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Keitaro Yoshihara - One of the best experts on this subject based on the ideXlab platform.

  • Ultrafast excited state dynamics of polybenzonitrile investigated by using femtosecond time-resolved Fluorescence Up-Conversion
    Journal of Luminescence, 2002
    Co-Authors: Tieqiao Zhang, Keitaro Yoshihara, Shufeng Wang, Hong Yang, Wentao Huang, Qihuang Gong, Qian Wang, Jiagang Luo, Huiying Chen
    Abstract:

    Abstract The photoluminescence dynamics of a new polymer, (–CN–) conjugated polybenzonitrile, was investigated with a femtosecond time-resolved Fluorescence Up-Conversion technique. The experimental results revealed a bi-exponential relaxation dynamics for excited state and it was explained with the photo-generated excitons’ migration model.

  • Energy transfer in a porphyrin chelate assembly
    Chemical Physics Letters, 1999
    Co-Authors: Igor V. Rubtsov, Yoshiaki Kobuke, Hidekazu Miyaji, Keitaro Yoshihara
    Abstract:

    Abstract Energy transfer among isoenergetic pigments, three oxinyl-substituted free-base porphyrins in an octahedral chelate Ga(III) complex, has been studied by the femtosecond Fluorescence Up-Conversion technique. The anisotropy decay of the complex has a fast component of ∼10 ps which is assigned to the energy transfer between the nearest porphyrin units in the complex. The anisotropy decay of the monomer (oxinyl-substituted porphyrin) is much slower and reflects monomer rotational dynamics in solution with decay times of 50 and ∼200 ps in dichloromethane.

  • ULTRAFAST PHOTOINDUCED SOLUTE-SOLVENT ELECTRON TRANSFER : CONFIGURATION DEPENDENCE
    Journal of Physical Chemistry A, 1999
    Co-Authors: Igor V. Rubtsov, Hideaki Shirota, Keitaro Yoshihara
    Abstract:

    Ultrafast photoinduced electron transfer between excited oxazine-1 (OX1) dye and electron donating solvents aniline (AN) and N,N-dimethylaniline (DMA) has been studied with the femtosecond Fluorescence Up-Conversion technique. Ultrafast and highly nonexponential Fluorescence decay of OX1 is observed in AN and DMA. The fastest component observed is about 60 fs in DMA and assigned to Fluorescence quenching due to an electron transfer reaction. Fluorescence decays are observed to be strongly dependent on the wavelength of observation in DMA and moderately dependent in AN. The wavelength dependence is assigned to Fluorescence from different configurations of OX1 and solvent molecules. The energy parameters for electron transfer are estimated and discussed.

  • Ultrafast Photoinduced Solute−Solvent Electron Transfer: Configuration Dependence
    The Journal of Physical Chemistry A, 1999
    Co-Authors: Igor V. Rubtsov, Hideaki Shirota, Keitaro Yoshihara
    Abstract:

    Ultrafast photoinduced electron transfer between excited oxazine-1 (OX1) dye and electron donating solvents aniline (AN) and N,N-dimethylaniline (DMA) has been studied with the femtosecond Fluorescence Up-Conversion technique. Ultrafast and highly nonexponential Fluorescence decay of OX1 is observed in AN and DMA. The fastest component observed is about 60 fs in DMA and assigned to Fluorescence quenching due to an electron transfer reaction. Fluorescence decays are observed to be strongly dependent on the wavelength of observation in DMA and moderately dependent in AN. The wavelength dependence is assigned to Fluorescence from different configurations of OX1 and solvent molecules. The energy parameters for electron transfer are estimated and discussed.

  • Deuterium Isotope Effect on the Solvation Dynamics of Methanol: CH3OH, CH3OD, CD3OH, and CD3OD
    The Journal of Physical Chemistry, 1996
    Co-Authors: Hideaki Shirota, Haridas Pal, † Keisuke Tominaga, Keitaro Yoshihara
    Abstract:

    Deuterium isotope effects on the solvation dynamics of methanol have been investigated using the femtosecond Fluorescence Up-Conversion technique. Deuterated methanols (CH3OD, CD3OH, and CD3OD) show slower solvation dynamics than normal methanol. The isotope effect arising from the OH group is about 10% and that arising from the CH3 group is about 5%, which are explained by the effects of hydrogen bonding and the frictional constant, respectively.

Qihuang Gong - One of the best experts on this subject based on the ideXlab platform.

