Three-dimensional titania arrays coupled with dopamine for visible-light-induced photoelectrochemical sensing

Three-dimensional TiO₂ hierarchical nanowire arrays were synthesized featuring nanocavities via a hydrogen peroxide-assisted wet chemical reaction, followed by a simple liquid-phase deposition process. We subsequently decorated the TiO₂ arrays with dopamine, leveraging its enediol ligand for chelation. Reduced nicotinamide adenine dinucleotide (NADH), a cofactor for over 300 dehydrogenases, serves as the targeted analyte to assess the PEC sensing performance of the sensor. The developed sensor exhibited a linear concentration range for NADH detection of 0.05 to 50 µM, achieving a high sensitivity of 0.29 μA∙μM^-1∙cm^-2 and a low detection limit of 0.03 μM (signal-to-noise ratio of 3). Notably, PEC performance of the resulting sensor surpassed that of commercial TiO₂ (P25)-based sensors. The enhanced sensing capabilities can be attributed to several factors: the TiO₂ hierarchical nanowire arrays with nanocavities provide a larger surface area, abundant active sites, and shorter molecular diffusion lengths for surface adsorption and reaction, thereby reducing response times and improving sensitivity. Additionally, the coupling of TiO₂ with dopamine enhances visible light absorption and optimizes charge transfer dynamics. These findings open a new avenue for designing high-performance three-dimensional nanoarchitectures for PEC sensing applications.