Design and characterization of nanostructured SERS substrates based on gold nanostars
Using the method of chemical synthesis, effective SERS substrates were developed, which were the films of gold nanoparticles in the form of stars. The peculiarity of star-shaped nanoparticles is that they could enhance the electric field of the radiating dipole not only by setting the frequency of t...
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Інститут фізики напівпровідників імені В.Є. Лашкарьова НАН України
2017
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| Cite this: | Design and characterization of nanostructured SERS substrates based on gold nanostars / V.O. Yukhymchuk, O.M. Hreshchuk, M.Ya. Valakh, Ye.G. Gule, M.A. Skoryk, V.S. Efanov, N.A. Matveevskaya, T.G. Beynik // Semiconductor Physics Quantum Electronics & Optoelectronics. — 2017. — Т. 20, № 1. — С. 41-47. — Бібліогр.: 22 назв. — англ. |
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| author | Yukhymchuk, V.O. Hreshchuk, O.M. Valakh, M.Ya. Gule, Ye.G. Skoryk, M.A. Efanov, V.S. Matveevskaya, N.A. Beynik, T.G. |
| author_facet | Yukhymchuk, V.O. Hreshchuk, O.M. Valakh, M.Ya. Gule, Ye.G. Skoryk, M.A. Efanov, V.S. Matveevskaya, N.A. Beynik, T.G. |
| citation_txt | Design and characterization of nanostructured SERS substrates based on gold nanostars / V.O. Yukhymchuk, O.M. Hreshchuk, M.Ya. Valakh, Ye.G. Gule, M.A. Skoryk, V.S. Efanov, N.A. Matveevskaya, T.G. Beynik // Semiconductor Physics Quantum Electronics & Optoelectronics. — 2017. — Т. 20, № 1. — С. 41-47. — Бібліогр.: 22 назв. — англ. |
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| container_title | Semiconductor Physics Quantum Electronics & Optoelectronics |
| description | Using the method of chemical synthesis, effective SERS substrates were developed, which were the films of gold nanoparticles in the form of stars. The peculiarity of star-shaped nanoparticles is that they could enhance the electric field of the radiating dipole not only by setting the frequency of the plasmon absorption band at the frequency of the exciting laser radiation, but additionally due to a significant contribution to Raman scattering of the so-called “hot spots” that exist at the edges of the stars. “Nanostar”-based films were prepared using both direct deposition of gold nanoparticles from colloidal solution on the glass substrate and on the layer of polycation of polydiallyldimethyl ammonium bromide on the surface of glass substrates. Surface morphology of the obtained films was investigated using scanning electron microscopy. Plasmon absorption spectra were obtained using the method of optical absorption. Variation of geometrical parameters inherent to these nanostructures allows configuring the position of the plasmonic absorption band maximum close to the laser excitation wavelength. The coefficient of enhancement of the Raman signal was evaluated for Rhodamine 6G molecules deposited on the designed SERS substrates (for different wavelengths of the exciting laser radiation, namely: λ = 633, 532, and 457 nm).
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Semiconductor Physics, Quantum Electronics & Optoelectronics, 2017. V. 20, N 1. P. 41-47.
doi: https://doi.org/10.15407/spqeo20.01.041
© 2017, V. Lashkaryov Institute of Semiconductor Physics, National Academy of Sciences of Ukraine
41
PACS 78.30.Ly, 78.67.Bf, 81.07.-b, 81.16.-c
Design and characterization of nanostructured SERS substrates
based on gold nanostars
V.O. Yukhymchuk1, O.M. Hreshchuk1*, M.Ya. Valakh1, Ye.G. Gule1, M.A. Skoryk2, V.S. Efanov1, 2,
N.A. Matveevskaya3, T.G. Beynik3
1V. Lashkaryov Institute of Semiconductor Physics, NAS of Ukraine;
45, prospect Nauky, 03680 Kyiv, Ukraine
2Nanomedtech LLC, 68, Antonovych str., 03680 Kyiv, Ukraine
3State Scientific Institution “Institute for Single Crystals”, NAS of Ukraine
60, prospect Nauky, 61178 Kharkiv, Ukraine
*E-mail: Hreshchuk@gmail.com
Abstract. Using the method of chemical synthesis, effective SERS substrates were
developed, which were the films of gold nanoparticles possessing the form of stars. The
peculiarity of star-shaped nanoparticles is that they could enhance the electric field of the
radiating dipole not only by setting the frequency of the plasmon absorption band at the
frequency of the exciting laser radiation, but additionally due to significant contribution
to Raman scattering of the so-called “hot spots” that exist at the edges of the stars.
