Proton induced green emission from AIEE active 2,2′ biquinoline hydrosol and its selective fluorescence turn-on sensing property towards Zn2+ ion in water

[Display omitted] •Hydrosol of 2,2′ Biquinoline microstructures exhibits aggregation induced enhanced emission.•Proton triggered yellowish green emission is observed under UV excitation.•2:1 complex of 2,2′ Biquinoline with Zn2+ shows sky blue emission under UV excitation.•2,2′ Biquinoline hydrosol is used as potential turn on senor for Zn2+ and H+ ion in water. A novel material showing aggregation induced enhanced emission (AIEE) is developed by reprecipitation method using 2,2′ biquinoline (BQN) in aqueous medium. Morphologies of the particles are characterized using optical and scanning electron microscopic (SEM) study. The selective fluorescence and absorbance response of aggregated BQN towards Zn2+ and H+ have been explained due to ground state complexation and protonation of BQN with Zn2+ and H+ respectively. Protonated BQN exhibits charge transfer character in transoid form with yellowish green emission but in BQN-Zn2+ complex, BQN changes to cis planer conformation and displays considerable intra ligand charge transfer (ILCT) character with sky blue color under UV excitation. A 2:1 BQN-Zn2+ complex have been confirmed using Job’s plot. Our study revealed that BQN hydrosol act as selective turn-on fluorescence sensor for Zn2+ ion both in acidic and alkaline medium. Further, the proton induced charge transfer character and the proposed binding modes of the receptor with Zn2+ have been supported by DFT based computational study.