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Electrolyte effects on formation and properties of PEDOT-graphene oxide composites
摘要： This work presents a comparative electrochemical and spectroelectrochemical study of composites consisting of poly(3,4-ethylenedioxythiophene) (PEDOT) and graphene oxide (GO) synthesized in different electrolyte solutions. The electrochemical behavior of PEDOT/GO composites were studied in an ionic liquid (1-butyl-3-methylimidazolium tetrafluoroborate) as well as in conventional organic (acetonitrile) and aqueous electrolytes by cyclic voltammetry and electrochemical impedance spectroscopy. Additionally, we applied in situ Attenuated Total Reflection Fourier Transformed Infrared (ATR–FTIR) spectroelectrochemistry using a Kretschmann geometry cell to study the composite fabrication during potentiodynamic electropolymerization, and to study the electronic properties and charge carrier formation during p-doping. According to in situ ATR-FTIR analysis, the doping induced bands from charge carrier formation begin to grow at lower potentials for the composite film and the electronic absorptions indicate formation of only one type of charge carrier in the composite made and characterized in ionic liquid. The optical properties during doping were determined by in situ UV–Vis spectroelectrochemistry. The composite film fabricated in water has its absorbance maximum at slightly higher wavelengths, and the appearance of the film is changed from well-known light blue color of PEDOT to greyish.
关键词： spectroelectrochemistry,PEDOT,composite,graphene oxide,electrolyte
更新于2025-11-19 16:56:35
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Spectroelectrochemical operando method for monitoring a phenothiazine electrografting process on amide functionalized C-nanodots/Au hybrid electrodes
摘要： Phenothiazine derivatives are extensively explored dye molecules, which present interesting electrochemical and optical properties. In recent years, the possibility of transforming some phenothiazines in their aryl diazonium salt derivatives has been proved, what allows them to be electrochemically reduced and electrografted onto conductive surfaces. This is a smart way to modify these surfaces and enable them with specific functionalities. In order to better comprehend the electrografting process and consequently have a higher control of it, in this work we have carried out an exhaustive study by operando UV–Vis spectroelectrochemistry of the electrografting of a phenothiazine aryl diazonium salt onto amide carbon nanodots. As a model of phenothiazine dye we have chosen Azure A. The electrografting onto carbon nanodots has been stablished by comparison with the results obtained on bare gold electrodes in this novel study. The presence of carbon dots improves the reversibility of the electrochemical process as derived from the results obtained by operando UV–Vis spectroelectrochemistry. In addition, to asses that the electrochemical process studied corresponds to the electrografting, the results have been compared to those obtained for the simple Azure A adsorption. This study shows the advantages of obtaining simultaneously the electrochemical and the spectroscopic evolution of an electron-transfer process in a single experiment, in a particular electrochemical reaction. This work could be the starting point for the study of the electrografting on other nanomaterials.
关键词： Azure A,Electrografting,Diazonium salt,Carbon nanodots,Spectroelectrochemistry
更新于2025-09-23 15:22:29
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Microsecond Resolved Infrared Spectroelectrochemistry Using Dual Frequency Comb IR Lasers
摘要： A dual infrared frequency comb spectrometer with heterodyne detection has been used to perform time resolved electrochemical attenuated total reflectance surface enhanced infrared absorption spectroscopy (ATR-SEIRAS). The measurement of the potential dependent desorption of a monolayer of a pyridine derivative (4-dimethylaminopyridine, DMAP) with time resolution as high as 4 μs was achieved without the use of step-scan interferometry. An analysis of the detection limit of the method as a function of both time resolution and measurement co-additions is provided and compared to step-scan experiments of an equivalent system. Dual frequency comb spectroscopy is shown to be highly amenable to time-resolved ATR-SEIRAS. Microsecond resolved spectra can be obtained with high spectral resolution and fractional monolayer detection limits in a total experimental duration that is two orders of magnitude less than the equivalent step-scan experiment.
