Photoelectrochemical Glucose Biosensor Based on the Heterogeneous Facets of Nanocrystalline TiO₂/Au/Glucose Oxidase Films

TiO₂ single-crystal nanomaterials with highly reactive surfaces have attracted widespread attention due to their fundamental aspects and industrial applications. However, many previous studies have ignored the poor photoelectric efficiency of TiO₂ nanomaterials originating from a mismatch in the diffusion distance of electrons and holes as well as migration rates of holes and electrons. Therefore, suppression of hole migration could enhance the photoelectrochemical performance of TiO₂. In this work, single-crystal anatase TiO₂ nanomaterials with (001) facets were successfully prepared. The results suggested that some (101) facets were retained by the modified fluoride ion crystal facet control process. Subsequently, fluorine-free and Au-containing crystal facets were obtained by annealing and electrochemical deposition. In addition, the propensity for adsorption of Au on a TiO₂ (101) surface was verified by first-principles quantum chemical calculations. Electrochemical impedance spectroscopy and UV–visible spectrophotometry showed the presence of a large area (001), conducive to better enzyme affinity. Biosensors prepared by carrier self-separation derived from natural different facets and Au nanoparticles (TiO₂ (001)/Au/GOx) achieved high sensitivities reaching 16.86 μA mM^–1 cm^–2, an extended linear range (0.01–3 mM), and a low detection limit (0.83 μM). In summary, the proposed route allowed for the first time the use of nanocrystal engineering in the construction of glucose biosensors with satisfactory performances, which is promising for the future fabrication of high-performance biosensors.