This presentation review a paper on SEIRA and SERS.

1. Optical Nanoantennas for
Multiband
Surface-Enhanced Infrared and
Raman Spectroscopy
1
Hossein Babashah
November 23rd, 2015
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2. 2
Results
& Discussion
51
Abstract
Optical
Nanoantennas
2
SERS
& SEIRS
3
Fabrication
& Measurement
4
Your
Questions
6
Agenda
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3. 3
Abstract
[2]www.balticent-palsmatec.org
 Goal: linear nanoantennas used as shared substrates for surface-enhanced
Raman and infrared spectroscopy (SERS and SEIRS, respectively)
 How the goal is achieved: by engineering the plasmonic properties of the
nanoantennas :
 1.make them resonant in both the visible (transversal resonance) and the
infrared(longitudinal resonance)
 2.rotating the excitation field polarization to selectively take advantage
of each resonance.
 Performance and fabrication: fabricated gold nanoantennas by electron
beam lithography on calcium di fluoride 
 1.a transverse plasmonic resonance in the visible (640 nm)
 2.a particularly strong longitudinal dipolar resonance in the infrared
(tunable in the 1280 -3100 )
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4. Abstract
4
[2]www.balticent-palsmatec.org
[3] Methylene Blue-Loaded Dissolving Microneedles
2
5 10
5
10
 Results: SERS and SEIRS detection of MB molecules adsorbed on
the nanoantenna's surface with signal enhancement factors of
for SERS (electromagnetic enhancement) and up to for
SEIRS.
 => field enhancement by transverse resonance is sufficient to
achieve SERS from single nanoantennas.
 tuning the nanoantenna length  signals of a multitude of
vibrational modes  enhanced with SEIRS. suitable for
integration on lab-on-a-chip scheme
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5. 5
Optical nanoantennas
 Definition: convert freely propagating optical radiation into enhanced optical
fields localized on nanometric regions of their surface hot spots.
 How they suit: arises from resonant coupling of light with localized surface
plasmon resonances (LSPR).
 Applications:
 1.electromagnetic field enhancement at the hot spots increase of the
vibrational signal of molecules Surface-enhanced Raman spectroscopy (SERS)
 2. amplify the infrared (IR) vibrational signals of adsorbed molecules and thin
layers. EF up to 104  increasing to 105  LSPR of a nanoantenna is resonantly
tuned to match IR vibration energy of the probe molecule surface-enhanced
infrared scattering (SEIRS)
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[4] Individual Nanoantennas Loaded with Three-Dimensional Optical Nanocircuits

6. 6
Simultaneous SERS and SEIRS
 Importance:
 important technique as a complementary tool to SERS with similarly high vibrational
sensitivity. Because of the different excitation mechanism, different selection rules and
different cross sections hold for IR and Raman activity.
 Complete vibrational information can be obtained, therefore, only with simultaneous
application of both techniques.
 Application:
 chemical, biological, and pharmaceutical analysis and sensing using specific plasmonic
nanostructures to enhance either the IR or the Raman signals.
 Other reports:
 Some approaches of shared substrates for SERS and SEIRS sensing,indeed more versatile and
simple to integrate in a lab-on-a-chip architecture. Examples include arrays of gold nano-
shells,self-assembled microemulsions, self-assembled pulsed laser deposited gold nanoparticles
clusters, sputtered thin- film gold electrodes,near-field coupled silver
nanowires,electrochemically treated copper surfaces,and silver nanoparticles clusters.
 Features:
 broad LSPRs from the visible to the IRbeing effective for plasmon-enhanced Raman and IR
spectroscopy.
 To optimize the response of a combined SERS SEIRS sensor optical nanoantennas much
more desirable.
 Linear nanoantennas, featuring two distinct LSPRs, precisely tune the first LSPR to specific IR
spectral regions, so to selectively enhance the desired IR vibrations, and to adjust the second
LSPR in the visible, close to the laser excitation, for maximum SERS enhancement.
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7. 7
Fabrication & Structure
 Nanoantennas have been fabricated by electron beam lithography on (100)
 Four sets of antenna arrays fabricated on the same wafer
 5 nm of Ti adhesion layer
 Each chain is separated from the neighboring one by 5 μm transverse coupling in the IR are optimal
 The longitudinal gap of 50 nm increases the antenna density  not important for the horizontal plasmon
resonance in the visible
2CaF
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8. Measurement (MB)
 To prove our concept MB as probe molecule
 the electronic resonances of MB permit exploiting the enhancement due to
resonant Raman scattering (RRS)  with low or no plasmonic enhancement.
 The strongly IR active C-H stretching modes from CH3 groups show up at higher
energies (2850-2950 cm-1).
 MB has been bound to gold surfaces following standard procedures
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9. Determination of LSPRs
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 extinction spectra of the four sets of nanoantennas after adsorption of MB.
 The IR LSPRs show up exciting the samples with a longitudinal field, E||, i.e.,polarized
along the long axis.
 In the visible, a single LSPR peak at 641 nm is observed for the transversal excitation
field, , i.e., polarized parallel to the short axis
 easily tunable nanoantenna  both LSPR frequencies can be optimized independently.
 antennas' length SEIRS enhancement
 width of the structures and excitation laser wavelength and the Raman bands to the
short axis maximum SERS /14