  • Ultrafast excited-state dynamics associated with the photoisomerization of a cyanine dye.
    The Journal of chemical physics, 2012
    Co-Authors: Zhenwei Wang, Shufeng Wang, Saisai Chu, Qihuang Gong
    Abstract:

    The ultrafast excited-state dynamics of a cyanine dye, 3,3′-bis(3-sulfopropyl)-5,5′-dimethoxy-thiacyanine triethylaminium salt, was investigated by using conventional time-resolved Fluorescence Up-Conversion technique. The Fluorescence decay can be well described as tri-exponential kinetics, which indicates the excited-state population decays through the bond-twist, vibrational and radiative relaxation channels. Further analysis shows that the contributions of the three relaxation channels to the Fluorescence decay demonstrate very different change with increasing the Fluorescence wavelength, through which the detailed dynamics at different regions in the excited-state potential energy surface can be retrieved.

  • Steady-state and transient-state optical properties of a charge-transfer composite material MO-PPV/SWNTs
    Chemical Physics Letters, 2007
    Co-Authors: Saisai Chu, Shufeng Wang, Wenke Feng, Qihuang Gong
    Abstract:

    Abstract Charge-transfer composite material, poly-1-methoxy-4-octoxy-(para-phenelene vinylene) (MO-PPV) wrapped single wall carbon nanotubes (SWNTs), MO-PPV/SWNTs, was synthesized by in situ polymerization. Photophysics properties of MO-PPV/SWNTs were studied by using steady-state spectra, femtosecond Fluorescence Up-Conversion technique, and streak camera. Compared with the pure MO-PPV in solution, Fluorescence quenching was observed. Photoinduced electron-transfer from MO-PPV to SWNTs occurs on femtosecond timescale, while photoinduced intermolecular energy-transfer appears at ∼100 ps timescale.

  • Broadband parametric amplification in ultrafast Fluorescence application
    Chinese Optics Letters, 2005
    Co-Authors: Shufeng Wang, Qihuang Gong
    Abstract:

    Broadband parametric amplification is applied for the femtosecond ultrafast Fluorescence research. The time resolution depends on duration of pump pulse, which works both as pump source and gate. For spectrum application, a special phase-matching angle exists for broadband amplification correspondence to the pump wavelength. The broadband amplification range from 500 to 750 nm was found for 'beta'-barium borate (BBO) crystal, pumped at 400 nm. Large dye Fluorescence amplification of 10^(7) is realized. The generation of cone emission is selected as reference for system tuning. It is supposed to be a new method for ultrafast study in Fluorescence comparable to Fluorescence Up-Conversion and optical Kerr gate techniques.

  • Ultrafast excited state dynamics of polybenzonitrile investigated by using femtosecond time-resolved Fluorescence Up-Conversion
    Journal of Luminescence, 2002
    Co-Authors: Tieqiao Zhang, Keitaro Yoshihara, Shufeng Wang, Hong Yang, Wentao Huang, Qihuang Gong, Qian Wang, Jiagang Luo, Huiying Chen
    Abstract:

    Abstract The photoluminescence dynamics of a new polymer, (–CN–) conjugated polybenzonitrile, was investigated with a femtosecond time-resolved Fluorescence Up-Conversion technique. The experimental results revealed a bi-exponential relaxation dynamics for excited state and it was explained with the photo-generated excitons’ migration model.

  • Photophysical Studies on the Mono- and Dichromophoric Hemicyanine Dyes III. Ultrafast Fluorescence Up-Conversion in Methanol: Twisting Intramolecular Charge Transfer and "Two-State Three-Mode" Model
    The Journal of Physical Chemistry B, 2002
    Co-Authors: Yanyi Huang, Shufeng Wang, Tianrong Cheng, Chunhui Huang, And Wentao Huang, Qihuang Gong
    Abstract:

    A series of hemicyanine dyes, including monomer ([(E)-N-methyl-4-(2-(4-N,N-dimethyl phenyl) ethenyl) pyridinium] iodide; M) and dimers (1,n-Bis [(E)- 4-(2-(4-N,N-dimethyl phenyl) ethenyl) pyridinyl]-alkane dibromide; n = 3, alkane = propane, B3; n = 5, alkane = pentane, B5; n = 12, alkane = dodecane, B12), are synthesized and their ultrafast Fluorescence Up-Conversion behaviors are studied. The Fluorescence decay curves of these dyes can be well fitted by the sum of several exponential decays in the shorter wavelengths and by the sum of the exponential rise(s) with decay(s) in the longer wavelengths. The fact that the values of longest lifetime component at longer wavelengths tend to be a constant proves the existence of a “sink” region on the potential energy surface of excited state. This sink region is around the TICT state, by which the nonradiative transition dominates the deactive decay paths of excited state. The time dependent Stokes shift function analysis of these four dye molecules in methanol ...

