Study On Design And Fabrication Of New Photoelectrochemical Material For Biosensing Platform

Photoelectrochemical?PEC?biosensor,as an efficient and sensitive analysis method,combines the advantages of optical analysis and electrochemical analysis,and provides powerful technical support for the diagnosis of tumors.In the construction of PEC biosensors,the design of highly active photoelectric materials and sensing strategies is the key to improving sensor performance.The photoelectric conversion efficiency of the electrode material directly affects the sensitivity and response speed of the sensor,and the signal amplification technology can further improve the detection performance of the PEC biosensor.Therefore,this paper designs a series of new nanomaterials with high photoelectric conversion efficiency by construction of built-in electric field,change of light absorption efficiency of materials,change of electron transfer path and other strategies.Finally,photoelectrochemical biosensors were fabricated with the aid of target conversion and various nucleic acid amplification technology to achieve sensitive detection of tumor markers.The specific work is as follows:1.A"signal off"Photoelectrochemical Biosensor By Porous Carbon Spheres to Quench g-C₃N₄ by Adjusting the Light Absorption EfficiencyThe decrease of photocurrent signal after target recognition determines the sensitivity of"signal off"photoelectrochemical biosensor,while the quenching efficiency of quench agent determines the decreasing degree of photocurrent signal.Traditional photocurrent quenchers are usually materials with poor conductivity.They can enhance steric hindrance and inhibit electron transfer.However,the quenching efficiency is limited and needs to be further improved.Therefore,a novel"signal off"PEC biosensor was constructed based on g-C₃N₄ as a photoactive material and porous carbon sphere as an effective quenching agent of photocurrent.Due to its excellent light absorption capacity,the porous carbon spheres can effectively quench the photocurrent signal of g-C₃N₄ by two reasons:?a?competitive light absorption and?b?competitive electron donor to reduce the number of photogenerated electrons and holes,resulting in low charge separation efficiency.This new quenching mechanism is different from the previous quenching mechanism based on steric effect.The PEC biosensor showed a linear response at VEGF₁₆₅65 concentrations ranging from 10 fmol/L to 10 nmol/L,with a detection limit of 3 fmol/L.The method of reducing photocurrent signal by adjusting light absorption efficiency will provide a new direction for the design of other PEC biosensors.2.A Photoelectrochemical Biosensor Based On Ti₃C₂-BiVO₄ as Photoactive Material and Dual Signal Amplification TechnologyIn the previous work,g-C₃N₄ was used as the photoelectric active material,while the photocurrent signal of single photoelectric active material was low because of the high recombination rate of electron and hole.At present,the common sensitization system is usually constructed by combining a variety of photosensitive materials to improve the photocurrent signal.However,how to find cascade sensitizers with matching energy level gradient and strong interface contact is still a problem.We composite Ti₃C₂ with good conductivity with BiVO₄,and the built-in electric field generated by Ti₃C₂-BiVO₄ Schottky structure can effectively inhibit the recombination of photogenerated electron hole pairs,thus enhancing the photoelectric signal of BiVO4.Then,a photoelectrochemical biosensor was constructed based on Ti3C2-Bi VO4 as the photoactive material and the target induced double signal amplification strategy.The design of Schottky structure can not only improve the photoelectric conversion efficiency of photoelectric materials without considering the energy level matching,but also provide good interface contact to promote electron transfer,so as to generate higher photocurrent signal.In order to further improve the detection sensitivity,T7exonuclease assisted double signal amplification strategy was adopted to convert a small amount of target protein into a large amount of DNA.Finally,DNA double-stranded structure can immobilize a large number of organic dye methylene blue,so as to effectively enhance the photocurrent signal of Ti3C2-BiVO4.The detection range of this PEC biosensor for VEGF₁₆₅65 is 10 fmol/L to 100 nmol/L,and the detection limit is3.3 fmol/L.The biosensor provides a new platform for high-sensitivity detection of biomarkers in clinical diagnosis.3.A Highly Sensitive Photoelectrochemistry Biosensor Based On Bi₂WO_6-XS_X Nanoparticles as Photoactive MaterialsIn the last work,we used the built-in electric field generated by the Ti₃C₂-BiVO₄Schottky heterojunction to improve the photocurrent signal.However,the interface between the two materials in Schottky will increase the electron transmission distance,so the increase of photoelectric performance is limited.In order to further improve the PEC performance,this work changes the energy band structure of the material through doping to improve the photoelectric conversion efficiency.In this work,sulfur-doped bismuth tungstate defective nanomaterial,Bi₂WO_6-XS_X,was synthesized by hydrothermal method.By introducing S into Bi₂WO₆,the band width of Bi₂WO₆ can be changed and the light absorption can be enhanced to promote the separation of electrons and holes,thus effectively enhancing the photocurrent.The synthesis of Bi₂WO_6-XS_X provides a novel photoactive material for the construction of PEC biosensor.In order to further improve the sensitivity,a large amount of DNA was released by the double-strand specific nuclease?DSN?-induced target amplification technology,then large amount of quench agent SiO₂ was immobilized to reduce the photocurrent signal,so as to realize sensitive detection of the target.The PEC biosensor has good analytical performance for miRNA-141 in the range of 1 fmol/L to 10 nmol/L,and the detection limit is 333 amol/L.