Eighth Condensed Phase and Interfacial Molecular Science (CPIMS)

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surface results in two excess electrons occupying 3d orbitals on Ti atoms neighboring the vacancy. With laser excitation, electrons at the valence band can be excited to higher energy states, for example, trap states below the conduction band. Figure 3. Optical response of the abundant surface states of the Nb-doped rutile TiO2 (110) surface. (A1) Confocal imaging and (A2) Raman/luminescence spectra of TiO2 (110) surface. (B1) Confocal imaging and (B2) Raman/luminescence spectra of TiO2 (110) surface with alizarin (1 �M). Probing Single-Electron Self-Exchange Dynamics Across a Molecule-Metal Interface. For a redox reaction, the key processes are the electron transfer between the reductant and oxidant and subsequently produce the reduced states or oxidized states of chemical species. Therefore, electron transfer dynamics is the core of the redox reaction dynamics. The probability for the molecule to stay in the oxidized state is high when the gate voltage is far greater than the formal redox potential. For a metal-molecule-metal junction, current-induced metal-atom motions, molecular conformation changes, and chemical bond fluctuations have been suggested to be the chemical and mechanical reasons of the fluctuations. On the other hand, the fluctuation of the conductance in a single molecule-metal junction is coincident with the fluctuation and inhomogeneity of the single molecule dynamics. Figure 4. (Left Panel) Time dependant SERS spectra of Hemin (1.4 nM) adsorbed on Ag NP surfaces. Typical vibrational modes, ν4, ν3, ν2, and ν10, are prominent but show strong fluctuation at the single molecule level. Four consecutive spectra, which show the evolution of ν4 from the oxidized state to the reduced state, are shown as a zoom-in view. (Right Panel) The thermally driven redox reaction of single Co(II)Pc molecules at the Au (111) surface with a reduction potential of 0.1 V vs. SCE at (A) 0 min (B) 1 min (C) 2 min. The fluctuation of the brightness of a single molecule indicates the oxidation states changes. The ground-state single-electron charge transfer dynamics at the Hemin/Ag NP interface hasbeen investigated by using SMSERS and spectroelectrochemistry. The electron transfer at the Hemin/Ag interface is evidenced by the prominent shift of a specific Raman mode ν4, which is a typical marker of the oxidation state of the Iron center in Hemin. The fluctuation dynamics of the Raman spectra has been quantitatively investigated by the autocorrelation and crosscorrelation function analysis. On the basis of the data analysis and combined with the single-molecule spectroelectochemistry control measurements, we suggest that the single molecule redox reaction at the Hemin/Ag interface is primarily driven by thermal fluctuation. The ground-state single-electron charge transfer events at the Hemin/Ag NP interface naturally exist, and it is different from the charge-transfer enhancement factor in SERS. This work reveals a real-time picture of the charge transfer dynamics at the 125
molecule-metal interface without a strong electric field. Our new information is relevant for a further understanding, design, and manipulation of the charge transfer processes at the moleculemetal interfaces or metal-molecule-metal junctions, which are fundamental elements in singlemolecule electronics, catalysis, and solar energy conversion. Future Research Plans Interfacial ET dynamics strongly involves with and regulated by molecule-surface interactions. To decipher the underlying mechanism of the complex and inhomogeneous interfacial electron transfer dynamics, we plan to study interfacial electron transfer on single crystal TiO2 surfaces by using pump-probe ultrafast single-molecule spectroscopy and near-field scanning microscopy. Our study will focus on understanding the interfacial electron transfer dynamics at specific crystal sites (kinks, planes, lattices, and