“Nanostar”-based films were prepared using both direct deposition of gold nanoparticles
from colloidal solution on the glass substrate and on the layer of polycation of
polydiallyldimethyl ammonium bromide on the surface of glass substrates. Surface
morphology of the obtained films was investigated using scanning electron microscopy.
Plasmon absorption spectra were obtained using the method of optical absorption.
Variation of geometrical parameters inherent to these nanostructures allows configuring
the position of the plasmonic absorption band maximum close to the laser excitation
wavelength. The coefficient of enhancement of Raman signal was evaluated for
Rhodamine 6G molecules deposited on the designed SERS substrates (for different
wavelengths of the exciting laser radiation, namely: λ = 633, 532 and 457 nm).
Keywords: SERS, SEM, Raman scattering, absorption spectra, gold nanoparticles,
“nanostars”.
Manuscript received 03.11.16; revised version received 07.02.17; accepted for
publication 01.03.17; published online 05.04.17.
1. Introduction
Surface-enhanced Raman spectroscopy (SERS) is an
efficient analytical method that is intensively
developing, and every year it finds more commonly
usage in diagnostics of substances in chemistry,
materials science, medicine, biology, pharmacology,
ecology etc. [1-5]. SERS allows performing the analysis
of substances available in low concentrations in
solutions or deposited in the amount of one monolayer
on nanostructured metal substrate. The SERS method is
a non-destructive express method like typical Raman
spectroscopy that allows identifying the component
composition of substances, the features of their
molecular structure and so on.
The theoretical and experimental studies show that
the effect of SERS enhancement is based on two
mechanisms: chemical and electromagnetic [1, 2]. The
first mechanism is associated with collective electron
oscillations (surface plasmons) in metallic
Semiconductor Physics, Quantum Electronics & Optoelectronics, 2017. V. 20, N 1. P. 41-47.
doi: https://doi.org/10.15407/spqeo20.01.041
© 2017, V. Lashkaryov Institute of Semiconductor Physics, National Academy of Sciences of Ukraine
42
nanostructures that create an electromagnetic field near
the surface, which enhances the Raman scattering from
molecules or semiconductor nanostructures deposited on
the SERS substrate. The second mechanism is associated
with formation of chemical bonds between the studied
molecules and metal nanostructures, which provides a
resonant energy exchange between them under laser
excitation. The efficiency of SERS effect depends on
morphology of nanostructured metal surface [6], the
parameters of the exciting laser radiation [7], the
conditions of deposition and properties of the substance
[8] as well as on the distance of the latter from the
surface of SERS substrate [9], etc.
It’s necessary to have substrates covered with films
of nanostructured gold or silver for effective application
of SERS substrates for routine laboratory usage.
Enhancing “platforms” should be characterized by such
parameters as stability in time, lateral uniformity, simple
and low cost fabrication, and significant enhancement of
the Raman signal for a wide range of substances (from
chemical and biological to semiconductor nanoclusters).
It is known that using the methods of colloidal
synthesis various nanostructures could be synthesized,
which are suitable for SERS substrates, for instance:
core-shell [10] nanostructures, nanoparticles (NPs) with
different shapes: spherical, triangles, cubes, wires and
others [11]. Nanostructures in the form of stars could be
the new type of efficient substrates for the SERS
diagnostics [12]. On the one hand, this geometrical form
of nanostructures causes the concentration of electrical
fields at the edges of nanostars (NSTs), moreover, it
enhances the electric field of radiating dipole not only by
fitting the frequency of plasmon absorption band to the
frequency of the exciting laser radiation, but also due to
the presence of the so-called “hot spots” in the radiating
system. The latter one is a superposition of electrical
fields created by few closely placed metal
nanostructures. Typically, the hot spots are not evenly
placed on the surface of SERS substrate, and the area
covered by them does not exceed 1% of the total area
[13]. However, in [13] it was shown that even such a
low percent of hot spots could make its contribution to
total SERS enhancement higher than 24%. That is why it
is so important for nanostructures of SERS substrates to
form hot spots.
