1
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Islam MM, Nawagamuwage SU, Parshin IV, Richard MC, Burin AL, Rubtsov IV. Probing the Hydrophobic Region of a Lipid Bilayer at Specific Depths Using Vibrational Spectroscopy. J Am Chem Soc 2023; 145:26363-26373. [PMID: 37982703 DOI: 10.1021/jacs.3c10178] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2023]
Abstract
A novel spectroscopic approach for studying the flexibility and mobility in the hydrophobic interior of lipid bilayers at specific depths is proposed. A set of test compounds featuring an azido moiety and a cyano or carboxylic acid moiety, connected by an alkyl chain of different lengths, was synthesized. FTIR data and molecular dynamics calculations indicated that the test compounds in a bilayer are oriented so that the cyano or carboxylic acid moiety is located in the lipid head-group region, while the azido group stays inside the bilayer at the depth determined by its alkyl chain length. We found that the asymmetric stretching mode of the azido group (νN3) can serve as a reporter of the membrane interior dynamics. FTIR and two-dimensional infrared (2DIR) studies were performed at different temperatures, ranging from 22 to 45 °C, covering the Lβ-Lα phase transition temperature of dipalmitoylphosphatidylcholine (∼41 °C). The width of the νN3 peak was found to be very sensitive to the phase transition and to the temperature in general. We introduced an order parameter, SN3, which characterizes restrictions to motion inside the bilayer. 2DIR spectra of νN3 showed different extents of inhomogeneity at different depths in the bilayer, with the smallest inhomogeneity in the middle of the leaflet. The spectral diffusion dynamics of the N3 peak was found to be dependent on the depth of the N3 group location in the bilayer. The obtained results enhance our understanding of the bilayer dynamics and can be extended to investigate membranes with more complex compositions.
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Affiliation(s)
- Md Muhaiminul Islam
- Department of Chemistry, Tulane University, New Orleans, Louisiana 70118, United States
| | | | - Igor V Parshin
- Department of Chemistry, Tulane University, New Orleans, Louisiana 70118, United States
| | - Margaret C Richard
- Department of Chemistry, Tulane University, New Orleans, Louisiana 70118, United States
| | - Alexander L Burin
- Department of Chemistry, Tulane University, New Orleans, Louisiana 70118, United States
| | - Igor V Rubtsov
- Department of Chemistry, Tulane University, New Orleans, Louisiana 70118, United States
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2
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Nawagamuwage SU, Qasim LN, Zhou X, Leong TX, Parshin IV, Jayawickramarajah J, Burin AL, Rubtsov IV. Competition of Several Energy-Transport Initiation Mechanisms Defines the Ballistic Transport Speed. J Phys Chem B 2021; 125:7546-7555. [PMID: 34185993 PMCID: PMC8287563 DOI: 10.1021/acs.jpcb.1c03986] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
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The ballistic regime
of vibrational energy transport in oligomeric
molecular chains occurs with a constant, often high, transport speed
and high efficiency. Such a transport regime can be initiated by exciting
a chain end group with a mid-infrared (IR) photon. To better understand
the wavepacket formation process, two chemically identical end groups,
azido groups with normal, 14N3-, and isotopically
substituted, 15N3-, nitrogen atoms, were tested
for wavepacket initiation in compounds with alkyl chains of n = 5, 10, and 15 methylene units terminated with a carboxylic
acid (-a) group, denoted as 14N3Cn-a and 15N3Cn-a. The transport
was initiated by exciting the azido moiety stretching mode, the νN≡N tag, at 2100 cm–1 (14N3Cn-a) or 2031 cm–1 (15N3Cn-a). Opposite to the
expectation, the ballistic transport speed was found to decrease upon 14N3 → 15N3 isotope
editing. Three mechanisms of the transport initiation of a vibrational
wavepacket are described and analyzed. The first mechanism involves
the direct formation of a wavepacket via excitation with IR photons
of several strong Fermi resonances of the tag mode with the νN=N + νN–C combination state
while each of the combination state components is mixed with delocalized
chain states. The second mechanism relies on the vibrational relaxation
of an end-group-localized tag into a mostly localized end-group state
that is strongly coupled to multiple delocalized states of a chain
band. Harmonic mixing of νN=N of the azido
group with CH2 wagging states of the chain permits a wavepacket
formation within a portion of the wagging band, suggesting a fast
transport speed. The third mechanism involves the vibrational relaxation
of an end-group-localized mode into chain states. Two such pathways
were found for the νN≡N initiation: The νN=N mode relaxes efficiently into the twisting band
states and low-frequency acoustic modes, and the νN–C mode relaxes into the rocking band states and low-frequency acoustic
modes. The contributions of the three initiation mechanisms in the
ballistic energy transport initiated by νN≡N tag are quantitatively evaluated and related to the experiment.
