Application Of Nanomaterials In Photoelectrochemical Immunoassay And Electrocatalytic Hydrogen Production

Nanomaterials branches include organic-inorganic hybrid materials（MOF materials）and organic conductive polymers.Currently,MIL-101（Cr）,a representative material of MOF materials,is mostly used as a supporting matrix to disperse other materials in the field of photoelectrocatalysis.But its own photoelectric properties have not been discussed too much and it has not been developed in the photoelectrochemical（PEC）immunoassay field.Similarly,polythionine,an organic conductive polymer,has not been studied in the field of PEC immunoassay and electrocatalytic hydrogen production.Therefore,this article mainly reveals the semiconducting properties of MIL-101（Cr）and applies it to the preparation of dual photocurrent signal PEC immunosensors and cathodic PEC immunosensors,and explores the role of polythionine in the field of cathodic PEC immunosensors and electrocatalytic hydrogen production.The research content and related results are as follows:（1）The compound MIL-101（Cr）&Cd Se（M&C）is prepared by a simple ultrasonic mixing method,and is used to prepare a dual photocurrent signal PEC immunosensor,which realizes the detection of human alpha-fetoprotein（AFP）.Thereinto,we found that MIL-101（Cr）can generate anode photocurrent and cathode photocurrent under different voltages,but the dual photocurrent signals are too weak.Therefore,we introduced Cd Se quantum dots（QDs）to improve the dual photocurrent signal response.It is worth noting that the electron transfer path between MIL-101（Cr）and Cd Se QDs in M&C may switch between“Z-type”and“Ⅱ-type”by adjusting voltage.Moreover,benefiting by the dual signals,the proposed sensor can not only perform sensitively quantitative detection of AFP,but also can intuitively estimate the accuracy and reliability of the test result by determining whether the corresponding relationship of“cathode photocurrent-analyte concentration-anode photocurrent”is established.The linear ranges of the sensing electrodes as cathode and anode are the same,both from 0.1 to 300 ng m L^-1.The limit of detection（LOD）is 0.082 ng m L^-1（S/N=3）when it used as an anode,and the LOD is 0.054 ng m L^-1（S/N=3）when it served as cathode.Furthermore,this sensor showed acceptable stability,reproducibility,specificity,and feasibility of detecting AFP in human serum,which has broad development prospects in the early clinical diagnosis.（2）A cathodic PEC immunosensor based on polythionine,MIL-101（Cr）and Cu₂O photosensitive materials was successfully prepared and furtherly applied to the detection of prostatic antigen（PSA）.Thereinto,we used simple cyclic voltammetry（CV）to electropolymerize polythionine on MIL-101（Cr）,and the obtained polythionine/MIL-101（Cr）was used as the sensing substrate.Cu₂O is combined with PSA antibody Ab₂as the signal amplification probe of the sensor.It is worth noting that the possible electron transfer path between polythionine and MIL-101（Cr）is“Ⅱ-type”,while the path between polythionine/MIL-101（Cr）and Cu₂O is"Z-type".The electron-hole transfer between materials effectively improves the photoelectric conversion efficiency,thereby significantly amplifying the response of the cathode photocurrent signal generated when PSA is detected.Therefore,the developed sensor shows a wide linear range(0.1～100 ng m L^-1)and a low detection limit(0.04 ng m L^-1,S/N=3)for the detection of PSA.In addition,the sensor has high stability,reproducibility and selectivity,and shows great potential in clinical applications.（3）In the process of preparing polythionine,it was found that it may have a certain ability of electrocatalytic hydrogen production.Hence,we proposed a novel polythionine/Au/Co₃O₄composite as HER catalyst.It is prepared by a two-step strategy,in which the Au/Co₃O₄is synthesized by a one-pot hydrothermal method,subsequently,CV is employed to electropolymerize polythionine on the Au/Co₃O₄.It is demonstrated that the HER electrocatalytic activity of Au/Co₃O₄is effectively improved by coating polythionine layer.The optimal polythionine/Au/Co₃O₄displays an excellent electrocatalytic ability towards HER with an overpotential of 168 m V at 10 m A cm^-2and low Tafel slope of 79 m V dec^-1in 0.5 mol dm^-3H₂SO₄,which is greatly superior to those of the Au/Co₃O₄(an overpotential of 300 m V at 10 m A cm^-2and Tafel slope of 157 m V dec^-1).Interestingly,the HER performance of N-doped reduced graphene（N-r GO）can be also significantly boosted by coating polythionine layers,indicating the multifunctionality of polythionine in the enhancement of HER performance of nano electrocatalysts.