It should be noted that gold NSTs could be used as
biomarkers for address delivery of drugs in the human
body or in detection of malignant tumors, etc [14]. In
[15], it was shown that the intensity of SERS signal from
molecules adsorbed on the surface of metal
nanoparticles is by 1-2 orders of magnitude higher than
the intensity of quantum dots (QDs) radiation.
Moreover, in contrast to QDs, the SERS based
biomarkers does not have such properties as
photobleaching and gradual self-quenching of emitted
radiation.
The aim of this work was to develop a method of
synthesis of nanostructures in the form of stars for
efficient SERS substrates, to investigate their properties,
establish the relationship between the morphology and
plasmonic absorption band and to determine the
coefficient of enhancement of the Raman signal from
analyte deposited on them.
2. The method of synthesis of nanostructures
The following chemical components were used for
synthesis of gold NSTs and forming of films based on
them: gold hydrochloric acid HAuCl4·3H2O ≥ 99.9%,
sodium citrate Na3C6H5O7 ≥ 98%, hydrochloric acid
HCl ≥ 99%, silver nitrate AgNO3 ≥ 99.8%, ascorbic acid
C6H8O6 ≥ 99%, 3-aminopropyl-triethoxysilane (APTES)
C9H23NO3Si ≥ 98%, sulfuric acid H2SO4 ≥ 98%,
hydrogen peroxide H2O2 ≥ 30%, poly (dyallildymetyl)
ammonium bromide (PDADMAD) (C8H16ClN)n (20%
aqueous solution) without further purification.
The two-stage method of chemical synthesis was
chosen to obtain aqueous solutions with colloidal gold
NSTs, which allowed to control the size and shape of the
obtained nanoparticles (NPs). At the first stage of
synthesis, the spherical gold NPs were obtained with an
average size close to 12 nm. The solution of spherical
gold NPs was obtained by addition of 1.5 ml of 1%
solution of sodium citrate to 10 ml of 0.001 M of boiling
solution of HAuCl4 and stirring. The solution was boiled
for 15 min maintaining a constant volume, and then this
solution was cooled in air. The obtained spherical gold
NPs served as seeds for controlled growing the bulk
nanostructures in the form of stars.
Gold cones with sharp peaks (the edges of the stars)
were grown during the second stage of synthesis on the
surface of the spherical gold NPs. This process was held
due to the recovery of gold hydrochloric acid by ascorbic
acid on the surface of Au NPs, in the presence of silver
ions in solution. In order to obtain the gold nanostars,
0.1 ml of the spherical Au seeds was added to 10 ml of
2.5·10–4 M of HAuCl4 solution at pH = 3, the solution
being under intense stirring. Then 0.002 ml of 0.05 M of
AgNO3 solution and 0.5 ml of 0.01 M solution of ascorbic
acid were quickly added. After adding ascorbic acid, the
color of the solution drastically changed to blue,
indicating the formation of Au NSTs.
The presence of silver ions in the solution was a
prerequisite for formation of gold NPs of non-spherical
shape, namely: creation and growth of sharp edges in
NSTs along certain crystallographic facets of gold NPs.
Silver is adsorbed on the facets of the gold NPs with the
largest surface energy, thus forming there monolayers or
submonolayers of Ag [16]. This leads to selective
stabilization of the facets of {110}, {310} and {720} of
the gold NPs [17] and prevents the further growth of Au
along these facets. Accordingly, further growth of gold
NPs is anisotropic, and the growth is on the facets that
have a lower surface energy. In particular, after
stabilization of the facets {110} adsorption of Au occurs
on the facets {111}, resulting in formation of gold in the
form of cones along this direction.
Films with gold NSTs were obtained using the self-
Semiconductor Physics, Quantum Electronics & Optoelectronics, 2017. V. 20, N 1. P. 41-47.
doi: https://doi.org/10.15407/spqeo20.01.041
© 2017, V. Lashkaryov Institute of Semiconductor Physics, National Academy of Sciences of Ukraine
43
assembly method [18, 19] on the glass substrates with
the size 1×1 cm. The substrates were kept in the solution
of H2SO4:H2O2 (10:1) during 10 hours to remove
adsorbed contaminants, then repeatedly washed with
bidistilled water by using ultrasound. Surface
modification of substrates was performed using the 5%
alcohol solution of APTES when boiling for 1.5 hours.
The modified substrates were repeatedly washed with
alcohol and water by using ultrasound to remove the
excess of APTES.
