Size Dependent Reflective Properties of TiO2 Nanoparticles and reflectors made thereof

Abstract

The present work investigates the size dependent reflective properties of TiO2 nanoparticles and discusses the development of reflectors. The nanocrystalline TiO2 powders with different crystallinity and phase structures were obtained by controlling the reaction parameters. TiO2 nanoparticles synthesized via sol-gel method were characterized by using X-ray diffraction (XRD), transmission electron microscope (TEM), UV-Vis absorption fluorospectrophotometer and UV-Vis diffuse reflectance spectroscopy (UV-Vis DRS). Rutile phase TiO2 nanoparticles with crystallite sizes in the range, 77.50 - 78.31 nm, were obtained by adjusting the L value in the range 20 to 50. On calcining the TiO2 powders from 350oC to 900oC, the particle size increases from 60 to 150 nm and band gap energy decreases from 3.42 to 3.14 eV, calculated respectively using TEM micrograph and UV-Vis absorption spectra. PL spectrum shows a broad luminescence peak at 431 nm, irrespective of the different calcination temperatures. TiO2 nanoparticles with L value of 40 shows the attainment of maximum diffuse reflectance (99.50 - 99.60%). Employing these nanoparticles as reflective pigment, coating material was prepared and applied on plastic substrate with different coating thicknesses to develop reflectors. These reflectors show maximum diffuse reflectance, 97.12 - 96.91%, for the 0.25-mm thick coating with 17% pigment to binder weight ratio