, Olivia Sarkar, Jiko Raut, Santi M. Mandal, Ansuman Chattopadhyay, Prithidipa Sahoo. Development of a Nanomarker for In Vivo Monitoring of Dopamine in Plants. ACS Applied Bio Materials 2024, 7 (7) , 4690-4701. https://doi.org/10.1021/acsabm.4c00506
  9. Mohit Kumar Chattopadhyay, Pravat Ghorai, Sourav Datta, Narayan Ch. Jana, Priyabrata Banerjee. First Crystallographic Evidence of Polarity-Assisted Pseudohalides Controllable Heteroaldazine-Based Coordination Polymers: A New Tributary in Low Level Recognition of Explosive from Real-Day Matrices. Crystal Growth & Design 2024, 24 (13) , 5781-5793. https://doi.org/10.1021/acs.cgd.4c00544
  10. Kangkan Jyoti Goswami, Nabajit Barman, Neelotpal Sen Sarma. Reduced Graphene Oxide Quantum Dots-Anchored Biopolymer Composite as Smart Sensor Platform for Fluorescent and Electrical Sensing of Rifampicin. ACS Applied Electronic Materials 2024, 6 (6) , 4030-4042. https://doi.org/10.1021/acsaelm.3c01523
  11. Ali Ibrahim Shkhair, Anju S. Madanan, Susan Varghese, Merin K. Abraham, Geneva Indongo, Greeshma Rajeevan, Arathy B. K, Sara Muneer Abbas, Sony George. Mo(IV) Ion-Modulated BSA-Protected Gold Nanocluster Probe for Fluorescence Turn-On Detection of Trimethylamine N-Oxide (TMAO). ACS Applied Bio Materials 2024, 7 (5) , 3460-3468. https://doi.org/10.1021/acsabm.4c00354
  12. Priyam Ghosh, Parameswar Krishnan Iyer. Conjugated Polyelectrolytes: Illuminating the Path to Neurodegenerative Disorders Detection and Treatment. ACS Applied Materials & Interfaces 2024, 16 (16) , 20034-20054. https://doi.org/10.1021/acsami.3c17890
  13. Aswathy Panalukudiyil Vijayan, Kala Ramakrishnan, Jayasree G Elambalassery. Triazine-Adenine Anchored Porous Organic Polymer: An Integrated Approach as a Fluorescent Sensor and Molecular Sieve for Mercury Ions. ACS Applied Polymer Materials 2024, 6 (7) , 3975-3984. https://doi.org/10.1021/acsapm.3c03233
  14. Anuraj S. Kshirsagar, Katherine A. Koch, Ajay Ram Srimath Kandada, Mahesh K. Gangishetty. Unraveling the Luminescence Quenching Mechanism in Strong and Weak Quantum-Confined CsPbBr3 Triggered by Triarylamine-Based Hole Transport Layers. JACS Au 2024, 4 (3) , 1229-1242. https://doi.org/10.1021/jacsau.4c00083
  15. Kheibar Dashtian, Fatemeh Binabaji, Rouholah Zare-Dorabei. Enhancing On-Skin Analysis: A Microfluidic Device and Smartphone Imaging Module for Real-Time Quantitative Detection of Multianalytes in Sweat. Analytical Chemistry 2023, 95 (44) , 16315-16326. https://doi.org/10.1021/acs.analchem.3c03516
  16. Subhrajyoti Ghosh, Debjit Mal, Srijan Mukherjee, Shyam Biswas. Sustainable Fabrication of an Eco-Friendly, Reusable Chitosan@Cotton@MOF Composite Sensor for 2,4-Dichlorophenoxyacetic Acid Herbicide and Nitroxoline Antibiotic. ACS Sustainable Chemistry & Engineering 2023, 11 (35) , 13179-13186. https://doi.org/10.1021/acssuschemeng.3c03517
  17. Jyoti Korram, Pallavi Koyande, Sayaji Mehetre, Shilpa N. Sawant. Biomass-Derived Carbon Dots as Nanoprobes for Smartphone–Paper-Based Assay of Iron and Bioimaging Application. ACS Omega 2023, 8 (34) , 31410-31418. https://doi.org/10.1021/acsomega.3c03969
  18. Kangkan Jyoti Goswami, Neelotpal Sen Sarma. “Click” Reaction-Mediated Silk Fibroin-Functionalized Thiol-Branched Graphene Oxide Quantum Dots for Smart Sensing of Tetracycline. ACS Omega 2023, 8 (24) , 21914-21928. https://doi.org/10.1021/acsomega.3c01753
  19. Pratibha, Atul Kapoor, Jaspreet Kaur Rajput, Arvind Kumar. Dualistic Fluorescence as Well as Portable Smartphone-Assisted RGB-Relied Sensing Assay for the Ultra-Sensitive Determination of Pendimethalin in Food and Water Samples by AIEE Active Organic Probes. Analytical Chemistry 2022, 94 (50) , 17685-17691. https://doi.org/10.1021/acs.analchem.2c04536
  20. Madhuparna Chakraborty, Banchhanidhi Prusti, Manab Chakravarty. Small Electron-Rich Isomeric Solid-State Emitters with Variation in Coplanarity and Molecular Packings: Rapid and Ultralow Recognition of TNT. ACS Applied Electronic Materials 2022, 4 (5) , 2481-2489. https://doi.org/10.1021/acsaelm.2c00241
  21. Sharjeel Ahmed, Hongwei Shi, Mustehsin Ali, Imran Ali, Fuchun Liu, En-Hou Han. A review of advancement in fluorescence-based corrosion detection for metals and future prospects. Journal of Materials Science & Technology 2025, 226 , 36-64. https://doi.org/10.1016/j.jmst.2024.12.009
  22. Preeyanuch Supchocksoonthorn, Pattaraporn Nuntahirun, Samita Soublerk, Chanuda Kaewkhong, Nichaphat Thongsai, Tanagorn Sangtawesin, Yao Wang, Peerasak Paoprasert. Novel fluorescence-based and portable detection platforms using nitrogen-doped carbon dots for environmental monitoring of dichloran fungicide. Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 2025, 336 , 125990. https://doi.org/10.1016/j.saa.2025.125990
  23. Christian Ebere Enyoh, Qingyue Wang, Weiqian Wang, Miho Suzuki, Go Masuda, Daisuke Nakajima, Senlin Lu. Green One-Step Synthesis and Characterization of Fluorescent Carbon Quantum Dots from PET Waste as a Dual-Mode Sensing Probe for Pd(II), Ciprofloxacin, and Fluoxetine via Fluorescence Quenching and Enhancement Mechanisms. Surfaces 2025, 8 (2) , 24. https://doi.org/10.3390/surfaces8020024
  24. Asmita De, Vishal Singh, Joydeep Dhar, Sumit Mishra. Zn (II) based fluorescent metal-organic framework as a 'turn-off' sensor for Al3+ and Fe3+ ions in aqueous solution: Synthesis, DFT calculations and Hirshfeld surface analysis. Journal of Molecular Structure 2025, 1329 , 141426. https://doi.org/10.1016/j.molstruc.2025.141426
  25. Prathul Nath, Ankan Dey, Tathagata Kundu, Manisha Chatterjee, Partha Roy, Zhiyi Liu, Soumitra Satapathi. Development of a smartphone integrated 3D-printed point of care platform for sensitive detection of bilirubin. Talanta 2025, 286 , 127430. https://doi.org/10.1016/j.talanta.2024.127430
  26. Jingyan Yu, Rajendran Kalimuthu, Xingchen Liu, Wengao Zhang, Yonggen Tan, Kun Yan, Shenglin Ye, Jun Feng. Unveiling the quenching mechanism of metal ions using solvent-driven N, S-doped carbon quantum dots. Optical Materials 2025, 162 , 116948. https://doi.org/10.1016/j.optmat.2025.116948
  27. Zeynep Kalaycıoğlu. Binding interaction between sodium carboxymethyl cellulose and serum albumin: Insights from multi-spectroscopy methods, rheological characterization and molecular docking analysis. Journal of Molecular Liquids 2025, 424 , 127130. https://doi.org/10.1016/j.molliq.2025.127130
  28. Xinru Zhang, Bo Sun, Huan Zhang, Chen Zhou, Qingqing Pan, Yining Wang, Chenyang Zou, Juan Hou, Jing Sun. A Novel Fluorescent Sensor for Fe3+ Based on a Quinoline Derivative. Molecules 2025, 30 (7) , 1579. https://doi.org/10.3390/molecules30071579
  29. Muthaiah Shellaiah, Kien-Wen Sun, K. Anandan, Arumugam Murugan, Vijayaraj Venkatachalam, Mayank Bhushan, Mani Sivakumar, E. Manikandan, Kumaravel Kaliaperumal, Wen-Tai Li. Luminescent Pyrene-Derivatives for Hg2+ and Explosive Detection. Chemosensors 2025, 13 (4) , 145. https://doi.org/10.3390/chemosensors13040145
  30. Renqi Ding, Jian Wang, Jiaqi Wei, Yeteng Wang, Yubing Hu, Wei Jiang, Guangpu Zhang. Smart sensing of materials: Research progress in trace detection of energetic materials. Chemical Engineering Journal 2025, 510 , 161372. https://doi.org/10.1016/j.cej.2025.161372
  31. Subrata Mandal, Akash Deshpande, Robert Leiter, Johannes Biskupek, Ute Kaiser, Andrea Pannwitz. Enhanced and Durable Light‐Driven Hydrogen Evolution by Cobalt‐Based Prussian Blue Analogs in Phospholipid Bilayers. Advanced Energy and Sustainability Research 2025, 57 https://doi.org/10.1002/aesr.202400372
  32. Wei Zhao, Juan L. Obeso, Valeria B. López‐Cervantes, Mounib Bahri, Elí Sánchez‐González, Yoarhy A. Amador‐Sánchez, Junyu Ren, Nigel D. Browning, Ricardo A. Peralta, Giovanni Barcaro, Susanna Monti, Diego Solis‐Ibarra, Ilich A. Ibarra, Dan Zhao. Achieving Sub‐ppm Sensitivity in SO 2 Detection with a Chemically Stable Covalent Organic Framework. Angewandte Chemie 2025, 137 (3) https://doi.org/10.1002/ange.202415088
  33. Wei Zhao, Juan L. Obeso, Valeria B. López‐Cervantes, Mounib Bahri, Elí Sánchez‐González, Yoarhy A. Amador‐Sánchez, Junyu Ren, Nigel D. Browning, Ricardo A. Peralta, Giovanni Barcaro, Susanna Monti, Diego Solis‐Ibarra, Ilich A. Ibarra, Dan Zhao. Achieving Sub‐ppm Sensitivity in SO 2 Detection with a Chemically Stable Covalent Organic Framework. Angewandte Chemie International Edition 2025, 64 (3) https://doi.org/10.1002/anie.202415088
  34. Manas Mahapatra, Maxime Bourguignon, Bruno Grignard, Marylène Vandevenne, Moreno Galleni, Christophe Detrembleur. Nonconventional Fluorescent Non‐Isocyanate Polyurethane Foams for Multipurpose Sensing Applications. Angewandte Chemie 2025, 137 (1) https://doi.org/10.1002/ange.202413605
  35. Manas Mahapatra, Maxime Bourguignon, Bruno Grignard, Marylène Vandevenne, Moreno Galleni, Christophe Detrembleur. Nonconventional Fluorescent Non‐Isocyanate Polyurethane Foams for Multipurpose Sensing Applications. Angewandte Chemie International Edition 2025, 64 (1) https://doi.org/10.1002/anie.202413605
  36. Murugesan Chandran, Gayathri Chellasamy, Mekala Veerapandian, Barkavi Dhanasekaran, Saravanan Govindaraju, Kyusik Yun. Instant synthesis of nitrogen-doped Ti 3 C 2 MXene quantum dots for fluorescence and electrochemical dual-mode detection of norepinephrine with a portable smartphone assay. Journal of Materials Chemistry B 2025, 13 (2) , 642-655. https://doi.org/10.1039/D4TB01818D
  37. Manpreet Kaur, Virender, Ashwani Kumar, Santosh Kumar Dubey. An Isoniazid-Based reversible Schiff base chemosensor for Multi-Analyte (Cu2+, Ni2+, Hg2+) detection. Polyhedron 2025, 265 , 117282. https://doi.org/10.1016/j.poly.2024.117282
