Dual-functional nitrogen-doped carbon quantum dots: Highly selective and smartphone detection of lactic acid/L-arginine, mechanisms and applications.

The determination of lactic acid (LA) and L-arginine (L-Arg) is critical in biochemical analysis, disease diagnosis, and food supervision. Herein, nitrogen-doped carbon quantum dots (N-CQDs) for high selectively LA and L-Arg detection were prepared via a simple hydrothermal method using cheap isatoic anhydride and 1,2,4-triaminobenzene dihydrochloride as the materials. N-CQDs specifically responds to LA with detection limit of (LOD) as low as 3.13 μmol·L to cause fluorescence decrease, emission wavelength red-shift (444 to 504 nm), color change (blue to green). N-CQDs can also sensitively identify L-Arg with an LOD of 4.92 μmol·L to result in fluorescence enhancement. FT-IR, XPS analysis and density functional theory (DFT) suggest the possible mechanisms involve synergistic hydrogen bonding and electronic effects. N-CQDs exhibits good biocompatibility and photostability and may successfully apply to fluorescence imaging of medaka fish in vivo, information encryption, and quantitative detection of LA and L-Arg in real samples, indicating it may be a practical and smartphone tool for chemical analysis, bioimaging and food monitoring.