Substrate Temperature Effect on Microstructure, Optical, and Glucose Sensing Characteristics of Pulsed Laser Deposited Silver Nanoparticles

Abstract

This work reports the substrate temperature-influenced change in the structural, morphological, optical, and glucose sensing properties of silver (Ag) nanoparticles (NPs) deposited on p-type Si (100) wafers. AgNP films grown at temperatures ranging from RT to 600 °C clearly show a dependence of orientation texture and surface morphology on substrate temperature (Ts). As Ts increases from RT towards 600 °C, the preferred orientation of AgNP film changes from (111) to (200). The AgNPs size, that is Ts-dependent, reaches the maximum value at Ts = 300 °C. This result is attributed to restructuring of AgNPs texture. Moreover, the AgNP shape also changes from ellipsoid to sphere as Ts increases from RT to 600 °C. Surface plasmon enhancement in photoluminescence intensity is observed with increase in Ts. It is found also that the AgNP film deposited at 300 °C has considerable reflectance reduction relative to the silicon substrate, in wavelength range of 300–800 nm and a progressive red shift of localized surface plasmon resonances caused by the adding of increasing quantities of glucose has been observed. As a proof of concept, we also demonstrate the capability of grown AgNP substrates for glucose detection based on surface enhanced Raman spectroscopy in physiological concentration range with short integration time 10 s, varying with Ts.

Full text

Substrate Temperature Effect on Microstructure, Optical,
and Glucose Sensing Characteristics of Pulsed Laser Deposited
Silver Nanoparticles
Koppole Kamakshi
1,2,3
&J. P. B. Silva
1,2
&K. C. Sekhar
4
&J. Agostinho Moreira
2
&
A. Almeida
2
&M. Pereira
1
&M. J. M. Gomes
1
Received: 13 February 2017 /Accepted: 12 June 2017
#Springer Science+Business Media, LLC 2017
Abstract This work reports the substrate temperature-
influenced change in the structural, morphological, optical,
and glucose sensing properties of silver (Ag) nanoparticles
(NPs) deposited on p-type Si (100) wafers. AgNP films grown
at temperatures ranging from RT to 600 °C clearly show a
dependence of orientation texture and surface morphology on
substrate temperature (T
s
). As T
s
increases from RT towards
600 °C, the preferred orientation of AgNP film changes from
(111) to (200). The AgNPs size, that is T
s
-dependent, reaches
the maximum value at T
s
= 300 °C. This result is attributed to
restructuring of AgNPs texture. Moreover, the AgNP shape
also changes from ellipsoid to sphere as T
s
increases from RT
to 600 °C. Surface plasmon enhancement in
photoluminescence intensity is observed with increase in T
s
.It
is found also that the AgNP film deposited at 300 °C has con-
siderable reflectance reduction relative to the silicon substrate,
in wavelength range of 300–800 nm and a progressive red shift
of localized surface plasmon resonances caused by the adding
of increasing quantities of glucose has been observed. As a
proof of concept, we also demonstrate the capability of grown
AgNP substrates for glucose detection based on surface en-
hanced Raman spectroscopy in physiological concentration
range with short integration time 10 s, varying with T
s
.
Keywords Surface plasmon resonance .AgNP thin film .
