Analysis of Fluorescence Quenching of Coumarin Derivative under Steady State and Transient State Methods

Nature has gifted us many organic molecules which have remarkable influence in our daily life. Amongst many organic molecules, heterocyclic organic molecules have gained potential applications in the advanced field of biomedicine, pharmaceutical, electronics and many more. In the present work fluorescence quenching of biologically active fluorescent probe 8EMOHCC by aniline in different solvents have been studied at room temperature. To understand the molecular behaviour in different media, solvents of different refractive index and dielectric constant have been used. Spectroscopic measurement techniques such as UV/Vis spectroscopy and time related single photon counting are employed to characterise the molecule at room temperature. The fluorescence quenching study shows linear dependence of SV-plot in solvents of different dielectric constants. It reveals that quenching reactions are dynamic in nature. Various parameters of quenching have been determined and identified the type of quenching involved in the quenching reaction. Further, kq is found to be greater than $$ {k}_q^{\prime } $$ in ACN, methanol, propanol and dioxane. Activation energy of quenching (Ea) is found to be greater than energy of diffusion (Ed) in ACN, methanol, propanol, THF solvents and Ed > Ea in dioxane, indicating that quenching reaction is not solely controlled by material diffusion but also activation process.