Synthesis, characterization, and application of TiO2 nanoparticles - Effect of pH adjusted solvent

Abstract

TiO2 nanoparticles were synthesized via the sol-gel method by varying the pH of the solvent used in the synthesis. The aim of the pH variation was to study its effect on the surface energy amongst other characteristics, and photocatalytic properties. The sol-gel method was adopted in the synthesis of TiO2 nanoparticles and calcined in air at 400 °C at 2 °C/min. The as-prepared materials were characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), high resolution transmission electron microscopy (HRTEM), N2 sorption, Raman spectroscopy, fluorescence spectrometry, and electron spin resonance spectroscopy (ESR), surface energy analyser (SEA), vibrating sample magnetometer (VSM). Photocatalytic properties of the materials were evaluated by monitoring the decoloration of model dye, methylene blue (MB) under natural sunlight conditions. The as-prepared materials existed in the anatase phase with polycrystalline and paramagnetic properties. The amount of surface defects of the as-prepared materials correlated well with the crystal size. The highest dispersive surface energy, 89.17 mJ/m2 exhibited by TB400, and the least dispersive energy of 49.67 mJ/m2 by TN400 are attributed to their microporosity. The acid - base numbers show that the materials are amphoteric with more of the basic sites. The values of the acidity-basicity ratio confirm the effect of pH in the synthesis of TiO2. The photocatalytic activities of the as-prepared materials were in the order of TB400 > TN400 > TA400, attributed to their characteristic crystal sizes, and surface defects.