A5090600056- Spectroscopy and Quantum Chemical Studies
- Spectroscopy Techniques in Biomedical and Chemical Research
- Photochemistry and Electron Transfer Studies
- X-ray Diffraction in Crystallography
- Crystallization and Solubility Studies
- Photoreceptor and optogenetics research
- Advanced Photocatalysis Techniques
- Spectroscopy and Chemometric Analyses
- Porphyrin and Phthalocyanine Chemistry
- Perovskite Materials and Applications
- Luminescence and Fluorescent Materials
- TiO2 Photocatalysis and Solar Cells
- Free Radicals and Antioxidants
- Organic Electronics and Photovoltaics
- Photosynthetic Processes and Mechanisms
- Laser-Matter Interactions and Applications
- DNA and Nucleic Acid Chemistry
- Molecular spectroscopy and chirality
- Conducting polymers and applications
- Quantum Dots Synthesis And Properties
- Advanced Nanomaterials in Catalysis
- Advanced biosensing and bioanalysis techniques
- Crystallography and molecular interactions
- Organic Light-Emitting Diodes Research
- Electrocatalysts for Energy Conversion
University of Rochester
2013-2024
China Jiliang University
2012
The Ohio State University
2010
University of Hong Kong
2010
Northwestern University
2006-2008
Northwest University
2007
University of California, Berkeley
2001-2006
The primary event that initiates vision is the light-induced 11-cis to all-trans isomerization of retinal in visual pigment rhodopsin. Despite decades study with traditional tools chemical reaction dynamics, both timing and nature atomic motions lead photoproduct production remain unknown. We used femtosecond-stimulated Raman spectroscopy obtain time-resolved vibrational spectra molecular structures formed along coordinate. spectral evolution features from 200 femtoseconds 1 picosecond after...
Abstract Reduced-dimensional perovskites are attractive light-emitting materials due to their efficient luminescence, color purity, tunable bandgap, and structural diversity. A major limitation in perovskite diodes is limited operational stability. Here we demonstrate that rapid photodegradation arises from edge-initiated photooxidation, wherein oxidative attack powered by photogenerated electrically-injected carriers diffuse the nanoplatelet edges produce superoxide. We report an...
The laser, detection system, and methods that enable femtosecond broadband stimulated Raman spectroscopy (FSRS) are presented in detail. FSRS is a unique tool for obtaining high time resolution (<100 fs) vibrational spectra with an instrument response limited frequency of <10 cm−1. A titanium:Sapphire-based laser system produces the three different pulses needed FSRS: (1) visible actinic pump initiates photochemistry, (2) narrow bandwidth picosecond provides energy reservoir...
We have developed the technique of femtosecond stimulated Raman spectroscopy (FSRS), which allows rapid collection high-resolution vibrational spectra on time scale. FSRS combines a sub-50 fs actinic pump pulse with two-pulse probe to obtain whose frequency resolution limits are uncoupled from resolution. This acquisition <100 and <30 cm(-1) Additionally, is unaffected by background fluorescence, provides (100 ms) times, exhibits traditional spontaneous line shapes. used here study...
Photoexcitation of a series donor−bridge−acceptor (D−B−A) systems, where D = phenothiazine (PTZ), B p-phenylene (Phn), n 1−5, and A perylene-3,4:9,10-bis(dicarboximide) (PDI) results in rapid electron transfer to produce 1(PTZ+•−Phn−PDI-•). Time-resolved EPR (TREPR) studies the photogenerated radical pairs (RPs) show that above 150 K, when 2−5, pair−intersystem crossing mechanism (RP−ISC) produces spin-correlated ion having spin polarization patterns indicating spin−spin exchange interaction...
A series of halogenated boron-dipyrromethene (Bodipy) chromophores with potential applications in solar energy conversion were synthesized and characterized by steady state ultrafast laser spectroscopy. The dynamics the compared between a containing H, Br, or I at 2,6 positions Bodipy dye. parent has fluorescent lifetime (τfl) 3−5 ns, fluorescence quantum yield (Φfl) 0.56, negligible triplet yield. Bromination enhances intersystem crossing (ISC) such that τfl Φfl decrease to ∼1.2 ns 0.11,...