We conclude that the third mechanism dominates the transport in alkane
chains of 5–15 methylene units initiated with the νN≡N tag and the wavepacket generated predominantly at
the CH2 twisting band. The isotope effect of the transport
speed is attributed to a larger contribution of the faster wavepackets
for 14N3Cn-a or to the different
breadth of the wavepacket within the twisting band. The study offers
a systematic description of different transport initiation mechanisms
and discusses the requirements and features of each mechanism. Such
analysis will be useful for designing novel materials for energy management.
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Affiliation(s)
| | - Layla N Qasim
- Department of Chemistry, Tulane University, New Orleans, Louisiana 70118, United States
| | - Xiao Zhou
- Department of Chemistry, Tulane University, New Orleans, Louisiana 70118, United States
| | - Tammy X Leong
- Department of Chemistry, Tulane University, New Orleans, Louisiana 70118, United States
| | - Igor V Parshin
- Department of Chemistry, Tulane University, New Orleans, Louisiana 70118, United States
| | | | - Alexander L Burin
- Department of Chemistry, Tulane University, New Orleans, Louisiana 70118, United States
| | - Igor V Rubtsov
- Department of Chemistry, Tulane University, New Orleans, Louisiana 70118, United States
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3
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Leong TX, Qasim LN, Mackin RT, Du Y, Pascal RA, Rubtsov IV. Unidirectional coherent energy transport via conjugated oligo(p-phenylene) chains. J Chem Phys 2021; 154:134304. [PMID: 33832250 DOI: 10.1063/5.0046932] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
We discovered a way to funnel high-frequency vibrational quanta rapidly and unidirectionally over large distances using oligo(p-phenylene) chains. After mid-IR photon photoexcitation of a -COOH end group, the excess energy is injected efficiently into the chain, forming vibrational wavepackets that propagate freely along the chain. The transport delivers high-energy vibrational quanta with a range of transport speeds reaching 8.6 km/s, which exceeds the speed of sound in common metals (∼5 km/s) and polymers (∼2 km/s). Efficiencies of energy injection into the chain and transport along the chain are found to be very high and dependent on the extent of conjugation across the structure. By tuning the degree of conjugation via electronic doping of the chain, the transport speed and efficiency can be controlled. The study opens avenues for developing materials with controllable energy transport properties for heat management, schemes with efficient energy delivery to hard-to-reach regions, including transport against thermal gradients, and ways for initiating chemical reactions remotely.
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Affiliation(s)
- Tammy X Leong
- Department of Chemistry, Tulane University, New Orleans, Louisiana 70118, USA
| | - Layla N Qasim
- Department of Chemistry, Tulane University, New Orleans, Louisiana 70118, USA
| | - Robert T Mackin
- Department of Chemistry, Tulane University, New Orleans, Louisiana 70118, USA
| | - Yuchen Du
- Department of Chemistry, Tulane University, New Orleans, Louisiana 70118, USA
| | - Robert A Pascal
- Department of Chemistry, Tulane University, New Orleans, Louisiana 70118, USA
| | - Igor V Rubtsov
- Department of Chemistry, Tulane University, New Orleans, Louisiana 70118, USA
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4
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Rubtsova NI, Lin Z, Mackin RT, Rubtsov IV. How Intramolecular Vibrational Energy Transport Changes with Rigidity and Polarity of the Environment? HIGH ENERGY CHEMISTRY 2020. [DOI: 10.1134/s0018143920060120] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
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5
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Boulatov A, Burin AL. Crucial effect of transverse vibrations on the transport through polymer chains. J Chem Phys 2020; 153:134102. [PMID: 33032425 DOI: 10.1063/5.0018591] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
The low temperature transport of electron, or vibrational or electronic exciton toward polymer chains, turns out to be dramatically sensitive to its interaction with transverse acoustic vibrations. We show that this interaction leads to a substantial polaron effect and decoherence, which are generally stronger than those associated with longitudinal vibrations. For site-dependent interactions, transverse phonons form subohmic bath leading to the quantum phase transition accompanied by full suppression of the transport at zero temperature and fast decoherence characterized by temperature dependent rate k2 ∝ T3/4 at low temperature, while k2 ∝ T2 for site-independent interactions. The latter dependence was used to interpret recent measurements of temperature dependent vibrational energy transport in polyethylene glycol oligomers.
