Electrical effects of AuNPs and PVA polymers on optical band gap and thermo-optical properties of TiO2 nanoparticles

In this work, titanium dioxide nanopartides (TiO2 NPs) have been synthesized and characterized by conducting X-ray Powder Diffraction (XRD), Uv-visible, and Dynamic Light Scattering (DLS) measurements. Band gap energy of the TiO2 NPs was calculated by analyzing of Uv-visible absorption spectrum of the colloidal solutions and was achieved about 32 eV. In the next step, TiO2 NPs were embedded into poly(vinyl alcohol) (PVA) matrix, a dielectric agent and mixed with gold nanoparticle as conductive agent. It was found that these two kinds of agents put different effects on optical absorption spectrum, band gap energy, and also nonlinear optical properties of TiO2 NPs. It was concluded that the free electron of the gold nanoparticles (AuNPs) reduces the band gap of TiO2 NPs. On the other hand, the high electrical polarization of PVA polymers, modify the surface of TiO2 NPs and enhance the band gap of it. Electron transition mechanisms of the samples were described due to these two mechanisms. Also, z-scan measurements were carried and nonlinear optical properties, which are mainly due to thermo-optical and reversed saturation absorption, were measured by an Nd-YAG laser beam. Results of z-scan experiments were in accordance with hypothesize. These results can open new sights about the optical properties of hybrid nanocolloids which are very important in biological and photocatalytic application of nanoparticles. (C) 2020 Elsevier B.V. All rights reserved.

Automated summary

TiO2 NPs were synthesized and characterized, then embedded into PVA matrix with gold nanoparticles to study their optical and nonlinear optical properties. The results showed different effects of gold nanoparticles and PVA polymers on the band gap energy and properties of TiO2 NPs.