Evidence of an enhanced interband absorption in Au nanoparticles: Size-dependent electronic structure and optical properties

Abstract

The present study reports clear evidence and physical significance of an interband transition due to the transition from the d band to an empty state in the conduction band in the optical absorption spectra of Au nanoparticles. The optical absorption due to interband transitions has been observed to dominate the plasmon absorption on decreasing the particle size. X-ray photoelectron spectroscopy and optical absorption studies reveal the metallic nature even for smaller sizes of 2.5nm.