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Affiliation(s)
- Alexei Boulatov
- National Research University Higher School of Economics, 11 Pokrovsky Blvd., Moscow 101000, Russia
| | - Alexander L Burin
- Department of Chemistry, Tulane University, New Orleans, Louisiana 70118, USA
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6
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Mackin RT, Leong TX, Rubtsova NI, Burin AL, Rubtsov IV. Low-Temperature Vibrational Energy Transport via PEG Chains. J Phys Chem Lett 2020; 11:4578-4583. [PMID: 32437615 DOI: 10.1021/acs.jpclett.0c01273] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
We used relaxation-assisted two-dimensional infrared spectroscopy to study the temperature dependence (10-295 K) of end-to-end energy transport across end-decorated PEG oligomers of various chain lengths. The excess energy was introduced by exciting the azido end-group stretching mode at 2100 cm-1 (tag); the transport was recorded by observing the asymmetric C═O stretching mode of the succinimide ester end group at 1740 cm-1. The overall transport involves diffusive steps at the end groups and a ballistic step through the PEG chain. We found that at lower temperatures the through-chain energy transport became faster, while the end-group diffusive transport time and the tag lifetime increase. The modeling of the transport using a quantum Liouville equation linked the observations to the reduction of decoherence rate and an increase of the mean-free-path for the vibrational wavepacket. The energy transport at the end groups slowed down at low temperatures due to the decreased number and efficiency of the anharmonic energy redistribution pathways.
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Affiliation(s)
- Robert T Mackin
- Department of Chemistry, Tulane University, New Orleans, Louisiana 70118, United States
| | - Tammy X Leong
- Department of Chemistry, Tulane University, New Orleans, Louisiana 70118, United States
| | - Natalia I Rubtsova
- Department of Chemistry, Tulane University, New Orleans, Louisiana 70118, United States
| | - Alexander L Burin
- Department of Chemistry, Tulane University, New Orleans, Louisiana 70118, United States
| | - Igor V Rubtsov
- Department of Chemistry, Tulane University, New Orleans, Louisiana 70118, United States
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7
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Zimbovskaya NA, Nitzan A. Energy, Work, Entropy, and Heat Balance in Marcus Molecular Junctions. J Phys Chem B 2020; 124:2632-2642. [PMID: 32163712 DOI: 10.1021/acs.jpcb.0c00059] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
We present a consistent theory of energy balance and conversion in a single-molecule junction with strong interactions between electrons on the molecular linker (dot) and phonons in the nuclear environment where the Marcus-type electron hopping processes predominate in the electron transport. It is shown that the environmental reorganization and relaxation that accompany electron hopping energy exchange between the electrodes and the nuclear (molecular and solvent) environment may bring a moderate local cooling of the latter in biased systems. The effect of a periodically driven dot level on the heat transport and power generated in the system is analyzed, and energy conservation is demonstrated both within and beyond the quasistatic regime. Finally, a simple model of atomic scale engine based on a Marcus single-molecule junction with a driven electron level is suggested and discussed.
