Designing Schottky junction constructed from porous PdPt nanospheres embedded in Bi2S3 nanorods for ultrasensitive photoelectrochemical immunoassay of acute myocardial infarction biomarkers

•The Schottky barrier formed in the B&P composite effectively prevents electron backflow.•The light absorption efficiency of B&P composite is improved due to the LSPR effect.•Suppressed recombination rate of h+and e-due to internal electric field.•The mechanism of the photoelectrochemical sensor is thoroughly investigated.•The PEC platform exhibited desired sensitivity and stability for cTnI detection. Acute myocardial infarction (AMI) is a prevalent and life-threatening cardiovascular disease that often presents suddenly, posing a significant threat to human life and health. Cardiac troponin I (cTnI), as a key biomarker, is crucial for sensitive and quantitative detection in clinical diagnostics. However, given the extraordinarily low concentrations of cTnI in the actual samples, achieving a highly sensitive and cost-effective determination is quite challenging. In this work, a photoelectrochemical (PEC) immunosensing platform for ultra-high sensitivity analysis of cTnI was successfully developed. The ultra-high sensitivity of the method is attributed to three favorable factors. Initially, Bi2S3 nanorods are used as the substrate and porous PdPt nanospheres are loaded on its surface, where the energy levels of the two materials match each other to form a Schottky barrier, which restrained the compounding of the photogenerated electron-hole pairs, facilitating the rapid separation and migration of electrons. Secondly, the bandgap of B&P composites becomes narrower after the materials are combined, which is conducive to the improvement of the absorption ability of visible light and carrier migration efficiency. Thirdly, the localized surface plasmon resonance (LSPR) effect, generated by the incorporation of porous PdPt nanospheres, significantly boosts light utilization efficiency. The constructed PEC sensor exhibited a linear range from 100 fg/mL to 100 ng/mL and a detection limit of 31.6 fg/mL under the optimal conditions, possessing ideal detection performance. In addition, the prepared immunosensors also displayed excellent sensitivity, selectivity, reproducibility, and stability. The work was also extended to the analysis of real samples, which yielded satisfactory results and provided new prospects for the construction of an accurate and portable sensing platform for early disease diagnosis.