微机化紫外可见区现场光谱电化学联用测量系统的研制

本文报道了由微机控制的紫外可见区现场(in situ)光谱电化学联用测量系统的硬件和软件设计。该系统可以测量电化学调制反射光谱,光电流谱和光电容谱,并可实现同一实验体系的同时联合测量,这些功能均由计算机软件完成。该系统已应用于金属、半导体、半导电氧化膜电极/溶液界面行为的研究,得到了一些新的实验结果。     

The reaction mechanism of p-toluenediamine anodic oxidation: an in situ ESR-UV/Vis/NIR spectroelectrochemical study.

In situ ESR-UV/Vis spectroelectrochemistry is applied to obtain new insights into the intermediates and reaction products of the anodic oxidation of p-toluenediamine in aqueous solution at different pH values. A strong pH dependence of the stability of the cation radical is found. While the absence of a stable radical was proved by ESR spectroscopy at pH 2 and 10, this radical is detected at medium pH values and assigned to the semiquinonediimine structure. The UV/Vis absorption of the radical is observed at these pH values as well. The p-toluenediimine intermediate and the trimeric reaction product were followed during the electrode reaction by UV/Vis spectroscopy at all pH values.     

In situ real-time monitoring of epoxy/amine kinetics by remote near infrared spectroscopy

An experimental set-up for in situ real-time monitoring of chemical reactions by remote fiber optic near-infrared spectroscopy was assembled in our laboratory and is described in this communication. A series of epoxy/amine formulations, nonpolymer-forming, and polymerforming alike, were prepared and their reaction kinetics investigated. Accurate and reproducible spectra were generated, the characteristic near-infrared peaks assigned, and the reaction kinetics evaluated by monitoring the rates of disappearance and/or appearance of the characteristic peaks. The effect of the chemical structure and functionality of the components were pointed out and a method suggested to correlate the spectral information with the chemophysical changes in multifunctional formulations.     

In situ Electronic Spectroscopic Techniques far Interfacical Electrochemistry

The present paper cover a measurement system combining reflection spectroscopy photocurrent spectroscopy and photocapacitance spectroscopy, and a measurement system for time resloved reflection and transmission spectroscopy in the ultraviolet-visible spectral region built in suit to characterize electrochemistrical processes. A differential or subtractive spectral method with recpect to an electrode potential change has been adopted in both systems in order to obtain a high S/N ratio.     

In situ UV-Vis and ex situ IR spectroelectrochemical investigations of amorphous and crystalline electrochromic Nb2O5 films in charged/discharged states

Niobium oxide (Nb₂O₅) films and powders have been obtained via the sol-gel route from an NbCl₅ precursor. XRD spectra revealed that films with pseudohexagonal (TT-phase) and orthorhombic (T-phase) structure were formed at 500  °C and 800  °C, respectively, while at 300  °C films were amorphous. Infrared (IR) and Raman spectra of powders and films of Nb₂O₅ in different polymorphic forms were detected, and vibrational band assignments were made. Electrochromic properties of amorphous films and films with the TT-phase were established from in situ ultraviolet visible (UV-Vis) spectroelectrochemical measurements and correlated with ex situ IR transmission spectra of charged films. Ex situ IR spectra revealed that charging of amorphous films is accompanied by variations of the Nb-O stretching mode intensity, while, for films with the TT- and T-phase, splitting of the Nb₃-O stretching modes and the appearance of polaron absorption were noted with Li⁺ ion insertion. Ex situ X-ray diffraction (XRD) spectra of charged films with the TT-phase showed changes of the unit cell dimensions with charging. The influence of the polaron absorption on the ex situ near-grazing incidence angle (NGIA) IR reflection-absorption spectra of charged/discharged films is discussed in detail. Received: 21 August 1997 / Accepted: 9 October 1997     

PETPP／Rh配合物催化剂的原位红光外光谱研究

利用原位红外光谱,考察了PETPP/Rh催化剂在CO/H2气氛下的活化情况,并监测1-十二碳烯氢甲酰化的反应过程。实验结果表明,在PETPP/Rh配合物催化剂中,膦配体主要以配位数少的形式存在,因而氢甲酰化反应产物醛的正/异比较低。     

In situ determination of organic compounds in liquid samples using a combined UV-Vis/fluorescence submersible sensor

In order to improve the in situ evaluation and quantitative analysis of complex contaminations of liquid media such as ground-, surface, and wastewaters, an integrated submersible sensor probe has been developed. It is especially characterized by the option of simultaneously measuring ultraviolet/visible (UV/Vis) and fluorescence spectra. Owing to the compact construction with light sources, flow cell, detection system, and data acquisition/processing unit in the waterproof case, the data transfer to the surface can be realized electrically, and the operation depth is practically not limited. The variability in the measuring techniques allows a wide variety of chemical compounds to be analysed within a broad concentration range. The performance of the new submersible sensor probe was tested ex situ in laboratory scale, and the performance was comparable with that of stationary measuring instruments. As an example for an in situ application, the sensor probe was successfully used to monitor the migration of chemical substances during a tracer experiment in groundwater. The concentration of the tracer compound uranin (sodium fluorescein) was measured in the range of 5–500 µg L^?1 using fluorescence spectroscopy, while at the same time the contents of toluene were continuously detected in the same groundwater wells using the UV/Vis sensor channel.     

