An Off-On-Off Benzoxazole-Based Fluorosensor for Relay Detection of Al3+ Ions and Explosive Nitroaromatic Compounds

Abstract

Developing fluorosensors for the efficient detection of aluminium (Al3+) ions and electron-deficient nitroaromatic compounds (NACs) is in high demand but challenging. This report introduces a benzoxazole-based off-on-off fluorosensor for the cascade detection of Al3+ ions and electron-deficient NACs. Upon addition of Al3+ ions, the probe BPMP displays a bright blue fluorescence under the exposure of 365 nm UV light radiation in an H2O/DMSO (1 : 1 v/v) medium due to the chelation of Al3+ ions disrupting the ESIPT process involved in probe BPMP. The detection limit for Al3+ ions is found to be 13 nM, which is significantly lower than many chemosensors available in the literature. The 1 : 1 stoichiometry of the chelated complex between BPMP and Al3+ ions is confirmed by Job′s plot and also by 1H NMR titration investigation. More importantly, the Al3+ ions chelated BPMP complex is further used as a fluorescent turn-off probe for the detection of electron-deficient NACs with the detection as low as 10−7 M. Based on these chemically encoded inputs and the corresponding optical output, we have constructed one input and one output based YES, and NOT logic gate with BPMP and BPMP-Al3+ complex as input respectively and also dual inputs and single optical output-based INHIBIT logic gates. Also, BPMP-doped paper strips-based test kit analysis has been demonstrated as a displayable photonic device for on-spot detection. The performance of BPMP and Al3+ ions chelated BPMP complex toward Al3+ ions and electron-deficient NACs demonstrated that BPMP could be served as a sensitive probe and could be employed for real sample analysis.