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Ultrafast Investigation of Excited-State Dynamics in Trans-4-methoxyazobenzene Studied by femtosecond transient absorption spectroscopy

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Chinese Journal of Chemical Physics 2018年第6期31卷 749-755,733页

作者： Ya-ping Wang Chun-hua Li Bing Zhang Chen Qin Song Zhang School of Electronic Science & Applied Physics Hefei University of Technology Hefei 230009 China State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics Wuhan Institute of Physics and Mathematics Chinese Academy of Sciences Wuhan 430071 China Key Laboratory of Mineral Luminescent Material and Microstructure of Xinjiang School of Physics and Electronic Engineering Xinjiang Normal University Urumqi 830054 China

The ultrafast photoisomerization and excited-state dynamics of trans-4-methoxyazobenzene (trans-4-MAB) in solutions were investigated by femtosecond transient absorption spectroscopy and quantum chemistry calculations. After being excited to the S2 state, the two-dimensional transient absorptions spectra show that cis-4-MAB is produced and witnessed by the permanent positive absorption in 400-480 nm. Three decay components are determined to be 0.11, 1.4 and 2.9 ps in ethanol, and 0.16, 1.5 and 7.5 ps in ethylene glycol, respectively. The fast component is assigned to the internal conversion from the S2 to S1 state. The other relaxation pathways are correlated with the decay of the S1 state via internal conversion and isomerization, and the vibrational cooling of the hot S0 state of the cis-isomer. Comparing of the dynamics in different solvents, it is demonstrated that the photoisomerization pathway undergoes the inversion mechanism rather than the rotation mechanism.

关键词： Photoisomerization Trans-4-methoxyazobenzene femtosecond transient absorption spectroscopy

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Hydrogen Bonding Effects on the Photophysical Properties of 2,3-dihydro-3-keto- 1H-pyrido[3,2,1-kl] phenothiazine

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Chinese Journal of Chemical Physics 2012年第3期25卷 254-260,373页

作者： Song-qiu Yang Guo-zhong He State Key Laboratory of Molecular Reaction Dynamics Dalian Institute of Chemical Physics ChineseAcademy of Sciences Dalian 115023 China Graduate School of the Chinese Academy of Sciences Beijing 100039 China

Time-dependent density functional theory （TDDFT） and femtosecond transient absorption spectroscopy were used to investigate the photophysical properties of 2,3-dihydro-3-keto-lH- pyrido[3,2,1-kl]phenothiazine （PTZ4） and 3-keto-lH-pyrido[3,2,1-kl]phenothiazine （PTZ5）. The calculated results obtained from TDDFT suggest that the red-shifts of the absorption spectra of these two fluorophores in methanol are due to the formation of hydrogen-bonded complexes at the ground state. Four conformers of PTZ4 were obtained by TDDFT. The two fluorescence peaks of PTZ4 in tetrahydrofuran （THF） came from the ICT states of the four conformers. The fluorescence of PTZ4 in THF showed a dependence on the excitation wavelength because of butterfly bending. The excited state dynamics of PTZ4 in THF and methanol were obtained by transient absorption spectroscopy. The lifetime of the excited PTZ4 in methanol was 53.8 ps, and its relaxation from the LE state to the ICT state was completed within several picoseconds. The short lifetime of excited PTZ4 in methanol was due to the formation of out-of-plane model hydrogen bonds between PTZ4 and methanol at the excited state.

关键词： 2,3-dihydro-3-keto-lH-pyrido[3,2,1-kl]phenothiazine Time-dependent densityfunctional theory femtosecond transient absorption spectroscopy Hydrogen bonding effect

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Ultrafast proton transfer dynamics of 2-(2'-hydroxyphenyl)benzoxazole dye in different solvents

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Chinese Physics B 2022年第2期31卷 606-612页

作者： Simei Sun Song Zhang Jiao Song Xiaoshan Guo Chao Jiang Jingyu Sun Saiyu Wang Huangshi Key Laboratory of Photoelectric Technology and Materials College of Physics and Electronic ScienceHubei Normal UniversityHuangshi 435002China State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics Innovation Academy for Precision Measurement Science and TechnologyChinese Academy of SciencesWuhan 430071China Hubei Key Laboratory of Pollutant Analysis&Reuse Technology College of Chemistry and Chemical EngineeringHubei Normal UniversityHuangshi 435002China

