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Charge Transfer Complex of Thioxanthonephenacyl Sulfonium Salt as Visible Light Photoinitiator for Free Radical and Cationic Polymerizations.
摘要： A new double chromophoric sulfonium salt photoinitiator possessing both thioxanthone and phenacyl groups, namely 2-isopropylthioxanthonium phenacyl hexafluoroantimonate (ITXPhenS) was synthesized and characterized. ITXPhenS can form charge transfer complex (CTC) with the donor N, N-dimethyl aniline (DMA) with absorption characteristics in the visible range as confirmed by spectral analysis, cyclic voltammetry (CV) and density functional theory (DFT). The extension of the absorbance shift can be controlled by the ITXPhenS to DMA ratio. The ability of the CTC to initiate free radical and cationic polymerization reactions of various monomers under visible and natural sunlight is demonstrated. The proposed mechanism assumes the generation of radical and ionic species by the heterolytic and/or homolytic cleavage of ITXPhenS within the CTC followed by electron transfer reactions.
关键词： photochemistry,density functional calculations,cyclic voltammetry,polymerization,charge transfer
更新于2025-09-23 15:21:01
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Effect of Size, Coverage, and Dispersity on the Potential-Controlled Ostwald Ripening of Metal Nanoparticles
摘要： Here we describe the size-dependent, electrochemically-controlled Ostwald ripening of 1.6, 4 and 15 nm diameter Au nanoparticles (NPs) attached to (3-aminopropyl)triethoxysilane (APTES)-modified glass/Indium tin oxide (glass/ITO) electrodes. Holding the Au NP-coated electrodes at a constant potential negative of the dissolution potential in bromide-containing electrolyte led to electrochemical Ostwald ripening of the different-sized Au NPs. The relative increase in the diameter of the NPs (Dfinal/Dinitial) during electrochemical Ostwald ripening increases with decreasing NP size, increasing applied potential, increasing NP population size dispersity, and increasing NP coverage on the electrodes. Monitoring the average size of the Au NPs as a function of time at a controlled potential allows the measurement of the Ostwald ripening rate. Anodic stripping voltammetry (ASV) and electrochemical determination of the surface area-to-volume ratio (SA/V) provides fast and convenient size analysis for the many different samples and conditions, with consistent sizes from scanning electron microscopy (SEM) images for some samples. It is important to better understand electrochemical Ostwald ripening, especially under potential control, since it is a major process that occurs during the synthesis of metal NPs and leads to detrimental size instability during electrochemical applications.
关键词： electrochemical control,surface area-to-volume ratio,anodic stripping voltammetry,size-dependent,metal nanoparticles,Ostwald ripening
更新于2025-09-23 15:19:57
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A new electrochemically prepared composite counter electrode for dye-sensitized solar cells
摘要： In this paper, we propose new counter electrodes for applications in dye-sensitized solar cells (DSSCs). Polyaniline (PANi), tungsten trioxide (WO3), and their composite are deposited on indium thin oxide substrates using cyclic voltammetry technique and employed as counter electrodes that reached comparable and superior performances than Pt counter electrodes. These excellent results are achieved due to the high conductivity and electrocatalytic behavior of the prepared materials. Morphological, electrocatalytic, bonding structure, charge transfer properties, and photovoltaic characteristics are respectively investigated by field emission electron microscopy, cyclic voltammetry, Tafel analysis, Fourier-transform infrared spectroscopy, UV-visible spectroscopy, energy dispersive spectroscopy, electrochemical impedance spectroscopy, and current-voltage analysis. Our best DSSC that is fabricated from the WO3/PANi nanocomposite counter electrode demonstrated an efficiency of 6.78%, which is a 12.4% improvement in comparison with the Pt-based DSSC.
关键词： Counter electrode,Tungsten trioxide,Cyclic voltammetry,Composites,Dye-sensitized solar cells,Polyaniline
更新于2025-09-23 15:19:57
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Tuning HOMO and LUMO of three region (UV, Vis and IR) photoluminescent nitrogen doped graphene quantum dots for photodegradation of methylene blue
摘要： Low cost, gram scale and highly N doped graphene quantum dots (NGQDs) with a broad absorption spectrum was synthesized using hydrothermal method by citric acid and urea. The obtained NGQDs possess wide absorption spectrum from ultraviolet to visible and IR range of wavelength. Optical characterization revealed that NGQDs are highly photoluminescent in three region of light (i.e. UV, Vis and IR). The average thickness is lower than 1 nm, meaning that the NGQDs are single, two or three layers of graphene. Lowest unoccupied molecular orbital (LUMO) and highest occupied molecular orbital (HOMO) of the NGQDs determined using a cyclic voltammetry (CV) method, and energy band gap was obtained ～ 1.91 eV. A mechanism of charge carrier generation, separation, transport and photodegradation of methylene blue under illumination was proposed using the energy states. Finally the effect of N concentration on the band gap of NGQDs was simulated and discussed.
