Photoelectrochemical Biosensing Based On Lead-free Perovskite Functional Composites

Photoelectrochemical（PEC）biosensing,which possesses reduced background noises and thus higher sensitivity than traditional optical and electrochemical determination owing to the complete separation of the input（light excitation）source and output（electrical detection）signal,is a newly emerging and vibrantly developing sensing technology for application potential in life analysis,clinical testing and other fields.Appropriate photoactive materials are crucial for improving the photoelectric conversion performance and constructing highly sensitive photosensors.Perovskite materials,have recently become a research hotspot owing to their excellent optical and electrical properties,such as narrow-band emission,tunable band gap,high charge mobility,high extinction coefficient,as well as low cost and facile synthesis.However,the most extensively studied Pb-contained perovskites may suffer from their toxic restrict their application in the field of PEC biosensing.Lead-free perovskites have become a new favorite in the field of perovskite research because of their good environmental stability and non-toxic properties.However,their photoelectric conversion performance is still far behind that of lead-based perovskites.Therefore,the new strategy to modify lead-free perovskite and prepare novel lead-free perovskite functional composites with environmental friendly and high optoelectronic activity is of great significance for its application in the field of PEC biosensing.In this thesis,a series of novel photoelectric active lead-free perovskites were designed and prepared Their structure was adjusted and modified by compounding with other materials to further improve the optoelectronic properties and stability,which were used to construct a series of photoelectrochemical（PEC）biosensorsfor detection of hydrogen peroxide（H₂O₂）and 8-hydroxy-2′-deoxyguanosine（8-OH-d G）.The specific research contents are as follows:1.Gold nanoparticle-attached Pb-free perovskite Cs₃Bi₂Br₉QDs/BiOBr heterostructures for H₂O₂photoelectrochemical biosensing A photoelectrochemical（PEC）sensing platform based on gold nanoparticle（Au NPs）attached lead-free perovskite Cs₃Bi₂Br₉QDs/BiOBr heterostructure was constructed for highly sensitive and selective biosensing of H₂O₂.In this work,the Cs₃Bi₂Br₉QDs/BiOBr heterostructures with high photoelectric activity and stability were successfully obtained by water treatment producing BiOBr-encapsulated Cs₃Bi₂Br₉QDs.The decoration of Au NPs can initiate a surface plasmon resonance enhancement effect to further effectively improve the PEC performance.The resulting Au NPs/Cs₃Bi₂Br₉QDs/BiOBr-modified photoelectrode presents efficient photoelectrochemical performance for H₂O₂sensing in a wide linear detection range from 0.002 to 200μM with a very low detection limit down to 0.89 n M.In addition,the sensor also showed excellent stability,acceptable reproducibility and satisfactory selectivity.Moreover,the promising platform is capable of monitoring H₂O₂released from drug-stimulated Hep G2 cells,indicating its promising potential in biological applications.This work proposed a facile photoelectrochemical sensing strategy,which has important research value for PEC biosensing applications in the study of lead-free perovskite heterostructures.2.8-OH-d G photoelectrochemical biosensing based on lead-free double perovskite Cs₂AgInCl₆/graphene compositesA photoelectrochemical（PEC）sensing platform based on graphene-supported lead-free double perovskite Cs₂AgInCl₆was constructed for highly selective biosensing of8-hydroxy-2′-deoxyguanosine.The two-dimensional planar structure of graphene can provide a broad platform for loading Cs₂AgInCl₆.The composite material with Cs₂AgInCl₆uniformly loaded on the surface of graphene was prepared by a simple one-pot method,which were used to construct Cs₂AgInCl₆/graphene modified photoelectrodes and investigatesaturated oxygen and 8-OH-d G.The study showthat Cs₂AgInCl₆/graphene can generate a better cathodic photocurrent response than Cs₂AgInCl₆in the oxygensaturatedelectrolyte,And a biosensing strategy based on photogenerated hole oxidation was proposed forthe detection of electron donor of 8-OH-d G.The resulting Cs₂AgInCl₆/graphene-modified photoelectrode presents efficient photoelectrochemical performance for H₂O₂sensing in a wide linear detection range from 0.005 to 1000μM with a very low detection limit down to 3.3 n M.In addition,the sensor also exhibited excellent stability and selectivity,indicating that the constructed sensing platform has promising potential in the biological field.This work shows that the good dispersion of graphene on Cs₂AgInCl₆can greatly improve the photoelectric activity of Cs₂AgInCl₆,and its high surface area can enrich the dissolved oxygen and 8-OH-d G.Thus,the electron donor-acceptor-based photoelectrochemical sensing strategy is of great significance for the study of lead-free double perovskites in PEC biosensing applications.