Glucose sensing
Introduction
Plasmonic nanostructures have been widely investigated due
to their potential applications in photovoltaic devices and sen-
sors [1–4]. In general, the efficiency of the photovoltaic de-
vices made fromsilicon (Si) decreases seriously due to its high
reflectivity to the visible and near infrared light. In order to
overcome the intrinsic disadvantage of silicon, a new method
has currently emerged by the use of light scattering from noble
metal nanoparticles (NPs), excited at their surface plasmon
resonance (SPR). The SPR wavelength of the metal NPs can
be tuned throughout a broad spectral range by adjusting their
size and shape, surface distribution density, and the surround-
ing dielectric environment [5–7]. The fine tuning of the SPR
wavelength makes the plasmonic nanostructures very attrac-
tive for various applications [5–8], including biosensors and
photovoltaic devices [9–11]. In particular, silver (Ag) and gold
(Au) NPs, with their associated strong SPR, have generated
great interest in developing glucose biosensors, silicon-based
solar cells, and photo-detectors [1,4,5]. In fact, glucose bio-
sensors account for 85% of the entire biosensor market, due to
the huge population of diabetics [12]. However, Raman de-
tection of glucose at physiological concentrations requires
both high laser power and long acquisition time (typically
250 mW and 5 min, respectively), which is not practical for
*Koppole Kamakshi
kamakshikoppole@gmail.com
*K. C. Sekhar
sekhar.koppole@gmail.com
1
Centre of Physics, University of Minho, Campus de Gualtar,
4710-057 Braga, Portugal
2
IFIMUP and IN-Institute of Nanoscience and Nanotechnology,
Departamento de Física e Astronomia, Faculdade de Ciênciasda
Universidade do Porto, Rua do Campo Alegre 687,
4169-007 Porto, Portugal
3
Department of Physics, Madanapalle Institute of Technology &
Science, Madanapalle, Andhra Pradesh, India
4
Department of Physics, Central University of Tamil Nadu,
Thiruvarur 610 101, India
Plasmonics
DOI 10.1007/s11468-017-0625-y

clinical purposes. This problem can be overcome by using
AgNP surfaces to enhance the glucose signal via surface-
enhanced Raman scattering (SERS).
The present work emphasizes the use of SPR associated
with AgNPs, to reduce the reflectivity in the visible region
and also for glucose sensing. Further, the SPR (in the visible
spectral range) wavelength and photoluminescence characteris-
tics of AgNP’s films grown on Si substrate are tuned through
the micro structural variations induced by substrate temperature
(T
s
). The performance of the as-deposited AgNP’s films to de-
tect glucose by Raman spectroscopy with a low laser power of
about 16 mW and acquisition time 10 s is also assessed.
Experiment
A thin layer of AgNPs was prepared on p-type Si (100) wafers by
the pulsed laser deposition (PLD) using commercially available
Ag target (99.99% purity) in presence of vacuum of 1 × 10
−7
mbar.
An excimer laser of wavelength 248 nm, with energy of 400 mJ
and pulse rate of 10 Hz, was focused onto the target. Silicon
substrates were placed at a distance of 10 cm directly in front of
the target. Silver thin films were grown at different temperatures
(T
s
) in the range of room temperature (RT) to 600 °C in high
vacuum. The number of laser shots was fixed at 12,000.
The grown AgNP films were structurally characterized
using a Philips X-ray diffractometer (model PW1710), with
CuK
α
radiation (λ= 0.154 nm). Surface morphology of Ag
films was studied by scanning electron microscopy (SEM)
using a FEI Quanta 400FEG ESEM/EDAX Genesis X4M.
The reflectance spectra of Ag films were recorded using a
Shimadzu (Model UV/2501PC) spectrometer.
Photoluminescence (PL) spectra were recorded on a
SpexFluorolog spectrometer in the front-face geometry at
room temperature, in the spectral range from 300 to 450 nm
under a 275 nm excitation from a Xenon lamp.
The SERS activity of glucose was investigated using
grown AgNP films at different T
s
as SERS chips. These chips
can be prepared by keeping droplets of aqueous glucose solu-
tion with a concentration of 0.18 g/dL (10
−5
M) to 100 g/dL
(5.5 mM) onto the surface of the AgNP substrates and
allowing them to dry naturally. SERS spectra were recorded
using the Raman spectrometer as described in ref [3,6]. The
acquisition time for each measurement was set at 10 s. We
recorded SERS spectra at different positions on the sample
surfaces and no significant differences were observed.
Results and Discussion
The XRD patterns of AgNP’s films on Si substrate grown with
different T
s
are presented in Fig. 1. For all T
s
, except 600 °C,
the films have a mixed texture revealed by the existence of
two diffraction peaks located at 2θ≈38.14° and 2θ≈44.26°
,
respectively. These peaks are assigned, respectively, to the
(111) and (200) sets of lattice planes (JCPDS 4–0783). The
change in the preferred orientation of the films with increasing
substrate temperature is qualitatively calculated from the tex-
ture coefficient of (111) and (200) reflections. In general, tex-
ture coefficient (T
c
) and lattice strain (ε) influences the inten-
sity of Braggpeaks causing change of preferred orientation. T
c
and εfor preferred orientation [13] are calculated using the
following formulae and tabulated in Table 1:
Tc¼ImhklðÞ
∑ImhklðÞ
ε¼dcosθ
4
where I
m
is the measured peak intensities and dis the an-
gular line width of the half maximum intensities of the (111)
and (200) reflections and θis the Bragg angle.