Haik Chosrowjan - One of the best experts on this subject based on the ideXlab platform.

  • ultrafast solvation dynamics of flavin mononucleotide in the reductase component of p hydroxyphenylacetate hydroxylase
    Journal of Physical Chemistry B, 2009
    Co-Authors: Haik Chosrowjan, Thanawat Phongsak, Seiji Taniguchi, Jeerus Sucharitakul, Pimchai Chaiyen, Noboru Mataga, Fumio Tanaka
    Abstract:

    The reductase unit of p-hydroxyphenylacetate hydroxylase contains flavin mononucleotide (FMN) as a cofactor. Fluorescence decay curves measured by Fluorescence Up-Conversion method were remarkably ...

  • Ultrafast Fluorescence dynamics of FMN-binding protein from Desulfovibrio vulgaris (Miyazaki F) and its site-directed mutated proteins
    Chemical Physics Letters, 2008
    Co-Authors: Haik Chosrowjan, Fumio Tanaka, Seiji Taniguchi, Noboru Mataga, Daisuke Todoroki, Masaya Kitamura
    Abstract:

    Abstract Ultrafast Fluorescence dynamics of FMN in FMN-binding protein (FMN-bp), and its mutated proteins, W32Y and W32A, were investigated by the Fluorescence Up-Conversion method. Fluorescence lifetimes were 167 fs (96%) and 1.5 ps (4%) in wild-type FMN-bp (WT), and 3.4 ps (23%), 18.2 ps (74%), and 96 ps (3%) at 530 nm in W32Y, and 30.1 ps in W32A. The Fluorescence lifetime of W32A, in which Trp-32 was absent, was about 140 times longer than that of WT. Tyr-32 in W32Y was not so effective quencher as Trp-32 in WT. This was explained in terms of different ionization potentials of quenchers and average donor–acceptor distances in the protein.

  • Role of arginine 52 on the primary photoinduced events in the PYP photocycle
    Chemical Physics Letters, 2007
    Co-Authors: Pascale Changenet-barret, Haik Chosrowjan, Seiji Taniguchi, Noboru Mataga, Pascal Plaza, Monique M. Martin, Yasushi Imamoto, Mikio Kataoka
    Abstract:

    International audienceWe investigated the earliest steps of the photocycle of photoactive yellow protein (PYP) and its R52Q mutant in aqueous solution, by subpicosecond transient absorption spectroscopy. Our aim was to address the role of the positively charged Arg52 residue. We found that the relaxation mechanism of R52Q is similar to that of wt-PYP and discarded that Arg52 plays a key role in the chromophore photoreactivity. The excited-state decay of R52Q is however slower, confirming previous Fluorescence Up-Conversion data. The experiments also reveal a slower stabilization of the cis isomer product. The loosening of the protein pocket and structural heterogeneities are discussed

  • Role of arginine 52 on the primary photoinduced events in the PYP photocycle
    Chemical Physics Letters, 2006
    Co-Authors: Pascale Changenet-barret, Haik Chosrowjan, Seiji Taniguchi, Noboru Mataga, Pascal Plaza, Monique M. Martin, Yasushi Imamoto, Mikio Kataoka
    Abstract:

    We investigated the earliest steps of the photocycle of photoactive yellow protein (PYP) and its R52Q mutant in aqueous solution, by subpicosecond transient absorption spectroscopy. Our aim was to address the role of the positively charged Arg52 residue. We found that the relaxation mechanism of R52Q is similar to that of wt-PYP and discarded that Arg52 plays a key role in the chromophore photoreactivity. The excited-state decay of R52Q is however slower, confirming previous Fluorescence Up-Conversion data. The experiments also reveal a slower stabilization of the cis isomer product. The loosening of the protein pocket and structural heterogeneities are discussed.

