Expandable Application Of Strontium Titanate-based Nanomaterials In The Field Of Photoelectrochemical Biosensors

With the ever-growing demands of living standards,life science,environmental protection and food safety increasingly attract the attention of people.As a new and crucial direction of the bioanalysis technique,photoelectrochemical（PEC）biosensors promises to be a high-profile sensing method for their desirable combination of electrochemistry and photochemistry.Compared with other detection techniques in biomedical applications,（e.g.,fluorescent sensors,surface plasmon resonance sensors,surface enhanced Raman scattering techniques,electrochemical sensor,electrochemiluminescence sensor）,although these techniques have high accuracy,some of these techniques have some disadvantages,such as time-consuming operation,relatively complex instruments,larger sample volume,professional staff,and limited sensitivity.PEC detection signal mainly stems from the photo-to-electric conversion of photoactive materials.The appearance of new nanomaterials,which possesses special advantages in optical properties,electrical conductivity and magnetism,has injected new vitality into the development of PEC biosensor.Semiconductor nanostructures have a strong absorption capacity and an inherent electronic band structure.Innovations in semiconductor morphologies,structure or element can enhance charge transport and thereby facilitating high photo-electricity conversion efficiency.Sr Ti O₃ with a perovskite structure has a higher conduction band position than Ti O₂,indicating that Sr Ti O₃ has a smaller energy band shift and promotes the transfer of photogenerated electrons better.Thus,Sr Ti O₃(5–8 cm² V^-1 s^-1)has a higher electron mobility than Ti O₂(0.1–4.0 cm² V^-1 s^-1).Therefore,Sr Ti O₃ is more suitable to photocatalysis than Ti O₂.Strontium titanate materials are less used in PEC biosensors.Therefore,this research focuses on the performance of strontium titanate nanomaterials in PEC biosensors.（1）The titanium mesh with a three-dimensional hole structure has excellent solution diffusion efficiency on the electrode surface,which is very beneficial to the enzymatic reaction process in the PEC sensor.Titanium wire mesh is selected as the electrode substrate.Anatase titanium dioxide nano-arrays are etched on the surface of the titanium wire mesh by anodizing method,and then hydrothermal method is used to grow in situ using strontium hydroxide octahydrate as the source of strontium.The titanium dioxide on the surface of the titanium mesh is completely converted into strontium titanate.So far,a strontium titanate nano-array photoelectrode with three-dimensional cavity junctions has been successfully prepared.Subsequently,the electrode is prepared into a PEC enzymatic glucose biosensor,which has higher stability and durability,and can expose more abundant active sites for enzymatic reactions.In glucose detection,good results have been achieved,with a wide linear range of 0-20 m M,a low detection limit of 0.025 m M and a high sensitivity of 5.97μA m M^-1 cm^-2.This work successfully fixed strontium titanate on the electrode surface and demonstrated excellent PEC performance.（2）The immobilization of the enzyme and the activity of the enzyme on the electrode directly affect the efficiency of the enzymatic reaction.In the second work,we used polydopamine（PDA）to modify the surface of the strontium titanate nanoarray with a three-dimensional pore structure,and constructed a highly sensitive photoelectrochemical biosensor with efficient immobilization of enzymes.The deposition solution was prepared by dissolving dopamine hydrochloride in PBS with PH=6,and then using the ultraviolet light bath method to carry out the light deposition experiment,fixing the polydopamine on the electrode surface.The super adhesion ability of polydopamine provides a strong guarantee for the immobilization of enzymes.More enzyme loading makes the three-dimensional hole structure Sr Ti O₃/PDA/GOx glucose biosensor exhibit more excellent sensing performance,with a higher sensitivity of 8.9μA m M^-1 cm^-2,and a linear range of 0-20 m M.The limit is0.017 m M.This work explored the effect of PDA on enzymatic reactions.（3）The high charge separation efficiency is conducive to improving the sensing performance of the electrode.In further research,we used gold nanoparticles as the electron cloud bridge to construct a three-dimensional hole structure Sr Ti O₃/Au/PDA photoelectrode with efficient photogenerated electrons.Used for glucose biosensor.First,the gold nanoparticles are uniformly loaded on the surface of the strontium titanate electrode by the microwave assisted method.Then,the polydopamine is uniformly grown on the top of the electrode by the light bath deposition method.The gold nanoparticles effectively improve the blocking of electronic transmission at the interface between strontium titanate and polydopamine,thereby enabling efficient separation of photo-generated charges,significantly improving the sensing performance of the glucose biosensor,with an ultra-high sensitivity of 23.7μA m M^-1 cm^-2,the linear range is 0-20 m M,and the detection limit is0.012 m M.This work explored the impact of high-efficiency photo-generated charge separation on sensing performance,and also provided new ideas for the further development of high-performance biosensors.