The Fabrication And Application Of Near-infrared Responsive Photoelectrochemical Sensors For The Detection Of Biotoxins In Aquatic Products

The near-infrared photoelectrochemical(NIR PEC)analysis is a technique that based on the changes in photocurrent/photovoltage caused by the interaction of photoelectrically active materials with the target under the irradiation of NIR light.It not only has the advantages of low background signal,high sensitivity,and easy miniaturization of the instrument in the PEC method,but also can combine the characteristics of good NIR light biocompatibility and strong penetrating ability,thus has a good application prospects in the field of rapid detection of hazards in food.This thesis takes the biological toxins in aquatic products as the main research object,by using the NIR PEC materials including silver sulfide(Ag₂S)cubes(NCs)and quantum dots(QDs)combined with the local surface plasmon resonance(LSPR)effect of gold nanoparticles(AuNPs),as well as the flower-like tungsten oxide(FL-WO₃)combined with up-conversion materials(UCNPs),NIR PEC sensors were constructed based on direct immunity and competitive immunosensing mode to achieve high sensitivity and rapid detection of microcystin(MC-LR),okadaic acid(OA)and tetrodotoxin(TTX).The main research contents of this thesis include three parts:(1)A novel NIR PEC immunosensing platform was fabricated for detecting MC-LR in fish based on AuNPs sensitized Ag₂S NCs.MC-LR is one of the main pollutants of freshwater fish.This study found that the LSPR effect and good conductivity of AuNPs can significantly improve the photoelectrical conversion efficiency of Ag₂S NCs,and the steric hindrance effect produced by the combination of MC-LR and the antibody immobilized on the electrode surface leads to a decrease in photocurrent.Based on this,a NIR PEC immunosensor was constructed for sensitive and rapid detection of MC-LR in Hypophthalmichthys molitrix.Under optimal conditions,the PEC intensity of the sensor decreased proportionally to the logarithmic of the MC-LR concentrations in the range of 10 pg L^-1 to 10?g L^-1,and the detection limit was 7 pg L^-1(S/N=3).(2)A NIR PEC competitive immunosensing platform was fabricated for measuring OA in shellfish based on UCNPs-driven FL-WO₃/screen-printed electrodes(SPE).OA is the main component of diarrheal shellfish poisoning.This study found that UCNPs can convert NIR excitation into visible light emission,and their emission wavelength matches the absorption wavelength of FL-WO₃,so UCNPs can drive FL-WO₃ to generate photocurrent.Accordingly,using UCNPs as the beacon of OA antibodies,combined with the modified FL-WO₃ on the SPE,a NIR PEC sensing method based on the competitive immunosorbent assay(c NIR-PECIA)was established for the efficient detection of shellfish.Under optimal conditions,the PEC intensity of the sensor and OA concentration showed a good linear relationship in the range of 0.01 to 60?g L^-1,and the detection limit was 7 ng L^-1(S/N=3).(3)A paper-based NIR PEC sandwich immunosensing platform was fabricated for detecting TTX in puffer fish based on Ag₂S QDs.Firstly,AuNPs were electrodeposited on paper-based SPE to obtain PSPEG,and then Ag₂S QDs prepared by one-pot method were modified on the surface of PSPEG.The electrode presented good NIR PEC performance.Accordingly,SPEG was used as a capture probe to immobilize the primary antibody(Ab₁)of TTX,and Ag₂S QDs was used as a beacon to label the secondary antibody(Ab₂),thereby a new type of paper-based NIR PEC sandwich immunosensor was constructed to realize convenient and rapid detection of TTX.Under optimal conditions,the PEC intensity of the sensor and the logarithm of the TTX concentration showed a good linear relationship in the range of 0.001 to 100?g L^-1,and the detection limit was 5 ng L^-1(S/N=3).