A novel label-free photoelectrochemical immunosensor based on CdSe quantum dots sensitized Ho3+/Yb3+-TiO2 for the detection of Vibrio parahaemolyticus

A novel photoelectrochemical (PEC) immunosensor based on CdSe quantum dots (QDs) sensitized Ho 3+ /Yb 3+ -TiO 2 for the detection of Vibrio parahaemolyticus (VP) was assembled. The working electrode was constructed via the layer-by-layer (LBL) method with the Ho 3+ /Yb 3+ -TiO 2 , CdSe QDs, NHS/EDC, antibody of VP (anti-VP), bovine serum albumin (BSA) modified on the surface of the FTO in sequence. Ascorbic acid (AA) acts as an electron donor to combine photogenerated holes in order to provide a stable current system. Ho 3+ and Yb 3+ co-doping TiO 2 broadened the spectral response range of TiO 2 to the infrared region and improved the photocurrent responsiveness of TiO 2 . The PEC immunosensor, with Ho 3+ /Yb 3+ ratio of 1:5, Ho 3+ /Yb 3+ -TiO 2 of 2 mg/mL and PBS solution of pH 7.4, had an optimal photocurrent responsiveness. Immobilization of anti-VP was by classical NHS/EDC coupling reactions between COOH groups of CdSe QDs and NH 2 groups of the anti-VP. The results indicated that PEC immunosensors had a low detection limit of 25 CFU/mL, a wide detection range of 10 2 –10 8  CFU/mL, high stability, low price, and short detection time. This method could be promising for the rapid and ultrasensitive detection of pathogenic microorganisms in the food.