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Electrogenerated Chemiluminescence for Chronopotentiometric SensorsClick to copy article linkArticle link copied!
- Wenyue GaoWenyue GaoDepartment of Inorganic and Analytical Chemistry, University of Geneva, Quai Ernest-Ansermet 30, CH-1211 Geneva, SwitzerlandDepartment of Chemistry, Southern University of Science and Technology, Shenzhen 518055, ChinaMore by Wenyue Gao
- Stéphane JeanneretStéphane JeanneretDepartment of Inorganic and Analytical Chemistry, University of Geneva, Quai Ernest-Ansermet 30, CH-1211 Geneva, SwitzerlandMore by Stéphane Jeanneret
- Dajing YuanDajing YuanDepartment of Inorganic and Analytical Chemistry, University of Geneva, Quai Ernest-Ansermet 30, CH-1211 Geneva, SwitzerlandMore by Dajing Yuan
- Thomas CherubiniThomas CherubiniDepartment of Inorganic and Analytical Chemistry, University of Geneva, Quai Ernest-Ansermet 30, CH-1211 Geneva, SwitzerlandMore by Thomas Cherubini
- Lu WangLu WangDepartment of Inorganic and Analytical Chemistry, University of Geneva, Quai Ernest-Ansermet 30, CH-1211 Geneva, SwitzerlandMore by Lu Wang
- Xiaojiang Xie*Xiaojiang Xie*Xiaojiang Xie. E-mail: [email protected]Department of Chemistry, Southern University of Science and Technology, Shenzhen 518055, ChinaMore by Xiaojiang Xie
- Eric Bakker*Eric Bakker*Eric Bakker. E-mail: [email protected]Department of Inorganic and Analytical Chemistry, University of Geneva, Quai Ernest-Ansermet 30, CH-1211 Geneva, SwitzerlandMore by Eric Bakker
Analytical Chemistry
Cite this: Anal. Chem. 2019, 91, 7, 4889–4895
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Abstract
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We introduce here a general strategy to read out chronopotentiometric sensors by electrogenerated chemiluminescence (ECL). The potentials generated in chronopotentiometry in a sample compartment are used to control the ECL in a separate detection compartment. A three-electrode cell is used to monitor the concentration changes of the analyte, while the luminol–H2O2 system is responsible for ECL. The principle was shown to be feasible by theoretical simulations, indicating that the sampled times at a chosen potential, rather than traditional transition times, similarly give linear behavior between concentration and the square root of sampled time. With the help of a voltage adapter, the experimental combination between chronopotentiometry and ECL was successfully implemented. As an initial proof of concept, the ferro/ferricyanide redox couple was investigated. The square root of time giving maximum light output changed linearly with ferrocyanide concentration in the range from 0.70 to 4.81 mM. The method was successfully applied to the visual detection of carbonate alkalinity from 0.06 to 0.62 mM using chronopotentiometry at an ionophore-based hydrogen ion-selective membrane electrode. The measurements of carbonate in real samples including river water and commercial mineral water were successfully demonstrated.
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Copyright © 2019 American Chemical Society
The conversion of electrochemical signals to visual readout is of great significance in analytical science, especially for the development of simple, easy to use and low-cost sensing devices. Not only do the electrochemical detection methods (voltammetry, amperometry, potentiometry, conductometry, and electrochemical impedance spectroscopy) possess the advantages of simplicity, fast responses, and ease of use, but also the instruments needed to perform the analysis can be miniaturized to low-cost microscale dimensions. (1−4) However, electrochemical signals are normally not intuitive and need numerical algorithms to allow for an interpretation of the data. Moreover, electrochemical methods become overly complex when extended to chemical detection in two dimensions and multiple channels. The visualization of chemical changes by means of imaging tools and parallel arrays has great promise for these applications. (5) It is therefore attractive to read out electrochemical signal with optical methods. Liu and Crooks previously developed a microelectrochemical sensing platform realizing such signal transduction through the electrochromic effect. (6) Gooding’s group used similar electrochromic effect to read out potentiometric pH sensor and resistive-based sensors. (7,8) Wang and co-workers contributed a lot to the visualization of electrochemical sensing events based on bipolar electrodes. (9−14) Recently, our group reported on a strategy to convert potentiometric signals to a colorimetric readout through the turnover of a redox indicator in a thin layer using a closed bipolar electrode, (15) although this has not been applied to dynamic electrochemistry protocols such as chronopotentiometry. An electrochemical-to-optical signal transduction scheme was also demonstrated under chronoamperometry control with light-emitting diodes as indicators. (16)
In addition to color change, electrogenerated chemiluminescence (ECL) has also been used to provide a direct optical readout for potentiometric sensors. (17) ECL is an attractive combination of spectroscopic and electrochemical methodologies. It shows great potential for designing portable sensing devices because there is no need for an additional excitation light source and the ECL emission signal can be observed visually or with digital cameras. (18−24) In the above-mentioned work, (17) an ion-selective sensing electrode was placed in a sample physically separated from the ECL detection compartment. It was then treated as the reference electrode in order to modulate the potential at the working electrode used for ECL generation. Because two physically separate compartments were used for sensing and detection, ECL generation is not influenced by the sample composition.
Here, a general strategy is proposed to convert chronopotentiometric signals to ECL readout. In chronopotentiometry, a constant current is applied across the electrochemical cell. The output signal is the cell potential, which changes drastically at the so-called transition time. This transition time is concentration dependent and serves as the analytical signal. The strategy of this work is for the chronopotentiometric experiment to give a light pulse at a time that indicates the analyte concentration. This would be quite easily detectable by a camera or even by the naked eye and be a major advantage compared to intensity-based measurements for field deployable devices.
To achieve this, the time dependent potential change is applied to the detection compartment as voltage input to generate ECL. As luminol is one of the most efficient ECL luminophores, emitting blue light in the presence H2O2, (25−27) it was chosen to generate ECL. The concept is successfully demonstrated with the ferro/ferricyanide redox couple at a conventional glassy carbon electrode and carbonate alkalinity detection at a hydrogen ion-selective electrode (ISE). Theoretical simulations accompany the experimental results. The use of the approach is demonstrated by visual detection of carbonate in river and commercial mineral water samples.
Experimental Section
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Reagents
Potassium tetrakis[3,5-bis(trifluoromethyl)phenyl]borate (KTFPB), tetrakis(4-chlorophenyl)borate tetradodecylammonium salt (ETH 500), chromoionophore I, 2-nitrophenyloctyl ether (o-NPOE), tris(hydroxymethyl)aminomethane (Tris), potassium ferricyanide, potassium ferrocyanide, acetic acid, sodium acetate, sodium chloride, luminol, hydrogen peroxide solution (35%), hydrochloric acid solution (1 M), and tetrahydrofuran (THF) were purchased from Sigma-Aldrich. All chemicals were of analytical grade and used without further purification.
Analytical Setup
A double-junction Ag/AgCl reference electrode was used in chronopotentiometric measurements (Mettler-Toledo AG, Schwerzenbach, Switzerland). A platinum electrode with a diameter of 3.0 mm (Metrohm, Switzerland) was used as counter electrode both in chronopotentiometric methods and in ECL measurements. A glassy carbon electrode of 3.0 mm diameter purchased from Metrohm Autolab was used as the working electrode to generate ECL and also used as the working electrode in the ferrocyanide detection system. For ion-selective electrode preparation, electrode bodies (Oesch Sensor Technology, Sargans, Switzerland) were used to mount the ion-selective membranes. Porous polypropylene (PP) membranes (Celgard, 0.237 cm2 surface area, 20 μm thickness) were kindly provided by Membrane Wuppertal, Germany. pH values were determined using a Metrohm 827 pH meter (Metrohm Autolab, Utrecht, The Netherlands).
The electrochemical measurements were performed with an Autolab PGSTAT128N (Metrohm Autolab, Utrecht, The Netherlands) controlled by a personal computer using Nova 2.1.3 software (supplied by Autolab). A panoramic picture of the setup is shown in Figure S1a. The homemade cell used for ECL measurement is shown in Figure S1b. ECL signals were video recorded by a digital camera (Canon EOS 5D Mark III with EF 100 mm f/2.8L Macro IS USM lens) operated in a dark box. The images of the ECL emission were extracted and analyzed by Wolfram Mathematica 11 software. A voltage adapter was designed and fabricated in house (picture shown in Figure S1c). It consists of an amplifier followed by an adder. The user can choose different fixed gains (0.5, 1, 2, 3, 5) and also set the offset (between −1 and +1 V). The adapter circuit uses precision operational amplifiers (TI OPA277) that have low bias current and low offset voltage. They are powered internally using an internal dc/dc converter (XP Power IH0512S) that is followed by linear regulators (ST L7808 and ST L7809) that provides power rails at +8 and −8 V. The gains are set using a rotary encoder that selects precalibrated feedback resistors that permits us to choose the gain. While the offset is selected by a precision 10-turn potentiometer, its value is displayed on a display (TDE Instruments DPM961TG). A second display (TDE Instruments DPM961TG) is provided to read the output value.
Ion-selective Membrane Preparation
The ion-selective membrane for the detection of alkalinity was prepared according to the literature. (28) The cocktail H1 used for the membrane preparation was prepared by dissolving a mixture of 120 mmol/kg of chromoionophore I, 60 mmol/kg of KTFPB, 90 mmol/kg of ETH 500, and 190 mg of o-NPOE in 1 mL of THF. The PP membrane used as supporting material was washed with THF for 10 min. When THF was completely evaporated, an excess volume of 4 μL of the cocktail H1 solution was deposited on the membrane. It was dried overnight at room temperature in a dust-free environment. After conditioning in buffer solution for 40 min, the membrane was mounted in the electrode body. The inner compartment was filled with 10 mM acetic acid/10 mM sodium acetate buffer (1/1) in 100 mM NaCl. All solutions were prepared in 100 mM NaCl as background electrolyte to minimize electrical migration.
Experimental Protocols
Chronopotentiometric experiments were performed in 100 mM NaCl as a background electrolyte with a galvanostatic pulse of 10 s. The potential was recorded as a function of time during the constant current pulse. After each chronopotentiometric determination, an opposite galvanostatic pulse was applied to recover the ferro/ferricyanide redox couple or to regenerate the ionophore-based hydrogen ion-selective membrane for carbonate detection. (29) For the ferrocyanide detection system, a constant current of 30 μA was applied and the dynamic response curves were obtained by adding predefined aliquots of standard solution (0.5 M potassium ferrocyanide solution and 0.5 M potassium ferricyanide solution) to a magnetically stirred background electrolyte. The use of equal amounts of ferricyanide and ferrocyanide maintains a stable starting potential of the system. For the carbonate sensing system, the stock solution was prepared from 1.0 M carbonate and 1.0 M bicarbonate solution, adjusting the pH to 9.6. Calibration curves were obtained by adding precise amounts of carbonate stock solution into the magnetically stirred background electrolyte. Freely dissolved CO2 was removed before measurements using nitrogen gas and a homemade capping seal. (29) Before each galvanostatic pulse, the pH value of the detection solution was measured with a Metrohm pH electrode and pH meter. The precise carbonate concentration was calculated from the pH value and the total carbonate concentration added. The potential generated in chronopotentiometry was output through the electrochemical workstation (Autolab PGSTAT128N) and modulated by the voltage adapter to fit the ECL requirements. The solution used in the ECL emission compartment was composed of 1 mM luminol and 5 mM H2O2 in 0.1 M phosphate buffer solution (pH 11.0).
Results and Discussion
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Figure 1 shows the schematic configuration of the cell that achieves an ECL readout for a chronopotentiometric sensor. In chronopotentiometry, a constant current is applied across the electrochemical cell. The output signal is the cell potential, which changes over time and is applied to the detection compartment as voltage input to generate ECL. As time proceeds, the concentration of the electroactive species at the electrode surface will be depleted at a transition time τ, giving a drastic change in potential. (30−32) According to the Sand equation, the square root of the transition time should be linearly dependent on the concentration of the locally depleted species as follows: (33,34)
where i is the applied current, cj is the initial concentration of analyte j, n is the number of transferred electrons (for ion-selective membranes, n becomes z, the valency of j), F is the Faraday constant, A is the electrode area, and Dj is the diffusion coefficient of j. The time at which ECL reaches maximum intensity should coincide with the chronopotentiometric transition time, which is achieved with the help of a voltage adapter. In this manner the analyte concentration in the sample compartment may be translated into a time dependent light pulse.
(1)
Figure 1
Figure 1. Schematic illustration of the proposed sensing approach converting chronopotentiometric signals in a sample compartment to a timed ECL pulse that can be captured by a camera. A glassy carbon electrode or an ion-selective electrode was used as the working electrode (WE1), platinum counter electrode (CE1), and double-junction Ag/AgCl/3 M KCl/1 M LiOAc reference electrode (RE) were used in chronopotentiometric measurements. In the ECL detection compartment, a glassy carbon electrode was used as the working electrode (WE2) to generate light, and a platinum electrode was used as counter electrode (CE2) to form a closed circuit.
To explain the working principle, a theoretical simulation of chronopotentiometric responses was made with the finite difference method (see the Supporting Information for details). (35) The simulated chronopotentiograms are shown in Figure 2a. The luminol/H2O2 system generates an ECL signal in the potential range from 0.2 to 1.0 V and gives a maximum intensity near 0.46 V on the surface of the glassy carbon electrode. (36−38) We therefore need to evaluate whether the square root of time at a given potential value (τE) still follows a linear relationship with analyte concentration. To test this, the times τE at which the chronopotentiometric responses reached a predefined potential for varying concentrations were extracted. Indeed, as shown in Figure 2b, the square root of τE shows a linear relationship with concentration. Surprisingly, linearity appears to hold even at chosen potentials that are far from the location of the inflection point.
Figure 2
Figure 2. (a) Simulated chronopotentiograms for different analyte concentrations. See the Supporting Information for details. (b) Points extracted at different fixed potential values in (a) and the linear curves between the concentration and the square root of time for each potential (τE).
The linearity observed in Figure 2b suggests that if the ECL output describes a maximum at a predefined potential, the time at which maximum light intensity is recorded may now serve as the analytical signal. To accomplish this, the potential for ECL generation must be adapted to lie within the potential range of the chronopotentiometric response. This was accomplished with the help of a voltage adapter.
As an initial proof of concept, the well-established ferri/ferrocyanide redox couple was investigated. The observed potential changes during a galvanostatic experiment for different concentrations of ferrocyanide are shown in Figure 3a. The concentration of ferrocyanide ions at the electrode surface changes with time, leading to a variation of potential. At the transition time, the depletion of ferrocyanide at the electrode surface occurs and a striking change in potential can be observed. The transition time can be easily observed by taking derivative of each chronopotentiogram, and a precise transition time can be extracted as the maximum of the time derivative of the potential (Figure S2).
Figure 3
Figure 3. Combination of chronopotentiometry (CP) and ECL technique for the determination of ferrocyanide. (a) Potential changes during galvanostatic pulse of 30 μA for varying concentrations of ferrocyanide in 10 mM Tris–HCl buffer solution (pH 7.4) with 100 mM NaCl as background. (b) ECL responses for different concentrations. (The inset shows the change of ECL signals from dark to light and then back to dark.) (c) Linear calibration curves of the square root of the transition time in chronopotentiometry and of the time when ECL intensity reaches the maximum as a function of concentration.
A linear calibration curve between the square root of transition time and concentration is confirmed (Figure 3c). This three-electrode cell was now combined with the ECL detection compartment containing 1 mM luminol and 5 mM hydrogen peroxide. The corresponding ECL responses for different ferrocyanide concentrations are shown in Figure 3b (the video file in the Supporting Information gives the ECL response at a 3.45 mM ferrocyanide concentration as an example). The luminol/H2O2 system tends to give a peak intensity near 0.46 V with a glassy carbon electrode, (36−38) while in the chronopotentiograms for the oxidation of ferrocyanide, the potential was found to change from 0.23 to 1.23 V.
The maximum ECL signal happens to appear near the transition time point. Without additional potential offset, these two systems match well. As the concentration increases, it takes a longer time to observe the transition of the potential and a correspondingly longer time to record peak ECL output. As seen in Figure 3c, a linear relationship was established between the square root of tp and the concentration of analyte, even though tp is strictly not the same transition time as observed in chronopotentiometry. To clearly show the differences, every transition time point in chronopotentiometry and ECL peak time point are marked in the chronopotentiograms (Figure 4a). ECL peaks were observed around the potential of 0.47 V, while the transition time points in chronopotentiometry with increasing concentration vary as a function of the chosen fixed potential. The relationships between the concentration of analyte and the square root of time for given fixed potential values were then visualized in Figure 4b. Consistent with the theoretical predictions, they exhibit a good linearity in the potential range from 0.4 to 0.8 V. Because most curves can be adequately described with the Sand equation, they should be adequate for analytical application to determine concentration. However, they should not be used for fundamental work, for example, to extract diffusion coefficients and electrode surface area, because the slopes and intercepts deviate from that using traditional transition times. The deviation of the slope between traditional chronopotentiometric data and ECL readout can be mainly attributed to the increasing transition potentials in chronopotentiometry with increasing analyte concentration; see Figure 4b. While the two calibration curves are not strictly identical, they are both linear and should allow for a successful translation of transition time measurements to an ECL light pulse, as proposed here.
Figure 4
Figure 4. (a) Traditional transition time points (noted as CP), the corresponding times when ECL intensity reaches a maximum (noted as ECL) for the determination of ferrocyanide (error bars give the potential range when the ECL intensity varies from 95% to 100% of its peak), and the times at a predefined potential value as indicated. (b) Relationships between the ferrocyanide concentration and the square root of the transition time (noted as CP), the times at which ECL gives highest intensity (noted as ECL), and the times for the indicated predefined potential values.
