Ultrafast dynamics of heat flow across molecules

Wang, Zhaohui; Cahill, David G.; Carter, Jeffrey A.; Koh, Yee Kan; Lagutchev, Alexei; Seong, Nak Hyun; Dlott, Dana D.

doi:10.1016/j.chemphys.2007.12.017

Cited by 54 publications

(116 citation statements)

References 45 publications

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“…Given the recent interest in thermal transport in organicbased nanocomposites [19][20][21][22][23] and heat transport across molecular interfaces [24][25][26][27][28][29][30], systematically studying the thermal conductivity of a series of ALD/MLD-grown hybrid SLs also provides an ideal platform to advance our understanding of phonon scattering at, and heat transfer across, thin molecular interfaces. These high-quality hybrid nanosystems also provide ideal materials to understand the heat transfer mechanisms in organic/inorganic SLs, and the interplay between phonon-boundary scattering and thermal boundary conductance across interfaces of identical materials separated by a well-defined molecular layer.…”

Section: Introductionmentioning

confidence: 99%

Heat-transport mechanisms in molecular building blocks of inorganic/organic hybrid superlattices

et al. 2016

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Nanomaterial interfaces and concomitant thermal resistances are generally considered as atomic-scale planes that scatter the fundamental energy carriers. Given that the nanoscale structural and chemical properties of solid interfaces can strongly influence this thermal boundary conductance, the ballistic and diffusive nature of phonon transport along with the corresponding phonon wavelengths can affect how energy is scattered and transmitted across an interfacial region between two materials. In hybrid composites composed of atomic layer building blocks of inorganic and organic constituents, the varying interaction between the phononic spectrum in the inorganic crystals and vibronic modes in the molecular films can provide a new avenue to manipulate the energy exchange between the fundamental vibrational energy carriers across interfaces. Here, we systematically study the heat transfer mechanisms in hybrid superlattices of atomic-and molecular-layer-grown zinc oxide and hydroquinone with varying thicknesses of the inorganic and organic layers in the superlattices. We demonstrate ballistic energy transfer of phonons in the zinc oxide that is limited by scattering at the zinc oxide/hydroquinone interface for superlattices with a single monolayer of hydroquinone separating the thicker inorganic layers. The concomitant thermal boundary conductance across the zinc oxide interfacial region approaches the maximal thermal boundary conductance of a zinc oxide phonon flux, indicative of the contribution of long wavelength vibrations across the aromatic molecular monolayers in transmitting energy across the interface. This transmission of energy across the molecular interface decreases considerably as the thickness of the organic layers are increased.

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Section: Introductionmentioning

confidence: 99%

Heat-transport mechanisms in molecular building blocks of inorganic/organic hybrid superlattices

et al. 2016

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“…An important driving factor in this growing interest is the development of experimental capabilities that greatly improve on the ability to gauge temperatures (and "effective" temperatures in nonequilibrium systems) with high spatial and thermal resolutions (29-43) and to infer from such measurement the underlying heat transport processes. In particular, vibrational energy transport/ heat conduction in molecular layers and junctions has recently been characterized using different probes (6,19,(44)(45)(46)(47)(48)(49)(50)(51)(52).The interplay between charge and energy (electronic and nuclear) transport (53-60) is of particular interest as it pertains to the performance of energy-conversion devices, such as thermoelectric, photovoltaic, and electromechanical devices. In particular, the thermoelectric response of molecular junctions, mostly focusing on the junction linear response as reflected by its Seebeck coefficient, has been recently observed (61-65) and theoretically analyzed (2,20,64,(66)(67)(68)(69)(70)(71)(72)(73)(74)(75)(76)(77).…”

mentioning

confidence: 99%

mentioning

confidence: 99%

Electron transfer across a thermal gradient

Craven

Nitzan

2016

Proc. Natl. Acad. Sci. U.S.A.

