| Photoelectrochemical(PEC)sensing is a new analytical technology which has been developed rapidly in recent years.Due to their advantages of fast response,low background noise,low cost and easy miniaturization,PEC sensors have been widely used in environmental monitoring,biochemical analysis and clinical diagnosis.In a PEC sensor,the semiconductive electrode material plays a vital role because its photoelectric conversion efficiency directly affects the sensitivity of detection.Although most semiconductors have good absorption and high photoelectric conversion efficiency under UV light irradiation,the energy of UV light is high,which can easily damage the biological recognition element or analyte.In contrast,visible or near-infrared(NIR)light possessing lower energy is relatively ideal as the excitation source for PEC biosensing.Nevertheless,the photoelectric properties of many semiconducting materials are not high under visible or NIR light irradiation.In this dissertation,semiconducting materials with enhanced visible or NIR photoactivity were prepared,which were explored to develop PEC sensors for achieving highly sensitive detection of different analytes.The main research contents and results are as follows:(?)A nanocomposite of Cd S nanoparticles and europium metal organic framework(Eu-MOF)(Cd S/Eu-MOF)was synthesized and used as photoelectric active materials to construct a PEC aptasensor for the detection of ampicillin(AMP).Due to the fact that Eu-MOF could help to improve the PEC properties of Cd S by utilizing a broader spectrum for light harvesting and facilitating the electron transfer,the nanocomposite exhibited an enhanced photocurrent response.In order to realize the specific detection of AMP,the AMP-binding aptamer was immobilized on the Cd S/Eu-MOF modified electrode surface as the recognition element during the construction of the sensor.When AMP was present,the photocurrent of sensor increased,attributed to the fact that AMP was captured by aptamer and then oxidized by photocatalysis under visible light irradiation.Several experimental conditions including the ratio of Cd S to MOF,the coating amount of the Cd S/Eu-MOF suspension and the concentration of the aptamer were studied.Under optimum conditions,the photocurrent of the developed sensor was linearly related to the logarithm AMP concentration in the range of 1.0×10-10 to 2.0×10-7 mol·L-1,with a detection limit(3?)of 9.3×10-11 mol·L-1.Moreover,the developed sensor was applied to the determination of AMP in lake water and milk samples,showing satisfactory potential practical applicability.(?)Yb-doped Bi2S3(Yb-Bi2S3)semiconducting material was prepared via a simple solvothermal method to improve its NIR photoelectric properties.It was employed as photoelectric active material to fabricate a NIR light-driven PEC aptasensor for the detection of adenosine triphosphate(ATP).Under NIR light irradiation,the Yb-Bi2S3modified electrode exhibited admirable photocurrent response,ascribed to the unfilled 4f orbital of Yb which introduced the impurity level between the valence band and conduction band of Bi2S3.When ATP was specifically captured by the aptamer immobilized on the electrode surface,the ATP-aptamer complex was formed,which increased the steric hindrance on the electrode surface,leading to declined photocurrent.Based on such a response,the quantitative determination of ATP was realized.The sensor showed a linear responsed to the logarithm of ATP comcentration from 0.5 to 300nmol·L-1,with a detection limit(3?)of 0.1 nmol·L-1.Moreover,this PEC sensor exhibited high selectivity,good repeatability and desirable stability.(?)Upconversion nanoparticles(UCNPs),namely Na YF4:Yb,Er,was doped into Bi2S3 nanorods to enhance the NIR photoelectric property of material.The UCNPs/Bi2S3modified photoanode was combined with a Pt cathode to construct a two-electrode photocatalytic fuel cell(PFC)system driven by NIR light.On the baisis of the constructed PFC,a self-powered sensing platform for the detection of aflatoxin B1(AFB1)was developed.Under NIR light irridation,UCNPs could absorb low-energy photons and radiate out specific types of photons with shorter wavelength through the anti-Stokes optical process to excite Bi2S3,resulting in the generation of more electron-hole pairs on the photoanode to catalyze the oxidation of H2O in electrolyte.Meanwhile,the dissolved oxygen in electrolyte was catalytically reduced on Pt cathode.Thus,a high electrical output power was generated from the two electrode reactions of PFC,which could provide the signal for self-powered sensing.Furthermore,the AFB1-binding aptamer was immpobilzied on the photoanode to serve as the recognition element.Based on the competition between the interaction of aptamer with AFB1 analyte and hybridization of aptamer with Au nanoparticles-labeled DNA sequence,a self-powered strategy for AFB1detection was proposed.Under optimum conditions,the output of PFC was linearly proportional to the logarithm of AFB1 concentration from 0.01 ng·m L-1 to 100 ng·m L-1,with a detection limit(3?)of 0.0079 ng·m L-1.Moreover,the contents of AFB1 in flour samples were determined by the constructed sensing platform.The results were consistent with those obtained by commercial enzyme linked immunosorbent assay kit,indicating the good practical performance of the developed self-powered sensor. |
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