To demonstrate the versatility of this sensing approach, we applied it to the visual detection of carbonate alkalinity. Alkalinity is a critical parameter for evaluating water quality. Bicarbonate and carbonate are the predominant species that determine the alkalinity of environmental samples such as river water and the determination of their concentration is of high significance. Here, WE1 is an ion-selective membrane consisting of a polypropylene-supported liquid membrane doped with a hydrogen ionophore (chromoionophore I), ion exchanger (KTFPB), and lipophilic electrolyte (ETH 500). As introduced in previous work, (28) hydrogen ions expelled galvanostatically from the ion-selective membrane protonate available carbonate base in the diffusion layer via acid–base reaction. With time, the base species becomes depleted owing to the constant imposed hydrogen ion flux from the membrane, and a potential inflection occurs at a transition time τ, which is correlated to the concentration of the base in solution. As above, this potential change was converted to ECL emission signals, giving a light pulse readout for a direct carbonate alkalinity sensor. Figure 5a shows the chronopotentiograms for different concentrations of carbonate at a constant positive current of 20 μA. Transition times are then extracted from the time derivatives of the chronopotentiograms (Figure S3). However, the potential changes here from −0.1 to +0.3 V, which is beyond the potential range for the ECL emission of the luminol/H2O2 system. For this reason, the potential input for ECL was altered by using a voltage adapter. With this compact electronic device, the potential output from chronopotentiometry (U1) may be adjusted as needed and used as input for ECL emission (U2), performed with the formula
For carbonate detection, the optimum values of a and b were 2 and 0.15 V, respectively, giving light output in the required potential range.
(2)
Figure 5
Figure 5. The determination of carbonate alkalinity using an ion-selective membrane electrode. (a) Potential changes with time during galvanostatic pulse of 20 μA for different concentrations of carbonate. (b) ECL responses for different concentrations of carbonate given in millimolar units. (c) Linear calibration curves of the square root of the chronopotentiometric transition time and of the time when ECL intensity reaches its maximum as a function of carbonate concentration.
The normalized ECL intensity versus time profiles for different concentrations of carbonate are shown in Figure 5b. As the concentration of carbonate increases, the time used to observe the ECL peak intensity becomes longer. As above, the square root of this time exhibits a good linear relationship with carbonate concentration (Figure 5c). Similarly, a deviation also exists between the linear calibration curves of chronopotentiometric method and electrochemiluminescent results. Good linear relationships between the square root of time and concentration of the analyte were obtained at any chosen potential value in the range from 0.15 to 0.25 V (Figure 6), which is again in agreement with theoretical expectations. This finding is welcome and confirms the practical applicability of the method. Yet, it is not entirely expected because ECL intensity is known to depend not only on the applied potential but also on the rate of the potential change, (39,40) which tends to vary with concentration (Figure 5a).
Figure 6
Figure 6. (a) The transition times (noted as CP), the corresponding times for which ECL intensity reaches its maximum (noted as ECL; error bars indicate the potential change for which ECL intensity is within 5% of its peak), and the times for fixed potential values (0.10 V, 0.15 V, 0.20 V and 0.25 V) in chronopotentiometry. (b) The relationships between the concentration of carbonate and the square root of the transition time (noted as CP), the time at which ECL reaches its peak (noted as ECL), and the time for a fixed potential in chronopotentiometry.
The sensing mode was applied to the determination of carbonate in environmental samples from the Arve River in Geneva and commercial Evian mineral water. The total carbonate concentration (ctot) in the samples is obtained from the carbonate concentration and the pH value of the detection solution (which is adjusted to about 9.6 in measurements). The carbonate species in the sample including carbonate (CO32–), bicarbonate (HCO3–), and carbonic acid (H2CO3) can be calculated according to the following distribution equations (where δ represents the distribution fraction of carbonate speciation and Ka1 and Ka2 are the dissociation constant of H2CO3 and HCO3–, respectively).
The same sample was measured using an acidimetric titration as a reference method, using phenolphthalein and bromocresol green as indicators. The results shown in Table 1 demonstrate that our visual detection method gives good quantitative agreement with the chronopotentiometric results and the standard titration method.
(3)
(4)
(5)
Table 1. Visual Carbonate Detection in Real Samples Compared with Different Methods
| sample | pH | ctot/mMa | [CO32–]/mMb | [HCO3–]/mMb | [H2CO3]/mMb | method |
|---|---|---|---|---|---|---|
| mineral water | 7.21 | 6.69 ± 0.10 | 0.00531 ± 0.00008 | 5.82 ± 0.09 | 0.861 ± 0.013 | ISE-ECL |
| 6.67 ± 0.17 | 0.00530 ± 0.00013 | 5.81 ± 0.15 | 0.859 ± 0.022 | ISE-CP | ||
| 6.85 ± 0.05 | 0.00544 ± 0.00004 | 5.96 ± 0.04 | 0.882 ± 0.006 | titration | ||
| river water | 8.28 | 2.88 ± 0.10 | 0.0302 ± 0.0010 | 2.81 ± 0.10 | 0.0354 ± 0.0012 | ISE-ECL |
| 2.87 ± 0.14 | 0.0301 ± 0.0014 | 2.80 ± 0.14 | 0.0353 ± 0.0017 | ISE-CP | ||
| 2.78 ± 0.03 | 0.0291 ± 0.0003 | 2.72 ± 0.03 | 0.0342 ± 0.0004 | titration |
a
Experimental values.
b
Calculated from the distribution equations. ISE-ECL means the ECL detection method combined with chronopotentiometry at the ion-selective electrode. ISE-CP means the chronopotentiometric method using ion-selective electrode.
Conclusions
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We proposed here a general approach to read out chronopotentiometric sensors by a timed light pulse, using an ECL readout. For this purpose, the potential change over time in chronopotentiometric sensors was modulated to generate ECL in a separate detection compartment. The working principle of this method was first established with the help of theoretical simulations under the approximation that ECL peak signals appear at a constant potential. The feasibility of this strategy was then confirmed not only using conventional solid electrode for the determination of ferrous ions but also with ion-selective electrode for the detection of carbonate. Instead of ECL intensity, the time upon which ECL intensity reaches its maximum was measured to reflect the analyte concentration. It chiefly relies on the potential change for ECL generation, avoiding the influence from other interfering parameters on ECL intensity readouts, such as temperature, pH, and concentration change of the detection solution. A timed light pulse is more easily detectable and quantifiable by mobile cameras than the traditional recording of intensities or potentials, which is attractive for field deployable devices as well as sensing arrays.
Supporting Information
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The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.analchem.9b00787.
Theory for the simulation of chronopotentiometric responses with the finite difference method, pictures of the experimental setup, time derivatives of the chronopotentiograms for the detection of ferrocyanide and carbonate (PDF)
Example of ECL response at 3.45 mM ferro/ferricyanide concentration (AVI)
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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
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- Xiaojiang Xie - Department of Chemistry, Southern University of Science and Technology, Shenzhen 518055, China;
http://orcid.org/0000-0003-2629-8362;
- Eric Bakker - Department of Inorganic and Analytical Chemistry, University of Geneva, Quai Ernest-Ansermet 30, CH-1211 Geneva, Switzerland;http://orcid.org/0000-0001-8970-4343;
Acknowledgments
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The authors thank the National Natural Science Foundation of China (21874063) and the Swiss National Science Foundation (200021_175622) for financial support.
References
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This article references 40 other publications.
- 1Schwarz, M. A.; Hauser, P. C. Lab Chip 2001, 1, 1– 6, DOI: 10.1039/b103795cGoogle Scholar1https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD3MXns1yntbg%253D&md5=729e97b79d03c430e713bba36b57c510Recent developments in detection methods for microfabricated analytical devicesSchwarz, Maria A.; Hauser, Peter C.Lab on a Chip (2001), 1 (1), 1-6CODEN: LCAHAM; ISSN:1473-0197. (Royal Society of Chemistry)A review. Sensitive detection in microfluidic anal. devices is a challenge because of the extremely small detection vols. available. Considerable efforts were made lately to further address this aspect and to study techniques other than fluorescence. Among the newly introduced techniques are the optical methods of chemiluminescence, refraction and thermooptics, as well as the electrochem. methods of amperometry, conductimetry and potentiometry. Developments are also in progress to create miniaturized plasma-emission spectrometers and sensitive detectors for gas-chromatog. sepns.
- 2Martı́n, A.; Kim, J.; Kurniawan, J. F.; Sempionatto, J. R.; Moreto, J. R.; Tang, G.; Campbell, A. S.; Shin, A.; Lee, M. Y.; Liu, X.; Wang, J. Epidermal Microfluidic Electrochemical Detection System: Enhanced Sweat Sampling and Metabolite Detection. ACS Sensors 2017, 2 (12), 1860– 1868, DOI: 10.1021/acssensors.7b00729Google Scholar2https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2sXhvVait7nM&md5=570525c3f08138dd970692d4f9fb0c2dEpidermal Microfluidic Electrochemical Detection System: Enhanced Sweat Sampling and Metabolite DetectionMartin, Aida; Kim, Jayoung; Kurniawan, Jonas F.; Sempionatto, Juliane R.; Moreto, Jose R.; Tang, Guangda; Campbell, Alan S.; Shin, Andrew; Lee, Min Yul; Liu, Xiaofeng; Wang, JosephACS Sensors (2017), 2 (12), 1860-1868CODEN: ASCEFJ; ISSN:2379-3694. (American Chemical Society)Despite tremendous recent efforts, noninvasive sweat monitoring is still far from delivering its early anal. promise. Here, the authors describe a flexible epidermal microfluidic detection platform fabricated through hybridization of lithog. and screen-printed technologies, for efficient and fast sweat sampling and continuous, real-time electrochem. monitoring of glucose and lactate levels. This soft, skin-mounted device judiciously merges lab-on-a-chip and electrochem. detection technologies, integrated with a miniaturized flexible electronic board for real-time wireless data transmission to a mobile device. Modeling of the device design and sweat flow conditions allowed optimization of the sampling process and the microchannel layout for achieving attractive fluid dynamics and rapid filling of the detection reservoir (within 8 min from starting exercise). The wearable microdevice thus enabled efficient natural sweat pumping to the electrochem. detection chamber contg. the enzyme-modified electrode transducers. The fabricated device can be easily mounted on the epidermis without hindrance to the wearer and displays resiliency against continuous mech. deformation expected from such epidermal wear. Amperometric biosensing of lactate and glucose from the rapidly generated sweat, using the corresponding immobilized oxidase enzymes, was wirelessly monitored during cycling activity of different healthy subjects. This ability to monitor sweat glucose levels introduces new possibilities for effective diabetes management, while similar lactate monitoring paves the way for new wearable fitness applications. The new epidermal microfluidic electrochem. detection strategy represents an attractive alternative to recently reported colorimetric sweat-monitoring methods, and hence holds considerable promise for practical fitness or health monitoring applications.
- 3Liana, D. D.; Raguse, B.; Gooding, J. J.; Chow, E. Sensors 2012, 12, 11505– 11526, DOI: 10.3390/s120911505Google Scholar3https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC38XhtlSjsrvK&md5=2a1e067bad05d764c9cd9c42b14307cbRecent advances in paper-based sensorsLiana, Devi D.; Raguse, Burkhard; Gooding, J. Justin; Chow, EdithSensors (2012), 12 (), 11505-11526CODEN: SENSC9; ISSN:1424-8220. (MDPI AG)A review. Paper-based sensors are a new alternative technol. for fabricating simple, low-cost, portable and disposable anal. devices for many application areas including clin. diagnosis, food quality control and environmental monitoring. The unique properties of paper which allow passive liq. transport and compatibility with chems./biochems. are the main advantages of using paper as a sensing platform. Depending on the main goal to be achieved in paper-based sensors, the fabrication methods and the anal. techniques can be tuned to fulfill the needs of the end-user. Current paper-based sensors are focused on microfluidic delivery of soln. to the detection site whereas more advanced designs involve complex 3-D geometries based on the same microfluidic principles. Although paper-based sensors are very promising, they still suffer from certain limitations such as accuracy and sensitivity. However, it is anticipated that in the future, with advances in fabrication and anal. techniques, that there will be more new and innovative developments in paper-based sensors. These sensors could better meet the current objectives of a viable low-cost and portable device in addn. to offering high sensitivity and selectivity, and multiple analyte discrimination. This paper is a review of recent advances in paper-based sensors and covers the following topics: existing fabrication techniques, anal. methods and application areas. Finally, the present challenges and future outlooks are discussed.
- 4Kalantar-zadeh, K.; Ha, N.; Ou, J. Z.; Berean, K. J. Ingestible Sensors. ACS Sensors 2017, 2 (4), 468– 483, DOI: 10.1021/acssensors.7b00045Google Scholar4https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2sXjsFCktb0%253D&md5=054d647ccc87df1c452a3aec12c0158dIngestible SensorsKalantar-zadeh, Kourosh; Ha, Nam; Ou, Jian Zhen; Berean, Kyle J.ACS Sensors (2017), 2 (4), 468-483CODEN: ASCEFJ; ISSN:2379-3694. (American Chemical Society)A review. Ingestible sensing capsules are fast emerging as a crit. technol. that has the ability to greatly impact health, nutrition and clin. areas. These ingestible devices are noninvasive, hence very attractive for customers. With widespread access to smart phones connected to the internet, the data produced by this technol. can be readily seen and reviewed online and accessed by both users and physicians. The outputs provide invaluable information to reveal the state of gut health and disorders as well as the impact of food, medical supplements and environmental changes on the gastrointestinal tract. One unique feature of such ingestible sensors is that their passage through the gut lumen gives them access to each individual organ of the gastrointestinal tract. Therefore, ingestible sensors offer the ability to gather images, monitor luminal fluid and the contents of each gut segment including electrolytes, enzymes, metabolites, hormones and the microbial communities. As such, an incredible wealth of knowledge regarding the functionality and state of health of individuals through key gut biomarkers can be obtained. This paper presents an overview of the gut structure, and discusses current and emerging digestible technologies. The text is an effort to provide a comprehensive overview of ingestible sensing capsules, from both a body physiol. point of view as well as a technol. view and detail the potential information that they can generate.
- 5Chow, K.-F.; Mavré, F.; Crooks, J. A.; Chang, B.-Y.; Crooks, R. M. J. Am. Chem. Soc. 2009, 131, 8364– 8365, DOI: 10.1021/ja902683fGoogle Scholar5https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD1MXmsFWmtbc%253D&md5=27aeaf85c8b7d3742a249adc9f4f7dcaA Large-Scale, Wireless Electrochemical Bipolar Electrode MicroarrayChow, Kwok-Fan; Mavre, Francois; Crooks, John A.; Chang, Byoung-Yong; Crooks, Richard M.Journal of the American Chemical Society (2009), 131 (24), 8364-8365CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)The authors report a microelectrochem. array composed of 1000 individual bipolar electrodes that are controlled with just 2 driving electrodes and a simple power supply. The system is configured so that faradaic processes occurring at the cathode end of each electrode are correlated to light emission via electrogenerated chemiluminescence (ECL) at the anode end. This makes it possible to read out the state of each electrode simultaneously. The significant advance is that the electrode array is fabricated on a glass microscope slide and is operated in a simple electrochem. cell. This eliminates the need for microfluidic channels, provides a fabrication route to arbitrarily large electrode arrays, and will make it possible to place sensing chemistries onto each electrode using a robotic spotter.
- 6Liu, H.; Crooks, R. M. Anal. Chem. 2012, 84, 2528– 2532, DOI: 10.1021/ac203457hGoogle Scholar6https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC38XislWjs70%253D&md5=e87e40e8992fa3a5039f00f5da411b19Paper-Based Electrochemical Sensing Platform with Integral Battery and Electrochromic Read-OutLiu, Hong; Crooks, Richard M.Analytical Chemistry (Washington, DC, United States) (2012), 84 (5), 2528-2532CODEN: ANCHAM; ISSN:0003-2700. (American Chemical Society)The authors report a battery-powered, microelectrochem. sensing platform that reports its output using an electrochromic display. The platform is fabricated based on paper fluidics and uses a Prussian blue spot electrodeposited on an indium-doped tin oxide thin film as the electrochromic indicator. The integrated metal/air battery powers both the electrochem. sensor and the electrochromic read-out, which are in elec. contact via a paper reservoir. The sample activates the battery and the presence of analyte in the sample initiates the color change of the Prussian blue spot. The entire system is assembled on the lab. bench, without the need for cleanroom facilities. The applicability of the device to point-of-care sensing is demonstrated by qual. detection of 0.1 mM glucose and H2O2 in artificial urine samples.
- 7Liana, D. D.; Raguse, B.; Gooding, J. J.; Chow, E. ACS Appl. Mater. Interfaces 2015, 7, 19201– 19209, DOI: 10.1021/acsami.5b04941Google Scholar7https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2MXhtlOntL%252FO&md5=2910439aa59326fbdf79eb978aa385bbToward Paper-Based Sensors: Turning Electrical Signals into an Optical Readout SystemLiana, Devi D.; Raguse, Burkhard; Gooding, J. Justin; Chow, EdithACS Applied Materials & Interfaces (2015), 7 (34), 19201-19209CODEN: AAMICK; ISSN:1944-8244. (American Chemical Society)Paper-based sensors are gaining increasing attention for their potential applications in resource-limited settings and for point-of-care anal. However, chem. anal. of paper-based electronic sensors is frequently interpreted using complex software and electronic displays which compromise the advantages of using paper. The authors present two semiquant. paper-based readout systems that can visually measure a change in resistance of a resistive-based sensor. The readout systems use electrochromic Prussian blue/polyaniline as an electrochromic indicator on a resistive gold nanoparticle film that is fabricated on paper. When the readout system is integrated with a resistive sensor in an elec. circuit, and a voltage is applied, the voltage drop along the readout system varies depending on the sensor's resistance. Due to the voltage gradient formed along the gold nanoparticle film, the overlaying Prussian blue/polyaniline will change color at voltages greater than its redn. voltage (green/blue for oxidized state and transparent for reduced state). Thus, the changes in resistances of a sensor can be semiquantified through color visualization by either measuring the length of the transparent film (analog readout system) or by counting the no. of transparent segments (digital readout system). The work presented herein can potentially serve as an alternative paper-based display system for resistive sensors in instances where cost and wt. is a premium.
