Ultrafast excited states relaxation dynamics in solution investigated by stimulated emission from a styryl dye

Guo, Xunmin; Xia, Andong

doi:10.1016/j.jlumin.2006.01.183

Cited by 7 publications

(9 citation statements)

References 22 publications

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“…Femtosecond fluorescence depletion was conducted using a homemade femtosecond time-resolved stimulated emission depletion setup (TR-STED) as described in previous publications. − In brief, a femtosecond laser pulse at 420 nm was used as pump beams to excite the chromophores from the electronic ground state S 0 to a Franck−Condon level S 1 *. The second femtosecond probe at 840 nm at the magic angle (54.7°) with respect to the pump polarization pulse with a delay time was applied to the excited molecules to induce stimulated emission with a transition from the relaxing electronic state S 1 to the vibrationally excited ground level S 0 *.…”

Section: Methodsmentioning

confidence: 99%

Photophysical Properties of Intramolecular Charge Transfer in Two Newly Synthesized Tribranched Donor−π−Acceptor Chromophores

Jia

Yan

et al. 2010

J. Phys. Chem. A

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The nature of optical excitation and the degree of intramolecular charge transfer (ICT) as well as the dynamics of excited ICT states of two new tribranched donor-pi-acceptor molecules with acceptor-terminated (DA(3)) and acceptor-centered (AD(3)) geometries have been investigated by steady-state and femtosecond time-resolved stimulated emission fluorescence depletion (FS TR-SEP FD) measurements in different polar solvents. The interpretation of the experimental results is based on the comparative investigation of the two D-pi-A compounds with respect to the model monomer counterpart (DA). The larger solvatochromic effects and stronger solvent dependence of spectral properties of DA(3) than that of AD(3) indicate that the excited ICT state of DA(3) possesses higher polarity and larger dipole moments compared to those of AD(3). The similarity of absorption and strong solvent-dependent fluorescence spectra of DA(3) and DA reveals that the excited-state properties of DA(3) are identical to that of the model DA, which localized on one of the branches in DA(3). In contrast to DA(3), the large red shift in the absorption and the small Stokes shift of AD(3) suggest the formation of a delocalized ICT state to a certain extent in the excited state of AD(3). The dynamic behavior of excited ICT states for all three compounds are also investigated by femtosecond time-resolved stimulated emission depletion (FS TR-SEP FD) measurements, where the excited-state relaxations are highly dependent on both solvent polarity and the polar degree of the excited ICT states. Furthermore, the steady-state fluorescence excitation anisotropy shows that the intramolecular excitation transfer among the three disorder-induced localized ICT states with nondegenerate transition dipole moments is involved within DA(3). Compared to DA(3), a substantial red shift in the absorption of AD(3) results from the formation of a delocalized ICT state, where the specific excitation anisotropy spectrum shows that the excitation energy is mainly redistributed between the localized ICT state and the delocalized ICT state.

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Section: Methodsmentioning

confidence: 99%

Photophysical Properties of Intramolecular Charge Transfer in Two Newly Synthesized Tribranched Donor−π−Acceptor Chromophores

Jia

Yan

et al. 2010

J. Phys. Chem. A

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“…Femtosecond Fluorescence Depletion Measurements. Fluorescence depletion measurements for DA and DAD samples are measured on a homemade femtosecond time-resolved stimulated emission pumping fluorescence depletion (FS TR SEP FD) setup based on the principle of so-called “pump−probe' technology described elsewhere. − In brief, A CW laser with 532 nm (Verdi-V5, Coherent, USA) pumps a homemade Ti:sapphire laser producing the pulse at 800 nm with duration of about 65 fs at a repetition of 80 MHz. The output power is about 400 mW.…”

Section: Methodsmentioning

confidence: 99%

“…It is of interest to get deeper insight into the underlying photophysical mechanisms of the difference performances in the photovoltaic devices for DA and DAD. The femtosecond time-resolved fluorescence depletion measurements further provide the salvation-dependent information about the very early dynamics of the formation and solvation of the ICT state upon photoexcitation. − The fast solvation dynamics of these two novel compounds are investigated, suggesting that the solvent has a significant impact on the dynamics of ICT states.…”

