A reversible and symmetric naphthalene-based ESIPT-active fluorescent chemosensor for Al3+ ions: real sample applications, molecular logic gates, bioimaging and latent fingerprint visualization

Abstract

A symmetric naphthalene derivative fluorescent chemosensor, XYHN, was conveniently prepared via a simple one-step reaction and demonstrated fast, sensitive, and selective recognition of trivalent aluminum ions (Al³⁺). Fluorescence titration and Job's plot analysis showed 1 : 1 stoichiometric binding between XYHN and Al³⁺ in a CH₃OH : H₂O (1 : 1, v/v) buffer medium at physiological pH (pH 7.0). Through coordination with Al³⁺ ions, the sensor demonstrated a clear “turn-on” fluorescence response due to the disruption of C–N bond rotation and the excited-state intramolecular proton transfer (ESIPT) process, thus stabilizing the emissive state. The limit of detection (LOD) and limit of quantification (LOQ) of Al³⁺ were found to be 8.88 nM and 2.9 nM, respectively, confirming the probe's high sensitivity. Additionally, the biological applicability of the probe XYHN was validated by its successful application for the detection of Al³⁺ in actual environmental water and food samples. The system was also used to assemble molecular logic gates through fluorescence outputs, proving its potential in molecular computations. Besides, the powdered XYHN probe was successfully used in forensic science to visualize latent fingerprints on various porous and non-porous surfaces upon irradiation with UV light. Such multiple functionalities make the probe XYHN a potential chemosensor for analytical, environmental, and forensic applications.