  38. Candela Melendreras, Inmaculada Ortiz-Gómez, Pablo Álvarez-García, Elena Lastra, Francisco Javier García Alonso, José M. Costa-Fernandez, Ana Soldado. Copper nano metal-organic framework paper-based sensor for dual optical detection of biogenic amines to evaluate the food freshness. Talanta 2025, 282 , 127026. https://doi.org/10.1016/j.talanta.2024.127026
  39. Shrodha Mondal, Olivia Sarkar, Santi M. Mandal, Ansuman Chattopadhyay, Prithidipa Sahoo. Monitoring CO as a plant signaling molecule under heavy metal stress using carbon nanodots. Dalton Transactions 2025, 31 https://doi.org/10.1039/D4DT03101F
  40. Arvin Sain Tanwar, Parameswar Krishnan Iyer, Franck Meyer. Dual-modal detection of perfluorooctanoic acid (PFOA) using a single polymer platform: ACQ and IDA approaches. RSC Applied Polymers 2025, 256 https://doi.org/10.1039/D4LP00344F
  41. Andreea Laura Chibac-Scutaru, Gheorghe Roman. Fluorescence sensing of metal ions in solution using a morpholine-containing phenolic Mannich base of 1′-hydroxy-2′-acetonaphthone. RSC Advances 2024, 14 (52) , 38590-38604. https://doi.org/10.1039/D4RA07200F
  42. Fatemah Aldakhil, Nawal A. Alarfaj, Salma A. Al-Tamimi, Maha F. El-Tohamy. Development of silver-doped carbon dots sensor derived from lignin for dual-mode fluorometric and spectrophotometric determination of valsartan in a bulk powder and a commercial product. Heliyon 2024, 10 (23) , e40848. https://doi.org/10.1016/j.heliyon.2024.e40848
  43. Kuppusamy Suganthirani, Rajendran Kishore Kumar, Thangaraj Thiruppathiraja, Panneerselvan Prabha, Senthilkumar Lakshmipathi, Subramaniam Selvakumar, Jan Grzegorz Malecki, Balasubramanian Murugesapandian. AIE active hydroxycoumarin-anthranilic acid coupled enamine: Sequential detection of Cu2+/S2− ions and live cell imaging application. Microchemical Journal 2024, 207 , 112080. https://doi.org/10.1016/j.microc.2024.112080
  44. Somnath Nayek, Subrata Nayak, Sumanta Bhattacharya, Sanyukta Bhattacharjee, Shalmali Bhattacharya. Study of complexation and energy transfer phenomenons in core/shell quantum dots-tetraphenyl porphyrin systems in solution. Journal of Porphyrins and Phthalocyanines 2024, 28 (11n12) , 786-797. https://doi.org/10.1142/S1088424624500615
  45. Zahra Mousavi, Jahan B. Ghasemi, Ghodsi Mohammadi Ziarani, Shahnaz Rahimi, Alireza Badiei. Coumarin derivative-functionalized nanoporous silica as an on–off fluorescent sensor for detecting Fe3+ and Hg2+ ions: a circuit logic gate. Discover Nano 2024, 19 (1) https://doi.org/10.1186/s11671-024-04013-9
  46. Gulshan Anjum, Ashish Kumar, Gurunath Ramanathan, Jarugu Narasimha Moorthy. Green fluorescent protein chromophore-based covalent organic polymers (GFPC-COPs): sensing of nitroaromatic organic pollutants and explosives. Materials Advances 2024, 5 (23) , 9279-9291. https://doi.org/10.1039/D4MA00811A
  47. Kiran Gupta, Nandini Tiwari, Prashant Dubey, Ranju Yadav, Ruchi Aggarwal, Chumki Dalal, Sumit Kumar Sonkar. Small amine-functionalized diesel soot-derived onion-like nanocarbon for selective sensing of glutamic acid and imaging application. New Journal of Chemistry 2024, 48 (43) , 18580-18588. https://doi.org/10.1039/D4NJ03514C
  48. Pravat Ghorai, Udayan Mondal, Abhijit Hazra, Priyabrata Banerjee. Luminescent metal organic frameworks (LMOFs) and allied composites for the unveiling of organic environmental contaminants (explosive NACs, PAHs and EDCs) sensing through ‘Molecular Recognition’: A chronicle of recent penetration and future modelling. Coordination Chemistry Reviews 2024, 518 , 216085. https://doi.org/10.1016/j.ccr.2024.216085
  49. Bably Khatun, Kangkan Jyoti Goswami, Neelotpal Sen Sarma. Single step synthesis of β -cyclodextrin-sericin based nitrogen-doped graphene oxide quantum dots for visual and optical detection of Riboflavin via Inner Filter Effect. Journal of Photochemistry and Photobiology A: Chemistry 2024, 456 , 115795. https://doi.org/10.1016/j.jphotochem.2024.115795
  50. Z. Nawas Sherif, K. Anitha. Efficacious sensing and elimination of iron ions from aqueous medium by polyethylenimine functionalized carbon dot. Journal of Environmental Chemical Engineering 2024, 12 (5) , 113595. https://doi.org/10.1016/j.jece.2024.113595
  51. Gunture, Tae Yoon Lee. Biomass-derived sensor for selective detection of Fe(III) ions in non-aqueous environments. Journal of Environmental Chemical Engineering 2024, 12 (5) , 113759. https://doi.org/10.1016/j.jece.2024.113759
  52. Pradnya K. Pachpatil, Seema V. Kanojia, Vaidehi Raut, Akhilesh Potnis, Dibakar Goswami. N-rich carbon nanosphere as fluorescent nanoprobe for intracellular iron. Talanta 2024, 278 , 126454. https://doi.org/10.1016/j.talanta.2024.126454
  53. Rousunara Khatun, Malay Dolai, Mihir Sasmal, Atul Katarkar, Abu Saleh Musha Islam, Nasima Yasmin, Sana Maryum, Jebiti Haribabu, Mahammad Ali. Small molecule interactions with biomacromolecules: selective sensing of human serum albumin by a hexanuclear manganese complex – photophysical and biological studies. Journal of Materials Chemistry B 2024, 12 (37) , 9408-9419. https://doi.org/10.1039/D4TB00712C
  54. Anjali Kumari Garg, Vaishali Singh, Nicky Kumar Lamba, Chumki Dalal, Sumit Kumar Sonkar. Silver phosphate-based melamine–formaldehyde polymer for reduction of mono, di, and tri-nitrophenols under ambient conditions. New Journal of Chemistry 2024, 48 (36) , 15726-15730. https://doi.org/10.1039/D4NJ02419B
  55. Vishakha Jaswal, Sanya Pachisia, Jagrity Chaudhary, Krishnan Rangan, Madhushree Sarkar. Selective sensing of picric acid using a Zn( ii )-metallacycle: experimental and theoretical validation of the sensing mechanism and quantitative analysis of sensitivity in contact mode detection. Dalton Transactions 2024, 53 (35) , 14710-14724. https://doi.org/10.1039/D4DT01771D
  56. V. Sreelaya, Shahnaz S. Rohman, Pattiyil Parameswaran, Lakshmi Chakkumkumarath. An investigation of the Excitation Wavelength‐Dependent Dynamic Changes in the Mechanism of Detection of Picric Acid using Pyrene‐Based Donor‐Acceptor Systems. ChemPhysChem 2024, 25 (17) https://doi.org/10.1002/cphc.202400264
  57. Jeffrey L. Viegas, Vishnu R. Chari, Sunder N. Dhuri. Ligand Backbone Influenced Luminescent Properties of Mononuclear Zn(II)‐N3Py2 Compounds: Synthesis, Structures and Nitroaromatics Detection. ChemistrySelect 2024, 9 (36) https://doi.org/10.1002/slct.202402704
  58. Srishti Singh Chauhan, Bhaskar Mohan Murari. Fluorescence Spectroscopic Studies to Evaluate Binding Interaction between Hoechst 33258 and Bilirubin. Journal of Fluorescence 2024, 34 (5) , 2229-2237. https://doi.org/10.1007/s10895-023-03440-8
  59. Merin K Abraham, Jithin Raj R, Anju S Madanan, Susan Varghese, Ali Ibrahim Shkhair, Geneva Indongo, Greeshma Rajeevan, N.S. Vijila, B.K. Arathy, Sony George. A comparative study of Fe (II) doped chiral L/D-methionine carbon dots (MCDs) as a “Turn-on” fluorescent probe for the sensitive detection of L – cysteine. Journal of Molecular Structure 2024, 1311 , 138333. https://doi.org/10.1016/j.molstruc.2024.138333
  60. Vengatesh Gopal, Jayasankar Sudhakaran, Nirenjana Ramachandran, Thejus Kozhiyottu Mana, Aravind Remesh Kana, Anandhu Omanakuttan Nair, Priyanka Mohan, Tejaswini Madhusudhan, Sankarasekaran Shanmugaraju, Pandurangan Nanjan. Synthesis and fluorescence properties of 2′-benzyloxy flavone—a dual probe for selective detection of picric acid and pH sensing. Sensors & Diagnostics 2024, 3 (8) , 1263-1271. https://doi.org/10.1039/D4SD00151F
  61. Nilanjan Dey, Tathagata Ray, Santanu Bhattacharya. Dual Mode Ratiometric Analysis of Cu 2+ and Ni 2+ Ions at Physiological pH: Effect of Signalling Units on Analytical Efficacy. Asian Journal of Organic Chemistry 2024, 13 (8) https://doi.org/10.1002/ajoc.202400153
  62. Collinica Syiemlieh, Mahalakshmi Narayanan, Marappan Velusamy, Arunkumar Kathiravan. Pyrene based AIE-active probe for selective detection of picric acid through the inner filter effect channel in aqueous medium. Journal of Molecular Liquids 2024, 407 , 125125. https://doi.org/10.1016/j.molliq.2024.125125
  63. Li-Li Man, Gang Wang, Xian Wei, Cheng Xu, Li Tong, Yang Zhang, Wen-Kui Dong. Spectroscopic properties of a fluorescent pyrene-quinoline-based bisoxime-type sensor and its application to the detection of Cu2+ ion in real water samples. Journal of Molecular Structure 2024, 1309 , 138131. https://doi.org/10.1016/j.molstruc.2024.138131
  64. Jin Xu, Xiaohui Zhang, Jiapeng Zhong, Siying Huang, Shumei Wang, Haiyun Zhai. Surface-active agent enhanced FRET effect Cu-doped NH2-MIL-88(Fe) for highly sensitive detection of 3-nitro-L-tyrosine. Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 2024, 316 , 124315. https://doi.org/10.1016/j.saa.2024.124315
  65. Muhammed Arshad, Athira Ajayan, Vismaya Joseph, Abraham Joseph. Highly sensitive detection of copper in aqueous media using a fluorescent probe developed from isophthaldehyde and (E)-1-(hydrazonomethyl) naphthlen-2-ol. Sensors and Actuators A: Physical 2024, 373 , 115436. https://doi.org/10.1016/j.sna.2024.115436
  66. Denitsa Elenkova, Yana Dimitrova, Martin Tsvetkov, Bernd Morgenstern, Maria Milanova, Dimitar Todorovsky, Joana Zaharieva. Investigation of the Sensing Properties of Lanthanoid Metal–Organic Frameworks (Ln-MOFs) with Terephthalic Acid. Molecules 2024, 29 (15) , 3713. https://doi.org/10.3390/molecules29153713
  67. Panagiota Bika, Vasileios K. Tzitzios, Elias Sakellis, Spyros Orfanoudakis, Nikos Boukos, Saeed M. Alhassan, Polychronis Tsipas, Vasileios Psycharis, Thomas Stergiopoulos, Panagiotis Dallas. Electron transfer and energy exchange between a covalent organic framework and CuFeS 2 nanoparticles. Journal of Materials Chemistry C 2024, 12 (28) , 10475-10486. https://doi.org/10.1039/D4TC01989J
  68. Sania, Mohammed A. Assiri, Sanwa Rafique, Hasher Irshad, Zulfiqar Ali Khan, Farhan A. Khan, Sohail Anjum Shahzad. Investigating structural dynamics and sensing capabilities: Spectroscopic and DFT analysis of novel AIEE active deferasirox based organic sensor. Journal of Molecular Structure 2024, 1307 , 137963. https://doi.org/10.1016/j.molstruc.2024.137963
