Gold nanoparticles embedded in glassblair/T/ece6461/notes/intro.pdfLocalized resonances/ -...
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Gold nanoparticles embedded in glass
“Labors of the Months” (Norwich, England, ca. 1480).The ruby color is attributed to gold nanoparticles.
2pω
pω
3pω
++ -- ++ -- ++ --
+ + + +
+++
---
Bulkmetal
Metalsurface
Metal spherelocalized SPPs
Plasmon resonance positions in vacuumPlasmon resonance positions in vacuum
0=ε
1−=ε
2−=εdrudemodel
- - - -
drudemodel
Surface Plasmon PhotonicsSurface Plasmon PhotonicsOptical technology using- propagating surface plasmon polaritons- localized plasmon polaritons
Topics include:
Localized resonances/ - nanoscopic particleslocal field enhancement - near-field tips
Propagation and guiding - photonic devices- near-field probes
Enhanced transmission - aperture probes- filters
Negative index of refraction - perfect lensand metamaterials
SERS/TERS - surface/tip enhanced Raman scattering
Molecules and - enhanced fluoresencequantum dots
Also called:• Plasmonics• Plasmon photonics• Plasmon optics
Plasmon-PolaritonsWhat is a plasmon ?
• Compare electron gas in a metal and real gas of molecules
• Metals are expected to allow for electron density waves: plasmons
Strong local field
Metal
Dielectric
z
I
E
HNote: This is a TM wave
• Sometimes called a surface plasmon-polariton (strong coupling to EM field)
Surface plasmon
Bulk plasmon• Metals allow for EM wave propagation above the plasma frequency
They become transparent!
Local Field Intensity Depends on Wavelength
Long wavelength Short wavelength
z
I
z
I
D << λo
Characteristics plasmon-polariton • Strong localization of the EM field • High local field intensities easy to obtain
Applications: • Guiding of light below the diffraction limit (near-field optics)• Non-linear optics• Sensitive optical studies of surfaces and interfaces• Bio-sensors• Study film growth• ……
Optical Properties of an Electron Gas (Metal)Dielectric constant of a free electron gas (no interband transitions)
( ) ( ) ( ){ }Re expt i tω ω= −E E• Consider a time varying field:
• Equation of motion electron (no damping)2
2
dm edt
= −r E
• Harmonic time dependence ( ) ( ) ( ){ }Re expt i tω ω= −p p
• Substitution p into Eq. of motion: ( ) ( )2 2m eω ω ω− =p E
( ) ( )2
2
1em
ω ωω
= −p E• This can be manipulated into:
• The dielectric constant is:
• Dipole moment electron ( ) ( )t e t= −p r
22
2
dm edt
=p E
( )( )
22
2 20 0
11 1 1 pr
N Nem
ωωε χ
ε ω ε ω ω= + = = − = −
pE
ωrε
pω
6
Resonance conditions
)(1)(
2
γωωω
ωεj
p
+−=
Use a Drude model: Free electron (Lorenz model with no restoring force)
Bulk
Bulk Resonance condition : ε(ω)=0 ω=ωp.
Dispersion Relation for EM Waves in Electron Gas Determination of dispersion relation for bulk plasmons
( ) ( )2
22 2
,,r tt
cε ∂
= ∇∂E r
E rt
• The wave equation is given by:
• Investigate solutions of the form: ( ) ( ) ( ){ }, Re , expt i i tω ω= ⋅ −E r E r k r
2 2 2r c kω ε =
2
21 pr
ωε
ω= −• Dielectric constant:
22 2 2 2 2
21 pp c k
ωω ω ω
ω − = − =
ω
k
pω
No allowed propagating modes (imaginary k)
ckω =
2 2 2p c kω ω= +• Dispersion relation:
Note1: Solutions lie above light lineNote2: Metals: ħωp ≈ 10 eV; Semiconductors ħωp < 0.5 eV (depending on dopant conc.)
