Micro-Raman study of nanocomposite porous films with silver nanoparticles prepared using pulsed laser deposition
Nanocomposite porous films with silver nanoparticle (Ag NP) arrays were prepared by the pulsed laser deposition from the back flux of erosion torch particles in argon atmosphere on the substrate placed at the target plane. Preparation conditions of the films were set by argon pressure, energy densit...
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Інститут фізики напівпровідників імені В.Є. Лашкарьова НАН України
2015
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| Цитувати: | Micro-Raman study of nanocomposite porous films with silver nanoparticles prepared using pulsed laser deposition / V.V. Strelchuk, O.F. Kolomys, B.O. Golichenko, M.I. Boyko, E.B. Kaganovich, I.M. Krishchenko, S.O. Kravchenko, O.S. Lytvyn, E.G. Manoilov, Iu.M. Nasieka // Semiconductor Physics Quantum Electronics & Optoelectronics. — 2015. — Т. 18, № 1. — С. 46-52. — Бібліогр.: 18 назв. — англ. |
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irk-123456789-1207262017-06-13T03:03:35Z Micro-Raman study of nanocomposite porous films with silver nanoparticles prepared using pulsed laser deposition Strelchuk, V.V. Kolomys, O.F. Golichenko, B.O. Boyko, M.I. Kaganovich, E.B. Krishchenko, I.M. Kravchenko, S.O. Lytvyn, O.S. Manoilov, E.G. Nasieka, Iu.M. Nanocomposite porous films with silver nanoparticle (Ag NP) arrays were prepared by the pulsed laser deposition from the back flux of erosion torch particles in argon atmosphere on the substrate placed at the target plane. Preparation conditions of the films were set by argon pressure, energy density of laser pulses, their amount and substrate position relatively to the torch axis. The films were prepared with gradient thickness, variable Ag NP sizes and distance between them along the length of substrate as well as corresponding maxima in the spectra of local surface plasmon absorption. Plasmon effects of the Raman scattering enhance in the matter of the Ag NP shell gave the opportunity to register the spectral bands caused by an extremely small quantity of silver compounds with oxygen and carbon. The possible nature of individual bands in the Raman spectrum was analyzed. The obtained results are important for interpretation of the Raman spectra of analytes based on the prepared SERS substrates. 2015 Article Micro-Raman study of nanocomposite porous films with silver nanoparticles prepared using pulsed laser deposition / V.V. Strelchuk, O.F. Kolomys, B.O. Golichenko, M.I. Boyko, E.B. Kaganovich, I.M. Krishchenko, S.O. Kravchenko, O.S. Lytvyn, E.G. Manoilov, Iu.M. Nasieka // Semiconductor Physics Quantum Electronics & Optoelectronics. — 2015. — Т. 18, № 1. — С. 46-52. — Бібліогр.: 18 назв. — англ. 1560-8034 DOI: 10.15407/spqeo18.01.046 PACS 78.30.Ly, 78.67.Rb, 81.07.Bc, 81.07.-b http://dspace.nbuv.gov.ua/handle/123456789/120726 en Semiconductor Physics Quantum Electronics & Optoelectronics Інститут фізики напівпровідників імені В.Є. Лашкарьова НАН України |
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| description |
Nanocomposite porous films with silver nanoparticle (Ag NP) arrays were prepared by the pulsed laser deposition from the back flux of erosion torch particles in argon atmosphere on the substrate placed at the target plane. Preparation conditions of the films were set by argon pressure, energy density of laser pulses, their amount and substrate position relatively to the torch axis. The films were prepared with gradient thickness, variable Ag NP sizes and distance between them along the length of substrate as well as corresponding maxima in the spectra of local surface plasmon absorption. Plasmon effects of the Raman scattering enhance in the matter of the Ag NP shell gave the opportunity to register the spectral bands caused by an extremely small quantity of silver compounds with oxygen and carbon. The possible nature of individual bands in the Raman spectrum was analyzed. The obtained results are important for interpretation of the Raman spectra of analytes based on the prepared SERS substrates. |
| format |
Article |
| author |
Strelchuk, V.V. Kolomys, O.F. Golichenko, B.O. Boyko, M.I. Kaganovich, E.B. Krishchenko, I.M. Kravchenko, S.O. Lytvyn, O.S. Manoilov, E.G. Nasieka, Iu.M. |
| spellingShingle |
Strelchuk, V.V. Kolomys, O.F. Golichenko, B.O. Boyko, M.I. Kaganovich, E.B. Krishchenko, I.M. Kravchenko, S.O. Lytvyn, O.S. Manoilov, E.G. Nasieka, Iu.M. Micro-Raman study of nanocomposite porous films with silver nanoparticles prepared using pulsed laser deposition Semiconductor Physics Quantum Electronics & Optoelectronics |
| author_facet |
