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Different strategies for single molecule
detection through nanoplasmonics
Enzo Di Fabrizio - Remo Proietti Zaccaria
Istituto Italiano di Tecnologia (IIT)
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Magna Graecia
University
IIT
Genova
Nanophotonics is the interaction of light with
micro/nanometric structures in order to realize optically
induced phenomena such as:
• light harvesting
• waveguiding (photonic crystals, quasi crystals, fibers, etc.)
• wavefront engineering
• near-field microscopy (STM, SNOM)
• near-field spectroscopy (SERS, TERS, SPPERS)
plasmonics (metallic-like nanodevices)
20 m
a)
b)
100nm
What is NanoPhotonics/Plasmonics?
1 Co
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Why NanoPhotonics?
2
Device oriented
nanophotonics
Photonics
COMPLEX SYSTEM
CO
MP
LE
X S
YS
TE
M C
OM
PLE
X S
YS
TE
M
COMPLEX SYSTEM Co
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Light is fun
3 Co
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Light is science
4
Micro
machine
Cloaking
device
X-rays zone-plate
Photonic
Crystal (PhC)
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Outline C
ort
on
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013
• Planar structures & Photonic crystals
• Metallic structures & Plasmonics
• AFM-Raman: toward few/single molecule detection
• Adiabatic compression in details (not too many though)
• Detection in Attomolar solution concentration
• Artificial Lotus effect
• Computational approach: a very powerful resource
5
• Few photons problem
• Electroporation
• Modulated SPPERS
• Adiabatic electrical generation
• Hot electrons nanoscopy
• THz antennas
• Optical computing
• Opto-mechanics
• Plasmo-catalysis
• Thermo-catalysis
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What is nanofabrication?
6
Bottom-up & Top-Down
approaches
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7 a-Si 2D Photonic Crystal
Coll. F. Pirri group
3D PH. Crys. By X-ray lithography 2D Bragg reflector Si/SiO2 Coll. F. Priolo
Topographic lenses
Planar nanostructures
A little something about Photonic Crystals
8
3D
1D PhC
Light?
2D PhC
n1 n2 n1 n2 n1
Fundamental request: translational periodicity
1D
2D
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Photonic crystals: the cradle of photonics
Ingredients:
• Different materials (no bulk)
• Dielectric or metal (absorption)
• Translational symmetry (1D, 2D, 3D)
What we can do:
• Filters
• Hot spot cavities with high Q factor
• Planar waveguides
• Fibers
• Fano modes
• Extention to quasi-crystals (self-similarity)
• Explain natural phenomena (butterfly color)
• Color changing paints
• Nonlinearity: optical computing
9 Co
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10
Metallic standing nanostructures
Elongated dimer
nanostars (flower-
like) patterns were
fabricated with
Electron Beam
Lithography.
H = 0-170 nm IPS = 6-250nm Branch ≈ 70 nm core ≈ 80 nm
Elongated Nanostar (flower-like) dimer pattern
SERS applications
A little something about Plasmonics
11
Surface Plasmon Polaritons (SPP)= surface electromagnetic wave
Light is compressed without changing the carried energy
High spatial resolution (nm scale)
kx~1/
light line
=kc/n
Conservation
law: kx
dielectric
metal
z
x
The problem of optics (but not only): diffraction limit ( /2)
How can we see things at the nanoscale with visible/IR/THz light
(>400nm)?
SPP line: light is
compressed!
bulk bulk SPP
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Outline C
ort
on
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• Planar structures & Photonic crystals
• Metallic structures & Plasmonics
• AFM-Raman: toward few/single molecule detection
• Adiabatic compression in details (not too many though)
• Detection in Attomolar solution concentration
• Artificial Lotus effect
• Computational approach: a very powerful resource
• Few photons problem
• Electroporation
• Modulated SPPERS
• Adiabatic electrical generation
• Hot electrons nanoscopy
• THz antennas
• Optical computing
• Opto-mechanics
• Plasmo-catalysis
• Thermo-catalysis
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Combination of AFM-Raman spectroscopy
12
Open challenge:
nanodevice on a cantilever
efficiently acting as AFM tip
and as a nanontenna for
Raman scattering.