Dispersion Relation Surface-Plasmon PolaritonsSolve Maxwell’s equations with boundary conditions
• Maxwell’s Equations in medium i (i = metal or dielectric):
0iε∇ ⋅ =E 0∇⋅ =H 0µ∂
∇× = −∂HEt iε
∂∇× =
∂EHt
• At the boundary:
Metal
DielectriczE
H
, ,x m x dE E=
x
ym ydH H=m zm d zmE Eε ε=
• We are looking for solutions that look like:
( ) ( )0, ,0 expm ym xm zmH i k x k z tω= + −H
( ) ( ),0, expm xm zm xm zmE E i k x k z tω= + −E
( ) ( )0, ,0 expd yd xd zdH i k x k z tω= + −H( ) ( ),0, expd xd zd xd zdE E i k x k z tω= + −E
• Mathematically: z<0
z>0
ii iε
∂∇× =
∂EHt
Dispersion Relation Surface-Plasmon Polaritons
• Start with curl equation for H in medium i (as we did for EM waves in vacuum)
( ) ( )0, ,0 expi yi xi ziH i k x k z tω= + −Hwhere
( ) ( ),0, expi xi zi xi ziE E i k x k z tω= + −E
( ) ( ), , ,0, ,0,yi yizi xi zi xizi yi xi yi i xi i zi
H HH H H H ik H ik H i E i Ey z z x x y
ωε ωε∂ ∂ ∂ ∂ ∂ ∂
− − − = = − ∂ ∂ ∂ ∂ ∂ ∂
zi yi i xik H Eωε= −• We will use that: zm yi m xmk H Eωε= −
zd yd d xdk H Eωε= −
• E// across boundary is continuous: , ,x m x dE E=
zm zdym yd
m d
k kH Hε ε
=
• H// across boundary is continuous: ym ydH H=
Combine with: zm zdym yd
m d
k kH Hε ε
=zm zd
m d
k kε ε
=
Dispersion Relation Surface-Plasmon Polaritons
Relations between k vectors
• Condition for SP’s to exist: zm zd
m d
k kε ε
=
• Relation for kx (Continuity E//, H//) : xm xdk k=
• For any EM wave:
zdk
zmkExample
1mε = −
1dε =z
z
22 2x zi ik k
cωε + =
22
sp x i zik k kcωε = = −
• Both in the metal and dielectric:
zm zd
m d
k kε ε
=
1/ 2
m dx
m d
kc
ε εωε ε
= +
Dispersion relation
homework
Example Air
SiO2true at any boundary
Dispersion Relation Surface-Plasmon Polaritons
1/ 2
m dx
m d
kc
ε εωε ε
= +
Plot of the dispersion relation
• Last page:
• Plot dielectric constants
• Low ω: 1/ 2
limm
m dx d
m d
kc cε
ε εω ω εε ε→−∞
= ≈ +
• At ω = ωsp (when εm = -εd):
ω
rε
pωspωdε−
dε dielectricmetal
xk →∞
ω
k
spω
dkcω ε=
• Note: Solution lies below the light line
Dispersion Relation Surface-Plasmon Polaritons
Dispersion relation plasma modes and SPP
• Note: Higher index medium on metal results in lower ωsp2
21 pm d
ωε ε
ω= − = − 2 2 2
p dω ω ε ω− = −2
2
1p
d
ωω
ε=
+ω = ωsp when:
Metal/air
Metal/dielectric with εd
1p
d
ωω
ε=
+
,SP Airω
, dSP εω
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Propagation length
Methods of SPP excitationMethods of SPP excitation
nprism > nL !!