Strelchuk, V.V. Kolomys, O.F. Golichenko, B.O. Boyko, M.I. Kaganovich, E.B. Krishchenko, I.M. Kravchenko, S.O. Lytvyn, O.S. Manoilov, E.G. Nasieka, Iu.M. |
| author_sort |
Strelchuk, V.V. |
| title |
Micro-Raman study of nanocomposite porous films with silver nanoparticles prepared using pulsed laser deposition |
| title_short |
Micro-Raman study of nanocomposite porous films with silver nanoparticles prepared using pulsed laser deposition |
| title_full |
Micro-Raman study of nanocomposite porous films with silver nanoparticles prepared using pulsed laser deposition |
| title_fullStr |
Micro-Raman study of nanocomposite porous films with silver nanoparticles prepared using pulsed laser deposition |
| title_full_unstemmed |
Micro-Raman study of nanocomposite porous films with silver nanoparticles prepared using pulsed laser deposition |
| title_sort |
micro-raman study of nanocomposite porous films with silver nanoparticles prepared using pulsed laser deposition |
| publisher |
Інститут фізики напівпровідників імені В.Є. Лашкарьова НАН України |
| publishDate |
2015 |
| url |
http://dspace.nbuv.gov.ua/handle/123456789/120726 |
| citation_txt |
Micro-Raman study of nanocomposite porous films with silver nanoparticles prepared using pulsed laser deposition / V.V. Strelchuk, O.F. Kolomys, B.O. Golichenko, M.I. Boyko, E.B. Kaganovich, I.M. Krishchenko, S.O. Kravchenko, O.S. Lytvyn, E.G. Manoilov, Iu.M. Nasieka // Semiconductor Physics Quantum Electronics & Optoelectronics. — 2015. — Т. 18, № 1. — С. 46-52. — Бібліогр.: 18 назв. — англ. |
| series |
Semiconductor Physics Quantum Electronics & Optoelectronics |
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Semiconductor Physics, Quantum Electronics & Optoelectronics, 2015. V. 18, N 1. P. 46-52.
doi: 10.15407/ spqeo18.01.046
© 2015, V. Lashkaryov Institute of Semiconductor Physics, National Academy of Sciences of Ukraine
46
PACS 78.30.Ly, 78.67.Rb, 81.07.Bc, 81.07.-b
Micro-Raman study of nanocomposite porous films
with silver nanoparticles prepared using pulsed laser deposition
V.V. Strelchuk, O.F. Kolomys, B.O. Golichenko, M.I. Boyko, E.B. Kaganovich, I.M. Krishchenko,
S.O. Kravchenko, O.S. Lytvyn, E.G. Manoilov, Iu.M. Nasieka
V. Lashkaryov Institute of Semiconductor Physics, NAS of Ukraine,
41, prospect. Nauky, 03028 Kyiv, Ukraine, e-mail: dept_5@isp.kiev.ua
Abstract. Nanocomposite porous films with silver nanoparticle (Ag NP) arrays were
prepared by the pulsed laser deposition from the back flux of erosion torch particles in
argon atmosphere on the substrate placed at the target plane. Preparation conditions of
the films were set by argon pressure, energy density of laser pulses, their amount and
substrate position relatively to the torch axis. The films were prepared with gradient
thickness, variable Ag NP sizes and distance between them along the length of substrate
as well as corresponding maxima in the spectra of local surface plasmon absorption.
Plasmon effects of the Raman scattering enhance in the matter of the Ag NP shell gave
the opportunity to register the spectral bands caused by an extremely small quantity of
silver compounds with oxygen and carbon. The possible nature of individual bands in the
Raman spectrum was analyzed. The obtained results are important for interpretation of
the Raman spectra of analytes based on the prepared SERS substrates.
Keywords: Raman spectroscopy, silver compound, Ag nanoparticle arrays, surface-
enhanced Raman scattering, pulsed laser deposition.
Manuscript received 15.09.14; revised version received 10.12.14; accepted for
publication 19.02.15; published online 26.02.15.
1. Introduction
The silver nanoparticles (NPs) have a high efficiency at
excitation of the local surface plasmon resonance, which
has wide application in the surface-enhanced Raman
scattering (SERS) of different analytes, photo-
luminescence of Ge and Si quantum dots, for creation of
sensors and optoelectronic structures. The advantages of
Ag NPs in comparison with Au ones are related with the
high density of conduction electrons, favorable fre-
quency dependence of complex dielectric permittivity in
the visible spectral range and in absence of competition
between plasmon and interband absorption. Unlike gold,
the energy of interband sp→d transition in silver is
located in the UV region of the spectrum. However,
silver is unstable and subjected to oxidation with
formation of compounds with oxygen, sulfur, carbon,
nitrogen and chlorine [1]. It leads to complication in
interpretation of Raman spectra when using SERS
substrates with Ag NPs, because of localization of the
characteristic bands inherent to silver compounds of the
Ag NP shell in the frequency range 100 up to 1600 cm
–1
.
