Coordination-Induced Photocurrent Polarity Switching of Black Titanium Dioxide for Tyrosinase Activity Assay

Polarity-switchable photoelectrochemical (PEC) analysis has garnered significant attention owing to its enhanced accuracy and superior anti-interference capability. Developing a straightforward and efficient approach for polarity-switchable PEC analysis is critically essential. We present here a novel approach for polarity-switchable PEC assay by leveraging the coordination interactions between black titanium dioxide (b-TiO₂) and o-diphenol-functionalized BiOI. Specifically, 4-hydroxyphenylacetic acid was covalently functionalized onto hydrolyzed 3-aminopropyl triethoxysilane-modified BiOI nanosheets, and the monophenol groups on BiOI are further converted into o-diphenol groups through tyrosinase (TYR) catalysis. Consequently, the o-diphenol-functionalized BiOI nanosheets are attached to a b-TiO₂-based photoelectrode via coordination interactions between b-TiO₂ and the o-diphenol groups, enabling photocurrent polarity switching of the b-TiO₂-based electrode and polarity-switchable PEC assay of TYR activity. The developed PEC assay of TYR activity exhibits a broad linear range from 0.010 to 10 U mL^-1 and a low detection limit of 0.002 U mL^-1. The present work not only reports an innovative photocurrent polarity switchable strategy but also establishes an effective method for TYR activity assay.