Mesoporous wide bandgap semiconductors offer high photocatalytic oxidation and mineralization activities. In this study, mesoporous beta-Ga2O3 diamond nanorods with 200-300 nm in diameter and 1.0-1.2 mu m in length were synthesized via a urea-based hydrothermal method using polyethylene glycol (PEG) as template agent. The UV photocatalytic oxidation activity of beta-Ga2O3 for gaseous toluene was evaluated, and 7 kinds of intermediates were monitored online by a proton transfer reaction mass spectrometry. Photoluminescence spectra manifested that the dosage and molecular weight of PEG are crucial for formation of vacancies and photocatalytic oxidation activities. A PEG-assisted hydrothermal formation mechanism of mesoporous beta-Ga2O3 diamond nanorods was proposed. Based on the health risk influence index (eta) of the intermediates, the calculated health risks revealed that the beta-Ga2O3 nanorods with a eta value of 9.6 are much safer than TiO2 (eta = 17.6). (C) 2011 Elsevier B.V. All rights reserved.