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

ABSTRACT

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 (λ_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 ¹H 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).

GRAPHICAL ABSTRACT

KEYWORDS:

• Spirooxazine
• turn-on fluorescence probe
• copper(ii) ion
• test strip

Acknowledgments

W.S. would like to thank the Kasetsart University Research and Development Institute (KURDI) and the Center of Excellent for Innovation in Chemistry (PERCH-CIC), Ministry of Higher Education, Science, Research and Innovation. W.F. also thanks the Human Resource Development in Science Project (Science Achievement Scholarship of Thailand, SAST) for the support.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Supplementary material

Supplemental data for this article can be accessed online at https://doi.org/10.1080/10610278.2023.2221365

Additional information

Funding

This research was supported by the Kasetsart University Research and Development Institute (KURDI) under Grant FF(KU)9.65 and the Cluster and Program Management Office (CPMO), the NSTDA-EGAT joint funding scheme, under Grant P1450309.