Catalytic Growth of CdS Nanowires by Microplasma-Prepared Gold Nanoparticles

Abstract

Integrating semiconductor nanowires with silicon platforms can combine the advantages of both materials to provide new functionality compared with each type of material. However, the direct localized growth of semiconductor nanowires on silicon platforms still remains a challenge. Herein, an atmospheric pressure microplasma jet, based on the integration of microplasma with the 3D printing technique, was applied for the synthesis of gold nanoparticles (AuNPs). The obtained AuNPs were then used as catalysts for the physical vapor deposition (PVD) growth of cadmium sulfide nanowires (CdS NWs). The results showed that AuNPs can be directly fabricated on the surface of silicon wafers in one step without chemical reducing agents. They also demonstrated good catalytic activity in the growth of CdS NWs via a typical vapor–liquid–solid (VLS) mechanism, where CdS NWs of straight sidewalls with a AuNP at their tips were formed. Complementary characterization reveals that CdS NWs possess crystalline structure, with the atomic ratio of Cd/S close to 1:1 stoichiometry. The energy band gap was estimated to be 2.5 eV from the photoluminescence spectrum. In addition, the influence of process parameters like the Au³⁺ concentration and plasma processing time on the products was studied. Both increase of the Au³⁺ concentration and plasma processing time led to the formation of high-density AuNPs and CdS NWs. With the rise of the Au³⁺ concentration, the average diameter of the AuNPs gradually increased from 13.17 nm at 0.02 mM to 17.0 nm at 0.05 mM and finally 20.44 nm at 0.1 mM. This also led to the formation of CdS NWs of large diameters. This work offers a simple, direct, and green way for localized fabrication of metal catalysts on target substrates for the growth of NWs and has unprecedented potential in various fields like catalysis, surface modification, and additive manufacturing.