Figure 1b shows the T
s
dependence of the T
c
for (111)
(I
(111)
/(I
(111)
+I
(200)
)) and (200) (I
(200)
/(I
(111)
+I
(200)
))
orientations. The texture coefficient of (200) increases and that
of (111) decreases as the T
s
increases from RT to 500 °C. This
change of orientation is due to the migration of adatoms on the
surface of the substrate to find their lowest energy position. It
is known that, for the fcc Ag crystal, (111) plane has the lowest
surface energy, while the (200) plane has the lowest strain
energy [14,15]. As previously mentioned, the XRD profiles
of Ag thin films deposited atlower T
s
show the (111) preferred
orientation, due to the minimization of surface energy and the
highest packing density [16,17]. However, as T
s
increases, the
(200) orientation becomes preferred instead of the previous
one, in such a way that when T
s
reaches 600 °C, only the
(200) orientation is observed. By increasing T
s
, the strain en-
ergy is reduced (Table 1) and the contribution of the surface
energy becomes less important [18]. Thus, the films grow in
(200) preferred orientation that is parallel to the (100) sub-
strate orientation.
Representative SEM images of the surfaces of the samples,
deposited at different T
s
ranging from RT to 600 °C on Si
substrate, are shown in Fig. 2a–f. The sample deposited at
RT has a percolated morphology. By increasing T
s
up to
500 °C, the AgNPs grow in height and diameter, and, conse-
quently, the NP surface density decreases and well-separated
AgNP’s are observed in samples grown at temperatures above
200 °C. The sample deposited at 600 °C is composed of iso-
lated spherical and ellipsoidal AgNPs. As it can be
ascertained, the mean size of the AgNPs exhibits a non-
monotonous dependence on T
s
. Figure 2g shows the AgNP’s
mean size as a function of T
s
, in the 100–600 °C temperature
range. The AgNP size increases as T
s
increases from RT to
300 °C, where the maximum mean size (61 ± 1.8) is reached.
Plasmonics

On further T
s
increasing, the AgNP’s mean size decreases. At
higher temperatures, scattering of atoms from heated substrate
surface might restrict the formation of clusters of crystallites
and might lead to low grain size. Bedir et al. [13]alsoob-
served the grain size and micro strain first increased up to
certain temperature and then decreased with the increase of
T
s
. At 600 °C, the increasing thermal energy input is mainly
used for texture restructuring rather than grain growth, as it is
evident from XRD.
Figure 3a presents the total reflectance spectra of Si sub-
strate and the AgNPs deposited on Si substrate, at different T
s
.
In the short wavelength region (λ< ~ 330 nm), the films of
AgNPs consistently show a reduced reflectance relative to the
Si substrate due to the combined effects of interband transi-
tions of the metallic NPs [19]. Large-reduced reflectance cen-
tered around 390 nm is due to the excitation of quadrupolar
SPRs (QR) of AgNPs [20]. Usually, QRs arise from bigger
AgNPs and show maximum forward scattering, leading to the
reduced reflectance in the spectral range centered on 390 nm
[21,22]. The temperature dependence of the QR (see Fig. 3b)
exhibits the non-monotonous character. As T
s
increases from
RT to 300 °C, the QR wavelength shifts to 405 nm and then it
is blue shifted down to 389 nm with further T
s
increasing up to
400 °C, keeping almost constant wavelength at 389 nm for the
films for which T
s
is above 400 °C. Coming back to Fig. 3a,
for larger wavelength, the reflectance of the AgNP films is
larger than in the Si substrate. The reflectance spectra consist
of a broad band, whose maximum shifts monotonously to
higher wavelength as T
s
increases (see Fig. 3b). This behavior
corresponds to the dipolar SPRs (DR) of AgNPs, which have
the equal probability for forward and backward scattering of
incident light [19]. The AgNP film deposited at 300 °C shows
the smaller reflectance over the entire spectral region. Thus, it
can facilitate forward scattering and causes the efficient light
trapping into the silicon substrate.