Section: Introductionmentioning

confidence: 99%

Photophysical Properties of Photoactive Molecules with Conjugated Push−Pull Structures

Gong

Guo²,

Wang³

et al. 2007

J. Phys. Chem. A

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The photophysical properties of two newly synthesized photoactive compounds with asymmetrical D-π-A structure and symmetrical D-π-A-π-D structure are investigated in different aprotic solvents by steady-state and femtosecond fluorescence depletion measurements. It is found that the asymmetrical DA compound has larger dipole moment change than that of the symmetrical DAD compound upon excitation, where the dipole moments of the two compounds have been estimated using the Lippert-Mataga equation. Furthermore, the steady-state spectral results show that increasing solvent polarity results in small solvatochromic shift in the absorption maxima but a large red shift in the fluorescence maxima for them, indicating that the dipole moment changes mainly reflect the changes of dipole moment in excited-state rather than in ground state. The redshifted fluorescence band is attributed to an intramolecular charge transfer (ICT) state upon photoexcitation, which could result in a strong interaction with the surrounding solvents to cause the fast solvent reorganization. The resulting ICT states of symmetrical compounds are less polar than the asymmetrical compounds, indicating the different extents of stabilization of solute-solvent interaction in the excited state. Femtosecond fluorescence depletion measurements are further employed to investigate the fast solvation effects and dynamics of the ICT state of these two novel compounds. The femtosecond fluorescence depletion results show that the DA compound has faster solvation time than that of DAD compound, which corresponds to the formation of relaxed ICT state (i.e., a final ICT state with rearranged solvent molecules after solvation) in polar solvents. It is therefore reasonably understood that the ICT compounds with asymmetrical (D-π-A) structure have better performance for those photovoltaic devices, which strongly rely on the nature of the electron pushpull ability, compared to those symmetrical compounds (D-π-A-π-D).

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“…The second type of observed kinetic process revealed 3–6 ps characteristic times and, presumably, corresponds to a solvate relaxation phenomenon. ,− After these fast relaxations, the values of photoinduced optical density Δ D relax back to zero in accordance with the much longer fluorescence lifetimes of the S 1 state. (See Table .)…”

Section: Resultsmentioning

confidence: 90%

Photophysical Properties and Ultrafast Excited-State Dynamics of a New Two-Photon Absorbing Thiopyranyl Probe

et al. 2013

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Comprehensive linear photophysical and photochemical characterization, two-photon absorption (2PA) properties, and femtosecond excited-state dynamics of a symmetrical fluorene derivative 2-(2,6-bis((E)-2-(7-(diphenylamino)-9,9-dihexyl-9H-fluoren-7-yl)vinyl)-4H-thiopyran-4-ylidene)malononitrile (1) are reported. The linear one-photon absorption (1PA), steady-state fluorescence, excitation, and excitation anisotropy spectra of 1 were investigated in organic solvents of different polarities at room temperature, exhibiting rather complex absorption and emission behavior. The relatively strong 2PA of thiopyranyl 1 was investigated by the open aperture femtosecond Z-scan technique in the main long wavelength 1PA contour with maxima cross sections up to 600−700 GM. Femtosecond dynamics of the excited-state absorption (ESA) and gain processes in 1 exhibited fast complicated relaxation phenomena with a strong dependence on solvent polarity and a weak dependence on excitation wavelength. The nature of the observed transient absorption kinetics was explained based on the short-lived ESA bands of 1 and solvate relaxation phenomena. Quantum chemical calculations, based on density functional theory, were employed for additional analysis of the 1PA and 2PA properties of 1.

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Ultrafast excited states relaxation dynamics in solution investigated by stimulated emission from a styryl dye

Cited by 7 publications

References 22 publications

Photophysical Properties of Intramolecular Charge Transfer in Two Newly Synthesized Tribranched Donor−π−Acceptor Chromophores

Photophysical Properties of Intramolecular Charge Transfer in Two Newly Synthesized Tribranched Donor−π−Acceptor Chromophores

Photophysical Properties of Photoactive Molecules with Conjugated Push−Pull Structures

Photophysical Properties and Ultrafast Excited-State Dynamics of a New Two-Photon Absorbing Thiopyranyl Probe

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