Ion Irradiation Induced SPR of Au Nanoparticles in Carbon

Abstract

Nanoparticles of gold in carbon are synthesized by co-sputtering of gold and graphite in high vacuum chamber using neutral Ar atom beam. Thin films are deposited on glass, Si and carbon coated Cu TEM grid substrates. These films are irradiated with 120 MeV Ag ions at different fluences 1x1012, 5 x1012, 1 x 1013 and 3 x 1013 ions/cm2 using Pelletron accelerator. The structural and optical properties of pristine and irradiated nanocomposite thin films are characterized by transmission electron microscopy and UV-visible absorption spectroscopy, respectively. The Au nanoparticles are observed to be too small (~ 1.5 nm) to excite the plasmon resonance in the pristine film. With ion irradiation, a clear but broad SPR peak is found at ~ 526 nm for the nanocomposite thin film irradiated at a fluence of 1 x 1013 ions/cm2, which is slightly red shifted to ~ 529 nm at a fluence of 3 x 1013 ions/cm2 with a broader width. The red shift is ascribed to the growth of the particles due to enhanced diffusion and ostwald ripening. The average particle size at 3 x 1013 ions/cm2 fluence is found to be ~ 2.1 nm. The sharp rings in selected area electron diffraction pattern also confirmed the growth of the Au nanoparticles.