zx
E0θ
R
kxdε
mε
0ε
Excitation by ATRExcitation by ATR
Kretschmann configuration Otto configuration
zx
E0θ
R
kx
dεmε
0ε
total reflection at prism/metal interface-> evanescent field in metal-> excites surface plasmon polariton at
interface metal/dielectric medium
metal thickness < skin depth
total reflection at prism/dielectric medium-> evanescent field excites surface plasmon
at interface dielectric medium/metal
usful for surfaces that should not be damagedor for surface phonon polaritons on thick crystals
distance metal – prism of about λ
ATR: Attenuated Total Reflection
zx
θ
R
kSP,xdε
mε
0ε kphoton,x
< kSP,xkphoton,x
θ
R
kSP,x
kphoton,x
= kSP,xkphoton,x
no SPP excitation SPP excitation
Excitation by ATRExcitation by ATR
SPP excitation requires = kSP,xkphoton,x
Excitation by Kretschmann configurationExcitation by Kretschmann configuration
photon indielectric
photonin air
xk
ω
SPP dispersion
ck=ω
z
x
0θ
dε
mε0ε
0εωc
k =
ck ω
=
( )00 sin θεωc
kx =
( )00 sin/ θεω xkc=
0ω
( )0000
sin1
θεεεω cc
k m
m
x
=+
= Resonancecondition
0xk
1+=
m
mx c
kε
εω
Kretschmann configuration – angle scanKretschmann configuration – angle scan
0θ R
0θ
p-polarized
s-polarized-> no excitation of SPPs
illumination freq. ω0= const.
photonin air
kx
ω
0ω
R
0θ
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Transmission EnhancementSingle hole
T. Thio et al., “ Optical transmission through a single sub-wavelength aperture,” Opt. Lett. 26, 1972 (2001).
Sample Parameters300 nm thick Ni filmFIB milling 5 nm resolution100nm AG film on one side30 nm Ag layer sputtered
Plan view
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Extraordinary transmission through an array of holes
a0 = separationd= hole diametert=film thickness
23
Ebbesen experiment
24
TheoryNormal incidence
25
Hole period scaling
13
Localized surface plasmonresonance
Dipole surface plasmon is excited when a long-wavelength electromagnetic wave (λ>>d) is incident on a metallic sphere
Metallic sphere
EM wave
Plane-wave E-field E0e-i ω t
dλ
ε0εm
2
Plasmon-resonant nanoparticlesSurface plasmon (SP): collective excitation of conduction
electrons, using light at a resonant (visible to NIR) frequency
www.gold.org
Scattering from single Au nanospheres
Ag NPs (20−150 nm): λSP = 380−600 nm
Plasmon-enhanced extinction:ε = 109−1011 M-1 cm-1
Csca = 10-13−10-9 cm2
φsca = 0.04−0.90
Au NPs (20−150 nm): λSP = 520−660 nm
Lycurgus Cup, 4th century A.D.
(Ag-Au NP’s embedded in
glass)
Absorption: red Scattering: green
Brit
ish
Mus
eum
, Lon
don
14
Localized SPR frequency
00
0
23 EE
min εε
ε+
=
)()(1 222
22
22
2
γωωωγ
γωω
ε+
−+
−= ppm j
Field inside the metal particle
Complex function
Simple Drude model for a metal
ωp is the plasma frequency , the dielectric function has a negative real part for ω < ωp.
Real part of denominator vanishes at the SPR: 12 0 +=
εω
ω pSPR
nanopar&cle sca,ering and ex&nc&on
par&cle polarizability
ex&nc&on cross-‐sec&on (units of area)
total sca,ering cross-‐sec&on (units of area)
€
α = 4πa3 εm −ε oεm + 2ε o
a = particle radius ε o = surrounding medium
€
Cext =2πλImaginary α{ }
€
Csca =16π
2πλ
⎛
⎝ ⎜
⎞
⎠ ⎟ 4
α 2
Kriebig and Vollmer, Optical Properties of Metal Clusters, c.1995.
Physical description of plasmons (cont’d)Electrodynamic Mie TheoryCan calculate dipolar optical response with great accuracy,especially if performed under “quasi-static” conditions(valid when particle size is less than 30 nm)
1240 62
0
413
310
Generalized Mie Theory:Can calculate approximate optical response for metal nanoparticles of all shapes and sizes; accounts for higher-order effects such as phase retardation, quadrupolar resonances, etc.
