XIV
h
International Conference on Molecular Spectroscopy, Białka Tatrzańska 2017
94
T3: O–13
Synthesis and characterisation of new types of nanoresonators
for Raman analysis of surfaces
Heman Abdulrahman
1
, and Andrzej Kudelski
1
1
Faculty of Chemistry, University of Warsaw, Pasteur 1, 02-093 Warsaw, Poland, e-mail:
hemin.80@mail.ru
Surface analysis of various materials (especially in the in situ conditions) is very important from
the economic and scientific point of view. Such studies are especially difficult for so-called buried
interfaces (e.g., the surface of the solid sample in the liquid or the high pressure gas), a situation
which occurs in very important from the practical point of view interfaces of various biological
samples in their “natural” environment. One of the tools which can be used for investigations of such
interfaces is developed by Tian et al. shell-isolated nanoparticle-enhanced Raman spectroscopy –
SHINERS [1]. In this approach, the analysed surface is covered with the layer of plasmonic
nanoparticles (the plasmonic core is covered by the thin layer of transparent material) and then the
Raman spectrum of the investigated sample is recorded. Metal cores of nanoparticles act as
electromagnetic resonators, significantly enhancing the electric field of the incident electromagnetic
radiation, and hence leading to very large increase of the Raman signal (the increase of the efficiency
of Raman scattering is roughly proportional to the fourth power of the field enhancement). The
ultrathin protecting coating does not damp surface electromagnetic enhancement, however, separates
nanoparticles from direct contact with the probed material and keeps them from agglomerating [2, 3].
In this contribution we present some new types of nanoresonators for SNINERS measurements.
For example, for measurements in the alkali environment we developed Ag@MnO
2
nanoresonators.
Such nanostructures are significantly more efficient in the enhancing Raman signal than the
previously used for SHINERS measurements in the alkali environment Au@MnO
2
nanostructures. In
comparison to highly active in SHINERS spectroscopy Ag@SiO
2
nanostructures, Ag@MnO
2
nanoparticles are significantly more stable in alkaline media. We have also developed very efficient
method of synthesis of highly efficient anisotropic silver nanoresonators covered by various
protecting layers (e.g., SiO
2
, MnO
2
or TiO
2
) – for example see Fig. 1. To increase the efficiency of
the synthesis of composite nanoresonators, and to decrease the unwanted agglomeration of formed
nanostructures, before deposition of the oxide layer (e.g., SiO
2
, MnO
2
or TiO
2
) silver nanoparticles
have been covered with very thin Ag
2
S layer.
The higher SHINERS activity of anisotropic nanoparticles is probably due to many sharp apexes
and
edges
on
their
surface.
Some
examples
of
practical
SHINERS
measurements
will
be
also
presented.
Fig.
1.
TEM
images
of
nanoresonators
for
SHINERS
measurements:
left
–
Ag@Ag
2
S@SiO
2
,
right
–
Ag@Ag
2
S@MnO
2
.
Keywords:
surface-enhanced
Raman
spectroscopy;
shell-isolated
nanoparticle-enhanced
Raman
spectroscopy;
SHINERS
Acknowledgment
This work was financed from the funds of the National Science Centre (Poland) allocated on the basis of the
decision number DEC-2013/11/B/ST5/02224.
References
[1] J.F. Li, Y.F. Huang, Y. Ding, Z.L. Yang, S.B. Li, X.S. Zhou, F.R. Fan, W. Zhang, Z.Y. Zhou, D.Y. Wu, B.
Ren, Z.L. Wang, Z.Q. Tian, Nature 464 (2010) 392.
[2] H.B. Abdulrahman, J. Krajczewski, D. Aleksandrowska, A. Kudelski, J. Phys. Chem. C 119 (2015) 20030.
[3] H.B. Abdulrahman, K. Kołątaj, P. Lenczewski, J. Krajczewski, A. Kudelski, Appl. Surf. Sci. 388 (2016) 704.
XIV
h
International Conference on Molecular Spectroscopy, Białka Tatrzańska 2017
95
T3: O–14
Photochemical synthesized anisotropic gold nanoparticles
as highly efficient SERS nanoresonators
Jan Krajczewski
1
, Karol Kołątaj
1
, and Andrzej Kudelski
1
1
Laboratory of Molecular Interactions, Faculty of Chemistry, University of Warsaw, ul. Pasteura 1,
02-093 Warsaw, Poland, e-mail: jkrajczewski@chem.uw.edu.pl
Noble metal nanoparticles interact with light in a specific way. Light with appropriate
frequency could excite electron cloud. This collective oscillation of electrons is called Surface
Plasmon Resonance (SPR). Anisotropic nanoparticles exhibit completely different plasmonic
properties than spherical ones. Theoretical calculations showed that the strongest enhancement
of the electromagnetic field occurs on sharp edges and tips of nanoparticles [1]. One of the
currently used methods for synthesis of anisotropic nanoparticles is photochemical
transformation. This method was for the first time described by Jin et al. [2]. However, in the
conditions described by Jin et al. only silver nanoparticles could be phototransformed from
spherical nanoseeds into anisotropic nanoparticles. Gold nanoseeds with the same average
diameter exhibit much higher photostability. Unfortunately, silver nanoparticles are highly toxic
for live cells and contact with silver nanoparticles induces change of the structure of many
biomolecules like DNA or proteins. Therefore, gold nanoparticles are significantly better for
analysis of many biomolecules. Therefore efficient method of synthesis of anisotropic gold
nanoparticles is still developed.
In this work we present some approaches to photochemical transformation of gold nanoseeds
into anisotropic nanostructures. Synthesize of core-shell Au@Ag nanoparticles by
photochemical method was also investigated. However, as described above, gold nanoparticles
exhibit much higher photostability than silver nanoseeds. Finally, anisotropic gold nanoparticles
were synthesized by photochemical method described by Y. Zhai et al. [2]. Influence of the
wavelength and duration of the process was carefully investigated. Optical and structural
properties of obtained anisotropic nanoparticles were studied. Obtained nanoparticles were
tested as optical nanoresonators in SERS measurements. SERS measurements were carried out
on monolayer of adsorbed analyte (p-MBA and MES) on platinum plate. Analysis of recorded
spectra showed that anisotropic gold nanoparticles generate significantly higher enhancement
factor of electromagnetic fields then the same amount of spherical nanoparticles. What is
important obtained anisotropic gold nanoparticles exhibit high durability and are stable longer
than 5 weeks.
Keywords: SERS, gold anisotropic nanoparticles, PDTr, plasmon driven transformation
References
[1] E. Hao, G. C. Shatz, J. Chem. Phys. 120 (2004) 357.
[2] Y. Zhai, J. DuChene, Y. Wang, J. Qiu, A, Johnstone-Peck, B. You, W. Guo, B. DiCiaccio, K. Qian, E.
Zhao, F, Ooi, D. Hu, D. Su, E. Stach, W. Wey, Nat. Mater. 15 (2016) 889.
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