Core-sheath-type TiO2@NH2-MIL-125(Ti) nanocone arrays for sensitive photoelectrochemical detection of carcinoembryonic antigen

In this study, a highly sensitive photoelectrochemical (PEC) immunosensor for the detection of carcinoembryonic antigen (CEA) utilizing core-sheath-type TiO 2 @NH 2 -MIL-125(Ti) nanocone array heterostructures was developed. The immunosensor was constructed by depositing NH 2 -MIL-125(Ti) as a sheath onto FTO/TiO 2 nanocones through seed-assisted solvothermal synthesis. The TiO 2 @NH 2 -MIL-125(Ti) heterostructure showcased superior PEC detection capabilities for CEA, leveraging the quantum and tip effects of the TiO 2 nanocones along with the broad-spectrum absorption of NH 2 -MIL-125(Ti), which collectively enhanced light utilization and photoelectric conversion efficiency. The internal electric field at the NH 2 -MIL-125(Ti)/TiO 2 interface enabled efficient photogenerated electron transfer, eliminating the need for external bias and enhancing photocurrent. The antibody-functionalized surface effectively captured CEA, resulting in a clear decrease in photocurrent. Under optimized conditions, the immunosensor exhibited a linear response to CEA in the range of 0.1 pg/mL to 100 ng/mL with a remarkable detection limit of 0.54 fg/mL. The developed PEC immunosensor demonstrated high stability and excellent reproducibility, providing an innovative strategy for the development of sensitive photoactive heterojunction materials for biomarker immunosensing applications.