  • Time and Frequency Domain Investigations on Ultrafast Photoisomerization Reaction Dynamics of PYP
    Springer Series in Chemical Physics, 2005
    Co-Authors: Haik Chosrowjan, Seiji Taniguchi, Noboru Mataga, Norio Hamada, Fumio Tokunaga, Masashi Unno
    Abstract:

    Low frequency modes of PYP (photoactive yellow protein), its several mutant and analogue systems have been investigated by Fluorescence Up-Conversion and resonance Raman scattering techniques, complemented by DFT and ab initio MO calculations. Assignments of the oscillatory components to particular vibrations are proposed. Their role in photoisomerization reaction is discussed.

Dan Huppert - One of the best experts on this subject based on the ideXlab platform.

  • A fresh look into the time-resolved Fluorescence of 8-hydroxy-1,3,6-pyrenetrisulfonate with the use of the Fluorescence Up-Conversion technique
    Journal of Photochemistry and Photobiology A: Chemistry, 2017
    Co-Authors: Ron Simkovitch, Georgi Gary Rozenman, Dan Huppert
    Abstract:

    Abstract Steady-state and time-resolved Fluorescence techniques were used to study the excited-state-proton-transfer (ESPT) process of 8-hydroxy-1,3,6-pyrenetrisulfonate (HPTS) in H 2 O and D 2 O. In this contribution we use the Fluorescence Up-Conversion technique with a time resolution of ∼100 fs to monitor the short-time components of HPTS ROH (protonated) and RO − (deprotonated) signals. The ESPT rate constant, k PT , for HPTS in H 2 O and D 2 O is rather small 10 10 s −1 and 3.3 × 10 9 s −1 , respectively. In the time-resolved Fluorescence signal of the deprotonated form we find a rise-component of 2.5 ps which we assign to slow charge rearrangement as was already suggested by Spry and Fayer [Spry, D. B.; Fayer, M. D. Charge Redistribution and Photoacidity: Neutral Versus Cationic Photoacids. J. Chem. Phys . 2008 , 128, 084508-1–084508-9]. Already in the time-window of 0.2–1.2 ns, the proton geminate recombination (GR) Fluorescence tail of the ROH form decays as t −α where α ≈ 3/2, as predicted by the diffusion-assisted GR model, but for much longer times ( t >  5 ns). We also found that the rotation-relaxation time of the ROH form is about τ or  = 80 ps in H 2 O, shorter than previously reported, whereas in methanol solution, with much lower viscosity, it is much larger – τ or  = 190 ps. We explain this large difference of τ or by counter-ion association on all the three sulfonate groups of HPTS.

  • Ultrafast excited state dynamics of trans-[4-(4′-dimethylaminostyryl)] pyridine N-oxide in solution: femtosecond Fluorescence Up-Conversion and theoretical calculations
    Physical chemistry chemical physics : PCCP, 2013
    Co-Authors: Anna Szemik-hojniak, Dan Huppert, Irena Deperasińska, Krzysztof Oberda, Yuval Erez, Yakov P. Nizhnik
    Abstract:

    The results of the steady-state and time-resolved Fluorescence-spectroscopy measurements and DFT calculations for trans-[4-(4′-dimethylaminostyryl)] pyridine N-oxide (trans-DPO) in various solvents are presented. These results are similar to those reported in the literature for trans-4-(dimethylamino)-4′-cyanostilbene (DCS) where the S1 emissive state shows the charge-transfer (CT) nature. Alcohol solvents, however, have aroused our particular interest because hydrogen-bonded complexes are formed between them and the trans-DPO molecule. They demonstrate a stronger CT character of the lower lying excited state and a larger separation between the first and the second absorption band than in the free trans-DPO molecule. The different effects found in time-dependent femtosecond Up-Conversion (performed for several emission wavelengths in dioxane and methanol solution over the time range 0–40 ps) were assigned to the hydrogen bond assisted charge transfer process in trans-DPO in methanol, to the excited-state solvation dynamics and mainly to solvent relaxation of trans-DPO dissolved in dioxane and methanol.

  • dimethylaminostyryl)) pyridine N-oxide in solution: femtosecond Fluorescence Up-Conversion and theoretical calculations†
    2013
    Co-Authors: Anna Szemik-hojniak, Dan Huppert, Irena Deperasińska, Krzysztof Oberda, Yuval Erez, Yakov P. Nizhnik
    Abstract:

    The results of the steady-state and time-resolved Fluorescence-spectroscopy measurements and DFT calculations for trans-[4-(4 0 -dimethylaminostyryl)] pyridine N-oxide (trans-DPO) in various solvents are presented. These results are similar to those reported in the literature for trans-4-(dimethylamino)-4 0 cyanostilbene (DCS) where the S1 emissive state shows the charge-transfer (CT) nature. Alcohol solvents, however, have aroused our particular interest because hydrogen-bonded complexes are formed between them and the trans-DPO molecule. They demonstrate a stronger CT character of the lower lying excited state and a larger separation between the first and the second absorption band than in the free trans-DPO molecule. The different effects found in time-dependent femtosecond Up-Conversion (performed for several emission wavelengths in dioxane and methanol solution over the time range 0–40 ps) were assigned to the hydrogen bond assisted charge transfer process in trans-DPO in methanol, to the excited-state solvation dynamics and mainly to solvent relaxation of trans-DPO dissolved in dioxane and methanol.

