Solvatochromic, thermochromic and pH-sensory DCDHF-hydrazone molecular switch: Response to alkaline analytes

Multi-stimuli responsive DCDHF-hydrazone molecular switch containing a hydrazone recognition moiety is developed for the naked-eye detection of alkaline analytes in both vapour and aqueous media. Mechanisms accounting for the thermochromism, pH-sensitivity and solvatochromism are proposed. DCDHF-hydrazone chromophores of different substituents introduced nanostructures with different morphologies via a re-precipitation technique. The films formulated from these nanostructures function as solid-state vapochromic sensors for probing alkaline vapours such as amines and ammonia. The sensing performance is reversible and has differential sensitivity towards a variety of amines at comparable concentrations. The structure of the hydrazone molecular switch was established spectroscopically and by single crystal X-ray crystallography.