Study On Photoelectrochemical Sensor Based On Photoactive Material And Photocurrent Signal Sensitized Amplification

Due to the characteristics of high sensitivity,good selectivity,low detection limit and fast response,PEC sensor has been widely developed and studied in recent years,which shows great potential in biological analysis and clinical diagnosis.At present,in the research of photoelectrochemical sensor,a new type of photoactive material was used,combined with the sensitization and amplification technology of photoactive material,the cyclic amplification technology of target and DNA self-assembly amplification technology,and a simple and efficient target detection method was introduced.Because of its high utilization rate of light energy and strong electronic transmission ability,this sensor can significantly enhance the photocurrent signal.In this paper,based on the functional nanomaterials of energy level matching,the Co-doped photoactive materials are used to reduce its basic signal and DNA origami technology is used in the technology of new material immobilization mode,so as to realize the sensitization and amplification of photocurrent signal,improve the photoelectric conversion efficiency of PEC sensor,and realize the super sensitive detection of protein.The main contents are as follows:1.Cosensitization Strategy with Cascade Energy Level Arrangement for Ultrasensitive Photoelectrochemical BiosensorClassical PEC sensor commonly requires photoactive material and a sensitizer to produce a photocurrent response with the addition or generation of an electron donor or acceptor.However,there are still limitations,such as uneven distribution and poor stability of the added electron donor/acceptor.In order to solve this problem,we use the donor-acceptor nanomaterial poly{4,8-bis[5-（2-ethylhexyl）thiophen-2-yl]benzo[1,2-b:4,5-b′]dithiophene-2,6-diyl-alt-3-flfluoro-2-[（2-ethylhexyl）-carbonyl]thieno[3,4-b]thiophe ne-4,6-diyl}（PTB7-Th）as the photoactive material.In order to improve the photoelectric conversion efficiency of the biosensor,we use the cascade energy level arrangement cosensitization strategy,using perylene tetracarboxylate diimide（PDI）,fullerene(nano-C₆₀)and polyaniline（PANI）as sensitizers.The resulting PTB7-Th/PDI/nano-C₆₀/PANI cascade cosensitization structure with narrow energy level gradient（<0.54 eV）could effffectively improve electron transfer capability,obviously raise light energy utilization and signifificantly enhance photoelectric conversion effiffifficiency,leading to dramatically enhanced photocurrent response.Using prostate-specifific antigen（PSA）as a target model,the proposed PEC biosensor exhibited high sensitivity and excellent stability with a wide detection range.Moreover,the proposed PEC biosensor provides a cascade cosensitization strategy that could signifificantly improve PEC performances and open up a promising platform to establish high selectivity,stability,and ultrasensitive analytical techniques.2.Supersensitive Photoelectrochemical Aptasensor Based on Br,N-Codoped TiO₂Sensitized by Quantum DotsAs a classic inorganic semiconductor material,titanium dioxide（TiO₂）has been widely used in the PEC fifield because of its excellent photoelectric properties.However,the band width of TiO₂was wide（3.2 eV）,and there were still limitations such as high basic signal and limited sensitivity.In order to solve this problem,we use the co doping of bromine and nitrogen elements in TiO₂to reduce the band width and make it match with the sensitizer better.Here,we fabricated a novel photoelectrochemical（PEC）aptasensor based on Br,N-codoped TiO₂/CdS quantum dots（QDs）sensitization structure with excellent energy level arrangement for supersensitive detection of carcinoembryonic antigen（CEA）.The prepared Br,N-codoped TiO₂could reduce the energy bandwidth of TiO₂from 3.2 to 2.88 eV,which could dramatically reduce the basic signal and obviously broaden the absorption of light（400-700 nm）.In addition,the energy bandwidth of Br,N-codoped TiO₂（2.88 eV）matched well with that of CdS QDs（2.4 eV）,making CdS QDs an ideal signal enhancer for amplifying the photocurrent signal of Br,N-codoped TiO₂.More importantly,the constructed Br,N-codoped TiO₂/CdS QDs sensitization structure with narrow energy level gradient enabled the effffective promotion of electron-transfer capability and dramatic improvement of photoelectric conversion effiffifficiency.Simultaneously,a small amount of the CEA was transformed into substantial single-chain DNA（T-DNA）via exonuclease III（Exo-III）-assisted cycle strategy.This strategy prepared a new photoactive material to markedly improve photoelectric conversion effiffifficiency and initiated a new way to realize the highly sensitive PEC biomolecules detection.3.Construction of Photoelectrochemical aptasensor based on DNA origami technology and immobilization strategy of new photoactive materialsZinc oxide（ZnO）was a semiconductor oxide with a wide band gap,which has the characteristics of low background signal and stable photocurrent.However,due to its wide band gap,it is difficult to have a suitable sensitizer to match its energy band,and the traditional sensitizer of photoelectric materials has a small amount of solid load,a long distance between the photoelectric materials and the sensing interface,and the interaction distance between different photoelectric materials was difficult to control.In order to solve this problem,ruthenium compound with wide band gap was selected as sensitizer,and DNA origami technology was used to make the distance between ruthenium compound and photoactive material adjustable,and the fixed load was increased,which could effectively improve the photoelectric conversion efficiency and realize the sensitization and amplification of photocurrent signal.The aptasensor uses a small amount of DNA,highly ordered DNA origami technology,highly efficient immobilization of sensitizer ruthenium compounds,and a new immobilization method of photoelectric materials could sensitize zinc oxide with sensitizer ruthenium compounds,which significantly improves the utilization of light energy.