Formation of the films with star-like nanostructures
on the glass substrate was carried out in two ways. In
order to obtain a multilayer film, the substrates were
placed in colloidal solution of Au NSTs, and then in
PDADMAB with the concentration 2 mg/ml,
M ~ 100,000–200,000. Substrates were kept in the
solution of NSTs overnight at 20 °C, then rinsed with
bidistilled water and placed in solution of polycations for
20 min (SERS substrate of type I). Another way to form
SERS substrates was in direct deposition of the colloidal
solution of the gold NSTs on the cleaned glass substrate
by drop-drying method in air (SERS substrate of the
II type).
3. Experimental methods
Morphology and structure of the SERS substrates with
Au NPs, synthesized using the above mentioned
methods, were examined with the scanning electron
microscope (SEM) Tescan Mira 3 LMU, transmission
electron microscope (TEM) TEM-125 with an
accelerating voltage of 100 kV, by high resolution TEM
Jeol JSM-820 equiped with X-ray microanalysis system
LINK IN 10000. Samples for TEM measurements were
prepared by the standard method, namely, by deposition
of aqueous suspensions of NPs onto the copper
substrates coated with a thin layer of carbon, followed
by drying at room temperature.
The elemental composition of substrates with gold
NPs were examined by X-ray photoelectron
spectroscopy (XPS) MXPS XP (Omicron) equipped with
hemispherical electrostatic analyzer, photoelectrons
were excited by Mg Kα-radiation (hγ = 1253.6 eV). The
energy scale was calibrated using the line S1s
(Eb = 285 eV). The resolution of spectrometer was
1.0 eV, accuracy of determining the binding energy was
0.2 eV. The composition of the samples was determined
by the surface area ratio for the bands C1s, O1s, Au4f,
Si2p, Cl2p, and N1s of valence electron shells with
account of the sensitivity coefficients. The thickness of
the analyzed layer was ∼5 nm.
The absorption spectra of obtained nanostructures
were recorded using the double-beam spectrophotometer
UV-VIS-IR Shimadzu UV-3600. Raman studies were
performed at room temperature by using a spectrometer
with monochromator equipped with CCD camera of
Andor company. Solid-state lasers with the wavelengths
of 532 and 457 nm and He-Ne+-laser with the
wavelength 632.8 nm were used to excite the Raman
scattering. The solution of Rhodamine 6G (R6G) in
bidistilled water was used as analyte with concentrations
10–3 and 10–5 M. The solution of R6G was deposited on
substrates by dispenser in the same amount of substance
(5⋅10–6 l) at approximately the same area, and then dried
in air to obtain the thin film of analyte molecules on the
surface of SERS substrates. To prevent damage of the
structure of the investigated molecules, Raman spectra
were excited by laser radiation with a minimally
sufficient power to ensure their registration. To verify
the homogeneity of the SERS substrates several points
on each sample were examined and the time of
accumulation of the signal was the same for all
measurements.
4. Results and discussion
Scanning (SEM) and transmission (TEM) electron
microscopy were used to characterize morphology of the
studied nanostructures. The results are shown in Fig. 1.
The figure shows that the synthesized nanostructures
have the form of stars with sharp edges. The length of the
edges (cones) ranges from 10 to 25 nm, the thickness at
their base is ~10 nm, and at the end of the tip it is ≤4 nm.
Nanostars have almost the same lateral dimensions
≤55 nm, and their size dispersion is 13%. SEM images
(Fig. 1b, c, d) show that the emplacement of the NSTs is
quite tight, which causes formation of the so-called hot
spots, where the value of the electric fields is significantly
larger than the average value of electric field on the
surface of SERS substrate.
The characteristic reflections of corresponding
planes of (111) (200) (220) (311) obtained by electronic
microdiffraction are indicative of a crystalline and face-
centered cubic structure of the obtained gold NPs in the
form of stars (Fig. 2).
