Based On The Preparation Of Tin Dioxide Nanocomposite Materials And The Construction Of Photoelectrochemical Sensors

Photoelectrochemical?PEC?is a new analytical and detection technology which takes light as input signal and establishes the correlation between the target analyte and the output electrical signal.Combining the advantages of photochemistry and electrochemistry,PEC can well separate excitation signal and detection signal.With some cyclic amplification strategies,it can achieve very high detection sensitivity,especially in biosensor analysis.Tin dioxide?SnO₂?nano semiconductor materials are widely used in the photoelectrochemical research because of the advantages such as convenient preparation,relatively stable chemical properties,easy to control morphology,transparent film-forming and so on.However,for photoelectrochemical detection,SnO₂ has wide band gap and low photoelectric conversion efficiency,so it is difficult to be directly used in photoelectric detection.Narrow band gap semiconductors have strong absorption in the visible region.In the composite semiconductors with matched energy bands,they can realize the efficient transfer of photogenerated electrons,promote the effective separation of h⁺/e^-pairs,and generate high photoelectric signals.The interface between noble metals and semiconductors has the dynamic advantage of Schottky barrier,which can promote the plasma driven charge separation and effectively inhibit the recombination of them with the thermal holes left on semiconductors.Therefore,one of the goals of our work is to improve the photoelectric conversion efficiency of wide band gap semiconductor nanomaterials by using the plasma effect of noble metal nanoparticles or the narrow band gap semiconductor.On this basis,for different chemical or biological molecules,we also try to design different reaction systems or modify the electrode surface to ensure the specificity of detection.The three specific tasks involved are as follows:1.SnO₂/TiO₂ nanocomposite modified with Au NPs was used to developphotoelectrochemical method for detecting sialic acid?SA?In this work,a PEC sensor based on SnO₂/TiO₂ modified with Au NPs was constructed to detect sialic acid in serum.The SnO₂ layer was fixed on the surface of ITO electrode by spin coating and sintering.Then,TiO₂ nanofibers were prepared on ITO/SnO₂ electrode surface by electrospinning to form SnO₂/TiO₂ heterojunction.Au NPs was loaded on the surface of ITO/SnO₂ electrode by ion sputtering instrument.As for 4-mercaptobenzoboric acid?MPBA?,it was fixed on the electrode surface by gold sulfur bond.In the presence of glucose oxidase,SA reacts with MPBA on the electrode surfaceforming cyclic borate and increasing the electrode interface impedance.It reduces the background photocurrent of the electrode.with this,the correlation between SA concentration and photocurrent intensity is established.Among them,Au NPs can not only improve the recognition of MPBA,but also improve the photoelectrochemical behavior and broaden the absorption of visible light.Under the illumination of visible light,the LSPR effect of Au NPs is excited to produce hot electrons,which are transferred to the conduction band of TiO₂.Because of the staggered type II heterojunction formed on the SnO₂/TiO₂ interface.The Fermi energy level of TiO₂ is higher than that of SnO₂.Because of its small work function,the electrons of TiO₂ conduction band transfer to the conduction band of SnO₂,and the holes of SnO₂ valence band transfer to the valence band of TiO₂.The efficient charge separation improves the carrier lifetime and the efficiency of the interface charge transfer,which shows that the recombination of photogenerated carriers is greatly inhibited in the SnO₂/TiO₂ heterostructure.In addition,TiO₂ nanofiber structure has a large specific surface area,which can provide a large number of binding sites to fix recognition molecules.It can realize the quantitative detection of SA.2.A photoelectric competition system was constructed based on Au/SnO₂nanocomposites for the detection of phthalate compoundsIn this work,?6-mercapto-6-deoxy?-?-cyclodextrin??-CD?were immobilized on the surface of SnO₂/Au composite nanomaterials by self-assembly of thiols.Ru?bpy?₃²⁺was taken as the photoelectric signal molecule,hydroquinone?HQ?as the electron donor and the competitive agent of PAEs.The cyclodextrin cavity on the electrode surface was first filled with hydroquinone,which can initiate the Ru³⁺to Ru²⁺cycle reaction,thus enhancing the photocurrent.When PEAs present,it can replace the hydroquinone in the cyclodextrin cavity,causing the photocurrent drop.The correlation between PAEs concentration and photocurrent intensity was established.The response of the sensor to DEHP was investigated.The linear range was 10^-9-10^-55 M,and the lowest detection concentration was 10^-99 M.The sensor was applied to the determination of PEAs in wine samples,findingthe detection results are similar to those of the classical HPLC-MS,which shows that the sensor has high accuracy and good practical application prospects.3.Photoelectrochemical sensors for highly sensitive detection of ferritin based on photo-stable SnO₂/Bi₂S₃ composite nanomaterialsIn this work,ITO/SnO₂ electrode was prepared by spin coating-sintering method,and then Bi₂S₃ composite nanorod array was prepared on the surface of the ITO/SnO₂electrode by continuous ion layer adsorption reaction?SILAR?.Bi₂S₃ is an n-type semiconductor with a direct band gap of 1.3–1.7 eV,which has good absorption activity for visible light.In addition,Bi₂S₃ has band structure matching with SnO₂,which can effectively form heterojunction with SnO₂ and improve its photoelectric conversion efficiency.Under the irradiation of visible light,the photogenerated electrons from Bi₂S₃ can be transferred to SnO₂ rapidly,which can promote the separation of photogenerated electrons and holes,and improve the photoelectrochemical?PEC?activity of SnO₂.Hydroquinone?HQ?has strong reducibility.It can be used as an electronic donor to participate in the photoelectric conversion process of SnO₂/Bi₂S₃ composite nanomaterials,which makes the system produce high photoelectric signal.Ferritin is a kind of metal protein containing iron???,which has a certain degree of oxidation,so it can compete to consume HQ in the electrolyte,resulting in the decrease of photocurrent.In addition,due to the large molecular weight of ferritin,it is easy to increase the electrode surface impedance,resulting in the decrease of photocurrent.The correlation between the concentration of ferritin and the intensity of photocurrent was established.The experimental results show that in the range of 0.1-1000 ng mL^-1,there is a good linear correlation between the photocurrent intensity and the logarithm of ferritin concentration.So we can detect ferritin with super sensitivity.