A near-infrared photoelectrochemical immunosensor for CA72-4 sensing based on SnS nanorods integrated with gold nanoparticles.

SnS nanorods with near-infrared photoelectric conversion characteristics were successfully synthesized through a simple hydrothermal method. Gold nanoparticles were self-assembled onto SnS nanorods surface to form SnS/AuNPs nanocomposites. The integration of AuNP can significantly improve the photocurrent response of SnS nanorods under being illuminated with 808 nm near-infrared light. A near-infrared photoelectrochemical immunosensing platform based on SNS/AuNPs nanocomposites was constructed for sensing gastric cancer tumor marker CA72-4. Experimental conditions were optimized to improve the immunosensing performances for CA72-4 determination. As CA72-4 concentration varied from 0.01 to 50 U mL, the photocurrent variation between the immunosensor before and after reacting with CA72-4 was linearly related to the logarithm of its concentration. The detection limit was calculated to be 0.008 U mL. The practicability of the immunosensor was demonstrated by determining CA72-4 in human serum samples.