Optical characterization of surface plasmon resonance of Pt nanoparticles in TiO2-SiO2 nanocomposite films

Abstract

The surface plasmon resonance (SPR) of Pt nanoparticles (NPs) in TiO2-SiO2 nanocomposite films, in which Pt NPs of about 5 nm are incorporated, is investigated by using spectroscopic ellipsometry. After obtaining the dielectric functions of Pt NPs from the Pt-SiO2 nanocomposite film, Pt-TiO2-SiO2 nanocomposite films are analyzed by applying a homogenous single layer model with an effective medium approximation. The effects of Pt NPs on the optical properties of the nanocomposite films are clearly revealed in the imaginary part of the dielectric functions, showing an increase in broadband absorption near the band gap of the films with the increasing volume fraction of Pt NPs in the films. Particularly, the maximum of extinction cross-section of Pt NPs in the films coincides with the broadband absorption, indicating that the localized SPR of Pt NPs is responsible for the enhanced light absorption at the visible-light wavelengths. This work emphasizes that, although SPR absorption of Pt NPs is not so distinctive in the visible-light wavelengths, proper tuning of the dielectric environment as well as the volume fraction of Pt NPs can enhance the photoactivity of the nanocomposite films. © 2017 Author(s)