Rapid Prototyped Optically Transparent Thin‐Layer Electrode Holder for Spectroelectrochemistry in Bench‐Top Spectrophotometers

A new optically transparent thin layer electrode (OTTLE) cell and holder have been designed to facilitate spectroelectrochemical measurements in standard bench‐top absorbance and fluorescence spectrophotometers. The use of rapid prototyping for the OTTLE cell holder combined with the selection of inexpensive OTE materials results in a practical, low‐cost spectroelectrochemical cell. The cell was characterized by thin‐layer cyclic voltammetry and coulometry of ferricyanide/ferrocyanide. Spectroelectrochemistry of tris‐(2,2′‐bipyridine) ruthenium(II) chloride (Ru(bpy)₃Cl₂) and 1‐hydroxypyrene (1‐pyOH) was done with commercially available bench‐top absorbance and fluorescence spectrophotometers. The good correlation between the results obtained and the known properties of each compound demonstrate that the OTTLE cell and holder provide an effective means for making spectroelectrochemical measurements in bench‐top absorbance and fluorescence spectrophotometers.     

超薄层红外光透电解池的设计和应用

采用真空镀膜技术制得了超薄型红外光透极电极，设计了适用于水溶液体系和多种固体电极体系的红外光透薄层电解池，通过亚铁氰化钾水溶液／金电极体系和亚硫酰氯／碳电极体系的现场红外光谱电化学测试证明：该电解池具有结构简单，光谱响应灵敏，适用范围较宽等优点。     

Polymer‐coated Boron Doped Diamond Optically Transparent Electrodes for Spectroelectrochemical Sensors

Spectroelectrochemical sensors combine electrochemistry, spectroscopy, and partitioning into a film to provide improved selectivity for the target analyte. The sensor usually consists of an optically transparent electrode (OTE) coated with a charge selective polymer film. The polymer film is chosen to pre‐concentrate analyte at the OTE surface to improve the sensitivity and provide selectivity against like charged interferences. OTEs such as Indium Tin Oxide (ITO) have been used extensively for spectroelectrochemical sensors, but little is known about the applicability of such sensors using other OTE materials, such as Boron Doped Diamond (BDD). One distinct advantage of BDD OTEs over ITO OTEs is their significant increase in sensitivity for organic compounds, such as 4‐aminophenol and hydroquinone. We have developed absorption and fluorescence‐based sensing methods with a BDD OTE coated with a sulfonated ionomer film, Nafion. This is demonstrated with tris(2,2′‐bipyridyl)ruthenium(II) ion [Ru(bpy)₃²⁺] using an attenuated total reflectance (ATR) flow cell setup for both absorption and fluorescence. With a Nafion coated BDD optically transparent thin layer electrode (OTTLE), we developed a fluorescence based sensor for a common polyaromatic hydrocarbon (PAH), 1‐hydroxypyrene (1‐pyOH), achieving a detection limit of 80 nM (17 ppb). This work manifests new sensing applications while broadening the use of spectroelectrochemistry, OTEs, and BDD as an electrode material.     

A Colloidal Au Monolayer Modulates the Conformation and Orientation of a Protein at the Electrode/Solution Interface

The orientation and conformation of adsorbed cytochrome c (cyt c) at the interface between an electrode modified with colloidal Au and a solution were studied by electrochemical, spectroscopic, and spectroelectrochemical techniques. The results indicate that the colloidal Au monolayer formed via preformation of an organic self‐assembled monolayer (SAM) can increase the electronic coupling between the SAM and cyt c in the same manner as bifunctional molecular bridges, one functional group of which is bound to the electrode surface while the other interacts with the protein surface. The approach of cyt c to the modified electrode/solution interface can be assisted by strong interactions of the intrinsic charge of colloidal particles with cyt c, while the heme pocket remains almost unchanged due to the screening effect of the negatively charged field created by the intrinsic charge. The conformational changes of cyt c induced by its adsorption at a bare glassy carbon electrode/solution interface and the effect of the electric field on the ligation state of the heme can be avoided at the colloidal‐Au‐modified electrode/solution interface. Finally, a possible model for the adsorption orientation of cyt c at the colloidal‐Au‐modified electrode/solution interface is proposed.     