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Affiliation(s)
- Natalya A Zimbovskaya
- Department of Physics and Electronics, University of Puerto Rico-Humacao, CUH Station, Humacao, Puerto Rico 00791, United States
| | - Abraham Nitzan
- Department of Chemistry, University of Pennsylvania, Philadelphia, Pennsylvania 19104, United States.,School of Chemistry, Tel Aviv University, Tel Aviv 6997801, Israel
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8
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Topology, landscapes, and biomolecular energy transport. Nat Commun 2019; 10:4662. [PMID: 31604949 PMCID: PMC6789131 DOI: 10.1038/s41467-019-12700-w] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2019] [Accepted: 09/12/2019] [Indexed: 12/20/2022] Open
Abstract
While ubiquitous, energy redistribution remains a poorly understood facet of the nonequilibrium thermodynamics of biomolecules. At the molecular level, finite-size effects, pronounced nonlinearities, and ballistic processes produce behavior that diverges from the macroscale. Here, we show that transient thermal transport reflects macromolecular energy landscape architecture through the topological characteristics of molecular contacts and the nonlinear processes that mediate dynamics. While the former determines transport pathways via pairwise interactions, the latter reflects frustration within the landscape for local conformational rearrangements. Unlike transport through small-molecule systems, such as alkanes, nonlinearity dominates over coherent processes at even quite short time- and length-scales. Our exhaustive all-atom simulations and novel local-in-time and space analysis, applicable to both theory and experiment, permit dissection of energy migration in biomolecules. The approach demonstrates that vibrational energy transport can probe otherwise inaccessible aspects of macromolecular dynamics and interactions that underly biological function. Understanding vibrational energy transfer in macromolecules has been challenging to both theory and experiment. Here the authors use non-equilibrium molecular dynamics to reveal the relationship between heat transport in a model peptide, emergent nonlinearity, and the underlying free energy landscape.
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9
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Liu M, Kawauchi T, Iyoda T, Piotrowiak P. Vibrational Cooling in Oligomeric Viologens of Different Sizes and Topologies. J Phys Chem B 2019; 123:1847-1854. [PMID: 30724560 DOI: 10.1021/acs.jpcb.8b12165] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Vibrational cooling was investigated in a set of homologous dimers and trimers with methyl viologen repeat units (MV2+). The rapid, <500 fs decay of the D1 excited state of monoreduced viologen (MV+•) via a conical intersection allows the preparation of a vibrationally hot D0 ground state with a large excess energy of 1.7 eV, which is equivalent to the initial effective temperature of ∼800 K. Pump-probe spectroscopy was used to monitor the disappearance of the characteristic D0 → D1 hot absorption band, which appears at longer wavelengths than the steady-state spectrum of "cold" MV+• in equilibrium with the solvent. It is assumed that the vibrational excitation of the ground is initially confined to the same monoreduced viologen repeat unit, which was optically excited to the localized electronic D1 state, although some degree of redistribution may occur already in the excited state. The observed cooling rates depend on the size and topology of the oligomer, with the linear trimer exhibiting significantly faster thermalization than the branched one. The experimental results were corroborated by molecular dynamics simulations carried out in the harmonic approximation. The dynamics of the thermal equilibration in these systems appears to be consistent with primarily ballistic initial propagation of the vibrational excess energy over distances as large as ∼4 nm and suggests the presence of interference between the equivalent pathways in the branched trimer.
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Affiliation(s)
- Mengdi Liu
- Department of Chemistry , Rutgers University-Newark , 73 Warren Street , Newark , New Jersey 07102 , United States
| | - Takehiro Kawauchi
- Department of Materials Chemistry, Faculty of Science and Technology , Ryukoku University , 1-5 Yokotani , Oe-cho, Seta, Otsu , Shiga 520-2194 , Japan
| | - Tomokazu Iyoda
- Harris Science Research Institute , Doshisha University , 1-3 Tatara Miyakodani , Kyotanabe , Kyoto 610-0394 , Japan
| | - Piotr Piotrowiak
- Department of Chemistry , Rutgers University-Newark , 73 Warren Street , Newark , New Jersey 07102 , United States
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10
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Li J, Zhang Y, Zheng J. Intermolecular energy flows between surface molecules on metal nanoparticles. Phys Chem Chem Phys 2019; 21:4240-4245. [PMID: 30747170 DOI: 10.1039/c8cp05932b] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Three model systems are designed to investigate energy transport between molecules on metal nanoparticle surfaces. Energy is rapidly transferred from one carbon monoxide (CO) molecule to another CO molecule or an organic molecule on adjacent surface sites of 2 nm Pt particles within a few picoseconds. On the contrary, energy flow from a surface organic molecule to an adjacent CO molecule is significantly slower and, in fact, within experimental sensitivity and uncertainty the transfer is not observed. The energy transport on particle surfaces (about 2 km s-1) is almost ten times faster than inside a molecule (200 m s-1). The seemingly perplexing observations can be well explained by the combination of electron/vibration and vibration/vibration coupling mechanisms, which mediate molecular energy dynamics on metal nanoparticle surfaces: the strong electron/vibration coupling rapidly converts CO vibrational energy into heat that can be immediately sensed by nearby molecules; but the vibration/vibration coupling dissipates the vibrational excitation in the organic molecule as low-frequency intramolecular vibrations that may or may not couple to surface electronic motions.
