Design And Construction Of TiO₂-based Photoelectrodes For Photoelectrochemical Glucose Sensor Application

Glucose,as the main substance for energy,plays a vital role in the human body.With the continuous improvement of human living material level,the number of diabetes induced by the increase of blood sugar content has been increasing rapidly year by year,and it has developed into a global problem endangering human health.Therefore,the development of simple,fast,and highly sensitive glucose detection technology is of great significance to the monitoring and prevention of diabetes.As a simple,fast and efficient biological detection method,photoelectrochemical（PEC）sensors have been widely used in various biological detection fields.The core component of the photoelectrochemical detector is the semiconductor photoelectrode,so the development of efficient semiconductor photoelectrode is the core issue of its future development.Among many semiconductor materials,TiO₂ has many advantages,such as strong photocatalytic activity,good stability,non-toxicity,high morphology tunability,and good biocompatibility.It is considered as an ideal semiconductor material for constructing photoelectrochemical biosensors..However,TiO₂ has a large forbidden band width（>3.0 e V）,and only absorbs and utilizes ultraviolet light that accounts for less than 5%of the solar spectrum.At the same time,the photo-generated charge in TiO₂ is easy to recombine,which affects its photocatalytic activity.Carbon-based nanomaterials have good electrical conductivity（such as graphene as a two-dimensional material with ultra-high charge mobility）and biocompatibility.The combination with TiO₂ can effectively promote the transport and separation of photo-generated charges,and can be oxidized with glucose.The enzyme forms a good charge transfer interface.Au nanoparticles have a strong absorption of visible light due to the tunable surface plasma oscillation effect,and the combination with TiO₂ can effectively expand the light absorption range.Based on the above analysis,in order to obtain a PEC glucose biosensor with high sensitivity,this paper proposes strategies such as TiO₂ morphology adjustment,carbon-based nanomaterials composite,and Au nanoparticle modification to improve the two limiting factors,which are narrow light response range and easy recombination of photo-generated charges.Specific research content includes:1)Controlled preparation of TiO₂ nanorod array photoelectrode and its application in photoelectrochemical glucose biosensorOne-dimensional nano-single crystal structure（nanorods,nanotubes,nanowires,nanoribbons,etc.）arrays can achieve the orthogonalization of the direction of light incidence and the direction of carrier diffusion,ensuring sufficient light absorption,and effectively promoting photo-generated charges.Transport and separation are regarded as an ideal structure for photoelectrode design.In this experiment,a one-dimensional TiO₂ nanorod single crystal array was synthesized on the FTO substrate by hydrothermal method.After hydrochloric acid treatment,the contact area with glucose oxidase was increased to facilitate the adsorption of glucose oxidase,thereby improving the absorption of glucose.The sensitivity of the response.By optimizing the morphology and subsequent acid treatment parameters（the ratio of water to hydrochloric acid is 1:1）,the high detection sensitivity of the TiO₂ nanorod single crystal array photoelectrode for glucose is realized,and the detection sensitivity can reach within the linear response range of 0.1-1.4 m M 28.53μA m M^-1cm^-2.2)Preparation of Au@C/TiO₂/FTO Composite Photoelectrode and Its Application in Photoelectrochemical Glucose BiosensorCarbon materials have the advantages of high stability,low cost,high conductivity and excellent biocompatibility,and they can improve the adsorption of enzymes,so they can effectively increase the detection range and sensitivity of the TiO₂-based photoelectrochemical sensor.Because Au nanoparticles have surface plasmon resonance absorption in the visible light region,they can be used as sensitizers to extend the light absorption range of TiO₂-based photoelectrodes,and Au can achieve better biological detection of many biomass.In this experiment,the TiO₂ nanorod array was synthesized by hydrothermal method,and then Au nanoparticles and carbon shell layer were deposited on the surface of the TiO₂nanorod array using secondary hydrothermal method.The introduction of Au nanoparticles and carbon shell layer can expand light absorption and effectively promote the transport and separation of photo-generated charges.Glucose photoelectrochemical biosensor was constructed by modifying glucose oxidase on the surface of Au@C/TiO₂/FTO composite photoelectrode.The biosensor has a low detection limit（0.049 m M）,linear measurement range and sensitivity of 0.1-1.6 m M and 29.76μA m M^–1cm^-2,respectively,and has good stability.3)Construction of Au/r GO/Au/TiO₂/FTO composite photoelectrode and its application in photoelectrochemical glucose biosensorAu nanostructures have good catalytic activity for glucose oxidation,and the efficiency of PEC reaction can be effectively improved by depositing Au nanoparticles on the surface of TiO₂ photoelectrode as a promoter.Reduced oxide graphene（r GO）has high conductivity and can provide a fast transport path for electric charges.At the same time,its large surface area and abundant functional groups can effectively immobilize glucose oxidase and improve stability,and effectively prevent the agglomeration of supported Au nanoparticles,helping to improve the chemical stability and catalytic activity of the photoelectrochemical biosensor.In this experiment,we used TiO₂ nanorod single crystal array treated with hydrochloric acid as the substrate,and deposited Au nanoparticles and r GO on its surface by electrodeposition to obtain Au/r GO/Au/TiO₂/FTO composite photoelectrodes.The glucose oxidase was modified on the surface of Au/r GO/Au/TiO₂/FTO composite photoelectrode to construct a glucose photoelectrochemical biosensor.The sensitivity of the biosensor in the linear response range of 0.1-3.2m M can reach 25.199μA m M^-1cm^-2.