Determination of the nature of these compounds is
required to realize activation of SERS analytes,
comprising choice of activator and analyte. Thereby,
identification of oxidation products in Ag NP shell that
are used for the SERS spectroscopy is an actual task.
Micro-Raman spectroscopy has seldom application
in the role of initial analytic method for identification of
chemical compounds on metal surface because of
absence of the corresponding database of benchmark
Raman spectra registered for the high-purity certified
chemical compounds. In 2012, it was published the work
in which, from the one hand, the short analysis of the
Raman spectra of silver compounds prepared using
different technologies in accord with literature data, was
Semiconductor Physics, Quantum Electronics & Optoelectronics, 2015. V. 18, N 1. P. 46-52.
doi: 10.15407/ spqeo18.01.046
© 2015, V. Lashkaryov Institute of Semiconductor Physics, National Academy of Sciences of Ukraine
47
presented, and from the other hand, it was carried out the
micro-Raman characterization of the certified silver
compound powders: oxide (Ag2O), chloride (AgCl),
sulfide (Ag2S), sulfite (Ag2SO3), sulfate (Ag2SO4),
carbonate (Ag2CO3), acetate (AgC2H3O2), nitrate
(AgNO3) with the purity level higher than 99.99% [2].
As a result, it was proposed the catalogue of Raman
spectra of the mentioned silver compounds, which
allows characterization of silver oxidation processes.
Today a substantial amount of the works is devoted
to Raman investigations, for example of the processes of
chemical interaction of polycrystalline silver with О2,
Н2О, СО2, ethylene, methanol [3], thermal dissociation
of silver oxide [4], to study mechanisms of
chemisorptions of oxygen on the silver analytic catalyzer
[5], on the thermal-induced transformation of different
silver oxides in the films of electrolytic silver [6],
plasmon-active catalyzers of the reactions with H2, O2,
CO, hydro-carbonates based on Ag/AgOx NPs [7], etc.
But due to characterization by different set of silver
compounds of the investigation objects prepared under
different technological conditions, using these Raman
spectra is rather limited, although they also contain
much important information.
For preparation of SERS substrates with Ag NPs, it
was used many approaches including chemical, vacuum
processes, electron-beam lithography, formation of
various templates with colloid NPs, rough films,
nanoparticle arrays including the organized ones.
Especial interest is caused by forming the porous films
with Ag NP arrays, because they are characterized by
large internal surface for the analyte, possibility of
formation in the pores the so-called “hot spots”, spots
with high values of local electro-magnetic fields that
mostly provide the enhance in analyte Raman spectra. It
is known about the porous nanocomposite systems in the
form of porous glass-ceramics, porous layers of
aluminum oxides, silicon prepared by anodization when
the pore walls are covered with the films of silver (gold)
[8-11]. It was formed the structures of porous gold from
the Au/Ag alloys by using the method of selective
etching of silver [12].
In the literature, there are no information
concerning production of the porous silver (por-Ag)
films formed in vacuum and their application as a SERS-
substrates, also there are no data concerning Raman
investigations of chemical compounds in the Ag NP
shell in por-Ag films.
Recently, the SERS-substrates based on films with
Ag NP arrays were prepared using pulsed laser
deposition (PLD) from the direct flux of erosion torch
particles on the substrate located at some distance along
the normal to the target plane [13]. Taking into account
the advantages for the SERS substrates of porous films
with Ag NP arrays, we have developed the
corresponding PLD method that is different as compared
to that in [13]. Deposition of Ag NPs is performed from
the back low-energy flux of Ag particles on the substrate
located in the target plane [14-16]. Under these
conditions, it is possible to provide formation of silver
chemical compounds in the Ag NP shell, which,
correspondingly will affect the efficiency of SERS.
Therefore, the aim of this work is identification, by
using micro-Raman spectroscopy, of silver compounds
of Ag NP shell that can be formed during preparation of
the SERS substrates with nanocomposite porous films
containing Ag NP arrays.
2. Experimental
Nanocomposite porous films (pores and Ag NPs) were
prepared using the PLD method (see the insert to Fig. 1)
from the back flux of the low-energy particles of erosion
torch on the glass substrates located in the target plane
(6). Nd:YАG laser radiation (λ =1.06 µm, p = 10 ns, fp =
25 Hz) with the energy in the pulse 200 mJ (1) was
focused on the surface of silver target (5) that can move.
Deposition was performed in the argon atmosphere
under the pressure P = 10…50 Pa (2). The density of the
energy of laser pulse was about j = 5…20 J/сm
2
. The
target irradiation time was varied from 1 up to 30
minutes, which corresponds to the change in the amount
of pulses N = 1500…45000. Under the pulsed laser
irradiation of the target, the erosion torch (4) is formed
in the vacuum chamber. In the torch region, interaction
of silver atoms between themselves and with gas atoms
takes place, which is accompanied with creation of
clusters and their deposition on the substrate with
formation of structure of Ag NPs: Ag-core/Ag
compound shell. In the argon atmosphere, the cluster
energy is scattered when colliding with atoms. The
deposition regime provides preparation of porous films.
