TiO₂-BiVO₄ Heterostructure to Enhance Photoelectrochemical Efficiency for Sensitive Aptasensing

This work designed a nanocomposite to enhance the photoelectrochemical (PEC) efficiency by depositing BiVO₄ nanoparticles on TiO₂ nanospheres with a solvothermal method. The TiO₂-BiVO₄ heterostructure was characterized with various spectroscopic and microscopic techniques and was employed as a nanostructured support to cross-link DNA aptamer for constructing a visible-light driven PEC aptasensor. The TiO₂ nanospheres provided a biocompatible microenvironment, and the high surface area of the heterostructure enhanced the loading of aptamer molecules. The small energy gap of BiVO₄ improved the PEC property of the nanocomposite compared with the pure TiO₂ under visible-light irradiation. The advantages of the nanocomposite along with the high loading of recognition molecules greatly improved the sensitivity of the aptasensor. Using 17β-estradiol as an analyst model, the proposed PEC biosensor showed excellent analytical performance with high sensitivity, low detection limit of 0.022 pM, and high selectivity in a detectable concentration range of 0.1-250 pM, indicating the promising application of the designed TiO₂-BiVO₄ heterostructure in PEC biosensing.