The elemental composition of obtained gold NSTs
was investigated using X-ray photoelectron spectroscopy
(XPS). The obtained spectra of Au4f and Ag3d shells
from the surface of the samples are shown in Fig. 3. It
was ascertained that the energy of the line Au4f7/2 for all
the samples equals to 84.0 ± 0.2 eV, and it corresponds
to the metallic state of the gold. Since the silver line
doesn’t have a pronounced chemical shift, namely, for
the most of the silver compounds the binding energy of
Ag3d does not differ more than by the value 0.2 eV as
compared to the binding energy of metallic silver
(368.1 eV) [17]. Therefore, it is impossible to
unambiguously identify the chemical state of the silver
from XPS spectra (Fig. 3). However, since there were
not observed any lines from chlorine (HAuCl4 and HCl)
in the spectra of the samples, and formation of silver
oxide in the process of synthesis was impossible (from
the chemical viewpoint), it could be assumed that silver
could be found in the metallic state for all the samples
with gold NSTs.
Semiconductor Physics, Quantum Electronics & Optoelectronics, 2017. V. 20, N 1. P. 41-47.
doi: https://doi.org/10.15407/spqeo20.01.041
© 2017, V. Lashkaryov Institute of Semiconductor Physics, National Academy of Sciences of Ukraine
44
Fig. 1. TEM (а) and SEM (b, c, d) images of the gold nanostructures in the form of bulk “stars”.
As noted above, the efficiency of enhancement of
Raman signal by SERS substrates increases
significantly, when the frequency of the exciting laser
radiation matches or is close to the frequency inherent to
the plasmon absorption band of the metal (typically
silver, gold). Considering that the wavelengths of laser
radiation used in Raman spectroscopy have fixed values,
it is more appropriate to adjust the parameters of SERS
substrates (shape, size and surface density of
nanostructures to the resonance with laser radiation. So,
one of the important characteristics of the SERS
substrates is their absorption spectra, since the position
of the peak and halfwidth of the plasmonic absorption
band determine the spectral range in which the
significant enhancement of the Raman signal is possible,
if the appropriate excitation laser is chosen.
Fig. 4 shows the absorption spectrum of the studied
SERS substrates obtained by the first method, namely,
by formation of 3 monolayers of NSTs in PDADMAB
matrix on a glass substrate. The absorption spectrum of
SERS substrates formed by deposition of gold NPs from
colloidal solution coincides with the mentioned above.
As shown in Fig. 4, the maximum of plasmon absorption
band was in 600 nm region for these substrates. The
plasmonic absorption band is quite wide, and its
halfwidth approximately equals to 174 nm, which is
caused by diversity in the sizes of spherical cores in
NSTs and their edges.
The great halfwidth of the plasmonic absorption
band of obtained nanostructuresNS allows to use several
lasers with different wavelengths of radiation to excite
surface plasmon oscillations. Indeed, as Fig. 4 shows,
lasers with the wavelengths of radiation 532 and
632.8 nm are close enough to the maximum of the
plasmon absorption band. Investigations that involved
usage of the laser with the wavelength 457 nm (which
does not match with the plasmon absorption band) were
performed to estimate the contributions of the
electromagnetic and chemical component to the
enhancement of the Raman signal.
Fig. 2. Picture of electron microdiffraction of the gold
nanostars.
Semiconductor Physics, Quantum Electronics & Optoelectronics, 2017. V. 20, N 1. P. 41-47.
doi: https://doi.org/10.15407/spqeo20.01.041
© 2017, V. Lashkaryov Institute of Semiconductor Physics, National Academy of Sciences of Ukraine
45
Fig. 3. Photoelectron X-ray spectra of Au4f and Ag3d shells from the surface of nanostars.
To correctly estimate the enhancement of the
Raman signal by SERS substrates, the same volume of
the R6G solution was deposited on substrates, and it
was sputtered approximately on the same surface area,
the concentration of R6G was of the order of 10–3 and
10–5 M. The choice of the concentration of R6G
molecules in the solution of the order of 10–3 M was
caused by the fact that this value was minimal (in this
case) sufficient for registration of the Raman signal
from R6G molecules deposited on a glass substrate
(without gold nanostructures).
The SERS enhancement factor was determined
using the formula [21]:
( ) ( )RSRSSERSSERS NINIk = , (1)
where ISERS, IRS are the intensities of SERS and
conventional Raman signal, NSERS, NRS are the numbers
of investigated molecules that contribute to SERS and
usual Raman scattering.
In all the cases, calculation of the enhancement
factor was carried out using the intensity of the Raman
band (612 cm–1) corresponding to R6G molecules, which
is caused by C–C bending vibrations of the benzene ring
[19]. The choice of this Raman band to determine the
enhancement factor of SERS substrates was made due to
high intensity of it and its far position relatively to the
peak of photoluminescence band of R6G molecules,
when it was excited by laser radiation.
