A Portable Smartphone Platform with FeNPs@g-C3N4 Nano-enzyme for Visual and On-site Sensing of F- and Al3+ in Tea

Abstract

The development of on-site, portable and visual assays for trace elements detection in tea is essential to ensure the health of the population in consideration of its widespread availability and most familiar consumption. Herein, a composite nano-enzyme (FeNPs@g-C3N4) based smartphone platform was proposed for sensing F- and Al3+. The FeNPs@g-C3N4 nano-enzyme with excellent peroxidase activity was synthesized through Fe nanoparticles (FeNPs) in situ growth on graphite-phase carbon nitride nanosheets (g-C3N4), which could catalyze H2O2 to oxidize TMB to blue oxide (oxTMB). The peroxidase activity of FeNPs@g-C3N4 nano-enzyme could be inhibited by F-, and then restored by Al3+ because of the coordination reaction between Fe3+/Al3+ and F-. Furthermore, based on the fact that the solution color could be dynamic manipulated by the concentrations of F- and Al3+,a smartphone was employed in visual detection by capturing and identifying the Red-Green-Blue (RGB) value of the solution images with detection limits of 2.43 nM and 7.66 μM. The cooperation of smartphone camera and color recognition application has greatly shortened the detection time and reduced the cost of detection, which provided a new strategy for the on-site and convenient detection of F- and Al3+ in tea, and showed significant application potential in food safety evaluation.