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Chemical and morphological characterization of photoactive SiOx films electrodeposited on Pt substrate
摘要： SiOx films electrodeposited on platinum (Pt) substrate were shown to exhibit n-type photoactivity while placed both in aqueous and organic solutions. The films were obtained via potentiostatic deposition at potential values ranging from ?2.25 to ?2.75 V. The mechanism of the electrodeposition involved reactions with the used electrolyte and with traces of water as sources of oxygen and hydrogen, as interpreted from Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). The photoactivity of the deposits deceased at potential ?2.75 V. The highest observed photocurrent was ca. 60 μA/cm2 and it was registered in organic solution. The band gap energies determined by XPS technique were approximately 2.5, 2.3 and 3.7 eV for films electrodeposited at ?2.25, ?2.5 and ?2.75 V, respectively. The depth profiles of Si, O and H in the films were registered by glow discharge optical emission spectroscopy (GD-OES), which showed that the film thickness was ca. 0.4 μm. The n-type photoactivity was associated with oxygen evolution from the aqueous solution (0.1 M HClO4, pH 1), whereas the time instability as a function of time observed for the photocurrent was associated with morphological changes of the films as seen by scanning electron microscopy (SEM) and their oxidation detected by XPS and FTIR spectroscopies.
关键词： Silicon oxides,XPS,SiOx,Photoactivity,Platinum,Electrodeposition
更新于2025-09-09 09:28:46
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Syntheses of 1,3-bis(2-arylimino)isondoline type ligands and some metal complexes containing EDOT moiety
摘要： EDOT (3,4-ethylenedioxythiophene) substituted 1,3-bis(2-arylimino)isoindoline derivatives EDOT-BAI1, EDOT-BAI2, EDOT-BAI3, and EDOT-BAI4 have been synthesized according to the Linstead or Siegl’s method. Preparation of palladium(II) and platinum(II) complexes of EDOT-BAI1 and EDOT-BAI2 have been also accomplished in this study. The new compounds have been characterized by FT-IR, NMR, UV-Vis spectroscopies and via mass spectrometric analysis. The present EDOT derivatives provide new starting materials that may be useful in the synthesis of new, functional electropolymers.
关键词： palladium,bis(arylimino)isoindoline,Poly(3,4-ethylenedioxythiophene),platinum
更新于2025-09-09 09:28:46
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A Computational Study on the Variation of Bandgap Due to Native Defects in Non-Stoichiometric NiO and Pd, Pt Doping in Stoichiometric NiO
摘要： This paper presents a computational study of non-stoichiometric nickel oxide in a 64-cell NiO system to model and validate localized heating effects due to nanosecond laser irradiation. Variation in the Bandgap of NiO is studied as a function of varying concentrations of native defects, ranging from 0 to 25%. It is observed that there is a slight increase in the bandgap from 3.80 eV for stoichiometric NiO to 3.86 eV for Ni-rich NiO and to 3.95 eV for O-rich NiO. It is hence deduced that the experimental laser irradiation leads to simultaneous reduction of Ni2+ ions and the oxidation of NiO as the number of laser pulses increase. As well, a detailed study on the effects of doping nickel family elements, i.e., palladium (Pd) and platinum (Pt), in stoichiometric NiO is presented. A bandgap decrease from 3.8 eV for pure NiO to 2.5 eV for Pd-doping and 2.0 eV for Pt-doping for varying doping concentrations ranging from 0–25% Pd, Pt, respectively, is observed.
关键词： dopants,platinum,palladium,nickel oxide,bandgap
更新于2025-09-04 15:30:14
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Evaluation of electroless Pt deposition and electron beam Pt evaporation on p-GaAs as a photocathode for hydrogen evolution
摘要： This study examines the changes in the photoelectrochemical (PEC) properties with Pt morphology after wet (electroless Pt deposition) and dry (e-beam Pt evaporation) deposition of Pt on p-GaAs. The Pt morphology and composition of the p-GaAs surface differed depending on the Pt deposition method, which in turn affected the optical and PEC properties of Pt on the GaAs electrode. Thus, the findings of this study can help in gaining a clearer understanding of the manner in which these changes affect the operation of a GaAs PEC water-splitting electrode.
关键词： Electrocatalyst,Electron beam evaporation,Gallium arsenide,Water splitting,Electroless deposition,Platinum
更新于2025-09-04 15:30:14
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Growth of Millimeter-Sized Graphene Single Crystals on Al <sub/>2</sub> O <sub/>3</sub> (0001)/Pt(111) Template Wafers Using Chemical Vapor Deposition
摘要： The synthesis of graphene using chemical vapor deposition on platinum surfaces is discussed. The crystalline nature of the platinum substrates as well as the graphene growth conditions play a key role to yield monolayer graphene with low defectivity. The need for template wafers with a single Pt orientation emerges due to graphene overgrowth on untextured polycrystalline Pt foils. Single-crystalline Pt foils can be obtained after long annealing steps. However, these Pt foils remain rough and are therefore less suitable during subsequent graphene transfer procedures. On the other hand, highly oriented platinum thin films avoid the overgrowth issues but result in differing nucleation phenomena on different oriented grains. An optimized graphene growth template is found in Al2O3(0001)/Pt(111), which is more than one order of magnitude flatter compared to the annealed Pt(111) foils and serves as an ideal catalyst to grow graphene grains exceeding 7 mm in diameter.
关键词： chemical vapor deposition,single crystals,platinum,Al2O3(0001)/Pt(111),graphene
更新于2025-09-04 15:30:14
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Development of a scanning probe microscopy integrated atomic layer deposition system for <i>in situ</i> successive monitoring of thin film growth
摘要： A dual chamber system integrated with atomic layer deposition (ALD) and atomic force microscopy (AFM) was developed for the successive monitoring of nanoparticles to thin film growth process. The samples were fabricated in the ALD chamber. A magnetic transmission rod enabled sample transferring between the ALD and the AFM test chambers without breaking the vacuum, avoiding possible surface morphology change when frequently varying the growth condition and oxidation under ambient condition. The sample transmission also avoids deposition and contamination on the AFM tip during the successive testing. The sample stage has machined a group of accurate location pinholes, ensuring the 10 μm2 measurement consistency. As a demonstration, the platinum thin films with different thickness were fabricated by varying ALD cycles. The surface morphology was monitored successively during the deposition. Under vacuum with controlled oxygen partial pressure, the aging and sintering phenomenon of particles has been studied in the AFM testing chamber after high temperature treatment. The integrated AFM/ALD instrument is potentially a powerful system for monitoring the thin film preparation and characterization.
关键词： platinum thin films,atomic force microscopy,in situ monitoring,atomic layer deposition,thin film growth
更新于2025-09-04 15:30:14