  69. Morteza Soltani-Shahrivar, Abbas Afkhami, Tayyebeh Madrakian. Design and optimization of a cost-effective paper-based voltammetric sensor for the determination of trinitrotoluene (TNT) utilizing cysteamine-linked Fe3O4 @Au nanocomposite. Talanta 2024, 274 , 126041. https://doi.org/10.1016/j.talanta.2024.126041
  70. Fatemah Aldakhil, Nawal A. Alarfaj, Salma A. Al-Tamimi, Maha F. El-Tohamy. Hydrothermal synthesis of modified lignin-based carbon dots derived from biomass waste for fluorescence determination of valsartan. RSC Advances 2024, 14 (28) , 19969-19982. https://doi.org/10.1039/D4RA02398F
  71. Xiaoyong Tian, Yu Zhang, Kezhen Zhang, Nan Wang, Huaping Wang, Hongyao Xu, Shanyi Guang. A novel triaminopyridine fluorescent probe based on AIE effect with high selectivity under solvent shielding effect. Microchemical Journal 2024, 201 , 110534. https://doi.org/10.1016/j.microc.2024.110534
  72. Ximan Zhang, Weichao Ma, Lina Zhao. Fluorescence detection of difloxacin in milk using blue light-emitting carbon dots. Microchemical Journal 2024, 201 , 110535. https://doi.org/10.1016/j.microc.2024.110535
  73. Fatemah Aldakhil, Nawal A. Alarfaj, Salma A. Al-Tamimi, Maha F. El-Tohamy. A Dual-Mode Spectrophotometric and Fluorescent Probe Based on Lignin-Derived Carbon Dots for the Detection of Atorvastatin Calcium in a Bulk Powder and a Commercial Product. Journal of Fluorescence 2024, 15 https://doi.org/10.1007/s10895-024-03745-2
  74. Junjie Lin, Wanyi Huang, Haoran Zhang, Xuejie Zhang, Yingliang Liu, Wei Li, Bingfu Lei. A fluorescence probe based on blue luminescent carbon dots for sensing Fe 3+ in plants. Journal of Materials Chemistry C 2024, 12 (15) , 5480-5487. https://doi.org/10.1039/D4TC00107A
  75. Rocky Raj, Mradula, Pradipta Samanta, Ravinderjit Singh, Abhay Sachdev, Sunita Mishra. Evaluation of AgNCs@PEI and their integrated hydrogel for colorimetric and fluorometric detection of ascorbic acid. Analytical Biochemistry 2024, 687 , 115433. https://doi.org/10.1016/j.ab.2023.115433
  76. Shalini Singh, Deepanshu Bhatt, Akash Deep, Umesh K Tiwari. An antibody conjugated NH2-MIL-101(Fe) metal-organic framework based optical biosensor for sensitive detection of lead ions. Microchemical Journal 2024, 199 , 110122. https://doi.org/10.1016/j.microc.2024.110122
  77. Mohammad Khalid Zia, Tooba Siddiqui, Sana Ansari, Mohammad Muaz, Haseeb Ahsan, Fahim Halim Khan. Insight into the molecular interaction between the anticancer drug, enzalutamide and human alpha-2-macroglobulin: Biochemical and biophysical approach. Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 2024, 311 , 123957. https://doi.org/10.1016/j.saa.2024.123957
  78. Arvin Sain Tanwar, Moirangthem Anita Chanu, Retwik Parui, Debika Barman, Yeon-Ho Im, Parameswar Krishnan Iyer. Dynamic quenching mechanism based optical detection of carcinogenic Cr( vi ) in water and on economical paper test strips via a conjugated polymer. RSC Applied Polymers 2024, 2 (2) , 196-204. https://doi.org/10.1039/D3LP00195D
  79. Praveena Rajendran, Parvathavarthini Murugaperumal, Sengottuvelan Nallathambi, Franc Perdih, Siva Ayyanar, Selvaraju Chellappan. Performance of 4,5‐diphenyl‐1 H ‐imidazole derived highly selective ‘Turn‐Off’ fluorescent chemosensor for iron(III) ions detection and biological applications. Luminescence 2024, 39 (3) https://doi.org/10.1002/bio.4694
  80. Vanshika Sharma, Meman Sahu, Dinesh De, Goutam Kumar Patra. Synthesis, Crystal Structure, DFT and Fluorescence Quenching Study of Novel syringe aldehyde-derived hydrazinyl-imidazole Based Schiff base Chemosensor. Journal of Fluorescence 2024, 34 (2) , 865-877. https://doi.org/10.1007/s10895-023-03319-8
  81. Bimal Chettri, Rikitha S Fernandes, Satadru Jha, Nilanjan Dey. Label-free multimodal analysis of copper ions at below permissible exposure limit in the aqueous medium. Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 2024, 308 , 123620. https://doi.org/10.1016/j.saa.2023.123620
  82. Nithya Mohan, S. S. Sreejith, M. R. Prathapachandra Kurup. A novel Salen-based dual channel sensor for easy and selective nanomolar detection of l -cysteine. New Journal of Chemistry 2024, 48 (6) , 2584-2593. https://doi.org/10.1039/D3NJ05504C
  83. Vida Sedighi, Farnoush Faridbod. Synthesis of polymer dots as fluorescent nanoprobe for the detection of Ponceau 4R, an additive color abuse in food. Food Chemistry 2024, 434 , 137402. https://doi.org/10.1016/j.foodchem.2023.137402
  84. Gouranga Jana, Shukdeb Sing, Arindam Das, Anirban Basu. Interaction of food colorant indigo carmine with human and bovine serum albumins: A multispectroscopic, calorimetric, and theoretical investigation. International Journal of Biological Macromolecules 2024, 259 , 129143. https://doi.org/10.1016/j.ijbiomac.2023.129143
  85. Crescentia Yazhini, Georgeena Mathew, Masakazu Anpo, Guillaume Maurin, Wonyong Choi, Bernaurdshaw Neppolian. Decoding the Mechanistic Strategies of Lanthanide‐based Luminescent Metal‐Organic Frameworks towards Antibiotic Detection. Advanced Optical Materials 2024, 12 (1) https://doi.org/10.1002/adom.202301625
  86. Isaí Barboza-Ramos, Sukriye Nihan Karuk Elmas, Kirk S. Schanze. Fluorogenic sensors. 2024, 181-223. https://doi.org/10.1016/B978-0-443-13394-7.00005-7
  87. Mst Nasima Khatun, Moirangthem Anita Chanu, Debika Barman, Priyam Ghosh, Tapashi Sarmah, Laxmi Raman Adil, Parameswar Krishnan Iyer. Sensors based on polymer nanomaterials. 2024, 391-428. https://doi.org/10.1016/B978-0-443-13394-7.00010-0
  88. Roberto J. Aguado. Detection of nitroaromatic and nitramine explosives. 2024, 671-706. https://doi.org/10.1016/B978-0-443-13394-7.00018-5
  89. Sameer Hussain, Chunhong Zhu, Ziyu Yue, Yi Hao, Ruixia Gao, Jinhua Wei. Rational design of signal amplifying fluorescent conjugated polymers for environmental monitoring applications: Recent advances and perspectives. Coordination Chemistry Reviews 2024, 499 , 215480. https://doi.org/10.1016/j.ccr.2023.215480
  90. Umesha Katrahalli, Govindaswamy Shanker, Debnath Pal, Manjunatha Devagondanahalli Hadagali. Molecular spectroscopic and docking analysis of the interaction of fluorescent thiadicarbocyanine dye with biomolecule bovine serum albumin. Journal of Biomolecular Structure and Dynamics 2023, 41 (20) , 10702-10712. https://doi.org/10.1080/07391102.2022.2158135
  91. Soumen Ghosh, Jyoti Devi Katiyar, Subrata Chattopadhyay. Stimuli-directed selective detection of Cu 2+ and Cr 2 O 7 2− ions using a pH-responsive chitosan-poly(aminoamide) fluorescent microgel in aqueous media. Soft Matter 2023, 20 (1) , 79-88. https://doi.org/10.1039/D3SM01319G
  92. Sanjay Yadav, Nishu Choudhary, Alok Ranjan Paital. Carbon within carbon: growth of excitation-independent CDs within functional mesoporous carbon towards detection and adsorption of a specific nitrofuran class of antibiotics. Journal of Materials Chemistry A 2023, 12 (1) , 202-213. https://doi.org/10.1039/D3TA05273G
  93. Kashish Azeem, Mofieed Ahmed, Amad Uddin, Shailja Singh, Rajan Patel, Mohammad Abid. Comparative investigation on interaction between potent antimalarials and human serum albumin using multispectroscopic and computational approaches. Luminescence 2023, 38 (12) , 2018-2033. https://doi.org/10.1002/bio.4590
  94. Chandni Sharma, Mohini Verma, Syed M.S. Abidi, Ashish K. Shukla, Amitabha Acharya. Functional fluorescent nanomaterials for the detection, diagnosis and control of bacterial infection and biofilm formation: Insight towards mechanistic aspects and advanced applications. Colloids and Surfaces B: Biointerfaces 2023, 232 , 113583. https://doi.org/10.1016/j.colsurfb.2023.113583
  95. Praveena Rajendran, Parvathavarthini Murugaperumal, Gayathri Santhalingam, Sengottuvelan Nallathambi, Franc Perdih, Siva Ayyanar, Ashokkumar Balasubramaniem. Structural elucidation and spectroscopic studies of acetyl substituted piperazine nucleus tethered with 4, 5-diaryl-1 H-imidazole scaffold: DNA binding, Cu2+and Sn2+ ions sensing and cytotoxicity. Journal of Molecular Structure 2023, 1293 , 136249. https://doi.org/10.1016/j.molstruc.2023.136249
  96. Mingya Wang, Shengling Li, Junli Shi, Yongzheng Liu, Duanlin Cao, Linxiu Zhao. A simple BODIPY-based fluorescent probe for sequential recognition of Cu2+ and GSH and its application on test strips and bioimaging in living cells. Journal of Molecular Structure 2023, 1294 , 136393. https://doi.org/10.1016/j.molstruc.2023.136393
  97. Romina Yousefi, Saba Ahmadi, Ghodsi Mohammadi Ziarani, Alireza Badiei. Synthesis of [Ta6O19] @MOF composite as a chloroacetaldehyde optical sensor in wastewater obtained from two waste-resourced precursors: Tantalum from capacitors and terephthalic acid from PET bottle. Materials Today Sustainability 2023, 24 , 100604. https://doi.org/10.1016/j.mtsust.2023.100604
  98. Haitham K.R. Al-Sharifi, Ani Deepthi. Study on the mechanistic classes of fluorescence quenching of tryptanthrin-malononitrile adduct by aniline. Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 2023, 303 , 123261. https://doi.org/10.1016/j.saa.2023.123261
  99. Arvin Sain Tanwar, Mst Nasima Khatun, Moirangthem Anita Chanu, Tapashi Sarmah, Yeon-Ho Im, Parameswar Krishnan Iyer. A water-soluble conjugated polyelectrolyte for selective and sensitive detection of carcinogenic chromium( vi ). The Analyst 2023, 148 (23) , 6011-6019. https://doi.org/10.1039/D3AN01387A
  100. Arpna Tamrakar, Kamlesh Kumar Nigam, Mrituanjay D. Pandey. Copper-guided tuning of supramolecular nano-assembly in pseudopeptide-based soft bioinspired materials. New Journal of Chemistry 2023, 47 (45) , 20785-20792. https://doi.org/10.1039/D3NJ04599D
Load all citations
Download PDF
Go to ACS Measurement Science Au
Get e-Alerts
Get e-Alerts

