We have demonstrated a method of fabricating long-range arrays of 2D metallic microstructures on glass surfaces and measured the optical resonances of those structures. Gold and silver stripes are fabricated using microcontact printing with PDMS gratings and electroless plating techniques without the use of resist masks or etching. Changing the blaze angle and periodicity of the gratings used to make the PDMS stamps varies the line widths. The optical response of these fabricated transmission gratings was evaluated by measuring the transmission spectra while varying the angle of the incident light.

We have recently proposed a new approach to optical lithography that could be used to replicate arrays of metal nanoparticles using broad beam illumination with visible light and standard photoresist. The method relies on resonant excitation of the surface plasmon oscillation in the nanoparticles. When excited at the surface plasmon frequency, a resonantly enhanced dipole field builds up around the nanoparticles. This dipole field is used to locally expose a thin layer of photoresist, generating a replica of the original pattern in the resist. Silver nanoparticles on photoresist can be resonantly excited at wavelengths ranging from 410 nm to 460 nm, allowing for resonantly enhanced exposure of standard g-line photoresist. Finite Difference Time Domain (FDTD) simulations of isolated silver particles on a thin resist layer show that broad beam illumination with p-polarized light at a wavelength of 439 nm can produce features as small as 30 nm, or λ/14. Depending on exposure time lateral spot sizes ranging from 30 to 80 nm with exposure depths ranging from 12 to 45 nm can be achieved. We discuss the effect of particle-particle interactions in the replica formation process. Experiments on low areal density Ag nanoparticle arrays are discussed. Resist layers (thickness 75 nm) in contact with 40 nm Ag nanoparticles were exposed using 410 nm light and were subsequently developed. Atomic Force Microscopy on these samples reveals nanoscale depressions in the resist, providing evidence for plasmon-enhanced resist exposure.

A phenomenon was observed in our laboratory as we studied the effect of chain length of fatty amine capped on the nanogold upon their 2D arrangement. The nanogolds modified with C₁₂NH₂, C₁₆NH₂, C₁₈NH₂ have been used in this investigation and were arranged by the method of LB technique. Electronmicrograms showed that the length of aggregates is proportional to the chain length of the capped amine C_nNH₂. The longer the chain length is, the straighter the aggregates will be and the more compact 2D arrangement could be formed. Linear aggregates has been found in the 2D pattern formation of nanoparticles without template, and these kinds of aggregates might be of great importance in the formation of 2D arrangement of nanoparticles.

We report a surprising chemical reactivity of gold nanoshells with carbon tetrachloride. Gold nanoshells are nanoparticles constructed from a silica core encapsulated in a gold shell. An aminoalkoxysilane linker molecule is used to derivatize the silica surface, which facilitates the attachment of the gold shell. Evidence is shown for the decomposition of the gold shell due to a reaction with carbon tetrachloride. The reaction is believed to proceed through the formation of a charge transfer complex between carbon tetrachloride and the gold-amine complex. The reaction is facilitated by the presence of defects in the shell layer.

Monodispersed superparamagnetic nanoparticles were synthesized from aqueous iron chloride solutions and were modified with poly(ethylene glycol) self assembled monolayers to improve their dispersion, biocompatibility and intracellular uptake for biomedical applications. Transmission electron micrographs (TEM) and atomic force microscopy (AFM) showed an average particle size of 10-30 nm and confirmed particle dispersion following surface modification with PEG. Fourier transform infrared spectroscopy (FTIR) confirmed the presence of PEG on the nanoparticle surface and the particles were further characterized with electron energy loss spectroscopy (EELS).

The large scattering cross section of plasmon resonant gold and silver nanoparticles functionalized with the appropriate ligand allows for sensitive and specific detection of nucleic acids and proteins. By varying the size, shape, and material morphology populations with a specific peak plasmon resonance can be prepared. By varying the order and length of plasmon resonant bar segment in a composite nanowire one can obtain a large number of particle populations. Distinct populations can be used for labels for multiplexing or as a platform for biological assays. An larger number of color populations can be obtained with composite nanowires that are fabricated with various lengths of silver, gold, or nickel segments. The order and length of the different plasmon resonance rod segments can be used to uniquely identify a rod population allowing for a large degree of multiplexing within a single sample.

Ultra-fast time-resolved fluorescence spectroscopy has been used to probe the emission properties in gold nanospheres and nanorods. The decay of the emission was found to be on the order of ~40 fs for both the gold nanorods and nanospheres. Measurements of the ultra-fast anisotropy decay suggest that the emission is depolarized on a very fast time-scale. The spectrum of the ultra-fast emission in the nanostructures is provided. The gold nanorods show an enhanced ultra-fast emission spectrum in the vicinity of the longitudinal surface plasmon resonance in comparison to the nanospheres.