Herewith, in the film regions located near the torch axis,
it is deposited a larger amount of Ag NPs with larger
sizes. With increasing the distance from the torch axis, a
smaller amount of Ag NPs with smaller sizes is formed.
Also, the porosity and thickness of the por-Ag film are
changed as functions of the distance from the torch axis
[14-16].
The thickness and the surface morphology of the
por-Ag films were investigated by means of atomic force
microscopy (AFM) using the Nanoscope IIIa scanning
probe microscope operating in the taping mode. The
silicon probes with the nominal radii of the tip apex
close to 10 nm were used. Thickness variation of the
por-Ag film along the sample was measured using the
series of step height measurements. Sharp edged
substrate-film steps were produced using the lift-off
lithography process. The effective thickness of films at a
given position was determined as a distance between
centers of two maxima in the height histogram
corresponding to the substrate and film levels.
Investigation of the por-Ag films microstructure were
also carried out using the scanning electron microscope
(SEM) JSM-6490 LV (JEOL), with the energy-dispersed
spectrometer [16] and using the transmission electron
microscope (TEM) JEM-1011 (JEOL).
Semiconductor Physics, Quantum Electronics & Optoelectronics, 2015. V. 18, N 1. P. 46-52.
doi: 10.15407/ spqeo18.01.046
© 2015, V. Lashkaryov Institute of Semiconductor Physics, National Academy of Sciences of Ukraine
48
Fig. 2. (a) АFM image in the region of the por-Ag film on the distance from the erosion torch axis L, mm: 5 (1), 10 (2), 15 (3);
(b) sectional (along the dashed line) analysis of the film and (c) histogram of distribution of the Ag NP sizes in these three
regions of the wedge.
Fig. 1. Dependence of the thickness on the substrate coordinate
d (L) for por-Ag films prepared at j = 5 J/сm2, N = 30000, PAr,
Pa: 13.5 (1), 20 (2). In the insert – the scheme of the PLD
vacuum set: 1 – laser beam, 2 – gas inflation, 3 – vacuum
chamber, 4 – erosion torch, 5 – target, 6, 7 – substrates, 8 – to
the vacuum pump.
Transmission spectra of the films were registered
with the spectrophotometer SF-26 in the wavelength
range 340 up to 1200 nm.
Micro-Raman spectra were measured using the
triple spectrometer Horiba Jobin Yvon T64000 equipped
with confocal optical microscope. As an optical
excitation source, the Ar-Kr laser line with ex =
488.0 nm was used. To prevent the photo-induced
changes in silver compounds, the power of excitation
laser radiation was reduced down to few milliwatts, the
measuring time was equal to 100…200 s. The laser
beam was focused on the sample surface in the spot with
the diameter of about 0.7 µm. The spatial mapping of the
optical spectra of studied structures was carried out via
the automatic movement of the table with the step
0.1 µm. The accuracy of determination of the frequency
of phonon bands was equal to 0.15 cm
–1
.
In this work, identification of silver chemical
compounds in Ag NP shell in the por-Ag films by their
vibrational bands in the Raman spectra was performed
using the data of works [2-7]. The Raman spectra were
mainly analyzed being based on comparison with the
basic spectra presented in [2].
3. Results and discussion
In Fig. 1, being based on AFM measurements, it has
been shown the dependence of the thickness (d) of the
por-Ag films as a function of the distance from the
erosion torch axis (L). The obtained profile of the
thickness is similar to the wedge shape: at the increase of
the distance from the torch axis, the films thickness
decreases. The thickness of films was increased even
with an insignificant increase of the argon pressure
(compare curves 1 and 2 in Fig. 1).
With increasing the argon pressure, energy density,
amount of pulses of target irradiation, the thickness of
por-Ag films increases. In the mentioned range of
formation conditions, the por-Ag film thickness lies
within the values between 10 and 100 nm.
Semiconductor Physics, Quantum Electronics & Optoelectronics, 2015. V. 18, N 1. P. 46-52.
doi: 10.15407/ spqeo18.01.046
© 2015, V. Lashkaryov Institute of Semiconductor Physics, National Academy of Sciences of Ukraine
49
In Fig. 2a, it was presented the AFM 3d-images of
11 µm por-Ag film deposited in the regime j =
5 J/сm
2
, Р = 13.5 Pа, N = 30000 that are related to the
substrate regions at various distances from the axis of
erosion torch with different sizes of Ag-Nps and pores.
With increasing the distance from the erosion torch.
