Surface plasmon resonance-enhanced photoelectrochemical immunoassay with Cu-doped porous BiWO nanosheets.

The development of rapid screening sensing platforms to improve pre-screening mechanisms in community healthcare is necessary to meet the significant need for portable testing in biomarker diagnostics. Here, we designed a portable smartphone-based photoelectrochemical (PEC) immunoassay for carcinoembryonic antigen (CEA) detection using Cu-doped ultrathin porous BiWO (CuBWO) nanosheets as the photoactive material. The CuBWO nanosheets exhibit a fast photocurrent response and excellent electrical transmission rate under UV light due to their surface plasmon resonance effect (SPR). The method uses glucose oxidase-labeled secondary antibody as a signal indicator for sandwich-type immune conjugation. In the presence of the target CEA, the electrons and holes generated at the surface of the photo-excited ultrathin porous CuBWO were rapidly consumed by the production of HO from glucose oxidase oxidizing glucose, resulting in a weakened photocurrent signal. The photocurrent intensity increased logarithmically and linearly with increasing CEA concentration (0.02-50 ng mL), with a detection limit of 15.0 pg mL (S/N = 3). The system provides a broader idea for inferring the electron-hole transport mechanism in ultrathin porous nanosheet layer materials and developing efficient PEC sensors.