In-situ FTIR spectro-electrochemistry of polyaniline

The structure and the electrochemical oxidation reactions of polyaniline in an organic electrolyte are studied usingin-situ FTIR spectroscopy. In the first oxidation process a decrease of the N-H absorption band is observed, indicating a loss of hydrogen atoms. In the second oxidation step anion intercalation occurs. A broad absorption band at 4000 cm^–1 is assigned to free carrier transitions in the conducting form of polyaniline.     

Using FTIR spectroscopy to detect sericin on historic silk

Silks represent some of the most precious ancient and historic textile artefacts in collections worldwide.Their optimum preservation demands an appreciation of their characteristics.One important concern,especially with regard to ancient Chinese silks,is whether the fabrics have been degummed.Silks with remnant sericin gum coating the fibroin fibres would require different conservation protocol.In previous research on aged silks,the presence of sericin has been inferred from amino acid analysis of hydrolysa...     

Impedance spectroscopy of lithium-carbon electrodes

The methods of coulometric titration and electrode impedance spectroscopy are used in studying the behavior of carbon film electrodes free of binding and conducting additives in the course of reversible lithium intercalation from nonaqueous electrolytes. The electrodes with the high and low degrees of graphitization are studied. The measurements are performed in the frequency range from 10⁵ to 10^?2 Hz with the lithium concentration in intercalate varied from 0.025 mol/cm³ (corresponds to LiC₆) to a state free of lithium. The factors responsible for the hysteresis in charge-discharge curves, the versions of equivalent circuits (EC) suitable for modeling the impedance spectra of Li _x C₆ electrodes, the dependence of EC parameters and the lithium diffusion coefficient on the concentration are discussed. It is shown that all experimental impedance spectra can be adequately modeled by a common general EC. The concentration dependences are consistent with the earlier data of pulse methods. The diffusion coefficient varies approximately from 10^?12 to 10^?13 cm²/s.     

Determination of the molecular structure of diacetylene from high-resolution FTIR spectroscopy

The high-resolution infrared absorption spectra of eight²H or¹³C substituted isotopomers of diacetylene have been recorded, and the bands corresponding to thev ₄ fundamental andv ₆ combination of the major isotopomer have been analyzed using a Loomis-Wood-type program. Effective ground-state rotational constants have been obtained from ground-state combination differences. A number ofr ₀,r _s,r _m , and (r _m )_corr structures have been calculated from the available data and are compared to those obtained by ab initio methods. The (r _m )_corr structure, which is a reliable near-equilibrium structure of diacetylene, isr _C–H=106.131(13) pm;r _C–C=137.081(16) pm;r _C-C=120.964(14). (r _m )_corr structures of the related molecules cyanogen, cyanoacetylene, and cyanodiacetylene have been calculated, and near-equilibrium structures of triacetylene and dicyanoacetylene have been predicted.     

Impedance spectroscopy of lithium-tin film electrodes

A method of electrochemical impedance spectroscopy was used to study the reversible lithium intercalation from nonaqueous electrolyte into tin films with the thickness of 0.1–1 μm. The impedance spectra of lithium-tin (Li _x Sn) electrodes have a complicated shape depending on the electrode state and prehistory; they reflect the occurrence of several consecutive and parallel processes, including the lithium migration, diffusion, and accumulation. The formation of a solid-electrolyte layer on the surface at Li intercalation into Sn is observed. Equivalent circuits are proposed that adequately model the experimental data on the Li _x Sn electrodes both freshly prepared and after prolonged cycling. Problems associated with the choice of equivalent circuits and determination of their parameters, the accuracy of the diffusion coefficient determination, the trends in the parameters’ variation with electrode potential (composition) are discussed.     

