Tuba Öznülüer

Synthesis of graphene on gold

Here we report chemical vapor deposition of graphene on gold surface at ambient pressure. We studied effects of the growth temperature, pressure, and cooling process on the growngraphene layers. The Raman spectroscopy of the samples reveals the essential properties of the graphenegrown on gold surface. In order to characterize the electrical properties of the growngraphene layers, we have transferred them on insulating substrates and fabricated field effect transistors. Owing to distinctive properties of gold, the ability to growgraphene layers on gold surface could open new applications of graphene in electrochemistry and spectroscopy.

Formation of Bi2S3 thin films on Au(111) by electrochemical atomic layer epitaxy: kinetics of structural changes in the initial monolayers

Abstract The kinetics and growth mechanism of the first and second monolayers of Bi2S3 by electrochemical atomic layer epitaxy (ECALE) has been studied using voltammetry and chronoamperometry techniques. Scan rate dependent cyclic voltammetry experiments reveal that the peak current in the stripping of the S layer from a Bi modified Au(111) electrode is a linear function of a 2/3 power of the scan rate, ν2/3. Similar behavior is observed for the deposition of Bi on to one atomic layer of an S modified Au(111) electrode. The dissolution of the Bi atomic layer from the S modified Au(111) electrode involves an initial Langmuir-type adsorption–desorption accompanied by a nucleation and two-dimensional (2-D) growth process. When Bi atomic layers are used as a first layer, the nucleation and 2-D growth process was observed for both deposition and stripping. Analysis of the reduced variables demonstrates that the stripping of S from Au(111)Bi and stripping of Bi from Au(111)S fit the progressive model. Our results suggest that the nucleation and 2-D growth mechanism is the dominant process in the formation of Bi2S3 atomic layers if Bi is used as the first layer in the ECALE method.

Stoichiometry, Morphology, and Size-Controlled Electrochemical Fabrication of CuxO (x = 1, 2) at Underpotential

A new one-step electrochemical approach has been developed for the morphology, size, and stoichiometry-controlled synthesis of Cu2O, CuO, and Cu2O/CuO composite structures at room temperature without using surfactants, capping agents, or any other additives. The electrochemical deposition of a Cu monolayer using underpotential deposition (UPD) and the flow rate of oxygen gas bubbled through the deposition solution used for oxidation of the Cu layer are the key parameters for controlling the stoichiometry of the CuxO (x = 1, 2) structures. The morphologies, crystallinity, stoichiometries, optical properties, and photoelectrochemical properties of the as-electrodeposited Cu2O and CuO materials were analyzed using scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), energy dispersive spectroscopy (EDS), UV-vis absorption, and photoelectrochemical (PEC) techniques. The results indicated that the Cu2O and CuO materials electrodeposited on both indium tin oxide coated (ITO) quartz and gold electrodes using this new electrochemical technique exhibit high-quality single crystalline structures and high photoactivity with rapid photoelectrical response to light irradiation.

X- and gamma-ray irradiation effects on vanadium pentoxide thin films

Abstract Thickness and composition of thin films can be measured with X- and gamma-rays. In this work, thickness and composition of vanadium pentoxide thin films are investigated by energy dispersive and wavelength dispersive X-ray fluorescence systems. Also, the surface analysis of vanadium pentoxide thin films irradiated with Rhodium Kα X-rays and 59.54 keV gamma-rays emitted from 100 mCi and 5 Ci Americium-241 radioactive sources is performed by scanning electron microscope. It is observed that X- and gamma-rays are destructive for vanadium pentoxide thin films. Also, the composition of vanadium pentoxide thin films changes by irradiation with X- and gamma-rays.

Fotovoltaik İnce Film Olarak Elektrokimyasal Depozit Edilmiş Cu-Grafen ve Cu2O-Grafen Nanokompozitler

Bu calismada, Au ve indiyum kalay oksit (ITO) elektrotlarda bakir iyonlarinin ve grafen oksitin sulu suspansiyonlarindan es zamanli olarak indirgemesine dayanan Cu-grafen ve Cu2O-grafen nanoyapilarinin elektrokimyasal buyumesine yeni bir yaklasim sunulmaktadir. Elde edilen kompozit nanoyapilar, taramali elektron mikroskobu (SEM), enerji dagilimli spektroskopi (EDS), X-isini kirinimi (XRD), fotoluminesans spektroskopi (PL) ve foto-akim olcumleri ile karakterize edildi. Deney sonuclari, Cu-grafen ve Cu2O-grafen kompozit film yapilarinin, uygulanan potansiyel ve deney ortami ile kolayca kontrol edilebildigini gostermektedir. Sentezlenen Cu-grafen ve Cu2O-grafen nanokompozit fotoelektrotlar; iyi fotovoltaik ozellikler sergilerler ve gunes enerjisi donusumundeki uygulamalar icin kullanilabilirler.