Fluorescence-quenching studies and temperature dependence of fluorescence quantum yield, decay time and intersystem crossing activation energy of TPB

Fluorescence quenching of 1, 1, 4, 4-tetraphenyl-1, 3-butadiene (TPB) by aniline has been carried out at room temperature (298 K) to understand the role of quenching mechanisms. The study has been carried out by both steady state (in different solvents) and by transient method (in cyclohexane). The Stern-Volmer plot has been found to be linear for all the solvents studied. The probability of quenching per encounter ‘p’ is determined in all the solvents and is found to be less than unity. It is found that, the activation energy E_a (E′_a) is greater than the activation energy of diffusion, E_d. The results obtained by the transient method infer that the thermally assisted intersystem crossing, a non-radiative deactivation process from S₁ to T₂ is responsible for observed decrease in quantum yield and lifetime. Hence, from both the methods it can be concluded that quenching mechanism is not solely due to the material diffusion, but there is also contribution from the activation energy.