XIV
h
International Conference on Molecular Spectroscopy, Białka Tatrzańska 2017
51
T1: O–9
The effect of annealing temperature on silicon oxycarbide obtained
from 1,3,5,7,9,11,13,15-octakis(dimethylsilyloxy)pentacyclo
[9.5.1.13,9.15, 15.17,13]octasiloxane-based polymers
Wiktor Niemiec
1
, Przemysław Szczygieł
1
, Piotr Jeleń
1
, and Mirosław Handke
1
1
Faculty of Materials Science and Ceramics, AGH University of Science and Technology,
Al.Mickiewicza 30, 30-059 Kraków, Poland, e-mail: wniemiec@agh.edu.pl
Silicon oxycarbide is a material combining outstanding thermal resistance with good
mechanical properties and the applicability as thin coatings. This material is based on
amorphous SiO
2
structure in which some of O
2–
ion pairs are substituted for a single C
4–
anion.
Carbon is also present in form of condensed aromatic rings, which form “free carbon” phase.
The only way of obtaining the silicon oxycarbide is the annealing of polymers containing Si-C
and Si–O bonds in temperatures between 600 and 1000°C. These polymers can be either linear
or crosslinked and synthesized in a number of ways including polycondensation via sol-gel
method. Usually the precursors are simple D (containing two alcoxy and two alkyl or aryl
groups), T (containing three alcoxy and one alkyl or aryl group) or Q (containing four alcoxy
groups) monomers.
In this work a number of gels were obtained from 1,3,5,7,9,11,13,15-octakis
(dimethylsilyloxy)pentacyclo[9.5.1.13,9.15,15.17,13]octasiloxane. The hydrogen in Si–H bond
was substituted for ethoxy (or silanol) group using various catalysts with different efficiency and
subsequently polycondesated. This leads to materials built from cubes formed from eight Q
groups interlinked with bridges of two D groups. The materials were then annealed in 600, 700,
800 and 900°C in argon atmosphere and their structure was investigated using IR, XRD and
29
Si
NMR methods. The results were compared with materials synthesized from other monomers
which also condensate to acquire gels with 1:1 silicon to carbon atom ratio, including equimolar
tetraethoxysilane and diethoxydimethylsilane mixture and triethoxymethylsilane.
Keywords: silicon oxycarbide; sol-gel; IR; XRD
Acknowledgment
Wiktor Niemiec would like to thank National Science Centre Poland for financial support in form of grant
No. UMO-2014/13/D/ST8/03243.
XIV
h
International Conference on Molecular Spectroscopy, Białka Tatrzańska 2017
52
T1: O–10
Raman imaging – a modern tool for 2D materials analysis
Agnieszka Sozańska
1
1
Renishaw Sp z o.o., ul. Osmańska 12, 02-823 Warsaw, Poland,
email: agnieszka.sozanska@renishaw.com
Raman spectroscopy (and Raman imaging) has become a powerful, noninvasive method to
characterize graphene and related materials. A large amount of information such as disorder,
edge and grain boundaries, thickness, doping, strain and thermal conductivity of graphene and
other 2D materials can be learned from the Raman spectrum and its behavior under varying
physical conditions
In this work we compare and contrast the different solutions for maintaining focus and
conducting Raman imaging on 2D materials with uneven, complex surfaces. We describe and
illustrate the application of the new LiveTrack™ dynamic focus tracking technology, which not
only provides in-focus Raman images of the most challenging samples but also topographic
information, allowing three dimensional surface Raman images to be generated.
We discuss and present data on a range of extremely difficult samples including graphene on a
Cu foil, a sample that is rough on a micrometre length scale. We will demonstrate dynamic
measurement of a polyethylene pellet undergoing phase transitions in a temperature cell,
demonstrating that LiveTrack can be used to maintain focus in moving systems.
As a complete picture of novel 2D materials characterization (like ReS2) a new tool of low
frequency Raman imaging will be shown, including share modes and breathing modes analysis.
