Synthesis, structural analysis and sensing performance of a novel spirooxazine derivative as a turn-on fluorescence probe for Cu2+ detection with high selectivity and sensitivity

A novel spirooxazine, MeOBnSPO, as a fluorescence probe was successfully synthesised and its molecular structure was confirmed by single crystal X-ray crystallographic and spectroscopic analyses. The sensing performance of MeOBnSPO for Cu2+ was achieved with a 'turn-on' fluorescent detection in acetonitrile. The results demonstrated that MeOBnSPO possessed high selectivity towards Cu2+ with a 10-fold enhancement in fluorescence intensity (lambda(em) = 544 nm) and high sensitivity at the micromolar concentration. The limit of detection was calculated to be 19.1 nM. Evidence for the ring opening reaction and 1:1 stoichiometric complexation of MeOBnSPO to Cu2+ was proven by H-1 NMR titration, FT-IR, MS, and Job analyses. Moreover, a drastic change in colour from colourless to bright yellow could provide naked-eye detection for Cu2+ with rapid response. The viable test strips of MeOBnSPO were also developed for Cu2+ colorimetric detection in mixed acetonitrile - H2O (50:50 v/v).