Size-Dependent Investigation of Surface Modified Gold Nanoparticles for Surface-Enhanced Raman Spectroscopy

CHI-TUNG CHIANG, Jeffrey T Roberts

Purdue University

     Abstract Number: 115
     Last modified: March 31, 2011

Abstract
The size-dependence of gold nanoparticles (AuNPs) for surface-enhaced Raman spectroscopy (SERS) has been investigated using particles produced and processed in the aerosol state. AuNPs were generated by a home-built heating well in which gold wires were placed in the alumina coated tungsten wire basket. Aerosol particles were formed by flowing 1.5 lpm nitrogen gas over near-melting gold inside a resistively-heated basket. Particle production was controlled by the power applied to the heating well. The surfaces of size-selected particles were thermally processed in the aerosol state by introducing vapor of thiol (R-SH) and carboxylate (RCO2H) molecules. Particle production process and particle size distributions were characterized by differential mobility analysis (DMA). Changes in mobility diameter of size-selected particles after thermal processing were monitored by tandem differential mobility analysis (TDMA). Transmission electron microscopy (TEM) and X-ray Diffraction (XRD) were used to confirm the particle morphology and crystalline structures. Surface chemistry of particles was analyzed by Fourier transform IR spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). The resulting size-selected and surface modified AuNPs were deposited on silicon wafers to serve as substrates for surface-enhanced Raman spectroscopic studies. These results not only provide an alternative route to produce surface modified AuNPs but also establish the correlation of AuNPs size and surface in SERS applications.