The dyads 3, 4, and 6, combining the Bodipy chromophore with a Pt(bpy)(bdt) (bpy = 2,2'-bipyridine, bdt 1,2-benzenedithiolate, 3 6) or Pt(bpy)(mnt) (mnt maleonitriledithiolate, 4) moiety, have been synthesized studied by UV-vis steady-state absorption, transient emission spectroscopies cyclic voltammetry. Comparison of absorption spectra voltammograms 6 those their model compounds 1a, 2, 5, 7 shows that spectroscopic electrochemical properties are essentially sum constituent chromophores,...
Femtosecond broadband stimulated Raman spectroscopy (FSRS) is a new technique that produces high-resolution (time-resolved) vibrational spectra from either the ground or excited electronic states of molecules, free background fluorescence. FSRS uses simultaneously narrow bandwidth approximately 1-3 ps pump pulse with continuum 30-50 fs Stokes probe to produce sharp gains, at positions corresponding transitions in sample, riding on top spectrum. When preceded by femtosecond actinic initiates...
Femtosecond time-resolved stimulated Raman spectroscopy (FSRS) is used to examine the photoisomerization dynamics in excited state of bacteriorhodopsin. Near-IR emission observed FSRS probe window that decays with a 400−600-fs time constant. Additionally, dispersive vibrational lines appear at locations ground-state frequencies and decay 260-fs The line shapes are caused by nonlinear effect we term initiated (RINE) generates coherence on surface. Theoretical expressions for RINE developed...
Femtosecond stimulated Raman spectroscopy (FSRS) is a new technique that produces high-quality vibrational spectra free from background fluorescence. FSRS combines narrow-bandwidth picosecond pump pulse with an ∼80 fs continuum probe to produce the pump-induced gain in spectrum. The high intensity of combined broad bandwidth signal-to-noise very short data acquisition times. standard solutions and solvents such as aqueous Na 2 SO 4 , KNO 3 methanol, isopropanol, cyclohexane are collected...
The electronic and vibrational structure of beta-carotene's early excited states are examined using femtosecond time-resolved stimulated Raman spectroscopy. spectrum the short-lived ( approximately 160 fs) second singlet state (S(2),1B(u) (+))of beta-carotene is obtained. Broad, resonantly enhanced features observed at 1100, 1300, 1650 cm(-1) that decay with a time constant corresponding to lifetime S(2). temporal evolution spectra consistent significant population only two low-lying (1B(u)...
New platinum(II) terpyridyl acetylide complexes having the ability to bind TiO(2) have been synthesized and assayed in their sensitize platinized titanium dioxide for photogeneration of H(2) using visible light (lambda > 410 nm). Specifically, [Pt(tpy-phen-COOH)(C[triple bond]C-C(6)H(5))]Cl (1), where tpy-phen-COOH = 4'-(4-carboxyphenyl)-[2,2';6',2'']terpyridine C[triple bond]C-C(6)H(5) phenylacetylide, [Pt(tpy-COOH)(C[triple (2), tpy-COOH 4'-carboxy-2,2';6',2''-terpyridine, were prepared...
We report on the synthesis of hybrid molecules consisting a porphyrin or corrole chromophore axially coordinated to [CoIII(dmgH)2(Cl)]±0 (dmg = dimethylglyoxime) unit via pyridine group as potential hydrogen forming entities in H2O/THF medium. Photophysical, electrochemical, and pulse radiolysis studies hybrids and/or their separate components show that selective excitation its first singlet excited state leads fast charge separation due cobalt electron transfer. However, this is followed by...
Significance The light-driven generation of H 2 , the reductive side water splitting, requires a light absorber or photosensitizer (PS) for electron-hole creation and photoinduced electron transfer. To increase effectiveness charge transfer chromophores as PSs, this report describes attachment strongly absorbing organic dye (dipyrromethene-BF commonly known Bodipy) to Pt diimine dithiolate examination systems containing these dyads . use increases system activity under green irradiation (530...
