Exploring the molecular binding mechanism of 6-fluoro, 4-hydroxy, 2- methyl quinoline with TiO2 nanoparticles: A spectroscopic, thermodynamic, and insights into the solvatochromic effect.

ABSTRACT

This study investigates the interaction between titanium oxide nanoparticles (TiO2 NPs) and the heterocyclic fluorophore 6-fluoro,4-hydroxy,2-methylquinoline (6-FHMQ), aiming to understand fluorescence quenching mechanisms and thermodynamic characteristics. Spectroscopic techniques including spectrofluorometry (FL) and spectrophotometry (UV-Vis) were used, with a lifetime decay (τ) of 0.18 ns for 6-FHMQ measured using time correlated single photon counting (TCSPC). The interaction between 6-FHMQ and TiO2 NPs revealed a mix of static and dynamic fluorescence quenching mechanisms, with increasing quenching constants (Ksv) and a higher bimolecular quenching rate constant (Kq). The dynamic nature was highlighted by a temperature-dependent increase in binding sites from 1 to ~ 2. Spontaneous complexation was affirmed by negative change in free energy (ΔG), with negative change in enthalpy (ΔH) and a positive change in entropy (ΔS) values indicating favorable electrostatic and ionic interactions. The impact of varying TiO2 NP concentrations on 6-FHMQ absorption was analyzed using the Benesi-Hildbrand equation, with a quantum yield of 0.61 determined. By forster resonance energy transfer (FRET) theory, the proximity between 6-FHMQ and TiO2 NPs was found to be less than 70 Å. Ground and excited state dipole moments of 6-FHMQ in different solvents were calculated to demonstrate solvent sensing ability and charge transfer properties. Ultimately, this study serves as a testament to the power of scientific innovation in the realms of drug delivery and tissue engineering.