Fabrication Of Photoelectrochemical Sensors And Their Applications For Hg²⁺ And Tumor Marker Detection

Due to its great potential in future analysis,photoelectrochemical（PEC）sensor with the features of low cost,fast detection speed,and easy miniaturization,has attracted substantial attentions in the analytical chemistry community.This technique possesses a totally separated light exciter and electrical signal detector,which makes it has a relatively lower background and higher sensitivity.To fabricate a highly sensitive PEC sensor,main attention should be paid to the exploration of highly efficient photoactive materials and specific recognition elements.In this regard,the main contents focus on the synthesis of PEC materials and their sensing applications.The main contents are described as below:A PEC probe with Ru^II bipyridyl complex as chromophore,thiocyanate ligand as recognition unit,and carboxylate group as the linkage site,was designed and coupled with TiO₂nanoparticles for the highly sensitive and selective detection of Hg²⁺in aqueous systems.Under irradiation,the PEC probe possesses strong visible light harvesting ability,highly efficient photoelectron transfer efficiency to the TiO₂ nanoparticles modified electrode,and good adhesive and photophysical stability.However,the specific coordination of Hg²⁺with the probe via the thiol moiety in thiocyanate significantly decreased the photocurrent response,which was attributed to the shift of adsorption spectrum and the change of inner energy level.Under optimal conditions,the PEC probe showed linear relationship with Hg²⁺concentrations in the ranges from 10^-12 to 10^-7 and 10^-7 to 10^-4 g/mL and a detection limit of 1 pg/mL.In addition,the PEC probe could exclude the interference from the possible existing metal ions,which make it has great potential for Hg²⁺monitoring in real systems.A PEC immunosensing strategy based on the synergistic interaction of TiO₂/CdS:Mn and polydopamine nanoparticles（PDA NPs）was designed for the highly sensitive detection of CEA,a typical tumor marker related with many malignant diseases.The PDA NPs synthesized via a simple self-polymerization reaction possessed a uniform size distribution,good dispersibility in water solution,good biocompatibility,and plenty of functional groups for biomolecule assembly.They also owned unique photophysical properties,whose light absorption covered a wide range from visible to infrared lights,totally covering the absorption and emission light ranges of the TiO₂/CdS:Mn nanocomposites.Thus,when the immune-recognition brought the PDA NPs close to the TiO₂/CdS:Mn interface,the PDA NPs competed with TiO₂/CdS:Mn to absorb the irradiation light,induced energy transfer between the two kinds of nanomaterials,and at the same time hindered the access of electron donor to photoactive materials,thus leading to a significant photocurrent decrease.Benefiting from the synergistic interaction,the PEC immunosensor showed high sensitivity towards CEA detection.Under optimal conditions,a low detection limit of 0.0178 pg/mL and wide linear relationship from 0.1 pg/mL to 100 ng/mL were obtained.The p-BiOI/n-β-Bi₂O₃/AuNR/TiO₂ nanodumbbells（NDs）multilayer was fabricated with high PEC transfer efficiency and tailorable light absorption range.The bottom p-BiOI/n-β-Bi₂O₃ hetero-junction layer was prepared by an electrodeposition method followed with a calcination process.Then,it was assembled with the AuNR/TiO₂ nanocomposites,which had a nanodumbbell structure and showed a tailorable light absorption range from visible light to infrared region.Upon light irradiation,the cascade energy band distribution efficiently promoted the photoelectron transfer and improved the PEC conversion efficiency,which may have potential applications in the PEC bioassay.