Photoelectrochemical and colorimetric dual-mode aptasensor for nonylphenol detection in food based on ascorbic acid-sensitive Bi2S3/Bi2O2CO3 heterojunction and multi-enzyme-mimicking Ce-MOF.

A simple and novel photoelectrochemical (PEC)-colorimetric (CL) dual-mode aptasensor was explored for nonylphenol determination using ascorbic acid (AA)-sensitive Bi2S3/Bi2O2CO3Z-Scheme heterojunction and Ce(III/IV)-MOF (R-UiO66-Ce) with dual enzyme-mimetic activity. Firstly, ascorbic acid phosphate was hydrolyzed under R-UiO66-Ce catalysis to generate AA to capture the hole of Bi2S3/Bi2O2CO3, which enhance the current response, and improved the detection sensitivity, achieving the PEC detection model. Then, 4-nitrophenyl phosphate disodium salt was hydrolyzed under R-UiO66-Ce catalysis to produce yellow 4-nitrophenyl and 3,3',5,5'-tetramethylbenzidine was oxidized by R-UiO66-Ce to produce blue product, achieving the dual-mode colorimetric detection. In the presence of nonylphenol, the hybridization event for aptamer DNA and probe DNA was inhibited, which blocked the following capture of R-UiO66-Ce, and decreased the PEC and colorimetric signal. The aptasensor was applied to detect nonylphenol in beer, milk, tea, shrimp with satisfactory results.