FDTD Analysis of Size and Shape-Dependent Optical Properties of TiO2 Nanoparticles Embedded in Poly(vinyl Alcohol)

Abstract

This study uses three-dimensional Finite-Difference Time-Domain (FDTD) simulations to investigate how particle size and shape influence the optical properties of TiO₂ nanoparticles embedded in a poly(vinyl alcohol) (PVA) matrix. Spherical nanoparticles with radii of 0.01–0.10 μm and ellipsoidal nanoparticles with aspect ratios of 1.2–2.0 were systematically analyzed. Increasing the sphere radius from 0.01 to 0.10 μm enhances optical absorption and induces a red shift in the absorption spectrum, attributed to stronger light–matter interaction. For equal particle volume, ellipsoidal nanoparticles with an aspect ratio of 2.0 exhibit up to ~1.8-fold higher absorbance than their spherical counterparts, with the enhancement increasing with aspect ratio. Electric-field analysis reveals that this improvement results from stronger localized field confinement near the anisotropic particle surfaces. These quantitative results establish geometry engineering particularly aspect ratio control as a viable route to tune light-harvesting efficiency in TiO₂/PVA nanocomposites, providing direct design parameters for photocatalytic applications.