Calculated plasmon response from spherical Au nanoparticles in H2O:
Yguerabide, Anal. Biochem. 1998, 262, 137.
Calculated response (extinction) from metal nanoparticles (in air):
eV-to-λ (nm)conversion: eV
1239=λ
λ (nm)
6
Size effects on localized SPRs
Surface scattering of oscillating electrons: plasmon lineshape (Γ) broadens with 1/R
Calculated plasmon response from spherical Ag nanoparticles in H2O: Yguerabide, Anal. Biochem. 1998, 262, 137.
Phase retardation: redshift and broadening of λSP for particles greater than LE, the electron mean free path (40-50 nm)
Higher-order plasmon resonances: increase in probability with larger particle size (also a function of LE)
Dipolar mode
Quadrupolar mode
Octupolar mode
6
15
SPR – refinements – particle shape and core/shell
• Gold and silver metal particles –shape dependence
)3(21
21
)3( |)(|)( χωγωγχ =eff
• Core-shell particles have larger enhancement
Ellipsoidal shapes
M&M – metal shell creates resonance in the coreεs
εc
Γ+Γ−
=)()1(
)(11
11 ωεε
εωγmii
−−+++−+−++
=))((2)2)(2()]/()2)(()2[()(
11
1111 εεεεδεεεε
εεεεεεδεεεωγ
sscscs
ssscsc
εm
16
Nanoshells
17
Absorption and Field enhancementCdS/Ag
core-shell ratio of 0.7The field magnitudes are scaled to the asymptotic applied field value. The surface plasmon resonance appears near a wavelength of 600 nm.
18
Heterostructured nanoparticles
core
Shell
Metal shell: surface plasmon resonance shifts by more than 500 nm observed. Enhanced nonlinear effects and intrinsic optical bistability observed.
PRB 47, 1359 (1993); PRB 50, 12052 (1994).
Exp.: A gold sulfide sample is decomposed into gold particles. The transformation begins at the surface.Numbers are time lapses.
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Tunability
12
SP modes as a function of aspect ratio:Link and El-Sayed, J. Phys. Chem. B 1999, 103, 3073
Transverse SP
Longitudinal SP(λmax)
Au
LSP
TSP
Au NRs: Tunable resonances in the NIR
Anisotropic metal nanoparticles: Au nanorods
Attenuation is minimized between 750 nm and 1.3 μm
H2 O
1 0 - 2
1 0 2
1
1 0
.2 .4 .6 .8 1 .0 2 . 4 . 6 . 8 .
H b O 2-1
Abs
orpt
ion
Coe
ffici
ent
Wavelength (µm)
Absorption Transmission Absorption
1 0 - 1
“Biological window” in tissue at NIR wavelengths:
Anisotropic metal nanoparticles: Au nanorods
13
Seeded growth using micellar surfactants (CTAB):
Sau and Murphy, Langmuir 2004, 20, 6414.Zweifel and Wei, Chem. Mater. 2005, 17, 4256.
AgNO3, CTAB
AuCl4, ascorbic acid15-60 min
3-nm Au particle seeds
Two-stage growth kinetics: effect on LPR wavelength
Wavelength (nm)400 500 600 700 800 900 1000
Nor
mal
ized
O.D
.
1x wash, 0 d1x wash, 1 d2x wash, 0 d2x wash, 1 d
1st growth stage (fast): dumbbell-shaped NRs(stabilized after Na2S)
2nd growth stage (slow):Cylindrical NRs
Au avg. width: 15-20 nm
avg. length: 40-60 nm
Synthesis of NIR-resonant Au nanorods
14
Nanostars (seeded growth from Au NPs)
Pentagonal bipyramids (decahedra)
Nanoshells(SiO2@Au)
Nanocages (growth on Ag nanocubes, with galvanic displacement)
Nanoprisms (by nanosphere lithography)
Haynes and van Duyne, J. Phys. Chem. B 2001, 105, 5599.