4-(Dimethylamino)benzonitrile (DMABN) has been one of the most studied photoinduced charge-transfer (CT) compounds for over 50 years, but due to complexity its excited electronic states and importance both intramolecular solvent reorganization, detailed microscopic mechanism CT is still debated. In this work, we have probed ultrafast process DMABN in methanol using broad-band transient absorption spectroscopy from 280 620 nm ultraviolet femtosecond stimulated Raman (FSRS) incorporating a 330...
A series of Boron-dipyrromethene (Bodipy) dyes were used as photosensitizers for photochemical hydrogen production in conjunction with [Co(III)(dmgH)2pyCl] (where dmgH = dimethylglyoximate, py pyridine) the catalyst and triethanolamine (TEOA) sacrificial electron donor. The Bodipy are fully characterized by electrochemistry, X-ray crystallography, quantum chemistry calculations, femtosecond transient absorption, time-resolved fluorescence, well long-term assays. Consistent other recent...
The first step of photosynthesis is the absorption light by antenna complexes. Recent studies light-harvesting complexes using two-dimensional electronic spectroscopy have revealed interesting coherent oscillations. Some contributions to those coherences are assigned coherence and therefore implications for theories energy transfer. To assign these femtosecond data gain insight into interplay among vibrational resonances, we need detailed information on vibrations in excited state compared...
Three new dyads consisting of a rhodamine (RDM) dye linked covalently to Pt diimine dithiolate (PtN2S2) charge transfer complex were synthesized and used as photosensitizers for the generation H2 from aqueous protons. The three differ only in substituents on amino groups, are denoted Pt-RDM1, Pt-RDM2, Pt-RDM3. In acetonitrile, show strong absorption visible region corresponding π–π* well mixed metal-dithiolate-to-diimine band characteristic PtN2S2 complexes. shift maxima going Pt-RDM1...
Establishing the fundamental chemical principles that govern molecular electronic quantum decoherence has remained an outstanding challenge. Fundamental questions such as how solvent and intramolecular vibrations or functionalization contribute to remain unanswered are beyond reach of state-of-the-art theoretical experimental approaches. Here we address this challenge by developing a strategy isolate pathways for chromophores immersed in condensed phase environments enables elucidating...
Density functional theory (DFT) and time-dependent DFT (TD-DFT) are pivotal approaches for modeling electronically excited states of molecules. However, choosing a exchange-correlation (XCF) among the myriad alternatives is an overwhelming task that can affect interpretation results lead to erroneous conclusions. The performance these XCFs describe excited-state properties often addressed by comparing them with high-level wave function methods or experimentally available vertical excitation...
Understanding how the electronic structures of electron donor−bridge−acceptor (D−B−A) molecules influence lifetimes radical ion pairs (RPs) photogenerated within them (D+•−B−A-•) is critical to designing and developing molecular systems for solar energy conversion. A general question that often arises whether HOMOs or LUMOs D, B, D+•−B−A-• are primarily involved in charge recombination. We have developed a new series D−B−A consisting 3,5-dimethyl-4-(9-anthracenyl)julolidine (DMJ-An) donor...
Picosecond time-resolved Stokes and anti-Stokes resonance Raman spectra of all-trans-beta-carotene are obtained analyzed to reveal the dynamics excited-state (S(1)) population decay, as well ground-state vibrational relaxation. Time-resolved show that ground state recovers with a 12.6 ps time constant, in agreement observed decay unique S(1) bands. The exhibit no peaks attributable (2A(g) (-)) state, indicating relaxation must be nearly complete within 2 ps. After photoexcitation there is...
A new methodology for two-dimensional Raman spectroscopy-termed femtosecond stimulated spectroscopy (2D-FSRS)-is presented and experimental results acetonitrile are discussed. 2D-FSRS can potentially observe molecular anharmonicity by measuring the modulation of frequency a probed mode, at omega(hi), coherent motion an impulsively driven omega(low). In acetonitrile, signal is generated driving CCN bend (379 cm(-1)) CC stretch (920 into coherence via impulsive scattering subsequently probing...