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Electrochromism in Electropolymerized Films of Pyrene-Triphenylamine Derivatives
摘要： Two star-shaped multi-triphenylamine derivatives 1 and 2 were prepared, where 2 has an additional phenyl unit between a pyrene core and surrounding triphenylamine units. The oxidative electropolymerization of 1 and 2 occurred smoothly to give thin films of polymers P1 and P2. The electrochemistry and spectroelectrochemistry of P1 and P2 were examined, showing two-step absorption spectral changes in the near-infrared region. The electrochromic properties, including contrast ratio, response time, and cyclic stability of P1 and P2 were investigated and compared. Thin film of P2 displays slightly better electrochromic performance than P1, with a contrast ratio of 45% at 1475 nm being achieved.
关键词： triphenylamine,near-infrared,electrochemistry,electrochromism,electropolymerization
更新于2025-09-23 15:22:29
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Nanoporous water oxidation electrodes with a low loading of laser-deposited Ru/C exhibit enhanced corrosion stability
摘要： For the oxidation of water to dioxygen, oxide-covered ruthenium metal is known as the most efficient catalyst, however, with limited stability. Herein, we present a strategy for incorporating a Ru/C composite onto a novel nanoporous electrode surface with low noble metal loading and improved stability. The Ru/C is coated on the pore walls of anodic alumina templates in a one-step laser-induced deposition method from Ru3(CO)12 solutions. Scanning electron microscopy proves the presence of a continuous Ru/C layer along the inner pore walls. The amorphous material consists of metallic Ru incorporated in a carbonaceous C matrix as shown by X-ray diffraction combined with Raman and X-ray photoelectron spectroscopies. These porous electrodes reveal enhanced stability during water oxidation as compared to planar samples at pH 4. Finally, their electrocatalytic performance depends on the geometric parameters and is optimized with 13 μm pore length, which yields 2.6 mA cm?2, or 49 A g?1, at η = 0.20 V.
关键词： ruthenium catalyst,nanostructures,water splitting,electrochemistry,noble metals
更新于2025-09-23 15:22:29
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Synthesis, Photophysical and Electrochemical Studies on Peripherally Ruthenated Tetraphenylporphyrin
摘要： Ruthenium(II) complexes of 5-(4-hydroxyphenyl)-10,15,20-tris-(4-methylphenyl)porphyrin and 5,10,15,20-tetrakis(4-hydroxyphenyl)-porphyrin have been synthesized in basic medium and spectroscopically characterized. The complexes show broad bands in the visible region due to overlap of porphyrin transitions with the metal-to-ligand charge transfer (MLCT) transitions arising from cis-Ru(bipy)2Cl2. 1H NMR indicates π-electron interactions between the porphyrin ring and bipyridyl rings. The complexes are emissive both at room temperature and at 77 K with two independent emissions at 77 K, one from the excited state of the porphyrin moiety at 650 and 720 nm and the other from the excited state of the ruthenium moiety at 700 nm. No excited state intramolecular energy transfer reactions have been detected. However the quantum yield of the complexes is reduced due to heavy atom effect. Time resolved fluorescence decay analyses show dual life time at 1.5 and 7.7 ns in dichloromethane. The shorter life time is assigned to singlet-excited state of ruthenium and longer life time to porphyrin singlet excited state. Electrochemical analysis of these species in dichloromethane exhibits three anodic peaks at around 0.68, 0.98 and 1.42 V versus SCE, analogous to the Ru3+/2+ couple and two successive one-electron oxidation processes on the porphyrin ring, respectively. On the other hand, cathodic potentials at around -0.8, -1.4 and -1.54 V versus SCE, with first two peaks corresponding to two successive reduction taking place at the porphyrin ring and the third peak corresponding to reduction of bipyridyl unit. All spectroscopic studies reveal perturbation on the electronic levels of both porphyrin ring and ruthenium chromophore.
关键词： Porphyrin,Ruthenated,Life time,Perturbation,Emission,Electrochemistry
更新于2025-09-23 15:22:29
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Significant Enhancement of Hole Transport Ability in Conjugated Polymer/Fullerene Bulk Heterojunction Microspheres
摘要： Bulk heterojunction (BHJ) strategy requires morphology of wide area donor-acceptor interfaces with high charge carrier mobilities through the bicontinuous charge transporting layers. Here, we report formation of well-defined bulk heterojunction (BHJ) microspheres from regiorandom poly(hexylthiophene) (rra-PHT)/phenyl-C61-butyric acid methyl ester (PCBM) mixture by a vapor diffusion method. By electrochemical oxidation, the BHJ microsphere exhibits enhanced generation of PHT cation species due to increased hole-transport property in comparison with a solution-cast film derived from rra-PHT/PCBM mixture without microsphere morphology. Photoconductivity and electrochemical stability of the microsphere are comparable or even higher than a cast film of irregular aggregates of regioregular P3HT.
