Au nanoclusters-decorated WO 3 nanorods for ultrasensitive photoelectrochemical sensing of Hg 2 .

Photosensitizers and enzyme mimics are extensively used in photoelectrochemical (PEC) sensing, but few materials can be used as both photosensitizers and enzyme mimics in PEC sensing. Herein, we report Au nanoclusters (AuNCs) as both photosensitizers and peroxidase mimics for sensitive PEC sensing of Hg 2+ . It is found that AuNCs can act as photosensitizers to improve the PEC activity of WO 3 nanorods; so the WO 3 /AuNCs composite material can be used as an advanced photosensitive material for PEC detection. AuNCs can also catalyze precipitate formation on the photoelectrode because of their peroxidase mimetic activity, and the interface electron transfer is hindered by the formed precipitate. Thus, the photocurrent of the WO 3 /AuNCs-based photoelectrode is quenched. When Hg 2+ is present, the AuNCs-catalyzed precipitate formation is inhibited by Hg 2+ because of the binding of Hg 2+ to AuNCs through Hg 2+ -Au + interactions. The photocurrent of the WO 3 /AuNCs-based photoelectrode increases accordingly, enabling "signal on" PEC detection of Hg 2+ . A broad linear range for Hg 2+ detection is achieved between 1.0 pM and 50 nM with a detection limit of 0.2 pM. We have developed an advanced photosensitive material and introduced a simple method for PEC detection of Hg 2+ .