  • Ultrafast excited-state intramolecular proton transfer of aloesaponarin I.
    The journal of physical chemistry. B, 2012
    Co-Authors: Shin-ichi Nagaoka, Hidemitsu Uno, Dan Huppert
    Abstract:

    Time-resolved emission of aloesaponarin I was studied with the Fluorescence Up-Conversion and time-correlated single-photon-counting techniques. The rates of the excited-state intramolecular proton transfer, of the solvent and molecular rearrangements, and of the decay from the excited proton-transferred species were determined and interpreted in the light of time-dependent density functional calculations. These results were discussed in conjunction with UV protection and singlet-oxygen quenching activity of aloe.

  • The impact of solvent polarity on intramolecular proton and electron transfer in 2-alkylamino-4-nitro-5-methyl pyridine N-oxides
    Physical chemistry chemical physics : PCCP, 2012
    Co-Authors: Anna Szemik-hojniak, Irena Deperasińska, Yuval Erez, Ł. Wiśniewski, Artur Makarewicz, Lucjan B. Jerzykiewicz, A. Puszko, Dan Huppert
    Abstract:

    The crystal structure of 2-butylamino-4-nitro-5-methyl pyridine N-oxide (2B5M) and solution studies of both 2B5M and 2-methylamino-4-nitro-5-methyl pyridine (2M5M) N-oxide are presented. Steady-state absorption and emission measurements were employed for both molecules while a picosecond Fluorescence Up-Conversion technique was used to follow the dynamic behavior of the 2M5M system. The experimental methods were complemented by DFT and TD DFT B3LYP/6-31G(d,p) calculations involving ground and excited-state optimization which in the case of the smaller 2M5M molecule were extended to the CAM-B3LYP/6-31G(d,p) method. The solvent effect is incorporated by applying the polarizable continuum (PCM) model. The data reveal that the 2B5M molecule crystallizes in the monoclinic space group P2(1)/c and its crystal lattice is composed of monomers with intramolecular N-H···O [2.572(3) A] hydrogen bonds, connected into a polymer network by weak intermolecular C-H…O [3.2-3.4 A]-type interactions. Quantum-chemical calculations show that the aminoalkyl substitutent in aminoalkyl-pyridine N-oxides is a specific determinant of the CT nature of the lowest-lying excited electronic ππ* state, distinguishing them from other nitroaromatic compounds. The results of both picosecond Fluorescence Up-Conversion experiments in different solvents and quantum-chemical calculations suggest that in nonpolar media the ESIPT process in 2M5M is favored, while in polar acetonitrile, the N* → PT* transition demands barrier-crossing and thus unfavorable thermodynamic conditions do not allow the ESIPT to occur. The signals of picosecond Fluorescence Up-Conversion of 2M5M are solvent- and emission-wavelength dependent. The three time components found in a weakly polar isooctane-dioxane mixture have been attributed to solvation dynamics (∼500 fs), and to relaxation of N* and PT* forms while in acetonitrile, a very rapid Fluorescence decay with a time constant (2.3-4.0 ps) indicative of the presence of the normal (N*) form was observed. Much shorter Fluorescence lifetimes in alcohols (a few picoseconds) and in D(2)O (less than 200 fs) than in aprotic solvents suggest that in protic media, the solvent molecules participate in the ESIPT, bridging between the methylamine group and the N-oxide group of 2M5M.

Shufeng Wang - One of the best experts on this subject based on the ideXlab platform.

