Four salicylidene-based dual-responsive chemosensors 1,5-bis(5-bromosalicylaldehyde)carbohydrazone (R1), 1,5-bis(5-bromosalicylaldehyde)thiocarbohydrazone (R2), 1,5-bis(3-ethoxysalicylaldehyde)carbohydrazone (R3) and 1,5-bis(3-ethoxysalicylaldehyde)thiocarbohydrazone (R4) were synthesized and characterized. The molecular structures of R1 and R3 were confirmed by single crystal X-ray diffraction technique, which crystallized in the orthorhombic Pbcn and monoclinic P21/n space groups, respectively. The chemosensor molecules were investigated for their recognition properties against the selected cations (K+, Ca2+, Mn2+, Co2+, Ni2+, Cu2+, Zn2+, Fe3+ and Al3+) and anions (F-, Cl-, Br-, I-, HSO4-, H2PO4-, ClO4-, N3- and NO3-) by colorimetry, absorption spectroscopy, fluorescence spectroscopy, 1H NMR spectroscopy and theoretical studies. The sensor molecules showed colorimetric responses for the Co2+, Ni2+, Cu2+ and Fe3+ cations and the F- anion. Interestingly, the Zn2+ and Al3+ cations showed only the 'turn on' fluorometric response, whereas the F- anion showed both colorimetric and fluorometric responses. The binding constants were determined using the Benesi-Hildebrand (B-H) equation from the fluorescence titrations and found to be higher for R3 towards the Al3+ cation (2.03 × 106 M-1) with a low limit of detection (1.79 μM) and for R4 towards the F- anion (5.13 × 105 M-1) with a low limit of detection (5.23 μM). The chemosensors established 1 : 2 and 1 : 1 binding stoichiometries with the sensed cations and anion, respectively, as confirmed by Job's plots. The computational studies show a lower band gap of HOMO-LUMO when the chemosensors bind with the sensed inorganic ions compared to the free chemosensors. Furthermore, the observed fluorescent behaviour of the Zn2+ and Al3+ cations have motivated us to investigate the practical applications in the live cell-imaging of zebrafish larvae as well as in the development of a molecular logic gate.