RF-sputtering preparation of gold-nanoparticle-modified ITO electrodes for electrocatalytic applications

Abstract

The preparation of gold-nanoparticle (AuNPs)-modified indium tin oxide (ITO) electrodes (AuNPs/ITO) was performed by radio-frequency (RF) sputtering from Ar plasmas at temperatures as low as 60 °C, tailoring the AuNP morphology and content as a function of the sole sputtering time. The latter parameter was varied from 5 to 20 min in order to investigate the influence of gold amount and distribution on the electrochemical performances of the resulting AuNPs/ITO systems. The electrodes were characterized using field emission-scanning electron microscopy (FE-SEM), UV-vis absorption and x-ray photoelectron spectroscopies (XPS); moreover variable scan rate cyclic voltammetry (CV) studies were performed to examine their electrochemical behavior. The electrocatalytic activity of the nanostructured AuNPs/ITO electrodes toward methanol oxidation was investigated and compared with a continuous gold film (Aufilm/ITO). The catalytic efficiency of the AuNPs/ITO systems was found to increase with the gold content and the AuNPs-support boundary region in the corresponding samples. For the longest sputtering time (i.e. 20 min) the performances of the nanostructured electrode were better than the Aufilm/ITO reference, despite the much lower catalyst amount. Furthermore, conversely from the AuNPs/ITO samples, in the Au(film)/ITO case the gold film displayed a poor adhesion to the substrate and the electrode could be used only for a limited number of electrochemical cycles.

Influence of Substrate, Additives, and Pulse Parameters on Electrodeposition of Gold Nanoparticles from Potassium Dicyanoaurate

“…[1,2] Conductive substrates coated with AuNPs are usable in electronic and biochemical sensors and electrodes owing to their excellent electrocatalytic behavior. [2][3][4][5][6][7] An example is AuNP-ITO which is used for making electrodes. [8] This material has good electrical conductivity, high stability, and capability to promote heterogeneous electron transfer.…”

“…[8] This material has good electrical conductivity, high stability, and capability to promote heterogeneous electron transfer. [2,3,9] Applications of AuNP-ITO include the electro-oxidation of uric acid, ascorbic acid, dopamine, norepinephrine, epinephrine, [10] and nitric oxide. [11] AuNP-ITO provides a biocompatible matrix for immobilization of hemoglobin (Hb), [12] effective H 2 O 2 reduction catalysis with stable reproducibility, [12] myoglobin (Mb) immobilization, and mediator-free H 2 O 2 sensor development [13] with promotion of the electrocatalytic activity of three-dimensional monolayer of 3-mercaptopropionic acid (MPA) assembled on AuNP-ITOs, [14] electrochemical response of the hydroquinone and p-aminophenol in phosphate buffer solutions [15] and electrochemical measurement of biomolecules such as simultaneous electrochemical determination of guanosine/guanosine-5¢-triphosphate, adenosine/adenosine-5¢-triphosphate, and dopamine/serotonin.…”

“…[19] Several methods have previously been used for attachment of AuNPs onto ITO. [3,7,8] General strategy has been self-assembly of binder molecules onto ITO. This method has been influenced by catalytic property and conductive behavior of the NPs.…”

“…[4,8] This technique has, however, been complex and timeconsuming. RF-sputtering [3] and nano-sphere lithography [20] have also been practiced to attach AuNPs onto an ITO substrate.…”

An Electrochemical H<SUB>2</SUB>O<SUB>2</SUB> Detection Method Based on Direct Electrochemistry of Myoglobin Immobilized on Gold Deposited ITO Electrode

“…Metal nanoparticles in conjugation with redox proteins have been proved good candidates for enzymatic molecule based biosensors as AuNPs has large surface area for enzyme immobilization, its biocompatible nature and suitable for direct electron transfer from catalytic molecule to electrode. 20 Hence the modified hybrid electrodes usually exhibit a unique electrocatalytic behavior or high sensitivity. The electrochemical detection of H 2 O 2 by using protein containing the heme groups, such as myoglobin [21][22] and hemoglobin [23][24] which possess peroxidase like catalytic activity, which can reduce H 2 O 2 due to electroactive heme center, has been reported by different research groups.…”