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Affiliation(s)
- Jiebo Li
- Beijing Advanced Innovation Center for Biomedical Engineering, School of Biological Science and Medical Engineering, Beihang University, Beijing, 100083, China
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11
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Rubtsov IV, Burin AL. Ballistic and diffusive vibrational energy transport in molecules. J Chem Phys 2019; 150:020901. [PMID: 30646721 DOI: 10.1063/1.5055670] [Citation(s) in RCA: 32] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023] Open
Abstract
Energy transport in molecules is essential for many areas of science and technology. Strong covalent bonds of a molecular backbone can facilitate the involvement of the molecule's high-frequency modes in energy transport, which, under certain conditions, makes the transport fast and efficient. We discuss such conditions and describe various transport regimes in molecules, including ballistic, diffusive, directed diffusion, and intermediate regime cases, in light of recently developed experimental and theoretical approaches.
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Affiliation(s)
- Igor V Rubtsov
- Department of Chemistry, Tulane University, New Orleans, Louisiana 70118, USA
| | - Alexander L Burin
- Department of Chemistry, Tulane University, New Orleans, Louisiana 70118, USA
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12
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Varner C, Zhou X, Saxman ZK, Leger JD, Jayawickramarajah J, Rubtsov IV. Azido alkanes as convenient reporters for mobility within lipid membranes. Chem Phys 2018. [DOI: 10.1016/j.chemphys.2018.05.020] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
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13
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Chen R, Craven GT, Nitzan A. Electron-transfer-induced and phononic heat transport in molecular environments. J Chem Phys 2017; 147:124101. [DOI: 10.1063/1.4990410] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- Renai Chen
- Department of Chemistry, University of Pennsylvania, Philadelphia, Pennsylvania 19104,
USA
| | - Galen T. Craven
- Department of Chemistry, University of Pennsylvania, Philadelphia, Pennsylvania 19104,
USA
| | - Abraham Nitzan
- Department of Chemistry, University of Pennsylvania, Philadelphia, Pennsylvania 19104,
USA
- School of Chemistry, Tel Aviv University, Tel Aviv 69978, Israel
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14
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Craven GT, Nitzan A. Electron transfer at thermally heterogeneous molecule-metal interfaces. J Chem Phys 2017. [DOI: 10.1063/1.4971293] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- Galen T. Craven
- Department of Chemistry, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA
| | - Abraham Nitzan
- Department of Chemistry, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA
- School of Chemistry, Tel Aviv University, Tel Aviv 69978, Israel
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15
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Ostrander JS, Knepper R, Tappan AS, Kay JJ, Zanni MT, Farrow DA. Energy Transfer Between Coherently Delocalized States in Thin Films of the Explosive Pentaerythritol Tetranitrate (PETN) Revealed by Two-Dimensional Infrared Spectroscopy. J Phys Chem B 2017; 121:1352-1361. [DOI: 10.1021/acs.jpcb.6b09879] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Joshua S. Ostrander
- Department
of Chemistry, University of Wisconsin-Madison, Madison, Wisconsin 53706, United States
| | - Robert Knepper
- Sandia National Laboratories, Albuquerque, New Mexico 87185, United States
| | | | - Jeffrey J. Kay
- Sandia National Laboratories, Livermore, California 94551, United States
| | - Martin T. Zanni
- Department
