Size control of Ag nanoparticles for SERS sensing applications

Ag nanoparticles developed by inert gas aggregation were deposited on silicon and quartz substrates. The samples were annealed under high vacuum at 200C. The influence of annealing time-length on the average size and size dispersion was examined by field emission scanning electron microscopy and UV-visible absorption spectra. The results showed that the average size of the nanoparticles decreased continuously for annealing time up to 6mins followed by a more tight size distribution. After further annealing the average size increased again approaching the average size of the nanoparticles in the non-annealed sample. The samples prepared were tested as substrates for SERS of R6G molecules adsorbed on the Ag nanoparticles. It was found that the characteristic 612cm-1 rhodamine peak followed the variation of the average nanoparticle size.