Experiments have shown that the intensity of ISERS
changes non-linearly with the concentration of the
solution of R6G molecules deposited onto the SERS
substrate. Indeed, ISERS depends on the number of
investigated molecules that are in the vicinity of
0.1–1 nm to metallic nanostructures in the place of laser
excitation spot. Calculations showed that in this case the
solution of R6G molecules with volume of 5⋅10–6 l and
concentration of 10–5 M deposited on substrate cover the
area of 3⋅1013 nm2, thus forming one monolayer of
molecules. Increasing the concentration by one order, it
will form a film with the thickness 10 monolayers. But
in this case, the main contribution to the intensity of
Raman band will be provided by the first layer, which is
located directly on metal nanostructures. The
contribution of the next layer will be several times
smaller and so on; this is caused by exponential decrease
of the electric field withdrawing from NP surface.
Consequently, it is clear, why in the certain
concentration range of solutions further increasing the
concentration by one order leads to the increase of ISERS
by 1.5-2 times.
500 600 700 800 900 1000 1100 1200
457 nm
A
bs
or
pt
io
n,
a
rb
. u
ni
ts
Wavelength, nm
632 nm
532 nm
Fig. 4. The absorption spectrum of SERS substrate based on
gold nanostars (I type). The arrows show the position of
wavelengths for laser excitation used in SERS experiments.
Semiconductor Physics, Quantum Electronics & Optoelectronics, 2017. V. 20, N 1. P. 41-47.
doi: https://doi.org/10.15407/spqeo20.01.041
© 2017, V. Lashkaryov Institute of Semiconductor Physics, National Academy of Sciences of Ukraine
46
600 800 1000 1200 1400 1600
In
te
ns
ity
, a
rb
. u
n.
Raman shift, cm-1
1
2
612
Fig. 5. Raman spectra of R6G molecules deposited on the glass
substrate (1) with the concentration of solution 10–3 M and on
the SERS substrate (II type) (2) with the concentration of the
solution 10–5 M. Spectra were obtained using laser excitation
with λ = 532 nm.
Fig. 5 shows the Raman spectra of Rhodamine 6G
molecules deposited on the glass (1) and SERS (II type)
(2) substrates obtained using excitation with the
wavelength 532 nm. It should be noted that R6G
molecules were deposited on the glass substrates from the
solution with the concentration 10–3 M, and on the SERS
substrate – with the concentration 10–5 M. Taking into
account that the intensity of the bands in the spectrum 2 is
higher by 2 orders of magnitude as compared to the
spectrum 1, estimation of the enhancement factor (k)
according to the formula (1) gives the value of 104. The
coefficient of enhancement could be significantly higher
in the case when the wavelength of the laser excitation
radiation coincidences with the wavelength of the
plasmon absorption band peak.
The efficiency of enhancement of the Raman signal
of R6G molecules on the SERS substrate (I type), where
gold nanostars are placed in the PDADMAB matrix is
significantly lower (102 times). The coefficient of
enhancement of the Raman signal, using the laser
excitation radiation with the wavelength 632.8 nm, is 1.5
times higher as compared to that for λ = 532 nm. The
latter fact is caused by the proximity of the laser light
with the wavelength 632.8 nm to the maximum of
plasmon absorption band (602 nm, see. Fig. 2). The
decrease of the enhancement by 2 orders of magnitude,
as compared to that for the substrate of the first type, is
caused by the fact that the gold nanostars are placed in
the PDADMAB matrix. On the one hand, it reduces the
enhancement due to absence of chemical bonds between
the Rhodamine molecules and gold nanoparticles, on the
other hand, it reduces the number of hot spots that
contribute to enhancement. A partial confirmation of this
conclusion could be obtained from the experiment
performed with laser radiation of λ = 457 nm for
excitation of the Raman spectra for SERS substrates.
With this radiation, the intensity of the Raman signal of
R6G molecules was only 2 times higher as compared to
the Raman signal from R6G molecules on a glass
substrate. The absence of significant enhancement of the
Raman signal in SERS substrates of I type can testify
about the absence of the chemical bonds between the
studied molecules and gold nanostructures.