关键词： polythiophene,bulk heterojunction,microspheres,electrochemistry,fullerene
更新于2025-09-23 15:22:29
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Resonance Raman Spectro-Electrochemistry to Illuminate Photo-Induced Molecular Reaction Pathways
摘要： Electron transfer reactions play a key role for artificial solar energy conversion, however, the underlying reaction mechanisms and the interplay with the molecular structure are still poorly understood due to the complexity of the reaction pathways and ultrafast timescales. In order to investigate such light-induced reaction pathways, a new spectroscopic tool has been applied, which combines UV-vis and resonance Raman spectroscopy at multiple excitation wavelengths with electrochemistry in a thin-layer electrochemical cell to study [RuII(tbtpy)2]2+ (tbtpy = tri-tert-butyl-2,2′:6′,2′′-terpyridine) as a model compound for the photo-activated electron donor in structurally related molecular and supramolecular assemblies. The new spectroscopic method substantiates previous suggestions regarding the reduction mechanism of this complex by localizing photo-electrons and identifying structural changes of metastable intermediates along the reaction cascade. This has been realized by monitoring selective enhancement of Raman-active vibrations associated with structural changes upon electronic absorption when tuning the excitation wavelength into new UV-vis absorption bands of intermediate structures. Additional interpretation of shifts in Raman band positions upon reduction with the help of quantum chemical calculations provides a consistent picture of the sequential reduction of the individual terpyridine ligands, i.e., the first reduction results in the monocation [(tbtpy)Ru(tbtpy?)]+, while the second reduction generates [(tbtpy?)Ru(tbtpy?)]0 of triplet multiplicity. Therefore, the combination of this versatile spectro-electrochemical tool allows us to deepen the fundamental understanding of light-induced charge transfer processes in more relevant and complex systems.
关键词： ruthenium bis-terpyridine complex,resonance Raman,in situ spectro-electrochemistry,TDDFT,UV-vis
更新于2025-09-23 15:22:29
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Oxidative and reductive cyclization in stiff dithienylethenes
摘要： The electrochemical behavior of stiff dithienylethenes, undergoing double bond isomerization in addition to ring-closure, has been investigated. Electrochromism was observed in almost all cases, with the major pathway being the oxidatively induced cyclization of the open isomers. The influence of the ring size (to lock the reactive antiparallel conformation) as well as substituents (to modulate the redox potential) on the electrocyclization was examined. In the series of derivatives with 6-membered rings, both the E- and the Z-isomer convert to the closed isomer, whereas for the 7-membered rings no cyclization from the E-isomer was observed. For both stiff and normal dithienylethenes bearing benzonitrile substituents an additional and rare reductive electrocyclization was observed. The mechanism underlying both observed electrocyclization pathways has been elucidated.
关键词： (spectro)electrochemistry,electrochromism,molecular switches,diarylethenes
更新于2025-09-23 15:22:29
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Thermal, spectroscopic, electrochemical, and electroluminescent characterization of malononitrile derivatives with triphenylamine structure
摘要： Three push-pull molecules with linear, quadrupolar and tripodal arrangements, consisting of triphenylamine (electro-donor) substituted with malononitrile groups (electro-acceptor), were synthesized with high yield by a simple procedure. Impact of the number of malononitrile substituents on optoelectronic properties was investigated with cyclic voltammetry, absorption and emission spectroscopy, as well as density functional theory calculation. The derivatives formed amorphous materials and exhibited low energy band gaps ranging from 2.06 to 2.49 eV. UV–Vis absorption and photoluminescence emission spectra were investigated in solutions (CHCl3, NMP) and in solid-state as thin films and two kinds of blends (with PMMA and PVK:PBD). Quantum yield of photoluminescence was dependent on the molecule structure, solvent, and solid-state layer formulation. The compounds exhibited high photoluminescence quantum yield in the range of 15–42% and 12–59% in solid-state as film and blend with PMMA (1 wt%), respectively, being promising for applications in light emitting diodes. The diodes with active layer consisting of neat derivatives and compounds molecularly dispersed in PVK:PBD (50:50 wt%) matrix showed orange and green electroluminescence.
