Low wavenumber Raman scattering of cobalt nanoparticles self‐organized in 3D superlattices far from surface plasmon resonance

Meziane, L.; Courty, Alexa; Colomban, Philippe; Lisiecki, Isabelle

doi:10.1002/jrs.4782

Cited by 14 publications

(17 citation statements)

References 43 publications

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“…Light in the UV range (<400 nm), coincident with the expected surface plasmon resonance of metallic cobalt nanoparticles, was observed to promote the reaction in a noticeable way. 33 Therefore, it can be deduced that photo-generation of charges (electron-hole pairs) on Co nanoparticles might participate in the CO2 hydrogenation reaction. A recent study on the use of carbon-coated iron nanoparticles in a similar process suggested that hot electrons generated by absorption of UV light were responsible for activating CO2.…”

Section: Effect Of Light On the Catalytic Performancementioning

confidence: 99%

Sunlight-assisted hydrogenation of CO 2 into ethanol and C2+ hydrocarbons by sodium-promoted Co@C nanocomposites

Liu

Puga

Cored

et al. 2018

Applied Catalysis B: Environmental

114

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The hydrogenation of CO2 into hydrocarbons promoted by the action of sunlight has been studied on Co nanoparticles covered by thin carbon layers. In particular, nearly 100% selectivity to hydrocarbons is obtained with increased selectivity's towards C2+ hydrocarbons and alcohols (mainly ethanol) when using nanostructured materials comprising metallic cobalt nanoparticles, carbon layers, and sodium as promoter (Na-Co@C). In the contrary, larger amount of CH4 and lower selectivity to C2+ hydrocarbons and alcohols were obtained in the conventional thermal catalytic process. When using Co@C nanoparticles in the absence of Na or bare Co3O4 as catalyst, methane is essentially the main product (selectivity >96%). Control experiments in the presence of methanol as a hole scavenger suggest the role of light in generating charges by photon absorption via surface plasmon resonance as promoting factor. The reaction mechanism for photoassited CO2 hydrogenation on the Co-based catalysts were investigated by near ambient-pressure X-ray photoelectron (AP-XPS) and in situ Raman spectroscopies, which provided information on the role of light and Na promotor in the modulation of product distribution for CO2 hydrogenation. Spectroscopic studies suggested that surface CO2 dissociation to CO, the stabilization of CO adsorbed on the surface of Na-Co@C catalyst and the easy desorption of reaction products is a key step for photoassisted CO2 hydrogenation to ethanol and C2+ hydrocarbons.

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Section: Effect Of Light On the Catalytic Performancementioning

confidence: 99%

Sunlight-assisted hydrogenation of CO 2 into ethanol and C2+ hydrocarbons by sodium-promoted Co@C nanocomposites

Liu

Puga

Cored

et al. 2018

Applied Catalysis B: Environmental

114

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“…According to Lamb’s theory, − the vibration modes of a free elastic sphere (regular) are described with the azimuthal quantum number . From the selection rules established in refs – only vibration modes related to an even value of are Raman active. The lowest wavenumber has a peak at ∼10 cm –1 , and is assigned to the quadrupolar ( = 2) mode, for the second lowest wavenumber mode at 20 cm –1 , it corresponds to the breathing mode ( = 0) .…”

Section: Resultsmentioning

confidence: 99%

“…From the selection rules established in refs – only vibration modes related to an even value of are Raman active. The lowest wavenumber has a peak at ∼10 cm –1 , and is assigned to the quadrupolar ( = 2) mode, for the second lowest wavenumber mode at 20 cm –1 , it corresponds to the breathing mode ( = 0) . The narrow size distribution and high stability of NCs against oxidation and coalescence, combined with the high luminosity of the spectrometer at the particular wavenumber interval, made possible the simultaneous observation of both breathing and quadrupolar modes whenever the Plasmon absorption of cobalt metal is expected far away from the laser excitation energy .…”

Section: Resultsmentioning

confidence: 99%

“…The lowest wavenumber has a peak at ∼10 cm –1 , and is assigned to the quadrupolar ( = 2) mode, for the second lowest wavenumber mode at 20 cm –1 , it corresponds to the breathing mode ( = 0) . The narrow size distribution and high stability of NCs against oxidation and coalescence, combined with the high luminosity of the spectrometer at the particular wavenumber interval, made possible the simultaneous observation of both breathing and quadrupolar modes whenever the Plasmon absorption of cobalt metal is expected far away from the laser excitation energy . Variation of the quadrupolar and breathing mode wavenumber as a function of the inverse particle diameter shows a linear behavior as expected (Figure b). , The wavenumber of the breathing mode is also in accordance with previous results obtained through femtosecond pump–probe spectroscopy on Co samples prepared with the same route, as well as with previous characterization of 3D assemblies of 7.7 nm Co NCs .…”