关键词： HOMO,NGQD,photodegradation,Quantum ESPRESSO,LUMO,cyclic voltammetry
更新于2025-09-23 15:19:57
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Indirect voltammetric determination of thiomersal in influenza vaccine using photo-degradation and graphene quantum dots modified glassy carbon electrode
摘要： Thiomersal is an organomercury derivative that degrades producing thiosalicylic acid, dithiobenzoic acid and ethylmercury. It is widely used in topical pharmaceutical preparations and as preservative in vaccines and cosmetics. In this work, an electro-analytical method for thiomersal was developed using graphene quantum dots (GQDs) as a surface modifier of a glassy carbon electrode. The method rely on using square-wave voltammetry and exploring the synergistic effect between GQDs, visible radiation and the applied potential in producing very intense Hg oxidation peak during the anodic scan. A linear voltammetric response was obtained for the analyte in the concentration range from 3.0 μmol L-1 (1.2 μg mL-1) to 32 μmol L-1 (12 μg mL-1), with a detection limit of 0.9 m mol L-1 (0.34 m g mL-1). The proposed method was successfully applied for thiomersal determination in influenza vaccine.
关键词： Voltammetry,Graphene quantum dots,Mercury,Thiomersal,Influenza vaccine,Modified glassy carbon
更新于2025-09-23 15:19:57
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Photo-electrochemical Behavior of Silver Nanoparticles inside Mesoporous Titania: Plasmon induced charge separation effect
摘要： The self-assembly block copolymer method was used to synthesize mesoporous titania films and silver nanoparticles (NPs) were grown inside the films. Such silver NPs-titania films are known for their multicolor photochromic properties, due to a photo-oxidation reaction of silver in the presence of titania under light excitation which is attributed to a plasmon induced charge separation (PICS). Here, the photo-electrochemical properties of these composite films have been investigated at different light wavelengths and chemical environment in order to characterize the light-induced redox reactivity modifications. Cyclic voltammetry (CV) study shows that the Ag+ electro-reduction peak potential varies depending on the light irradiation, which determines the state of the silver nanoparticles complexed or not by titania.
关键词： cyclic voltammetry,Silver nanoparticles,photochromism,plasmon,mesoporous titania
更新于2025-09-19 17:15:36
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Polyselenides on the Route to Electrodeposited Selenium
摘要： The electrochemical oxidation of aqueous solutions of hydrogen selenide (HSe – ) and of hydrogen polyselenide ions (HSex – ) on glassy carbon electrodes at pH = 9.2 is reported. In both cases, the oxidation leads to deposits of selenium. The role of polyselenides as intermediates in the process is demonstrated. At 25 ?C amorphous selenium is formed whereas at 70 ?C crystalline selenium is deposited. The possible use of selenium ?lms for technological purposes is discussed.
关键词： polyselenides,cyclic-voltammetry,selenium,electrodeposition
更新于2025-09-19 17:15:36
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Influence of the synthesis method on electrical storage capacity of graphene-related materials
摘要： The electrochemical properties and their relationship with the physico-chemical properties of graphene-based materials have been studied. Graphite was used as the raw material and it was oxidised and then reduced by two alternative approaches, namely thermal and multi-step reduction using ascorbic acid. It was demonstrated that the physico-chemical characteristics of the material are directly related to the synthesis method and greatly influence the major capacitance of the material. It was observed that the materials with lower levels of functional oxygen groups and with a more ordered structure, i.e. similar to graphene powder, are the ideal candidates for use in electrochemical applications as these materials have better capacitance and specific capacitances.
关键词： Graphene-related materials,characterisation,supercapacitors,voltammetry
更新于2025-09-19 17:15:36
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Multifaceted Protocol in Biotechnology || Characterization of Electrochemical Transducers for Biosensor Applications
摘要： Biosensors are devices that detect and report the presence or quantity of a particular analyte. Among the biosensor components, a physicochemical transducer measures physical and chemical changes from analyte-recognition interactions where products, by-products, intermediates, or physical changes are converted into a measurable signal. The character of the transducer determines the performance of a biosensor; hence the characterization of the transduction is crucial in the design of a biosensor. This chapter describes electrochemical characterization of the transducer layer of a biosensor via cyclic voltammetry.
关键词： Effective surface area,Randles-Sevcik,Electrochemical transducer,Cyclic voltammetry,Chronoamperometry,Biosensors
更新于2025-09-19 17:15:36
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[IEEE 2018 IEEE SENSORS - New Delhi, India (2018.10.28-2018.10.31)] 2018 IEEE SENSORS - C-MEMS Derived Glassy Carbon Electrodes as Sensitive Electrochemical Biosensors
摘要： Electrochemical biosensors have high potential for application in point of care setting, as they involve simpler measurements compared to optical counterparts and can operate in complex analyte. In this context, carbon electrodes have been widely explored since it is more stable than other metals. Pyrolyzed carbon electrodes have been deployed for protein sensing but the detection limit achieved is not satisfactory, probably due to the selection of the carbon precursor. In this paper, we have prepared glassy carbon electrodes using conventional carbon-microelectromechanical systems (C-MEMS) process. SU-8 photoresist has been used as the carbon precursor. The carbon thin film electrodes have then been tested by cyclic voltammetry measurements in the potential range of -800 mV to 800 mV in presence of 10 mM potassium ferricyanide solution. The samples have been immobilized with anti-Hep-B monoclonal antibody. The presence of antibodies has been further confirmed by UV-VIS spectrophotometry. It has been observed that the current peak reduces distinctly and the fractional change in current magnitude is around 30% and 83% at the potential of 175 mV for 1 fM and 1 pM concentrations respectively. Hence, the presented study is the proof-of concept of sensitive electrochemical detection of Hep-B using functionalized glassy carbon electrodes which when integrated with a low cost microfluidic platform can become suitable for point-of-care diagnostics.
关键词： biosensor,cyclic voltammetry,glassy carbon,C-MEMS,electrochemical sensing,Hep-B
更新于2025-09-19 17:15:36