Biomass carbon quantum dots and Zr-MOFs as ratiometric fluorescent probes for sensitive detection of biogenic amines...

On-site rapid food safety testing is an important means of market supervision. A "dual-response-reverse" (one signal increases while the other decreases) type biomass carbon quantum dots (G-BCQDs)/Zr-MOF ratiometric fluorescent paper-based sensor was designed for the visual detection of spermine concentration (SPM, a representative of biological amines). G-BCQDs (emitting at 477 nm) and Zr-MOF (emitting at 537 nm) exhibit reverse fluorescence responses to spermine, namely quenching and enhancement, respectively, thus enabling fluorescence ratio detection. The smartphone was connected with the ratiometric fluorescent paper-based sensor to quantitatively detect the concentration of spermine. The results showed that there was a linear relationship between the concentration of spermine in the range of 0.1-220.0 µM and the R' value of RGB values, and the linear equation was R' = 0.3740C_SPM + 141.75 (R² = 0.9913). The detection limit of the method was 19.93 µM. Shrimp samples were selected to evaluate the practicability of the ratiometric fluorescent paper-based sensor for detecting spermine concentration. The results of the spiked recovery experiment showed that the recovery rate of the shrimp samples was in the range of 90.97-101.14%, and the relative standard deviation was less than 2.15%, indicating that the ratiometric fluorescent paper-based sensor had high accuracy and precision and was shown to be applicable for detecting SPM in spoiled samples and thus for monitoring spoilage.