A Novel Label-free Photoelectrochemical Sensor Based on N,S-GQDs and CdS Co-sensitized Hierarchical ZnSnO Cube for Detection of Cardiac Troponin I

A novel label-free photoelectrochemical (PEC) sensor based on graphene quantum dots doped with nitrogen and sulfur (N,S-GQDs) and CdS co-sensitized hierarchical ZnSnO cube was fabricated to detect cardiac troponin I (cTnI). The unique hierarchical ZnSnO cube was synthesized successfully by the solvothermal method, which has a large specific surface to load functional materials. N,S-GQDs nanoparticles were assembled to the surface of cubic ZnSnO coated ITO electrode, which efficiently accelerated the electronic transition and improved photo-to-current conversion efficiency. Then, CdS nanoparticles further were modified by in-situ growth method to form ZnSnO/N,S-GQDs/CdS composite with prominent photocurrent, which was 30 times that of the ZnSnO cube alone. In this work, the specific immune recognition between cTnI antigens and cTnI antibodies (anti-cTnI) reduced the intensity of the photoelectric signal. And the intensity decreased linearly with the logarithm of cTnI concentration range from 0.001 ng/mL to 50 ng/mL with a detection limit of 0.3 pg/mL. With high sensitivity, excellent selectivity, good stability and reproducibility, the fabricated PEC sensor showed promising applications in the sensor, clinical diagnosis of myocardial infarction and PEC analysis.