corners) with high-spatially and temporally resolved topographic/spectroscopic characterization at individual molecule basis, characterizing single-molecule rate processes, reaction driving force, and molecule-substrate electronic coupling. Our effort will also be focused on understanding the TiO2 electron trap centers and surface states. Publications of DOE sponsored research (FY2009-2012) 1. Desheng Zheng, Leonora Kaldaras, H. Peter Lu, “Total Internal Reflection Fluorescence Microscopy Imaging-Guided Confocal Single-Molecule Fluorescence Spectroscopy,” Review of Scientific Instruments, 83, 013110 (2012). 2. X. Wang, D. Zhang, Y. Wang, P. Sevinc, H. Peter, Lu, A. J. Meixner, “Interfacial Electron Transfer Energetics Studied by High Spatial Resolution Tip-Enhanced Raman Spectroscopic Imaging,” Angewandte Chemie International Edition 50, (2011) A25-A29. 3. Yuanmin Wang, Papatya C. Sevinc, Yufan He, H. Peter Lu, "Probing Ground-State Single- Electron Self-Exchange Across a Molecule-Metal Interface," J. Am. Chem. Soc., 133, 6989-6996 (2011). 4. Sevinc, Papatya; Wang, Xiao; Wang, Yuanmin; Zhang, Dai; Meixner, Alfred; Lu, H. Peter, "Simultaneous Spectroscopic and Topographic Near-Field Imaging of TiO2 Single Surface States and Interfacial Electronic Coupling," Nano Letter, 11, 1490-1494 (2011). 5. H. Peter Lu, "Acquiring a Nano-View of Single Molecules in Actions," Nano Reviews 1, 6-7 (2010). 6. Guo, Lijun; Wang, Yuanmin; Lu, H. Peter, "Combined Single-Molecule Photon-Stamping Spectroscopy and Femtosecond Transient Absorption Spectroscopy Studies of Interfacial Electron Transfer Dynamics," J. Am. Chem. Soc. 132, 1999-2004 (2010) (Cover page). 7. Yufan He, Xiaohua Zeng, Saptarshi Mukherjee, Suneth Rajapaksha, Samuel Kaplan, H. Peter Lu, "Revealing Linear Aggregates of Light Harvesting Antenna Proteins in Photosynthetic Membranes," Langmuir 26, 307-313 (2010) (Cover page). 8. Yuanmin Wang, Xuefei Wang, and H. Peter Lu, "Probing single-molecule interfacial geminate electron-cation recombination dynamics,” J. Am. Chem. Soc. 131, 9020–9025 (2009). 9. Yuanmin Wang, Xuefei Wang, Sujit Kumar Ghosh, H. Peter Lu, "Probing single-molecule interfacial electron transfer dynamics of porphyrin on TiO2 nanoparticles," J. Am. Chem. Soc. 131, 1479-1487 (2009). 126
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Eighth Condensed Phase and Interfac
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Potential energy landscape of the (
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Agenda
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Session III Chair: Jay A. LaVerne,
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Table of Contents
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Transition Metal-Molecular Interact
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Ultrafast Electron Transport across
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CPIMS Principal Investigator Abstra
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VUV LDPI image of a polymer photore
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Publications based on DOE support (
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entirely quenched, presumably due t
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Future Plans In addition to the TiO
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The relative path indexes of the ur
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We have recently carried out molecu
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have been obtained with γ-rays sug
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Two novel plasma devices have been
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(Figure 2) can be adsorbed exclusiv
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3. Future Plans Our planned work de
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Figure 1: Snap shots from molecular
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6. Varilly, P., A. J. Patel and D.
