Graphene-assisted titanium dioxide Z-mechanism photoelectrode as enzymatic glucose biosensor

Abstract

Highly exposed surfaces of anatase TiO2 crystals are of interest due to their excellent photogenerated electron–hole pair separation effect and high photocatalytic activity. In this work, a Z-mechanism biosensor with reduced graphene oxide (rGO) and anatase TiO2 nanocrystals combined with PDA (TiO2/rGO/PDA) was successfully synthesized. rGO was combined with the co-exposed (001) and (101) facets of TiO2 nanocrystals to construct a Z-mechanism in which rGO acts as an electron transport medium and provides a channel for the transfer of electrons, resulting in TiO2 nanocrystals with high photoelectron–hole pair separation efficiency and strong redox ability. The coated PDA polymer not only could absorb visible light but also has good stability and biocompatibility, which helps to increase the adsorption of target enzyme molecules. The TiO2/rGO/PDA/GOx biosensor with the Z-mechanism displays the sensitivity of 13.82 μA mM−1 cm−2 in 0.1M PBS solution (pH = 7.4) with a linear range of 0–3 mM and the LOD of 0.034 µM. In general, the application of the Z-mechanism in biosensors would provide a new orientation for the design of biosensors.