Photoluminescence emission spectra of the samples grown
at different T
s,
under the excitation wavelength of 275 nm are
shown in Fig. 4a. It is found that the samples deposited at 200,
300, 400, and 600 °C exhibit broad asymmetrical PL band,
pointing out that the PL band has more than one component.
Therefore, a sum of Gaussian function was fitted to the exper-
imental PL spectrum. The continuous lines in Fig. 4b–ewere
determined from the fit procedure. The de-convoluted peaks
were observed around 346 and 384 nm, respectively. PL emis-
sion in the UV-Visible region peaked at ~346 nm and is close
to the PL band of bulk silver (330 nm) [22–24]. PL emissions
from AgNPs with the emission wavelength maxima of about
330 nm have also been reported in refs. [25–27]. Several
mechanisms have been proposed to explain the PL emissions
from noble metals in the visible and infrared region [28–30].
Smitha et al. reported the similar PL emission at 332 nm from
Ag nano colloids, which has been attributed to the radiative
Fig. 1 a XRD patterns of Ag
films deposited on Si at different
T
S
in high vacuum. bChange of
I
(111)
/(I
(111)
+I
(200)
)andI
(200)
/
(I
(111)
+I
(200)
) with T
s
Tabl e 1 XRD analysis of texture
coefficient and micro strain of
AgNP thin films grown at
different T
s
Ts Texture Coefficient (111) Texture Coefficient (200) Micro strain (111) ε×10
−4
RT 0.84592 0.15408 15.87
100 0.48576 0.51423 24.12
200 0.45053 0.54947 24.32
300 0.07656 0.92344 22.46
400 0.00662 0.99338 18.55
500 0.01114 0.98886 14.84
600 0 1
Plasmonics

recombination of an electron from an occupied sp–band with
the holes in the valance d band [31]. Since the PL peak in our
experiments is close to those PL maxima referred above, we
assume that a similar mechanism is responsible for the ob-
served PL emission that was reported here. The position of
the emission band at 384 nm is close to the QR wavelength,
observed in the reflectance spectra. It is also observed that the
PL peak emission intensity has been enhanced with increase
of T
s
, but the PL peak positions remain almost T
s
-independent.
The intensity of peaks may be intensively influenced by the
increase of interactions between AgNPs due to change in mi-
crostructure. From Fig. 4a, it is clear that the luminescence
intensity increases with Ts. The relative intensity of peak 1
(band-band transition) and peak 2 (Ag NPs) (I
1
/I
2
)isshown
in Fig. 4f; it could be concluding from the monotonous de-
crease of the ratio I
1
/I
2
that the contribution of Ag NPs in-
creases with increasing T
s
. By combining Fig. 3b and Fig.
4f, we may conclude that the DR of AgNPs play a key role
compared to the QR in the enhancement of the luminescence
intensity.
The AgNP films were utilized as SERS chips to trace the
presence of glucose. Figure 5a presents the SERS spectra of
10
−5
M glucose solution dispensed on the AgNP substrates
grown at different T
s
. The band located at 1345 cm
−1
is assigned
to the C-C-H bending mode of glucose [32]. Figure 5bshows
the SERS intensity (peak height) of the Raman band at
Fig. 2 SEM images of silver thin films grown at different T
s
.RT(a), 100 (b), 200 (c), 300 (d), 400 (e), 600 (f) in high vacuum, and shows the particle
size as a function of T
s
(g)
Fig. 3 a Reflectance spectra of
Ag films deposited on Si at
different T
s
and bQuadrupolar
(QR) and dipolar (DR) SPR
wavelength as a function of T
s
Plasmonics

1345 cm
−1
of glucose as a function of T
s
. Each data point rep-
resents an average of three measurements taken at three different
places on the sample, to confirm the homogeneity of the
substrate and reproducibility of the results. The changes in
SERS intensity can be explained by the changes of Ag nanopar-
ticle size as well as interparticle distance. For example, in [33], it
Fig. 5 a Raman spectra of
glucose adsorbed onto AgNP
substrates grown at different
values of T
s
.bHeight of the
Raman peak 1 (1345 cm
−1
)versus
T
s
.cReflectance spectra of Ag
films deposited on Si at different
T
s
, following the increasing of the
glucose concentration and dSPR
shift versus glucose concentration
Fig. 4 a Photoluminescence
spectra of AgNPs deposited at
different Ts with the excitation of
275 nm. b-e De-convoluted peaks
of PL spectra using the Gaussian
approximations. fVariation of
convoluted peaks intensity ratio
with the T
s
Plasmonics

was shown that SERS signal of adenine molecules deposited on
an ordered Ag nanoparticle array increases with the increased
particle size and decreased with the interparticle distance. In the
same way, the SERS intensity of glucose Raman band at
1345 cm
−1
increased first and then decreased when T
s
changes
from RT to 500 °C in consistence with the particle size.
