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

• Published in: Journal of molecular liquids 2021-02, Vol.323, p.115074, Article 115074
• Main Authors: Doost, Hamid Akherat, Ghasedi, Arman, Koushki, Ehsan
• Format: Article
• Language: English
• Subjects: AuNPs; Band gap energy; Fermi level; PVA; Surfactant; Titanium dioxide nanoparticles; Z-scan technique
• ISSN: 0167-7322; 1873-3166
• DOI: 10.1016/j.molliq.2020.115074

In this work, titanium dioxide nanoparticles (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 3.2 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. [Display omitted] •TiO2 wrapped with PVA and TiO2 loaded with Au nanocomposites were synthesized through a facile technique.•High degree of polarization of the PVA governs the electrical characteristics of the TiO2 NPs.•TiO2 NP energy levels were perturbed (Stark effect) by inducing an outward force upon addition of PVA.•Optical measurements suggest that PVA loaded with Au can be utilized as optical bistable switchers.