关键词： 4-dimethyamino pyridine (DMAP),noise analysis,Dual frequency comb spectroscopy,time resolved spectroelectrochemistry,RC constant,attenuated total reflectance surface enhanced infrared absorption spectroscopy (ATR-SEIRAS),detection limit
更新于2025-09-19 17:13:59
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Electronic properties of oxidized cyclometalated diiridium complexes: Spin delocalization controlled by the mutual position of the iridium centres
摘要： Four cyclometalated diiridium complexes, with IrCp*Cl (Cp* = η5-C5Me5?) termini bridged by 1,4- and 1,3-bis(p-tolylimino-ethyl)benzene (1, 2), or 1,4- and 1,3-bis(2-pyridyl)benzene (3, 4), were prepared and characterized by nuclear magnetic resonance (NMR) spectroscopy and single-crystal X-ray diffraction (complexes 1, 2 and 4). The two iridium centres in complexes 1 and 3 are thus bound at the central benzene ring in the para-position (trans-Ir2), while those in complexes 2 and 4 in the meta-position (cis-Ir2). Cyclic voltammograms of all four complexes show two consecutive one-electron oxidations. The potential difference between the two anodic steps in 1 and 3 is distinctly larger compared to 2 and 4. The visible - near-infrared (NIR) - short-wave infrared (SWIR) absorption spectra of trans-Ir2 monocations 1+ and 3+ are markedly different from those of cis-Ir2 monocations 2+ and 4+. Notably, strong near-infrared electronic absorption appears only in the spectra of 1+ and 3+ while 2+ and 4+ absorb only weakly in the NIR-SWIR region. Combined DFT and TD-DFT calculations have revealed that (a) 1+ and 3+ (the diiridium-benzene trans-isomers) display HOSO and LUSO evenly delocalized over both molecule halves, and (b) their electronic absorptions in the NIR-SWIR region are attributed to mixed metal-to-ligand and ligand-to-ligand charge transfers (MLCT and LLCT). In contrast, cis-isomers 2+ and 4+ do not feature this stabilizing π-delocalization but a localized mixed-valence state showing a weak IVCT absorption in the SWIR region.
关键词： Mixed-valence State,Cyclometalated Isomers,Cyclic Voltammetry,Diiridium Complex,Spectroelectrochemistry
更新于2025-09-12 10:27:22
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Coherent Vibrational Spectroscopy of Electrochemical Interfaces with Plasmonic Nano-gratings
摘要： The fundamental understanding of electrochemistry urges accurate knowledge of all interfacial properties at the molecular-level, but the retrieval of such information is a real challenge. Optical spectroscopies facilitated by surface plasmon enhancement can shed light on this field, yet past studies relied on either highly inhomogeneous “hot spots”, or planar plasmon modes with limited enhancement. Here we report an in situ sum-frequency vibrational spectroscopy scheme using plasmonic nano-gratings, which enable strong, coherent surface plasmon excitation even on planar electrodes. With two classical reactions, the gold oxidation and pyridine adsorption in water, we demonstrate the realization of coherent vibrational spectroscopy in the strong absorption region, revealing the polar orientation and ordering of interfacial species that are crucial toward the mechanistic understanding of electrochemical phenomena.
关键词： field enhancement,surface plasmon resonance,molecular-level information,in situ spectroelectrochemistry,electrode/electrolyte interfaces
更新于2025-09-12 10:27:22
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Electrochemistry of zinc tetraarylporphyrins containing fused butano and benzo groups. Effect of solvent and substituents on spectra, potentials and mechanism in nonaqueous media
摘要： Two series of zinc tetraarylporphyrins containing four b,b′-pyrrole fused butano or benzo groups were synthesized and characterized as to their electrochemical and spectroelectrochemical properties in nonaqueous media. The examined compounds are represented as butano(Ar)4PorZn and benzo(Ar)4PorZn, where Por is the porphyrin dianion and Ar is a p-CH3Ph, Ph or p-ClPh substitutent on meso-positions of the macrocycle. Each Zn(II) butano- and benzoporphyrin undergoes two one-electron reductions to give a p-anion radical and dianion in CH2Cl2. In contrast, three reductions were observed for the benzoporphyrin derivatives in pyridine, the third of which is assigned as electron addition to a benzophlorin anion generated from the doubly reduced benzoporphyrin. Two overlapped one-electron oxidations were observed for the butanoporphyrins in CH2Cl2, a result not previously observed for any other zinc porphyrin. The electrochemically measured HOMO–LUMO gap of the benzoporphyrins ranges from 1.89 to 1.90 V in CH2Cl2 and from 1.93 to 1.95 V in pyridine. Both values are smaller than the gaps of butanoporphyrins at 2.11–2.13 V in CH2Cl2 and 2.07–2.09 V in pyridine.
关键词： spectroelectrochemistry,electrochemistry,substituent effect,synthesis,porphyrinoids
更新于2025-09-10 09:29:36
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Application of spectroelectroanalysis for the quantitative determination of mixtures of compounds with highly overlapping signals
摘要： The amount of qualitative and quantitative information provided by a UV?vis absorption spectroelectrochemistry (SEC) experiment is sometimes wasted. However, almost all electrochemical and spectroscopic data can provide valuable information. In this spirit, the main objective proposed in this work is the quantitative resolution of catechol/dopamine (CAT/DA) and dopamine/epinephrine (DA/EP) mixtures, using spectroelectrochemical sensors in long optical path length arrangement based on bare optical fibers in parallel configuration with respect to carbon nanotubes or screen-printed electrodes. These compounds show extremely similar electrochemical and spectroscopic responses at high acidic pH, being impossible to determine their concentrations in the mixtures just using univariate regression models. To our knowledge, the SEC ability to resolve complex mixtures has never been demonstrated before with signals with this degree of overlapping. The quantitative analysis of these mixtures is possible using multivariate regression analysis of a set of time-resolved spectroelectrochemical data with a powerful statistical tool such as parallel factor analysis (PARAFAC). PARAFAC enables us to extract all the information from the experiments, allowing us to quantify the different analytes in mixtures of varying concentrations with excellent results. This milestone for spectroelectroanalysis illustrates the expected capabilities of SEC and demonstrates experimentally the potential of this technique for sensing of biomolecules.