Section: Resultsmentioning

confidence: 99%

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Solvent Effects on Cobalt Nanocrystal Synthesis—A Facile Strategy To Control the Size of Co Nanocrystals

et al. 2016

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In this paper, revisiting the chemical reduction approach of Co(AOT) 2 (AOT = bis(2-ethylhexyl) sulfosuccinate) precursor by NaBH 4 , we highlight a novel synthetic strategy based on the change of the solvent to accurately control the size of Co nanocrystals (NCs) from 3.9 to 9.3 nm and their 2D and 3D (supracrystal) ordering. The evolution of the NC size with the solvent is explained by solventmediated ligand−ligand interactions using Hansen solubility parameters. A formula for the nanocrystal size as a function of the solvent is proposed which predicts its diameter within 1 nm. Moreover, and to the best of our knowledge, we show the first example of tunable Co NC size while keeping unchanged the chemistry of ligands (combination and proportion) during the growth step. Due to the possibility we have to replace the AOT ligand by the strong-binding dodecanoic acid, Co NCs are characterized by long-term stability against oxidation and coalescence of the metallic NCs, whatever their size. Low-wavenumber Raman spectra are obtained using a triple notch filtered spectrometer under 514.5 nm excitation. Two modes are clearly observed according to Lamb's model of sphere vibrations whenever the excitation laser line is far from plasmon absorption. They shift linearly with inverse particle diameter from ∼8/17 ± 0.1 cm −1 (9.3 nm) to 12.5/23 ± 0.3 cm −1 (3.9 nm).

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“…Simon and co‐workers report the first observation of low‐wavenumber Raman scattering of cobalt nanoparticles that were self‐organized into 3D superlattices far from surface plasmon resonance. Their results demonstrate that surface plasmon‐phonon resonance coupling is not required to observe Lamb's modes in metal nanoparticles . Sivadasan and Dhara used polarized Raman and photoluminescence studies of a submicron‐sized hexagonal AlGaN crystallite to study their structural and optical properties.…”

Section: Nanomaterialsmentioning

confidence: 99%

Recent advances in linear and non‐linear Raman spectroscopy. Part XI

Nafie

2017

J Raman Spectroscopy

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This review, published annually, provides an overview of advances in the field of Raman spectroscopy as found in papers published in the preceding calendar year in the Journal of Raman Spectroscopy (JRS), as well as in trends over the past decade across journals that have published papers important to the field of Raman spectroscopy. This information is obtained from statistical data on article counts obtained from Clarivate Analytics' Web of Science Core Collection by year and by subfield of Raman spectroscopy. Additional information is gleaned from presentations at the IX International Conference on Advanced Vibrational Spectroscopy (ICAVS‐9) in Victoria, British Columbia, Canada, in June 2017 and those featuring Raman scattering at SCIX 2017 organized by the Federation of Analytical Chemistry and Spectroscopy Societies (FACSS) in Reno, Nevada, USA, in October 2017. Coverage is also provided for topics from the European Conference on Non‐linear Optical Spectroscopy (ECONOS 2017) held in April 2017 in Jena, Germany, and the Ninth Congress on the Application of Raman in Art and Archaeology (RAA 2017) in October 2017 in Evora, Portugal. Finally, papers published in JRS in 2016 are highlighted and arranged by topics at the frontier of Raman spectroscopy. Based on this survey information, it is clear that Raman spectroscopy maintains a rapidly expanding influence across a wide range of novel disciplines and applications that provide sensitive photonic information of matter at the molecular level.

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Low wavenumber Raman scattering of cobalt nanoparticles self‐organized in 3D superlattices far from surface plasmon resonance

Cited by 14 publications

References 43 publications

Sunlight-assisted hydrogenation of CO 2 into ethanol and C2+ hydrocarbons by sodium-promoted Co@C nanocomposites

Sunlight-assisted hydrogenation of CO 2 into ethanol and C2+ hydrocarbons by sodium-promoted Co@C nanocomposites

Solvent Effects on Cobalt Nanocrystal Synthesis—A Facile Strategy To Control the Size of Co Nanocrystals

Recent advances in linear and non‐linear Raman spectroscopy. Part XI

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