- 8Chow, E.; Liana, D. D.; Raguse, B.; Gooding, J. J. Aust. J. Chem. 2017, 70, 979– 984, DOI: 10.1071/CH17191Google Scholar8https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2sXhtlOksLjL&md5=51195faf58f428a76b8da78785cfa284A Potentiometric Sensor for pH Monitoring with an Integrated Electrochromic Readout on PaperChow, Edith; Liana, Devi D.; Raguse, Burkhard; Gooding, J. JustinAustralian Journal of Chemistry (2017), 70 (9), 979-984CODEN: AJCHAS; ISSN:0004-9425. (CSIRO Publishing)Paper-based potentiometric pH sensors allow multiple measurements to be recorded in a cost-effective manner but usually in combination with an external display unit. A potentiometric pH sensor is integrated with an electrochromic readout system all on paper. The potentiometric pH sensor is based on electropolymd. aniline on a conductive gold nanoparticle film working electrode. The voltage output of the sensor is amplified using an operational amplifier and generated across an electrochromic readout system. The readout system comprises four segments of electrochromic Prussian blue/polyaniline on conductive gold nanoparticle films connected by graphite resistive separators. The color of each segment is dependent on the voltage output from the potentiometric sensor and can be used to det. the pH range of a sample or whether the sample pH falls outside a crit. value. This type of integrated paper device can be used for multiple measurements and also be applied to the development of other types of potentiometric sensors.
- 9Zhang, X.; Chen, C.; Yin, J.; Han, Y.; Li, J.; Wang, E. Anal. Chem. 2015, 87, 4612– 4616, DOI: 10.1021/acs.analchem.5b01018Google Scholar9https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2MXmsVeltb4%253D&md5=a0f8a997bed0a452a8f0d6b7238a5aedPortable and Visual Electrochemical Sensor Based on the Bipolar Light Emitting Diode ElectrodeZhang, Xiaowei; Chen, Chaogui; Yin, Jianyuan; Han, Yanchao; Li, Jing; Wang, ErkangAnalytical Chemistry (Washington, DC, United States) (2015), 87 (9), 4612-4616CODEN: ANCHAM; ISSN:0003-2700. (American Chemical Society)Here the authors report a novel sensing strategy based on the closed bipolar system, in which the authors use a light emitting diode (LED) to connect a split bipolar electrode (BPE) and generate the luminescent signal in the presence of the target. With this design, the authors have constructed a BPE array for the quick and high-throughput detn. of various electroactive substances with naked eyes. Due to the ultrahigh current efficiency of the closed bipolar system, the sample concn. can be reported by the luminous intensity of the inserted LED without the expensive luminescent agent and instruments. Besides, the stability of the signal is improved because of the electroluminescent property of the LED. To demonstrate the promising applications of the bipolar LED electrode (BP-LED-E), the rapid quantification of four model targets (H2O2, ascorbic acid (AA), glucose, and blood sugar) was achieved based on different principles.
- 10Zhang, X.; Shang, C.; Gu, W.; Xia, Y.; Li, J.; Wang, E. ChemElectroChem 2016, 3, 383– 386, DOI: 10.1002/celc.201500282Google Scholar10https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2MXhtlCks7jJ&md5=5bf3ed6abd9416b6fc1a34a1ff46a982A Renewable Display Platform Based on the Bipolar Electrochromic ElectrodeZhang, Xiaowei; Shang, Changshuai; Gu, Wenlin; Xia, Yong; Li, Jing; Wang, ErkangChemElectroChem (2016), 3 (3), 383-386CODEN: CHEMRA; ISSN:2196-0216. (Wiley-VCH Verlag GmbH & Co. KGaA)We report a renewable display platform based on bipolar electrochem. that uses bipolar electrochromic electrode (BP-EC-E) arrays for high-throughput screening applications. Prussian blue (or another electrochromic material) is electrodeposited on one end of the bipolar electrode (BPE) as the signal reporter, and the other end is for the loading of catalyst. Owing to the quant. relation between the two reactions occurring at both ends of the BP-EC-E, the discoloration speeds (Prussian blue to Prussian white) are related to the amt. or the catalytic activity of the catalysts. Interestingly, the established platform can be used repeatedly, owing to the reversibility of the electrochromic reactions. With this strategy, we have achieved the fast imaging anal. of several electrocatalysts for methanol and ethanol oxidn.
- 11Zhang, X.; Zhang, L.; Zhai, Q.; Gu, W.; Li, J.; Wang, E. Anal. Chem. 2016, 88, 2543– 2547, DOI: 10.1021/acs.analchem.6b00054Google Scholar11https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC28XitFeqtr4%253D&md5=75fd66e2fd3f66fb1ee136b200f46851Self-Powered Bipolar Electrochromic Electrode Arrays for Direct Displaying ApplicationsZhang, Xiaowei; Zhang, Lingling; Zhai, Qingfeng; Gu, Wenling; Li, Jing; Wang, ErkangAnalytical Chemistry (Washington, DC, United States) (2016), 88 (5), 2543-2547CODEN: ANCHAM; ISSN:0003-2700. (American Chemical Society)Here we report a self-powered-bipolar-electrochromic-electrode (termed SP-BP-EC-E) array for the displaying applications including catalyst screening, catalytic activity measurement, and enzyme substrate quantification. By replacing the directional (or active) power source with the isotropic chem. energy to drive the bipolar electrochem. reaction, the driving background signal, bipolar electrode (BPE) background signal, uneven reporting signal and the influence of electrolysis which commonly appear in traditional bipolar systems are effectively eliminated from origin. Thus, the reporting signals from the SP-BP-EC-E arrays can be more direct and reliable to reflect the target nature. Such a SP-BP-EC-E platform exhibits a sensitive response toward the fast anal. of com. Pt black catalyst, NiPdAu hollow nanospheres, glucose dehydrogenase, and glucose. To our knowledge, this test paper-like SP-BP-EC-E is the simplest platform for high-throughput screening to date, which offers a very convenient approach for nonprofessional people to access the complicated screening and fast anal. of the electrocatalysts and biocatalyst activity and quantification of enzymic substrates.
- 12Xing, H.; Zhang, X.; Zhai, Q.; Li, J.; Wang, E. Anal. Chem. 2017, 89, 3867– 3872, DOI: 10.1021/acs.analchem.7b00246Google Scholar12https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2sXktV2mtLs%253D&md5=bae66b962cda370361694ad2e78aa574Bipolar Electrode Based Reversible Fluorescence Switch Using Prussian Blue/Au Nanoclusters Nanocomposite FilmXing, Huanhuan; Zhang, Xiaowei; Zhai, Qingfeng; Li, Jing; Wang, ErkangAnalytical Chemistry (Washington, DC, United States) (2017), 89 (7), 3867-3872CODEN: ANCHAM; ISSN:0003-2700. (American Chemical Society)A highly efficient fluorescence switch system based on a closed bipolar electrode (C-BPE) system is proposed for the first time. Here, Au nanoclusters (Au NCs) were premodified on one pole of the BPE and acted as the fluorescent donor. On the basis of the spectral overlap between the absorbance of electrochromic material Prussian blue (PB) and the fluorescence spectrum of Au NCs, fluorescence quenching ("off" state) induced by the inner filter effect was obsd. Due to the electrochem. reversible redox reaction between PB and Prussian white, switching the polarity of driving voltage could easily achieve the fluorescence recovery of the Au NCs, corresponding to the "on" state. Through the reasonable design of C-BPE and optimization of driving voltage, the on-off ratio of the integrated fluorescence switch was up to 2.7 and a good fatigue resistance, while performing 10 on-off cycles was obtained owing to the good stability of Au NCs and the reversible redox feature of PB. The introduction of BPE made the fluorescence switch more simple and controllable compared with the traditional three-electrode system, which will provide a new route for the design of the elec.-stimuli responsive fluorescence switch, esp. for the integration of the miniaturized device.
- 13Zhai, Q.; Fan, D.; Zhang, X.; Li, J.; Wang, E. NPG Asia Mater. 2017, 9, e421 DOI: 10.1038/am.2017.132Google Scholar13https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2sXhtlygurvO&md5=182db663f09d500122560e7a74b10f10Dual-electrochromic bipolar electrode-based universal platform for the construction of various visual advanced logic devicesZhai, Qingfeng; Fan, Daoqing; Zhang, Xiaowei; Li, Jing; Wang, ErkangNPG Asia Materials (2017), 9 (8), e421CODEN: NAMPCE; ISSN:1884-4057. (Nature Publishing Group)A universal logic platform based on dual-electrochromic bipolar electrodes (BPEs) for the operation of various visual advanced logic devices was designed and constructed for the first time. Two BPEs sepd. by three reaction channels filled with different reaction solns. constituted the closed BPE system and were used as the initial state. Under different input combinations, the electrochem. oxidn. of 2, 2 -azinobis (3-ethylbenzthiazoline-6-sulfonic acid) and the electrodeposition of Prussian blue occurred at different poles simultaneously and triggered rapid color changes that could be easily visualized by the naked eye. By defining the color changes at the two specific poles as outputs, visual advanced logic devices, including an encoder, a decoder, a demultiplexer, a keypad lock and a three-input concatenated logic circuit with two outputs, were successfully constructed.
- 14Zhang, X.; Jing, Y.; Zhai, Q.; Yu, Y.; Xing, H.; Li, J.; Wang, E. Anal. Chem. 2018, 90, 11780– 11784, DOI: 10.1021/acs.analchem.8b02838Google Scholar14https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1cXhslequr%252FP&md5=87d44564f8df941fe81e00192ed1308bPoint-of-Care Diagnoses: Flexible Patterning Technique for Self-Powered Wearable SensorsZhang, Xiaowei; Jing, Yin; Zhai, Qingfeng; Yu, You; Xing, Huanhuan; Li, Jing; Wang, ErkangAnalytical Chemistry (Washington, DC, United States) (2018), 90 (20), 11780-11784CODEN: ANCHAM; ISSN:0003-2700. (American Chemical Society)This paper demonstrated the fabrication of a facile, low-cost, and self-powered platform for point-of-care fitness level and athletic performance monitoring sensor using electrochem. lithog. method and its application in body fluid sensing. Flexible Au/prussian blue electrode was employed as the indicating electrode, where the color change was an indication of fitness level and athletic performance. A piece of Al foil, Au/multiwalled carbon nanotubes (MWCNTs)-glucose dehydrogenase, and Au/polymethylene blue-MWCNTs-lactic dehydrogenase electrodes were used for the detection of ionic strength, glucose, and lactic acid in sweat, resp., which allows the sensor to work without any extra instrumentation and the output signal can be recognized by the naked eyes. The advantages of these sensors are (1) self-powered; (2) readily applicable to the detection of any electroactive substance by an electrochromic material; (3) easy to fabricate via two steps of EDP; and (4) point-of-care. By assembling the energy and sensing components together through a transparent adhesive tape, the proposed self-powered wearable biosensor exhibits superior performances, indicating its broad applied prospect in the point-of-care diagnoses.
- 15Jansod, S.; Cuartero, M.; Cherubini, T.; Bakker, E. Anal. Chem. 2018, 90, 6376– 6379, DOI: 10.1021/acs.analchem.8b01585Google Scholar15https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1cXpvVejtLs%253D&md5=9b8baf19fade2f0723427e4fb7e385b7Colorimetric Readout for Potentiometric Sensors with Closed Bipolar ElectrodesJansod, Sutida; Cuartero, Maria; Cherubini, Thomas; Bakker, EricAnalytical Chemistry (Washington, DC, United States) (2018), 90 (11), 6376-6379CODEN: ANCHAM; ISSN:0003-2700. (American Chemical Society)We present here a general strategy to translate potential change at a potentiometric probe into a tunable color readout. It is achieved with a closed bipolar electrode where the ion-selective component is confined to one end of the electrode while color is generated at the opposite pole, allowing one to phys. sep. the detection compartment from the sample. An elec. potential is imposed across the bipolar electrode by soln. contact such that the potentiometric signal change at the sample side modulates the potential at the detection side. This triggers the turnover of a redox indicator in the thin detection layer until a new equil. state is established. The approach is demonstrated in sep. expts. with a chloride responsive Ag/AgCl element and a liq. membrane based calcium-selective membrane electrode, using the redox indicator ferroin in the detection compartment. The principle can be readily extended to other ion detection materials and optical readout principles.
- 16Zhai, J.; Yang, L.; Du, X.; Xie, X. Anal. Chem. 2018, 90, 12791– 12795, DOI: 10.1021/acs.analchem.8b03213Google Scholar16https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1cXhvVWitrbI&md5=38de0c14e87f4c12ba0cc63482252ce4Electrochemical-to-Optical Signal Transduction for Ion-Selective Electrodes with Light-Emitting DiodesZhai, Jingying; Yang, Liyuan; Du, Xinfeng; Xie, XiaojiangAnalytical Chemistry (Washington, DC, United States) (2018), 90 (21), 12791-12795CODEN: ANCHAM; ISSN:0003-2700. (American Chemical Society)Optical ion sensors normally have a relative narrow sensitive detection window. Here, based on multicolor light-emitting diodes (LEDs), the authors report on an electrochem.-to-optical signal transduction scheme under chronoamperometry control to convert the potentiometric response of ion-selective electrodes (ISEs) to optical output with tunable sensitivity and much wider response range. The sensing principle was demonstrated on K+, Ca2+, and Pb2+. LED light intensity was found to depend linearly on the concn. of monovalent ions. Optical signals could be captured with photomultiplier tubes or digital cameras, and a visual alarming system to monitor abnormal ion concn. was also developed from super-Nernstian electrodes.
- 17Crespo, G. A.; Mistlberger, G.; Bakker, E. J. Am. Chem. Soc. 2012, 134, 205– 207, DOI: 10.1021/ja210600kGoogle Scholar17https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3MXhs1aqu7nE&md5=94620adacd3ac2e755f0b314bdd7b102Electrogenerated Chemiluminescence for Potentiometric SensorsCrespo, Gaston A.; Mistlberger, Gunter; Bakker, EricJournal of the American Chemical Society (2012), 134 (1), 205-207CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)The authors report here on a generic approach to read out potentiometric sensors with electrogenerated chemiluminescence (ECL). In a 1st example, a potassium ion-selective electrode acts as the ref. electrode and is placed in contact with the sample soln. The working electrode of the three-electrode cell is responsible for ECL generation and placed in a detection soln. contg. tris(2,2'-bipyridyl)ruthenium(II) [Ru(bpy)32+] and the coreactant 2-(dibutylamino)ethanol (DBAE), phys. sepd. from the sample by a bridge. Changes in the sample potassium concn. directly modulate the potential at the working electrode, and hence the ECL output, when a const.-potential pulse is applied between the two electrodes. A linear response of the ECL intensity to the logarithmic potassium concn. between 10 μm and 10 mM was found.
- 18Knight, A. W. TrAC, Trends Anal. Chem. 1999, 18, 47– 62, DOI: 10.1016/S0165-9936(98)00086-7Google Scholar18https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaK1MXltFShsw%253D%253D&md5=ce4ddc6ca31c554847b2530f93e3abc0A review of recent trends in analytical applications of electrogenerated chemiluminescenceKnight, Andrew W.TrAC, Trends in Analytical Chemistry (1999), 18 (1), 47-62CODEN: TTAEDJ; ISSN:0165-9936. (Elsevier Science B.V.)A review with 79 refs. The development of anal. applications involving the electrochem. generation of chemiluminescence (ECL) in the last 5 yr is reviewed. The mechanisms of common ECL reactions are summarized, and the potential advantages of ECL over conventional chemiluminescence are discussed. The current limitations of the technique are considered along with how they are being addressed. Finally some pointers as to likely directions of future research are given.
- 19Fahnrich, K. A.; Pravda, M.; Guilbault, G. G. Talanta 2001, 54, 531– 559, DOI: 10.1016/S0039-9140(01)00312-5Google Scholar19https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD3MXktVGnur8%253D&md5=cdfc44470f063a3f257e77042d025261Recent applications of electrogenerated chemiluminescence in chemical analysisFahnrich, K. A.; Pravda, M.; Guilbault, G. G.Talanta (2001), 54 (4), 531-559CODEN: TLNTA2; ISSN:0039-9140. (Elsevier Science B.V.)A review with 285 refs. Anal. applications of electrogenerated chemiluminescence (ECL) are reviewed with emphasis on the years 1997-2000. Recent developments are described for the ECL of orgs., metal complexes and clusters, cathodic ECL on oxide covered electrodes, ECL based immunosensors, DNA-probe assays and enzymic biosensors. Mechanisms are given for polyarom. hydrocarbons, luminol/hydrogen peroxide, some cathodic ECL reactions and ruthenium complexes with and without co-reactants. New developments and improvements of techniques and instrumentation and their application to analytes are described. The application of ECL for visualization of electrochem. processes and imaging of surfaces is mentioned.
- 20Richter, M. M. Chem. Rev. 2004, 104, 3003– 3036, DOI: 10.1021/cr020373dGoogle Scholar20https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD2cXitlWmsLw%253D&md5=b30fc3521d1df4e0b0760d5fb3fbb0d3Electrochemiluminescence (ECL)Richter, Mark M.Chemical Reviews (Washington, DC, United States) (2004), 104 (6), 3003-3036CODEN: CHREAY; ISSN:0009-2665. (American Chemical Society)A review. Electrochemiluminescence ( ECL) involves the generation of species at electrode surfaces that then undergo electron-transfer reactions to form excited states that emit light. By employing ECL-active species as labels on biol. mols., ECL has found application in immunoassays and DNA analyses. Com. systems have been developed that use ECL to detect many clin. important analytes (e.g., α-fetoprotein, digoxin, protein and steroidal hormones, and various antibodies) with high sensitivity and selectivity.
- 21Marquette, C. A.; Blum, L. J. Anal. Bioanal. Chem. 2008, 390, 155– 168, DOI: 10.1007/s00216-007-1631-2Google Scholar21https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD2sXhsVKgur%252FN&md5=c57591aa5e9559d146f72b2d9b5d7a1aElectro-chemiluminescent biosensingMarquette, Christophe A.; Blum, Loiec J.Analytical and Bioanalytical Chemistry (2008), 390 (1), 155-168CODEN: ABCNBP; ISSN:1618-2642. (Springer)A review. The present review draws a general picture of the bioanal. applications of electro-chemiluminescent reactions (ECL). Only the two main ECL reactions-i.e. the luminol-based and Ru(bpy)32+-based reactions-are considered for application in the fields of enzyme biosensors, immunochem. biosensors, DNA biosensors, and biochips. The mechanism, principle, and exptl. conditions of these two reactions are described. Then, for each category of anal. tools, exptl. set-ups and performances are presented and discussed.
