A competitive photoelectrochemical immunosensor for the detection of diethylstilbestrol based on an Au/UiO-66(NH2)/CdS matrix and a direct Z-scheme Melem/CdTe heterojunction as labels

A novel photoelectrochemical (PEC) bioassay protocol for diethylstilbestrol (DES) was systematically proposed. The Au/UiO-66(NH2) hybrid with countless active sites was fabricated using an in situ reduction strategy and was subsequently decorated with CdS nanoparticles (NPs) by a sequential chemical bath deposition process. The resulting Au/UiO-66(NH2)/CdS composites were exploited as a sensing matrix for the first time. The excellent photocurrent response of the as-prepared hybrid under visible light is attributed to its improved photo-electric conversion efficiency due to the local surface plasma resonance (LSPR) effect of Au and the matching energy-level structure between UiO-66(NH2) and CdS. In addition, the competitive strategy for the detection of DES was devised by employing the direct Z-scheme Melem/CdTe heterojunction covalently conjugated with bovine serum albumin (BSA)-DES as signal tags. As a consequence, a cascade-like band-edge level was obtained, which could effectively promote the transfer of photogenerated charges and markedly improve the photocurrent. On the basis of the above strategy, the concentrations of DES could be detected through the competitive binding of DES antibodies (Anti-DES) with either Melem/CdTe/BSA-DES or free DES. Under optimal conditions, the linear range for the detection of DES was 0.1 pg mL-1 to 20 ng mL-1. The detection limit was as low as 0.06 pg mL-1 (S/N = 3). Furthermore, the designed PEC DES-sensing approach has acceptable selectivity, reproducibility, and stability and offers great promise for the detection of small molecules in biomedical, food and environmental samples.