Au@SiO2 Nanoparticles Sheathed W Nano-Tips for Local Electrochemical and SERS Applications

Wednesday, 4 October 2017: 11:40
Camellia 3 (Gaylord National Resort and Convention Center)
M. Zhang, Y. Ling, S. Yu, Z. Zhang (Tsinghua University), and Y. Gu (Beijing Institute of Petrochemical Technology)
Simultaneous acquisition of information on electrochemistry and phase composition is of great concern in diagnosis and detection of localized corrosion, which is calling for spatial resolution and phase recognition with improved accuracy. In this work, a new structure of Au@SiO2 nanoparticles sheathed W nano-tips for local electrochemical and SERS measurements is proposed, by which W nano-tips are prepared by improved direct current electrochemical etching, followed by coating with Au@SiO2 nanoparticles. The influence of the etching solution composition, voltage and the depth of immersion on the surface structure, tip apex radius and aspect ratios of W nano-tips has been investigated. Gold nanoparticles are prepared with chemical reduction method and the size is controlled via adjusting the molar ratio of sodium citrate to chloroauric acid. By measuring the TEOS and ammonia, the layer of SiO2 is attached onto gold nanoparticles with different thicknesses to produce Au@SiO2 core-shell nanoparticles. The microstructures, morphologies and composition are characterized using TEM, HRTEM and EDX, respectively, while the SERS effect is detected using Rhodamine 6G (R6G) as probe molecules. It was found that the enhancement on both SERS and spatial resolution of electrochemical measurement could be obtained by optimal diameter manipulation of tip apex and Au NPs. This work provides a convenient way to prepare new functional electrodes with the high sensitivity and stability for local electrochemical detection and SERS application.