- 22Miao, W. Chem. Rev. 2008, 108, 2506– 2553, DOI: 10.1021/cr068083aGoogle Scholar22https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD1cXmtlCqurY%253D&md5=53805dc698b191a4fc2ebef17aeefe9bElectrogenerated Chemiluminescence and Its Biorelated ApplicationsMiao, WujianChemical Reviews (Washington, DC, United States) (2008), 108 (7), 2506-2553CODEN: CHREAY; ISSN:0009-2665. (American Chemical Society)A review. The rapid development of electrogenerated chemiluminescence (ECL) in both fundamentals and applications over the past several years has clearly demonstrated that ECL is a powerful tool for ultrasensitive biomol. detection and quantification. High-throughput, miniaturized biosensors based on ECL technol. capable of multiplexing detection with high sensitivity, low detection limit, and good selectivity and stability will continue to attract the interest of the research community. With further understanding of ECL mechanisms, new highly efficient, tunable ECL systems, both emitters and coreactants, will be developed. Approaches based on ECL enhancement as well as quenching may play an important role in designing new methodologies for sensitive biomol. recognition. Thermodn. and kinetic studies of biomol. interactions using ECL are expected to be further expanded. The combination of ECL with other techniques could lead to the development of new instruments or provide valuable insights into mol. structures and intracellular components of biorelated species. Ultimately, detection of single biomols. will be realized.
- 23Liu, Z.; Qi, W.; Xu, G. Chem. Soc. Rev. 2015, 44, 3117– 3142, DOI: 10.1039/C5CS00086FGoogle Scholar23https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2MXltVaiurc%253D&md5=957d27a9a9fc4e7616d209a15de5d255Recent advances in electrochemiluminescenceLiu, Zhongyuan; Qi, Wenjing; Xu, GuobaoChemical Society Reviews (2015), 44 (10), 3117-3142CODEN: CSRVBR; ISSN:0306-0012. (Royal Society of Chemistry)The great success of electrochemiluminescence (ECL) for in vitro diagnosis (IVD) and its promising potential in light-emitting devices greatly promote recent ECL studies. More than 45% of ECL articles were published after 2010, and the first international meeting on ECL was held in Italy in 2014. This crit. review discusses recent vibrant developments in ECL, and highlights novel ECL phenomena, such as wireless ECL devices, bipolar electrode-based ECL, light-emitting electrochem. swimmers, upconversion ECL, ECL resonance energy transfer, thermoresponsive ECL, ECL using shape-controlled nanocrystals, and ECL as an ion-selective electrode photonic reporter, a paper-based microchip, and a self-powered microfluidic ECL platform. We also comment on the latest progress in bioassays, light-emitting devices and, the computational approach for the ECL mechanism study. Finally, perspectives and key challenges in the near future are addressed (198 refs.).
- 24Gao, W.; Saqib, M.; Qi, L.; Zhang, W.; Xu, G. Curr. Opin. Electrochem. 2017, 3, 4– 10, DOI: 10.1016/j.coelec.2017.03.003Google Scholar24https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1cXhtVGgsLvK&md5=1e24de4daaab7e9eb15f7b7b0266d262Recent advances in electrochemiluminescence devices for point-of-care testingGao, Wenyue; Saqib, Muhammad; Qi, Liming; Zhang, Wei; Xu, GuobaoCurrent Opinion in Electrochemistry (2017), 3 (1), 4-10CODEN: COEUCY; ISSN:2451-9111. (Elsevier B.V.)A Review. A dynamic progress of methodologies has increased demand for high performance detection technologies for point-of-care testing (POCT). Electrochemiluminescence (ECL) is now established as an important, highly sensitive detection strategy for the development of POCT devices. In this short review, we summarize the recent advances of portable ECL devices, such as portable power sources, bipolar ECL devices, wireless ECL devices, ECL detectors, and microfluidic chips. Moreover, we address the remaining challenges and future perspectives to integrate ECL sensing devices into point-of-care solns.
- 25Fähnrich, K. A.; Pravda, M.; Guilbault, G. G. Talanta 2001, 54, 531– 559, DOI: 10.1016/S0039-9140(01)00312-5Google Scholar25https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD3MXktVGnur8%253D&md5=cdfc44470f063a3f257e77042d025261Recent applications of electrogenerated chemiluminescence in chemical analysisFahnrich, K. A.; Pravda, M.; Guilbault, G. G.Talanta (2001), 54 (4), 531-559CODEN: TLNTA2; ISSN:0039-9140. (Elsevier Science B.V.)A review with 285 refs. Anal. applications of electrogenerated chemiluminescence (ECL) are reviewed with emphasis on the years 1997-2000. Recent developments are described for the ECL of orgs., metal complexes and clusters, cathodic ECL on oxide covered electrodes, ECL based immunosensors, DNA-probe assays and enzymic biosensors. Mechanisms are given for polyarom. hydrocarbons, luminol/hydrogen peroxide, some cathodic ECL reactions and ruthenium complexes with and without co-reactants. New developments and improvements of techniques and instrumentation and their application to analytes are described. The application of ECL for visualization of electrochem. processes and imaging of surfaces is mentioned.
- 26Gao, W.; Muzyka, K.; Ma, X.; Lou, B.; Xu, G. Chem. Sci. 2018, 9, 3911– 3916, DOI: 10.1039/C8SC00410BGoogle Scholar26https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1cXltVyls7s%253D&md5=bb8489eb30266c80343b2fa6592161d1A single-electrode electrochemical system for multiplex electrochemiluminescence analysis based on a resistance induced potential differenceGao, Wenyue; Muzyka, Kateryna; Ma, Xiangui; Lou, Baohua; Xu, GuobaoChemical Science (2018), 9 (16), 3911-3916CODEN: CSHCCN; ISSN:2041-6520. (Royal Society of Chemistry)Developing low-cost and simple electrochem. systems is becoming increasingly important but still challenged for multiplex expts. Here we report a single-electrode electrochem. system (SEES) using only one electrode not only for a single expt. but also for multiplex expts. based on a resistance induced p.d. SEESs for a single expt. and multiplex expts. are fabricated by attaching a self-adhesive label with a hole and multiple holes onto an ITO electrode, resp. This enables multiplex electrochemiluminescence anal. with high sensitivity at a very low safe voltage using a smartphone as a detector. For the multiplex anal., the SEES using a single electrode is much simpler, cheaper and more user-friendly than conventional electrochem. systems and bipolar electrochem. systems using electrode arrays. Moreover, SEESs are free from the electrochemiluminescent background problem from driving electrodes in bipolar electrochem. systems. Since numerous electrodes and cover materials can be used to fabricate SEESs readily and electrochem. is being extensively used, SEESs are very promising for broad applications, such as drug screening and high throughput anal.
- 27Hu, L.; Xu, G. Chem. Soc. Rev. 2010, 39, 3275– 3304, DOI: 10.1039/b923679cGoogle Scholar27https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3cXptFygs7o%253D&md5=f6d5d09802f9a4fcefbc98ad30a8a944Applications and trends in electrochemiluminescenceHu, Lianzhe; Xu, GuobaoChemical Society Reviews (2010), 39 (8), 3275-3304CODEN: CSRVBR; ISSN:0306-0012. (Royal Society of Chemistry)A review. Electrochemiluminescence (ECL) is chemiluminescence triggered by electrochem. techniques. More than 150 ECL assays with remarkably high sensitivity and extremely wide dynamic range are currently available, and accounts for hundreds of millions of dollars in sales per yr. The recent development of ECL is particularly rapid. After a brief introduction to ECL, this crit. review presents the active and/or emerging areas of ECL research as well as new applications and phenomena of ECL, such as light-emitting electrochem. cell, wireless electrochem. microarray using ECL as photonic reporter, high throughput anal., aptasensors, immunoassays and DNA anal., ECL of nanoclusters and carbon nanomaterials, ECL imaging techniques, scanning ECL microscopy, colorimetric ECL sensor, surface plasmon-coupled ECL, electrostatic chemiluminescence, soliton-like ECL waves, ECL investigation of mol. interaction, and single mol. detection. Finally, some perspectives on this rapidly developing field are discussed (322 refs.).
- 28Afshar, M. G.; Crespo, G. A.; Xie, X.; Bakker, E. Anal. Chem. 2014, 86, 6461– 6470, DOI: 10.1021/ac500968cGoogle Scholar28https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2cXos1Wrsbw%253D&md5=19d39ea2b127e5d99def536db7dded24Direct Alkalinity Detection with Ion-Selective ChronopotentiometryAfshar, Majid Ghahraman; Crespo, Gaston A.; Xie, Xiaojiang; Bakker, EricAnalytical Chemistry (Washington, DC, United States) (2014), 86 (13), 6461-6470CODEN: ANCHAM; ISSN:0003-2700. (American Chemical Society)The authors explore the possibility to directly measure pH and alky. in the sample with the same sensor by imposing an outward flux of hydrogen ions from an ion-selective membrane to the sample soln. by an applied current. The membrane consists of a polypropylene-supported liq. membrane doped with a hydrogen ionophore (chromoionophore I), ion exchanger (KTFBP), and lipophilic electrolyte (ETH 500). While the sample pH is measured at zero current, alky. is assessed by chronopotentiometry at anodic current. Hydrogen ions expelled from the membrane undergo acid-base soln. chem. and protonate available base in the diffusion layer. With time, base species start to be depleted owing to the const. imposed hydrogen ion flux from the membrane, and a local pH change occurs at a transition time. This pH change (potential readout) is correlated to the concn. of the base in soln. As in traditional chronopotentiometry, the obsd. square root of transition time (τ) is linear in the concn. range of 0.1 mM to 1 mM, using the bases tris(hydroxymethyl)aminomethane, ammonia, carbonate, hydroxide, hydrogen phosphate, and borate. Numerical simulations were used to predict the concn. profiles and the chronopotentiograms, allowing the discussion of possible limitations of the proposed method and its comparison with volumetric titrns. of alky. Finally, the P-alky. level is measured in a river sample to demonstrate the anal. usefulness of the proposed method. As a result of these preliminary results, probably this approach becomes useful for the in situ detn. of P-alky. in a range of matrixes.
- 29Jarolimova, Z.; Crespo, G. A.; Xie, X.; Afshar, M. G.; Pawlak, M.; Bakker, E. Anal. Chem. 2014, 86, 6307– 6314, DOI: 10.1021/ac5004163Google Scholar29https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2cXosl2qt7c%253D&md5=87b751d0c6429440e1fc6eddc63b868aChronopotentiometric Carbonate Detection with All-Solid-State Ionophore-Based ElectrodesJarolimova, Zdenka; Crespo, Gaston A.; Xie, Xiaojiang; Ghahraman Afshar, Majid; Pawlak, Marcin; Bakker, EricAnalytical Chemistry (Washington, DC, United States) (2014), 86 (13), 6307-6314CODEN: ANCHAM; ISSN:0003-2700. (American Chemical Society)The authors present here for the 1st time an all-solid-state chronopotentiometric ion sensing system based on selective ionophores, specifically for the carbonate anion. A chronopotentiometric readout is attractive because it may allow one to obtain complementary information on the sample speciation compared to zero-current potentiometry and detect the sum of labile carbonate species instead of only ion activity. Ferrocene covalently attached to the PVC polymeric chain acts as an ion-to-electron transducer and provides the driving force to initiate the sensing process at the membrane-sample interface. The incorporation of a selective ionophore for carbonate allows one to det. this anion in a background electrolyte. Various inner electrolyte and all-solid-state-membrane configurations are explored, and localized carbonate depletion is only obsd. for systems that do not contain ion-exchanger additives. The square root of the transition times extd. from the inflection point of the chronopotentiograms as a function of carbonate specie concn. follows a linear relation. The obsd. linear range is 0.03-0.35 mM in a pH range of 9.50-10.05. By applying the Sand equation, the diffusion coeff. of carbonate is calcd. as (9.03 ± 0.91) 10-6 cm2 s-1, which corresponds to the established value. The reproducibility of assessed carbonate is better than 1%. Addnl., carbonate is monitored during titrimetric anal. as a precursor to an in situ environmental detn. Based on these results, Fc-PVC membranes doped with ionophores may form the basis of a new family of passive/active all-solid-state ion selective electrodes interrogated by a current pulse.
- 30Delahay, P.; Mattax, C.; Berzins, T. Theory of Voltammetry at Constant Current. IV. Electron Transfer Followed by Chemical Reaction. J. Amer. Chem. Soc. 1954, 76, 5319– 5324, DOI: 10.1021/ja01650a017Google Scholar30https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaG2MXhtFWitw%253D%253D&md5=a546bb6357e732467847658149bf6d60Theory of voltammetry at constant current. IV. Electron transfer followed by chemical reactionDelahay, Paul; Mattax, Calvin C.; Berzins, TalivaldisJournal of the American Chemical Society (1954), 76 (), 5319-24CODEN: JACSAT; ISSN:0002-7863.cf. C.A. 48, 5689e. A theoretical treatment is given of electron-transfer processes followed by chem. reaction in voltammetry at const. current. The 4 processes treated are: (1) O + ne = R .dblharw. Z; (2) O + ne = R, R + Z .dblharw. O; (3) M + pX- = MXp(p-n)- + ne; (4) M + pX- = MXp + pe; where O is a reducible substance, R its product of reduction, and Z, a substance not reduced or oxidized at the potentials at which O is reduced. For processes represented by 1 and 2, boundary value problems are set up, the boundary conditions detd., and the problems solved. For 1, the equation for the potential is given in terms of a transition time, τ, which is the time at which the concn. of O is zero at the electrode surface. It is shown that potential-time curves are shifted toward more anodic potentials as the reaction R to Z becomes more rapid. The influence of c.d. is discussed. For 2, the transition times, τc, in the presence of, and τd, in the absence of a catalytic effect are introduced. The ratio, (τc/τd)1/2, is plotted against (kfCZ0 τc)1/2, where kf is a 1st-order rate const. for the forward reaction in 2 and CZ0 is the concn. of Z which is assumed to be const. This can be applied to the detn. of kf if τc and τd are known. The influence of c.d. is discussed, and conclusions are shown to agree with the exptl. results obtained from the catalytic reduction of Ti(IV) in the presence of hydroxylamine. The anodic oxidation of a metal with the formation of a complex by 3 is treated by deriving an expression for the concn. of M+ at the electrode surface in terms of τ and substituting this in the Nernst equation. This is then used to det. the potential for the anodic oxidation of Ag in KCN, and the exptl. and theoretical values are shown to agree. The treatment given is valid only for the equil. formation of one complex. The anodic oxidation of a metal with the formation of a film of insol. substance on the electrode by 4 is given a treatment similar to 3. The resulting equation is used to det. the soly. products of AgCl and AgBr from expts. on the anodic oxidation of Ag in chloride and bromide solns., resp. The values obtained are higher than those given in the literature, primarily because the solid particles formed in the anodic process are very small and, therefore, more sol. The treatment is simplified by assuming films are too thin to offer any barrier to diffusion to and from the electrode. Transition times are derived for spherical and linear diffusion with partial mass transfer by migration in an elec. field of const. intensity.
- 31Gemene, K. L.; Bakker, E. Anal. Chem. 2008, 80, 3743– 3750, DOI: 10.1021/ac701983xGoogle Scholar31https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD1cXjvFejt70%253D&md5=b1c01b6bd66a0602d2b9f79db306657aDirect Sensing of Total Acidity by Chronopotentiometric Flash Titrations at Polymer Membrane Ion-Selective ElectrodesGemene, Kebede L.; Bakker, EricAnalytical Chemistry (Washington, DC, United States) (2008), 80 (10), 3743-3750CODEN: ANCHAM; ISSN:0003-2700. (American Chemical Society)Polymer membrane ion-selective electrodes contg. lipophilic ionophores are traditionally interrogated by zero current potentiometry, which, ideally, gives information on the sample activity of ionic species. A discrete cathodic current pulse across an H+-selective polymeric membrane doped with the ionophore ETH 5294 may be used for the chronopotentiometric detection of pH in well-buffered samples. However, a redn. in the buffer capacity leads to large deviations from the expected Nernstian response slope. This is explained by the local depletion of hydrogen ions at the sample-membrane interface as a result of the galvanostatically imposed ion flux in direction of the membrane. This depletion is a function of the total acidity of the sample and can be directly monitored chronopotentiometrically in a flash titrn. expt. The subsequent application of a baseline potential pulse reverses the extn. process of the current pulse, allowing one to interrogate the sample with minimal perturbation. In one protocol, total acidity is proportional to the magnitude of applied current at the flash titrn. end point. More conveniently, the square root of the flash titrn. end point time obsd. at a fixed applied current is a linear function of the total acid concn. Probably it is possible to perform rapid localized pH titrns. at ion-selective electrodes without the need for volumetric titrimetry. The technique is explored here for acetic acid, MES and citric acid with promising results. Polymeric membrane electrodes based on poly(vinyl chloride) plasticized with o-nitrophenyl octyl ether in a 1:2 mass ratio may be used for the detection of acids of up to ca. 1 MM concn., with flash titrn. times on the order of a few seconds. Possible limitations of the technique are discussed, including variations of the acid diffusion coeffs. and influence of elec. migration.
- 32Jarolimova, Z.; Crespo, G. A.; Afshar, M. G.; Pawlak, M.; Bakker, E. J. Electroanal. Chem. 2013, 709, 118– 125, DOI: 10.1016/j.jelechem.2013.10.011Google Scholar32https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3sXhvV2qt7zE&md5=b335bc5e2d9c66220cfb1b6301d78957All solid state chronopotentiometric ion-selective electrodes based on ferrocene functionalized PVCJarolimova, Zdenka; Crespo, Gaston A.; Afshar, Majid Ghahraman; Pawlak, Marcin; Bakker, EricJournal of Electroanalytical Chemistry (2013), 709 (), 118-125CODEN: JECHES; ISSN:1873-2569. (Elsevier B.V.)An all solid contact ion-selective electrode based on poly(vinyl chloride) covalently modified with ferrocene moieties allows one to operate the membrane in a chronopotentiometric sensing mode. The membrane is considered as initially non-perm-selective towards anions, and an applied anodic current provokes a defined anion flux in direction of the membrane. With this protocol, a variety of anions can be depleted at the membrane surface. Since this model system does not yet contain an ionophore, their order of preference follows the expected Hofmeister selectivity sequence. The all solid-state configuration tolerates an imposed c.d. of 1.4 μA mm-2, which translates into an upper detection limit of ∼1.2 mM. Higher current densities of up to 31.2 μA mm-2 are possible with addn. of freely dissolved alkyl ferrocene deriv. for an expected upper detection limit of 17.0 mM. Numerical simulations were performed to establish the fundamental basis of the mechanism that takes place in this all solid-state membrane electrode. The oxidn. of bound Fc and the ion-transfer process are considered in the simulation. In view of developing an anal. sensor, different anions are tested. A linear range of two orders of magnitude from 0.01 to 1 mM is found. The membranes are evaluated over several days, displaying practically the same slopes and intercepts, with a relative std. deviation of <2%. Electrochem. limitations of free Fc and bound Fc are crit. evaluated. This approach should allow one to develop a new family of solid-state chronopotentiometric ion sensors that require relatively high current densities.
