1 r. bachelot h. ibn-el-ahrach 1, o. soppera 2, a. vial 1,a.-s. grimault 1, g. lérondel 1, j. plain...
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R. BachelotR. Bachelot, H. Ibn-El-AhrachH. Ibn-El-Ahrach11, O. Soppera, O. Soppera22 , A. Vial , A. Vial11 ,A.-S. ,A.-S. GrimaultGrimault11, G. Lérondel, G. Lérondel11, J. Plain, J. Plain11 and P. Royer and P. Royer1 1
1 Laboratoire de Nanotechnologie et d’Instrumentation Optique, Institut Charles Delaunay. FRE CNRS 1 Laboratoire de Nanotechnologie et d’Instrumentation Optique, Institut Charles Delaunay. FRE CNRS 2848. Université de Technologie de Troyes, France2848. Université de Technologie de Troyes, France
2 Département de Photochimie Générale ,Université de Haute-Alsace Mulhouse, France2 Département de Photochimie Générale ,Université de Haute-Alsace Mulhouse, France
Spectral degeneracy breaking in plasmon resonance of single metalnanoparticles by nanoscale near-field photopolymerization
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Geometry : shape and size Geometry : shape and size – Rods, stars, triangles…Rods, stars, triangles…– Chemical synthesis / e-beam lithographyChemical synthesis / e-beam lithography
Single particle coupling (dimers, trimers,chains,..)Single particle coupling (dimers, trimers,chains,..)
Core/shell approachCore/shell approach– Ex: «Nanorice»Ex: «Nanorice»
(Rice University)(Rice University)
Effective refractive index (polymer coating, surrounding medium) Effective refractive index (polymer coating, surrounding medium) – Nanosensors Nanosensors – But so far only isotropic modification (symmetry was kept)But so far only isotropic modification (symmetry was kept)
What about anisotropic modification of the surrounding index ?What about anisotropic modification of the surrounding index ?
Tuning plasmon resonance of metallic Tuning plasmon resonance of metallic nanoparticles (MRS bulletin May 2005, Vol. 30, nanoparticles (MRS bulletin May 2005, Vol. 30,
N°5)N°5)
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Based on local isomerization
A new approach: local photopolymerization
Triggered by local enhanced fields of metal nanostructures
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The Photopolymer The Photopolymer formulationformulation
composition:
Initiator ( Eosin Y)
Co-initiator (MDEA)
Monomer (PETIA)
Radical polymerization
Eosin absorption spectrum
h
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The photopolymer formulationThe photopolymer formulation
Formulation propertiesFormulation properties– Polymerization threshold Polymerization threshold
energyenergy– Refractive indexRefractive index
1.48 for 0% reticulation
(liquid formulation)
1.52 for 100% reticulation
(Crosslinked polymer)
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A key parameter : the threshold A key parameter : the threshold energy.energy.
Far field characterization of this Far field characterization of this parameterparameter
Optical fiberLens
Diaphragm
Beam splitter
Mirror
Polarizer
Experimental set-up
Interference area
Ar laser 515nm
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Far field characterization of the Far field characterization of the PhotopolymerizationPhotopolymerization
Experimental characterization of the threshold energy of polymerization
(a)AFM image of a polymer grating obtained after 12mJ/cm²
(b)AFM image of a polymer grating obtained after 20mJ/cm²
4 6 8 10 12 14 16 18 20 22 24-0.2
0.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
1.6
1.8
2.0
Gra
tin
g d
ep
th
m)
Dose (mJ/cm2)
Threshold polymerization
energy
Threshold energy value = 10 mJ/cm²
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PrinciplePrinciple
Incident energy EIncident energy Eii< E< Ethresholdthreshold
Near field Near field photopolymerizationphotopolymerization
Dose
x
Dincidente
Dpolymérisation
Dose
x
Incident energy
Threshold energy
Confined optical source
Overcoming the threshold energy by local enhancement of the optical near field
P
FDTD
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Experimental approachExperimental approach
1) E-beam lithography1) E-beam lithography
4) Monomer removal (Rinsing)4) Monomer removal (Rinsing)5) Characterization: - AFM5) Characterization: - AFM
-Spectroscopy-Spectroscopy
2) 2) CoatingCoating (drop) (drop)
3) 3) IlluminationIllumination
Near field illuminationNear field illumination
Array of Ag particles
Argon Laser (514 nm)
linear Polarization
D=2,5mW/cm2
four time weaker than the
threshold polymerization value500 nm
Diameter ~ 70nmDiameter ~ 70nmheight = 50nmheight = 50nm
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Results : AFM imagesResults : AFM images
97nm260nm
AFM Images after irradiationAFM Images after irradiation
pp
Two symmetric polymer lobes built up near the metal particles and oriented along the direction of polarization of the incident light
Polymer lobes describe the spatial distribution of the optical near field of the metallic nanoparticle excited close to its dipolar plasmon resonance
p
E intensity E intensity ( FDTD)( FDTD)
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500 600
1,00
1,05
1,10
1,15
1,20
1,25
1,30
1,35
1,40
1,45
1,50
Inte
nsi
ty (
a.u
.)