F
d
Raman & force measurements
Force measurements
Co
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13
01 0 01 3
Mark Stockman,
PRL 93, 137404 (2004)
Electric field
Inte
nsity
Effective refractive index
Phase velocity
14
Adiabatic compression
De Angelis et al., Nature Nanotech. 5,
67 (2010)
Adiabatic compression
Energy at the nanoscale
Nm
erical sim
ula
tion
Calc
ula
tion
benzenethiol
Radial mode
(TM0)
Tip radius < 10nm
High spatial
resolution
5fs
ec r
adia
l excitation
(ba
nd
wid
th: 0
.1P
Hz-0
.85
PH
z, 3
50
nm
-3m
)
Scala
r E
fie
ld
Ve
cto
r E
fie
ld
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Fabrication process: pillar growth
15
Electron Beam
5 Kev, 2 nm spot
Si-N Membrane
gold
Pt precursor gas
100 nm
pillar height 2.5 m
pillar base 100 nm
Tip radius of curvature 10-15 nm
15 nm
16
Single QD Raman spectrum C
ort
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Amine peak estimated 10 NH2
groups (from company linkage
data) maximum 80 NH2 groups
De Angelis et al. Nano Lett., 8 (8), 2321–2327 (2008)
17
QDs manipulation and deposition on the NW C
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18
Adiabatic cone on PhC C
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Gold and Silver cones
Di Fabrizio, E., et al., Italian patent n. TO2008A000693 23.09.2008
5 nm radius
19
AFM-Raman spectroscopy C
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Nanodevice on a cantilever
efficiently acting as AFM tip and as
a nanontenna for Raman scattering.
20
Optical setup C
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Focal plane on the
cantilever
Focal plane on the tip end
TASC – CBM Trieste
21
Raman & AFM: chemical sensing C
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silica
Cantilever with
Nano-Cone
Laser lithography Si/SiO2
(optical image)
10 m
Silicon nanocrystal
SiOx Raman
Band
Si Raman
Band
22
Raman & AFM: chemical sensing, coarse scan C
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silica
Silicon nanocrystal
Scan length 2 µm
Scan step ~220 nm
p1 p2 p3 p4 p5 p6 p7 p8 p9 p10
2 m
Cantilever with
Nano-Cone
23
Raman & AFM: chemical sensing, fine scan C
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Fine scan along the “wall”.
AFM scan step: 7 nm
110 nm Sensing and topography resolution 5-10 nm
From Raman detailed line shape analysis
we found nano crystal size 5-7 nm
Topography Raman intensity
at 520 cm-1
Simultaneously:
AFM topography
24
Selected results C
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Nanocone on biological samples C
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Nanocone performs
exceptionally well on biological
samples in physiological
environment
Lipid bilayers in liquid: 4 nm
thickness. Sharp topography
without shear effects.
Topography on insulin fibrils in
liquid: down to resolution of
protofibrillar structures (3-4 nm).
Only 1 report in literature.
Force spectroscopy
on titin protein
Titin Pulling
25
26
Recent results:SERS on amyloid fibrils (on silicon) C
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1
2
Amyloid fibrils are involved in
Alzheimer disease.
Their characterization by AFM
is widely used, however to
date there are few reports
about their Raman signature.
Here we show that insulin
fibrils on silicon, bear a
Raman signature (1),
compared to the background
(2).
1 um scan (topography)
1
2
27
Adiabatic compression: behind the scenes C
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SPP
Ag
Strong field
laser
(visible)
27
Adiabatic compression: behind the scenes C
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SPP
Ag
Strong field
laser
(visible)
What kind of source?
28
The source C
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x
z
Plane wave
X-polarized
Radial polarization
x
y
z
29
3D simulation: radial-like source C
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Adiabatic compression
Field enhancement ~100
Strong localization
500nm
x
z
30
3D simulation: longitudinal plane wave X C
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NO Adiabatic compression
Phase dependence
Field enhancement ~20
500nm
x
z
31
Summarizing…
Nature Nanotech. 5, 67 (2010)
Adiabatic compression
Energy at the nanoscale
Nm
erical sim
ula
tion
Calc
ula
tion
benzenethiol
Radial mode
(TM0)
Tip radius < 10nm
High spatial
resolution
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Opt. Exp. 19, 22268 (2011)
PRB 86, 035410 (2012)
Opt. Lett. 37, 545 (2012)
Outline C
ort
on
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013
• Planar structures & Photonic crystals
• Metallic structures & Plasmonics
• AFM-Raman: toward few/single molecule detection
• Adiabatic compression in details (not too many though)
• Detection in Attomolar solution concentration
• Artificial Lotus effect
• Computational approach: a very powerful resource
• Few photons problem
• Electroporation
• Modulated SPPERS
• Adiabatic electrical generation
• Hot electrons nanoscopy
• THz antennas
• Optical computing
• Opto-mechanics
• Plasmo-catalysis
• Thermo-catalysis
32
33
Diffusion limit C
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1 fM analyte concentration
34
Question: can the diffusion limit be avoided?