- 33Sand, H. J. S. Philos. Mag. 1901, 1, 45– 79, DOI: 10.1080/14786440109462590Google Scholar33https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaD28XptlI%253D&md5=66930f7b3424ff19590b664cf5f06c25On the concentration at the electrodes in a solution, with special reference to the liberation of hydrogen by electrolysis of a mixture of copper sulphate and sulphuric acidSand, Henry J. S.Philosophical Magazine (1798-1977) (1901), 1 (1), 45-79CODEN: PHMAA4; ISSN:0031-8086.Since the electrolysis of mixtures first attracted the attention of scientists, three distinct views have been held about the processes which take place at the electrodes. An equation has been derived and proved for calculating the concentration at the electrode of a solution of a single salt from which the metal is being deposited. In the case of mixture, it is possible to arrive at limits for the concentration. Convection currents play a key role in determining the ratio of the two constituents given off at the electrode of an acid copper-sulphate solution.
- 34Bard, A. J. Anal. Chem. 1961, 33, 11– 15, DOI: 10.1021/ac60169a002Google Scholar34https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaF3MXjs12jtA%253D%253D&md5=1f7cbee495306682e6a9ff6afa472b8dEffect of electrode configuration and transition time in solid electrode chronopotentiometryBard, Allen J.(1961), 33 (), 11-15CODEN: ANCHAM; ISSN:0003-2700.To det. the optimum electrode conditions and transition time range for chronopotentiometric analysis, the transition time const., i0γ1/2/C0, was measured for the redn. of Ag(I) and Pb(II), and the oxidn. of I- and hydroquinone, over a transition time range of 0.001-300 sec. The transition time const. increased at long transition times owing to spherical contributions to diffusion and natural convection. An increase at short transition times was ascribed to charging of the double layer, electrode oxidn., and roughness of the electrode. By employing a horizontal electrode with a glass mantle, oriented so that d. gradients were not produced, the transition time const. was maintained const. to ±0.2% with transition times of 7-145 sec.
- 35Yuan, D.; Cuartero, M.; Crespo, G. A.; Bakker, E. Anal. Chem. 2017, 89, 586– 594, DOI: 10.1021/acs.analchem.6b03354Google Scholar35https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC28XhvFKns7rO&md5=736b18423f8b6620d591990a719be73eVoltammetric Thin-Layer Ionophore-Based Films: Part 1. Experimental Evidence and Numerical SimulationsYuan, Dajing; Cuartero, Maria; Crespo, Gaston A.; Bakker, EricAnalytical Chemistry (Washington, DC, United States) (2017), 89 (1), 586-594CODEN: ANCHAM; ISSN:0003-2700. (American Chemical Society)Voltammetric thin layer (∼200 nm) ionophore-based polymeric films of defined ion-exchange capacity have recently emerged as a promising approach to acquire multi-ion information about the sample, in analogy to performing multiple potentiometric measurements with individual membranes. They behave under two different regimes that are dependent on the ion concn. A thin layer control (no mass transport limitation of the polymer film or soln.) is identified for ion concns. of >10 μM, in which case the peak potential serves as the readout signal, in analogy to a potentiometric sensor. However, ion transfer at lower concns. is chiefly controlled by diffusional mass transport from the soln. to the sensing film, resulting in an increase of peak current with ion concn. This concn. range is suitable for electrochem. ion transfer stripping anal. Here, the transition between the two mentioned scenarios is explored exptl., using a highly Ag-selective membrane as a proof-of-concept under different conditions (variation of ion concn. in the sample from 0.1 μM to 1 mM, scan rate from 25 mV s-1 to 200 mV s-1, and angular frequency from 100 rpm to 6400 rpm). Apart from exptl. evidence, a numerical simulation is developed that considers an idealized conducting polymer behavior and permits one to predict exptl. behavior under diffusion or thin-layer control.
- 36Liu, X.; Qi, W.; Gao, W.; Liu, Z.; Zhang, W.; Gao, Y.; Xu, G. Chem. Commun. 2014, 50, 14662– 14665, DOI: 10.1039/C4CC06633BGoogle Scholar36https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2cXhslCis7bL&md5=9eff7c0ca7299c6d34f7d3f299066b19Remarkable increase in luminol electrochemiluminescence by sequential electroreduction and electrooxidationLiu, Xiaoyun; Qi, Wenjing; Gao, Wenyue; Liu, Zhongyuan; Zhang, Wei; Gao, Ying; Xu, GuobaoChemical Communications (Cambridge, United Kingdom) (2014), 50 (93), 14662-14665CODEN: CHCOFS; ISSN:1359-7345. (Royal Society of Chemistry)Luminol electrochemiluminescence is dramatically increased by about five hundred times by taking full advantage of both electrochem. redn. and electrochem. oxidn. using simple linear sweep voltammetry, leading to sensitive detection.
- 37Sakura, S. Anal. Chim. Acta 1992, 262, 49– 57, DOI: 10.1016/0003-2670(92)80007-TGoogle Scholar37https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaK38Xks1Wrtr8%253D&md5=ce777aa3fcae9fb6416f90260a2906c5Electrochemiluminescence of hydrogen peroxide-luminol at a carbon electrodeSakura, SachikoAnalytica Chimica Acta (1992), 262 (1), 49-57CODEN: ACACAM; ISSN:0003-2670.Electrochemiluminescence (ECL) was used to detect hydrogen peroxide in aq. solns. in the presence of electrolytically oxidized luminol. Using a glassy carbon electrode, the ECL mechanism could be selected by the applied potential. Luminol is oxidized to the excited intermediate (diazasemiquinone radical or diazaquinone) at around 0.5 V vs. SCE in pH 7.4 aq. soln.; above 1.0 V, hydrogen peroxide is oxidized to superoxide and the amino group of luminol is also oxidized. Therefore, the ECL mechanism is different depending on whether the applied potential is between 0.5 and 1.0 V or more pos. At the higher potentials, complex fluorophores are involved. On the other hand, at the lower potentials the fluorophore is simple and the ECL spectrum shows a simple max. emission peak. The quality of the data obtained at 0.7 V is better than that at 1.2 V. The detection limit of hydrogen peroxide is 66 pmol with a relative std. deviation of 1.1% (n = 5) at a signal-to-noise ratio of 6.
- 38Vitt, J. E.; Johnson, D. C.; Engstrom, R. C. J. Electrochem. Soc. 1991, 138, 1637– 1643, DOI: 10.1149/1.2085846Google Scholar38https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaK3MXkvVSkurg%253D&md5=f135d00166b037a5e34e77228963c37aThe effect of electrode material on the electrogenerated chemiluminescence of luminolVitt, Joseph E.; Johnson, Dennis C.; Engstrom, Royce C.Journal of the Electrochemical Society (1991), 138 (6), 1637-43CODEN: JESOAN; ISSN:0013-4651.The oxidn. of luminol and its concomitant electrogenerated chemiluminescence (ECL) were studied at several electrode materials by voltammetry and chronoamperometry. The ECL intensity (IECL) was inversely related to the activity of the electrodes. The lowest IECL was measured when luminol was oxidized to 3-aminophthalate (n ≃ 4 equiv mol-1) at a nearly mass-transport limited rate at glassy carbon. The ECL kinetics were studied and the order of the reaction with respect to luminol was 3/2 at concns. to ca. 1mM when O2 was the coreactant. In the presence of H2O2, the ECL reaction was first order with respect to luminol. A reaction mechanism is proposed that is consistent with the kinetic data and the inverse relationship between electrode activity and IECL. The implications of these results are discussed with respect to imaging the spatial distribution of c.d. at electrode surfaces, including that of PbO2 films activated by adsorbed Bi(V). A value of 6.6 × 10-6 cm2s-1 was detd. for the diffusion coeff. of luminol in 0.1M NaOH.
- 39Choi, J.-P.; Bard, A. J. Anal. Chim. Acta 2005, 541, 141– 148, DOI: 10.1016/j.aca.2004.11.075Google ScholarThere is no corresponding record for this reference.
- 40Cui, H.; Zhang, Z. F.; Zou, G. Z.; Lin, X. Q. J. Electroanal. Chem. 2004, 566, 305– 313, DOI: 10.1016/j.jelechem.2003.11.041Google Scholar40https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD2cXjtFGjsLs%253D&md5=9d42970ec55b8ef6249e24579b41a13dPotential-dependent electrochemiluminescence of luminol in alkaline solution at a gold electrodeCui, Hua; Zhang, Zhi-Feng; Zou, Gui-Zheng; Lin, Xiang-QinJournal of Electroanalytical Chemistry (2004), 566 (2), 305-313CODEN: JECHES ISSN:. (Elsevier)The behavior of luminol electrochemiluminescence (ECL) at a polycryst. gold electrode was studied under conventional cyclic voltammetric (CV) conditions. At least six ECL peaks were obsd. at 0.28 (ECL-1), 0.56 (ECL-2), 0.95 (ECL-3), 1.37 (ECL-4), -0.43 (ECL-5) and 1.00 (ECL-6, a broad wave after the reverse scan from +1.66) V (vs. SCE), resp., on the curve of ECL intensity vs. the potential. These ECL peaks were found to depend on the presence of O2 and N2, the pH of the soln., KCl concn., scan rate, and potential scan ranges. The emitter of all ECL peaks was identified as 3-aminophthalate by analyzing the CL spectra. It is believed that ECL-1 at 0.28 V was correlated to luminol radicals produced by the electro-oxidn. of luminol anion and ECL-2 at 0.56 V was caused by the reaction of luminol radical anions with gold oxide formed on the electrode surface. ECL-1 and ECL-2 could be strongly enhanced by O2 and O2√-. ECL-3 at 0.95 V was likely to be due to the reaction of luminol radical anions with O2 oxidized by OH-. ECL-4 at 1.37 V suggested that OH- was electro-oxidized to HO2- at this potential and then to O2√-, which reacted with luminol radical anions to produce light emission. ECL-5 at -0.43 V seems to be due to the reaction of luminol with ClO- electrogenerated at higher pos. potential and HO2- electrogenerated at neg. potential. ECL-6 was attributed to the reaction of luminol radical anions and ClO- electrogenerated at higher pos. potential. The results indicated that luminol ECL can be readily initiated by various oxygen-contg. species electrogenerated at different potentials, leading to multi-channel light emissions. Furthermore, the present work also reveals that ECL-2 is a predominant ECL reaction route at a gold electrode with higher potential scan rates under CV conditions.
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Analytical Chemistry
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Abstract
Figure 1
Figure 1. Schematic illustration of the proposed sensing approach converting chronopotentiometric signals in a sample compartment to a timed ECL pulse that can be captured by a camera. A glassy carbon electrode or an ion-selective electrode was used as the working electrode (WE1), platinum counter electrode (CE1), and double-junction Ag/AgCl/3 M KCl/1 M LiOAc reference electrode (RE) were used in chronopotentiometric measurements. In the ECL detection compartment, a glassy carbon electrode was used as the working electrode (WE2) to generate light, and a platinum electrode was used as counter electrode (CE2) to form a closed circuit.
Figure 2
Figure 2. (a) Simulated chronopotentiograms for different analyte concentrations. See the Supporting Information for details. (b) Points extracted at different fixed potential values in (a) and the linear curves between the concentration and the square root of time for each potential (τE).
Figure 3
Figure 3. Combination of chronopotentiometry (CP) and ECL technique for the determination of ferrocyanide. (a) Potential changes during galvanostatic pulse of 30 μA for varying concentrations of ferrocyanide in 10 mM Tris–HCl buffer solution (pH 7.4) with 100 mM NaCl as background. (b) ECL responses for different concentrations. (The inset shows the change of ECL signals from dark to light and then back to dark.) (c) Linear calibration curves of the square root of the transition time in chronopotentiometry and of the time when ECL intensity reaches the maximum as a function of concentration.
Figure 4
Figure 4. (a) Traditional transition time points (noted as CP), the corresponding times when ECL intensity reaches a maximum (noted as ECL) for the determination of ferrocyanide (error bars give the potential range when the ECL intensity varies from 95% to 100% of its peak), and the times at a predefined potential value as indicated. (b) Relationships between the ferrocyanide concentration and the square root of the transition time (noted as CP), the times at which ECL gives highest intensity (noted as ECL), and the times for the indicated predefined potential values.
Figure 5
Figure 5. The determination of carbonate alkalinity using an ion-selective membrane electrode. (a) Potential changes with time during galvanostatic pulse of 20 μA for different concentrations of carbonate. (b) ECL responses for different concentrations of carbonate given in millimolar units. (c) Linear calibration curves of the square root of the chronopotentiometric transition time and of the time when ECL intensity reaches its maximum as a function of carbonate concentration.
Figure 6
Figure 6. (a) The transition times (noted as CP), the corresponding times for which ECL intensity reaches its maximum (noted as ECL; error bars indicate the potential change for which ECL intensity is within 5% of its peak), and the times for fixed potential values (0.10 V, 0.15 V, 0.20 V and 0.25 V) in chronopotentiometry. (b) The relationships between the concentration of carbonate and the square root of the transition time (noted as CP), the time at which ECL reaches its peak (noted as ECL), and the time for a fixed potential in chronopotentiometry.
References
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- 1Schwarz, M. A.; Hauser, P. C. Lab Chip 2001, 1, 1– 6, DOI: 10.1039/b103795c1https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD3MXns1yntbg%253D&md5=729e97b79d03c430e713bba36b57c510Recent developments in detection methods for microfabricated analytical devicesSchwarz, Maria A.; Hauser, Peter C.Lab on a Chip (2001), 1 (1), 1-6CODEN: LCAHAM; ISSN:1473-0197. (Royal Society of Chemistry)A review. Sensitive detection in microfluidic anal. devices is a challenge because of the extremely small detection vols. available. Considerable efforts were made lately to further address this aspect and to study techniques other than fluorescence. Among the newly introduced techniques are the optical methods of chemiluminescence, refraction and thermooptics, as well as the electrochem. methods of amperometry, conductimetry and potentiometry. Developments are also in progress to create miniaturized plasma-emission spectrometers and sensitive detectors for gas-chromatog. sepns.
- 2Martı́n, A.; Kim, J.; Kurniawan, J. F.; Sempionatto, J. R.; Moreto, J. R.; Tang, G.; Campbell, A. S.; Shin, A.; Lee, M. Y.; Liu, X.; Wang, J. Epidermal Microfluidic Electrochemical Detection System: Enhanced Sweat Sampling and Metabolite Detection. ACS Sensors 2017, 2 (12), 1860– 1868, DOI: 10.1021/acssensors.7b007292https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2sXhvVait7nM&md5=570525c3f08138dd970692d4f9fb0c2dEpidermal Microfluidic Electrochemical Detection System: Enhanced Sweat Sampling and Metabolite DetectionMartin, Aida; Kim, Jayoung; Kurniawan, Jonas F.; Sempionatto, Juliane R.; Moreto, Jose R.; Tang, Guangda; Campbell, Alan S.; Shin, Andrew; Lee, Min Yul; Liu, Xiaofeng; Wang, JosephACS Sensors (2017), 2 (12), 1860-1868CODEN: ASCEFJ; ISSN:2379-3694. (American Chemical Society)Despite tremendous recent efforts, noninvasive sweat monitoring is still far from delivering its early anal. promise. Here, the authors describe a flexible epidermal microfluidic detection platform fabricated through hybridization of lithog. and screen-printed technologies, for efficient and fast sweat sampling and continuous, real-time electrochem. monitoring of glucose and lactate levels. This soft, skin-mounted device judiciously merges lab-on-a-chip and electrochem. detection technologies, integrated with a miniaturized flexible electronic board for real-time wireless data transmission to a mobile device. Modeling of the device design and sweat flow conditions allowed optimization of the sampling process and the microchannel layout for achieving attractive fluid dynamics and rapid filling of the detection reservoir (within 8 min from starting exercise). The wearable microdevice thus enabled efficient natural sweat pumping to the electrochem. detection chamber contg. the enzyme-modified electrode transducers. The fabricated device can be easily mounted on the epidermis without hindrance to the wearer and displays resiliency against continuous mech. deformation expected from such epidermal wear. Amperometric biosensing of lactate and glucose from the rapidly generated sweat, using the corresponding immobilized oxidase enzymes, was wirelessly monitored during cycling activity of different healthy subjects. This ability to monitor sweat glucose levels introduces new possibilities for effective diabetes management, while similar lactate monitoring paves the way for new wearable fitness applications. The new epidermal microfluidic electrochem. detection strategy represents an attractive alternative to recently reported colorimetric sweat-monitoring methods, and hence holds considerable promise for practical fitness or health monitoring applications.