Wavelenth (nm)
(a)
500 600
1,00
1,05
1,10
1,15
1,20
1,25
1,30
1,35
1,40
1,45
1,50
Inte
nsi
ty (
a.u
.)
Wavelenth (nm)
(b)
Results : polarized extinction Results : polarized extinction spectroscopyspectroscopy
New induced symmetry CC2
Spectral degeneracy breaking of the SPR in the hybrid nanoparticle
500 600
1,00
1,05
1,10
1,15
1,20
1,25
1,30
1,35
1,40
1,45
1,50
Inte
nsi
ty (
a.u
.)
Wavelenth (nm)
(c)
500 600
1,00
1,05
1,10
1,15
1,20
1,25
1,30
1,35
1,40
1,45
1,50
Inte
nsi
ty (
a.u
.)
Wavelenth (nm)
(d)
Two artificial plasmon eigenmodes (508nm and 528nm)
97nm
P
(a), (b) : isotropic response
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Polarized extinction spectroscopyPolarized extinction spectroscopyDipolar diagram
Eθ0
30
60
90
120
150
180
210
240270
300
330
508
512
516
520
524
508
512
516
520
524
Re
so
na
nc
e W
av
ele
ng
ht
(nm
)
Continuous tunable SPR mode ?
resonance()
0
30
60
90
120
150
180
210
240270
300
330
95
100
105
110
95
100
105
110
FW
HM
(
nm
)Linear combination of the two eigenmodes
FWHM maximum for 45 degrees / axis of the hybrid particle
FWHM ()
Quasi Continuous tunable SPR mode
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0
30
60
90
120
150
180
210
240270
300
330
1,12
1,16
1,20
1,24
1,28
1,12
1,16
1,20
1,24
1,28
ne
ff
d
dnn
nnn
Ag
mres
resmeff
/4
)(
Nanoscale effective index distribution neff()
Minor axis Major axis
Effective index 1,06 1,14 1,28
Hybrid particlesOriginal sample
Spatial extension of the two polymer lobes
neff()Dipolar diagram
Polarized extinction spectroscopy Polarized extinction spectroscopy distribution of nanoscale effective distribution of nanoscale effective
refractive indexrefractive index
Reference : particle surrounded by an “homogeneous” medium: glass substrate + liquid formulation before exposure ( nm~1.5)
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ConclusionConclusion
Controlled Nanoscale photopolymerization around a single Controlled Nanoscale photopolymerization around a single metallic particles excited close to their dipolar plasmon metallic particles excited close to their dipolar plasmon resonanceresonance
Breaking of symmetry of the dielectric environment of the Breaking of symmetry of the dielectric environment of the nanoparticlesnanoparticles– Spectral degeneracy breaking of the SPRSpectral degeneracy breaking of the SPR– Nanoscale effective index distribution Nanoscale effective index distribution – Tunability of the plasmon resonance Tunability of the plasmon resonance
First step towards new hybrid metal-organic particles with First step towards new hybrid metal-organic particles with new functionalities (polymer engineering) new functionalities (polymer engineering) – Refractive index, photoluminescence (absorption), Refractive index, photoluminescence (absorption), – NonlinearityNonlinearity– Exciting higher SP modesExciting higher SP modes– Multiple exposuresMultiple exposures
97nm
P
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Thank you for your Thank you for your attentionattention
Thanks to J.J. Greffet, R. Carminati Thanks to J.J. Greffet, R. Carminati and A. Bouhelierand A. Bouhelier
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which kind of energy conversion ?
In NSOM : energy transfer between evanescent waves and the nanoprobe conversion of inhomogeneous surfaces waves into homogeneous propagating waves
In our cases : near-field optical energy is locally transferred into chemical energy new method of near-field imaging + new functionalities
E:eosin, A:amine
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E *Eh AH ** AHE
** AEH *AM
E:eosin,
AH:amine
Case of the photo-polymerization
Case of the photo-izomerization (C. Hubert et al. Nanoletters 5, 615)
P
P Radical aminyle
+propagation+termination