Kelly et al, J. Phys. Chem. B2003, 107, 668
Sanchez-Igleisias et al,Adv. Mater. 2006, 18,
2529
Lal et al., Acc. Chem. Res.2008, 41, 1842
Siekkinen et al, J. Am. Chem. Soc. 2006, 128, 14776
Nehl, Liao, and Hafner, Nano Lett. 2006, 6, 683
Other anisotropic Au nanoparticles
Local field factors increase nonlinearly as a function of particle diameter–spacing ratio (γ)
Size of ensemble, unit particle size are also important factors in EM enhancement
EM field factors in NP assemblies:
Calculation of G = (E/E0)4 in Ag NP dimer, as a function of interparticle separation
Xu et al, Phys. Rev. E 2000, 62, 4318.
λex=514.5 nm; 2R =90 nm, S= 1 or 5 nm (Ag)
GEM
S = 1 nm
S = 5 nm
Local EM field factors (E/E0): extends for several nanometers from NP surface, in direction of LSPR mode
Origin of plasmon-amplified signals in surface-enhanced Raman scattering (SERS) and other optical emissions
Plasmon-enhanced field effects
7
A. Surface-enhanced Raman scattering (SERS)
N
R'
H
R
nanostructured Ag and Au surfaces(roughness ~ 10-200 nm)
200 400 600 800 1000 1200 1400
cm -1
analyte
hν1 hν2
Raman spectrum
• Label-free chemical sensing• Multiplexing capabilities• Water is Raman-silent
• relationship between nanostructure and activityoften not well-defined
• SERS-active substrates are easy to make, but can be tricky to reproduce
Plasmon-enhanced emissions
8
SERS activity is strongly correlated with local electromagnetic (EM) field factors
“Hot spots” can be found at edges and tips of anisotropic NPs, but can be even stronger in gaps between closely spaced metal nanostructures
Liu et al. Adv. Mater. 2005, 17, 2683.
SERS-active “nano-crescents” Self-assembled Au nanoparticle arrays
Wei et al, ChemPhysChem2001, 2, 743.
Genov, Sarychev, Shalaev, Wei, Nano Lett. 2004, 4, 153.
λex=647 nm; γ = 5 or 10 (Au)2D array of 87-nm Au NPs
“Hot Spots” in SERS-active substrates
9
B. Surface-enhanced fluorescence (SEF)Highly sensitive to distance between fluorophore and metal surface: SEF also relies on local EM field factors, but excited states can be quenched by back-electron transfer
Multilayers of phospholipid or BSA−biotin/avidin over Ag NPs, then coated with fluorophore
Fluorescence intensity of biotin−FITC on top of (1) six, (2) four, and (3) two monolayers formed by alternating avidin and BSA−biotin.
Nanometric coatings for optimizing SEF (up to 20-fold increase in fluorescence)
Sokolov, Chumanov, and Cotton, Anal. Chem. 1998, 70, 3898.
No SEF
Plasmon-enhanced emissions
10
C. Förster resonance energy transfer (FRET)
Energy transfer mediated by overlap between emission and absorption (donor−acceptor) bands; D−A distance <10 nm
Dye-doped Ag@SiO2 core-shell NPs
Plasmon-enhanced FRET: greater efficency and range
Lessard-Viger et al, Nano Lett. 2009, 9, 3066.Wang and Wang, Integr. Biol. 2009, 1, 565
Shell=7 nm 13 nm 23 nm
D A
Plasmon-enhanced emissions
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A. Resonant light scattering: Darkfield microscopy
Aaron et al, Opt. Express 2008, 16, 2153.
Cross-polarized scattering: a novel method of noise reduction for anisotropic NP labels
Ag nanoparticles of variable size and shape
Plasmon-resonant NPs used as biological imaging labels must also compete with other scatterers.
Spherical NP
Stellated NP 90° scattering (from incident polarization)
A431 cells with anti-EGFR labeled nanostars
Linear pol. Cross pol.
no NPs
Imaging: Metal NPs as optical contrast agents
12
B. Multiphoton excitation
400 500 600 700 800 9000.0
0.4
0.8
1.2
0.0
0.2
0.4
0.6
0.8
I PL (a
.u.)