ACS Measurement Science Au

Cite this: ACS Meas. Sci. Au 2022, 2, 1, 23–30
Click to copy citationCitation copied!
https://doi.org/10.1021/acsmeasuresciau.1c00023
Published September 8, 2021

Copyright © 2021 The Authors. Published by American Chemical Society. This publication is licensed under

CC-BY-NC-ND 4.0 .

Article Views

14k

Altmetric

-

Citations

137
Learn about these metrics

Article Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.

Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.

The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated.

  • Abstract

    High Resolution Image
    Download MS PowerPoint Slide

    Scheme 1

    Scheme 1. (a) 1,6-Dibromohexane, Tetrabutylammonium Iodide (TBAI), 50% NaOH(aq.), 70 °C, 4 h. (b) Tetrakistriphenylphosphine Palladium (0), 2,1,3-Benzothiadiazole-4,7-Bis(boronic acid pinacol ester), aq. K2CO3, THF, reflux, 24 h; (c) Pyridine, DMF, 70 °C, 24 h
    High Resolution Image
    Download MS PowerPoint Slide

    Figure 1

    Figure 1. (a) PL spectra of PFPy (6.66 μM) at different concentration of TNT in water containing 10 mM NaOH. (b) Effect of various NACs (3.33 μM) on the PFPy (6.66 μM) intensity. (c) S–V plots (3D) obtained for various NACs. (d) Quenching (%) by various NACs (3.33 μM) before (blue) and after (red) addition of TNT (3.33 μM).

    High Resolution Image
    Download MS PowerPoint Slide

    Figure 2

    Figure 2. (1) Stern–Volmer (S–V) plot (2D) obtained for (a) all NACs and (b) second-order polynomial fitting of S–V plot for TNT. (c) S–V equation for both static and dynamic quenching. (2) (a) Time-resolved photoluminescence (TRPL) spectra of PFPy (6.66 μM) in the absence and presence of various concentration of TNT in water containing 10 mM NaOH. (b) Change in lifetime at various concentrations of TNT. (c) Equation (II) for dynamic quenching: where τ and τo are the average fluorescence lifetime with and without TNT, respectively. (3) (a) Spectral overlap between the normalized PL spectrum [0–0.1] of CP PFPy with absorbance of various NACs in water containing 10 mM NaOH. (b) Spectral overlapping region between the normalized emission spectrum of PFPy with TNT in water containing 10 mM NaOH. (c) Equations for RET parameters: (1) Equation (III)-where J denotes overlap integral value, FD(λ) represents the corrected fluorescence intensity from λ to Δλ with total fluorescence intensity for PFPy normalized to 1, and εA represents molar absorptivity of acceptor in M–1 cm–1. (2) Equation (IV)-where R0 represents Förster distance, Q denotes the fluoresence quantum yield of PFPy, η represents refractive index of the medium, and k2 signifies dipole orientation factor (0.667). (3) Equation (V)-where E% denotes RET efficiency, τDA and τD are the average fluorescence lifetime with and without quencher, i.e., TNT.

    High Resolution Image
    Download MS PowerPoint Slide

    Figure 3

    Figure 3. (a) Absorbance of PFPy (6.66 μM) in the presence of various amounts of TNT in water containing 10 mM NaOH. (b) Absorbance of TNT in water containing 10 mM NaOH. (c) Plot of Kapp versus concentration of TNT in water containing 10 mM NaOH. (d) Equations and calculation for static and dynamic quenching constants, i.e., KS and KD, respectively.

    High Resolution Image
    Download MS PowerPoint Slide

    Figure 4

    Figure 4. Combined dynamic and static quenching of the same population of the fluorophore PFPy via quencher (Q), i.e., Meisenheimer complex of TNT.

    High Resolution Image
    Download MS PowerPoint Slide

    Figure 5

    Figure 5. Photographs of portable paper strips under the UV emitting lamp of 365 nm wavelength after applying a fixed volume (10 μL) of different concentration of TNT solution.

    High Resolution Image
    Download MS PowerPoint Slide

    Figure 6

    Figure 6. Photographs of three different locations and portable paper strips under UV light after being in contact with soil samples spiked with different concentration of TNT.

    High Resolution Image
    Download MS PowerPoint Slide

  • References

    This article references 34 other publications.