一种铂网栅薄层光谱电化学池的制作及表征

以铂网栅电极作工作电极,设计制作了一种应用于紫外-可见光谱电化学研究的新型光透薄层电化学池（OTTLE）,并以铁氰化钾-亚铁氰化钾体系对此光谱化学池进行了表征。铁氰化钾-亚铁氰化钾体系在该池中有良好的循环伏安特性,并可获得良好的紫外-可见光谱。测得的克式量电位E^0,电子转移数n与文献结果一致。     

甲醇是极氧化的现场FTIR透射差谱研究

利用现场透射红外差谱方法研究了在无水1mol/LiClO~4甲醇溶液中甲醇在Pt电极上的阳极氧化。实验采用了细网格Pt电极和薄层电解池。各电位下的FTIR透射差谱反映了溶液中电极反应的变化。结果表明甲醇可被氧化成甲醛,且随电位的提高可进一步氧化成甲酸甲酯。     

Electrochemical and spectroelectrochemical properties of manganese reconstituted myoglobin

Electrochemical and spectroelectrochemical properties of manganese(III) reconstituted myoglobin (Mn(III)–Mb) have been investigated. No redox wave of Mn(III)–Mb was observed at a highly hydrophilic indium oxide electrode on which rapid direct electron transfer of native myoglobin took place, suggesting the electron transfer reaction of Mn(III)–Mb at an indium oxide electrode is very slow. The rate constant of the chemical reduction of Mn(III)–Mb with dithionite was ca. 20 times smaller than that of native Mb. Using an optically transparent thin layer electrode (OTTLE) cell and Oxazine-170 perchlorate, 5,9-bis(diethylamino)-10-methyl-benzo[a]phenoxazonium perchlorate, as an electron transfer mediator, the redox potential for the Mn(III) Mn(II)–Mb couple was estimated to be −0.32 V versus Ag AgCl (sat. KCl) at 25°C.     

In situ transmission difference FTIR spectroscopic investigation on anodic oxidation of methanol in aqueous solution

In situ transmission difference FTIR spectroscopy method was introduced for studying the anodic oxidation of methanol in acid aqueous solution. A minigrid Pt optically transparent thin layer electrode was used as working electrode. This method has the ability to clarify the identity of species involved in the oxidation process both in solution and adsorbed at the surface of electrode. From the results of in situ transmission difference FTIR spectroscopy measurement it was found that HCHO, HCOOH, HCOOCH₃ and CH₂(OCH₃)₂ could be formed in the oxidation process of methanol. The final product was CO₂. The adsorbed poisonous intermediate CO was detected. It was formed at near 0.6 V and became significant at 0.9 V, where the oxidation current was inhibited. The in situ transmission difference FTIR spectroscopy method is a very convenient, relative simplicity and efficient method for investigating the electrochemical process, and could be as a good candidate for further application.     

新式夹心型光透薄层光谱电化学电解池

本文设计了一种新式夹心型光透薄层紫外-可见光谱电化学池。该池采用铂网工作电极,两侧平行放置铂片为对极置于同一石英窗口夹层中,同时以聚四氟乙烯隔离膜作为边际限制器,结合池内小孔道设置内参比点进行精确的电位控制,具有理想的光谱电化学响应。利用循环伏安、循环电位-吸收、恒电位现场光谱、双电位跃-计时电量、双电位跃-计时吸收等技术,对铁氰化钾在氯化钾溶液中的行为进行了表征。     

Characterization of ABTS at a Polymer‐Modified Electrode

ABTS, 2,2′‐azinobis(3‐ethylbenzothiazoline‐6‐sulfonate), a colorless dianion that forms a colored radical upon oxidation, was characterized with electrochemistry and spectroscopy and demonstrated to be a detectable analyte in a polymer‐modified spectroelectrochemical sensor. Three positively charged polymers were incorporated into a thin film on an indium tin oxide (ITO) optically transparent electrode and used to concentrate ABTS at the electrode surface. Of the three films, poly(vinylbenzyl trimethyl ammonium chloride)‐poly(vinyl alcohol) (PVTAC‐PVA), poly(diallyldimethylammonium chloride)‐silica (PDMDAAC‐SiO₂), and quaternized poly(4‐vinyl‐N‐methylpyridinium nitrate)‐silica (QPVP‐SiO₂), PVTAC‐PVA demonstrated the best ability to absorb ABTS. Within 20 min, a change of 0.2 absorbance units at 417 nm and 13.6 μA/cm² in anodic peak current density in cyclic voltammetry at a scan rate of 0.025 V/s were observed.     

