Smartphone-based ratiometric fluorescence sensor for sensitive visual detection of H2O2 and glucose based on B-CDs-Ag NPRs-OPD ternary system

A straightforward and highly sensitive ratiometric fluorescence sensor comprising blue emissive carbon dots , silver nanoprisms, and o-phenylenediamine (B-CDs-Ag NPRs-OPD) was developed for the detection of H 2 O 2 and glucose. Ag NPRs were etched into Ag +  ions upon exposure to H 2 O 2 , which caused non-fluorescent OPD to be oxidized and produce 2,3-diaminophenazine (DAP), resulting in intense yellow fluorescence emission at 555 nm. DAP can quench the B-CDs based on inner filter effect (IFE), leading to a decrease in their fluorescence intensity at 435 nm. Because glucose oxidase may catalyze the oxidation of glucose to produce H 2 O 2 , this approach can also be used to detect glucose. The unique triangular structure leads to the easy etching of the edge and tip of Ag NPRs by H 2 O 2 into Ag +  ions, allowing for the high sensitivity of detection of H 2 O 2 and glucose with limit of detection (LOD) of 0.12 μM and 0.6 μM, respectively. Furthermore, with the increase of the concentrations of H 2 O 2 and glucose, a visible color shift from blue to yellow-green occurs, which can be detected using a smartphone's color recognition application that captures the RGB channel values of the image. Real-time and on-spot detection of H 2 O 2 and glucose were achieved based on smartphone sensing platform, presenting vast potential for applications in various fields.