Study On The Construction Of Photoelectrochemical Biosensor Based On Novel Sulfide Composites

Photoelectrochemical(PEC)bioanalysis technology,as a booming emerging technology,has been rapidly developed in the fields of photovoltaic,photocatalysis and biosensing due to its advantages of low cost,simple instrument and simple operation.In photoelectrochemical biosensors,the photoelectrochemical process refers to the redox reaction of the ground state or excited state of molecules or ions caused by the electronhole pairs formed at the interface when the photoelectric material absorbs photons under the excitation of light,and electron separation and transfer occurs.In order to achieve efficient PEC biosensor analysis,the selection of more excellent photoactive materials has always been the focus of researchers.In addition,apart from the selection of photoelectric materials,the introduction of high-efficiency nucleic acid signal amplification strategy can further accurately detect the target,so as to effectively improve the detection sensitivity of photoelectrochemical biosensor.Therefore,it is of great significance to find photoelectric substrate materials with impressive PEC performance and effectively amplify the photoelectric response combined with nucleic acid signal amplification strategy to improve the detection performance of PEC biosensors.In this work,a series of photoelectrochemical biosensors with excellent analytical and detection performance have been constructed around the preparation of novel sulfide composite materials and combined with a variety of nucleic acid signal amplification strategies,realizing the ultrasensitive detection of nucleic acid molecules.The main research contents are as follows:1.Ultrasensitive Photoelectrochemical Platform Based on High-Efficient Photoactive AuNPs@Bi2S3/Bi2O3 Nanocomposite for Detection of MicroRNA-21As an n-type metal chalcogenide inorganic semiconductor material,Bi2S3 is a promising photoelectrochemical sensitizer with a non-toxicity,tunable narrow band gap(1.3-1.7 eV)and strong visible light absorption ability.Unfortunately,Bi2S3 is still suffered from the fast recombination of photoexcited electron-hole pairs,leading to a relatively low photocurrent signal and hindering its direct application in PEC biosensing.In this work,wide band gap Bi2O3(2.80 eV)is introduced.Because Bi2S3 and Bi2O3 have an admirable energy band matching,and narrow band gap,Bi2S3 can effectively sensitize wide band gap Bi2O3 to obtain a marvelous photocurrent response.At the same time,gold nanoparticles(AuNPs)are introduced to form a novel AuNPs@Bi2S3/Bi2O3 nanocomposite.The photocurrent signal of AuNPs@Bi2S3/Bi2O3 is 8 times higher than that of Bi2S3/Bi2O3,which is due to the surface plasmon resonance(SPR)effect of AuNPs providing more photoelectrons,thus increasing the photoelectric conversion efficiency of AuNPs@Bi2S3/Bi2O3.In addition,with the assistance of catalytic hairpin assembly(CHA)and Nt.BsmAI enzyme-assisted cycle amplification strategy,a large number of doublestranded DNA(dsDNA)was generated to immobilize the simulated enzyme manganese porphyrin(MnPP),which can catalyze 4-chloro-l-naphthol(4-CN)to produce benzo-4chloro-hexadienone(4-CD)precipitation in the presence of H2O2,thus achieving the sensitive detection of the target miRNA-21.The designed PEC biosensor demonstrates a perfect linear relationship between the logarithm of target concentration and photocurrent response range from 100 amol/L to 10 nmol/L with a lower detection limit of 34 amol/L.Importantly,this strategy provides a novel sulfide nanocomposite AuNPs@Bi2S3/Bi2O3 as photoactive material to construct an ultrasensitive PEC biosensor for biological analysis and early disease diagnosis.2.A Photoelectrochemical Biosensor Based on Ti3C2Tx MXene/Ag2S as a Novel Photoelectric Composite for Ultrasensitive Detection of MicroRNA-141Silver sulfide(Ag2S)is widely used in PEC field as a sensitized semiconductor material with narrow band gap,low toxicity and excellent chemical stability.However,owing to its low initial photocurrent signal and small visible light absorption range,its application in PEC field is limited.In order to solve this problem and improve the photoelectric conversion efficiency of photoactive materials,a two-dimensional(2D)material Ti3C2Tx MXene is selected.Since the discovery of Ti3C2Tx MXene,it has attracted popular attention attributed to its excellent conductivity,large specific surface area and adjustable band gap structure.In this work,Ag2S and Ti3C2Tx MXene are combined to form Ti3C2Tx MXene/Ag2S composite.Based on the excellent metal conductivity of Ti3C2Tx MXene,it can shorten the electron transmission path,effectively reduce the recombination rate of electron-hole pairs,and prominently enhance the photocurrent signal.At the same time,streptavidin(SA)is used as a scaffold to assemble DNA tetrads,and a spherical DNA structure is constructed by the nonlinear hybrid chain reaction(HCR)triggered by the single-stranded S2.Thionine,as a sensitizer,can be extensively embedded into the double-stranded structure to further enhance the photocurrent response.Hence,a novel photoactive sulfide material Ti3C2Tx MXene/Ag2S with admirable photocurrent signal is prepared to construct a PEC biosensor for ultrasensitive detection of biomarker miRNA-141.The proposed PEC biosensor has a marvelous analytical detection performance from 100 amol/L to 100 pmol/L with a satisfactory detection limit of 34 amol/L.This strategy provides a versatile photoactive material for the construction of PEC biosensor,which can be used for the sensitive detection of biomarkers and has potential application value in disease diagnosis.