A novel photoelectrochemical immunosensor based on TiO2@Bi2WO6 hollow microspheres and Ag2S for sensitive detection of SARS-COV-2 nucleocapsid protein

Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-COV-2) is a cluster of β coronaviruses. The 2019 coronavirus disease (COVID-19) caused by SARS-COV-2 is emerging as a global pandemic. Thus, early diagnosis of SARS-COV-2 is essential to prevent severe outbreaks of the disease. In this experiment, a novel label-free photoelectrochemical (PEC) immunosensor was obtained based on silver sulfide (Ag 2 S) sensitized titanium dioxide@bismuth tungstate (TiO 2 @Bi 2 WO 6 ) nanocomposite for quantitative detection of SARS-COV-2 nucleocapsid protein. The constructed TiO 2 @Bi 2 WO 6 hollow microspheres had large specific surface area and could produce high photocurrent intensity under visible light illumination. Ag 2 S was in-situ grown on the surface of thioglycolic acid (TGA) modified TiO 2 @Bi 2 WO 6 . In particular, TiO 2 @Bi 2 WO 6 and Ag 2 S formed a good energy level match, which could effectively enhance the photocurrent conversion efficiency and strength the photocurrent response. Ascorbic acid (AA) acted as an effective electron donor to effectively eliminate photogenerated holes. Under optimal experimental conditions, the constructed immunosensor presented a supersensitive response to SARS-COV-2 nucleocapsid protein, with a desirable linear relationship ranged from 0.001 to 50 ng/mL for nucleocapsid protein and a lower detection limit of 0.38 pg/mL. The fabricated sensor exhibited a wide linear range, excellent selectivity, specificity and stability, which provided a valuable referential idea for the detection of SARS-COV-2.