原位衰减全反射表面增强红外光谱实验技术

介绍了原位研究电极,溶液界面反应的技术--衰减全反射表面增强红外光谱实验技术(ATR-SEIRAS)的产生背景和工作原理,重点描述了ATR-SEIRAS实验技术的关键:光谱电化学池的构造和薄膜电极的制备.与IRAS相比,ATR-SEIRAS技术可以更容易消除溶剂的背景吸收,获得较高的表面灵敏度,而且允许物质在电极表面自由扩散.与循环伏安相结合,利用ATR-SEIRAS技术可以实时监测电极,溶液界面问的反应.选择了利用ATR-SEIRAS实验技术原位研究功能表面的构造和性质、分子识别和反应中间体的形成等方面的应用实例,分析了ATR-SEIRAS实验技术的研究方向.     

Infrared study of iron impurities in polycrystalline solar grade silicon

In this work the role of Fe impurities introduced in boron doped polycrystalline solar grade silicon is examined by means of low temperature absorption measurements in the far infrared. In particular, the results can be explained in term of formation of boron acceptor-iron donor complexes.     

利用原位红外光谱研究钙钛矿复合半导体CH_3NH_3PbI_3的稳定性

利用高压原位红外光谱法实时跟踪监测了CH_3NH_3PbI_3在高压氮气以及不同含量氧气气氛中加热时的变化规律.发现CH_3NH_3PbI_3对氧气十分敏感,当氮气中含有1%(体积分数)的氧气时,CH_3NH_3PbI_3加热到150℃发生分解;继续提高氧气含量到21%,温度升高到100℃时CH_3NH_3PbI_3即发生分解;若在常压高纯氮气中加热,其分解温度则能提高到250℃;若将氮气压力提高到4.0 MPa,CH_3NH_3PbI_3的分解温度进一步提高到270℃.实验结果表明,提高压力和减少环境中的氧含量是改善钙钛矿复合半导体稳定性的有效方法.相应地,复合半导体光电子器件的热处理过程可以在更高的温度下进行,从而有希望获得性能更加优良的钙钛矿复合半导体光电子器件.     

FTIR spectroscopy of monomolecular layers and multilayers of organic molecules on solid substrates

A method for measuring grazing incidence reflection spectra of monomolecular organic layers is presented which involves the use of a stepmotor-driven translation stage to alternately measure the covered and uncovered part of a metal substrate and averaging of the spectra from several such cycles. The method is applied to Langmuir-Blodgett films of poly(octadecylmethacrylate).     

原位红外光谱法研究对氯苯酚在Pt电极上的电氧化行为

采用原位红外光谱法研究了碱性条件下对氯苯酚(PCP)在Pt电极上电化学氧化的脱氯反应机理. 研究结果表明Pt电极对PCP有良好的电化学反应活性, 其氧化过程首先是对氯苯酚负离子氧化生成对氯苯氧自由基, 该自由基可与对氯苯酚负离子作用生成芳香醚低聚物; 随着电位升高, 对氯苯酚负离子经电化学氧化生成了苯二酚盐(还可能存在其氧化产物不饱和羧酸盐); 当电位继续升高, 苯二酚盐进一步氧化形成苯醌; 最后, 在Pt表面生成小分子羧酸盐, 同时生成了最终产物CO2. 但由于芳香醚低聚物等不溶性聚合物膜的形成并吸附在Pt电极表面, 可造成Pt电极毒化, 使得Pt电极在使用过程中逐渐失去活性.     

基于超微电极的原位电化学拉曼光谱

原位电化学拉曼光谱是一种重要的光谱电化学技术.基于超微电极的原位电化学拉曼光谱将拉曼光谱反映的结构信息与电极表面的电化学过程从实验上严格对应和关联,为深刻理解电化学反应机理提供依据.本文综述了采用超微电极作为工作电极的原位电化学拉曼光谱的研究方法和应用进展,总结了应用超微电极作为工作电极开展电化学拉曼光谱实验的方法和具有表面增强拉曼活性的超微电极制备方法,展示了如何利用在超微电极表面获得的拉曼光谱与界面电化学过程的严格关联研究单个锌颗粒电化学氧化过程、吡啶分子在Au电极表面的电化学吸附过程,以及如何利用该技术能以高的信噪比和灵敏度同时测量光电流与分子反应这一特性研究对巯基苯胺选择性光氧化反应.采用超微电极作为工作电极的原位电化学拉曼光谱技术极大拓展了拉曼光谱技术的研究范围,有望成为探索(光)电化学反应的有力工具.     