- 3Liana, D. D.; Raguse, B.; Gooding, J. J.; Chow, E. Sensors 2012, 12, 11505– 11526, DOI: 10.3390/s1209115053https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC38XhtlSjsrvK&md5=2a1e067bad05d764c9cd9c42b14307cbRecent advances in paper-based sensorsLiana, Devi D.; Raguse, Burkhard; Gooding, J. Justin; Chow, EdithSensors (2012), 12 (), 11505-11526CODEN: SENSC9; ISSN:1424-8220. (MDPI AG)A review. Paper-based sensors are a new alternative technol. for fabricating simple, low-cost, portable and disposable anal. devices for many application areas including clin. diagnosis, food quality control and environmental monitoring. The unique properties of paper which allow passive liq. transport and compatibility with chems./biochems. are the main advantages of using paper as a sensing platform. Depending on the main goal to be achieved in paper-based sensors, the fabrication methods and the anal. techniques can be tuned to fulfill the needs of the end-user. Current paper-based sensors are focused on microfluidic delivery of soln. to the detection site whereas more advanced designs involve complex 3-D geometries based on the same microfluidic principles. Although paper-based sensors are very promising, they still suffer from certain limitations such as accuracy and sensitivity. However, it is anticipated that in the future, with advances in fabrication and anal. techniques, that there will be more new and innovative developments in paper-based sensors. These sensors could better meet the current objectives of a viable low-cost and portable device in addn. to offering high sensitivity and selectivity, and multiple analyte discrimination. This paper is a review of recent advances in paper-based sensors and covers the following topics: existing fabrication techniques, anal. methods and application areas. Finally, the present challenges and future outlooks are discussed.
- 4Kalantar-zadeh, K.; Ha, N.; Ou, J. Z.; Berean, K. J. Ingestible Sensors. ACS Sensors 2017, 2 (4), 468– 483, DOI: 10.1021/acssensors.7b000454https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2sXjsFCktb0%253D&md5=054d647ccc87df1c452a3aec12c0158dIngestible SensorsKalantar-zadeh, Kourosh; Ha, Nam; Ou, Jian Zhen; Berean, Kyle J.ACS Sensors (2017), 2 (4), 468-483CODEN: ASCEFJ; ISSN:2379-3694. (American Chemical Society)A review. Ingestible sensing capsules are fast emerging as a crit. technol. that has the ability to greatly impact health, nutrition and clin. areas. These ingestible devices are noninvasive, hence very attractive for customers. With widespread access to smart phones connected to the internet, the data produced by this technol. can be readily seen and reviewed online and accessed by both users and physicians. The outputs provide invaluable information to reveal the state of gut health and disorders as well as the impact of food, medical supplements and environmental changes on the gastrointestinal tract. One unique feature of such ingestible sensors is that their passage through the gut lumen gives them access to each individual organ of the gastrointestinal tract. Therefore, ingestible sensors offer the ability to gather images, monitor luminal fluid and the contents of each gut segment including electrolytes, enzymes, metabolites, hormones and the microbial communities. As such, an incredible wealth of knowledge regarding the functionality and state of health of individuals through key gut biomarkers can be obtained. This paper presents an overview of the gut structure, and discusses current and emerging digestible technologies. The text is an effort to provide a comprehensive overview of ingestible sensing capsules, from both a body physiol. point of view as well as a technol. view and detail the potential information that they can generate.
- 5Chow, K.-F.; Mavré, F.; Crooks, J. A.; Chang, B.-Y.; Crooks, R. M. J. Am. Chem. Soc. 2009, 131, 8364– 8365, DOI: 10.1021/ja902683f5https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD1MXmsFWmtbc%253D&md5=27aeaf85c8b7d3742a249adc9f4f7dcaA Large-Scale, Wireless Electrochemical Bipolar Electrode MicroarrayChow, Kwok-Fan; Mavre, Francois; Crooks, John A.; Chang, Byoung-Yong; Crooks, Richard M.Journal of the American Chemical Society (2009), 131 (24), 8364-8365CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)The authors report a microelectrochem. array composed of 1000 individual bipolar electrodes that are controlled with just 2 driving electrodes and a simple power supply. The system is configured so that faradaic processes occurring at the cathode end of each electrode are correlated to light emission via electrogenerated chemiluminescence (ECL) at the anode end. This makes it possible to read out the state of each electrode simultaneously. The significant advance is that the electrode array is fabricated on a glass microscope slide and is operated in a simple electrochem. cell. This eliminates the need for microfluidic channels, provides a fabrication route to arbitrarily large electrode arrays, and will make it possible to place sensing chemistries onto each electrode using a robotic spotter.
- 6Liu, H.; Crooks, R. M. Anal. Chem. 2012, 84, 2528– 2532, DOI: 10.1021/ac203457h6https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC38XislWjs70%253D&md5=e87e40e8992fa3a5039f00f5da411b19Paper-Based Electrochemical Sensing Platform with Integral Battery and Electrochromic Read-OutLiu, Hong; Crooks, Richard M.Analytical Chemistry (Washington, DC, United States) (2012), 84 (5), 2528-2532CODEN: ANCHAM; ISSN:0003-2700. (American Chemical Society)The authors report a battery-powered, microelectrochem. sensing platform that reports its output using an electrochromic display. The platform is fabricated based on paper fluidics and uses a Prussian blue spot electrodeposited on an indium-doped tin oxide thin film as the electrochromic indicator. The integrated metal/air battery powers both the electrochem. sensor and the electrochromic read-out, which are in elec. contact via a paper reservoir. The sample activates the battery and the presence of analyte in the sample initiates the color change of the Prussian blue spot. The entire system is assembled on the lab. bench, without the need for cleanroom facilities. The applicability of the device to point-of-care sensing is demonstrated by qual. detection of 0.1 mM glucose and H2O2 in artificial urine samples.
- 7Liana, D. D.; Raguse, B.; Gooding, J. J.; Chow, E. ACS Appl. Mater. Interfaces 2015, 7, 19201– 19209, DOI: 10.1021/acsami.5b049417https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2MXhtlOntL%252FO&md5=2910439aa59326fbdf79eb978aa385bbToward Paper-Based Sensors: Turning Electrical Signals into an Optical Readout SystemLiana, Devi D.; Raguse, Burkhard; Gooding, J. Justin; Chow, EdithACS Applied Materials & Interfaces (2015), 7 (34), 19201-19209CODEN: AAMICK; ISSN:1944-8244. (American Chemical Society)Paper-based sensors are gaining increasing attention for their potential applications in resource-limited settings and for point-of-care anal. However, chem. anal. of paper-based electronic sensors is frequently interpreted using complex software and electronic displays which compromise the advantages of using paper. The authors present two semiquant. paper-based readout systems that can visually measure a change in resistance of a resistive-based sensor. The readout systems use electrochromic Prussian blue/polyaniline as an electrochromic indicator on a resistive gold nanoparticle film that is fabricated on paper. When the readout system is integrated with a resistive sensor in an elec. circuit, and a voltage is applied, the voltage drop along the readout system varies depending on the sensor's resistance. Due to the voltage gradient formed along the gold nanoparticle film, the overlaying Prussian blue/polyaniline will change color at voltages greater than its redn. voltage (green/blue for oxidized state and transparent for reduced state). Thus, the changes in resistances of a sensor can be semiquantified through color visualization by either measuring the length of the transparent film (analog readout system) or by counting the no. of transparent segments (digital readout system). The work presented herein can potentially serve as an alternative paper-based display system for resistive sensors in instances where cost and wt. is a premium.
- 8Chow, E.; Liana, D. D.; Raguse, B.; Gooding, J. J. Aust. J. Chem. 2017, 70, 979– 984, DOI: 10.1071/CH171918https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2sXhtlOksLjL&md5=51195faf58f428a76b8da78785cfa284A Potentiometric Sensor for pH Monitoring with an Integrated Electrochromic Readout on PaperChow, Edith; Liana, Devi D.; Raguse, Burkhard; Gooding, J. JustinAustralian Journal of Chemistry (2017), 70 (9), 979-984CODEN: AJCHAS; ISSN:0004-9425. (CSIRO Publishing)Paper-based potentiometric pH sensors allow multiple measurements to be recorded in a cost-effective manner but usually in combination with an external display unit. A potentiometric pH sensor is integrated with an electrochromic readout system all on paper. The potentiometric pH sensor is based on electropolymd. aniline on a conductive gold nanoparticle film working electrode. The voltage output of the sensor is amplified using an operational amplifier and generated across an electrochromic readout system. The readout system comprises four segments of electrochromic Prussian blue/polyaniline on conductive gold nanoparticle films connected by graphite resistive separators. The color of each segment is dependent on the voltage output from the potentiometric sensor and can be used to det. the pH range of a sample or whether the sample pH falls outside a crit. value. This type of integrated paper device can be used for multiple measurements and also be applied to the development of other types of potentiometric sensors.
- 9Zhang, X.; Chen, C.; Yin, J.; Han, Y.; Li, J.; Wang, E. Anal. Chem. 2015, 87, 4612– 4616, DOI: 10.1021/acs.analchem.5b010189https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2MXmsVeltb4%253D&md5=a0f8a997bed0a452a8f0d6b7238a5aedPortable and Visual Electrochemical Sensor Based on the Bipolar Light Emitting Diode ElectrodeZhang, Xiaowei; Chen, Chaogui; Yin, Jianyuan; Han, Yanchao; Li, Jing; Wang, ErkangAnalytical Chemistry (Washington, DC, United States) (2015), 87 (9), 4612-4616CODEN: ANCHAM; ISSN:0003-2700. (American Chemical Society)Here the authors report a novel sensing strategy based on the closed bipolar system, in which the authors use a light emitting diode (LED) to connect a split bipolar electrode (BPE) and generate the luminescent signal in the presence of the target. With this design, the authors have constructed a BPE array for the quick and high-throughput detn. of various electroactive substances with naked eyes. Due to the ultrahigh current efficiency of the closed bipolar system, the sample concn. can be reported by the luminous intensity of the inserted LED without the expensive luminescent agent and instruments. Besides, the stability of the signal is improved because of the electroluminescent property of the LED. To demonstrate the promising applications of the bipolar LED electrode (BP-LED-E), the rapid quantification of four model targets (H2O2, ascorbic acid (AA), glucose, and blood sugar) was achieved based on different principles.
- 10Zhang, X.; Shang, C.; Gu, W.; Xia, Y.; Li, J.; Wang, E. ChemElectroChem 2016, 3, 383– 386, DOI: 10.1002/celc.20150028210https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2MXhtlCks7jJ&md5=5bf3ed6abd9416b6fc1a34a1ff46a982A Renewable Display Platform Based on the Bipolar Electrochromic ElectrodeZhang, Xiaowei; Shang, Changshuai; Gu, Wenlin; Xia, Yong; Li, Jing; Wang, ErkangChemElectroChem (2016), 3 (3), 383-386CODEN: CHEMRA; ISSN:2196-0216. (Wiley-VCH Verlag GmbH & Co. KGaA)We report a renewable display platform based on bipolar electrochem. that uses bipolar electrochromic electrode (BP-EC-E) arrays for high-throughput screening applications. Prussian blue (or another electrochromic material) is electrodeposited on one end of the bipolar electrode (BPE) as the signal reporter, and the other end is for the loading of catalyst. Owing to the quant. relation between the two reactions occurring at both ends of the BP-EC-E, the discoloration speeds (Prussian blue to Prussian white) are related to the amt. or the catalytic activity of the catalysts. Interestingly, the established platform can be used repeatedly, owing to the reversibility of the electrochromic reactions. With this strategy, we have achieved the fast imaging anal. of several electrocatalysts for methanol and ethanol oxidn.
- 11Zhang, X.; Zhang, L.; Zhai, Q.; Gu, W.; Li, J.; Wang, E. Anal. Chem. 2016, 88, 2543– 2547, DOI: 10.1021/acs.analchem.6b0005411https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC28XitFeqtr4%253D&md5=75fd66e2fd3f66fb1ee136b200f46851Self-Powered Bipolar Electrochromic Electrode Arrays for Direct Displaying ApplicationsZhang, Xiaowei; Zhang, Lingling; Zhai, Qingfeng; Gu, Wenling; Li, Jing; Wang, ErkangAnalytical Chemistry (Washington, DC, United States) (2016), 88 (5), 2543-2547CODEN: ANCHAM; ISSN:0003-2700. (American Chemical Society)Here we report a self-powered-bipolar-electrochromic-electrode (termed SP-BP-EC-E) array for the displaying applications including catalyst screening, catalytic activity measurement, and enzyme substrate quantification. By replacing the directional (or active) power source with the isotropic chem. energy to drive the bipolar electrochem. reaction, the driving background signal, bipolar electrode (BPE) background signal, uneven reporting signal and the influence of electrolysis which commonly appear in traditional bipolar systems are effectively eliminated from origin. Thus, the reporting signals from the SP-BP-EC-E arrays can be more direct and reliable to reflect the target nature. Such a SP-BP-EC-E platform exhibits a sensitive response toward the fast anal. of com. Pt black catalyst, NiPdAu hollow nanospheres, glucose dehydrogenase, and glucose. To our knowledge, this test paper-like SP-BP-EC-E is the simplest platform for high-throughput screening to date, which offers a very convenient approach for nonprofessional people to access the complicated screening and fast anal. of the electrocatalysts and biocatalyst activity and quantification of enzymic substrates.
- 12Xing, H.; Zhang, X.; Zhai, Q.; Li, J.; Wang, E. Anal. Chem. 2017, 89, 3867– 3872, DOI: 10.1021/acs.analchem.7b0024612https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2sXktV2mtLs%253D&md5=bae66b962cda370361694ad2e78aa574Bipolar Electrode Based Reversible Fluorescence Switch Using Prussian Blue/Au Nanoclusters Nanocomposite FilmXing, Huanhuan; Zhang, Xiaowei; Zhai, Qingfeng; Li, Jing; Wang, ErkangAnalytical Chemistry (Washington, DC, United States) (2017), 89 (7), 3867-3872CODEN: ANCHAM; ISSN:0003-2700. (American Chemical Society)A highly efficient fluorescence switch system based on a closed bipolar electrode (C-BPE) system is proposed for the first time. Here, Au nanoclusters (Au NCs) were premodified on one pole of the BPE and acted as the fluorescent donor. On the basis of the spectral overlap between the absorbance of electrochromic material Prussian blue (PB) and the fluorescence spectrum of Au NCs, fluorescence quenching ("off" state) induced by the inner filter effect was obsd. Due to the electrochem. reversible redox reaction between PB and Prussian white, switching the polarity of driving voltage could easily achieve the fluorescence recovery of the Au NCs, corresponding to the "on" state. Through the reasonable design of C-BPE and optimization of driving voltage, the on-off ratio of the integrated fluorescence switch was up to 2.7 and a good fatigue resistance, while performing 10 on-off cycles was obtained owing to the good stability of Au NCs and the reversible redox feature of PB. The introduction of BPE made the fluorescence switch more simple and controllable compared with the traditional three-electrode system, which will provide a new route for the design of the elec.-stimuli responsive fluorescence switch, esp. for the integration of the miniaturized device.
- 13Zhai, Q.; Fan, D.; Zhang, X.; Li, J.; Wang, E. NPG Asia Mater. 2017, 9, e421 DOI: 10.1038/am.2017.13213https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2sXhtlygurvO&md5=182db663f09d500122560e7a74b10f10Dual-electrochromic bipolar electrode-based universal platform for the construction of various visual advanced logic devicesZhai, Qingfeng; Fan, Daoqing; Zhang, Xiaowei; Li, Jing; Wang, ErkangNPG Asia Materials (2017), 9 (8), e421CODEN: NAMPCE; ISSN:1884-4057. (Nature Publishing Group)A universal logic platform based on dual-electrochromic bipolar electrodes (BPEs) for the operation of various visual advanced logic devices was designed and constructed for the first time. Two BPEs sepd. by three reaction channels filled with different reaction solns. constituted the closed BPE system and were used as the initial state. Under different input combinations, the electrochem. oxidn. of 2, 2 -azinobis (3-ethylbenzthiazoline-6-sulfonic acid) and the electrodeposition of Prussian blue occurred at different poles simultaneously and triggered rapid color changes that could be easily visualized by the naked eye. By defining the color changes at the two specific poles as outputs, visual advanced logic devices, including an encoder, a decoder, a demultiplexer, a keypad lock and a three-input concatenated logic circuit with two outputs, were successfully constructed.
- 14Zhang, X.; Jing, Y.; Zhai, Q.; Yu, Y.; Xing, H.; Li, J.; Wang, E. Anal. Chem. 2018, 90, 11780– 11784, DOI: 10.1021/acs.analchem.8b0283814https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1cXhslequr%252FP&md5=87d44564f8df941fe81e00192ed1308bPoint-of-Care Diagnoses: Flexible Patterning Technique for Self-Powered Wearable SensorsZhang, Xiaowei; Jing, Yin; Zhai, Qingfeng; Yu, You; Xing, Huanhuan; Li, Jing; Wang, ErkangAnalytical Chemistry (Washington, DC, United States) (2018), 90 (20), 11780-11784CODEN: ANCHAM; ISSN:0003-2700. (American Chemical Society)This paper demonstrated the fabrication of a facile, low-cost, and self-powered platform for point-of-care fitness level and athletic performance monitoring sensor using electrochem. lithog. method and its application in body fluid sensing. Flexible Au/prussian blue electrode was employed as the indicating electrode, where the color change was an indication of fitness level and athletic performance. A piece of Al foil, Au/multiwalled carbon nanotubes (MWCNTs)-glucose dehydrogenase, and Au/polymethylene blue-MWCNTs-lactic dehydrogenase electrodes were used for the detection of ionic strength, glucose, and lactic acid in sweat, resp., which allows the sensor to work without any extra instrumentation and the output signal can be recognized by the naked eyes. The advantages of these sensors are (1) self-powered; (2) readily applicable to the detection of any electroactive substance by an electrochromic material; (3) easy to fabricate via two steps of EDP; and (4) point-of-care. By assembling the energy and sensing components together through a transparent adhesive tape, the proposed self-powered wearable biosensor exhibits superior performances, indicating its broad applied prospect in the point-of-care diagnoses.
- 15Jansod, S.; Cuartero, M.; Cherubini, T.; Bakker, E. Anal. Chem. 2018, 90, 6376– 6379, DOI: 10.1021/acs.analchem.8b0158515https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1cXpvVejtLs%253D&md5=9b8baf19fade2f0723427e4fb7e385b7Colorimetric Readout for Potentiometric Sensors with Closed Bipolar ElectrodesJansod, Sutida; Cuartero, Maria; Cherubini, Thomas; Bakker, EricAnalytical Chemistry (Washington, DC, United States) (2018), 90 (11), 6376-6379CODEN: ANCHAM; ISSN:0003-2700. (American Chemical Society)We present here a general strategy to translate potential change at a potentiometric probe into a tunable color readout. It is achieved with a closed bipolar electrode where the ion-selective component is confined to one end of the electrode while color is generated at the opposite pole, allowing one to phys. sep. the detection compartment from the sample. An elec. potential is imposed across the bipolar electrode by soln. contact such that the potentiometric signal change at the sample side modulates the potential at the detection side. This triggers the turnover of a redox indicator in the thin detection layer until a new equil. state is established. The approach is demonstrated in sep. expts. with a chloride responsive Ag/AgCl element and a liq. membrane based calcium-selective membrane electrode, using the redox indicator ferroin in the detection compartment. The principle can be readily extended to other ion detection materials and optical readout principles.
