Biomedical Engineering Reference
In-Depth Information
Figure 15.16
Comparative simulation of electric field distribution for
different nanostructures. Reproduced from G. Das, M. Chirumamilla, A.
Gopalakrishnan, A. Toma, S. Panaro, R. Proietti Zaccaria, F. De Angelis, E.
Di Fabrizio. Plasmonic nanostars for SERS application,
Microelectron. Eng
.,
111
, pp. 247-250, Copyright (2013),with permission from Elsevier.
for nanoantenna plasmonic structure. Focusing of electric field is
found very close to NST tip.
After confirmation from simulation results regarding the advan-
tageofNSTstructure,opticaltransmissionandSERSmeasurements
were performed for the periodic NSTs. In the past, few research
works were reported for gold NSTs, which were produced by
chemical technique [73]. Results report the variation of plasmonic
behaviors, depending on the polarization [68] and by changing the
molecules [74]. Herein, a reproducible periodic gold NSTs based
SERSdevicewasreported.Theopticaltransmissionspectrum(inset
of Fig. 15.17) shows its plasmon resonance, centered around 900
nm. SERS background measurement without any molecules was
investigated, shown in the inset of same Fig. 15.17. It shows a
featureless Raman spectrum, confirming the SERS nanostructures
contamination free. Cresyl violet (CV) is deposited over nanos-
tructures by means of chemisorption technique. SERS spectra of
CV, deposited over NSTs device and on Au marker, are shown in
Fig. 15.17. Various characteristic Raman bands of CV molecules can
be found throughout the experimental range [75, 76]. In the figure,
itcanbefoundtheRamansignalenhancementwhendepositedover
patterned area, though the laser power and integration time are
reduced with respect to the SERS measurement on marker. Taking
into consideration all the experimental parameters and the number
ofmoleculesdepositedclosetoNSTtip,SERSenhancementfactoris
2.80
10
4
with respect to the Au marker.
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