    1. 1
      Sun, X.; Wang, Y.; Lei, Y. Fluorescence based explosive detection: from mechanisms to sensory materials. Chem. Soc. Rev. 2015, 44 (22), 8019– 8061,  DOI: 10.1039/C5CS00496A
      1
      Fluorescence based explosive detection: from mechanisms to sensory materials
      Sun, Xiangcheng; Wang, Ying; Lei, Yu
      Chemical Society Reviews (2015), 44 (22), 8019-8061CODEN: CSRVBR; ISSN:0306-0012. (Royal Society of Chemistry)
      The detection of explosives is one of the current pressing concerns in global security. In the past few decades, a large no. of emissive sensing materials have been developed for the detection of explosives in vapor, soln., and solid states through fluorescence methods. In recent years, great efforts have been devoted to develop new fluorescent materials with various sensing mechanisms for detecting explosives in order to achieve super-sensitivity, ultra-selectivity, as well as fast response time. This review article starts with a brief introduction on various sensing mechanisms for fluorescence based explosive detection, and then summarizes in an exhaustive and systematic way the state-of-the-art of fluorescent materials for explosive detection with a focus on the research in the recent 5 years. A wide range of fluorescent materials, such as conjugated polymers, small fluorophores, supramol. systems, bio-inspired materials and aggregation induced emission-active materials, and their sensing performance and sensing mechanism are the centerpiece of this review. Finally, conclusions and future outlook are presented and discussed.
    2. 2
      Sun, Y.; Wu, Y.; Yu, C.; Zhang, L.; Song, G.; Yao, Z. Self-Assembly of nanoscale induced excimers of 12-Pyren-1-yldodecanoic acid for TNT detection. ACS Appl. Nano Mater. 2019, 2 (6), 3453– 3458,  DOI: 10.1021/acsanm.9b00386
      2
      Self-Assembly of Nanoscale Induced Excimers of 12-Pyren-1-yldodecanoic Acid for TNT Detection
      Sun, Yanan; Wu, Yuwei; Yu, Chaoran; Zhang, Li; Song, Gang; Yao, Zhiyi
      ACS Applied Nano Materials (2019), 2 (6), 3453-3458CODEN: AANMF6; ISSN:2574-0970. (American Chemical Society)
      We report nanoscale pyrenyl excimers induced by the self-assembly of a pyrene-based fluorescent probe, 12-pyren-1-yldodecanoic acid (PyDA), for rapid detection of 2,4,6-trinitrotoluene (TNT) in aq. media. Under the optimized conditions, the sensing nanosystem exhibited fast response and high selectivity and sensitivity for the detection of TNT. Esp., it could distinguish TNT from TNP, which is the major interferent in most circumstances. The detection limit is as low as 5.0 × 10-9 M. It also can be used for qual. and quant. monitoring TNT in real samples.
    3. 3
      Agency for toxic substances and disease registry Toxicological profile for 2,4,6-trinitrotoluene ; 1995; https://wwwn.cdc.gov/TSP/ToxProfiles/ToxProfiles.aspx?id=677&tid=125.
      There is no corresponding record for this reference.
    4. 4
      Hakonen, A.; Andersson, P. O.; Stenbæk Schmidt, M.; Rindzevicius, T.; Käll, M. Explosive and chemical threat detection by surface-enhanced Raman scattering: a review. Anal. Chim. Acta 2015, 893, 1– 13,  DOI: 10.1016/j.aca.2015.04.010
      4
      Explosive and chemical threat detection by surface-enhanced Raman scattering: A review
      Hakonen, Aron; Andersson, Per Ola; Stenbaek Schmidt, Michael; Rindzevicius, Tomas; Kaell, Mikael
      Analytica Chimica Acta (2015), 893 (), 1-13CODEN: ACACAM; ISSN:0003-2670. (Elsevier B.V.)
      A review. Acts of terror and warfare threats are challenging tasks for defense agencies around the world and of growing importance to security conscious policy makers and the general public. Explosives and chem. warfare agents are two of the major concerns in this context, as illustrated by the recent Boston Marathon bombing and nerve gas attacks on civilians in the Middle East. To prevent such tragic disasters, security personnel must be able to find, identify and deactivate the threats at multiple locations and levels. This involves major tech. and practical challenges, such as detection of ultra-low quantities of hazardous compds. at remote locations for anti-terror purposes and monitoring of environmental sanitation of dumped or left behind toxic substances and explosives. Surface-enhanced Raman scattering (SERS) is one of todays most interesting and rapidly developing methods for label-free ultrasensitive vibrational "fingerprinting" of a variety of mol. compds. Performance highlights include attomolar detection of TNT and DNT explosives, a sensitivity that few, if any, other technique can compete with. Moreover, instrumentation needed for SERS anal. are becoming progressively better, smaller and cheaper, and can today be acquired for a retail price close to 10,000 US$. This contribution aims to give a comprehensive overview of SERS as a technique for detection of explosives and chem. threats. The authors discuss the prospects of SERS becoming a major tool for convenient in-situ threat identification and the authors summarize existing SERS detection methods and substrates with particular focus on ultra-sensitive real-time detection. General concepts, detection capabilities and perspectives are discussed to guide potential users of the technique for homeland security and anti-warfare purposes.
    5. 5
      Zhao, X.; Yinon, J. Characterization and origin identification of 2,4,6-trinitrotoluene through its by-product isomers by liquid chromatography–atmospheric pressure chemical ionization mass spectrometry. J. Chromatogr. A 2002, 946 (1), 125– 132,  DOI: 10.1016/S0021-9673(01)01533-3
      5
      Characterization and origin identification of 2,4,6-trinitrotoluene through its by-product isomers by liquid chromatography-atmospheric pressure chemical ionization mass spectrometry
      Zhao, Xiaoming; Yinon, Jehuda
      Journal of Chromatography A (2002), 946 (1-2), 125-132CODEN: JCRAEY; ISSN:0021-9673. (Elsevier Science B.V.)
      The byproducts of industrial 2,4,6-trinitrotoluene (TNT), including isomers of trinitrotoluene, dinitrotoluene, trinitrobenzene and dinitrobenzene were studied using liq. chromatog.-mass spectrometry (LC-MS), to build a profile for the characterization of TNT samples from various origins. LC-MS with atm. pressure chem. ionization, in the neg.-ion mode, is the most suitable method for this study. The characterization of TNT by the byproduct profile was demonstrated on a variety of TNT samples.
    6. 6
      Trammell, S. A.; Melde, B. J.; Zabetakis, D.; Deschamps, J. R.; Dinderman, M. A.; Johnson, B. J.; Kusterbeck, A. W. Electrochemical detection of TNT with in-line pre-concentration using imprinted diethylbenzene-bridged periodic mesoporous organosilicas. Sens. Actuators, B 2011, 155 (2), 737– 744,  DOI: 10.1016/j.snb.2011.01.039
      6
      Electrochemical detection of TNT with in-line pre-concentration using imprinted diethylbenzene-bridged periodic mesoporous organosilicas
      Trammell, Scott A.; Melde, Brian J.; Zabetakis, Daniel; Deschamps, Jeffrey R.; Dinderman, Michael A.; Johnson, Brandy J.; Kusterbeck, Anne W.
      Sensors and Actuators, B: Chemical (2011), 155 (2), 737-744CODEN: SABCEB; ISSN:0925-4005. (Elsevier B.V.)
      The authors examd. the adsorption and release of TNT using diethylbenzene-bridged (DEB) periodic mesoporous organosilica sorbents under varying conditions. The sorbents were applied for in-line target pre-concn. in conjunction with an electrochem. flow cell contg. a glassy carbon electrode. Square wave voltammetry was employed for TNT detection. TNT sample vols. between 2 and 480 mL at concns. ranging from 0.5 to 500 ppb were passed through the DEB sorbents (imprinted or not imprinted for TNT) at pH 6 (sodium acetate) or at pH 7.4 (PBS). Release of target was accomplished using solvent mixts. of methanol/water with sodium acetate as electrolyte or acetonitrile/water with PBS components as electrolyte. Under these conditions, the TNT was released in <200 μL of the solvent mixt., and pre-concn. factors of >3000 can be achieved when using large vols. of trace TNT samples. When sample vols. of 2 mL were used, the sensing system gave a linear response between 20 and 500 ppb with an estd. limit of detection of 13 ppb. When pre-concg. 480 mL of sample in either buffered soln. or seawater, detection of 0.5 ppb TNT was achieved with a signal to noise ratio of 20.
    7. 7
      Soldate, A. M.; Noyes, R. M. X-Ray diffraction patterns for identification of crystalline constituents of explosives. Anal. Chem. 1947, 19 (7), 442– 444,  DOI: 10.1021/ac60007a004
      7
      X-ray diffraction patterns for the identification of crystalline constituents of explosives
      Soldate, Albert M.; Noyes, Richard M.
      (1947), 19 (), 442-4CODEN: ANCHAM; ISSN:0003-2700.
      New powder-diffraction data, suitable for use as aids in the identification of constituents in unknown samples, are given for 18 org. compds. present in explosives. The data were obtained with Cu Kα radiation, filtered by Ni foil and collimated by a two-slit system. A form similar to that used by Hanawalt, Rinn, and Frevel (C.A. 32, 7841.8) for the presentation of x-ray powder data to be used for analytical purposes was used. Only the morphological forms of these compds. commonly occurring in the explosives under investigation were studied. Interplanar spacings and approx. intensities are given in tabular form for the following compds.: pentaerythritol tetranitrate, 2,4-dinitrotoluene, 2,4,6-trinitrotoluene, picric acid, guanidine picrate, ethylene-dinitramine, nitroguanidine, 2,2,5,5-tetrahydroxymethylcyclopentanone tetranitrate, dihydroxyethylnitramine dinitrate, hexahydro-1,3,5-trinitro-s-triazine, octahydro-1,3,5,7-tetranitro-s-tetrazine, 1-acetyloctahydro-3,5,7-trinitro-s-tetrazine, α, β-diethylcarbanilide, diphenylamine, N-nitrosodiphenylamine, 2-nitrodiphenylamine, 2,4'-dinitrodiphenylamine, 4,4'-dinitrodiphenylamine.
    8. 8
      Calcerrada, M.; González-Herráez, M.; García-Ruiz, C. Recent advances in capillary electrophoresis instrumentation for the analysis of explosives. TrAC, Trends Anal. Chem. 2016, 75, 75– 85,  DOI: 10.1016/j.trac.2015.08.005
      8
      Recent advances in capillary electrophoresis instrumentation for the analysis of explosives
      Calcerrada, Matias; Gonzalez-Herraez, Miguel; Garcia-Ruiz, Carmen
      TrAC, Trends in Analytical Chemistry (2016), 75 (), 75-85CODEN: TTAEDJ; ISSN:0165-9936. (Elsevier B. V.)
      Capillary electrophoresis (CE) is a well-established anal. sepn. technique. Owing to its high versatility, major advancements have been made with regard to the instrumental set-ups during the last years. New strategies have been proposed to develop high-sensitive methods, portable CE or miniaturized devices. These techniques are of great interest in the anal. of explosives, which generally requires a highly selective approach. This review provides a recent perspective (from the beginning of 2008 to March 2015) on the use of CE for the anal. of explosives. First, a general description of explosives is made, emphasizing the role of sepn. techniques and specifically CE. Next, the most recent works focused on the anal. of explosives by using conventional CE, portable CE and microchip CE are compared and critically discussed. Besides, other emerging techniques for the anal. of explosives are referred and compared to CE results. Finally, future perspectives for the anal. of explosives by CE are proposed.
    9. 9
      Senthamizhan, A.; Celebioglu, A.; Bayir, S.; Gorur, M.; Doganci, E.; Yilmaz, F.; Uyar, T. Highly fluorescent pyrene-functional polystyrene copolymer nanofibers for enhanced sensing performance of TNT. ACS Appl. Mater. Interfaces 2015, 7 (38), 21038– 21046,  DOI: 10.1021/acsami.5b07184
      9
      Highly Fluorescent Pyrene-Functional Polystyrene Copolymer Nanofibers for Enhanced Sensing Performance of TNT
      Senthamizhan, Anitha; Celebioglu, Asli; Bayir, Sumeyra; Gorur, Mesut; Doganci, Erdinc; Yilmaz, Faruk; Uyar, Tamer
      ACS Applied Materials & Interfaces (2015), 7 (38), 21038-21046CODEN: AAMICK; ISSN:1944-8244. (American Chemical Society)
      A pyrene-functional polystyrene copolymer was prepd. via 1,3-dipolar cycloaddn. reaction (Sharpless-type click reaction) between azide-functional styrene copolymer and 1-ethynylpyrene. Subsequently, nanofibers of pyrene-functional polystyrene copolymer were obtained by using electrospinning technique. The nanofibers thus obtained, found to preserve their parent fluorescence nature, confirmed the avoidance of aggregation during fiber formation. The trace detection of trinitrotoluene (TNT) in water with a detection limit of 5 nM was demonstrated, which is much lower than the max. allowable limit set by the U.S. Environmental Protection Agency. Interestingly, the sensing performance was found to be selective toward TNT in water, even in the presence of higher concns. of toxic metal pollutants such as Cd2+, Co2+, Cu2+, and Hg2+. The enhanced sensing performance was found to be due to the enlarged contact area and intrinsic nanoporous fiber morphol. Effortlessly, the visual colorimetric sensing performance can be seen by naked eye with a color change in a response time of few seconds. Furthermore, vapor-phase detection of TNT was studied, and the results are discussed herein. In terms of practical application, electrospun nanofibrous web of pyrene-functional polystyrene copolymer has various salient features including flexibility, reproducibility, and ease of use, and visual outputs increase their value and add to their advantage.
    10. 10
      Wu, X.; Hang, H.; Li, H.; Chen, Y.; Tong, H.; Wang, L. Water-dispersible hyperbranched conjugated polymer nanoparticles with sulfonate terminal groups for amplified fluorescence sensing of trace TNT in aqueous solution. Mater. Chem. Front. 2017, 1 (9), 1875– 1880,  DOI: 10.1039/C7QM00173H
