Unveiling of a smartphone-mediated ratiometric chemosensor towards the nanomolar level detection of lethal CN⁻: combined experimental and theoretical validation with the proposition of a molecular logic circuitry

Abstract

A promising naphthalene-functionalized ratiometric chemosensor (<i>E</i>)-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 Δ<i>G</i> 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 <i>Bacillus thuringiensis</i> and <i>Escherichia coli</i> is successfully investigated <i>via</i> 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 '<i>chemistry beyond the molecule</i>' and 'engineering' <i>via</i> 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.