Early Time Solvation Dynamics Probed by Spectrally Resolved Degenerate Pump‐Probe Spectroscopy

Abstract

The dynamic role of solvent in influencing the rates of physico‐chemical processes (for example, polar solvation and electron transfer) has been extensively studied using time‐resolved fluorescence spectroscopy. Here we study ultrafast excited state relaxation dynamics of three different fluorescent probes (DNTTCI, IR‐140 and IR‐144) in two polar solvents, ethanol and ethylene glycol, using spectrally resolved degenerate pump‐probe spectroscopy. We discuss how time‐resolved emission spectra can be directly used for constructing relaxation correlation function, obviating spectral reconstruction and estimation of time‐zero spectrum in non‐polar solvents. We show that depending on the specific probe used, the relaxation dynamics is governed either by intramolecular vibrational relaxation (for IR140) or by intermolecular solvation (for DNTTCI) or by both (for IR144). We further show (using DNTTCI as a probe) that major differences in solvation by ethanol and ethylene glycol is contributed by early time (<1 ps) dynamics.

Unravelling the Role of Water in Ultrafast Excited‐State Relaxation Dynamics within Nano‐Architectures of Chlorophyll a

“…Details of the customized femtosecond transient absorption spectrometer (TAS, Newport) are discussed elsewhere. [26,27] The ultrashort pulse centered at 670 nm having~43 fs pulse-width at 1 kHz repetition rate from a commercial non-collinear optical parametric amplifier (Topas White, Light conversion), pumped by a Ti: Sapphire regenerative amplifier centered on~800 nm having~54 fs pulse-width (Libra, Coherent), is used as pump to excite the Q y band of Chl-a. At the pump laser wavelength (centered at 670 nm), the optical densities of monomer, rodshaped and micellar structures are 0.192, 0.148 and 0.125, respectively.…”

Stable CsPbI3-Mesoporous Alumina Composite Thin Film at Ambient Condition: Preparation, Characterization, and Study of Ultrafast Charge-Transfer Dynamics

“…Thus, by noting the sign (positive or negative) of differential absorption (ΔOD > 0 or ΔOD < 0) and recording the time evolution of different spectral regions of the probe, we can map these signals. The detailed information of the pump–probe setup is given elsewhere , (see the Supporting Information). We used ultrafast TA spectroscopy to appraise the role of charge conducting materials (TiO 2 and P3HT) to separate the charges generated in CsPbI 3 .…”

“…In the absence of any charge-conducting layer, the exciton relaxes by the charge recombination via radiative or nonradiative pathways . Since there is a time-dependent red shift in the spectrum centered at 645 nm, we introduced a time correlation function to measure the time-dependent relaxation in the excited state, much like the same way it is constructed to estimate excited-state relaxation via dipolar solvation . Details of the time correlation function calculation can be found in the Supporting Information.…”

“…Thus, by noting the sign (positive or negative) of differential absorption (ΔOD > 0 or ΔOD < 0) and recording the time evolution of different spectral regions of the probe, we can map these signals. The detailed information of the pump−probe setup is given elsewhere 52,53 (see the Supporting Information).…”

Ultrafast Excited-State Dynamics of Tricarbocyanine Dyes Probed by Two-Dimensional Electronic Spectroscopy: Polar Solvation vs Photoisomerization

“…The effect of solvent refractive index on steady-state spectra of cyanine dyes was investigated followed by solvent-dependent studies on steady-state fluorescence and fluorescence lifetime of tricarbocyanin dyes . Of special interest is the study of solvation dynamics − probed using tricarbocyanine dyes as the probe. However, the low quantum yield of fluorescence (or, equivalently, short fluorescence lifetime) of these molecules limits their application to be used as suitable probes in the solvation dynamics experiments based on time-gated detection of fluorescence. − As an alternative to fluorescence-based techniques, third-order nonlinear optical spectroscopic methods, for example, transient absorption (pump–probe) spectroscopy, − transient grating spectroscopy, , and photon-echo spectroscopy,− were implemented which are particularly useful for weakly fluorescent probes like tricarbocyanine dyes.…”