Gallium/gold composite microspheres fixed on a silicon substrate for surface enhanced Raman scattering

Abstract

In this work, gallium (Ga) microspheres were successfully prepared on a silicon substrate by a chemical vapor deposition method and used as templates to fabricate Au nanoparticle-coated Ga (Ga/Au) composite microspheres using an oxidation–reduction reaction between Ga and HAuCl₄. The morphology and composition of the Ga microspheres were characterized by scanning electron microscopy and energy-dispersive X-ray. It was found that Ga microspheres were partly embedded in the Si substrate. The possible formation mechanism was discussed. The content of Au in the composites could be modulated by controlling the reaction time. SERS measurement shows that the content of Au in Ga/Au composite microspheres has a great effect on the SERS activity. The SERS signals collected by point-to-point and SERS mapping images showed that as-prepared composites exhibit good spatial uniformity and reproducibility. Detection of malachite green molecules with a low concentration (1.0 × 10⁻¹⁰ M) was used as an example to show the possible application of such a substrate.