of Chemistry, University of Wisconsin-Madison, Madison, Wisconsin 53706, United States
| | - Darcie A. Farrow
- Sandia National Laboratories, Albuquerque, New Mexico 87185, United States
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16
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Leger JD, Varner C, Rubtsov IV. Multi-mode heterodyned 5th-order infrared spectroscopy. J Chem Phys 2016; 145:154201. [DOI: 10.1063/1.4963815] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- Joel D. Leger
- Department of Chemistry, Tulane University, New Orleans, Louisiana 70118, USA
| | - Clyde Varner
- Department of Chemistry, Tulane University, New Orleans, Louisiana 70118, USA
| | - Igor V. Rubtsov
- Department of Chemistry, Tulane University, New Orleans, Louisiana 70118, USA
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17
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Abstract
Charge transfer is a fundamental process that underlies a multitude of phenomena in chemistry and biology. Recent advances in observing and manipulating charge and heat transport at the nanoscale, and recently developed techniques for monitoring temperature at high temporal and spatial resolution, imply the need for considering electron transfer across thermal gradients. Here, a theory is developed for the rate of electron transfer and the associated heat transport between donor-acceptor pairs located at sites of different temperatures. To this end, through application of a generalized multidimensional transition state theory, the traditional Arrhenius picture of activation energy as a single point on a free energy surface is replaced with a bithermal property that is derived from statistical weighting over all configurations where the reactant and product states are equienergetic. The flow of energy associated with the electron transfer process is also examined, leading to relations between the rate of heat exchange among the donor and acceptor sites as functions of the temperature difference and the electronic driving bias. In particular, we find that an open electron transfer channel contributes to enhanced heat transport between sites even when they are in electronic equilibrium. The presented results provide a unified theory for charge transport and the associated heat conduction between sites at different temperatures.
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Affiliation(s)
- Galen T Craven
- Department of Chemistry, University of Pennsylvania, Philadelphia, PA 19104
| | - Abraham Nitzan
- Department of Chemistry, University of Pennsylvania, Philadelphia, PA 19104; School of Chemistry, Tel Aviv University, Tel Aviv 69978, Israel
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18
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Abstract
We review studies of vibrational energy transfer in a molecular junction geometry, consisting of a molecule bridging two heat reservoirs, solids or large chemical compounds. This setup is of interest for applications in molecular electronics, thermoelectrics, and nanophononics, and for addressing basic questions in the theory of classical and quantum transport. Calculations show that system size, disorder, structure, dimensionality, internal anharmonicities, contact interaction, and quantum coherent effects are factors that combine to determine the predominant mechanism (ballistic/diffusive), effectiveness (poor/good), and functionality (linear/nonlinear) of thermal conduction at the nanoscale. We review recent experiments and relevant calculations of quantum heat transfer in molecular junctions. We recount the Landauer approach, appropriate for the study of elastic (harmonic) phononic transport, and outline techniques that incorporate molecular anharmonicities. Theoretical methods are described along with examples illustrating the challenge of reaching control over vibrational heat conduction in molecules.