      10
      Water-dispersible hyperbranched conjugated polymer nanoparticles with sulfonate terminal groups for amplified fluorescence sensing of trace TNT in aqueous solution
      Wu, Xiaofu; Hang, Hao; Li, Hua; Chen, Yonghong; Tong, Hui; Wang, Lixiang
      Materials Chemistry Frontiers (2017), 1 (9), 1875-1880CODEN: MCFAC5; ISSN:2052-1537. (Royal Society of Chemistry)
      Conjugated polymers (CPs) have been recognized as promising fluorescent sensing materials for 2,4,6-trinitrotoluene (TNT) vapor. However, their applications for TNT detection in aq. soln. are restricted because of their low sensitivity (detection limits >90 nM). Here we report highly sensitive detection of TNT by water-dispersible hyperbranched conjugated polymer nanoparticles (HCPN-S) with hydrophobic CP cores and hydrophilic sulfonate terminal groups. Based on efficient TNT encapsulation by numerous hydrophobic cavities inside the hyperbranched CP core, HCPN-S exhibits a quenching const. of 1.21 × 106 M-1, two to three orders of magnitude higher than those of CP analogs, allowing amplified detection of TNT with a detection limit of 0.8 ppb (3.7 nM), which is the best result for CP-based fluorescent sensors for TNT detection in water reported so far. Furthermore, HCPN-S can selectively detect TNT even in the presence of 2,4,6-trinitrophenol and other nitro compds.
    11. 11
      Xiao, S. J.; Zhao, X. J.; Hu, P. P.; Chu, Z. J.; Huang, C. Z.; Zhang, L. Highly photoluminescent molybdenum oxide quantum dots: one-pot synthesis and application in 2,4,6-trinitrotoluene determination. ACS Appl. Mater. Interfaces 2016, 8 (12), 8184– 8191,  DOI: 10.1021/acsami.5b11316
      11
      Highly Photoluminescent Molybdenum Oxide Quantum Dots: One-Pot Synthesis and Application in 2,4,6-Trinitrotoluene Determination
      Xiao, Sai Jin; Zhao, Xiao Jing; Hu, Ping Ping; Chu, Zhao Jun; Huang, Cheng Zhi; Zhang, Li
      ACS Applied Materials & Interfaces (2016), 8 (12), 8184-8191CODEN: AAMICK; ISSN:1944-8244. (American Chemical Society)
      As a well-studied transition-metal semiconductor material, MoOx has a wider band gap than molybdenum disulfide (MoS2), and its property varies dramatically for the existence of several different allotropes and suboxide phases of molybdenum oxides (MoOx, x < 3). In this manuscript, a one-pot method possessing the advantages of one pot, easily prepd., rapid, and environmentally friendly, has been developed for facile synthesis of highly photoluminescent MoOx quantum dots (MoOx QDs), in which com. molybdenum disulfide (MoS2) powder and hydrogen peroxide (H2O2) are employed as the precursor and oxidant, resp. The obtained MoOx QDs can be further utilized as an efficient photoluminescent probe, and a new turn-off sensor is developed for 2,4,6-trinitrotoluene (TNT) detn. based on the fact that the photoluminescence of MoOx QDs can be quenched by the Meisenheimer complexes formed in the strong alkali soln. through the inner filter effect (IFE). Under the optimal conditions, the decreased photoluminescence of MoOx QDs shows a good linear relationship to the concn. of TNT ranging from 0.5 to 240.0 μM, and the limit of detection was 0.12 μM (3σ/k). With the present turn-off sensor, TNT in river water samples can be rapidly and selectively detected without tedious sample pretreatment processes.
    12. 12
      Alizadeh, N.; Akbarinejad, A.; Ghoorchian, A. Photophysical diversity of water-soluble fluorescent conjugated polymers induced by surfactant stabilizers for rapid and highly selective determination of 2,4,6-trinitrotoluene traces. ACS Appl. Mater. Interfaces 2016, 8 (37), 24901– 24908,  DOI: 10.1021/acsami.6b08577
      12
      Photophysical Diversity of Water-Soluble Fluorescent Conjugated Polymers Induced by Surfactant Stabilizers for Rapid and Highly Selective Determination of 2,4,6-Trinitrotoluene Traces
      Alizadeh, Naader; Akbarinejad, Alireza; Ghoorchian, Arash
      ACS Applied Materials & Interfaces (2016), 8 (37), 24901-24908CODEN: AAMICK; ISSN:1944-8244. (American Chemical Society)
      The increasing application of fluorescence spectroscopy in development of reliable sensing platforms has triggered a lot of research interest for the synthesis of advanced fluorescent materials. Herein, we report a simple, low-cost strategy for the synthesis of a series of water-sol. conjugated polymer nanoparticles with diverse emission range using cationic (hexadecyltrimethylammonium bromide, CTAB), anionic (sodium dodecylbenzenesulfonate, SDBS), and nonionic (TX114) surfactants as the stabilizing agents. The role of surfactant type on the photophys. and sensing properties of resultant polymers has been investigated using dynamic light scattering (DLS), FT-IR, UV-vis, fluorescence, and energy dispersive X-ray (EDS) spectroscopies. The results show that the surface polarity, size, and spectroscopic and sensing properties of conjugated polymers could be well controlled by the proper selection of the stabilizer type. The fluorescent conjugated polymers exhibited fluorescence quenching toward nitroarom. compds. Further studies on the fluorescence properties of conjugated polymers revealed that the emission of the SDBS stabilized polymer, N-methylpolypyrrole-SDBS (NMPPY-SDBS), is strongly quenched by 2,4,6-trinitrotoluene mol. with a large Stern-Volmer const. of 59,526 M-1 and an excellent detection limit of 100 nM. UV-vis and cyclic voltammetry measurements unveiled that fluorescence quenching occurs through a charge transfer mechanism between electron rich NMPPY-SDBS and electron deficient 2,4,6-trinitrotoluene mols. Finally, the as-prepd. conjugated polymer and approach were successfully applied to the detn. of 2,4,6-trinitrotoluene in real water samples.
    13. 13
      Venkatramaiah, N.; Firmino, A. D. G.; Almeida Paz, F. A.; Tomé, J. P. C. Fast detection of nitroaromatics using phosphonate pyrene motifs as dual chemosensors. Chem. Commun. 2014, 50 (68), 9683– 9686,  DOI: 10.1039/C4CC03980G
      13
      Fast detection of nitroaromatics using phosphonate pyrene motifs as dual chemosensors
      Venkatramaiah, N.; Firmino, Ana D. G.; Almeida Paz, Filipe A.; Tome, Joao P. C.
      Chemical Communications (Cambridge, United Kingdom) (2014), 50 (68), 9683-9686CODEN: CHCOFS; ISSN:1359-7345. (Royal Society of Chemistry)
      A new class of dual fluorescent chemosensors (I, II) for nitroarom. compds. (NACs) based on phosphonated pyrene derivs. is reported, showing high selectivity towards trinitrotoluene (TNT). The strong intermol. interactions (π-π stacking and hydrogen bonding) allow high fluorescence quenching with visual detection in short response times.
    14. 14
      Yang, J.; Wang, Z.; Hu, K.; Li, Y.; Feng, J.; Shi, J.; Gu, J. Rapid and specific aqueous-Phase detection of nitroaromatic explosives with inherent porphyrin recognition sites in metal–organic frameworks. ACS Appl. Mater. Interfaces 2015, 7 (22), 11956– 11964,  DOI: 10.1021/acsami.5b01946
      14
      Rapid and Specific Aqueous-Phase Detection of Nitroaromatic Explosives with Inherent Porphyrin Recognition Sites in Metal-Organic Frameworks
      Yang, Jian; Wang, Zhe; Hu, Kaili; Li, Yongsheng; Feng, Jianfang; Shi, Jianlin; Gu, Jinlou
      ACS Applied Materials & Interfaces (2015), 7 (22), 11956-11964CODEN: AAMICK; ISSN:1944-8244. (American Chemical Society)
      Development of a rapid and effective method for the detection of 2,4,6-trinitrotoluene (TNT) in aq. phase has attracted great attention. In this work, the fluorescent porphyrin-based metal-org. frameworks (MOFs) of PCN-224 were successfully exploited as a fluorescent probe for the rapid and selective TNT detection in water media. This strategy combined the advantages of fluorescent porphyrin mols. and porous MOFs, which not only overcame the aggregation of hydrophobic tetrakis(4-carboxyphenyl)porphyrin (TCPP) recognition sites but also promoted TNT to interact with recognition sites in virtue of the high surface and intrinsic open structure of MOFs. As a result, a rapid response time of as short as 30 s was obtained for the elaborated fluorescent probe. Meanwhile, the bright red emission of porphyrin units in PCN-224 could be proportionally quenched in correlation with the applied TNT level through the formation of TNT-TCPP complex in the ground state. The specificity of the employed sensory platform for TNT recognition was scarcely affected by other possible coexistent interfering species. Furthermore, this fluorescent PCN-224 probe presented a much higher quenching efficiency for TNT than other structurally similar nitroarom. compds. and was successfully applied for the quant. detection of TNT in the mixed nitroarom. explosive samples. This prefigured their great potentials of practical TNT detection in water media for public safety and security.
    15. 15
      Yang, J.-S.; Swager, T. M. Fluorescent porous polymer films as TNT chemosensors: electronic and structural effects. J. Am. Chem. Soc. 1998, 120 (46), 11864– 11873,  DOI: 10.1021/ja982293q
      15
      Fluorescent Porous Polymer Films as TNT Chemosensors: Electronic and Structural Effects
      Yang, Jye-Shane; Swager, Timothy M.
      Journal of the American Chemical Society (1998), 120 (46), 11864-11873CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
      The synthesis, spectroscopy, and fluorescence quenching behavior of pentiptycene-derived phenyleneethynylene polymers, 1-3, are reported. The incorporation of rigid three-dimensional pentiptycene moieties into conjugated polymer backbones offers several design advantages for solid-state (thin film) fluorescent sensory materials. First, they prevent π-stacking of the polymer backbones and thereby maintain high fluorescence quantum yields and spectroscopic stability in thin films. Second, reduced interpolymer interactions dramatically enhance the soly. of polymers 1-3 relative to other poly(phenyleneethynylenes). Third, the cavities generated between adjacent polymers are sufficiently large to allow diffusion of small org. mols. into the films. These advantages are apparent from comparisons of the spectroscopic and fluorescence quenching behavior of 1-3 to a related planar electron-rich polymer 4. The fluorescence attenuation (quenching) of polymer films upon exposure to analytes depends on several factors, including the exergonicity of electron transfer from excited polymer to analytes, the binding strength (polymer-analyte interactions), the vapor pressure of the analyte, and the rates of diffusion of the analytes in the polymer films. Films of 1-3 are particularly selective toward nitro-arom. compds. The dependence of fluorescence quenching on film thickness provides an addnl. criterion for the differentiation of nitro-arom. compds. from other species, such as quinones. In short, thinner films show a larger response to nitro-arom. compds., but show a lower response to quinones. Such differences are explained in terms of polymer-analyte interactions, which appear to be electrostatic in nature. The rapid fluorescence response (quenching) of the spin-cast films of 1-3 to nitro-contg. compds. qualifies these materials as promising TNT chemosensory materials.
    16. 16
      Nie, H.; Zhao, Y.; Zhang, M.; Ma, Y.; Baumgarten, M.; Müllen, K. Detection of TNT explosives with a new fluorescent conjugated polycarbazole polymer. Chem. Commun. 2011, 47 (4), 1234– 1236,  DOI: 10.1039/C0CC03659E
      16
      Detection of TNT explosives with a new fluorescent conjugated polycarbazole polymer
      Nie, Heran; Zhao, Yang; Zhang, Ming; Ma, Yuguang; Baumgarten, Martin; Muellen, Klaus
      Chemical Communications (Cambridge, United Kingdom) (2011), 47 (4), 1234-1236CODEN: CHCOFS; ISSN:1359-7345. (Royal Society of Chemistry)
      A novel fluorescent poly(2,7-carbazole) with a 4-[tris-(4-octyloxyphenyl)methyl]phenyl side chain is used to detect the explosive compds. TNT and DNT. It shows high recycled fluorescence quenching sensitivity, which is due to its strong electron donating ability and weaker interaction between the polymer chains caused by the bulky side chain.
    17. 17
      Xu, B.; Wu, X.; Li, H.; Tong, H.; Wang, L. Selective detection of TNT and picric acid by conjugated polymer film sensors with donor–acceptor architecture. Macromolecules 2011, 44 (13), 5089– 5092,  DOI: 10.1021/ma201003f
      17
      Selective Detection of TNT and Picric Acid by Conjugated Polymer Film Sensors with Donor-Acceptor Architecture
      Xu, Bowei; Wu, Xiaofu; Li, Haibo; Tong, Hui; Wang, Lixiang
      Macromolecules (Washington, DC, United States) (2011), 44 (13), 5089-5092CODEN: MAMOBX; ISSN:0024-9297. (American Chemical Society)
      A strong donor-acceptor polymer P1 and two donor-only polymers P2 and P3 are designed and synthesized on the basis of the rational anal. of the electrostatic potential and the LUMO distribution for highly selective and sensitive detection of TNT and picric acid in aq. solns., resp. Although their emission in soln. states is very poor, spin-coating films of these AIE-active polymers exhibit bright emission. For the P1 film, the Stern-Volmer quenching const., Ksv of TNT (1.2 ×. 105 M-1) is almost 2 orders higher than that of picric acid (1.8 × 103 M-1), and the detection limit of TNT is about 23 ppb, while the emission of the P3 film can be selectively quenched by the picric acid with the Ksv const. 2.8 × 104 M-1 and the detection limit 2 ppb. These quenching effects of both TNT and picric acid on the P1 and P3 films are found to be reversible. In addn., it was also demonstrated that the emission of P1 and P3 films could be efficiently quenched by TNT and DNT vapors.
    18. 18
      He, G.; Yan, N.; Yang, J.; Wang, H.; Ding, L.; Yin, S.; Fang, Y. Pyrene-containing conjugated polymer-based fluorescent films for highly sensitive and selective sensing of TNT in aqueous medium. Macromolecules 2011, 44 (12), 4759– 4766,  DOI: 10.1021/ma200953s
