Optical property of gold nanoparticles modified by plasma exposure and sputtering

Kawaguchi, Kazuhiro; Sanari, Takumi*; Takahiro, Katsumi*; Yamamoto, Shunya; Yoshikawa, Masahito; Nagata, Shinji*

Optical extinction spectrum of gold nanoparticles (Au NPs) exhibits a strong peak due to the localized surface plasmon resonance (LSPR). The extinction peak by LSPR change in dependence on a medium surrounding Au NPs. Recently, new sensing materials have been developed for organic gas sensors using LSPR. The extinction peak by LSPR, however, often differs from the ideal values because of impurities adhered on Au NPs surface in air. In this study, plasma and ion sputtering treatments have been employed to eliminate impurities on the Au NPs surfaces. As the result, it was found that carbonaceous impurities decrease significantly from X-ray photoelectron spectroscopy and the wavelength of the LSPR extinction peak close to ideal value. In addition, the observation by scanning electron microscopy was indicated no significant change in the morphology of Au NPs after the treatments. We concluded plasma and ion sputtering treatments were effective methods to obtain Au NPs with clean surfaces.