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Au and Ag nanoshells are investigated as substrates for surface-enhanced Raman scattering (SERS). We find that SERS enhancements on nanoshell films are dramatically different from those observed on colloidal aggregates, specifically that the Raman enhancement follows the plasmon resonance of the individual nanoparticles. Comparative finite difference time domain calculations of fields at the surface of smooth and roughened nanoshells reveal that surface roughness contributes only slightly to the total enhancement. SERS enhancements as large as 2.5 x [10.sup.10] on Ag nanoshell films for the nonresonant molecule p-mercaptoaniline are measured.

Metal nanoshells are a class of nanoparticles with tunable optical resonances. In this article, an application of this technology to thermal ablative therapy for cancer is described. By tuning the nanoshells to strongly absorb light in the near infrared, where optical transmission through tissue is optimal, a distribution of nanoshells at depth in tissue can be used to deliver a therapeutic dose of heat by using moderately low exposures of extracorporeally applied near-infrared (NIR) light. Human breast carcinoma cells incubated with nanoshells in vitro were found to have undergone photothermally induced morbidity on exposure to NIR light (820 nm, 35 W/[cm.sup.2]), as determined by using a fluorescent viability stain. Cells without nanoshells displayed no loss in viability after the same periods and conditions of NIR illumination. Likewise, in vivo studies under magnetic resonance guidance revealed that exposure to low doses of NIR light (820 nm, 4 W/[cm.sup.2]) in solid tumors treated with metal nanoshells reached average maximum temperatures capable of inducing irreversible tissue damage ([delta]T = 37.4 [+ or -] 6.6[degrees]C) within 4-6 min. Controls treated without nanoshells demonstrated significantly lower average temperatures on exposure to NIR light ([delta]T < 10[degrees]C). These findings demonstrated good correlation with histological findings. Tissues heated above the thermal damage threshold displayed coagulation, cell shrinkage, and loss of nuclear staining, which are indicators of irreversible thermal damage. Control tissues appeared undamaged.

We present a simple and intuitive picture, an electromagnetic analog of molecular orbital theory, that describes the plasmon response of complex nanostructures of arbitrary shape. Our model can be understood as the interaction or 'hybridization' of elementary plasmons supported by nanostructures of elementary geometries. As an example, the approach is applied to the important case of a four-layer concentric nanoshell, where the hybridization of the plasmons of the inner and outer nanoshells determines the resonant frequencies of the multilayer nanostructure., The fabrication of materials on a nanoscale can be used to enhance and exploit properties that become stronger under conditions of reduced dimensionality. In metallic systems, the conduction electron charge [...]

A rapid immunoassay capable of detecting analyte within complex biological media without any sample preparation is described. This was accomplished using gold nanoshells, layered dielectric-metal nanoparticles whose optical resonance is a function of the relative size of its constituent layers. Aggregation of antibody/nanoshell conjugates with extinction spectra in the near-infrared was monitored spectroscopically in the presence of analyte. Successful detection of immunoglobulins was achieved in saline, serum, and whole blood. This system constitutes a simple immunoassay capable of detecting sub-nanogram-per-milliliter quantities of various analytes in different media within 10-30 min.

The experimental and theoretical aspects of the interaction of gold nanoshells on a waveguiding structure are studied. The result reveals that the light scattering spectrum of the nanoshells is modified because of the presence of an underlying waveguiding structure.

Self-assembling and electronic properties of unsymmetrical disulfides adsorbed onto Au(111) have been studied. Results include analysis of self-assembled monolayers that have been derived from fullerene disulfides.

Low-temperature scanning tunneling microscopy was used in studying the anisotropic scattering from point defects on the surface of graphite. The experiments were done using an ultrahigh-vacuum STM at 77 K. The experimental results obtained were in close agreement with theoretical calculations made by Mizes and Foster. The images are similar with those of three-fold scattering using a C60-functionalized probe tip at room temperature.

The scanning tunneling microscope (STM) has been used to observe threefold symmetric electron scattering from point defects on a graphite surface. These theoretically predicted electronic perturbations could not be observed with a bare metal tip but could only be imaged when a fullerene ([C.sub.60]) molecule was adsorbed onto the tunneling region (apex) of an STM tip. Functionalizing an STM tip with an appropriate molecular adsorbate alters the density of states near the Fermi level of the tip and changes its imaging characteristics., The STM has recently enabled scientists to image local surface electronic phenomena on the nanometer scale. On metal surfaces, the STM has been used to image scattering of surface-state electrons [...]

The production of silica core-silver nanoparticles by using different chemical methods like the methods of Danscher, Burry and Zsigmondy is described, where each method helps in producing a silver outer layer with a unique morphology. Results indicate that the reduction of silver on the nanometer scale depends on the chemical stabilizers and the pH of the reaction involved.

Examines the infrared extinction properties of gold nanoshells. Strong optical resonance depending on their core radius and shell thickness displayed by the gold nanoshells; Resolution of multipolar plasmon resonances in the extinction spectra; Additional resonances due to particle aggregation observed; Frequency agile infrared properties of the nanoparticles.

Studies light scattering from dipole and quadrupole nanoshell antennas. Structures of the nanoshells; Construction of nanoshell antennas; Coupling of the antennas to incident electromagnetic waves; Applications in the remote coupling of electromagnetic signals into nanoscale machines or devices.

Characterizes the diffusion process of silver (Ag) atoms in fullerene solid thin films. Correlation between temperature and diffusion; Implications of Ag and fullerene interdiffusion for the formation of fullerene/metal contacts or layered materials; Formation of an impurity band in solid fullerene.

Analyzes a series of subpicosecond time-resolved reflectivity measurements in n-type gallium arsenide (GaAs) interfaces at photoexcitation densities. Dependence of reflectivity signal to interface preparation; Preparation of GaAs surface; Changes in the space-charge field of GaAs.