- 16Zhai, J.; Yang, L.; Du, X.; Xie, X. Anal. Chem. 2018, 90, 12791– 12795, DOI: 10.1021/acs.analchem.8b0321316https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1cXhvVWitrbI&md5=38de0c14e87f4c12ba0cc63482252ce4Electrochemical-to-Optical Signal Transduction for Ion-Selective Electrodes with Light-Emitting DiodesZhai, Jingying; Yang, Liyuan; Du, Xinfeng; Xie, XiaojiangAnalytical Chemistry (Washington, DC, United States) (2018), 90 (21), 12791-12795CODEN: ANCHAM; ISSN:0003-2700. (American Chemical Society)Optical ion sensors normally have a relative narrow sensitive detection window. Here, based on multicolor light-emitting diodes (LEDs), the authors report on an electrochem.-to-optical signal transduction scheme under chronoamperometry control to convert the potentiometric response of ion-selective electrodes (ISEs) to optical output with tunable sensitivity and much wider response range. The sensing principle was demonstrated on K+, Ca2+, and Pb2+. LED light intensity was found to depend linearly on the concn. of monovalent ions. Optical signals could be captured with photomultiplier tubes or digital cameras, and a visual alarming system to monitor abnormal ion concn. was also developed from super-Nernstian electrodes.
- 17Crespo, G. A.; Mistlberger, G.; Bakker, E. J. Am. Chem. Soc. 2012, 134, 205– 207, DOI: 10.1021/ja210600k17https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3MXhs1aqu7nE&md5=94620adacd3ac2e755f0b314bdd7b102Electrogenerated Chemiluminescence for Potentiometric SensorsCrespo, Gaston A.; Mistlberger, Gunter; Bakker, EricJournal of the American Chemical Society (2012), 134 (1), 205-207CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)The authors report here on a generic approach to read out potentiometric sensors with electrogenerated chemiluminescence (ECL). In a 1st example, a potassium ion-selective electrode acts as the ref. electrode and is placed in contact with the sample soln. The working electrode of the three-electrode cell is responsible for ECL generation and placed in a detection soln. contg. tris(2,2'-bipyridyl)ruthenium(II) [Ru(bpy)32+] and the coreactant 2-(dibutylamino)ethanol (DBAE), phys. sepd. from the sample by a bridge. Changes in the sample potassium concn. directly modulate the potential at the working electrode, and hence the ECL output, when a const.-potential pulse is applied between the two electrodes. A linear response of the ECL intensity to the logarithmic potassium concn. between 10 μm and 10 mM was found.
- 18Knight, A. W. TrAC, Trends Anal. Chem. 1999, 18, 47– 62, DOI: 10.1016/S0165-9936(98)00086-718https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaK1MXltFShsw%253D%253D&md5=ce4ddc6ca31c554847b2530f93e3abc0A review of recent trends in analytical applications of electrogenerated chemiluminescenceKnight, Andrew W.TrAC, Trends in Analytical Chemistry (1999), 18 (1), 47-62CODEN: TTAEDJ; ISSN:0165-9936. (Elsevier Science B.V.)A review with 79 refs. The development of anal. applications involving the electrochem. generation of chemiluminescence (ECL) in the last 5 yr is reviewed. The mechanisms of common ECL reactions are summarized, and the potential advantages of ECL over conventional chemiluminescence are discussed. The current limitations of the technique are considered along with how they are being addressed. Finally some pointers as to likely directions of future research are given.
- 19Fahnrich, K. A.; Pravda, M.; Guilbault, G. G. Talanta 2001, 54, 531– 559, DOI: 10.1016/S0039-9140(01)00312-519https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD3MXktVGnur8%253D&md5=cdfc44470f063a3f257e77042d025261Recent applications of electrogenerated chemiluminescence in chemical analysisFahnrich, K. A.; Pravda, M.; Guilbault, G. G.Talanta (2001), 54 (4), 531-559CODEN: TLNTA2; ISSN:0039-9140. (Elsevier Science B.V.)A review with 285 refs. Anal. applications of electrogenerated chemiluminescence (ECL) are reviewed with emphasis on the years 1997-2000. Recent developments are described for the ECL of orgs., metal complexes and clusters, cathodic ECL on oxide covered electrodes, ECL based immunosensors, DNA-probe assays and enzymic biosensors. Mechanisms are given for polyarom. hydrocarbons, luminol/hydrogen peroxide, some cathodic ECL reactions and ruthenium complexes with and without co-reactants. New developments and improvements of techniques and instrumentation and their application to analytes are described. The application of ECL for visualization of electrochem. processes and imaging of surfaces is mentioned.
- 20Richter, M. M. Chem. Rev. 2004, 104, 3003– 3036, DOI: 10.1021/cr020373d20https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD2cXitlWmsLw%253D&md5=b30fc3521d1df4e0b0760d5fb3fbb0d3Electrochemiluminescence (ECL)Richter, Mark M.Chemical Reviews (Washington, DC, United States) (2004), 104 (6), 3003-3036CODEN: CHREAY; ISSN:0009-2665. (American Chemical Society)A review. Electrochemiluminescence ( ECL) involves the generation of species at electrode surfaces that then undergo electron-transfer reactions to form excited states that emit light. By employing ECL-active species as labels on biol. mols., ECL has found application in immunoassays and DNA analyses. Com. systems have been developed that use ECL to detect many clin. important analytes (e.g., α-fetoprotein, digoxin, protein and steroidal hormones, and various antibodies) with high sensitivity and selectivity.
- 21Marquette, C. A.; Blum, L. J. Anal. Bioanal. Chem. 2008, 390, 155– 168, DOI: 10.1007/s00216-007-1631-221https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD2sXhsVKgur%252FN&md5=c57591aa5e9559d146f72b2d9b5d7a1aElectro-chemiluminescent biosensingMarquette, Christophe A.; Blum, Loiec J.Analytical and Bioanalytical Chemistry (2008), 390 (1), 155-168CODEN: ABCNBP; ISSN:1618-2642. (Springer)A review. The present review draws a general picture of the bioanal. applications of electro-chemiluminescent reactions (ECL). Only the two main ECL reactions-i.e. the luminol-based and Ru(bpy)32+-based reactions-are considered for application in the fields of enzyme biosensors, immunochem. biosensors, DNA biosensors, and biochips. The mechanism, principle, and exptl. conditions of these two reactions are described. Then, for each category of anal. tools, exptl. set-ups and performances are presented and discussed.
- 22Miao, W. Chem. Rev. 2008, 108, 2506– 2553, DOI: 10.1021/cr068083a22https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD1cXmtlCqurY%253D&md5=53805dc698b191a4fc2ebef17aeefe9bElectrogenerated Chemiluminescence and Its Biorelated ApplicationsMiao, WujianChemical Reviews (Washington, DC, United States) (2008), 108 (7), 2506-2553CODEN: CHREAY; ISSN:0009-2665. (American Chemical Society)A review. The rapid development of electrogenerated chemiluminescence (ECL) in both fundamentals and applications over the past several years has clearly demonstrated that ECL is a powerful tool for ultrasensitive biomol. detection and quantification. High-throughput, miniaturized biosensors based on ECL technol. capable of multiplexing detection with high sensitivity, low detection limit, and good selectivity and stability will continue to attract the interest of the research community. With further understanding of ECL mechanisms, new highly efficient, tunable ECL systems, both emitters and coreactants, will be developed. Approaches based on ECL enhancement as well as quenching may play an important role in designing new methodologies for sensitive biomol. recognition. Thermodn. and kinetic studies of biomol. interactions using ECL are expected to be further expanded. The combination of ECL with other techniques could lead to the development of new instruments or provide valuable insights into mol. structures and intracellular components of biorelated species. Ultimately, detection of single biomols. will be realized.
- 23Liu, Z.; Qi, W.; Xu, G. Chem. Soc. Rev. 2015, 44, 3117– 3142, DOI: 10.1039/C5CS00086F23https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2MXltVaiurc%253D&md5=957d27a9a9fc4e7616d209a15de5d255Recent advances in electrochemiluminescenceLiu, Zhongyuan; Qi, Wenjing; Xu, GuobaoChemical Society Reviews (2015), 44 (10), 3117-3142CODEN: CSRVBR; ISSN:0306-0012. (Royal Society of Chemistry)The great success of electrochemiluminescence (ECL) for in vitro diagnosis (IVD) and its promising potential in light-emitting devices greatly promote recent ECL studies. More than 45% of ECL articles were published after 2010, and the first international meeting on ECL was held in Italy in 2014. This crit. review discusses recent vibrant developments in ECL, and highlights novel ECL phenomena, such as wireless ECL devices, bipolar electrode-based ECL, light-emitting electrochem. swimmers, upconversion ECL, ECL resonance energy transfer, thermoresponsive ECL, ECL using shape-controlled nanocrystals, and ECL as an ion-selective electrode photonic reporter, a paper-based microchip, and a self-powered microfluidic ECL platform. We also comment on the latest progress in bioassays, light-emitting devices and, the computational approach for the ECL mechanism study. Finally, perspectives and key challenges in the near future are addressed (198 refs.).
- 24Gao, W.; Saqib, M.; Qi, L.; Zhang, W.; Xu, G. Curr. Opin. Electrochem. 2017, 3, 4– 10, DOI: 10.1016/j.coelec.2017.03.00324https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1cXhtVGgsLvK&md5=1e24de4daaab7e9eb15f7b7b0266d262Recent advances in electrochemiluminescence devices for point-of-care testingGao, Wenyue; Saqib, Muhammad; Qi, Liming; Zhang, Wei; Xu, GuobaoCurrent Opinion in Electrochemistry (2017), 3 (1), 4-10CODEN: COEUCY; ISSN:2451-9111. (Elsevier B.V.)A Review. A dynamic progress of methodologies has increased demand for high performance detection technologies for point-of-care testing (POCT). Electrochemiluminescence (ECL) is now established as an important, highly sensitive detection strategy for the development of POCT devices. In this short review, we summarize the recent advances of portable ECL devices, such as portable power sources, bipolar ECL devices, wireless ECL devices, ECL detectors, and microfluidic chips. Moreover, we address the remaining challenges and future perspectives to integrate ECL sensing devices into point-of-care solns.
- 25Fähnrich, K. A.; Pravda, M.; Guilbault, G. G. Talanta 2001, 54, 531– 559, DOI: 10.1016/S0039-9140(01)00312-525https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD3MXktVGnur8%253D&md5=cdfc44470f063a3f257e77042d025261Recent applications of electrogenerated chemiluminescence in chemical analysisFahnrich, K. A.; Pravda, M.; Guilbault, G. G.Talanta (2001), 54 (4), 531-559CODEN: TLNTA2; ISSN:0039-9140. (Elsevier Science B.V.)A review with 285 refs. Anal. applications of electrogenerated chemiluminescence (ECL) are reviewed with emphasis on the years 1997-2000. Recent developments are described for the ECL of orgs., metal complexes and clusters, cathodic ECL on oxide covered electrodes, ECL based immunosensors, DNA-probe assays and enzymic biosensors. Mechanisms are given for polyarom. hydrocarbons, luminol/hydrogen peroxide, some cathodic ECL reactions and ruthenium complexes with and without co-reactants. New developments and improvements of techniques and instrumentation and their application to analytes are described. The application of ECL for visualization of electrochem. processes and imaging of surfaces is mentioned.
- 26Gao, W.; Muzyka, K.; Ma, X.; Lou, B.; Xu, G. Chem. Sci. 2018, 9, 3911– 3916, DOI: 10.1039/C8SC00410B26https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1cXltVyls7s%253D&md5=bb8489eb30266c80343b2fa6592161d1A single-electrode electrochemical system for multiplex electrochemiluminescence analysis based on a resistance induced potential differenceGao, Wenyue; Muzyka, Kateryna; Ma, Xiangui; Lou, Baohua; Xu, GuobaoChemical Science (2018), 9 (16), 3911-3916CODEN: CSHCCN; ISSN:2041-6520. (Royal Society of Chemistry)Developing low-cost and simple electrochem. systems is becoming increasingly important but still challenged for multiplex expts. Here we report a single-electrode electrochem. system (SEES) using only one electrode not only for a single expt. but also for multiplex expts. based on a resistance induced p.d. SEESs for a single expt. and multiplex expts. are fabricated by attaching a self-adhesive label with a hole and multiple holes onto an ITO electrode, resp. This enables multiplex electrochemiluminescence anal. with high sensitivity at a very low safe voltage using a smartphone as a detector. For the multiplex anal., the SEES using a single electrode is much simpler, cheaper and more user-friendly than conventional electrochem. systems and bipolar electrochem. systems using electrode arrays. Moreover, SEESs are free from the electrochemiluminescent background problem from driving electrodes in bipolar electrochem. systems. Since numerous electrodes and cover materials can be used to fabricate SEESs readily and electrochem. is being extensively used, SEESs are very promising for broad applications, such as drug screening and high throughput anal.
- 27Hu, L.; Xu, G. Chem. Soc. Rev. 2010, 39, 3275– 3304, DOI: 10.1039/b923679c27https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3cXptFygs7o%253D&md5=f6d5d09802f9a4fcefbc98ad30a8a944Applications and trends in electrochemiluminescenceHu, Lianzhe; Xu, GuobaoChemical Society Reviews (2010), 39 (8), 3275-3304CODEN: CSRVBR; ISSN:0306-0012. (Royal Society of Chemistry)A review. Electrochemiluminescence (ECL) is chemiluminescence triggered by electrochem. techniques. More than 150 ECL assays with remarkably high sensitivity and extremely wide dynamic range are currently available, and accounts for hundreds of millions of dollars in sales per yr. The recent development of ECL is particularly rapid. After a brief introduction to ECL, this crit. review presents the active and/or emerging areas of ECL research as well as new applications and phenomena of ECL, such as light-emitting electrochem. cell, wireless electrochem. microarray using ECL as photonic reporter, high throughput anal., aptasensors, immunoassays and DNA anal., ECL of nanoclusters and carbon nanomaterials, ECL imaging techniques, scanning ECL microscopy, colorimetric ECL sensor, surface plasmon-coupled ECL, electrostatic chemiluminescence, soliton-like ECL waves, ECL investigation of mol. interaction, and single mol. detection. Finally, some perspectives on this rapidly developing field are discussed (322 refs.).
- 28Afshar, M. G.; Crespo, G. A.; Xie, X.; Bakker, E. Anal. Chem. 2014, 86, 6461– 6470, DOI: 10.1021/ac500968c28https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2cXos1Wrsbw%253D&md5=19d39ea2b127e5d99def536db7dded24Direct Alkalinity Detection with Ion-Selective ChronopotentiometryAfshar, Majid Ghahraman; Crespo, Gaston A.; Xie, Xiaojiang; Bakker, EricAnalytical Chemistry (Washington, DC, United States) (2014), 86 (13), 6461-6470CODEN: ANCHAM; ISSN:0003-2700. (American Chemical Society)The authors explore the possibility to directly measure pH and alky. in the sample with the same sensor by imposing an outward flux of hydrogen ions from an ion-selective membrane to the sample soln. by an applied current. The membrane consists of a polypropylene-supported liq. membrane doped with a hydrogen ionophore (chromoionophore I), ion exchanger (KTFBP), and lipophilic electrolyte (ETH 500). While the sample pH is measured at zero current, alky. is assessed by chronopotentiometry at anodic current. Hydrogen ions expelled from the membrane undergo acid-base soln. chem. and protonate available base in the diffusion layer. With time, base species start to be depleted owing to the const. imposed hydrogen ion flux from the membrane, and a local pH change occurs at a transition time. This pH change (potential readout) is correlated to the concn. of the base in soln. As in traditional chronopotentiometry, the obsd. square root of transition time (τ) is linear in the concn. range of 0.1 mM to 1 mM, using the bases tris(hydroxymethyl)aminomethane, ammonia, carbonate, hydroxide, hydrogen phosphate, and borate. Numerical simulations were used to predict the concn. profiles and the chronopotentiograms, allowing the discussion of possible limitations of the proposed method and its comparison with volumetric titrns. of alky. Finally, the P-alky. level is measured in a river sample to demonstrate the anal. usefulness of the proposed method. As a result of these preliminary results, probably this approach becomes useful for the in situ detn. of P-alky. in a range of matrixes.
- 29Jarolimova, Z.; Crespo, G. A.; Xie, X.; Afshar, M. G.; Pawlak, M.; Bakker, E. Anal. Chem. 2014, 86, 6307– 6314, DOI: 10.1021/ac500416329https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2cXosl2qt7c%253D&md5=87b751d0c6429440e1fc6eddc63b868aChronopotentiometric Carbonate Detection with All-Solid-State Ionophore-Based ElectrodesJarolimova, Zdenka; Crespo, Gaston A.; Xie, Xiaojiang; Ghahraman Afshar, Majid; Pawlak, Marcin; Bakker, EricAnalytical Chemistry (Washington, DC, United States) (2014), 86 (13), 6307-6314CODEN: ANCHAM; ISSN:0003-2700. (American Chemical Society)The authors present here for the 1st time an all-solid-state chronopotentiometric ion sensing system based on selective ionophores, specifically for the carbonate anion. A chronopotentiometric readout is attractive because it may allow one to obtain complementary information on the sample speciation compared to zero-current potentiometry and detect the sum of labile carbonate species instead of only ion activity. Ferrocene covalently attached to the PVC polymeric chain acts as an ion-to-electron transducer and provides the driving force to initiate the sensing process at the membrane-sample interface. The incorporation of a selective ionophore for carbonate allows one to det. this anion in a background electrolyte. Various inner electrolyte and all-solid-state-membrane configurations are explored, and localized carbonate depletion is only obsd. for systems that do not contain ion-exchanger additives. The square root of the transition times extd. from the inflection point of the chronopotentiograms as a function of carbonate specie concn. follows a linear relation. The obsd. linear range is 0.03-0.35 mM in a pH range of 9.50-10.05. By applying the Sand equation, the diffusion coeff. of carbonate is calcd. as (9.03 ± 0.91) 10-6 cm2 s-1, which corresponds to the established value. The reproducibility of assessed carbonate is better than 1%. Addnl., carbonate is monitored during titrimetric anal. as a precursor to an in situ environmental detn. Based on these results, Fc-PVC membranes doped with ionophores may form the basis of a new family of passive/active all-solid-state ion selective electrodes interrogated by a current pulse.