However, the increased intensity at T
s
= 600 °C is attributed to
the decreased interparticle distance as evident from SEM (Fig.
2). The higher SERS activityobservedforthecaseT
s
=300°Cis
due to the coupling of the excitation line (514 nm) with the DR
plasmon of the substrate deposited at 300 °C. This interpretation
supports that the SERS effect of the AgNPs can be mainly
attributed to the effective coupling of the wavelength of incident
laser with DR band. SERS activity also strongly depend on the
morphology of AgN Ps. The optimum SERS intensity at
T
s
= 300 °C can be attributed to the larger particle size as evident
from the SEM analysis (Fig. 3g). As the particle size increases,
the electromagnetic field contribution increases and consequent-
ly promote the SERS activity. Further, the gap between the Ag
NPs so called Bhot spots^also contribute to higher SERS activ-
ity [6].
We have also studied the glucose sensitivity in the SPR
monitoring of the resonance dip as a function of glucose con-
centration at the Ag/Si junction. Different concentrations of
glucose were used, from 0 to 100 mg/dL. We are interested in
these concentrations since according to the guidelines set by
the National Institute of Diabetes and Digestive and Kidney
Diseases, fasting glucose levels below 50 mg/dL indicate se-
vere hypoglycemia and potential brain function impairment,
while glucose concentrations of 70–99 mg/dL are considered
normal, and concentrations over 100 mg/dL are indicative of a
pre-diabetic condition [34]. Figure 5c depicts the changes in
the reflectance of the AgNPs, when glucose aqueous solution
was dropped and dried on the AgNP film deposited at 600 °C,
following the increasing of the glucose concentration. The
pure Ag film shows a dip at 391 nm associated with the QR
and when glucose aqueous solution was dropped on the film, a
clear red shift in the QR is observed with increasing glucose
concentration as shown in the Fig. 5d. It can be seen that the
SPR shift varies linearly with the glucose concentration.
Previously it was reported that AgNPs in ethanol solution
interact selectively with glucose, giving rise to a red shift of
20 nm for the addition of 50 mg/dL
−1
glucose solution [35].
The present work shows the better sensitivity where 40 nm
redshift was observed for the addition of 50 mg/dL
−1
glucose
solution. Further, the red shift reaches 74 nm as the glucose
concentration achieves 100 mg/dL
−1
as evidenced from Fig.
5d. This can be used for quantitative analysis. However, in
further work, the sensitivity of glucose will be tested in the
presence of the interfering proteins, buffer salts, and analyte
mixtures typically found in bodily fluids based on both SERS
intensity and SPR shift and which may lead to the fabrication
of a practical diagnostic biosensor.
Conclusions
The microstructure and optical (reflectance and
photoluminescence) properties of silver nanoparticles depos-
ited by pulsed laser deposition at different substrate tempera-
tures in high vacuum were investigated. SEM analysis re-
vealed that AgNP’s size is maximum at Ts = 300 °C and is
attributed to restructuring of crystal texture as evidenced from
XRD analysis. In total reflectance from silicon substrates, a
sharp valley due to forward scattering, which corresponds to
quadrupolar resonances, and a broad peak due to backward
scattering of the incident light that corresponds to dipolar res-
onances were observed. The film grown at 300 °C showed a
maximum reflectance reduction from the silicon substrate in
the visible region, which will be useful for Si-based photovol-
taic and photo electronic detectors. The room temperature
photoluminescence spectra of silver nanoparticles show an
increasing intensity of emission with increasing substrate tem-
perature. The silver nanoparticle film grown at 600 °C was
used for quantitative glucose detection in the range 0–100 mg/
dL and a clear red shift of 74 nm inthe resonance positionwas
observed as the glucose concentration achieves 100 mg/dL.
