plasmons in different shapes ppt

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NANOSTRUCTURAL PROPERTIESNANOSTRUCTURAL PROPERTIES

MASTER IN NANOSCIENCEMASTER IN NANOSCIENCE

AprilApril 20082008

Lourdes del Valle Lourdes del Valle CarrandiCarrandi

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�� IntroductionIntroduction

�� Synthesis of metallic Synthesis of metallic nanoparticlesnanoparticles

�� ResponseResponse--resonanceresonance

�� ConclusionsConclusions

�� BibliographyBibliography

IntroductionIntroductionIntroductionIntroductionIntroductionIntroductionIntroductionIntroduction

Metallic nanostructures have been a subject of considerable interest

in recent years. The field of metallic nanostructures is now more

popularly called plasmonics, since the major manifestation produced

by optical excitations is the collective oscillation of electrons, which

are localized along the interface. Hence, this wave is called a surface

plasmon wave.

Metal nanostructures and nanoparticles have found applications in a

wide variety of areas: catalysis, optics, optoelectronics, information

storage, biological and chemical sensing, and surface-enhanced

Raman scattering.

By tailoring the size and shape of metal nanoparticles, one can tune

their intrinsic properties.

Synthesis of metallic Synthesis of metallic Synthesis of metallic Synthesis of metallic Synthesis of metallic Synthesis of metallic Synthesis of metallic Synthesis of metallic

nanoparticlesnanoparticlesnanoparticlesnanoparticlesnanoparticlesnanoparticlesnanoparticlesnanoparticles

TwoTwo approachesapproaches::

--TOPTOP--DOWNDOWN

LithographyLithography

--BOTTOMBOTTOM--UPUP

ColloidalColloidal synthesissynthesis


nanoparticlesnanoparticlesnanoparticlesnanoparticlesnanoparticlesnanoparticlesnanoparticlesnanoparticlesTOPTOP--DOWNDOWN

LithographyLithography

Electron-beam-lithography (EBL):

Despite the sophistication and flexibility of these techniques, difficulties remain in

obtaining high-quality metal nanostructures (sharp corners and nanometer-scale

interparticle spacings) needed for exploitation of plasmon effects. To achieve greater

control over the atomic-scale structure of metal NPs, the complementary technique of

colloidal synthesis must be considered.

An electronbeam resist is first deposited on a substrate, and is then exposed

by scanning a focused electron beam over the surface. Development of the resist

removes the exposed portions. A metal layer is then deposited on the sample,

and the remaining resist is subsequently dissolved in a solvent, so that the metal

deposited on the unpatterned part of the samples is removed.

Optical properties of two interacting gold nanoparticlesW. Rechberger, A. Hohenau, A. Leitner, J. R. Krenn, B. Lamprecht and F. R. AusseneggOptics CommunicationsVolume 220, Issues 1-3, 1 May 2003, Pages 137-141


nanoparticlesnanoparticlesnanoparticlesnanoparticlesnanoparticlesnanoparticlesnanoparticlesnanoparticlesBOTTOMBOTTOM--UPUP

ColloidalColloidal synthesissynthesis

http://webs.uvigo.es/coloides/nano/research.html


nanoparticlesnanoparticlesnanoparticlesnanoparticlesnanoparticlesnanoparticlesnanoparticlesnanoparticlesThis technique of synthesis is inspired by Faraday’s two-phase system but

developed by Schiffrin and coworkers.

It uses the thiol ligands that strongly bind gold due to the soft character of both

Au and S.

AuCl4- is transferred from water to toluene using tetraoctylammonium

bromide as the phase-transfer reagent and reduced by NaBH4 in the presence

a thiol.

Depending on the ratio of the Au salt and capping agent (thiol), the particle size

can be tuned to between ~1 nm and ~10 nm.

Faraday, M. Experimental Relations of Gold (and otherMetals) to Light. Philos. Trans. 1857, 147, 145-181.

Synthesis of Thiol-Derivatized Gold Nanoparticles in a Two-PhaseLiquid-LiquidSystem. M. Brust, M. Walker, D. Bethell, D. J. Schiffrin, R. J. WhymanJ. Chem. Soc., Chem. Commun.1994, 801-802.


nanoparticlesnanoparticlesnanoparticlesnanoparticlesnanoparticlesnanoparticlesnanoparticlesnanoparticlesThe most popular method of preparing Au nanospheres dispersed in water is the

reduction of HAuCl4 in a boiling sodium citrate solution.