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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. T he study of electronic transport in molecular nanojunctions naturally involves consideration of inelastic transport, where the transporting electron can exchange energy with underlying nuclear motions (1, 2). Such studies have been motivated by the use of inelastic tunneling spectroscopy, and more recently Raman spectroscopy, as diagnostic tools on one hand, and by considerations of junction stability on the other. In parallel, there has been an increasing interest in vibrational heat transport in nanostructures and their interfaces with bulk substrates (3-11) focusing on structure-transport correlations (12-15), moleculesubstrate coupling (16-18), ballistic and diffusive transport processes (11,19), and rectification (20-22). More recently, noise (23-26), nonlinear response (e.g., negative differential heat conductance), and control by external stimuli (27, 28) have been examined. An important driving factor in this growing interest is the development of experimental capabilities that greatly improve on the ability to gauge temperatures (and "effective" temperatures in nonequilibrium systems) with high spatial and thermal resolutions (29-43) and to infer from such measurement the underlying heat transport processes. In particular, vibrational energy transport/ heat conduction in molecular layers and junctions has recently been characterized using different probes (6,19,(44)(45)(46)(47)(48)(49)(50)(51)(52).The interplay between charge and energy (electronic and nuclear) transport (53-60) is of particular interest as it pertains to the performance of energy-conversion devices, such as therm...

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“…Flash-heating experiments to study the time dependence used the arrangement shown in Fig. 106a [153,154]. Flash-heating pulses could heat the metal layer up to and beyond the melting point, which was 1064°C for Au.…”

Section: Figure 100mentioning

confidence: 99%

Nano Engineered Energetic Materials (NEEM)

Dlott¹,

Eden²,

Girolami³

et al. 2011

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The public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection of information. The ARO Nano Engineered Energetic Materials (NEEM) MURI program has been exploring new methodologies for developing energetic material formulations with control of all constituents over a wide range of length scales from 1 nm to 1 mm and larger and employing the latest techniques in molecular self-assembly and supramolecular chemistry for synthesizing and assembling NEEMs. The synthetic efforts have been guided by theoretical calculations and dynamic performance testing methodologies that also operate on all length scales. This final report ABSTRACTThe ARO Nano Engineered Energetic Materials (NEEM) MURI program has been exploring new methodologies for developing energetic material formulations with control of all constituents over a wide range of length scales from 1 nm to 1 mm and larger and employing the latest techniques in molecular self-assembly and supramolecular chemistry for synthesizing and assembling NEEMs. The synthetic efforts have been guided by theoretical calculations and dynamic performance testing methodologies that also operate on all length scales. This final report provides a summary of the accomplishments. In particular, new methods to generate metal nanoclusters were developed that are stabilized against environmental degradation while preserving their high energy content. Rapid expansion supercritical solution processes were developed and applied to synthesize nanosized particulate oxidizers and energetic oxidizer shell/fuel core composites. Surface science and experimental chemistry methods were applied to study the structures and energy releasing reaction pathways of NEEMs. Unique diagnostic capabilities were developed and applied to study the fundamental mechanisms that underlie NEEM dynamic performance. Combustion mechanisms of various NEEMs, including nanothermites and nanoparticulate fuel/liquid oxidizer systems, were experimentally analyzed. The reactive and thermal characteristics of NEEMs were studied using large (billion atoms) multiscale simulations that couple quantum-mechanical calculations to molecular dynamics calculations. In particular, the stability, structure and energetics of metallic nanoparticles with a special focus on the relationships between particle size, shape and excess surface free energy were studied. A unified theory of ignition and combustion of aluminum particles for a wide range of sizes, from nano to meso scales was established. . 12, 777-787 (2010 (b) Papers published in non-peer-reviewed journals or in conference proceedings (N/A for none)18.00 Number of Papers published in peer-reviewed journals:Number of Papers published in non peer-reviewed journals:1. USC group, "Multibillion-atom simulations of nano-mechano-chemistry on petaflops computers," First

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Ultrafast dynamics of heat flow across molecules

Cited by 54 publications

References 45 publications

Heat-transport mechanisms in molecular building blocks of inorganic/organic hybrid superlattices

Heat-transport mechanisms in molecular building blocks of inorganic/organic hybrid superlattices

Electron transfer across a thermal gradient

Nano Engineered Energetic Materials (NEEM)

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