The SERS results demonstrate glucose detection at the phys-
iological concentration by Raman spectroscopy, with the low-
est laser power (16 mW) and the shortest integration time
(10 s). This would be important for potential glucose detection
in urine, tear, or sweat.
Acknowledgments This study has been partially funded by the follow-
ing: (i) the Portuguese Foundation for Science and Technology (FCT)
under the project PTDC/FIS/098943/2008, strategic projects PEST-C/
FIS/UI0607/2011 and UID/FIS/04650/2013; (ii) the European COST
Actions MP0901-NanoTP and MP0903-NanoAlloy. The author J.P.B.S.
is grateful for financial support through the FCT grants SFRH/BPD/
92896/2013. The author KCS acknowledges UGC, New Delhi, for the
startup grant (F.4-5(59-FRP)/2014(BSR)). The authors would also like to
thank Engineer José Santos for technical support at Thin Film Laboratory.
References
1. Zeng B, Gan Q, Kafafi ZH, Bartoli FJ (2013) Polymeric photovol-
taics with various metallic plasmonic nanostructures. J Appl Phys
113:063109
2. Atwater HA, Polman A (2010) Plasmonics for improved photovol-
taic devices. Nat Mater 9:205
3. Kamakshi K, Silva JPB, Sekhar KC, Marslin G, Agostinho MJ,
Conde O, Almeida A, Pereira M, Gomes MJM (2016) Influence
of substrate temperature on the properties of pulsed laser deposited
silver nanoparticle thin films and their application in SERS detec-
tion of bovine serum albumin. Appl Phys B Lasers O 122:108 (1 -
8)
4. Anker JN, Hall WP, Lyandres O, Shah NC, Zhao J, Van Duyne RP
(2008) Biosensing with Plasmonic nanosensors. Nat Mater 7:442
5. Berini P (2013) Surface plasmon photodetectors and their applica-
tions. Laser Photonics Rev 8:197
Plasmonics

6. Kamakshi K, Sekhar KC, Almeida A, Moreira JA, Gomes MJM
(2014) Tuning the surface plasmon resonance and surface-
enhanced Raman scattering of pulsed laser deposited silver nano-
particle films by ambience and deposition temperature. J Opt 16:
055002 (5 pp)
7. Kamakshi K, Sekhar KC, Almeida A, Moreira JA, Gomes MJM
(2015) Surface plasmon resonance coupled photoluminescence and
resistive switching behavior of pulsed laser deposited Ag: SiC
nanocermet thin films. Plasmonics 10:1211–1217
8. Gong P, Li H, He X, Wang K, Hu J, Zhang S, Yang X (2007)
Preparation and antibacterial activity of Fe
3
O
4
@Ag nanoparticles.
Nanotechnology 18:285604
9. Cheng XR, HauBYH, EndoT, Kerman K (2014) Au nanoparticle-
modified DNA sensor based on simultaneous electrochemical im-
pedance spectroscopy and localized surface plasmon resonance.
Biosens Bioelectron 53:513–518
10. Acimovic SS, Ortega MA, Sanz V, Berthelot J, Garcia-Cordero JL,
Renger J, Maerkl SJ, Kreuzer MP, Quidant R (2014) LSPR chip for
parallel, rapid and sensitive detection of cancer markers in serum.
