Poly-L-lysine functionalized graphene quantum dots embedded zirconium metal–organic framework-based fluorescence switch on-off-on nanoprobe for highly sensitive and selective detection of taurine

Taurine is now widely used as a novel diagnostic biomarker for cardiovascular disease. Unfortunately, engaged techniques for the analysis of taurine are suffering from low sensitivity, poor selectivity, and a tedious process. In this work, the poly-L-lysine functionalized graphene quantum dots embedded UiO-66@NH2 metal–organic framework (PLL-fGQDs@UiO-66@NH2 MOF) based turn ‘On-Off-On’ fluorescent nanoprobe was designed for taurine sensing. Initially, synthesized PLL-fGQDs, UiO-66@NH2 MOF, and PLL-fGQDs@UiO-66@NH2 MOF nanoprobe were confirmed using UV–Vis spectroscopy, FT-IR analysis, particle size analysis, fluorescence study, PXRD, SEM-EDAX, HR-TEM, etc. Here, anticipated PLL-fGQDs incorporation into UiO-66@NH2 MOF nanoprobe portrayed a highly fluorescent nanoprobe for taurine sensing. The copper (Cu2+) ions addition in the fluorescent nanoprobe resulted in fluorescence dampness followed by taurine addition showed the recovery of quenched fluorescence. Principally, it might be because of the greater binding affinity of Cu2+ ions towards taurine-containing oxygen atoms of a sulfonic group and the nitrogen atom of an amine group. The linear concentration range, limit of detection (LOD), and limit of quantification (LOQ) of taurine were found to be 5 ng/mL to 360 ng/mL, 2.91 ng/mL, and 8.84 ng/mL, respectively. It also provides a high selectivity towards taurine in the occurrence of interfering agents whereas practical applicability was assured by spiked artificial serum samples analysis. In conclusion, the designed PLL-fGQDs@UiO-66@NH2 MOF nanoprobe offers high sensitivity, selectivity, good stability, repeatability, and practicability. In the future, it can be used as a new nanoprobe for taurine recognition with improved performance than the traditional methods.