A competitive photoelectrochemical assay for estradiol based on in situ generated CdS-enhanced TiO2.

A novel and simple photoelectrochemical (PEC) bioassay protocol for estradiol was proposed based on in situ generated CdS-enhanced TiO 2 film via competitive strategy. The CdS was generated in situ by immediately dropping S 2− onto the Cd 2+ -functionalized titanium phosphate nanoparticles (TiP@Cd 2+ ). The TiO 2 photoactive sensing film with countless active sites was obtained by calcination and further explored for estradiol (E 2 ) capture. The TiP@Cd 2+ was used as labels and immobilized through affinity-specific binding with E 2 on the surface of the electrode. Greatly enhanced sensitivity was achieved by using porous TiP nanoparticles as carriers to load a large amount of Cd 2+ and further for more CdS production through the S 2− deposition. What's more, the photocurrent of CdS generated on the electrode surface could be significantly amplified by the coupling of CdS and TiO 2 , which could enhance the excitation and photo-to-electric conversion efficiency. Through the application of a competitive binding assay, the proposed biosensor showed high sensitivity with a detection limit down to 2 pg/mL. This simple and fast PEC E 2 -sensing approach offers great promise to extend its application for the assay of small molecules of biomedical, food and environmental interest. Additionally, the strategy of employing in situ generated narrow-band gap semiconductors paves a new way for PEC sensing. [ABSTRACT FROM AUTHOR]