A novel label-free photoelectrochemical immunosensor based on NCQDs and BiS co-sensitized hierarchical mesoporous SnO microflowers for detection of NT-proBNP.

A unique hierarchical mesoporous SnO microflower was utilized for the fabrication of an immunosensor. The modified nitrogen-doped carbon quantum dots (NCQDs) improved the photoelectrochemical (PEC) activity of the SnO, and contributed to the in situ assembly of BiS nanoparticles on the surface of the SnO materials. Under the stimulation of visible light and ascorbic acid as an efficient electron donor, the NCQDs and BiS co-sensitized mesoporous SnO microflower (SnO/NCQDs/BiS) modified ITO electrode exhibited an excellent photoelectric signal arriving at around 150 μA. Moreover, a novel label-free PEC sensor based SnO/NCQDs/BiS composite was constructed, which enabled the ultrasensitive detection of N-terminal pro-B-type natriuretic peptide (NT-proBNP). The photocurrents decreased linearly with the logarithm of NT-proBNP concentration in the range of 0.01-50 ng mL with a detection limit of 3.7 pg mL (S/N = 3). Furthermore, the novel PEC immunosensor showed perfect selectivity, good stability and reproducibility, which suggest promising applications in the sensing and clinical diagnosis of cardiac disease.