      18
      Pyrene-Containing Conjugated Polymer-Based Fluorescent Films for Highly Sensitive and Selective Sensing of TNT in Aqueous Medium
      He, Gang; Yan, Ni; Yang, Jiayu; Wang, Hongyue; Ding, Liping; Yin, Shiwei; Fang, Yu
      Macromolecules (Washington, DC, United States) (2011), 44 (12), 4759-4766CODEN: MAMOBX; ISSN:0024-9297. (American Chemical Society)
      Two poly(pyrene-co-phenyleneethynylene)s of different compns. (PyPE-1 and PyPE-2) were synthesized and characterized. The two polymers had been casted, sep., onto glass plate surfaces to fabricate films (film 1, film 2) for sensing performance studies. The fluorescence emissions of the two films are sensitive to the presence of 2,4,6-trinitrotoluene (TNT) in aq. phase. TNT shows little effect upon the emission of the parent polymer, poly(phenyleneethynylene) (PPE). The difference was explained by considering (1) the π-π interaction between pyrene moieties contained in the copolymers and the analyte, TNT, mols., and (2) more suitable matching of the LUMOs of the pyrene-contg. conjugated polymers with that of TNT mols. Further the sensing is reversible and rarely encounters interference from commonly found compds., including other nitroaroms. (NACs). Fluorescence lifetime measurements revealed that the quenching is static in nature. The smart performance of the films and the easiness of their prepn. guarantee that the films may be developed into sensor devices for the supersensitive detection of TNT in groundwater or seawater.
    19. 19
      Lee, J. Y.; Root, H. D.; Ali, R.; An, W.; Lynch, V. M.; Bähring, S.; Kim, I. S.; Sessler, J. L.; Park, J. S. Ratiometric turn-On fluorophore displacement ensembles for nitroaromatic explosives detection. J. Am. Chem. Soc. 2020, 142 (46), 19579– 19587,  DOI: 10.1021/jacs.0c08106
      19
      Ratiometric Turn-On Fluorophore Displacement Ensembles for Nitroaromatic Explosives Detection
      Lee, Ji Yoon; Root, Harrison D.; Ali, Rashid; An, Won; Lynch, Vincent M.; Bahring, Steffen; Kim, In Su; Sessler, Jonathan L.; Park, Jung Su
      Journal of the American Chemical Society (2020), 142 (46), 19579-19587CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
      There is a recognized need in the area of explosives detection for fluorescence-based sensing systems that are capable of not only producing a turn-on response but also generating a distinctive spectral signature for a given analyte. Here, several supramol. ensembles are reported displaying efficient fluorophore displacement that give rise to an increase in fluorescence intensity upon exposure to various nitroarom. compds. The synthetic supramol. constructs in question consist of a tetrathiafulvalene (TTF)-based pyrrolic macrocycle, benzo-TTF-calix[4]pyrrole (Bz-TTF-C4P), and fluorescent dyes, monomeric or dimeric naphthalenediimide (NDI) and perylenediimide (PDI) derivs., as well as chloride or hexafluorophosphate (PF6-) salts of rhodamine 6G (Rh-6G). In chloroform soln., these assemblies exist in the form of discrete supramol. complexes or oligomeric aggregates depending on the specific dye combinations in question. Each ensemble was tested as a potential explosive-responsive fluorescence indicator displacement assay (FIDA) by challenging it with a series of di- and trinitroarom. compds. and examg. the change in fluorescence spectral characteristics. Upon addn. of nitroarom. compds. (NACs), either a "turn-on" or a "turn-off" fluorescent response was obsd. depending on the nature of the constituent fluorophore and, where applicable, the counteranion. The FIDAs based on the PDI derivs. were found to display not only a ratiometric fluorescence enhancement but also analyte-dependent spectral changes when treated with NACs. The NAC-induced fluorescence spectral response of each ensemble was rationalized on the basis of various soln.-phase spectroscopic studies, as well as single-crystal X-ray diffraction analyses.
    20. 20
      Climent, E.; Biyikal, M.; Gröninger, D.; Weller, M. G.; Martínez-Máñez, R.; Rurack, K. Multiplexed Detection of Analytes on Single Test Strips with antibody-gated indicator-releasing mesoporous nanoparticles. Angew. Chem., Int. Ed. 2020, 59 (52), 23862– 23869,  DOI: 10.1002/anie.202009000
      20
      Multiplexed Detection of Analytes on Single Test Strips with Antibody-Gated Indicator-Releasing Mesoporous Nanoparticles
      Climent, Estela; Biyikal, Mustafa; Groeninger, Delia; Weller, Michael G.; Martinez-Manez, Ramon; Rurack, Knut
      Angewandte Chemie, International Edition (2020), 59 (52), 23862-23869CODEN: ACIEF5; ISSN:1433-7851. (Wiley-VCH Verlag GmbH & Co. KGaA)
      Rapid testing methods for the use directly at a point of need are expected to unfold their true potential esp. when offering adequate capabilities for the simultaneous measurement of multiple analytes of interest. Considering the unique modularity, high sensitivity, and selectivity of antibody-gated indicator delivery (gAID) systems, a multiplexed assay for three small-mol. explosives (TATP, TNT, PETN) was thus developed, allowing to detect the analytes simultaneously with a single test strip at lower ppb concns. in the liq. phase in <5 min using a fluorescence reader or a smartphone for readout. While the TNT and PETN systems were newly developed here, all the three systems also tolerated harsher matrixes than buffered aq. model solns. Besides a single-track strip, the outstanding modularity of the hybrid biosensor materials in combination with strip-patterning technologies allowed us to obtain a multichannel strip in a straightforward manner, offering comparable anal. performance while allowing to be tailored even more to the user's need.
    21. 21
      Wan, W.-M.; Tian, D.; Jing, Y.-N.; Zhang, X.-Y.; Wu, W.; Ren, H.; Bao, H.-L. NBN-doped conjugated polycyclic aromatic hydrocarbons as an AIEgen class for extremely sensitive detection of explosives. Angew. Chem., Int. Ed. 2018, 57 (47), 15510– 15516,  DOI: 10.1002/anie.201809844
      21
      NBN-Doped Conjugated Polycyclic Aromatic Hydrocarbons as an AIEgen Class for Extremely Sensitive Detection of Explosives
      Wan, Wen-Ming; Tian, Di; Jing, Ya-Nan; Zhang, Xiao-Yun; Wu, Wei; Ren, Hao; Bao, Hong-Li
      Angewandte Chemie, International Edition (2018), 57 (47), 15510-15516CODEN: ACIEF5; ISSN:1433-7851. (Wiley-VCH Verlag GmbH & Co. KGaA)
      A simple and efficient synthesis of NBN-doped conjugated polycyclic arom. hydrocarbons (such as diazaborinines) has been accomplished by a catalyst-free intermol. dehydration reaction at room temp. between boronic acid and diamine moieties with yields up to 99 %. Polycyclic arom. hydrocarbons with a six-membered NBN ring are a new class of aggregation-induced emissive luminogens. Extremely sensitive detection of ppb levels of TNT by Ph naphthodiazaborinine is straightforward. Visual detection of TNT is illustrated by fabrication of TNT test strips, which can detect as little as 100 ng of TNT powder. This simple and sensitive detection of TNT has potential applications in the area of public safety and security against terrorist activities.
    22. 22
      Tanwar, A. S.; Hussain, S.; Malik, A. H.; Afroz, M. A.; Iyer, P. K. Inner filter effect based selective detection of nitroexplosive-picric acid in aqueous solution and solid support using conjugated polymer. ACS Sens. 2016, 1 (8), 1070– 1077,  DOI: 10.1021/acssensors.6b00441
      22
      Inner Filter Effect Based Selective Detection of Nitroexplosive-Picric Acid in Aqueous Solution and Solid Support Using Conjugated Polymer
      Tanwar, Arvin Sain; Hussain, Sameer; Malik, Akhtar Hussain; Afroz, Mohammad Adil; Iyer, Parameswar Krishnan
      ACS Sensors (2016), 1 (8), 1070-1077CODEN: ASCEFJ; ISSN:2379-3694. (American Chemical Society)
      A new polyfluorene deriv., poly[4,4'-(((2-phenyl-9H-fluorene-9,9-diyl)bis(hexane-6,1-diyl))bis(oxy))dianiline)] (PFAM) was synthesized via the Suzuki coupling polymn. method in high yields for the rapid and specific recognition of nitroexplosive picric acid (PA) at 22.9 pg level on solid support using paper strips and at 13.2 ppb level in aq. soln. The polymer PFAM was well-characterized by means of NMR, UV-vis, fluorescence, time-resolved photoluminescence (TRPL) spectroscopy, and cyclic voltammetry. The amplified signal response exclusively for PA was achieved via a strong inner filter effect (IFE), a phenomenon different from the widely reported ground-state charge transfer and/or Forster resonance energy transfer (FRET) based probes for nitroaroms. detection. Pendant amine groups attached on the side chains of PFAM provide enhanced sensitivity and exceptional selectivity via protonation assisted photoinduced electron transfer (PET) even in the presence of most common interfering nitroexplosives, as well as other analytes usually found in natural water. Thus, the PFAM based platform was demonstrated for monitoring traces of PA at very low levels even in competitive environment in soln. as well as solid state.
    23. 23
      Kim, H. N.; Guo, Z.; Zhu, W.; Yoon, J.; Tian, H. Recent progress on polymer-based fluorescent and colorimetric chemosensors. Chem. Soc. Rev. 2011, 40 (1), 79– 93,  DOI: 10.1039/C0CS00058B
      23
      Recent progress on polymer-based fluorescent and colorimetric chemosensors
      Kim, Ha Na; Guo, Zhiqian; Zhu, Weihong; Yoon, Juyoung; Tian, He
      Chemical Society Reviews (2011), 40 (1), 79-93CODEN: CSRVBR; ISSN:0306-0012. (Royal Society of Chemistry)
      A review. Recently, fluorescent or colorimetric chemosensors based on polymers have attracted great attention due to several important advantages, such as their simplicity of use, signal amplification, easy fabrication into devices, and combination of different outputs, etc. This tutorial review will cover polymer-based optical chemosensors from 2007 to 2010.
    24. 24
      Thomas, S. W.; Joly, G. D.; Swager, T. M. Chemical sensors based on amplifying fluorescent conjugated polymers. Chem. Rev. 2007, 107 (4), 1339– 1386,  DOI: 10.1021/cr0501339
      24
      Chemical sensors based on amplifying fluorescent conjugated polymers
      Thomas, Samuel W., III; Joly, Guy D.; Swager, Timothy M.
      Chemical Reviews (Washington, DC, United States) (2007), 107 (4), 1339-1386CODEN: CHREAY; ISSN:0009-2665. (American Chemical Society)
      A review. In this review the authors restrict the discussions to purely fluorescence-based methods using conjugated polymers. Amplification, small ion sensing using amplifying fluorescent conjugated polymers (AFPs), AFPs for detection of explosives, conjugated polyelectrolytes as biosensors, AFPs for detection of small biomols., proteins, and DNA are discussed.
    25. 25
      Feng, L.; Li, H.; Qu, Y.; Lü, C. Detection of TNT based on conjugated polymer encapsulated in mesoporous silica nanoparticles through FRET. Chem. Commun. 2012, 48 (38), 4633– 4635,  DOI: 10.1039/c2cc16115j
      25
      Detection of TNT based on conjugated polymer encapsulated in mesoporous silica nanoparticles through FRET
      Feng, Lijuan; Li, Hui; Qu, Ying; Lue, Changli
      Chemical Communications (Cambridge, United Kingdom) (2012), 48 (38), 4633-4635CODEN: CHCOFS; ISSN:1359-7345. (Royal Society of Chemistry)
      Amine-functionalized mesoporous silica nanoparticles contg. poly(p-phenylenevinylene) provide a facile strategy to detect TNT through fluorescence resonance energy transfer (FRET). The obsd. linear fluorescence intensity change allows the quant. detection of TNT with the detection limit of 6 × 10-7 M.
    26. 26
      Novotney, J. L.; Dichtel, W. R. Conjugated porous polymers for TNT vapor detection. ACS Macro Lett. 2013, 2 (5), 423– 426,  DOI: 10.1021/mz4000249
      26
      Conjugated Porous Polymers For TNT Vapor Detection
      Novotney, Jennifer L.; Dichtel, William R.
      ACS Macro Letters (2013), 2 (5), 423-426CODEN: AMLCCD; ISSN:2161-1653. (American Chemical Society)
      A conjugated porous polymer (CPP) that exhibits fluorescence quenching when exposed to TNT vapor was synthesized via a Sonaogashira cross-coupling reaction. Two polymn. solvents, DMF and PhMe, and two activation procedures, evacuation and lyophilization, were evaluated to optimize the response of the CPP to TNT vapor. Key differences in surface area and absorption were seen as a function of polymn. solvent and activation procedure. The polymer synthesized in DMF and activated by lyophilization had the highest surface area and the strongest response to TNT vapor. This paper demonstrates the importance of growth and activation conditions in optimizing the porosity and sensing performance of CPPs.
    27. 27
      Adil, L. R.; Gopikrishna, P.; Iyer, P. K. Receptor-free detection of picric acid: a new structural approach for designing aggregation-induced emission probes. ACS Appl. Mater. Interfaces 2018, 10 (32), 27260– 27268,  DOI: 10.1021/acsami.8b07019
      27
      Receptor-Free Detection of Picric Acid: A New Structural Approach for Designing Aggregation-Induced Emission Probes
      Adil, Laxmi Raman; Gopikrishna, Peddaboodi; Krishnan Iyer, Parameswar
      ACS Applied Materials & Interfaces (2018), 10 (32), 27260-27268CODEN: AAMICK; ISSN:1944-8244. (American Chemical Society)