5. Conclusions
The efficient SERS substrates based on films of
nanoparticles in the form of stars were developed and
investigated. This star-shaped nanostructure enhances
the electrical field of radiating dipole not only by setting
the frequency of the plasmon absorption band to the
frequency of the laser excitation, but also by increasing
the number of the so-called hot spots on the surface of
substrate. It was shown that these nanostructures
efficiently enhance the Raman signal when using laser
excitation with the wavelengths 532 and 632.8 nm,
which is close to the wavelength of the maximum of
plasmon absorption band. For structures that were
deposited directly from the colloidal solution, the
chemical enhancement is characteristic, because of direct
contact of adsorbed molecules with gold nanoparticles.
Analysis of the Raman spectra of R6G molecules,
deposited on manufactured SERS substrates showed that
they enhance Raman signal by 4 orders.
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| id | nasplib_isofts_kiev_ua-123456789-214914 |
| institution | Digital Library of Periodicals of National Academy of Sciences of Ukraine |
| issn | 1560-8034 |
| language | English |
| last_indexed | 2026-03-21T14:44:23Z |
| publishDate | 2017 |
| publisher | Інститут фізики напівпровідників імені В.Є. Лашкарьова НАН України |
| record_format | dspace |
| spelling | Yukhymchuk, V.O. Hreshchuk, O.M. Valakh, M.Ya. Gule, Ye.G. Skoryk, M.A. Efanov, V.S. Matveevskaya, N.A. Beynik, T.G. 2026-03-03T11:09:32Z 2017 Design and characterization of nanostructured SERS substrates based on gold nanostars / V.O. Yukhymchuk, O.M. Hreshchuk, M.Ya. Valakh, Ye.G. Gule, M.A. Skoryk, V.S. Efanov, N.A. Matveevskaya, T.G. Beynik // Semiconductor Physics Quantum Electronics & Optoelectronics. — 2017. — Т. 20, № 1. — С. 41-47. — Бібліогр.: 22 назв. — англ. 1560-8034 PACS: 78.30.Ly, 78.67.Bf, 81.07.-b, 81.16.-c https://nasplib.isofts.kiev.ua/handle/123456789/214914 https://doi.org/10.15407/spqeo20.01.041 Using the method of chemical synthesis, effective SERS substrates were developed, which were the films of gold nanoparticles in the form of stars. The peculiarity of star-shaped nanoparticles is that they could enhance the electric field of the radiating dipole not only by setting the frequency of the plasmon absorption band at the frequency of the exciting laser radiation, but additionally due to a significant contribution to Raman scattering of the so-called “hot spots” that exist at the edges of the stars. “Nanostar”-based films were prepared using both direct deposition of gold nanoparticles from colloidal solution on the glass substrate and on the layer of polycation of polydiallyldimethyl ammonium bromide on the surface of glass substrates. Surface morphology of the obtained films was investigated using scanning electron microscopy. Plasmon absorption spectra were obtained using the method of optical absorption. Variation of geometrical parameters inherent to these nanostructures allows configuring the position of the plasmonic absorption band maximum close to the laser excitation wavelength. The coefficient of enhancement of the Raman signal was evaluated for Rhodamine 6G molecules deposited on the designed SERS substrates (for different wavelengths of the exciting laser radiation, namely: λ = 633, 532, and 457 nm). en Інститут фізики напівпровідників імені В.Є. Лашкарьова НАН України Semiconductor Physics Quantum Electronics & Optoelectronics Design and characterization of nanostructured SERS substrates based on gold nanostars Article published earlier |
| spellingShingle | Design and characterization of nanostructured SERS substrates based on gold nanostars Yukhymchuk, V.O. Hreshchuk, O.M. Valakh, M.Ya. Gule, Ye.G. Skoryk, M.A. Efanov, V.S. Matveevskaya, N.A. Beynik, T.G. |
| title | Design and characterization of nanostructured SERS substrates based on gold nanostars |
| title_full | Design and characterization of nanostructured SERS substrates based on gold nanostars |
| title_fullStr | Design and characterization of nanostructured SERS substrates based on gold nanostars |
| title_full_unstemmed | Design and characterization of nanostructured SERS substrates based on gold nanostars |
| title_short | Design and characterization of nanostructured SERS substrates based on gold nanostars |
| title_sort | design and characterization of nanostructured sers substrates based on gold nanostars |
| url | https://nasplib.isofts.kiev.ua/handle/123456789/214914 |
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