Analysis of film surface morphology evidences about
presence of Ag NPs and hollows between them in the
same concentration. It was seen that the size of Ag NP
and hollows decreases with increasing the distance
from the erosion torch axis. In Fig. 2b, it was shown
height profiles of the por-Ag film surface relief
obtained along the dashed line for three regions of the
wedge. One can see that the surface relief amplitude is
substantially smaller in the region of por-Ag film with
a smaller thickness (the longer distance from the torch
axis). In Fig. 2c, the histograms of Ag NPs by the sizes
(effective diameters) in dependence on the distance
from the torch axis are presented. The size distribution
shape transforms from the Gauss type to log-normal
one, when the distance from the torch axis increases.
The corresponding value of NPs diameters decreases
from 35 down to 20 nm. It should be noted that
correlation between the thickness of film points and Ag
NPs sizes takes place. The surface relief amplitude for
the films has the same order of magnitude of their
thickness. This evidence suggests greater porosity of
por-Ag films.
Fig. 3a shows the SEM image of the por-Ag film
on Si substrate. In the image, one can see light and dark
spots of various shapes, which is indicative of the
existence of Ag NPs, their conglomerates and surface
pores in comparable concentrations. Fig. 3b presents the
TEM image of the por-Ag film. The corresponding
histograms of distribution of Ag NPs by their sizes,
obtained from the analysis of SEM and TEM images are
shown in Figs. 3c and 3d. For the films with the smallest
thickness, isolated spherical nanoparticles, i.e. island
films, are typical. Using the method of X-ray dispersion
spectroscopy, it was performed the elemental analysis of
the por-Ag film deposited on the Si substrate (Fig. 3e)
[16]. It was shown that, in the spectra except silver
contained silicon (material of the Si substrate), carbon
and oxygen in the Ag NP aggregates, it was additionally
registered the less sulfur, chlorine and nitrogen. It is
related with the fact that the concentration of the latter is
lower than that of the oxygen and carbon atoms. The
existence of carbon can be caused by uncontrolled
contamination inserted in the process of por-Ag film
deposition in the vacuum chamber by using the oil
pump. Except this, oxygen is an impurity in argon and in
silicon oxide on the used Si substrate. The value of the
weight percents for uncontrolled impurities in the por-
Ag film determined from the X-ray spectrum are as
follows: C – 1.55; O – 1.48; Si – 73.58 (substrate); S –
0.34; Cl – 0.46; Ag – 22.59.
The transmission spectra, T(), of the porous films
with the Ag NP arrays prepared at various argon
pressures are shown in Fig. 4. One can see the wide
bands of plasmon absorption in the wavelength range
400 to 1000 nm. At the increase of the argon pressure,
the maximum shifts towards the long-wave region, the
transmission value decreases, and the spectrum expands.
This type of the spectra is caused by two reasons. First,
with increasing the argon pressure the size of the torch
decreases. It leads to enhancement of the interaction
between silver atoms, the sizes of silver clusters in the
torch increase, too. With larger sizes of silver clusters,
the transmission spectra shift towards the more long-
wave region. Second, oxygen chemisorption, formation
of the silver compounds with carbon in the shell of Ag
NPs lead to the change in the dielectric permittivity of
Ag NP shell and long-wave shift of the plasmon spectra
[17]. Non-uniform expansion of the absorption band of
the surface plasmon resonance is caused by dispersion of
nanoparticle sizes and can be due to size-depending
scattering of electrons at the surface, if the nanoparticle
sizes become smaller than the average value of the free
path for electrons in bulk metallic silver (of about
200 nm) [18].
Fig. 3. (а) SЕМ image of por-Ag film (j = 5 J/сm2, N = 30000,
PAr = 13.5 Pа, L = 5 mm); (b) TEM image of por-Ag film (j =
5 J/сm2, N = 1500, PAr = 13.5 Pа, L = 15 mm); (c), (d) the
histograms of distribution of Ag NPs by their sizes,
correspondingly; (e) X-ray spectrum of por-Ag film from the
left to right: carbon, oxygen, silicon, sulfur, chlorine, silver.
Semiconductor Physics, Quantum Electronics & Optoelectronics, 2015. V. 18, N 1. P. 46-52.
doi: 10.15407/ spqeo18.01.046
© 2015, V. Lashkaryov Institute of Semiconductor Physics, National Academy of Sciences of Ukraine
50
Fig. 4. Transmission spectra of por-Ag films prepared at j =
5 J/сm2, N = 15000, L = 5 mm, PAr, Pа: 13.5 (1), 20 (2), 50 (3).
Fig. 5. Micro-Raman spectra of porous film with Ag NP arrays
(j = 20 J/сm2, N = 30000, PAr = 20 Pа) in the regions of the
film at the distance from the erosion torch axis between
20 mm (1) to 5 mm (4).