      A pristine aggregation-induced enhanced emission (AIEE) active monomer 2,5-bis((E)-4-bromostyryl)-3,4-diphenylthiophene (TPBZ) and its copolymer (PFTPBZ) with 9,9-dioctylfluorene-2,7-diboronic acid bis(1,3-propandiol) ester were synthesized via Suzuki coupling polymn. PFTPBZ that is devoid of any receptor showed AIEE property and demonstrated excellent and selective fluorometric recognition of 2,4,6-trinitrotoluene (TNT) in aggregated state (aq. medium) and picric acid (PA) in aggregated state and soln. state (org. solvent) as well as in vapor phase via PFTPBZ dip-coated Whatman filter paper on a solid-phase platform in 1.86 ng level (naked eye). Limit of detection (LOD) for TNT in 95% water fraction (fw) was 53.74 × 10-6 M, and at 40% fw, it was 14.26 × 10-7 M. PA detection in THF soln. was possible with a LOD of 28.16 × 10-7 M, 95% fw with LOD of 10.47 × 10-6 M, and in 40% fw with LOD of 47.39 × 10-8 M. As a unique example of structural design, the probe PFTPBZ surprisingly possesses no receptor, yet remarkably high selectivity was achieved via Forster resonance energy transfer (FRET) and photoinduced electron transfer from the copolymer PFTPBZ to PA and TNT. Detection of PA in the presence of various metal analytes and inorg. acids in real water samples (lakes, rivers, and sea water) was also demonstrated using this concept of receptor-free conjugated polymer probe.
    28. 28
      Tanwar, A. S.; Adil, L. R.; Afroz, M. A.; Iyer, P. K. Inner filter effect and resonance energy transfer based attogram level detection of nitroexplosive picric acid using dual emitting cationic conjugated polyfluorene. ACS Sens. 2018, 3 (8), 1451– 1461,  DOI: 10.1021/acssensors.8b00093
      28
      Inner Filter Effect and Resonance Energy Transfer Based Attogram Level Detection of Nitroexplosive Picric Acid Using Dual Emitting Cationic Conjugated Polyfluorene
      Tanwar, Arvin Sain; Adil, Laxmi Raman; Afroz, Mohammad Adil; Iyer, Parameswar Krishnan
      ACS Sensors (2018), 3 (8), 1451-1461CODEN: ASCEFJ; ISSN:2379-3694. (American Chemical Society)
      A novel conjugated cationic polyfluorene (polyelectrolyte) deriv., PFBT, was developed by means of simple and cost-effective oxidative coupling polymn. method. PFBT displayed dual state emission in DMSO as well as in water, a characteristic phenomenon of polyfluorene homopolymers, and tested for nitroexplosive analytes detection to observe a remarkable fluorescence quenching response for picric acid (PA) in the both solvents. The polymer PFBT demonstrated substantial selectivity and ultrasensitivity toward nitroexplosive PA in both the solvents (DMSO and H2O) with exceptional quenching const. values of 2.69 × 104 and 2.18 × 105 M-1 and a ultralow limit of detection of 92.7 nM (21.23 ppb) and 0.19 nM (43.53 ppt) in resp. solvents. Furthermore, economical portable test strip devices were prepd. for easy and fast on-site PA sensing, which can detect up to 0.22 ag level of PA. PA sensing in vapor phase was also established, that could detect up to 42.6 ppb level of PA vapors. Interestingly, the mechanism of sensing in DMSO solvent was attributed to substantial inner filter effect and photoinduced electron transfer, while in H2O the sensing occurs via possible resonance energy transfer and photoinduced electron transfer, which is exceptional and not reported earlier for a single probe.
    29. 29
      Tanwar, A. S.; Patidar, S.; Ahirwar, S.; Dehingia, S.; Iyer, P. K. Receptor free” inner filter effect based universal sensors for nitroexplosive picric acid using two polyfluorene derivatives in the solution and solid states. Analyst 2019, 144 (2), 669– 676,  DOI: 10.1039/C8AN01970C
      29
      "Receptor free" inner filter effect based universal sensors for nitroexplosive picric acid using two polyfluorene derivatives in the solution and solid states
      Tanwar, Arvin Sain; Patidar, Sourabh; Ahirwar, Saurabh; Dehingia, Sourav; Iyer, Parameswar Krishnan
      Analyst (Cambridge, United Kingdom) (2019), 144 (2), 669-676CODEN: ANALAO; ISSN:0003-2654. (Royal Society of Chemistry)
      Two receptor-free blue fluorescent conjugated polymers (CPs) of fluorene namely 9,9-bis(6-bromohexyl)-2-phenyl-9H-fluorene (PF1) and 9,9-bis(6-bromohexyl)-9H-fluorene (PF2) were synthesized using Suzuki cross coupling polymn. and oxidative coupling polymn. methods in high yields and well characterized by gel permeable chromatog., NMR, UV-vis, fluorescence and time-resolved photoluminescence (TRPL) spectroscopy. Both CPs explicitly recognized nitroexplosive picric acid (PA) and displayed a fluorescence quenching response in soln. and on a solid support via the inner filter effect (IFE) mechanism. Both CPs were highly selective and sensitive towards PA with high quenching const. values (Ksv) of 5.1 × 104 M-1 and 5.0 × 104 M-1 and remarkably low limit of detection (LOD) values of 110 nM and 219 nM. Contact mode detection of PA was also accomplished using economical and transportable fluorescent paper test strip devices for on-site sensing, which detect a min. of 22.9 fg of PA. The IFE mechanism for PA sensing (or for other analytes) is an interesting concept that can detect PA by just having blue fluorescence. Therefore, careful expts. for IFE correction were performed herein for PA detection to observe ∼77% suppression efficiency due to the IFE. These studies provide fundamentally important information on the IFE based mechanism for the detection of various analytes.
    30. 30
      Hussain, S.; Malik, A. H.; Afroz, M. A.; Iyer, P. K. Ultrasensitive detection of nitroexplosive – picric acid via a conjugated polyelectrolyte in aqueous media and solid support. Chem. Commun. 2015, 51 (33), 7207– 7210,  DOI: 10.1039/C5CC02194D
      30
      Ultrasensitive detection of nitroexplosive - picric acid via a conjugated polyelectrolyte in aqueous media and solid support
      Hussain, Sameer; Malik, Akhtar Hussain; Afroz, Mohammad Adil; Iyer, Parameswar Krishnan
      Chemical Communications (Cambridge, United Kingdom) (2015), 51 (33), 7207-7210CODEN: CHCOFS; ISSN:1359-7345. (Royal Society of Chemistry)
      Picric acid (PA) detection at parts per trillion (ppt) levels is achieved by a conjugated polyelectrolyte (PMI) in 100% aq. media and on a solid platform using paper strips and chitosan (CS) films. The unprecedented selectivity is accomplished via combination of ground state charge transfer and resonance energy transfer (RET) facilitated by favorable electrostatic interactions.
    31. 31
      Lakowicz, J. R. Principles of Fluorescence Spectrosopy, 3rd ed.; Springer: Singapore, 2010.
      There is no corresponding record for this reference.
    32. 32
      Tanwar, A. S.; Meher, N.; Adil, L. R.; Iyer, P. K. Stepwise elucidation of fluorescence based sensing mechanisms considering picric acid as a model analyte. Analyst 2020, 145 (14), 4753– 4767,  DOI: 10.1039/D0AN00732C
      32
      Stepwise elucidation of fluorescence based sensing mechanisms considering picric acid as a model analyte
      Tanwar, Arvin Sain; Meher, Niranjan; Adil, Laxmi Raman; Iyer, Parameswar Krishnan
      Analyst (Cambridge, United Kingdom) (2020), 145 (14), 4753-4767CODEN: ANALAO; ISSN:0003-2654. (Royal Society of Chemistry)
      A review. In most of the sensing systems, specific detection mechanisms are involved during the detection process for a certain analyte irresp. of probes. However, unlike that of various sensing analytes, the detection of the highly toxic and explosive picric acid (PA) analyte was found to involve significant types of distinct sensing mechanisms depending on the nature of probes. Moreover, in the past five years, apart from the plethora of fluorescent probes designed, a no. of unique org. small mols. and polymers have been strategically developed at our lab. for the detection of PA, wherein the involvement of several diverse mechanisms along with a few new mechanisms depending on the electronic and photophys. properties of the probes has been unveiled. This involvement of several distinct mechanisms for the detection of PA motivated us to compile a step-by-step guide for the elucidation of the fluorescence sensing mechanism by taking PA as a model analyte. This "tutorial review" summarizes all the common sensing mechanisms involved for the detection of PA hitherto and provides a step-by-step guide to design expts. for the elucidation of sensing mechanisms for any newly designed sensing system. In addn. to the appropriate classification of mechanisms involved for the fluorescence sensing of PA using various fluorescent systems developed at our lab., this tutorial review also includes most other possible mechanistic approaches studied previously. The present tutorial also provides a very unique method of a flow chart, which could help readers to elucidate the likely sensing mechanism via stepwise exptl. and theor. studies. Apart from the elucidation of the sensing mechanism for PA, this review presents an easy and distinct approach for the identification of all the involved mechanisms that would be of primary concern in the detection process of any analyte and could accurately help researchers in the easy and quick elucidation of sensing mechanisms in any kind of fluorophore-analyte system.
    33. 33
      Xu, S.; Lu, H.; Li, J.; Song, X.; Wang, A.; Chen, L.; Han, S. Dummy Molecularly Imprinted Polymers-Capped CdTe Quantum Dots for the Fluorescent Sensing of 2,4,6-Trinitrotoluene. ACS Appl. Mater. Interfaces 2013, 5 (16), 8146– 8154,  DOI: 10.1021/am4022076
      33
      Dummy Molecularly Imprinted Polymers-Capped CdTe Quantum Dots for the Fluorescent Sensing of 2,4,6-Trinitrotoluene
      Xu, Shoufang; Lu, Hongzhi; Li, Jinhua; Song, Xingliang; Wang, Aixiang; Chen, Lingxin; Han, Shaobo
      ACS Applied Materials & Interfaces (2013), 5 (16), 8146-8154CODEN: AAMICK; ISSN:1944-8244. (American Chemical Society)
      Molecularly imprinted polymers (MIPs) with trinitrophenol (TNP) as a dummy template mol. capped with CdTe quantum dots (QDs) were prepd. using 3-aminopropyltriethoxy silane (APTES) as the functional monomer and tetraethoxysilane (TEOS) as the cross linker through a seed-growth method via a sol-gel process (i.e., DMIP@QDs) for the sensing of 2,4,6-trinitrotoluene (TNT) from electron-transfer-induced fluorescence quenching. With the presence and increase of TNT in sample solns., a Meisenheimer complex was formed between TNT and the primary amino groups on the surface of the QDs. The energy of the QDs was transferred to the complex, resulting in the quenching of the QDs and thus decreasing the fluorescence intensity, which allowed the TNT to be sensed optically. DMIP@QDs generated a significantly reduced fluorescent intensity within <10 min upon binding TNT. The fluorescence-quenching fractions of the sensor presented a satisfactory linearity with TNT concns. at 0.8-30 μM, and its limit of detection could reach 0.28 μM. The sensor exhibited distinguished selectivity and a high binding affinity to TNT over its possibly competing mols. of 2,4-dinitrophenol (DNP), 4-nitrophenol (4-NP), phenol, and dinitrotoluene (DNT) because there are more nitro groups in TNT and therefore a stronger electron-withdrawing ability and because it has a high similarity in shape and vol. to TNP. The sensor was successfully applied to det. the amt. of TNT in soil samples, and the av. recoveries of TNT at three spiking levels ranged from 90.3 to 97.8% with relative std. deviations <5.12%. The results provided an effective way to develop sensors for the rapid recognition and detn. of hazardous materials from complex matrixes.
    34. 34
      Zhu, H.; Zhang, H.; Xia, Y. Planar Is Better: Monodisperse Three-Layered MoS2 Quantum Dots as Fluorescent Reporters for 2,4,6-Trinitrotoluene Sensing in Environmental Water and Luggage Cases. Anal. Chem. 2018, 90 (6), 3942– 3949,  DOI: 10.1021/acs.analchem.7b04893
      34
      Planar Is Better: Monodisperse Three-Layered MoS2 Quantum Dots as Fluorescent Reporters for 2,4,6-Trinitrotoluene Sensing in Environmental Water and Luggage Cases
      Zhu, Hui; Zhang, Hui; Xia, Yunsheng
      Analytical Chemistry (Washington, DC, United States) (2018), 90 (6), 3942-3949CODEN: ANCHAM; ISSN:0003-2700. (American Chemical Society)
      The authors present a simple but effective fluorescent system for highly sensitive and versatile sensing of 2,4,6-trinitrotoluene (TNT) using few layered planar MoS2 quantum dots (QDs) as reporters. Excitation-independent emitting MoS2 QDs were 1st fabricated by using the proposed ultrasonic-hydrothermal-based top-down method assisted by carbon-free hydroxylamine hydrochloride. The obtained pristine MoS2 QDs were then modified with cysteine for introducing amino groups as TNT binding sites. The as-prepd. MoS2 QDs possess a planar structure, which can more adequately interact with flat arom. TNT mols. due to π-π attraction and decreased steric effects, compared with traditional spherical/quasi-spherical QDs. As a result, they exhibit extremely high sensitivity for TNT sensing (1 nM and 2 ng for soln. and substrate assay, resp.). The common ions contg. in environmental water samples do not interfere with the sensing. Also, the QDs-decorated test paper shows an instantaneous (within 1 min) response to trace amts. of deposited TNT, and the fluorescence quenching can even be well-visualized by the naked eye. Because of favorable anal. performances, the proposed MoS2 QDs-based TNT sensing system has potential applications in both environmental water monitoring and security screening.

  • Supporting Information

    Supporting Information

    The Supporting Information is available free of charge at https://pubs.acs.org/doi/10.1021/acsmeasuresciau.1c00023.

    • All the characterization data such as NMR spectra, GPC, UV–vis, and PL spectra, LoD plot, table of comparison, IFE and RET calculations, sensing photographs in solution and on paper (PDF)


    Terms & Conditions

    Most electronic Supporting Information files are available without a subscription to ACS Web Editions. Such files may be downloaded by article for research use (if there is a public use license linked to the relevant article, that license may permit other uses). Permission may be obtained from ACS for other uses through requests via the RightsLink permission system: http://pubs.acs.org/page/copyright/permissions.html.