Nanosecond Time-Resolved Emission Spectroscopy: Spectral Shifts due to Solvent-Excited Solute Relaxation

Abstract

Nanosecond time-resolved emission spectral techniques have been applied to the problem of the origin and nature of the well-known temperature-dependent spectral shifts characteristic of the aminophthalimides in alcohol solvents. It is demonstrated that the temperature-dependent spectral shifts are in fact due to time-dependent spectral shifts. At least two relaxation times characterize this phenomenon. One relaxation time is observed to be subnanosecond in character and may be associated with the exciplex that presumably is present in the system. The other relaxation time is presumably associated with the nonspecific dipolar reorientation although it has distinctly different characteristics from the solvent dielectric relaxation time. Wavelength-dependent fluorescence decay that can be explained by the time dependence of the emission spectrum is also observed.

Hydrophobic Clustering in Acid-Denatured IL-2 and Fluorescence of a Trp NH···π H-bond

“…The fluorophore and environment must relax in order to accommodate the new charge distribution of the excited state. This can be directly observed during the lifetime of the excited state by representing multiwavelength time-resolved fluorescence as TRES (45). This phenomenon has been characterized in proteindye interactions (31,46) and tryptophan in proteins and membranes (47)(48)(49).…”

Time-resolved fluorescence emission spectra of labeled phospholipid vesicles, as observed using multi-frequency phase-modulation fluorometry

“…The phase and modulation values for any assumed decay law can be calculated from the sine and cosine transforms of the decay law [21,22]. Let fo ~l(X,t)sin ¢otdt (3) fo~l(X, t)cos ¢otdt D~(X) fo~l(X,t)d t (4) Then, substitution of Eqn. I yields:…”

“…Hence, the timedependent spectra parameters reveal the timecourse of these rather complex intermolecular interactions. For instance, time-resolved decays of fluorescence intensity have been utilized in detailed studies of the dynamic interactions of fluorophore and solvents [4][5][6] and biological macromolecules [7,8]. Also, such measurements have been used to distinguish between stepwise and continuous relaxation processes [5,9] and to detect the subnanosecond formation of partially relaxed fluorophores [4].…”

Nanosecond timescale optical inhomogeneous broadening of dye molecules in liquids at and near room temperature

“…However, for the fluorescence depolarization measurements the detection optics were modified. Since solvent relaxation about an excited chromophore occurs on the time scale of the fluorescence lifetime in these samples [ 23,241, the population decay from the S, excited state is complicated and non-exponential if detection is made over a narrow spectral region of the fluorescence. Therefore, a double, subtractive-dispersive monochromator was modified to pass a broad band of fluorescence ( z 60 nm) and block only a narrow band ( x 1 nm) around the laser excitation wavelength to avoid detecting scattered laser light.…”