The effects of operating parameters on the morphology, and the SERS of Cu NPs prepared by spark discharge deposition

Copper nanoparticles were fabricated and deposited on a glass substrate by spark discharge of copper electrode under different atmospheric conditions for SERS application. An interesting dependence of the deposition process and the formation of different particle structures on the deposition atmospheres were observed. Static air atmosphere ensured the deposition of the Cu particles on the glass surface by avoiding the repulsion between charged Cu particles and the surface of the glass through the formation of CuO, which acts as a seed mediated for nanorods formation. The average diameter of the as-deposited Cu rods was measured by the TEM to be 39 nm. Thermal annealing of the film up to 200 degrees C resulted in a reduction in the diameter of the nanorods as well as an increase in the rod density. A water solution of dye molecule (crystal violet) with a concentration of 1 x 10(-6)to 1 x 10(-9) M was dropped on the prepared Cu substrate. Raman signals from dye molecule were detected and their intensities changed according to deposition time, post-annealing temperature and dye concentration. A significant increase in the Raman scattering signal of a dye molecule was observed in the film fabricated at 30 min of deposition time and post-annealed temperature of 200 degrees C for 1 h. This substrate provides a maximum SERS intensity with a detection limit of 1 x 10(-8) M, with an enhancement factor of 3.9 x 10(3). The SERS performance of the substrates was correlated well with the change in their surface morphologies.