- 30Delahay, P.; Mattax, C.; Berzins, T. Theory of Voltammetry at Constant Current. IV. Electron Transfer Followed by Chemical Reaction. J. Amer. Chem. Soc. 1954, 76, 5319– 5324, DOI: 10.1021/ja01650a01730https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaG2MXhtFWitw%253D%253D&md5=a546bb6357e732467847658149bf6d60Theory of voltammetry at constant current. IV. Electron transfer followed by chemical reactionDelahay, Paul; Mattax, Calvin C.; Berzins, TalivaldisJournal of the American Chemical Society (1954), 76 (), 5319-24CODEN: JACSAT; ISSN:0002-7863.cf. C.A. 48, 5689e. A theoretical treatment is given of electron-transfer processes followed by chem. reaction in voltammetry at const. current. The 4 processes treated are: (1) O + ne = R .dblharw. Z; (2) O + ne = R, R + Z .dblharw. O; (3) M + pX- = MXp(p-n)- + ne; (4) M + pX- = MXp + pe; where O is a reducible substance, R its product of reduction, and Z, a substance not reduced or oxidized at the potentials at which O is reduced. For processes represented by 1 and 2, boundary value problems are set up, the boundary conditions detd., and the problems solved. For 1, the equation for the potential is given in terms of a transition time, τ, which is the time at which the concn. of O is zero at the electrode surface. It is shown that potential-time curves are shifted toward more anodic potentials as the reaction R to Z becomes more rapid. The influence of c.d. is discussed. For 2, the transition times, τc, in the presence of, and τd, in the absence of a catalytic effect are introduced. The ratio, (τc/τd)1/2, is plotted against (kfCZ0 τc)1/2, where kf is a 1st-order rate const. for the forward reaction in 2 and CZ0 is the concn. of Z which is assumed to be const. This can be applied to the detn. of kf if τc and τd are known. The influence of c.d. is discussed, and conclusions are shown to agree with the exptl. results obtained from the catalytic reduction of Ti(IV) in the presence of hydroxylamine. The anodic oxidation of a metal with the formation of a complex by 3 is treated by deriving an expression for the concn. of M+ at the electrode surface in terms of τ and substituting this in the Nernst equation. This is then used to det. the potential for the anodic oxidation of Ag in KCN, and the exptl. and theoretical values are shown to agree. The treatment given is valid only for the equil. formation of one complex. The anodic oxidation of a metal with the formation of a film of insol. substance on the electrode by 4 is given a treatment similar to 3. The resulting equation is used to det. the soly. products of AgCl and AgBr from expts. on the anodic oxidation of Ag in chloride and bromide solns., resp. The values obtained are higher than those given in the literature, primarily because the solid particles formed in the anodic process are very small and, therefore, more sol. The treatment is simplified by assuming films are too thin to offer any barrier to diffusion to and from the electrode. Transition times are derived for spherical and linear diffusion with partial mass transfer by migration in an elec. field of const. intensity.
- 31Gemene, K. L.; Bakker, E. Anal. Chem. 2008, 80, 3743– 3750, DOI: 10.1021/ac701983x31https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD1cXjvFejt70%253D&md5=b1c01b6bd66a0602d2b9f79db306657aDirect Sensing of Total Acidity by Chronopotentiometric Flash Titrations at Polymer Membrane Ion-Selective ElectrodesGemene, Kebede L.; Bakker, EricAnalytical Chemistry (Washington, DC, United States) (2008), 80 (10), 3743-3750CODEN: ANCHAM; ISSN:0003-2700. (American Chemical Society)Polymer membrane ion-selective electrodes contg. lipophilic ionophores are traditionally interrogated by zero current potentiometry, which, ideally, gives information on the sample activity of ionic species. A discrete cathodic current pulse across an H+-selective polymeric membrane doped with the ionophore ETH 5294 may be used for the chronopotentiometric detection of pH in well-buffered samples. However, a redn. in the buffer capacity leads to large deviations from the expected Nernstian response slope. This is explained by the local depletion of hydrogen ions at the sample-membrane interface as a result of the galvanostatically imposed ion flux in direction of the membrane. This depletion is a function of the total acidity of the sample and can be directly monitored chronopotentiometrically in a flash titrn. expt. The subsequent application of a baseline potential pulse reverses the extn. process of the current pulse, allowing one to interrogate the sample with minimal perturbation. In one protocol, total acidity is proportional to the magnitude of applied current at the flash titrn. end point. More conveniently, the square root of the flash titrn. end point time obsd. at a fixed applied current is a linear function of the total acid concn. Probably it is possible to perform rapid localized pH titrns. at ion-selective electrodes without the need for volumetric titrimetry. The technique is explored here for acetic acid, MES and citric acid with promising results. Polymeric membrane electrodes based on poly(vinyl chloride) plasticized with o-nitrophenyl octyl ether in a 1:2 mass ratio may be used for the detection of acids of up to ca. 1 MM concn., with flash titrn. times on the order of a few seconds. Possible limitations of the technique are discussed, including variations of the acid diffusion coeffs. and influence of elec. migration.
- 32Jarolimova, Z.; Crespo, G. A.; Afshar, M. G.; Pawlak, M.; Bakker, E. J. Electroanal. Chem. 2013, 709, 118– 125, DOI: 10.1016/j.jelechem.2013.10.01132https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3sXhvV2qt7zE&md5=b335bc5e2d9c66220cfb1b6301d78957All solid state chronopotentiometric ion-selective electrodes based on ferrocene functionalized PVCJarolimova, Zdenka; Crespo, Gaston A.; Afshar, Majid Ghahraman; Pawlak, Marcin; Bakker, EricJournal of Electroanalytical Chemistry (2013), 709 (), 118-125CODEN: JECHES; ISSN:1873-2569. (Elsevier B.V.)An all solid contact ion-selective electrode based on poly(vinyl chloride) covalently modified with ferrocene moieties allows one to operate the membrane in a chronopotentiometric sensing mode. The membrane is considered as initially non-perm-selective towards anions, and an applied anodic current provokes a defined anion flux in direction of the membrane. With this protocol, a variety of anions can be depleted at the membrane surface. Since this model system does not yet contain an ionophore, their order of preference follows the expected Hofmeister selectivity sequence. The all solid-state configuration tolerates an imposed c.d. of 1.4 μA mm-2, which translates into an upper detection limit of ∼1.2 mM. Higher current densities of up to 31.2 μA mm-2 are possible with addn. of freely dissolved alkyl ferrocene deriv. for an expected upper detection limit of 17.0 mM. Numerical simulations were performed to establish the fundamental basis of the mechanism that takes place in this all solid-state membrane electrode. The oxidn. of bound Fc and the ion-transfer process are considered in the simulation. In view of developing an anal. sensor, different anions are tested. A linear range of two orders of magnitude from 0.01 to 1 mM is found. The membranes are evaluated over several days, displaying practically the same slopes and intercepts, with a relative std. deviation of <2%. Electrochem. limitations of free Fc and bound Fc are crit. evaluated. This approach should allow one to develop a new family of solid-state chronopotentiometric ion sensors that require relatively high current densities.
- 33Sand, H. J. S. Philos. Mag. 1901, 1, 45– 79, DOI: 10.1080/1478644010946259033https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaD28XptlI%253D&md5=66930f7b3424ff19590b664cf5f06c25On the concentration at the electrodes in a solution, with special reference to the liberation of hydrogen by electrolysis of a mixture of copper sulphate and sulphuric acidSand, Henry J. S.Philosophical Magazine (1798-1977) (1901), 1 (1), 45-79CODEN: PHMAA4; ISSN:0031-8086.Since the electrolysis of mixtures first attracted the attention of scientists, three distinct views have been held about the processes which take place at the electrodes. An equation has been derived and proved for calculating the concentration at the electrode of a solution of a single salt from which the metal is being deposited. In the case of mixture, it is possible to arrive at limits for the concentration. Convection currents play a key role in determining the ratio of the two constituents given off at the electrode of an acid copper-sulphate solution.
- 34Bard, A. J. Anal. Chem. 1961, 33, 11– 15, DOI: 10.1021/ac60169a00234https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaF3MXjs12jtA%253D%253D&md5=1f7cbee495306682e6a9ff6afa472b8dEffect of electrode configuration and transition time in solid electrode chronopotentiometryBard, Allen J.(1961), 33 (), 11-15CODEN: ANCHAM; ISSN:0003-2700.To det. the optimum electrode conditions and transition time range for chronopotentiometric analysis, the transition time const., i0γ1/2/C0, was measured for the redn. of Ag(I) and Pb(II), and the oxidn. of I- and hydroquinone, over a transition time range of 0.001-300 sec. The transition time const. increased at long transition times owing to spherical contributions to diffusion and natural convection. An increase at short transition times was ascribed to charging of the double layer, electrode oxidn., and roughness of the electrode. By employing a horizontal electrode with a glass mantle, oriented so that d. gradients were not produced, the transition time const. was maintained const. to ±0.2% with transition times of 7-145 sec.
- 35Yuan, D.; Cuartero, M.; Crespo, G. A.; Bakker, E. Anal. Chem. 2017, 89, 586– 594, DOI: 10.1021/acs.analchem.6b0335435https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC28XhvFKns7rO&md5=736b18423f8b6620d591990a719be73eVoltammetric Thin-Layer Ionophore-Based Films: Part 1. Experimental Evidence and Numerical SimulationsYuan, Dajing; Cuartero, Maria; Crespo, Gaston A.; Bakker, EricAnalytical Chemistry (Washington, DC, United States) (2017), 89 (1), 586-594CODEN: ANCHAM; ISSN:0003-2700. (American Chemical Society)Voltammetric thin layer (∼200 nm) ionophore-based polymeric films of defined ion-exchange capacity have recently emerged as a promising approach to acquire multi-ion information about the sample, in analogy to performing multiple potentiometric measurements with individual membranes. They behave under two different regimes that are dependent on the ion concn. A thin layer control (no mass transport limitation of the polymer film or soln.) is identified for ion concns. of >10 μM, in which case the peak potential serves as the readout signal, in analogy to a potentiometric sensor. However, ion transfer at lower concns. is chiefly controlled by diffusional mass transport from the soln. to the sensing film, resulting in an increase of peak current with ion concn. This concn. range is suitable for electrochem. ion transfer stripping anal. Here, the transition between the two mentioned scenarios is explored exptl., using a highly Ag-selective membrane as a proof-of-concept under different conditions (variation of ion concn. in the sample from 0.1 μM to 1 mM, scan rate from 25 mV s-1 to 200 mV s-1, and angular frequency from 100 rpm to 6400 rpm). Apart from exptl. evidence, a numerical simulation is developed that considers an idealized conducting polymer behavior and permits one to predict exptl. behavior under diffusion or thin-layer control.
- 36Liu, X.; Qi, W.; Gao, W.; Liu, Z.; Zhang, W.; Gao, Y.; Xu, G. Chem. Commun. 2014, 50, 14662– 14665, DOI: 10.1039/C4CC06633B36https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2cXhslCis7bL&md5=9eff7c0ca7299c6d34f7d3f299066b19Remarkable increase in luminol electrochemiluminescence by sequential electroreduction and electrooxidationLiu, Xiaoyun; Qi, Wenjing; Gao, Wenyue; Liu, Zhongyuan; Zhang, Wei; Gao, Ying; Xu, GuobaoChemical Communications (Cambridge, United Kingdom) (2014), 50 (93), 14662-14665CODEN: CHCOFS; ISSN:1359-7345. (Royal Society of Chemistry)Luminol electrochemiluminescence is dramatically increased by about five hundred times by taking full advantage of both electrochem. redn. and electrochem. oxidn. using simple linear sweep voltammetry, leading to sensitive detection.
- 37Sakura, S. Anal. Chim. Acta 1992, 262, 49– 57, DOI: 10.1016/0003-2670(92)80007-T37https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaK38Xks1Wrtr8%253D&md5=ce777aa3fcae9fb6416f90260a2906c5Electrochemiluminescence of hydrogen peroxide-luminol at a carbon electrodeSakura, SachikoAnalytica Chimica Acta (1992), 262 (1), 49-57CODEN: ACACAM; ISSN:0003-2670.Electrochemiluminescence (ECL) was used to detect hydrogen peroxide in aq. solns. in the presence of electrolytically oxidized luminol. Using a glassy carbon electrode, the ECL mechanism could be selected by the applied potential. Luminol is oxidized to the excited intermediate (diazasemiquinone radical or diazaquinone) at around 0.5 V vs. SCE in pH 7.4 aq. soln.; above 1.0 V, hydrogen peroxide is oxidized to superoxide and the amino group of luminol is also oxidized. Therefore, the ECL mechanism is different depending on whether the applied potential is between 0.5 and 1.0 V or more pos. At the higher potentials, complex fluorophores are involved. On the other hand, at the lower potentials the fluorophore is simple and the ECL spectrum shows a simple max. emission peak. The quality of the data obtained at 0.7 V is better than that at 1.2 V. The detection limit of hydrogen peroxide is 66 pmol with a relative std. deviation of 1.1% (n = 5) at a signal-to-noise ratio of 6.
- 38Vitt, J. E.; Johnson, D. C.; Engstrom, R. C. J. Electrochem. Soc. 1991, 138, 1637– 1643, DOI: 10.1149/1.208584638https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaK3MXkvVSkurg%253D&md5=f135d00166b037a5e34e77228963c37aThe effect of electrode material on the electrogenerated chemiluminescence of luminolVitt, Joseph E.; Johnson, Dennis C.; Engstrom, Royce C.Journal of the Electrochemical Society (1991), 138 (6), 1637-43CODEN: JESOAN; ISSN:0013-4651.The oxidn. of luminol and its concomitant electrogenerated chemiluminescence (ECL) were studied at several electrode materials by voltammetry and chronoamperometry. The ECL intensity (IECL) was inversely related to the activity of the electrodes. The lowest IECL was measured when luminol was oxidized to 3-aminophthalate (n ≃ 4 equiv mol-1) at a nearly mass-transport limited rate at glassy carbon. The ECL kinetics were studied and the order of the reaction with respect to luminol was 3/2 at concns. to ca. 1mM when O2 was the coreactant. In the presence of H2O2, the ECL reaction was first order with respect to luminol. A reaction mechanism is proposed that is consistent with the kinetic data and the inverse relationship between electrode activity and IECL. The implications of these results are discussed with respect to imaging the spatial distribution of c.d. at electrode surfaces, including that of PbO2 films activated by adsorbed Bi(V). A value of 6.6 × 10-6 cm2s-1 was detd. for the diffusion coeff. of luminol in 0.1M NaOH.
- 39Choi, J.-P.; Bard, A. J. Anal. Chim. Acta 2005, 541, 141– 148, DOI: 10.1016/j.aca.2004.11.075There is no corresponding record for this reference.
- 40Cui, H.; Zhang, Z. F.; Zou, G. Z.; Lin, X. Q. J. Electroanal. Chem. 2004, 566, 305– 313, DOI: 10.1016/j.jelechem.2003.11.04140https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD2cXjtFGjsLs%253D&md5=9d42970ec55b8ef6249e24579b41a13dPotential-dependent electrochemiluminescence of luminol in alkaline solution at a gold electrodeCui, Hua; Zhang, Zhi-Feng; Zou, Gui-Zheng; Lin, Xiang-QinJournal of Electroanalytical Chemistry (2004), 566 (2), 305-313CODEN: JECHES ISSN:. (Elsevier)The behavior of luminol electrochemiluminescence (ECL) at a polycryst. gold electrode was studied under conventional cyclic voltammetric (CV) conditions. At least six ECL peaks were obsd. at 0.28 (ECL-1), 0.56 (ECL-2), 0.95 (ECL-3), 1.37 (ECL-4), -0.43 (ECL-5) and 1.00 (ECL-6, a broad wave after the reverse scan from +1.66) V (vs. SCE), resp., on the curve of ECL intensity vs. the potential. These ECL peaks were found to depend on the presence of O2 and N2, the pH of the soln., KCl concn., scan rate, and potential scan ranges. The emitter of all ECL peaks was identified as 3-aminophthalate by analyzing the CL spectra. It is believed that ECL-1 at 0.28 V was correlated to luminol radicals produced by the electro-oxidn. of luminol anion and ECL-2 at 0.56 V was caused by the reaction of luminol radical anions with gold oxide formed on the electrode surface. ECL-1 and ECL-2 could be strongly enhanced by O2 and O2√-. ECL-3 at 0.95 V was likely to be due to the reaction of luminol radical anions with O2 oxidized by OH-. ECL-4 at 1.37 V suggested that OH- was electro-oxidized to HO2- at this potential and then to O2√-, which reacted with luminol radical anions to produce light emission. ECL-5 at -0.43 V seems to be due to the reaction of luminol with ClO- electrogenerated at higher pos. potential and HO2- electrogenerated at neg. potential. ECL-6 was attributed to the reaction of luminol radical anions and ClO- electrogenerated at higher pos. potential. The results indicated that luminol ECL can be readily initiated by various oxygen-contg. species electrogenerated at different potentials, leading to multi-channel light emissions. Furthermore, the present work also reveals that ECL-2 is a predominant ECL reaction route at a gold electrode with higher potential scan rates under CV conditions.
Supporting Information
Supporting Information
The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.analchem.9b00787.
Theory for the simulation of chronopotentiometric responses with the finite difference method, pictures of the experimental setup, time derivatives of the chronopotentiograms for the detection of ferrocyanide and carbonate (PDF)
Example of ECL response at 3.45 mM ferro/ferricyanide concentration (AVI)
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