SuperHydrophobicity for analyte concentration
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Evaporation implies
concentration and localization
35
Artificial Lotus effect: micropatterned surface C
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• Full controllable size
• High aspect ratio (up to 20 or more)
• Both rigid and flexible substrates
Photolithography combined with Deep RIE
10 m
36
Artificial Lotus effect C
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Evaporation of 10 ml of water in few minutes
36
Artificial Lotus effect C
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Evaporation of 10 ml of water in few minutes
Few molecules...
and we know where they are!
37
Evaporation and concentration (10 Attomolar)
Rhodamine
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38
Raman detection of Rhodamine on pillars C
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1050 1250 1450 1650 1850
Inte
ns
ity
(a
rb.
un
its
)
Raman shift (cm-1)
Rhodamine 6G
10 l - 10-17 mol/l
Roughly 10 Rhodamine
molecules!
39
Combination of Plasmonics and hydrophobic surfaces C
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200 nm
4 m 40 m
40 Co
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3 m
50 nm
Combination of Plasmonics and hydrophobic surfaces
41 Co
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m m
m m
Combination of Plasmonics and hydrophobic surfaces
42
Selected results C
ort
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Outline C
ort
on
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• Planar structures & Photonic crystals
• Metallic structures & Plasmonics
• AFM-Raman: toward few/single molecule detection
• Adiabatic compression in details (not too many though)
• Detection in Attomolar solution concentration
• Artificial Lotus effect
• Computational approach: a very powerful resource
43
• Few photons problem
• Electroporation
• Modulated SPPERS
• Adiabatic electrical generation
• Hot electrons nanoscopy
• THz antennas
• Optical computing
• Opto-mechanics
• Plasmo-catalysis
• Thermo-catalysis
44
200nm
=514/5
30nm
d: 30nm
-200nm
Signal
Noise
• very high signal to noise ratio ~ 100
• field localization
#1: Few photons sub-wavelenght transmission
Max E ~1.7V/m
Z
Polarization: X
Holes diameter: 80nm
0: 530nm
Period: 1 m
|E| @ z=150nm along x (nm)
--- 514nm
--- 530nm
(Ihole/Ibg)x~1400
and
(Ihole/Ibg)y~120
Very high signal
to-noise ratio !
~E0
Decay of |E| along z (nm)
(side hole)
--- 514nm
--- 530nm
(Ihole/Ibg)x~1400
and
(Ihole/Ibg)y~120
Very high signal
to-noise ratio !
~E0
hole
~10nm 1/e
European project: FOCUS
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45
200nm
=514/5
30nm
d: 30nm
-200nm
Signal
Noise
• very high signal to noise ratio ~ 100
• field localization
#1: Few photons sub-wavelenght transmission
Max E ~1.7V/m
Z
Polarization: X
Holes diameter: 80nm
0: 530nm
Period: 1 m
|E| @ z=150nm along x (nm)
--- 514nm
--- 530nm
(Ihole/Ibg)x~1400
and
(Ihole/Ibg)y~120
Very high signal
to-noise ratio !
~E0
Decay of |E| along z (nm)
(side hole)
--- 514nm
--- 530nm
(Ihole/Ibg)x~1400
and
(Ihole/Ibg)y~120
Very high signal
to-noise ratio !
~E0
hole
~10nm 1/e
E field travelling through the slab
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Va
Vb
Vc
= electrode
#2: Computational electroporation
46 Co
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#2: Computational electroporation
DNA is negatively charged
47 Co
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48
#3: Modulated SPPERS (Energy/Life) U
nfo
lde
d p
rote
in
Pro
pa
ga
tin
g lig
ht
Fo
lde
d p
rote
in
Lo
ca
lize
d lig
ht
• Logic ports (1/0 unit)
optical computing
• Near/Far-field Spectroscopy
Adia
ba
tic c
om
pre
ssio
n!
1 m
Au
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49
#4: Electrically generated energy concentrator
Laser approach
a)
Electrical
contribution:
adiabatic
compression
~V Hot
electrons
injection
Wide excitation range Not yet possible
(maximum frequency:
100 GHz;
Visible: 500THz)
b)
Electrical approach
Narrow excitation range
Magnetic
contribution:
spectroscopical
shift
• Near-field
magnetic probe?