The formation of uniform Au nanoparticles is revealed by a deep wine red color

observed after ~10 minutes. The average particle diameter can be tuned over

quite a wide range (~10-100 nm) by varying the concentration ratio between the

Au salt and sodium citrate (less citrate leads to larger nanoparticles).

The same procedure can be used to reduce an Ag salt, but particle size control

is very limited.

Citrate reduction has also been applied to the production of Pt colloids of smaller

particle sizes (2-4 nm), which can be grown further by hydrogen treatment.

Standard citrate reduction introduced by Turkevich:

Turkevich, P. C. Stevenson, J. Hillie. A study of the nucleation and growth processes in thesynthesis of colloidal gold. Discussions of the Faraday Society. 1951, 11, 55-75.. OF THE FARADAY SOCIETY(11): 55 (1951)


nanoparticlesnanoparticlesnanoparticlesnanoparticlesnanoparticlesnanoparticlesnanoparticlesnanoparticlesIn the “polyol” process, AgNO3 is reduced at high temperature by ethylene

glycol, which also serves as the solvent. The use of polyvinylpyrrolidone (PVP)

as a capping agent leads to highly non-spherical silver particles, such as

singlecrystal nanocubes. The dimensions of Ag nanoparticles can be controlled

varying the experimental conditions (temperature, ratio of Ag salt and PVP, etc.).

Liz-Marzán and coworkers have reported the ability of N,N-dimethylformamide

(DMF) to reduce Ag+ ions, so that stable spherical Ag nanoparticles can be

synthesized using PVP as a stabilizer (larger PVP concentrations, star-like,

multipod nanoparticles).

Shape-Controlled Synthesis of Gold and Silver NanoparticlesYugang SUN, Younan XIA. SCIENCE 13 December 2002: Vol. 298. no. 5601, pp. 2176 - 2179

I. Pastoriza-Santos, L.M. Liz-Marzán, Formation of PVP-Protected Metal Nanoparticles in DMF Langmuir 2002, 18,2888-2894.

ResponseResponseResponseResponseResponseResponseResponseResponse--------resonanceresonanceresonanceresonanceresonanceresonanceresonanceresonance

The light absorption by metallic nanoparticles is described by coherent

oscillation of the electrons, which is induced by interaction with the

electromagnetic field. These oscillations produce surface plasmon waves.

The specific wavelengths of light absorption producing plasmon

oscillations are called surface plasmon bands or simply plasmon bands.

The electric field of the incoming radiation induces the formation of a

dipole in the nanoparticle. A restoring force in the nanoparticle tries to

compensate for this, resulting in a unique resonance wavelength.

The oscillation wavelength depends on a number

of factors, among which particle size and shape,

as well as the nature of the surrounding medium,

are the most important.

For nonspherical particles, such as rods,

the resonance wavelength depends also on the

orientation of the electric field.


For metallic nanoparticles significantly smaller than the wavelength of light, light absorption is within a narrow wavelength range. The wavelength of the absorption peak maximum due to the surface plasmon absorption band is dependent on the size and the shape of the nanocrystals, as well as on the dielectric environment surrounding the particles.

For extremely small particles

(less than 25 nm for gold),

the shift of the surface plasmon

band peak position is rather small.

For larger nanoparticles

(more than 25 nm for gold),

the surface plasmon peak shows

a red-shift.

Nanophotonics. Prasad, Paras N. Hoboken, New Jersey : Wiley-Interscience, 2004

Henglein, A., J. Phys. Chem. (1993) 97, 5457

Nanophotonics. Prasad, Paras N. Hoboken, New Jersey : Wiley-Interscience, 2004

For a nanorod-shaped metallic nanoparticle, the plasmon band splits into two bands corresponding to oscillation of the free electrons along (longitudinal) and perpendicular (transverse) to the long axis of the rod. The longitudinal oscillation is very sensitive to the aspect ratio of the particles.