关键词： Triphenylamine,Photoluminescence,Electrochemistry,Malononitrile,Electroluminescence
更新于2025-09-23 15:21:21
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Electrochemistry of Atomically Precise Metal Nanoclusters
摘要： Thiolate-protected metal nanoparticles containing a few to few hundred metal atoms are interesting materials exhibiting unique physicochemical properties. They encompass the bulk-to-molecule transition region, where discrete electronic states emerge and electronic band energetics yield to quantum con?nement e?ects. Recent progresses in the synthesis and characterization of ultrasmall gold nanoparticles have opened up new avenues for the isolation of extremely monodispersed nanoparticles with atomically precision. These nanoparticles are also called nanoclusters to distinguish them from other regular metal nanoparticles with core diameter >2 nm. These nanoclusters are typically identi?ed by their actual molecular formulas; prominent among these are Au25(SR)18, Au38(SR)24, and Au102(SR)44, where SR is organothiolate. A number of single crystal structures of these nanoclusters have been disclosed. Researchers have e?ectively utilized density functional theory (DFT) calculations to predict their atomic and electronic structures, as well as their physicochemical properties. The atomically precise metal nanoclusters have been the focus of recent studies owing to their novel size-speci?c electrochemical, optical, and catalytic properties. In this Account, we highlight recent advances in electrochemistry of atomically precise metal nanoclusters and their applications in electrocatalysis and electrochemical sensing. Compared with gold nanoclusters, much less progress has been made in the electrochemical studies of other metal nanoclusters, and thus, we mainly focus on the electrochemistry and electrochemical applications of gold-based nanoclusters. Voltammetry has been extremely powerful in investigating the electronic structure of metal nanoclusters, especially near HOMO and LUMO levels. A sizable opening of HOMO?LUMO gap observed for Au25(SR)18 gradually decreases with increasing nanocluster size, which is in line with the change in the optical gap. Heteroatom-doping has been a powerful strategy to modify the optical and electrochemical properties of metal nanoclusters at the atomic level. While the superatom theory predicts 8-electron con?guration for [Au25(SR)18]? and many doped nanoclusters thereof, Pt- and Pd-doped [PtAu24(SR)18]0 and [PdAu24(SR)18]0 nanoclusters show dramatically di?erent electronic structures, as manifested in their optical spectra and voltammograms, suggesting the occurrence of the Jahn?Teller distortion in these doped nanoclusters. Furthermore, metal-doping may alter their surface binding properties, as well as redox potentials. Metal nanoclusters o?er great potential for attaining high activity and selectivity in their electrocatalytic applications. The well-de?ned core?shell structure of a metal nanocluster is of special advantage because the core and shell can be independently engineered to exhibit suitable binding properties and redox potentials. We discuss recent progress made in electrocatalysis based upon metal nanoclusters tailored for water splitting, CO2 conversion, and electrochemical sensing. A well-de?ned model nanocatalyst is absolutely necessary to reveal the detailed mechanism of electrocatalysis and thereby to lead to the development of a new e?cient electrocatalyst. We envision that atomically controlled metal nanoclusters will enable us to systematically optimize the electrochemical and surface properties suitable for electrocatalysis, thus providing a powerful platform for the discovery of ?nely tuned nanocatalysts.
关键词： quantum con?nement,electrocatalysis,atomically precise metal nanoclusters,electrochemistry,electrochemical sensing
更新于2025-09-23 15:21:21
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The impact of replacement of nitrogen with phosphorus atom in the pyromellitic diimides on their photophysical and electrochemical properties
摘要： Exploration of optoelectronic properties of novel phosphorus-embedded π-conjugated compounds would provide us with fundamental information about the design of hitherto unknown electroactive organic materials. Herein, detailed photophysical and electrochemical profiles of a series of benzene-cored diketophosphanyl compounds were investigated with steady- and time-resolved spectroscopic and spectroelectrochemical techniques. The comparative studies revealed the impact of phosphorus and nitrogen atoms on their triplet energies and on the behaviour of electrochemical processes to form radical species.
关键词： photophysics,phosphorus heterocycles,π-conjugated compounds,radical,electrochemistry
更新于2025-09-23 15:21:21
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The Reaction Mechanism for the Hydrogen Evolution Reaction on the Basal Plane Sulfur Vacancy Site of MoS2 Using Grand Canonical Potential Kinetics
摘要： We develop the grand canonical potential kinetics (GCP-K) formulation based on thermodynamics from quantum mechanics calculations to provide a fundamental basis for understanding heterogeneous electrochemical reactions. Our GCP-K formulation arises naturally from minimizing the free energy using a Legendre transform relating the net charge of the system and the applied voltage. Performing this macroscopic transformation explicitly allows us to make the connection of GCP-K to the traditional Butler-Volmer kinetics. Using this GCP-K based free energy, we show how to predict both the potential and pH dependent chemistry for a specific example, the hydrogen evolution reaction (HER) at a sulfur vacancy on the basal plane of MoS2. We find that the rate determining steps in both acidic and basic conditions are the Volmer reaction in which the second hydrogen atom is adsorbed from the solution. Using the our GCP-K formulation, we show that the stretched bond distances change continuously as a function of the applied potential. This shows that the main reason for the higher activity in basic conditions is that the transition state is closer to the product, which leads to a more favorable Tafel slope of 60mV/dec. In contrast if the transition state were closer to the reactant, where the transfer coefficient is less than 0.5 we would obtain a Tafel slope of almost 150mV/dec. Based on this detailed understanding of the reaction mechanism, we conclude that the second hydrogen at the chalcogenide vacant site is the most active towards the hydrogen evolution reaction. Using this as a descriptor, we compare to the other 2H group VI metal dichalcogenides and predict that vacancies on MoTe2 will have the best performance towards HER.
关键词： Grand Canonical Potential,Hydrogen Evolution Reaction,Molybdenum Disulfide,Electrochemistry
更新于2025-09-23 15:21:21