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Affiliation(s)
- Dvira Segal
- Department of Chemistry, University of Toronto, Toronto, Ontario M5S 3H6, Canada;,
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19
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Rubtsova NI, Qasim LN, Kurnosov AA, Burin AL, Rubtsov IV. Ballistic Energy Transport in Oligomers. Acc Chem Res 2015; 48:2547-55. [PMID: 26305731 DOI: 10.1021/acs.accounts.5b00299] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The development of nanocomposite materials with desired heat management properties, including nanowires, layered semiconductor structures, and self-assembled monolayer (SAM) junctions, attracts broad interest. Such materials often involve polymeric/oligomeric components and can feature high or low thermal conductivity, depending on their design. For example, in SAM junctions made of alkane chains sandwiched between metal layers, the thermal conductivity can be very low, whereas the fibers of ordered polyethylene chains feature high thermal conductivity, exceeding that of many pure metals. The thermal conductivity of nanostructured materials is determined by the energy transport between and within each component of the material, which all need to be understood for optimizing the properties. For example, in the SAM junctions, the energy transport across the metal-chain interface as well as the transport through the chains both determine the overall heat conductivity, however, to separate these contributions is difficult. Recently developed relaxation-assisted two-dimensional infrared (RA 2DIR) spectroscopy is capable of studying energy transport in individual molecules in the time domain. The transport in a molecule is initiated by exciting an IR-active group (a tag); the method records the influence of the excess energy on another mode in the molecule (a reporter). The energy transport time can be measured for different reporters, and the transport speed through the molecule is evaluated. Various molecules were interrogated by RA 2DIR: in molecules without repeating units (disordered), the transport mechanism was expected and found to be diffusive. The transport via an oligomer backbone can potentially be ballistic, as the chain offers delocalized vibrational states. Indeed, the transport regime via three tested types of oligomers, alkanes, polyethyleneglycols, and perfluoroalkanes was found to be ballistic, whereas the transport within the end groups was diffusive. Interestingly, the transport speeds via these chains were different. Moreover, the transport speed was found to be dependent on the vibrational mode initiating the transport. For the difference in the transport speeds to be explained, the chain bands involved in the wavepacket formation were analyzed, and specific optical bands of the chain were identified as the energy transporters. For example, the transport initiated in alkanes by the stretching mode of the azido end group (2100 cm(-1)) occurs predominantly via the CH2 twisting and wagging chain bands, but the transport initiated by the C=O stretching modes of the carboxylic acid or succinimide ester end groups occurs via C-C stretching and CH2 rocking bands of the alkane chain. Direct formation of the wavepacket within the CH2 twisting and wagging chain bands occurs when the transport is initiated by the N═N stretching mode (1270 cm-1) of the azido end-group. The transport via optical chain bands in oligomers involves rather large vibrational quanta (700-1400 cm(-1)), resulting in efficient energy delivery to substantial distances. Achieved quantitative description of various energy transport steps in oligomers, including the specific contributions of different chain bands, can result in a better understanding of the transport steps in nanocomposite materials, including SAM junctions, and lead towards designing systems for molecular electronics with a controllable energy transport speed.
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Affiliation(s)
- Natalia I. Rubtsova
- Department of Chemistry, Tulane University, New Orleans, Louisiana 70118, United States
| | - Layla N. Qasim
- Department of Chemistry, Tulane University, New Orleans, Louisiana 70118, United States
| | - Arkady A. Kurnosov
- Department of Chemistry, Tulane University, New Orleans, Louisiana 70118, United States
| | - Alexander L. Burin
- Department of Chemistry, Tulane University, New Orleans, Louisiana 70118, United States
| | - Igor V. Rubtsov
- Department of Chemistry, Tulane University, New Orleans, Louisiana 70118, United States
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Yue Y, Qasim LN, Kurnosov AA, Rubtsova NI, Mackin RT, Zhang H, Zhang B, Zhou X, Jayawickramarajah J, Burin AL, Rubtsov IV. Band-Selective Ballistic Energy Transport in Alkane Oligomers: Toward Controlling the Transport Speed. J Phys Chem B 2015; 119:6448-56. [DOI: 10.1021/acs.jpcb.5b03658] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Yuankai Yue
- Department of Chemistry, Tulane University, New Orleans, Louisiana 70118, United States
| | - Layla N. Qasim
- Department of Chemistry, Tulane University, New Orleans, Louisiana 70118, United States
| | - Arkady A. Kurnosov
- Department of Chemistry, Tulane University, New Orleans, Louisiana 70118, United States
| | - Natalia I. Rubtsova
- Department of Chemistry, Tulane University, New Orleans, Louisiana 70118, United States
| | - Robert T. Mackin
- Department of Chemistry, Tulane University, New Orleans, Louisiana 70118, United States
| | - Hong Zhang
- Department of Chemistry, Tulane University, New Orleans, Louisiana 70118, United States
| | - Boyu Zhang
- Department of Chemistry, Tulane University, New Orleans, Louisiana 70118, United States
| | - Xiao Zhou
- Department of Chemistry, Tulane University, New Orleans, Louisiana 70118, United States
| | | | - Alexander L. Burin
- Department of Chemistry, Tulane University, New Orleans, Louisiana 70118, United States
| | - Igor V. Rubtsov
- Department of Chemistry, Tulane University, New Orleans, Louisiana 70118, United States
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