FTIR spectroscopy study of the electrochemical reduction of CO2 on various metal electrodes in methanol

The electrochemical reduction of CO₂ on Sn, Cu, Au, In, Ni, Ru and Pt electrodes in methanol containing 0.1 M sodium perchlorate was studied by cyclic voltammetry and in-situ FTIR spectroscopy. Dissolved CO₂ increases the cathodic current at potentials below −1.3 V vs. Ag|0.01 M Ag⁺ with Sn, Au, Cu, In and Ni electrodes. It is concluded from the FTIR spectra obtained that there is no reduction of CO₂ on any of the metals studied, and that the only reaction product detected by Fourier transform (FT) IR spectroscopy, i.e. CO²⁻₃, is formed by reaction of CO₂ with hydroxyl anions produced in the electroreduction of residual water.In order to identify the electroreduction products of CO₂ it was necessary to obtain the FTIR spectra of sodium oxalate and sodium carbonate in methanol. They were obtained by the electroreduction of oxalic acid and the alkalinization of CO₂-saturated methanol respectively. It could be proved that the electroreduction of carboxylic acids to carboxylate anions in organic solvents does not require either a H-chemisorbing metal electrode, or the presence of water in the solvent.     

Determination of enzyme activity inhibition by FTIR spectroscopy on the example of fructose bisphosphatase

A mid-infrared enzymatic assay for label-free monitoring of the enzymatic reaction of fructose-1,6-bisphosphatase with fructose 1,6-bisphosphate has been proposed. The whole procedure was done in an automated way operating in the stopped flow mode by incorporating a temperature-controlled flow cell in a sequential injection manifold. Fourier transform infrared difference spectra were evaluated for kinetic parameters, like the Michaelis–Menten constant (K _M) of the enzyme and V _max of the reaction. The obtained K _M of the reaction was 14 ± 3 g L⁻¹ (41 μM). Furthermore, inhibition by adenosine 5′-monophosphate (AMP) was evaluated, and the K _M^App value was determined to be 12 ± 2 g L⁻¹ (35 μM) for 7.5 and 15 μM AMP, respectively, with V _max decreasing from 0.1 ± 0.03 to 0.05 ± 0.01 g L⁻¹ min⁻¹. Therefore, AMP exerted a non-competitive inhibition.     

In-situ FTIR Spectroelectrochemical Study of Chromium Hexacyanoferrate on Glassy Carbon Electrode

CrHCFisanoveltransition-metalcyanometallatecomPound.Asasortofinorganicpolymer,ithasattractedmuchattention.AwiderangeofaPplicationhasbeenfoundl'2.However,consideringthelimitedstudyoftheCrHCFlGCmodifiedelectrodereportedpreviously',thereisstillmuchtodo.Thisletterreportsanin-situFTIRspectroelectrochemicalinvestigationofCrHCFmodifiedonaglassycarbonelectrode(CrHCF/GC).ItwasfoundthatthestructureofCrHCFwasre1ativelyamorPhous,andthelatticeofCrHCFwasdeformedduringtheelectrochemicalredoxpro…     

固体六氰合铁酸钴微粒在聚电解质中的现场显微红外光谱电化学

报道了六氰合铁酸钴（COHCF）微粒在聚电解质中的光谱电化学及电催化行为．CoHCF的循环伏安呈现一对可逆氧化还原峰，电位扫速在100mV／s范围内，峰电流与扫速成正比．现场红外光谱表明，氧化还原属于CoHCF中的Fe（Ⅱ／Ⅲ）的转化CoHCF微粒可以催化抗坏血酸的氧化，使氧化电位负移，氧化电流增大．根据现场红外光谱推测，催化作用是通过抗坏血酸的烯酸基与CoHCF相互作用实现的．     