Fig. 5 shows the confocal micro-Raman spectra of
the por-Ag nanocomposite film (pores and Ag NP
arrays) in its various regions along the direction from the
erosion torch axis. In the Raman spectra, the following
typical intense clear bands are registered in three spectral
ranges: below 200 cm
–1
(96, 140 cm
–1
), within the range
200 to 600 cm
–1
– bands at 280, 348, 434, 475 cm
–1
,
within the range 600 to 1800 cm
–1
– band at 664 cm
–1
,
wide band at 780 cm
–1
, band at 970 cm
–1
with two
shoulders at 933 and 1012 cm
–1
, wide bands at 1165,
1355, 1585 cm
–1
with the shoulder at 1524 cm
–1
. The
spectra obtained near and far from the axis of erosion
torch are in general analogous, however, the intensities
of different bands change substantially. In particular, the
band intensity is larger from the regions that are near the
axis of erosion torch, which is caused by a larger
thickness of the por-Ag films as well as a larger content
of silver oxidation products in Ag NP shell. The spectra
obtained under changing of mentioned technological
parameters are also analogous, the intensity of different
bands changes inessentially. The possibility to observe
the Raman spectra in the chemical compounds inside the
shells of Ag NPs are associated with local surface
plasmon resonance in Ag NP core.
Let us analyze the possible nature of the silver
compounds that are formed in the process of por-Ag film
deposition. The intense bands at 96, 140 cm
–1
are
attributed to lattice vibrational modes of Ag NP cores. The
analogous intense bands in the range below 200 cm
–1
with
equal to these values of the frequency were observed in
numerous works, for example, for Ag2O (96, 146 cm
–1
),
Ag2CO3 (106 cm
–1
), AgC2H3O2 (102 cm
–1
with the
shoulder at 140 cm
–1
), Ag2S (93, 147 cm
–1
), Ag2SO3
(105 cm
–1
with the shoulder at 144 cm
–1
), AgNO3
(144 cm
–1
with the shoulders at 95 and 158 cm
–1
), AgCl
(95 cm
–1
with the shoulders at 143 and 190 cm
–1
), and
these bands are attributed to lattice vibrations of Ag [2].
Summarized in Table are the frequency positions of
characteristic bands in the por-Ag films within the
frequency range 200 to 1600 cm
–1
from Fig. 5, and, for
comparison, there were selected the most intense and
characteristic (bench mark) bands for the expected silver
compounds [2-7].
The wide bands with the clear maxima within the
frequency range 200 to 600 cm
–1
[2, 5]:
– for Ag2O (230 – 248, 342, 430, 487, 565 cm
–1
) are
caused by Ag–O valence bending vibrations,
moreover, the bands at 430 and 487 cm
–1
are
attributed to the tensile vibrations of the bulk Ag2O
compound;
– for Ag2CO3 (204 cm
–1
, the intense band is
attributed to Ag–C valence vibrations), for
AgC2H3O2 (258 cm
–1
, very intense band – C–O–Ag
bending modes);
– for Ag2S (243 cm
–1
, shoulder at 273 cm
–1
– Ag–S
valence vibrations), for Ag2SO3 (460 cm
–1
– O–S–O
symmetric bending vibrations (swinging)),
(602 cm
–1
– O–S–O asymmetric bending vibrations
(torsional)), for Ag2SO4 (432, 460, 623 cm
–1
–
O–S–O symmetric (asymmetric) bending vibrations
(swinging, torsional));
– for AgCl (233, 345, 409 cm
–1
, Ag–Cl valence
vibrations).
Within the spectral range 200 to 600 cm
–1
, it is the
most evident that the bands of the chemical compounds
of silver with oxygen, carbon, chlorine, and among the
compounds with sulfur, the most intense band is only for
Ag2S; there are no bands in the Raman spectrum of
AgNO3.
Semiconductor Physics, Quantum Electronics & Optoelectronics, 2015. V. 18, N 1. P. 46-52.
doi: 10.15407/ spqeo18.01.046
© 2015, V. Lashkaryov Institute of Semiconductor Physics, National Academy of Sciences of Ukraine
51
Table. The comparison of the measured Raman spectrum of por-Ag films within the range 200–1600 сm
–1 with the database for
the Raman scattering in the silver compounds.
por-Ag Ag2O AgCl Ag2CO3 AgC2H3O2 Ag2S
Ag2SO3
(Ag2SO4)
AgNO3
280 230–248 233 s
204 s,
283 w
258 vs
243 vs,
273 sh
348 s 342 345 w 341 sh
434–475 s
430,
487 s
409 vw 490 w
460
(432–480) w
664 vs 565 s 614 w, 664
602
(595, 623) w
698 vw
780
732, 804,
853 w
717 vw,
791 w
(933), 970
(1012) vs
933–950 s,
1072,
1100 vs
1075 w
933 s,
1030 w
964 (970) vs,
1076 (1079)
1030 vs
1165, 1278,
1355 s
1341 w
1346,
1410 s
1330 vw
1524–1585 vs 1507 w 1536 w
Letter symbols of the band intensities: vs – very strong; s – strong; w – weak; vw – very weak; sh – band shoulder; without any
symbols – less clear.
