Surface specific heats of metal nanocrystals at low temperatures

Lei, Hongwei; Li, Jun; Luo, Jiangshan

doi:10.1039/c5nr00056d

Cited by 9 publications

(8 citation statements)

References 24 publications

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“…As a matter of fact, the excess has more than doubled (3% to 7%) when the mean size is reduced from sample D to B. The excess specific heat has been already examined when going from bulk to nanocrystalline copper, either theoretically in clusters26 or experimentally6. In this last and very recent work, the excess has been shown to reach a maximum of 5% near 50 K, in good agreement with the present observation.…”

Section: Discussionsupporting

confidence: 89%

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Vibrational density of states and thermodynamics at the nanoscale: the 3D-2D transition in gold nanostructures

Carles

Benzo

Pécassou

et al. 2016

Sci Rep

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Surface enhanced Raman scattering (SERS) is generally and widely used to enhance the vibrational fingerprint of molecules located at the vicinity of noble metal nanoparticles. In this work, SERS is originally used to enhance the own vibrational density of states (VDOS) of nude and isolated gold nanoparticles. This offers the opportunity of analyzing finite size effects on the lattice dynamics which remains unattainable with conventional techniques based on neutron or x-ray inelastic scattering. By reducing the size down to few nanometers, the role of surface atoms versus volume atoms become dominant, and the “text-book” 3D-2D transition on the dynamical behavior is experimentally emphasized. “Anomalies” that have been predicted by a large panel of simulations at the atomic scale, are really observed, like the enhancement of the VDOS at low frequencies or the occurrence of localized modes at frequencies beyond the cut-off in bulk. Consequences on the thermodynamic properties at the nanoscale, like the reduction of the Debye temperature or the excess of the specific heat, have been evaluated. Finally the high sensitivity of reminiscent bulk-like phonons on the arrangements at the atomic scale is used to access the morphology and internal disorder of the nanoparticles.

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Section: Discussionsupporting

confidence: 89%

“…As a consequence, size reduction generates “anomalies” – i.e. departures from the bulk behavior - on elastic and thermodynamic properties like lattice specific heat, thermal expansion, Debye and melting temperature, vibrational entropy…123456. It also modifies the thermal and electrical conductivity because phonons mediate transport properties789.…”

mentioning

confidence: 99%

Vibrational density of states and thermodynamics at the nanoscale: the 3D-2D transition in gold nanostructures

Carles

Benzo

Pécassou

et al. 2016

Sci Rep

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“…We note that a T 3 implies a 3D lattice contribution to the low temperature heat capacity of the Ni(TCNQ − D 4 ) 2 sample which consists of nanograins. However, there have been reports of other nanostructured materials exhibiting such a temperature dependence, though the measured Debye temperatures did not correspond to bulk values [52,53]. This suggests that, in Ni(TCNQ − D 4 ) 2 , there is strong enough coupling between the nanograins to allow long wavelength lattice vibrations to contribute to the heat capacity.…”

Section: Heat Capacitymentioning

confidence: 78%

Separating the ferromagnetic and glassy behavior within the metal-organic magnetNi(TCNQ)2

et al. 2015

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Publisher's copyright statement:Reprinted with permission from the American Physical Society: Physical Review B 92, 184431 c 2015 by the American Physical Society. Readers may view, browse, and/or download material for temporary copying purposes only, provided these uses are for noncommercial personal purposes. Except as provided by law, this material may not be further reproduced, distributed, transmitted, modied, adapted, performed, displayed, published, or sold in whole or part, without prior written permission from the American Physical Society.Additional information: Use policyThe full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-prot purposes provided that:• a full bibliographic reference is made to the original source • a link is made to the metadata record in DRO • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders.Please consult the full DRO policy for further details. An in-depth study of the metal-organic magnet Ni(TCNQ) 2 was conducted where the deuterated form was synthesised both to attempt to alter the magnetic properties of the material and to be advantageous in techniques such as neutron scattering and muon spectroscopy. Deuteration saw a 3 K increase in T C with magnetization and heat capacity measurements demonstrating a spin wave contribution at low temperatures confirming the 3D nature of the ferromagnetic state shown by Ni(TCNQ − D 4 ) 2 . AC susceptibility results suggest there is a glassy component associated with the magnetically ordered state, though muon spectroscopy measurements did not support the presence of a spin glass state. Instead muon spectroscopy at zero magnetic field indicated the presence of two magnetic transitions, one at 20 K and another below 6 K; the latter is likely due to the system entering a quasistatic regime, similar to what one might expect of a superspin or cluster glass. Neutron diffraction measurements further supported this by revealing very weak magnetic Bragg peaks suggesting that the magnetism may have a short coherence length and be confined to small grains or clusters. The separation of the ferromagnetic and glassy magnetic components of the material's properties suggest that this system may show promise as a metal-organic magnet which is easily modified to change its magnetic properties, providing larger grain sizes can be synthesized.

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“…As a sustainable clean energy, solar energy is more and more widely used due to its abundant natural resources and broad spectrum [6][7][8]. The photothermal energy obtained from sunlight is now utilized for steam generation, enabling renewable desalination and purification, which provides a promising avenue for the current water crisis [9][10][11][12][13][14][15].…”

Section: Introductionmentioning

confidence: 99%

Copper nanoparticles with near-unity, omnidirectional, and broadband optical absorption for highly efficient solar steam generation

et al. 2018

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Solar steam generation provides a renewable and environmentally friendly approach to solve the water shortage issue. The pursuit of efficient, stable, and cheap photothermal agents is thus of great significance. In this work, Cu nanoparticles (NPs) fabricated simply by a substitution reaction, exhibit a near-unity (∼97.7%) light absorption, covering a broad incident angle and wavelength range (200–1300 nm). Thereby, a high photothermal conversion efficiency of 93% is achieved. The excellent photothermal performance offers a unique opportunity for the development of solar steam generation. By coating the Cu NPs on a cellulose membrane, a solar steam generation efficiency up to 73% is acquired at a low irradiation power density of 2 kW m−2 (1 kW m−2 = 1 sun). Moreover, the Cu NPs are recyclable with the high stability being resistant to heat, photoirradiation and corrosion of brine.

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Surface specific heats of metal nanocrystals at low temperatures

Cited by 9 publications

References 24 publications

Vibrational density of states and thermodynamics at the nanoscale: the 3D-2D transition in gold nanostructures

Vibrational density of states and thermodynamics at the nanoscale: the 3D-2D transition in gold nanostructures

Separating the ferromagnetic and glassy behavior within the metal-organic magnetNi(TCNQ)2

Copper nanoparticles with near-unity, omnidirectional, and broadband optical absorption for highly efficient solar steam generation

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