In situ/operando X-ray spectroscopy applied to electrocatalytic CO2 reduction: Status and perspectives

X-ray spectroscopy is a powerful tool to understand the electronic and local structure of electrocatalysts under operating conditions. Although catalysis itself is performed by electroactive species, other, non-electroactive ones play a critical role in electrocatalytic reactions as well. Cations, anions, solvents or reactants all have significant effects in the efficiency of electrocatalytic reactions. Focusing on the electrochemical reduction of carbon dioxide, we give a short summary of the current status of the in situ/operando X-ray spectroscopy experiments performed on electroactive species, as well as a perspective on the techniques and setups that could be used to probe non-electroactive ones.     

In situ Raman spectroelectrochemistry of azobenzene monolayers on glassy carbon

In situ Raman spectra of chemisorbed azobenzene (AB) monolayers on glassy carbon (GC) electrodes were observed under potentiostatic conditions in acetonitrile (ACN) with tetrabutyl-ammonium tetrafluoroborate (TBA-BF₄). The Raman intensities of these spectra were high below −1000 mV, and this is attributed to the change in absorbance of AB on GC. In this paper, we describe chemisorbed AB molecules on GC electrode surfaces under potentiostatic conditions.     

In situ Second-Harmonic Generation Circular Dichroism with Submonolayer Sensitivity

In this work, we present an experimental setup for the in situ and ex situ study of the optical activity of samples, which can be prepared under ultra-high vacuum (UHV) conditions by second-harmonic generation circular dichroism (SHG-CD) over a broad spectral range. The use of a racemic mixture as a qualified reference for the anisotropy factor is described and, as an example, the chiroptical properties of 1.5 μm thick (multilayers) as well as sub-monolayer thin films of the R- and S-enantiomer of 1,1′-Bi-2-naphthol (BINOL) evaporated onto BK7 substrates were investigated.     

Ionic Liquid for in situ Vis/NIR and Raman Spectroelectrochemistry: Doping of Carbon Nanostructures

1-butyl-3-methylimidazolium tetrafluoroborate (an ionic liquid) is an advantageous electrolyte for the study of charge-transfer reactions at single-walled carbon nanotubes (SWCNTs) and fullerene peapods (C₆₀@SWCNT). Compared to traditional electrolyte solutions, this medium offers a broader window of electrochemical potentials to be applied, and favorable optical properties for in situ Vis/NIR and Raman spectroelectrochemistry of nano-carbon species. The electrochemistry of both nanotubes and peapods is dominated by their capacitive double-layer charging. Vis/NIR spectroelectrochemistry confirms the charging-induced bleaching of transitions between Van Hove singularities. At high positive potentials, new optical transitions were activated in partly filled valence band. The bleaching of optical transitions is mirrored by the quenching of resonance Raman scattering in the region of tube-related modes. The Raman frequency of the tangential displacement mode of SWCNT shifts to blue upon both anodic and cathodic charging in the ionic liquid. The Raman modes of intratubular C₆₀ exhibit a considerable intensity increase upon anodic doping of peapods.     

A combination of in situ ESR and in situ NMR spectroelectrochemistry for mechanistic studies of electrode reactions: the case of p-benzoquinone

A combined in situ NMR and in situ ESR spectroelectrochemical study of a reaction mechanism is presented detecting and describing the whole number of paramagnetic and diamagnetic intermediates and final products in an electrode reaction. While in situ NMR spectroelectrochemistry provides a powerful method for the study of structural or electronic changes of diamagnetic molecules in any electrochemical reaction mechanism, in situ ESR spectroelectrochemistry is the method of choice to detect paramagnetic structures and to characterise their electronic state via the g-value and hyperfine splitting in redox reactions. To demonstrate the power of this combination of magnetic spectroscopies in electrochemistry, the reduction of p-benzoquinone to hydroquinone is followed by both these spectroelectrochemical methods at selected pH values, thus considering the influence of the proton on the reaction mechanism. The results of both in situ spectroelectrochemical methods at the same redox system are used to get the complete reaction mechanism of p-benzoquinone at electrodes in aqueous solutions.     

Characterization and electrical properties of polypyrrole/multiwalled carbon nanotube composites synthesized by in situ chemical oxidative polymerization

This study describes the preparation of polypyrrole (PPy)/multiwalled carbon nanotube (MWNT) composites by in situ chemical oxidative polymerization. Various ratios of MWNTs, which served as hard templates, were first dispersed in aqueous solutions with the surfactant cetyltrimethylammonium bromide to form micelle/MWNT templates and overcome the difficulty of MWNTs dispersing into insoluble solutions of pyrrole monomer, and PPy was then synthesized via in situ chemical oxidative polymerization on the surface of the templates. Raman spectroscopy, Fourier transform infrared (FTIR), field‐emission scanning electron microscopy (FESEM), and high‐resolution transmission electron microscopy (HRTEM) were used to characterize the structure and morphology of the fabricated composites. Structural analysis using FESEM and HRTEM showed that the PPy/MWNT composites were core (MWNT)–shell (PPy) tubular structures. Raman and FTIR spectra of the composites were almost identical to those of PPy, supporting the idea that MWNTs served as the core in the formation of a coaxial nanostructure for the composites. The conductivities of these PPy/MWNT composites were about 150% higher than those of PPy without MWNTs. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 1413–1418, 2006     

Photo‐Rheometry/NIR Spectrometry: An in situ Technique for Monitoring Conversion and Viscoelastic Properties during Photopolymerization

Summary: A suitable rheometer for simultaneous dynamic mechanical analysis (DMA) and NIR (Near Infra‐Red) in situ analysis during UV curing was developed. The conversion and viscoelastic properties of a dimethacrylate/styrene‐based system were investigated. The results were plotted against both irradiation time and total average conversion. For the same conversion, a lower intensity delays the reaction but does not affect the viscoelastic properties.

A device for simultaneous photo‐rheology and NIR spectroscopy experiments.