A novel label-free photoelectrochemical immunosensor based on NCQDs and Bi2S3 co-sensitized hierarchical mesoporous SnO2 microflowers for detection of NT-proBNP

Abstract

A unique hierarchical mesoporous SnO₂ microflower was utilized for the fabrication of an immunosensor. The modified nitrogen-doped carbon quantum dots (NCQDs) improved the photoelectrochemical (PEC) activity of the SnO₂, and contributed to the in situ assembly of Bi₂S₃ nanoparticles on the surface of the SnO₂ materials. Under the stimulation of visible light and ascorbic acid as an efficient electron donor, the NCQDs and Bi₂S₃ co-sensitized mesoporous SnO₂ microflower (SnO₂/NCQDs/Bi₂S₃) modified ITO electrode exhibited an excellent photoelectric signal arriving at around 150 μA. Moreover, a novel label-free PEC sensor based SnO₂/NCQDs/Bi₂S₃ 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⁻¹ with a detection limit of 3.7 pg mL⁻¹ (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.