• Magnetic
compression?
1≠ 2
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50
#5: Plasmonic hot electrons nanoscopy
5 m m
=1060nm (1.17eV); P=2.43 m;
d=365nm; Tip radius= 25nm
500nm
Ho
t ele
ctro
ns m
ap
an
d m
orp
ho
log
y m
ap
GaAs: Egap=1.42eV
Highly efficient photon-to-
hot electrons conversion
(>30%)!
(k vector from the cone)
AF
M
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#6: THz antennas (0.1-10THz) Characteristics of THz:
• can penetrate inside most dielectric materials that may be opaque to
visible light
• has low photon energies that do not cause photoionization in
biological tissues
Applications of THz:
• imaging of plastic/ceramic/semiconductors (e.g, quality control)
• spectroscopy (semiconductors, molecules, DNA, proteins)
51
Diffr
action lim
it:
/2
Solu
tion:
resonant
pla
sm
onic
nanoante
nnas
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#7: Optical computing
52
Logic gate:
AND
T-shape
antenna:
Fano mode
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53
#8: Opto-mechanic interactions at the
nanoscale Rb = 60nm
H = 3.5 um
T_polymer = 30nm (SU8)
Rho = 1217.9 Kg/m3 (SU8)
Young_mod = 3.1982*108 (1/10
SU8)
Poisson_ratio = 0.33
Core = 30nm Au
Immagine SEM
da Mario
Applications:
• time (msec) resolved spectroscopy (quality
factor, force spectroscopy, sensing)
• microfluidics
• optofluidics
V
m
V V
V V
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54
#9: Plasmocatalysis
UV
TiO2
e-
h+
O2
O-2
OH-
*OH
Two main issues:
1) UV light (<5% total) Visible with doping
(nitrogen, tungsten, etc.)
2) High e-h recombination rate & low light
absorption Resonant plasmonic
nanodevices
Bayarri et al., Chem.
Eng. J. 200, 158 (2012)
c)
J. Mater. Chem., 2008,
18, 1858-1864
+ superhydrophobicity!
Al
Nature Nanotech. 247, 8, 2013
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55
#10: Localized high temperature catalysis
Below 1000 C:
Ag=961 C - Au=1065 C - Al=595 C
Ti=1670 C - Cu=1083 C - Cr=1857 C
Pt= 1768 C
e.m
. field
heat sourc
e
tem
pera
ture
440
300
K
Joule effect:
P =J·E
Rb
Te
mp
era
ture
(K
)
Single gold nanoantenna
=1070nm; P=15 W; Waist=1 m;
L=500nm; W=25nm
Conduction
heat transfer:
P= T·S·k/d,
kair=0.026
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Thank you!
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Extra
Remo Proietti Zaccaria
Istituto Italiano di Tecnologia (IIT)
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Computational/analytical research flow chart
Photonic Crystals Plasmonic
structures
Application:
SPPERS*
*Surface Plasmon Polaritons Enhanced Raman Spectroscopy;
Quasicrystals
Application:
Quasicrystals
fibers
Fundamentals:
Quasicrystals
properties
Fundamentals:
symmetry mode
in slab cavities
Metallic Photonic
Crystals
Fundamentals: High
Q factor & Low
modal volume
Fundamentals:
Adiabatic
devices
Super-long
SPP
SMD project Focus project
Nanoantenna project
Applications:
Super-lenses
Sub-wavelength
sensors
E1 Co
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E2
Computational and analytical instruments
RSoft
• Plane wave expansion (PMW)
• Rigorous Coupled Wave Analysis (RCWA)
• Finite Difference Time Domain (FDTD)
Finite Difference
Ttime Domain
(FDTD)
Lumerical CST
Finite Integrate
Technique (FIT)
Robust but not
versatile
Finite Element
Method (FEM)
Less robust than
CST but very
versatile
Comsol
Mathematica
Analytical tool
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E3
Plasmonic at the DUV range (Life/Energy)
Energy (eV)
Experi
ment
Sim
ula
tion
Al/Al2O3 nanoparticles array
E near-field
Extinction e
ff.
Extinction
4 6 8 10
ACS Nano 2013
5.8eV!
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High temperature catalysis (Env.) Matrix of gold nanoantennas
Localized temperature pattern!
400nm
E4 Co
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KA
US
T 2
013
E5
V V
V V
V V
V V
V V
V=1.1V
V=0.3V
V=0.6V