Facile detection of photogenerated reactive oxygen species in TiO2 nanoparticles suspension using colorimetric probe-assisted spectrometric method.

This present study reports that reactive oxygen species (ROS), which mainly consist of hydroxyl (OH) and superoxide (O2(-)) radicals generated by the photocatalysis of TiO2 nanoparticles (TiO2 NPs) in suspension, can be quantitatively measured by the colorimetric probe-assisted spectrometric method without any interference by the TiO2 NPs. The interference effect of the TiO2 NPs with UV-vis spectroscopy was excluded by the selective separation of p-nitrosodimethylaniline (RNO) and tetrazolium salt (XTT) (probe compounds for OH and O2(-), respectively) from the TiO2 NPs in the suspension by centrifugation at a specified ionic strength adjusted with phosphate buffer (KH2PO4/NaOH, PB) solution. This colorimetric probe-assisted spectrometric method was also successfully applied to measure the steady-state production of photogenerated ROS in a TiO2 NPs suspension.