Integrated Bi2O3 nanostructure modified with Au nanoparticles for enhanced photocatalytic activity under visible light irradiation

An integrated Bi₂O₃ (i-Bi₂O₃) nanostructure with a particle size 10 nm inducing agglomerated structure were synthesized by dissolving bismuth nitrate pentahydrate in diethylene glycol at 180 °C with post heat treatment. The prepared i-Bi₂O₃ nanostructures were employed for the construction of Au/i-Bi2O3 composite system and characterized by X-ray diffraction pattern, UV–visible diffuse reflectance spectroscopy (DRS), and transmission electron microscopy, X-ray photoemission spectroscopy (XPS) and Energy dispersive X-ray spectroscopy (EDS). The i-Bi₂O₃ nanostructure and Au/i-Bi₂O₃ composite system were found to exhibit high photocatalytic activity than commercial Bi₂O₃ in decomposing salicylic acid under visible light irradiation. The high catalytic activity of i-Bi₂O₃ nanostructure was deduced to be caused by charge separation facilitated by electron hopping between the particles within the integrated structure and space-charge separation between i-Bi₂O₃ and Au. The charge separation behavior in i-Bi₂O₃ nanostructure was further bolstered by comparing the measured. OH radical produced in the solution with i-Bi₂O₃ nanostructure, commercial Bi₂O₃ and Au/i-Bi₂O₃ composite which readily react with 1,4-terephthalic acid (TA) inducing 2-hydroxy terephthalic acid (TAOH) that shows unique fluorescence peak at 426 nm. The space-charge separation between i-Bi2O3 and Au was confirmed by measuring the electron spin resonance (ESR) spectra.