A promising naphthalene-functionalized ratiometric chemosensor (E)-1-((naphthalen-5-yl) methylene)-2-(2,4-dinitrophenyl) hydrazine (DNMH) is unveiled in the present work. DNMH demonstrates brisk discernible colorimetric response from yellow to red in the presence of CN-, a lethal environmental contaminant, in a near-perfect aqueous medium with a LOD of 278 nM. The "key role marker" controlling the electrochemical and non-covalent H-bonding interaction between DNMH and CN- is through the commendable role of acidic -NH functionalities. Kinetic studies reveal a pseudo second order reaction rate and the formation of an unprecedented photostable adduct. The negative value of ΔG as evaluated from ITC substantiates the spontaneity of the DNMH⋯CN- interaction. The sensing mechanism was further reinforced with state-of-the-art theoretical investigations, namely DFT, TDDFT and Fukui indices (FIs). Moreover, the proposition of a reversible multi-component logic circuitry implementing Boolean functions in molecular electronics has also been triggered by the turn-over spectrophotometric response of the ditopic ions CN- and Cd2+. The cytotoxicity of DNMH towards Bacillus thuringiensis and Escherichia coli is successfully investigated via the MTT assay. Impressively, "dip stick" and "easy to prepare" test paper device and silica gel-based solid-phase CN- recognition validate the on-site analytical application of DNMH. Furthermore, the involvement of a synergistic approach between 'chemistry beyond the molecule' and 'engineering' via an exquisitely implemented smartphone-assisted colorimetric sensory prototype makes this work unprecedented among its congeners and introduces a new frontier in multitudinous material-based functional product development.
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