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hypothesis that delocalized charges
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Efforts will be made to observe ele
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Photochemistry and Solvation Dynami
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complementary to work we have carri
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The Co3O4 films for the optical pum
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chamber will allow us to heat the s
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calculations. Additional PMF calcul
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the gas solute first needs to cross
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laser system, which is an infrared
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Publications (10/1/2009-present) fo
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interest are: (i) What is the diffu
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and anilino groups attached to the
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had been formed. This coincides wit
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Figure 1. (A) Simplified bR photocy
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Figure 4. Photocurrent density of b
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single-file diffusion and cannot ca
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PUBLICATIONS SUPPORTED BY USDOE CHE
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arrangement. However, the hydrogen
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(5) “Water Dynamics in Salt Solut
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from high- energy x-ray diffraction
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concentrated aqueous solutions. The
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molecule’s center of mass, or alt
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Moreover, SHG studies by Saykally
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The effective fragment potential (E
Page 89 and 90: 10. D.D. Kemp, J. Rintelman, M.S. G
Page 91 and 92: temperature dependent, equilibrium
Page 93 and 94: mimicking real organic photovoltaic
Page 95 and 96: 100 kHz amplifier, SE-FSRS was succ
Page 97 and 98: photovoltaics will be explored via
Page 99 and 100: for laser surface reactions to thes
Page 101 and 102: This is a significant advantage of
Page 103 and 104: the STM, which might underlie the u
Page 105 and 106: Future Plans: Figure 3. One and two
Page 107 and 108: methane molecule and a lattice atom
Page 109 and 110: eactive than the Ni, experiment sug
Page 111 and 112: Fig. 1. PE spectra of M3Oy � (M =
Page 113 and 114: each of the intermediates obtained
Page 115 and 116: a regime where each solvent molecul
Page 117 and 118: observables that arise from subtle
Page 119 and 120: total potentials. One can see from
Page 121 and 122: Our calculations have shown that ch
Page 123 and 124: our understanding of structure and
Page 125 and 126: viscosity, η, are inversely relate
Page 127 and 128: photodissociation of the metal - NO
Page 129 and 130: from a Ru 2p3/2 orbital to an orbit
Page 131 and 132: Integrated O 2 PSD (ML) Integrated
Page 133 and 134: anisotropy in the structure of the
Page 135 and 136: XPS studies have been performed on
Page 137 and 138: Publications with BES support since
Page 139: MLCT (metal to ligand charge transf
Page 143 and 144: observe the predicted effects, whic
Page 145 and 146: (4*) Lymar, S. V.; Schwarz, H. A. J
Page 147 and 148: (τ .820 ns), but we have not been
Page 149 and 150: B. Photodissociation spectroscopy o
Page 151 and 152: oth BLYP and PBE. Our results have
Page 153 and 154: Publications from BES support (2010
Page 155 and 156: understanding of factors that contr
Page 157 and 158: Our talk will discussion our initia
Page 159 and 160: Figure 1 shows the band structure o
Page 161 and 162: likely to also occur in low coordin
Page 163 and 164: These results are promising indicat
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Page 167 and 168: method recently developed by Prende
Page 169 and 170: and coordination regions. A differe
Page 171 and 172: two ions I - [3] and IO3 - [7]. One
Page 173 and 174: "Probing the Hydration Structure of
Page 175 and 176: world-wide scientific user base sup
Page 177 and 178: 10) C. Zhang, M.E. Grass, A.H. McDa
Page 179 and 180: produce the nanoparticles needed fo
Page 181 and 182: step as a symmetry-breaking templat
Page 183 and 184: work provides what we believe in th
Page 185 and 186: Selected publications acknowledging
Page 187 and 188: 2. Optical Stark study of PtF (Acce
Page 189 and 190: Figure 4. The Q(3.5) line of the [1
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In marked contrast to the selective
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y depositing cobalt onto copper sin
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Carlo calculations, we have carried
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approach on a model phenol-amine pr
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We performed pump-probe experiments
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15. “A phenomenological approach
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may be initially produced in a non-
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4. Inelastic scattering of hydrogen
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Using QM/MM free energy methods we
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This page is intentionally left bla
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gas phase using electrospray ioniza
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order of Li + > Na + > K + for comp
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2. MM Meyer, XB Wang, CA Reed, LS W
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Technical Approach and Progress to
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Ionic liquid synthesis and characte
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Studies of structure and reaction d
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structure theory that include elect
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9. S. Pandelov, J. C. Werhahn, B. M
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pulse duration is a few times longe
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Figure 1 (Left) The HOMO and LUMO e
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slightly preferable in energy, the
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Participant List Dr. Musahid Ahmed
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Professor Kenneth Eisenthal Columbi
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Dr. Ireneusz Janik Notre Dame Radia
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Professor Eric Potma University of
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Dr. James Wishart Brookhaven Nation
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Eighth Condensed Phase and Interfacial Molecular Science (CPIMS)

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