Determination of dissolved oxygen based on photoinduced electron transfer from quantum dots to methyl viologen

Abstract

A rapid colorimetric methodology based on photoinduced electron transfer from excited CdS quantum dots (CdS QDs) to methyl viologen (MV²⁺) has been developed for the sensitive determination of dissolved oxygen (DO) content. The reduction of MV²⁺ is initiated by light excitation of CdS QDs, which induces the electron transfer from sacrificial donor glutathione (GSH) to the photogenerated hole of CdS QDs. Due to the presence of oxygen, the reduced radical-cation of methyl viologen (MV⁺˙) could be rapidly reoxidized, thus turning into the original methyl viologen dication (MV²⁺). The existence of MV⁺˙ is confirmed by electron paramagnetic resonance technique. This proposed colorimetric methodology has been applied to quantify the concentration of DO in real water samples. The result is consistent with the value obtained while adopting the traditional standard Winkler's methodology. A linear response of the absorbance of CdS QDs-GSH-MV system to the different concentrations of DO is obtained in the range of 0.75∼7.95 ppm, with a detection limit of 0.23 ppm in pH 7.5.