Surface Plasmons on Metal Nanoparticles: The Influence of Shape and Physical EnvironmentCecilia NoguezJ. Phys. Chem. C 2007, 111, 3806-3819

Metal nanoellipsoids possess 3 plasmon resonances corresponding to the oscillation of electrons along the 3 axes of the NP. The resonance wavelength depends on the orientation of the electric field relative to the particle. Changing the axes length, the plasmon resonance frequencies of the nanoellipsoid can be tuned systematically.

Influence of morphology on the optical properties of metal nanoparticlesJournal of computational and theoretical nanoscience. A. L. González and Cecilia Noguez. Volume: 4 Issue: 2

Pages 231-238 Pulishes: Mar 2007


To understand the influence of morphology, the SPRs for polyhedral NP

have been recently studied. A general relationship between the SPRs and

the morphology of each NP was established in terms of their vertices and

faces. In summary, it was found that as the truncation increases:

(i) the main resonance is always blue-shifted.

(ii) the SPRs at smaller wavelength are closer

to the dominant mode, so they can be hidden.

(iii) the width of the main SPRs increases.

The optical response of complex

nanostructures can often be understood in

terms of the coupling of plasmons in

simpler components that make up the

structure. Extinction measurements have

shown that the plasmon resonance of gold

nanorings, fabricated using lithographic

techniques and latex sphere templates, is

strongly redshifted as compared to the

response of a disk with the same size. The

calculations show that this redshift is due

to increased coupling between plasmons

on the inner and outer edges of the

nanorings.

Optical Properties of Gold Nanorings. J. Aizpurua, P. Hanarp, D. S. Sutherland, M. Käll, Garnett W. Bryant, and F. J. García de Abajo. Physical Review Letters. VOLUME 90, NUMBER 5. 7 FEBRUARY 2003


The Optical Properties of Metal Nanoparticles: The Influence of Size, Shape, and Dielectric EnvironmentK. Lance Kelly, Eduardo Coronado, Lin Lin Zhao, and George C. SchatzJ. Phys. Chem. B 2003, 107, 668-677


The presence of sharp edges or tips has been shown to increase electric-

field enhancement, which is important for applications involving metal

nanoparticles as sensors.

It is also found that the corners induce more surface plasmons in a wider

energy range.

High-yield synthesis and optical response of gold nanostarsPandian Senthil Kumar, Isabel Pastoriza-Santos, Benito Rodríguez-González, F. Javier García de Abajo and Luis M Liz-MarzánNanotechnology 19 (2008)

ConclusionsConclusionsConclusionsConclusionsConclusionsConclusionsConclusionsConclusions

Metal-NP plasmonics promises to have significant impact on fastly

developing technologies. Applications currently being developed include:

nanoscale optical and infrared sensing, microscopy, and spectroscopy (the

metal NPs effectively act as nanoantennas to enhance signal emission).

Metal NPs can act as nanoantennas to collect and localize energy input.

Critical uses in medicine, for example to locally and selectively heat and kill

cancerous tumors, are already being developed. Nanoscale optical

communication along pathways defined by assemblies of coupled NPs, is

also being explored as one approach to push electronic and optical

technologies down to the nanoscale.

Gold nanoparticlesstick to cancer cellsand make them shine.

Gold nanoparticles don’tstick as well tononcancerous cells. Theresults can be seen with asimple microscope.

Mostafa El-Sayed. Georgia Tech

BibliographyBibliographyBibliographyBibliographyBibliographyBibliographyBibliographyBibliography

Nanophotonics. Prasad, Paras N. Hoboken, New Jersey : Wiley-Interscience, 2004.

Nanoparticles : from theory to application. Schmid, Günter Weinheim, Germany:

Wiley-VCH, 2004.

Nano-optics. Kawata, Satoshi, Ohtsu, Motoichi, Irie, Masahiro. Berlin: Springer, 2002.

Nanometals: formation and color. Luis M. Liz-Marzán. Review Feature.

Materials Today. February 2004.

Metal-Nanoparticle Plasmonics. Matthew Pelton, Javier Aizpurua, and Garnett Bryant.

Laser & Photonics Reviews. 2008.

Gold nanostars (digitally coloured electron microscopy images) on a background of real colour spots produced by interaction of visible light with nanoparticles of various shapes.

plasmons in different shapes ppt

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