Within the range 600 to 1800 сm
–1
for Ag2O, it is
typical to observe the intense bands at 933 – 950, 1072,
1100 cm
–1
that are caused by Ag–O valence vibrations.
In the spectra of AgC2H3O2, it was observed the clear
maxima at 933 cm
–1
(C–CH3 symmetric bending
(swinging) vibrations), at 1410 cm
–1
(CH3 symmetric
bending vibrations), and more weak, as compared with the
latter, vibrational bands at 1346, 1536 cm
–1
(symmetric,
asymmetric valence vibrations). For AgNO3, typical is the
very intense phonon band at 1030 cm
–1
(N–O symmetric
valence vibrations) and more weak bands at 690, 717,
1330 cm
–1
(N–O bending (valence) vibrations). For
Ag2SO3 (Ag2SO4), the spectra are very similar: very
intense bands at 964 (970 cm
–1
) and at 1078 (1079 cm
–1
),
which are caused correspondingly by S–O symmetric
and asymmetric valence vibrations. For the compounds
AgCl, Ag2S, the vibrational bands are absent within this
range of Raman spectrum.
The performed analysis of the Raman spectra of
silver chemical compounds using the literature data
caused the choice of the benchmark bands that were
presented in Table. Table information obtained using the
method of comparison of the obtained spectrum of por-
Ag films and selected benchmark spectra of silver
chemical compounds allow determining the possible
nature of vibrations in the measured Raman spectra.
From Table, one can see that the band at 280 cm
–1
can indicate the existence of silver compounds with
oxygen, carbon, hydrogen, chlorine and sulfur as Ag2S
in the Ag NP shells. The band at 348 cm
–1
was registered
in the compounds of silver with oxygen, carbon,
hydrogen and chlorine. The band at 434 – 475 cm
–1
quite
often is attributed to the vibrations of Ag2O, in other
cases it can be caused by the vibrations in compounds
AgCl, AgC2H3O2 and Ag2SO3 (Ag2SO4). The most
probable nature of the registered bands at 624 cm
–1
is the
compounds of silver with oxygen, carbon (AgC2H3O2),
Ag2SO3 (Ag2SO4) and AgNO3, and for the band at
780 cm
–1
– vibrations in Ag2CO3 and AgNO3. The strong
bands at 970 cm
–1
with the shoulders at 932 and
1012 cm
–1
are caused by manifestation of the
compounds of silver with oxygen, carbon (AgC2H3O2),
sulfur (Ag2SO3, Ag2SO4) and nitrogen. The strong bands
observed at 1355, 1524 – 1585 cm
–1
are caused by the
compound of silver with carbon (Ag2CO3, AgC2H3O2).
Thus, according to micro-Raman spectroscopy the main
composition of shells on Ag NPs are silver compounds
with oxygen and carbon. It is noteworthy that the
revealed nature of the shells in Ag NPs, in the view of
mentioned compounds, coincides with X-ray spectral
data (see Fig. 3e).
The determined nature of Ag NPs shells, their
manifestation in the micro-Raman spectra allow, firstly,
to exclude some difficulties in interpretation of the
SERS spectra of analytes when controlling the
technology of preparation of the films with Ag NPs
arrays. Secondly, determination of chemical composition
inherent to the shells compounds of Ag NPs promotes
developing the more efficient SERS substrates by
controlling the processes of preparation of por-Ag films
as well as by selecting SERS activators and analytes.
4. Conclusions
Developed in this work is the method for preparation of
nanocomposite porous films with silver nanoparticle
arrays by using pulsed laser deposition from the back
flux of the erosion torch particles. The optimal
conditions of por-Ag film formation with the gradient
change in its thickness and sizes of Ag NPs as well as
pores have been determined. It has been investigated the
peculiarities of the absorption spectra that are related to
local surface plasmon resonance of Ag NPs. Using the
method of confocal micro-Raman spectroscopy, it has
been investigated the nature of the silver chemical
compounds in the silver nanoparticle shells in por-Ag
Semiconductor Physics, Quantum Electronics & Optoelectronics, 2015. V. 18, N 1. P. 46-52.
doi: 10.15407/ spqeo18.01.046
© 2015, V. Lashkaryov Institute of Semiconductor Physics, National Academy of Sciences of Ukraine
52
films. The bands in the Raman spectra at 96 and 140 cm
–1
are caused by lattice vibrational modes of Ag-core NPs.
The registered Raman bands at 280, 348, 434-475, 664,
780, 970 cm
–1
and at 1165-1355, 1524-1585 cm
–1
are
predominantly related to the compounds of silver with
oxygen and carbon. The obtained results will be used for
interpretation of the vibrational spectra of analytes
placed on the prepared SERS substrates.
