Thermal-driven attachment of gold nanoparticles prepared with ascorbic acid onto indium tin oxide surfaces
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RESEARCH PAPER
Thermal-driven attachment of gold nanoparticles prepared with ascorbic acid onto indium tin oxide surfaces Md. Abdul Aziz • Munetaka Oyama
Received: 26 December 2012 / Accepted: 26 March 2013 / Published online: 6 April 2013 Ó Springer Science+Business Media Dordrecht 2013
Abstract Thermal-driven attachment of gold nanoparticles (AuNPs), of which size was less than 50 nm, onto the surfaces of indium tin oxide (ITO) is reported as a new phenomenon. This was permitted by preparing AuNPs via the reduction of hydrogen tetrachloroaurate (HAuCl4) with ascorbic acid (AA). While the AuNPs prepared via the AA reduction sparsely attached on the surface of ITO even at room temperature, a heat-up treatment at ca. 75 °C caused denser attachment of AuNPs on ITO surfaces. The attached density and the homogeneity after the thermal treatment were better than those of AuNP/ITO prepared using 3-aminopropyl-trimethoxysilane linker molecules. The denser attachment was observed similarly both by the immersion of ITO samples after the preparations of AuNPs by AA and by the in situ preparation of AuNPs with AA together with ITO samples. Thus, it is considered that the thermal-driven attachment of AuNPs would occur after the formation of AuNPs in the aqueous solutions, not via the growth of AuNPs on ITO surfaces. The preparation of AuNPs with AA would be a key for the thermal-driven attachment because the same attachments were not observed for AuNPs prepared with citrate ions or commercially available tannic acid-capped AuNPs.
Md. A. Aziz M. Oyama (&) Department of Material Chemistry, Graduate School of Engineering, Kyoto University, Nishikyo-ku, Kyoto 615-8520, Japan e-mail: [email protected]
Keywords Gold nanoparticles Hydrogen tetrachloroaurate Ascorbic acid Indium tin oxide Thermal treatment
Introduction For preparing gold nanoparticles (AuNPs) in aqueous solutions, the reduction of AuCl4- with citrate is a well-known method since a report by Turkevich et al. (1951) and the refinement by Frens (1973). On the other hand, reports on the reduction of AuCl4- with ascorbic acid (AA) are very limited though it can also prepare AuNPs in aqueous solutions. For example, Kimling et al. (2006) studied the AA reduction process at room temperature to compare with the citrate reduction initiated with thermal treatments and UV irradiation for preparing AuNPs. Goia and coworkers explored the reduction by iso-ascorbic acid (iso-AA) (Goia and Matijevic 1999; Andreescu et al. 2006), which is equivalent in reducing properties with AA but biologically inactive (Goia and Matijevic 1999). Compared with the citrate reduction, ‘‘stabilizer-free’’ AuNPs were reported to be prepared in aqueous solutions at ambient temperature (Andreescu et al. 2006). Recently, Aslam and coworker reported the pH-dependent synthesis of AuNPs using AA (Tyagi et al. 2011). In addition to these achievements, i.e., the pure reaction of AuCl4- and AA or iso-AA, the reduction by AA was conducted in the presence of
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