We have developed a novel isonicotiamide-based fluorescent “turn-on” chemosensor 1 for the selective detection of Zn²⁺ and HSO₄⁻. The sensor 1 can detect Zn²⁺ and HSO₄⁻ with a detection limit down to the nanomolar level by forming a complex in 1 : 1 stoichiometry in the presence of other anions and 2 : 1 in presence of cations in aqueous solution. Density functional theory calculations on 1 and the 1-Zn²⁺/HSO₄⁻ complexes are consistent with the experimental results. We have successfully utilized the above cation and anion for the fabrication of INHIBIT molecular logic gates. Furthermore the receptor 1 successfully detected the Zn²⁺ and HSO₄⁻ ions in HeLa cells cultured in Zn²⁺ and HSO₄⁻ enriched medium.