References
1. E. Le Ru, P. Etchegoin, Principles of Surface
Enhanced Raman Spectroscopy and Related Plas-
monic Effects, first ed. Elsevier, Amsterdam, 2009.
2. I. Martina, R. Wiesinger, D. Sembrih-Simbürger, M.
Schreiner, Micro-Raman characterization of silver
corrosion products: Instrumental set up and reference
database // Raman Spectroscopy, 9, p. 1-8 (2012).
3. Chuan-Bao Wang, G. Deo, I.E. Wachs, Interaction
of polycrystalline silver with oxygen, water, carbon
dioxide, ethylene, and methanol: in situ Raman and
catalytic studies // J. Phys. Chem. B, 103, p. 5645-
5656 (1999).
4. G.I.N. Waterhouse, G.A. Bowmaker, J.B. Metson,
The thermal decomposition of silver (I, III) oxide:
A combined XRD, FT-IR and Raman spectroscopic
study // Phys. Chem. Chem. Phys. 3, p. 3838-3845
(2001).
5. G.I.N. Waterhouse, G.A. Bowmaker, J.B. Metson,
Mechanism and active sites for the partial oxidation
of methanol to formaldehyde over an electrolytic
silver catalyst // Applied Catalysis A: General, 265,
p. 85-101 (2004).
6. R. Liping, D. Weilin, Y. Xinli, C. Yong, X. Zaiku,
F. Kangnian, Transformation of various oxygen
species on the surface of electrolytic silver
characterized by in situ Raman spectroscopy //
Chin. J. Catal. 27(2), p. 115-118 (2006).
7. Z. Zhao, M.A. Carpenter, Support-free bimodal
distribution of plasmonically active Ag/AgOx
nanoparticle catalysts: attributes and plasmon
enhanced surface chemistry // J. Phys. Chem. C,
117(21), p. 11124-11132 (2013).
8. Z. Pan, A. Zabalin, A. Veda, M. Guo, M. Groza,
A. Burger, R. Mu, S.H. Morgan, Surface-enhanced
Raman spectroscopy using silver-coated porous
glass-ceramic substrates // Applied Spectroscopy,
59(6), p. 782-786 (2005).
9. S. Chan, S. Kwon, T-W. Koo, L.P. Lee, A.A. Berlin,
Surface-enhanced Raman scattering of small
molecules from silver-coated silicon nanopores //
Adv. Mater. 75(19), p. 1595-1598 (2003).
10. S.N. Terekhov, P. Mojzes, S.M. Kachan et al.,
A comparative study of surface-enhanced Raman
scattering from silver-coated anodic aluminum
oxide and porous silicon // Raman Spectroscopy,
42, p. 12-20 (2011).
11. K. Grytsenko, Yu. Kolomzarov, O. Lytvyn,
T. Doroshenko, V. Strelchuk, SERS of dye film
deposited onto gold nano-clusters // Semiconductor
Physics, Quantum Electronics & Optoelectronics,
13(2), p. 151-153 (2010).
12. L.H. Qian, X.Q. Yan, T. Fujita et al., Surface
enhanced Raman scattering of nanoporous gold:
Smaller pore sizes stronger enhancements // Appl.
Phys. Lett. 90, p. 153120 (1-3) (2007).
13. C.A. Smyth, I. Mirza, J.G. Junney, E.M. Mc Cabe,
Surface-enhanced Raman spectroscopy (SERS)
using Ag nanoparticle films produced by pulsed
laser deposition // Appl. Surf. Sci. 264, p. 31-35
(2013).
14. E.B. Kaganovich, S.A. Kravchenko,
L.S. Maksimenko et al., Polarization properties of
porous gold and silver films // Optics and
Spectroscopy, 110(4), p. 513-521 (2011).
15. E.G. Manoilov, Optical and photoluminescence
properties of Ag/Al2O3 nanocomposite films
obtained by pulsed laser deposition // Semicon-
ductor Physics, Quantum Electronics & Opto-
electronics, 12(2) p. 298-301 (2009).
16. E.B. Kaganovich, I.M. Krishchenko, E.G. Manoilov,
N.P. Maslak-Gudyma, V.V. Kremenitskiy, Structure
and optical properties of gold and silver porous films
obtained by pulsed laser deposition in vacuum //
Nanosystems, Nanomaterials, Nanotechnologies,
10(4), p. 859-868 (2012).
17. A.D. Mc Farland, R.P. Van Duyne, Single silver
nanoparticles as real-time optical sensors with
zeptomole sensitivity // NanoLett. 3(8), p. 1057
(2003).
18. S. Hayashi, R. Koga, M. Ohtuji, K. Yamamoto, and
M. Fujii, Surface plasmon resonances in gas-
evaporated Ag small particles: Effects of
aggregation // Solid State Communs. 76, p. 1067
(1990).
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