The excited-state intramolecular proton transfer of 2-(2-hydroxyphenyl)benzoxazole dye in different solvents is investigated using ultrafast femtosecond transient absorption spectroscopy combined with quantum chemical *** conversion from the syn-enol configuration to the keto configuration is proposed as the mechanism of excited-state intramolecular proton *** duration of excited-state intramolecular proton transfer is measured to range from 50 fs to 200 fs in different *** time is strongly dependent on the calculated energy gap between the N-S;and T-S;structures in the S;*** the proton transfer reaction coordinate,the vibrational relaxation process on the S;state potential surface is *** duration of the vibrational relaxation process is determined to be from8.7 ps to 35 ps dependent on the excess vibrational energy.

关键词： proton transfer vibrational relaxation femtosecond transient absorption spectroscopy quantum chemical calculations

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Rebinding kinetics of dissociated amino acid ligand and carbon monoxide to ferrous microperoxidase-11 in aqueous solution

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Science China Chemistry 2013年第2期56卷 230-237页

作者： ZHONG RangBo LU Rong YU AnChi Department of Chemistry Renmin University of China

The rebinding kinetics of an amino acid ligand to ferrous microperoxidase-11 (MP11) after photolysis of aggregated ferrous MP11 was measured in aqueous solution with femtosecond transient visible absorption spectroscopy. The kinetics of CO rebinding to ferrous MP11 after photolysis of MP11CO was also measured in aqueous solution with femtosecond transient visible absorption spectroscopy. From these measurements, we found that either Val-11 or Lys-13 rebinds to ferrous MP11 exponentially with an 8 picosecond time constant in aggregated ferrous MP11 solution and that CO rebinds to ferrous MP11 nonexponentially with subnanosecond time scale in MP11CO solution. The kinetics of both the amino acid and CO rebinding to ferrous MP11 in MP11 system mimics that in carbon monoxide oxidation activator protein (CooA) or carboxymethyl cytochrome c (CmCytC) system. We also measured the kinetics of CO rebinding to ferrous MP11 in aqueous solution at different MP11CO concentrations and found that MP11CO concentration has an obvious effect on the kinetics of CO rebinding to ferrous MP11, where both the germinate yield and rate of CO rebinding to ferrous MP11 increase with the increase of MP11CO concentration. These findings suggested that the picosecond amino acid ligand rebinding process could disturb the proximal heme-ligand structure that possibly leads to the subnanosecond CO rebinding kinetics in MP11CO, CooACO and CmCytCCO systems.

关键词： femtosecond transient absorption spectroscopy ferrous microperoxidase-11 concentration-dependent recombination kinetics aggregation tendency carbon monoxide

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Shell thickness dependence of plasmon-induced hot electron injection process in Core/Shell Au@CdS Nanocrystals

Shell thickness dependence of plasmon-induced hot electron i...

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第十五届全国化学动力学会议

作者：董慧纺 Hailong Chen Yuxiang Weng Jingwen Feng Jia Liu Jiatao Zhang Key Laboratory of Soft Matter Physics of CAS Institute of Physics School of Materials Science Beijing Institute of Technology

Finding the essential mechanism for hot electron injection of metal-semiconductor is of of vital importance for improving the solar energy utilization ratio in photocatalytic *** transient absorption spectroscopy is used to detect a series of Au@CdS nanocrystals to explore the shell thickness dependence of plasmon-induced hot electron injection *** interface of Au core and CdS shell forms a Schottky *** depicted in Figure 1:Plasmon induced hot electrons in Au core are excited from the occupied levels below the Fermi energy to unoccupied levels above the Fermi *** distribution joint density of state（EDJDOS）gives the distribution of hot electrons in Au core,but the hot electrons will cool down in a few 100 fs due to electron-electron *** hot electrons must arrive at the CdS shell before lossing energy,then the hot electrons with enough energy above Schottky barrier potential can inject into the CdS shell.A highly significant finding exists in our study:the shell thickness can change the height of the Schottky barrier,thus injection efficiency could be tuned by changing the CdS shell thickness.

关键词： Plasmon femtosecond transient absorption spectroscopy EDJDOS Schottky barrier Hot electron injection

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