10. SERS experiment
 SERS spectrum of MB adsorbed on a single L = 1410 nm nanoantenna(HeNe laser beam)
 observation suggests that:
 (i) for longitudinal polarization no plasmonic enhancement at 633 nm
 (ii) RRS signal measured on the nanoantennas is almost originating from MB on the CaF2
 (iii) the contribution of MB on CaF2 to the total SERS signal is only 1%.
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11. SEIRS experiment
 SEIRS measurements the same sample used for SERS.
 The IR radiation was polarized parallel to the nanoantenna long axis
 A zoom-in of the IR LSPRs  resonance profiles are slightly distorted(Fano-type)
 Peak strongly in SEIRS due to the good match of its frequency to the LSPR
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12. Enhanced Factor
 Calculation: EF ratio between the SERS intensity of the peak intensity
corresponding reference RRS signal.
 Measurement considerations:
 the second derivative of the spectra calculated with respect to the photon
wavenumber for the various antenna lengths
 So, the peak size (and thus EF) is higher if the vibrational energy is closer to
the LSPR peak.
 In order to quantitatively calculate the EF, the second derivative of the Fano
profile fitted to the second derivative from experiment
 Longitudinal gaps below 50 nm increase near-field coupling of antennas =>
additional near-field confinement in the gaps higher EF=>near- field coupling
broadens the LSPR  broadens the spectral range for vibrational sensing.
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13. Conclusion
 SERS and SEIRS using the same linear optical antennas have been
successfully demonstrated.
 SEIRS enhancement factors up to 6×105, comparable to former studies, is
observed exciting the longitudinal dipolar resonance.
 SERS amplification between 102 and 103 (electromagnetic enhancement)
is obtained exciting the transverse LSPR.
 the IR the enhanced fields are confined at the nanoantenna edges
excitation of the transverse LSPR allows to extend the enhanced near-
field zone to all the molecules present over the antenna surface within
the laser spot, permitting to achieve SERS from a single nanoantenna.
 By changing the length of the antenna, multiple vibrational lines can be
enhanced in SEIRS in an extended range up to 3000 cm-1, enabling
improved identification of molecules and observation of molecular
changes
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14. References
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[1] Optical Nanoantennas for Multiband Surface-Enhanced Infrared and Raman
Spectroscopy , Cristiano D’Andrea,Jorg Bochterle
[2]www.balticent-palsmatec.org
[3] Methylene Blue-Loaded Dissolving Microneedles: Potential Use in Photodynamic
Antimicrobial Chemotherapy of Infected Wounds
[4] Individual Nanoantennas Loaded with Three-Dimensional Optical Nanocircuits
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15. 15
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Your Questions