Abso
rban
ce (a
.u.)
Wavelength (nm)
sp-hole relaxation after 2-photon absorption
2ν ν’5d
6sp
TPL intensity vs. Au NR absorption:
Wang et al. PNAS 2005, 102, 15752.
Au
Au
fs-pulsed
laser excitation
TPL of Au NRs on glass slide
1
2
pol.
Two-photon excited luminescence (TPL) from Au nanorods
Imaging: Metal NPs as optical contrast agents
13
(a) TPL image of Au NRs (green) internalized by KB cells after a 5-hour incubation (linescan = 75 µm).
(b) Intensity profile across yellow linescan in (a); high SNR provided by TPL contrast.
a b
Huff et al, Nanomedicine 2007, 2, 105.
In vivo TPL imaging of Au NRs flowing through blood
vessel in mouse ear
In vitro TPL imaging of Au NR uptake by KB cell: single-particle sensitivity
Wang et al. PNAS 2005, 102, 15752.
Multiphoton imaging has very low autofluorescence
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SERS reporter label: Malachite Green
Targeted in vivo delivery of SERS labels to tumor in nude mouse model:
in vitro detection of labeled SERS tags: compares well with fluorescence imaging
Qian et al, Nat. Biotechnol.2008, 26, 83.
C. Au NPs as SERS tags
Imaging: Metal NPs as optical contrast agents
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Optical coherence tomography
200 um
tissue surface
Oldenburg et al, J. Mater. Chem. 2009, 19, 6407.Eghtedari et al, Nano Lett. 2007,7, 1914.
Relatively high loadings of Au NPs are still required to generate sufficient contrast in tissue for these imaging modalities.
Photoacoustic tomography
PAT of Au NRs within nude mouse (before and after injection)
OCT contrast by Au NRs in human breast carcinoma tissue
After Au NR injection
D. Other optical modalities for biomedical imaging
Imaging: Metal NPs as optical contrast agents
17Govorov and Richardson, Nano Today 2007, 2, 30.
Absorbed light is mostly converted into heat
abs
p
ETmc
∆ =Estimation of surface temperature on Au NP:
0
( )4
NPV QT rk rπ
∆ =
Eabs =absorbed photon energym =mass of Au NPcp = heat capacity of Au
ΔT for 5-nm Au sphere =15 K at LSPR saturation
Estimation of heat transfer to environment of Au NP:
1/r dependence
VNP = volume of NPQ = heat of NPk0 = thermal conductivity of mediumr = distance from surface
Photothermal activity of metal nanoparticles
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((( )))
Link and El-Sayed, Int. Rev. Phys. Chem. 2000, 19, 409.Pitsillides et al, Biophys. J. 2003, 84, 4023.
10-15 (fs) 10-12 (ps) 10-9 (ns) 10-6 (μs) 10-3 (ms) 100 (s)
Au
1. Electron thermalization;transient plasmon bleaching
2. Electron-phonon collisions;local heating by 100s of °C
Au
3. Cavitation dynamics:microbubble expansion
Au
4. Microbubble collapse; acoustic energy released
Superheating can lead to mechanical release of energy
Timescale of photothermal response, induced by pulsed laser excitation:
Photothermal activity of metal nanoparticles
19
Internalized Au NRs
81 s scan, cw mode:Laser power = 6 mw; fluence = 24 J/cm2
Membrane-bound Au NRs on tumor cells
6mw CW
before
10 µm
after, w/ EB stain
Threshold fluence for hyperthermic damage (blebbing)
is 10X lower or more when nanorods are localized on cell
membranes
before after, w/ EB stain
Tong et al, Adv. Mater. 2007 19, 3136.