Nano Lett 14:2636–2641
11. Nakayama K, Tanabe K, Atwater HA (2008) Plasmonic nanoparti-
cle enhanced light absorption in GaAs solar cells. Appl Phys Lett
93:121904
12. Wang J (2008) Electrochemical Glucose Biosensors. Chem Rev
108:814–825
13. Bedir M, ÖztaşM, Hüsniye K (2013) Effect of the substrate tem-
perature on the structural, optical and electrical properties of spray
deposited CdS:B films. J Mater Sci Mater Electron 24:499–504
14. Jianmin Z, Yan Z, Kewei XU (2005) Dependence of stresses and
strain energies on grain orientations in FCC metal films. J Cryst
Growth 285(3):427–435
15. Fei MA, Jianmin Z, Kewei XU (2005) Surface-energy-driven ab-
normal grain growth in Cu and Ag films. App Sur Sci 242(1–2):55–
61
16. Tao F, Bingyao J, Sun Z, Wang X, Lu X (2008) Study on the
orientation of silver films by ion-beam assisted deposition. App
Sur Sci 254:1565–1568
17. Jung YS (2004) Study on texture evolution and properties of silver
thin films prepared by sputtering deposition. Appl Surf Sci 221:
281–287
18. Sekhar KC, Levichev S, Kamakshi K, Karzazi O, Doyle S,
Chahboun A, Gomes MJM (2013) Effect of rapid thermal anneal-
ing on texture and properties of pulsed laser deposited zinc oxide
thin films. Mater Lett 98:149–152
19. Thouti E, Chander N, Dutta V, Komarala VK (2013) Optical prop-
erties of Ag nanoparticle layers deposited on silicon substrates. J
Opt 15:035005
20. Temple TL, Mahanama GDK, Reehal HS, Bagnall DM (2009)
Influence of localized surface plasmon excitation in silver
nanoparticles on the performance of silicon solar cells. Sol
Energy Mater Sol Cells 93:1978–1985
21. Temple TL, Bagnall DM (2013) Broadband scattering of the solar
spectrum by spherical metal nanoparticles. Prog Photovolt Res
Appl 21:600–611
22. Apell P, Monreal R, Lundqvist S (1988) Photoluminescence of
noble metals. Phys Scr 38:174
23. Whittle DJ, Burstein E (1981) Raman-scattering by resonant mole-
cules at smooth metal-surfaces. Bull Am Phys Soc 26:777
24. Yeshchenko OA, Dmitruk IM, Alexeenko AA, Losytskyy MY,
Kotko AV, Pinchuk AO (2009) Size-dependent surface-plasmon-
enhanced photoluminescence from silver nanoparticles embedded
in silica. Phys Rev B 79:235438
25. Mohamed MB, Volkov V, Link S, El-Sayed MA (2000) The ‘light-
ning’gold nanorods: fluorescence enhancement of over a million
compared to the gold metal. Chem Phys Lett 317:517–523
26. Varnavski OP, Mohamed MB, El-Sayed MA, Goodson T (2003)
Relative enhancement of ultrafast emission in gold nanorods. J
Phys Chem B 107:3101–3104
27. Beversluis MR, Bouhelier A, NovotnyL (2003) Continuum gener-
ation from single gold nanostructures through near-field mediated
intraband transitions. Phys Rev B 68:115433
28. Zhang AP, Zhang JZ, Fang Y (2008) Photoluminescence from col-
loidal silver nanoparticles. J Lumin 128:1635–1640
29. Xie FT, Bie HY, Duan LM, Li GH, Zhang X, Xu JQ (2005) Self-
assembly of silver polymers based on flexible isonicotinate ligand
at different pH values: syntheses, structures and photoluminescent
properties. J Solid State Chem 178:2858–2866
30. Yeshchenko AO, Bondarchuk IS, Losytskyy MY, Alexeenko AA
(2014) Temperature dependence of photoluminescence from silver
nanoparticles. Plasmonics 9:93–101
31. Smitha SL, Nissamudeen KM, Philip D, Gopchandran KG (2008)
Studies on surface plasmon resonance and photoluminescence of
silver nanoparticles. Spectrochim Acta Part A 71:186–190
32. Quyen TTB, Su WN, Chen KJ, Pan CJ, Rick J, Chang CC, Hwang
BJ (2013) Au@SiO
2
core/shell nanoparticle assemblage used for
highly sensitive SERS-based determination of glucose and uric ac-
id. J Raman Spectrosc 44:1671–1677
33. Wang HH, Liu CY, Wu SB, Liu NW, Peng CY, Chan TH, Hsu CF,
Wang JK, Wang YL (2006) Highly Raman-enhancing substrates
based on silver nanoparticle arrays with tunable sub-10 nm gaps.
Adv Mater 18:491–495
34. Bantz KC, Meyer AF, Wittenberg NJ, Im H, KurtuluşÖ, Lee SH,
Lindquist NC, Oh SH, Haynes CL (2011) Recent progress in SERS
biosensing. Phys Chem Chem Phys 13:11551–11567
35. Serra A, Filippo E, Re M, Palmisano M, Vittori-Antisari M,
Buccolieri A, Manno D (2009) Non-functionalized silver nanopar-
ticles for a localized surface plasmon resonance-based glucose sen-
sor. Nanotechnology 20:165501–165508
Plasmonics