光谱电化学研究(Ⅲ)——己烯雌酚在光透薄层电极上的氧化反应及其产物的重排

己烯雌酚(DES)是一种人工合成的非甾类雌激素,药理病理研究表明有致癌作用,这与它在体内代谢过程中产生很活泼的中间体4,4′-己烯雌醌(DESQ)有关,DESQ在水和甲醇中重排生成双烯雌酚Z,Z-DIES,也是DES在体内外氧化代谢的主要产物,故这方面的研究已受到人们重视,本文研究了在二茂铁催化下,使DES在光透薄层金网电极上氧化成DESQ,并重排成Z,Z-DIES,用单电位跃-计时吸收光谱法测得其重排反应的速率常数。     

Use of multivariate curve resolution analysis in the spectroelectrochemistry of 9,10-anthraquinone reduction in dimethylformamide solution

A multivariate curve resolution analysis has been conducted to deconvolute the spectroelectrochemical data of 9,10-anthraquinone (AQ) reduction. The experiments were carried out in dimethylformamide solution containing small amounts of benzoic acid as a proton source at an optically transparent thin layer electrode (OTTLE). Two electrochemical techniques, namely a potential step method and chronoabsorptiometry were employed. In the former, the absorbance spectra of anthraquinone solutions at different applied potentials were recorded, and in the latter technique, a −1.90 V potential was applied to the OTTLE and the absorbance spectra of the solution were recorded at different time intervals. For both techniques, factor analysis revealed that three chemical components coexist in the system, which can be attributed to AQ⁻, AQH⁻ and AQ²⁻. By using a multivariate curve resolution analysis, the concentration profiles and pure spectra of the components were determined. The results of the potential step method revealed that the maximum amount of AQ⁻ is produced at −1.25 V, and application of more negative potentials causes an decreased amount of AQ⁻ at the expense of the evolution of AQH⁻. Finally, the AQ²⁻ species is produced at −1.6 V. The chronoabsorptiometric results showed that AQ⁻ is not stable at 1.9 V and rapidly converts to AQ²⁻.     

Spectroelectrochemical Evaluation of a ZnO Optically Transparent Electrode Prepared by the Spin‐spray Technique

We present a novel zinc oxide (ZnO) optically transparent electrode (OTE) prepared by the spin‐spray technique for spectroelectrochemistry. The spin‐spray technique can deposit ZnO film at a low cost, high rate deposition, and at a low temperature (<100 °C) in a single step. This new technique provides good optical transparency and electrical conductivity for ZnO. The electrochemical and spectroelectrochemical properties of the ZnO electrode were investigated for varying thicknesses of ZnO using methylene blue as a redox indicator. A ZnO OTE chip that includes three electrodes on a glass chip was developed for thin‐layer spectroelectrochemistry. Moreover, the ZnO films were successfully applied in an electrochemical‐localized surface plasmon resonance (LSPR) method for methylene blue detection by using them as a transparent conducting substrate for loading gold nanoparticles.     

汞修饰掺锡三氧化二铟导电玻璃光透薄层电化学池的设计

报道了汞膜修饰掺锡三氧化二铟导电玻璃电极的制备及其薄层电化学池的设计，测试限电极和薄层的光、电化学性能，在水溶液中，与基底电极相比，该电极的负电位范围增加了７００ｍＶ，并表现出普通汞电极的电化学 性质，以此电极制得的电极制得的薄层层池可适用于氧化还原电位较负的电化学过程的光谱电化学研究及金属离子的电化学分析。     

C60电化学还原的稳态性质研究

自1990年9月Kratschmer等报导了C_(60)的常量制备和提纯以来,有关C_(60)及其他富勒炭分子(Fullerens)的研究报导与日俱增,成为近三年来最为活跃的研究领域之一.由于C_(60)的特殊结构,在电化学行为上也表现出十分独特的反应性质,如容易实现多电子氧化还原反应,可逆加氢及能形成离子嵌入电极材料等.本工作采用微电极方法研究了C_(60)稳态极化行为,测定了C_(60)的扩散系数和反应电子数,并通过现场紫外可见光谱电化学方     

Potential-modulation spectroscopy at solid/liquid and liquid/liquid interfaces.

