Dye-Sensitized NiO Photocathode For Photoelectrochemical Bioanalysis

Photoelectrochemical（PEC）analysis technology exhibits many advantages such as high sensitivity,fast response capability,easy miniaturization of instruments.Based on these advantages,PEC analysis technology has been widely applied in environment,food,and biomedical science.The working electrodes used for PEC analysis are divided into two types,including photoanode based on n-type material and photocathode based on p-type material.Currently,widely studied photoanode exhibits high photoelectric conversion rates,but it shows poor detection selectivity due to its susceptibility to various reducing substances.Photocathode exhibits outstanding anti-interference ability and better selectivity than photoanode.As a commonly used photocathodic material,NiO exhibits a wide band gap（3.5 e V）and low utilization of visible light.In order to improve its performance,dyes are often used to sensitize it.At present,the commonly used dyes are mainly metal organic complexes,such as iridium（III）complexes.The lack of absorption of these dyes in the visible light region limits their practical application.In order to improve their light absorption characteristics,cyclometalated iridium（III）complexes and Cd Se quantum dots were designed and synthesized respectively to sensitize NiO,which improved the photoelectric conversion efficiency.And they were used to construct PEC biosensing platform,achieving sensitive detection of micro RNA（mi RNA）in biological systems.The main research contents are as follows:（1）An iridium（III）complex-sensitized NiO photocathode was constructed for PEC bioanalysis,and the sensitive detection of mi RNA-133a was realized.Firstly,an iridium complex（ppy-PH）₂Ir（phen-BDP）was synthesized by introducing the organic fluorescent group Bodipy into the cyclometalated ligand（ppy-PH=phenyl pyridine with methyl phosphate,phen-BDP=Bodipy with phenanthroline）,which exhibits strong visible light absorption at 506 nm withεover 50000 M^-1 cm^-1.The complex was assembled on the surface of NiO electrode,and a dye sensitized NiO photocathode was constructed and used for the detection of mi RNA.When mi RNA is present,it can trigger hybrid chain reaction（HCR）,forming a DNA super double stranded structure on the electrode surface,and inserting a large number of hydrogen peroxide mimetic enzyme manganese porphyrin（Mn PP）.In the presence of H₂O₂,4-chloro-1-naphthol（4-CN）was catalyzed to form benzo-4-chlorophenol（4-CD）precipitate,hindering electron transfer and effectively quenching PEC signals,achieving photoelectric response to mi RNA.The linear range is 0.1 f M～1 n M,and the detection limit is 66.2a M（3σ）.（2）CdSe quantum dots（QDs）sensitized NiO photocathode was constructed for mi RNA detection.Cd Se QDs were synthesized,which reached 495 nm in the visible light absorption region.By introducing H1 modified by quantum dots into the NiO electrode,Cd Se QDs sensitized NiO photocathode was constructed and used for the detection of mi RNA.By introducing c DNA onto the photoelectrode and opening H1 to insert the molecular quencher manganese porphyrin,electron transfer was hindered,and the PEC signal was quenched.When mi RNA was present,the translysis activity of CRISPR/Cas12a enzyme was activated,achieving a change in PEC signal.The photocathode sensing platform exhibits a linear range of 0.1 f M～10 n M and a detection limit of 0.26 f M for miRNA（3σ）.