XIV
h
International Conference on Molecular Spectroscopy, Białka Tatrzańska 2017
28
I–10
Strongly 2D-confined phonons and their overtones in colloidal
nanoplatelets
Volodymyr Dzhagan
1,2
, Mykhailo Ya. Valakh
2
, Alexander G. Milekhin
3
,
Silvia Pedetti
4
, Benoit Dubertret
4
, and Dietrich R.T. Zahn
1
1
Semiconductor Physics, Technische Universität Chemnitz, Reichenhainer Str. 70, D-09126
Chemnitz, Germany, e-mail: volodymyr.dzhagan@physik.tu-chemnitz.de
2
V. E. Lashkaryov Institute of Semiconductors Physics, NAS of Ukraine, pr. Nauky 45, 03128 Kyiv,
Ukraine
3
A.V. Rzhanov Institute of Semiconductor Physics, pr. Lavrentieva 13, 630090 Novosibirsk, Russia
4
Laboratoire de Physique et d’Etude des Matériaux, CNRS, ESPCI, 10 rue Vauquelin, 75005 Paris,
France
The high flexibility of chemical routes for tailoring the properties of colloidal nanocrystals
(NCs) and NC-molecule hybrid structures stimulates ever-growing activities on synthesis,
investigation, and application [1]. Recently, 2D colloidal semiconductor nanocrystals, or
nanoplatelets (NPLs), as thin as 1–2 nm, were obtained [2]. Growing CdSe and CdS
subsequently in either side-by-side or stacked manner results in core-crown or core/shell
structures, respectively. Both kinds of hetero-NPLs find efficient applications and are interesting
materials to study the elemental excitations under strong one-directional confinement.
Here, we report on Raman and infrared spectroscopy study of the phonon spectra and
electron-phonon coupling in CdSe/CdS core/shell and core-crown NPLs. The general difference
between two NPL morphologies is the larger number of phonon modes in core/shell NPLs, their
spectral shifts with change of shell thickness or Eexc, as well as resulting overtone spectra,
which are further modified by tuning the laser excitation energy Eexc between in- and off-
resonant conditions. The spectra of the core-crown NPLs resemble more the sum of spectra of
the isolated CdSe and CdS particles and are similar to spherical morphologies studied earlier.
This behaviour is explained by mutual influence of the core and shell in NPLs and formation of
combined modes. In the core-crown structure, the CdSe and CdS modes preserve a more
independent behaviour with only interface modes forming overtones with core phonons.
Fig. 1. Representative resonant Raman spectra of two types of CdSe/CdS NPL morphologies shown in the insets.
Keywords: Semiconductor Nanocrystals; Nanoplatelets; Interface; Core-Shell; Phonons; Raman;
Infrared Spectroscopy.
References
[1] J.M. Pietryga Y.-S. Park, J. Lim, A.F. Fidler, W. K. Bae, S. Brovelli, V.I. Klimov Chem. Rev. 116
(2016) 10513.
[2] S. Ithurria, M. D. Tessier, B. Mahler, R. P. S. M. Lobo, B. Dubertret, A. L. Efros. Nat. Mater. 10
(2011) 936.
XIV
h
International Conference on Molecular Spectroscopy, Białka Tatrzańska 2017
29
I–11
X-band EPR imaging characterization of psoriasis vulgaris skin
Kouichi Nakagawa
1
, Stoko Minakawa
2
, Daisuke Sawamura
2
,
and Hideyuki Hara
3
1
Division of Regional Innovation, Graduate School of Health Sciences, Hirosaki University, 66-1
Hon-Cho, Hirosaki 036-8564, Japan, e-mail: nakagawa@hiroaki-u.ac.jp
2
Department of Dermatology, Graduate School of Medicine, Hirosaki University, 5 Zaifu-Cho,
Hirosaki 036-8562, Japan
3
Bruker BioSpin K. K., 3-9, Moriya-Cho, Kanagawa-ku, Yokohama 221-0022, Japan
We investigated locations and identification of structural abnormality of the stratum
corneum (SC) in patients with psoriasis vulgaris (PV) by using X-band EPR imaging. The X-
band EPR spin-probe imaging of PV-SC samples provided a useful image concerning the status
of the SC.
The Hirosaki University Internal Review Board approved all protocols used in this study.
For EPR imaging, a Bruker E500 ELESYS system was used. Spin probe (5-doxylstearic acid, 5-
DSA) solution was used to investigate structural aspects of PV-SC [1, 2]. We measured the thick
SC, the outermost layer for PV. The control SC was taken from skin lesions on the forearms.
A small, broad three-line pattern of 5-DSA in PV-SC was observed. The spectral pattern of
PV-SC was quite different from those of the control SC. Two-dimensional (2D) imaging using
X-band EPR imager showed that radical locations vary between control and PV skin [3]. The
results showed that the intense red signal was due to probe penetration into the PV skin. No red
lesion region was observed in the control. The EPR images showed various sizes and number
distribution concerning the disordered states in the SC. Thus, X-band EPR imaging can be
useful for detecting and identifying the location of abnormality of the SC states. In addition,
EPR imaging can potentially offer further quantitative insights into skin-lipid states.
D
is
ta
n
c
e
[
m
m
]
Distance [mm]
3 mm
PV
Control
Fig. 1. The image shows the psoriasis vulgaris (PV) (top) and control (bottom) samples.
The aqueous solution of the spin probe, 5-doxylstearic acid (5-DSA) was used.
Keywords: EPR imaging; skin structure; spin probe; psoriasis vulgaris; ESR
Acknowledgment
Part of this research was supported by a Grant-in-Aid for Exploratory Research (15K12499) from the Japan
Society for the Promotion of Science (JSPS) (K.N.).
References
[1] K. Nakagawa, S. Minakawa, and D. Sawamura, J. Dermatol. Sci., 65 (2012) 222.
[2] K. Nakagawa, S. Minakawa, and D. Sawamura, Appl. Magn. Reson., 44 (2013) 941.
[3] K. Nakagawa, S. Minakawa, and D. Sawamura, J. Dermatol. Sci., 81 (2016) 71.
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