Triphenylamine-Based Colorimetric and Fluorometric Sensor for Cu²⁺, Co²⁺ Ions and Volatile Acid Vapour: Experimental and DFT Studies.

In this work, we describe the development of an imidazole functionalised colorimetric receptor (TDC) that can distinguish Cu2+ and Co2+ ions in aqueous acetonitrile medium with colour changes that are visible to the naked eye. With the addition of small amount of Cu2+ the colour changes from colourless to Persian green and for Co2+ it changes to light violet. Additionally, TDC exhibits exceptional sensitivity to Cu2+ and Co2+ cations in aqueous acetonitrile by fluorometric change, acting as a "turn-off" luminous chemosensor. Lower detection limits of 21.5 nM and 24.2 nM were used to validate fluorometric selectivity towards Cu2+ and Co2+ ions. It was evident that with passing the vapours of TFA the colour of the chemosensor TDC changes from colourless to mild green with the emergence of new peak at 638 nm. In order to examine the interaction site, determine the energies of the border molecular orbitals, and validate some of the experimental findings, a computational DFT research was conducted on the free ligand TDC and complex with Cu2+ and Co2+. The sensing ability of TDC was also supported by the silica based portable, easily disposable device studies.