Potential-modulation spectroelectrochemical methods at solid/liquid and liquid/liquid interfaces are reviewed. After a brief summary of the basic features and advantages of the methods, practical applications of potential-modulation spectroscopy are demonstrated using our recent studies of solid/liquid and liquid/liquid interfaces, including reflection measurements for a redox protein on a modified gold electrode and fluorescence measurements for various dyes at a polarized water/1,2-dichloroethane interface. For both interfaces, the use of linearly polarized incident light enabled an estimation of the molecular orientation. The use of a potential-modulated transmission-absorption measurement for an optically transparent electrode with immobilized metal nanoparticles is also described. The ability of potential-modulated fluorescence spectroscopy to clearly elucidate the charge transfer and adsorption mechanisms at liquid/liquid interfaces is highlighted.     

Spectroelectrochemical Sensing Based on Multimode Selectivity Simultaneously Achievable in a Single Device. 19. Preparation and Characterization of Films of Quaternized Poly(4‐vinylpyridine)‐silica

Quaternized poly(4‐vinylpyridine) (QPVP) has been incorporated as an anion exchanger into sol‐gel derived silica films for use in a spectroelectrochemical sensor. The preparation, characteristics and performance of these films are described. The films, which are spin‐coated onto the surface of a planar optically transparent electrode, are optically transparent and uniform. Scanning electron microscopy and spectroscopic ellipsometry have been used to examine film structure, thickness and optical properties. These films have been shown both spectroscopically and electrochemically to preconcentrate ferrocyanide, a model analyte for the sensor. The films can be regenerated for multiple measurements by exposure to 1 M KNO₃. The effects of polymer molecular weight and storage conditions on film performance are described. The overall response of this film is comparable to the poly(dimethyldiallylammonium chloride)‐silica films previously used for this sensor.     

阳离子艳蓝的薄层光谱电化学研究

用薄层光谱电化学技术研究了阳离子艳蓝的电还原过程。薄层循环伏安图表明阳离子艳蓝有一对接近可逆的氧化还原峰。从光谱发现它有顺反异构体互变现象与变色效应。在氧存在时，循环伏安图和光谱图上均出现新峰，推测阳离艳蓝分子与氧分子能形成电荷转移络合物。测得阳离艳蓝电还原的式电极电势，电子转移数以及扩散系数等参数。并讨论了可能的电极过程。     

Analytical aspects of absorption spectroelectrochemistry at a platinum electrode-II Quantitative basis and study of organic compounds

The theoretical basis for a new spectroelectrochemical technique, in which a narrow light-beam is passed at grazing incidence over a plane electrode surface, has been derived. Agreement between theoretical and experimental behaviour has been obtained for a number of organic molecules with well-defined redox behaviour. The advantages of this technique over other spectroelectrochemical techniques are discussed with respect to potential applications in quantitative analysis and electrochemical studies.     

Assessing a Spectroelectrochemical Sensor’s Performance for Detecting [Ru(bpy)3]2+ in Natural and Treated Water

A spectroelectrochemical sensor that combines three modes of selectivity in a single device was evaluated in natural and treated water samples using tris‐(2,2′‐bipyridyl) ruthenium(II) dichloride hexahydrate, [Ru(bpy)₃]²⁺, as a model analyte. The sensor was an optically transparent indium tin oxide (ITO) electrode coated with a thin film of partially sulfonated polystyrene‐block‐poly(ethylene‐ran‐butylene)‐block‐polystyrene (SSEBS). As the potential of the ITO electrode was cycled from +0.7 to +1.3 V, the analyte changed from the colored [Ru(bpy)₃]²⁺ complex to colorless [Ru(bpy)₃]³⁺ complex and the change in absorbance at 450 nm was used as the optical signal for quantification. Calibration curves were obtained for [Ru(bpy)₃]²⁺ in natural well water, river water and treated tap water with detection limits of 108, 139 and 264 nM, respectively. A standard addition method was developed to determine an ‘unknown’ spike addition concentration of [Ru(bpy)₃]²⁺ in well water. The spectroelectrochemical sensor determined the concentration of [Ru(bpy)₃]²⁺ spiked into a sample of Hanford well water to be 0.39±0.03 µM versus the actual concentration of 0.40 µM.