Two different laser techniques for producing tungsten-based nanoparticles have been compared in this investigation. The particles were produced by Laser assisted Chemical Vapor Deposition (LCVD) from WF₆/H₂/Ar gas mixtures, and by Pulsed Laser Ablation (PLA) of a solid W target in N₂ atmosphere, respectively. An ArF excimer laser (λ = 193 nm) was used as the light source for both methods. The ablation was performed at atmospheric pressure which allowed for direct size-distribution determination by a Differential Mobility Analyzer (DMA), and a subsequent deposition of size-selected monodisperse particles. The deposits were characterized by using TEM, SEM, XRD, and XPS techniques. Optical emission spectroscopy was capable of monitoring the temperature of the particles by measuring the emitted thermal radiation from the laser-excited nanoparticles during LCVD. Strong evaporation, due to high temperature of the particles, affects the size-distribution as the laser fluence is increased. Coagulation widens and alters the size-distribution as the partial pressure of WF₆ is increased; according to TEM analysis of the deposits. Lognormal distribution was found at low WF₆ partial pressures. However, laser ablation at fluences below the ablation threshold yielded a non-lognormal size-distribution with a continuous decreasing occurrence as the particle diameter increased in the observed size-window (7-133 nm in diameter). Crystalline (β-phase) particles could be formed by LCVD, but only amorphous WN_x (x~0.3) particles were obtained by PLA in a N₂ ambient. The differences in size-distributions and crystallinity for LCVD- and PLA-produced particles are discussed on a basis that diverse mechanisms lead to particle formation.

In this paper, we will present the experimental results of the microwave properties of BaTiO₃ and BaTiO₃-Pt composites. These composites materials were designed to increase the effective dielectric constant at microwave frequency. Three different platinum volume fractions were used, 3, 5 and 10%, to make BaTiO₃-Pt composites, in addition to a pure BaTiO₃ material. To characterize the BaTiO₃-Pt composites, microwave measurements were conducted using the waveguide transmission measurements. The experimental results verify that it is possible to increase the dielectric constant using the conductor loading method.

Photodecomposition by pulsed UV laser irradiation of metal acetylacetonate (MeAcAc) crystals which are embedded in polymethylmetacrylate (PMMA) films is investigated by scanning (SEM)- and transmission (TEM)- electron microscopy. The photodecomposition occurs at and above a laser fluence threshold of 50 mJ/cm². Observations after irradiation performed under different condition, either in air or in vacuum, suggest that metal cluster formation develops in atmosphere upon PMMA ablation and MeAcAc decomposition. These clusters serve further as excellent catalytic centers for electroless metal plating, which develops at the irradiated sample surface.

We investigate the possibility of using arrays of closely spaced metal nanoparticles as plasmon waveguides for electromagnetic energy below the diffraction limit of light. Far-field spectroscopy on arrays of closely spaced 50 nm Au particles fabricated using electron beam lithography reveals the presence of near-field optical particle interactions that lead to shifts in the plasmon resonance frequencies for longitudinal and transverse excitations. We link this observation to a point-dipole model for energy transfer in plasmon waveguides and give an estimate of the expected group velocities and energy decay lengths for the fabricated structures. A near-field optical excitation and detection scheme for energy transport is proposed and demonstrated. The fabricated structures show a high propagation loss of about 3 dB / 15 nm which renders a direct experimental observation of energy transfer impossible. The nature of the loss and ways to decrease it by an order of magnitude are discussed. We also present finite-difference time-domain simulations on the energy transfer properties of plasmon waveguides.

Systematic variation of the internal geometry of a dielectric core-metal shell nanoparticle allows the local electromagnetic field at the nanoparticle surface to be precisely controlled. The strength of the field as a function of core and shell dimension is measured by monitoring the Surface-Enhanced Raman Scattering (SERS) response of nonresonant molecular adsorbates (para-mercaptoaniline) bound to the nanoparticle surface. The SERS enhancement appears to be directly controllable by nanoparticle geometry. A series of silica core-silver shell nanoparticles were constructed using 65 nm and 79 nm cores, upon which silver layers ranging from 5 nm to 20 nm were deposited by an electroless plating method. Raman spectra of nanoshell and adsorbate molecule solutions were obtained at an excitation of 1.0 μm (Nd:YAG). The magnitude of three predominant Stokes modes (390cm^-1, 1077cm^-1, and 1590cm^-1) were theoretically calculated and experimentally measured as a function of nanoshell geometry. The excellent agreement observed between experiment and classical theory indicates that metal nanoshells provide a substrate with a controllable optical near field.

The electronic structure and optical properties of metallic nanoshells are calculated using a jellium model and the local density approximation. An efficient implementation of the local density method enables applications to nanoshells with a very large number of conduction electrons. The frequency dependent polarizabilities of nanoshells are calculated using the time-dependent local density formalism. The optical response of these systems is characterized by both single particle and collective plasmon excitations. The energies of the plasmon resonances are calculated for different sizes of the metallic nanoshells and for different dielectric embedding media and nanoshell cores. The results are compared with results obtained using classical Mie scattering and the results from a semiclassical model.

Polymer/MX₂ layered nanocomposites containing organic polymers between the inorganic sheets of the host lattice have been synthesized by using the exfoliation-adsorption method. The temperature dependences of the electrical resistivities of polymer/MX₂ nanocomposites down to 10 K were characterized. Electron transfer in PEI/MoS₂ nanocomposite showed the three-dimensional variable rang hopping, while polymer/1T-TaS₂ nanocomposites showed semiconductor-like behavior, but which was found to be different from the standard variable range hopping model.