Confinement of defect-rich bimetallic InO/CeO nanocrystals in mesoporous nitrogen-doped carbon as a sensitive platform for photoelectrochemical aptasensing of Escherichia coli.

The sensitive determination of food-borne pathogens from food products is essential to ensure food safety and to protect people's health. Herein, a novel photoelectrochemical (PEC) aptasensor was manufactured based on defect-rich bimetallic cerium/indium oxide nanocrystals confined in mesoporous nitrogen-doped carbon (denoted as InO/CeO@mNC) for sensitively detecting Escherichia coli (E. coli) from real samples. A new cerium-based polymer-metal-organic framework [polyMOF(Ce)] was synthesized using polyether polymer containing 1,4-benzenedicarboxylic acid unit (L8) as ligand, trimesic acid as co-ligand, and cerium ions as coordination centers. After adsorbing trace indium ions (In), the gained polyMOF(Ce)/In complex was calcined at high temperature under nitrogen atmosphere, resulting in the production of a series of defect-rich InO/CeO@mNC hybrids. Benefitting from the advantages of high specific surface area, large pore size, and multiple functionality of polyMOF(Ce), InO/CeO@mNC hybrids showed enhanced visible light absorption ability, separation performance of the photo-generated electrons and holes, promoted electron transfer, as well as the strong bioaffinity toward E. coli-targeted aptamer. Accordingly, the constructed PEC aptasensor illustrated an ultralow detection limit of 1.12 CFU mL, remarkably lower than most of the reported E. coli biosensors, along with high stability and selectivity, excellent reproducibility, and expected regeneration ability. The present work provides insight into the construction of a general PEC biosensing strategy based on MOF-based derivatives for the sensitive analysis of food-borne pathogens.