Effects of linker molecules on the attachment and growth of gold nanoparticles on indium tin oxide surfaces

Abstract

As a linker molecule to attach gold nanoparticles (AuNPs) on indium tin oxide (ITO) surfaces, cysteamine was examined together with well-known 3-mercaptopropyltrimethoxysilane (MPTMS) and 3-aminopropyltrimethoxysilane (APTMS). Systematic comparisons of AuNPs’ nanostructures formed on ITO were carried out after the room temperature treatment in an ethanol solution of linker molecules followed by the attachment of AuNPs using (i) one-step immersion into the 20-nm Au colloidal solution or (ii) two-step immersion, i.e., a seed-mediated growth treatment. Consequently, in case (i), it was found that APTMS was most effective for denser and homogeneous attachment of AuNPs on ITO surfaces with keeping the dispersion. With the MPTMS or cysteamine linkers in case (i), AuNPs aggregated on the ITO surfaces, and the attached amount of AuNPs were larger with the MPTMS linker. In contrast, in case (ii), nanostructural growth of AuNPs was possible with MPTMS or cysteamine using the seed-mediated growth, while the growth of AuNPs was significantly suppressed with the APTMS linker. Because quite different results were obtained between APTMS and cysteamine, it was found that the attachment and nanostructural growth of AuNPs on the organic linker layers cannot be simply governed by the functional groups, –NH 2, on the outer surfaces.