固体六氯合铁酸钴微粒在聚电解质中的现场显微红外光谱电化学

报道了六氰合铁酸钴（ＣｏＨＣＦ）微粒在聚电解质中的光谱电化学及电催化行为，ＣｏＨＣＦ的循环伏安呈现一对可逆氧化还原峰，电位扫速在１００ｍＶ／ｓ范围内，峰电流与扫速成正比，现场红外光谱表明，氧化还原属于ＣｏＨＣＦ中的Ｆｅ（Ⅱ／Ⅲ）的转化，ＣｏＨＣＦ微粒可以催化抗坏血酸的氧化，使氧化电位负移，氧化电流增大，根据现场红外光谱推测，催化作用是通过抗坏血酸的烯醇基与ＣｏＨＣＦ相互作用实现的。     

In-Situ Infrared Spectroscopy Applied to the Study of the Electrocatalytic Reduction of CO2: Theory,Practice and Challenges

The field of electrochemical CO₂ conversion is undergoing significant growth in terms of the number of publications and worldwide research groups involved. Despite improvements of the catalytic performance, the complex reaction mechanisms and solution chemistry of CO₂ have resulted in a considerable amount of discrepancies between theoretical and experimental studies. A clear identification of the reaction mechanism and the catalytic sites are of key importance in order to allow for a qualitative breakthrough and, from an experimental perspective, calls for the use of in-situ or operando spectroscopic techniques. In-situ infrared spectroscopy can provide information on the nature of intermediate species and products in real time and, in some cases, with relatively high time resolution. In this contribution, we review key theoretical aspects of infrared reflection spectroscopy, followed by considerations of practical implementation. Finally, recent applications to the electrocatalytic reduction of CO₂ are reviewed, including challenges associated with the detection of reaction intermediates.     

Temperature-resolved derivative FTIR

The fine-structure of the 720/730 cm^-1 doublet of FTIR spectra has been evaluated by derivative spectroscopy as function of temperature on low-density poly(ethylene-co-1-octene). The pseudo-hexagonal mesophase in polyethylene, obtained at atmospheric pressure, is a non-equilibrium phase which develops preferred in presence of short-chain branches. An increasing concentration of short-chain branches slows down the ethylene-sequence selection process which is required for the formation of largely branch/defect-free orthorhombic crystals. Non-isothermal melt-crystallization at sufficiently high rate of temperature-change favors the development of metastable mesomorphic domains which likely form by entrapment of branches. It is proven that the mesophase transforms to the orthorhombic structure exclusively via the liquid phase. This revised version was published online in July 2006 with corrections to the Cover Date.     

Two-dimensional correlation spectroscopy and multivariate curve resolution for the study of lipid oxidation in edible oils monitored by FTIR and FT-Raman spectroscopy

Accelerate oxidative degradation of six vegetable oils was monitored using FTIR and FT-Raman spectroscopy. Two-dimensional correlation spectroscopy and multivariate curve resolution alternating least squares (MCR-ALS) were applied to the analysis of the data. The use of hetero-spectral two-dimensional correlation of FTIR and FT-Raman data allowed the use of well established band assignments to interpret less clearly assigned spectral features. With a moving window approach it was possible to obtain simplified two-dimensional correlation maps and to detect compounds evolving with different kinetic. Simultaneous analysis of the oxidation experiments of the six different oils monitored by both spectroscopic techniques was performed using MCR-ALS. Although a complete resolution of the data was not possible, the spectral changes occurring during the oxidative degradation of the oils were described with a five-component model. The two fundamentally different chemometric approaches lead to coincident results.