Browsing by Author "Korepanov, Vitaly I."

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Carbon structure in nanodiamonds elucidated from Raman spectroscopy
(2017-09-01)
Korepanov, Vitaly I.
;
Hamaguchi, Hiro-o
;
Osawa, Eiji
;
Ermolenkov, Vladimir
;
Lednev, Igor K.
Despite their name, nanodiamonds (ND) are comprised of a complex interplay of different carbon phases. The diamond core is surrounded by the shell consisting mostly of disordered sp(3) carbon and graphene-like carbon (GLC). The complex structure makes the characterization of nanodiamonds (ND) a difficult challenge. Recent development of many varieties of NDs for different applications demands quick and reliable characterization of the content of various carbon fragments, as well as the estimation of the diamond core size. In this work, we apply Raman spectroscopy to study the structure of nanodiamonds from different origins, including those produced by detonation (DND), high pressure high temperature synthesis (HPHT), and pulsed laser irradiation (LND). The relative content of GLC, disordered and surface carbon can be easily determined from Raman spectra. In particular, we show how the content of different structure fragments is changed upon de-agglutination, surface oxidation and ion irradiation. We also compare the different ND production methods in terms of the structural uniformity of the nanoparticles. Raman spectroscopy provides unique quantitative tool for ND characterization; we believe that the present data will be useful for understanding the structure of diamond nanoparticles, and will provide the background for obtaining the NDs with desired properties. (C) 2017 Elsevier Ltd. All rights reserved.
Communication: Three-dimensional model for phonon confinement in small particles: Quantitative bandshape analysis of size-dependent Raman spectra of nanodiamonds
(2014-01-28)
Korepanov, Vitaly I.
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Witek, Henryk
;
Okajima, Hajime
;
Osawa, Eiji
;
Hamaguchi, Hiro-O
Raman spectroscopy of nano-scale materials is facing a challenge of developing a physically sound quantitative approach for the phonon confinement effect, which profoundly affects the phonon Raman band shapes of small particles. We have developed a new approach based on 3-dimensional phonon dispersion functions. It analyzes the Raman band shapes quantitatively in terms of the particle size distributions. To test the model, we have successfully obtained good fits of the observed phonon Raman spectra of diamond nanoparticles in the size range from 1 to 100 nm. (C) 2014 AIP Publishing LLC.
Quantum-chemical perspective of nanoscale Raman spectroscopy with the three-dimensional phonon confinement model
(2017-06-01)
Korepanov, Vitaly I.
;
Hamaguchi, Hiro-o
;
應用化學系
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應用化學系分子科學碩博班
;
Department of Applied Chemistry
Raman spectroscopy of crystalline/molecular systems is well grounded with quantum-chemical calculations and group theory, making it a unique tool for material characterization. For the intermediate' case of nanometer-scale systems, however, the application of Raman spectroscopy is limited by the lack of such theoretical bases. Here, we couple a scaled quantum-chemical calculation with the phonon confinement model to construct a universal and physically consistent basis for nanoscale Raman spectroscopy. Unlike the commonly assumed one-dimensional approximation of phonon dispersion, we take into account the confinement along all the three dimensions of the k-space. We apply it to diamond nanoparticles of sub-50-nm size, a system with pronounced anisotropy of dispersion for which consideration of three-dimensional dispersion is a requisite. The model excellently reproduces size-sensitive Raman spectral features, including the peak position, bandwidth, and asymmetry of the sp(3) C-C stretch Raman line. This fundamental approach can be easily generalized to contribute the future development of quantitative nanoscale Raman spectroscopy. Copyright (c) 2017 John Wiley & Sons, Ltd.
Reply to the comment by Osipov et al. to "Carbon structure in nanodiamonds elucidated from Raman Spectroscopy"
(2018-08-01)
Korepanov, Vitaly I.
;
Osawa, Eiji
;
Lednev, Igor K.
;
Hamaguchi, Hiro-o
;
交大名義發表
Osipov and co-authors [1] commented on our recent paper "Carbon structure in nanodiamonds elucidated from Raman Spectroscopy" [2]. We wish to reply to their comments to further clarify the issues. (C) 2018 Elsevier Ltd. All rights reserved.