  • Ultrafast excited-state dynamics associated with the photoisomerization of a cyanine dye.
    The Journal of chemical physics, 2012
    Co-Authors: Zhenwei Wang, Shufeng Wang, Saisai Chu, Qihuang Gong
    Abstract:

    The ultrafast excited-state dynamics of a cyanine dye, 3,3′-bis(3-sulfopropyl)-5,5′-dimethoxy-thiacyanine triethylaminium salt, was investigated by using conventional time-resolved Fluorescence Up-Conversion technique. The Fluorescence decay can be well described as tri-exponential kinetics, which indicates the excited-state population decays through the bond-twist, vibrational and radiative relaxation channels. Further analysis shows that the contributions of the three relaxation channels to the Fluorescence decay demonstrate very different change with increasing the Fluorescence wavelength, through which the detailed dynamics at different regions in the excited-state potential energy surface can be retrieved.

  • Steady-state and transient-state optical properties of a charge-transfer composite material MO-PPV/SWNTs
    Chemical Physics Letters, 2007
    Co-Authors: Saisai Chu, Shufeng Wang, Wenke Feng, Qihuang Gong
    Abstract:

    Abstract Charge-transfer composite material, poly-1-methoxy-4-octoxy-(para-phenelene vinylene) (MO-PPV) wrapped single wall carbon nanotubes (SWNTs), MO-PPV/SWNTs, was synthesized by in situ polymerization. Photophysics properties of MO-PPV/SWNTs were studied by using steady-state spectra, femtosecond Fluorescence Up-Conversion technique, and streak camera. Compared with the pure MO-PPV in solution, Fluorescence quenching was observed. Photoinduced electron-transfer from MO-PPV to SWNTs occurs on femtosecond timescale, while photoinduced intermolecular energy-transfer appears at ∼100 ps timescale.

  • Broadband parametric amplification in ultrafast Fluorescence application
    Chinese Optics Letters, 2005
    Co-Authors: Shufeng Wang, Qihuang Gong
    Abstract:

    Broadband parametric amplification is applied for the femtosecond ultrafast Fluorescence research. The time resolution depends on duration of pump pulse, which works both as pump source and gate. For spectrum application, a special phase-matching angle exists for broadband amplification correspondence to the pump wavelength. The broadband amplification range from 500 to 750 nm was found for 'beta'-barium borate (BBO) crystal, pumped at 400 nm. Large dye Fluorescence amplification of 10^(7) is realized. The generation of cone emission is selected as reference for system tuning. It is supposed to be a new method for ultrafast study in Fluorescence comparable to Fluorescence Up-Conversion and optical Kerr gate techniques.

  • Ultrafast excited state dynamics of polybenzonitrile investigated by using femtosecond time-resolved Fluorescence Up-Conversion
    Journal of Luminescence, 2002
    Co-Authors: Tieqiao Zhang, Keitaro Yoshihara, Shufeng Wang, Hong Yang, Wentao Huang, Qihuang Gong, Qian Wang, Jiagang Luo, Huiying Chen
    Abstract:

    Abstract The photoluminescence dynamics of a new polymer, (–CN–) conjugated polybenzonitrile, was investigated with a femtosecond time-resolved Fluorescence Up-Conversion technique. The experimental results revealed a bi-exponential relaxation dynamics for excited state and it was explained with the photo-generated excitons’ migration model.

  • Photophysical Studies on the Mono- and Dichromophoric Hemicyanine Dyes III. Ultrafast Fluorescence Up-Conversion in Methanol: Twisting Intramolecular Charge Transfer and "Two-State Three-Mode" Model
    The Journal of Physical Chemistry B, 2002
    Co-Authors: Yanyi Huang, Shufeng Wang, Tianrong Cheng, Chunhui Huang, And Wentao Huang, Qihuang Gong
    Abstract:

    A series of hemicyanine dyes, including monomer ([(E)-N-methyl-4-(2-(4-N,N-dimethyl phenyl) ethenyl) pyridinium] iodide; M) and dimers (1,n-Bis [(E)- 4-(2-(4-N,N-dimethyl phenyl) ethenyl) pyridinyl]-alkane dibromide; n = 3, alkane = propane, B3; n = 5, alkane = pentane, B5; n = 12, alkane = dodecane, B12), are synthesized and their ultrafast Fluorescence Up-Conversion behaviors are studied. The Fluorescence decay curves of these dyes can be well fitted by the sum of several exponential decays in the shorter wavelengths and by the sum of the exponential rise(s) with decay(s) in the longer wavelengths. The fact that the values of longest lifetime component at longer wavelengths tend to be a constant proves the existence of a “sink” region on the potential energy surface of excited state. This sink region is around the TICT state, by which the nonradiative transition dominates the deactive decay paths of excited state. The time dependent Stokes shift function analysis of these four dye molecules in methanol ...