TiO₂ nanoengineering for high-performance photoelectrochemical biosensors: From fundamental strategies to frontier...

Titanium dioxide (TiO₂), owing to its high stability, low cost, and good biocompatibility, has become a key material in the field of Photoelectrochemical (PEC) biosensors. However, its inherently wide bandgap and severe photogenerated charge carrier recombination fundamentally limit its photoelectric conversion efficiency, confining its light absorption primarily to the ultraviolet region. This review systematically summarizes recent advanced nanoengineering strategies developed to address these bottlenecks, including element doping, heterojunction construction, defect engineering, and multicomponent hybridization. It analyzes how these strategies modulate the electronic and optical properties of TiO₂ to promote charge separation and broaden its photoresponse range. Furthermore, this work showcases the cutting-edge applications of engineered TiO₂ nanomaterials in the highly sensitive detection of disease biomarkers, food contaminants, and environmental pollutants. Finally, the major challenges currently hindering the practical application of TiO₂-based PEC biosensors, such as stability in complex matrices and scalable fabrication, are discussed. Future research directions are also discussed, with particular emphasis on flexible and wearable devices, microfluidic integration, and AI-assisted data analysis. These directions may promote the practical translation of TiO₂-based PEC biosensors toward POCT and continuous health monitoring.