Microwave-Accelerated Surface Modification of Plasmonic Gold Thin Films with Self-Assembled Monolayers of Alkanethiols

Abstract

A rapid surface modification technique for the formation of self-assembled monolayers (SAMs) of alkanethiols on gold thin films using microwave heating in <10 min is reported. In this regard, SAMs of two model alkanethiols, 11-mercaptoundecanoic acid (11-MUDA, to generate a hydrophilic surface) and undecanethiol (UDET, a hydrophobic surface), were successfully formed on gold thin films using selective microwave heating in (1) a semicontinuous fashion and (2) a continuous fashion at room temperature (24 h, control experiment, no microwave heating). The formation of SAMs of 11-MUDA and UDET was confirmed by contact angle measurements, Fourier transform infrared (FT-IR) spectroscopy, and X-ray photoelectron spectroscopy (XPS). The contact angles for water on SAMs formed by the selective microwave heating and conventional room temperature incubation technique (24 h) were measured to be similar for 11-MUDA and UDET. FT-IR spectroscopy results confirmed that the internal structures of SAMs prepared using both microwave heating and room temperature were similar. XPS results revealed that the organic and sulfate contaminants found on bare gold thin films were replaced by SAMs after the surface modification process had been conducted using both microwave heating and room temperature.