Paper-supported near-infrared-light-triggered photoelectrochemical platform for monitoring Escherichia coli O157:H7 based on silver nanoparticles-sensitized-upconversion nanophosphors.

Escherichia coli O157:H7 (E. coli O157:H7) is a typical foodborne pathogen that contaminates food and water, leading to lots of infectious diseases. In this study, a near-infrared-responsive photoelectrochemical (PEC) sensing platform for the ultrasensitive detection of E. coli O157:H7 was established by assembling a flexible conductive paper electrode with core-shell-structured upconversion nanophosphors (UCNPs) @SiO 2 @Ag and carbon self-doped graphitic carbon nitride (C-g-C 3 N 4). In this design, UCNPs act as a self-powered that change near infrared (NIR) excitation into visible emission, while the semiconductor material C-g-C 3 N 4 acts as the energy-conversion center to convert visible illumination to photocurrent. Importantly, silver nanoparticles (AgNPs) significantly enhance the upconversion luminescence of UCNPs and facilitate the separation and transportation of photoelectrons by the localized surface plasmon resonance effect. Using the antimicrobial peptide Magainin I as the recognition element, E. coli O157:H7 was specifically captured and determined directly for its steric hindrance effect on the photoelectrode. As a result, the photocurrent decreased linearly with the increase in E. coli O157:H7 in a wide range from 5 to 5 × 106 colony-forming units per mL (CFU/mL), and the detection limit was as low as 2 CFU/mL. Finally, the proposed NIR PEC sensor was successfully utilized for the determination of E. coli O157:H7 in contaminated pork, cabbage, and milk samples without enrichment of the bacteria in 50 min. ◆ A paper-supported NIR (980 nm) - responsive PEC sensing platform was developed ◆ AgNPs dramatically improved the UCL of UCNPs and the PEC performance of C-g-C 3 N 4 ◆ E. coli O157:H7 was concentrated and determined using the proposed NIR PEC platform ◆ A relatively low LOD of 2 CFU/mL was achieved for E. coli O157:H7 detection ◆ Due to the high sensitivity, there is no need to enrich bacteria before detection ◆ The proposed method could be used for rapid detection of E. coli O157:H7 in food [ABSTRACT FROM AUTHOR]