Solvent Polarity Dependent Ultrafast Relaxation Kinetics of ADS800AT Dye.

This work investigated the photoexcitation and relaxation kinetics of the ADS800AT dye dissolved in different solvents using transient absorption spectroscopy (TAS) with a white-light continuum probe. The dye was dissolved in various solvents, including dichloromethane (DCM), 1,2-dichlorobenzene (DCB), ethanol, and methanol, to study their impact on the dye's characteristics. The linear absorption peak varied from 835 to 809 nm, depending on the polarity of the solvent, and the pump wavelength for TAS was chosen accordingly. We observed ground-state bleaching and excited-state absorption after exciting the dye with the pump pulse. Global analysis was performed using Glotaran software to fit exponential decay curve models, allowing us to determine the relaxation time of the excited molecule. The relaxation time varied from 198 ps to 508 ps across the different solvents, decreasing as the polarity of the solvent increased. Additionally, we could experimentally correlate the dye molecule's nonlinear properties with the solvent's polarity.