关键词： screen-printed electrodes,dopamine,optical fibers,epinephrine,carbon nanotubes,spectroelectrochemistry
更新于2025-09-10 09:29:36
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INVESTIGATION OF rGO AND CHITOSAN EFFECTS ON OPTICAL AND ELECTRICAL PROPERTIES OF THE CONDUCTIVE POLYMERS FOR ADVANCED APPLICATIONS
摘要： A simple and fast method for preparing chitosan (CH)/conducting polymer (CP) composite film with and without reduced graphene oxide (rGO) was realized to investigate the effect of rGO on an optoelectrochemical system. For this purpose, firstly rGO was successfully dispersed in the acidic aqueous solution of CH by ultrasonic agitation. One by one CH and CH/rGO blend deposited on an indium tin-oxide (ITO) coated glass electrode by drop-casting method. After that, N1,N4-bis(2,5-di(thiophen-2-yl)-1H-pyrrol-1-yl)terephthalamide (m(BT)) electroactive monomer was deposited onto CH and CH/rGO modified ITO electrode surfaces via electrochemical polymerization. Electrochemical and optical properties of the composite structures were investigated by cyclic voltammetry (CV) technique and UV-vis spectroscopy. The surface characterizations of nanocomposites have been performed by scanning electron microscopy. It was observed that, chemical functionalities of CH, rGO and p(BT) provide excellent compatibility. Therefore, the CH/rGO/p(BT) electroactive nanocomposite has better conductivity, stability, charge density, electrochromic switching kinetics and electrochemical properties than the CH/p(BT) and p(BT)/rGO composites. This is due to more efficient synergistic effect between CH, rGO and p(BT) which provide larger active surface area and ease ion transport. This method for producing composite films with novel optical, electrical and stability properties has been gaining a new perspective in the material world, which enables smart and advanced material design in various practical applications especially for designing molecular detection systems.
关键词： conducting polymer,rGO,spectroelectrochemistry,chitosan
更新于2025-09-09 09:28:46
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Xanthommatin-Based Electrochromic Displays Inspired by Nature
摘要： Color is a signature visual feature in nature; however, the ability to trigger color change in the presence of different environmental stimuli is unique to only a handful of species in the animal kingdom. We exploit the natural color-changing properties of arthropods and cephalopods—xanthommatin (Xa)—and describe its utility as a new broad-spectrum electrochromic material. To accomplish this goal, we explored the spectroelectrochemical properties of Xa adsorbed to an indium-doped tin oxide-coated substrate chemically modified with poly(3,4-ethylene dioxythiophene) doped with poly(styrenesulfonate) (PEDOT:PSS). We identified a synergistic role between PEDOT:PSS and Xa that contributed to its absorption profile, which could be modulated across multiple cycles. By varying the ratio of the two electroactive components, we also altered the perceived visible color of Xa-based devices, which cycled from different shades of red to yellow under reducing and oxidizing potentials, respectively. Together, our data illustrate the utility of Xa-based devices as new broad-spectrum electrochromic materials.
关键词： redox,poly(3,4-ethylene dioxythiophene)?poly(styrenesulfonate),xanthommatin,spectroelectrochemistry,electrochromic device
更新于2025-09-09 09:28:46
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Effect of Chloride and pH on the Electrochemical Surface Oxidation Enhanced Raman Scattering
摘要： In the present work, electrochemical surface oxidation enhanced Raman scattering (EC-SOERS) was studied using time resolved Raman spectroelectrochemistry. This multiresponse technique allows us to obtain dynamic information about the processes taking place during the electrochemical oxidation of a silver substrate. EC-SOERS is particularly found in specific electrolytic conditions, namely, HClO4 0.1 M + KCl 5·10-3 M, and has a clear dependence on chloride concentration and pH, being the optimum values between 5·10-3 M and 1·10-2 M for chloride and pH = 1. In light of the results of this study, the appearance of the phenomenon is related to the modification of the electrode surface, yielding Ag/AgCl cubes as plasmonic structures, and the stability of such structures at low pH values. The results presented in this work could shed more light into the intricate EC-SOERS phenomenon which can be summarized as the increase of the Raman signal for a Raman probe molecule exclusively during the electrochemical oxidation of silver electrodes.
关键词： Silver,Raman enhancement,nanostructures,spectroelectrochemistry
更新于2025-09-04 15:30:14