Biomedical subjects

Peter Nordlander

Publications and source records attributed to Peter Nordlander.

8 recordsLinked to original sources

PubMed2007

Plasmonic nanostructures: artificial molecules.

This Account describes a new paradigm for the relationship between the geometry of metallic nanostructures and their optical properties. While the interaction of light with metallic nanoparticles is determined by their collective electronic or plasmon response, a compelling analogy exists between plasmon resonances of metallic nanoparticles and wave functions of simple atoms and molecules. Based on this insight, an entire family of plasmonic nanostructures, artificial molecules, has been developed whose optical properties can be understood within this picture: nanoparticles (nanoshells, nanoeggs, nanomatryushkas, nanorice), multi-nanoparticle assemblies (dimers, trimers, quadrumers), and a nanoparticle-over-metallic film, an electromagnetic analog of the spinless Anderson model.

Journal Article↗

PubMed2006

Plasmon hybridization in nanoshells with a nonconcentric core.

We apply the plasmon hybridization method to a nanoshell with a nonconcentric (offset) core and investigate how the energy and excitation cross section of the plasmon modes depend on the offset distance D of the inner core from the nanoshell center. A two-center spherical coordinate system is used for mathematical convenience. It is shown that the presence of an offset core shifts the plasmon energies and makes higher multipolar nanoshell plasmons dipole active and visible in the optical spectrum. The dependence of the plasmon shifts on D is weak for small offsets but strong for large offsets. The polarization dependence of the optical absorption spectra is found to be relatively weak. The electromagnetic field enhancements are shown to be much larger than on a concentric nanoshell. The results agree very well with results from finite difference time domain simulations.

Journal Article↗

PubMed2006

Symmetry breaking in individual plasmonic nanoparticles.

The plasmon resonances of a concentric metallic nanoshell arise from the hybridization of primitive plasmon modes of the same angular momentum on its inner and outer surfaces. For a nanoshell with an offset core, the reduction in symmetry relaxes these selection rules, allowing for an admixture of dipolar components in all plasmon modes of the particle. This metallodielectric nanostructure with reduced symmetry exhibits a core offset-dependent multipeaked spectrum, seen in single-particle spectroscopic measurements, and exhibits significantly larger local-field enhancements on its external surface than the equivalent concentric spherical nanostructure.

Electromagnetic Phenomena↗

PubMed2006

Plasmon modes of nanosphere trimers and quadrumers.

Using the plasmon hybridization method, we investigate the plasmon frequencies and optical absorption spectra of symmetric configurations of nanosphere trimers and quadrumers. Plasmon hybridization allows us to express the fundamental plasmon modes of these multinanosphere systems as linear combinations of the plasmons of individual nanospheres in a manner analogous to molecular orbital theory. We show how group theory may be used to interpret the plasmon modes of each multiparticle system as specific structure-dependent symmetric combinations of the plasmon modes of the individual nanoparticles. We compare the optical absorption spectra calculated using plasmon hybridization with the spectra obtained using finite difference time domain simulations.

Journal Article↗

PubMed2006

Nanorice: a hybrid plasmonic nanostructure.

We have designed and fabricated a new hybrid nanoparticle that combines the intense local fields of nanorods with the highly tunable plasmon resonances of nanoshells. This dielectric core-metallic shell prolate spheroid nanoparticle bears a remarkable resemblance to a grain of rice, inspiring the name "nanorice". This geometry possesses far greater structural tunability than either a nanorod or a nanoshell, along with much larger local field intensity enhancements and far greater sensitivity as a surface plasmon resonance (SPR) nanosensor than any dielectric-metal nanostructures reported previously. Invoking the plasmon hybridization picture allows us to understand the plasmon resonances of this geometry, as arising from a hybridization of the primitive plasmons of a solid spheroid and an ellipsoidal cavity inside a continuous metal.

Crystallization↗

PubMed2005

Plasmon hybridization in nanoshell dimers.

We extend the plasmon hybridization method to investigate the plasmon modes of metallic nanoshell dimers. The formalism is also generalized to include the effects of dielectric backgrounds. It is shown that the presence of dielectrics shifts the plasmon resonances of the individual nanoparticles to lower energies and screens their interaction in the dimer configuration. The net result is a redshift of dimer energies compared to the system without dielectrics and a weaker dependence of the dimer plasmon energies on dimer separation. We calculate the plasmon energies and optical absorption of nanoshell dimers as a function of dimer separation. The results are in excellent agreement with the results of finite difference time domain simulations.

Journal Article↗

PubMed2005

Controlled texturing modifies the surface topography and plasmonic properties of Au nanoshells.

We report a facile and controllable method for the postfabrication texturing of the surface topography of Au nanoshells based on site-selective chemical etching of the polycrystalline Au nanoshell surface by a bifunctional alkanethiol molecule, cysteamine. This nanoscale surface texturing process systematically introduces dramatic changes to the plasmonic properties of the Au nanoshells. The modification of the plasmon resonant properties of nanoshells as a function of increased surface roughness was examined experimentally and modeled theoretically using three-dimensional finite difference time domain (FDTD) simulations.

Letter↗

PubMed2005

Surface-enhanced Raman scattering from individual au nanoparticles and nanoparticle dimer substrates.

Surface-enhanced Raman scattering (SERS) intensities for individual Au nanospheres, nanoshells, and nanosphere and nanoshell dimers coated with nonresonant molecules are measured, where the precise nanoscale geometry of each monomer and dimer is identified through in situ atomic force microscopy. The observed intensities correlate with the integrated quartic local electromagnetic field calculated for each specific nanostructure geometry. In this study, we find that suitably fabricated nanoshells can provide SERS enhancements comparable to nanosphere dimers.

Dimerization↗