Sensitive colorimetric and ratio l-arginine probe for smartphone detection and living roe imaging

Owing to the importance of L-Arginine (Arg) in humans and organisms, it is necessary to develop efficient methods to detect it. In this article, a novel colorimetric and ratio Arg probe L1 was developed via a simple synthetic process from economical substrates. The D-π-A structure having a large conjugated system endowed it with the high performance of large Stokes shift and obvious color changes both in its UV and fluorescence. The dual-signal sensor was constructed with excellent colorimetric sensitivity with the detection limit (LOD, S/N = 3) of 57.91  nM, which can realize the detection of Arg for qualitative analysis without any instrument. Besides, the probe also has relatively great selectivity and fluorescence sensitivity with the detection limit of 131.5 nM. Meanwhile, the short response time within 2 min allowed it to detect Arg immediately. The binding mechanism was also investigated by various ways, job’s plots indicated a 2:1 stoichiometric ratio of L1 with Arg, and the synergistic effects of deprotonation and intermolecular hydrogen bonding are considered as the primary interactions through ¹H NMR titration experiments and theoretical calculation. The frontier orbitals distribution and their respective energies of L1 and 2L1 + Arg complex were obtained too, the reduced energy gap corresponded with the red shift of the absorption peak. Based on these excellent recognition behavior, probe L1 was not only used as the convenient Arg detection sensor in various food by a smartphone, but also applied in the living fertilized medaka egg imaging.