Keywords: Raman spectroscopy; 2D materials; imaging
XIV
h
International Conference on Molecular Spectroscopy, Białka Tatrzańska 2017
53
T1: O–11
3D Ag nanosponge aggregate with incorporated testing adsorbates
as a sample for effective SER(R)S spectral detection
Veronika Sutrova
1,2
, Ivana Sloufova
1
, Martina Nevoralova
2
, and Blanka Vlckova
1
1
Department of Physical and Macromolecular chemistry, Charles University, Hlavova 2030/8,
Prague, 128 43, Czech Republic, e+mail: sutrovav@natur.cuni.cz
2
Department of Morphology and Rheology, Institute of Macromolecular chemistry ASCR, Heyrovsky
Sq. 2, Prague, 162 06, Czech Republic
Surface-enhanced Raman scattering (SERS) and Surface-enhanced resonance Raman
scattering (SERRS) are well-known spectro-analytical methods, which utilize enhancement of
Raman scattering by plasmonic metal nanostructures, e.g. Ag and Au nanoparticles (NPs).
Effective localization of molecules into “hot spots” (i.e. strong, nanoscale localized optical
fields generated in plasmonic metal nanostructures, such as nanoparticle (NP) assemblies, by an
external optical excitation) provides large enhancement of Raman signal. Presence of “hot
spots” has been predicted and proved experimentally in fractal aggregates [1, 2] and in dimers of
Ag NPs [3, 4]. Recently, we obtained strong indications about the presence of “hot spots” in 3D
Ag nanosponge aggregates [5].
In this contribution, we report preparation and SERS spectral investigation of 3D Ag
nanosponge aggregates, which were assembled from 2D fused fractal aggregates (D = 1.87 ±
0.02) resulting from modification of AgNPs hydrosol by Cl
–
and by hydrophilic [Ru(bpy)
3
]
2+
dication and hydrophobic fullerene C
60
as the testing adsorbate.
AgNPs hydrosol was prepared by reduction of AgNO
3
by NH
2
OH∙HCl [6]. For SERS
measurements, 3D Ag nanosponge aggregates with incorporated [Ru(bpy)
3
]
2+
cations, fullerene
C
60
and chloride anions were prepared and overlayed by a thin layer of aqueous phase.
SERS, SER(R)S and SERRS spectra were measured at 4 excitation wavelengths: 780, 633,
532 and 445 nm, and the limits of [Ru(bpy)
3
]
2+
and C
60
spectral detection were determined. The
limit of the SERS spectral detection of fullerene C
60
(1×10
–6
M) at all excitation wavelengths
was higher than for [Ru(bpy)
3
]
2+
cations. This is due to less effective incorporation of molecules
of fullerene C
60
into the Ag aggregate internal structure. The limit of the SERRS (1×10
–15
M)
and SER(R)S (1×10
–14
M) limits of detection of [Ru(bpy)
3
]
2+
determined at 445 and 532 nm
excitations, respectively, correspond to the single molecule level of the complex detection. Its
achievement is attributed to a large electromagnetic mechanism enhancement experienced by
[Ru(bpy)
3
]
2+
incorporated into “hot spots”, to an efficient localization of “hot spots” in the 3D
aggregate to the focus of the laser beam in micro-Raman spectral measurements and to a
molecular resonance contribution to the overall enhancement. Another benefit for SERS/SERRS
spectral measurements from the 3D Ag nanosponge aggregate is protection of the analyte (i.e.
[Ru(bpy)
3
]
2+
, fullerene C
60
) against thermal decomposition by the thin aqueous phase overlayer.
Keywords: Ag nanosponge; aggregate, [Ru(bpy)
3
]
2+
; fullerene; single-molecule detection
Acknowledgment
Financial support through grants 892217 (GAUK), 17-05007S (GACR), TE01020118 (TACR) and
POLYMAT LO1507 (MSMT, NPU I) is gratefully acknowledged.
References
[1] M.I. Stockman, V.M. Shalaev, M. Moskovits, R. Botet, T.F. George, Phys. Rev. B., 46 (1992) 2821.
[2] P. Zhang, T.L. Haslett, C. Douketis, M. Moskovits, Phys. Rev. B. 57 (1998) 15513.
[3] H. Xu, J. Aizpurua, M. Käll, P. Apell, Phys. Rev. E., 62 (2000) 4318.
[4] B. Vlčková, M. Moskovits, I. Pavel, K. Šišková, M. Sládková, M. Šlouf, Chem.Phys.Lett. 455 (2008)
131.
[5] V. Sutrová, I. Šloufová, M. Nevoralová, B. Vlčková, J. Raman. Spectr., 46 (2015) 559.
[6] N. Leopold, B. Lendl J. Phys. Chem. B 107 (2003) 5273.
Dostları ilə paylaş: |