81 s scan, cw mode:Laser power = 60 mw; fluence = 240 J/cm2
before after, w/ EB stain
81 s scan, fs-pulsed mode:Laser power = 0.75 mw; fluence = 3 J/cm2
Photothermolysis of tumor cells mediated by Au NRs targeted to cell membranes
Why nanophotonics needs plasmons?
Courtesy of M. Brongersma
31
• Surface plasmon resonance• Continuous films
– Propagating mode couples to the surface and propagates
-Reflection dip at the phase matching angle for coupling
• Disontinuous films– Local field resonance condition
• Applications• Bio/chem assays• Cancer therapy• Photonic waveguides
Summary
32
References • BookP. N. Prasad, Nanophotonics, Wiley-Interscience (2004) Optics Express, Volume 12, Issue 16, (9 August 2004), Focus Issue: Extraordinary
Light Transmission Through Sub-Wavelength Structured SurfacesMetal particles: shape and core-shell effectsM. J. Bloemer et al., “Broadband Waveguide Polarizers Based On The Anisotropic
Optical Constants Of Nanocomposite Films,” J. Lightwave Tech. 14, 1534 (1996).
H.S. Zhou et al., “The Controlled Synthesis and Quantum Size Effect in Gold Coated Nanoparticles,” Phys. Rev. B 50, 12052 (1994).
J.W. Haus et al., “Enhanced Optical Properties of Metal-coated Nanoparticles,” J. Appl. Phys. 73, 1043 (1993).
J.W. Haus et al., ”Intrinsic Optical Bistability for Coated Particles,” Phys. Rev. A 42, 5613 (1990).
A. Neeves and M. Birnboim, Opt. Lett. 13, 1087 (1998).J. Haus, H.S. Zhou, S. Takami, M. Hirasawa, I. Honma, and H. Komiyama, J. Appl.
Phys. 73, 1043 (1993).R. Eychmuller, A. Mews, and H. Weller, Chem. Phys. Lett. 208, 58 (1993).H. Zhou, I. Honma, H. Komiyama, and J. Haus, J. Phys. Chem. 97, 895 (1993)H.S. Zhou, I. Honma, H. Komiyama, and J.W. Haus, Phys. Rev. B 50, 10210 (1994).R. Neuendorf, M. Quinten, and U. Kreibig, J. Chem. Phys. 104, 6348 (1996).
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ReferencesV.M.Shalaev, Nanoscale Linear and Nonlinear Optics, eds: M. Bertolotti and C.Sibilia, AIP p239-241 (2001).S. Oldenburg, R. D. Averitt, S. Westcott, and N. J. Halas, Chem. Phys. Lett. 288, 243
(1998).Y. Sun, Y. Xia, Anal. Chem. 74, 5297 (2002).Attridge, J.W.; Daniels, P.B.; Deacon, J.K.; Robinson, G.A.; Davidson, G.P. (1991)
Sensitivity enhancement of optical immunosensors by the use of a surface plasmonresonance fluoroimmunoassay, Biosens. Bioelectron. 1991; 6(3): 201-214
Bain C.D., Whitesides G.M. (1989) Modeling organic surfaces with self-assembled monolayers, Adv. Mater. 4: 110
K. Lance Kelly, Eduardo Coronado, Lin Lin Zhao, and George C. Schatz, J. Phys.Chem. B 107, 668-677 (2003).E. Prodan, C. Radloff, N.J. Halas and P. Nordlander, Science 302, 419-422 (2003).E.Prodan, P. Nordlander, Nano Lett. 3, 543-547 (2003).M.Brongersma, Nature Materials 2, 296, (2003).C.Loo, A. Lin, L. Hirsch, Min-Ho Lee, J. Barton, N. Halas, J. West, R. Drezek,Technology in Cancer Research and Treatment 3, 33-40 (Feb. 2004).E. Prodan and P. Nordlander,, J. Chem. Phys. 120, 5444-5454, (2004).
Websiteshttp://shay.ecn.purdue.edu/~ece695s/http://lanp.rice.edu/Plasmonics/publications.phphttp://www-ece.rice.edu/~halas/pubs.html