Small molecular probe as selective tritopic sensor of Al3+, F− and TNP: Fabrication of portable prototype for onsite detection of explosive TNP

- Small molecular probe as selective fluorescent chemosensor for Al3+, F− and TNP with LOD 1 μM, 3 μM and 500 nM respectively.
- Fluorescence enhancement for Al3+ and F− is due to PET-CT-CHEF-C=N isomerization & quenching with TNP occurs due to ACQ-RET-ICT.
- Al3+ and F− detection is reversible with NO3− & H+ which is used for logic circuit formation applicable in molecular electronics.
- One handy prototype has been designed and fabricated for on spot detection of TNP from solid or solution phase.

Schiff base organic compound (SOC) has been prepared as a tritopic chemosensor for selective sensing by fluorescence signalling towards ions like Al3+, F− and explosive molecule like TNP. In general, fluorescence like photophysical property has been used for selective detection of analyte where Al3+ and F− show turn-on fluorescence signal at different wavelengths (nm) however, quenching was found with TNP. As a consequence, the chemosensor has become a selective sensor for Al3+, F− and TNP. Reversibility of fluorescence responses for Al3+ and F− are observed in presence of ammonium nitrate and H+ respectively. Similar to the detection of TNP, the detection of explosive like NO3− salts is also essential from homeland security point of view. In the present work, the finding of reversible sequential fluorescence response can be promoted for fabrication of next generation AND-NOT-OR-NAND-XOR-XNOR-NOR based complex logic circuit which is applicable in photonics, security and other fields including inorganic and material science. In the case of TNP recognition, the pathway mainly depends on non-covalent interaction (quenching constant: 4.4 × 105 M−1) which is even better than the recently reported materials. Detection limit for Al3+, F− and TNP is 1 μM, 3 μM and 500 nM respectively. DFT-D3 has been carried out to explore the host⋯guest interaction along with the structure-property correlation of the present host-guest system. All three guest analytes have been detected inside the living cell at a certain level and in its consequence, the successful in vitro recognition ability of the SOCs inside human cell line HeLa has been explored too. In real time stepping, an easy to operate and an economically affordable pocket prototype has also been fabricated for on spot detection of TNP like explosive.

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