- Handbook of Nanostructured Materials and Nanotechnology
- NONLINEAR OPTICAL PROPERTIES OF QUANTUM DOTS: EXCITONS IN NANOSTRUCTURES
- Optical Properties of Nanostructured Optical Materials | Chemistry of Materials
- Optical Properties Simulation of Magneto-Plasmonic Alloys Nanostructures
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We will show how the composition of the substrate on which the particles are immobilized and the dielectric of the surrounding medium have a significant effect on the plasmon resonance of the individual particles. High SERS sensitivity for protein detection has been accomplished with semicontinuous silver films.
These surfaces are produced by vapor deposition of a metal film over nanospheres that are assembled in a hexagonally close packed arrangement. The Raman signal for AgFON electrodes is observed to be extremely stable even at extremely negative potentials in both aqueous and nonaqueous electrolytes.
Handbook of Nanostructured Materials and Nanotechnology
Recent reports have indicated that SERS enhancement factors of up to 14 orders of magnitude can be achieved, providing the sensitivity requisite for ultra trace level detection of target analytes. For this reason, we are developing a method for bacterial endospore SERS detection based on the endospores marker -- dipicolinic acid DPA. The SERS spectra of dipicolinic acid in aqueous solutions are reported. Recent experiments have shown that the effective cross sections of Raman scattering can reach the same level that of fluorescence of good laser dyes, making SERS a promising single-molecular detection tool.
The poor repeatability and controllability of these SERS substrates have prevented SERS from viable industrial applications, therefore it is imperative to design and fabricate optimized "hot spots" with desired plasmon resonance frequency in a controllable fashion. We study optical properties of these nanoburger particles by using discrete dipole approximation method. The numerical results show that nanoburger particles possess many advantages over single layered particles, including high brightness or scattering intensity, high local field enhancements, and more freedom of tuning plasmon resonance wavelength.
Synthesis and characterization of gold nanoparticle aggregates as novel substrates for surface-enhanced Raman scattering Author s : Adam M. Schwartzberg ; Chris D. Grant ; A. Wolcott ; R. Bogomolni; Jin Z. Zhang Show Abstract. Novel gold nanoparticle aggregates have been synthesized using simple colloidal chemistry techniques. The electronic absorption spectra of the aggregates can be manipulated by controlling the synthetic conditions.
The aggregates have been demonstrated for the first time to exhibit strong activity for surface-enhanced Raman scattering SERS. SERS studies were performed using rhodamine 6G R6G , a molecule which normally does not show SERS enhancement on gold surfaces, showed an enhancement factor on the order of 10 9 , which is similar to or better than most ensemble averaged SERS enhancement factors reported to date.
The results demonstrate that these gold nanoparticle aggregates are promising for SERS applications in detection and analysis of molecules. Smith ; Sheldon Schultz Show Abstract. Nano gold particles interact strongly with visible light to excite the collaborative oscillation of conductive electrons within nano particles resulting in a surface plasmon resonance which makes them useful for various applications including bio-labeling. In this paper, we study the effect of particle sizes with particle plasmon resonant wavelength and the coupling between pair of elliptical metallic disks and ellipsoid particles by simulations and experiments.
The red-shift resonant peak wavelength of coupled particles to that of single particle is due to particle plasmons near-field coupling. The shift decays is approximately exponentially with increasing particle spacing, and reaches zero when the gap between the two particles exceeds about 2. It is also found that the exponential decay of peak shift with particle gap is size independent but shape dependent.
Recent theoretical works have suggested the possibility of constructing a diffraction-free lens by using a negative refractive index medium NRIM. The key theoretical proposition is that evanescent waves can be greatly enhanced by increasing the thickness of the NRIM. We present here experimental evidence on enhanced transmission of evanescent waves via surface plasmon at a thin silver film operating near surface plasma resonant frequency. We found the transmission of evanescent waves rapidly grows with the film thickness up to about 50 nm, after which it decays as loss becomes significant.
These findings represent the first step toward the understanding and realization of a diffraction-free lens by using NRIM. Applications of surface plasmon and phonon polaritons to developing left-handed materials and nano-lithography Author s : Gennady Shvets Show Abstract.
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Despite recent successes in making left-handed materials in the microwave frequency range, there has been little progress in achieving same for infrared frequencies. A novel approach to making a material with negative index of refraction using photonic crystals made of dielectric components with a small of order minus one negative dielectric permittivity has recently been proposed.
Periodic structures with negative-epsilon dielectrics support surface waves which can have a negative group velocity.
NONLINEAR OPTICAL PROPERTIES OF QUANTUM DOTS: EXCITONS IN NANOSTRUCTURES
The nature of these surface waves depends on the dielectric components:they are surface plasmons for plasmonic materials such as metals or surface phonon polaritons for polar crystals such as SiC,ZnSe,GaP with the reststrahlen band. The advantages of using phononic materials long phonon lifetime,scientifically important frequency range will be illustrated. Depending on the photonic lattice square or hexagonal , the resulting meta-material can be either isotropic,or strongly anisotropic.
Another application of the negative-epsilon materials is nano-lithography. As was suggested earlier Pendry ,Shen and Platzman , any material with formula available in paper can be used to significantly enhance near-field imaging.
Optical Properties of Nanostructured Optical Materials | Chemistry of Materials
It is shown that a thin slab of SiC is capable to focus the Analytic calculations of the fields in the focus of such slab are presented, and parametric dependence on the slab width and phonon lifetime explored. Finite difference time-domain studies of optical properties of nanoshell structures Author s : Chris Oubre ; Peter J. Nordlander Show Abstract. The method provides a convenient approach for calculating several physical properties of nanoshells based structures including the optical absorption and scattering cross sections as well as the local electromagnetic fields near the nanoshell surfaces.
The method is applied to silver and gold nanoshells and nanoshell dimers. Comparisons with classical Mie scattering are presented. Optical properties of crossed metallodielectric gratings Author s : Jennifer M. Steele; Cristin E. Moran ; Allen Lee; Naomi J. Halas Show Abstract.
In this paper we report an experimental and theoretical study of the optical properties of metallodielectric gratings with subwavelength gaps in the thin metal limit. A mask-free method of fabrication for large area submicron silver gratings on silica substrates has been developed using soft-lithographic techniques. By measuring the zeroth-order transmission of these gratings, both an edge anomaly associated with the Rayleigh wavelength and a resonant anomaly associated with the excitation of surface plasmons SPs are observed.
A crossed grating configuration is studied: the presence of the additional crossed grating results in a dramatic widening of the plasmonic band gap relative to that of a 1D grating. Investigation of the spectra of coupled polaritons on the periodically modulated metallic layer and narrow regions of anomalous transparency Author s : Alexandre V. The optical properties of magneto-plasmonic nanostructures are a current subject of research with fast-growing experimental and theoretical activities.
Optical Properties Simulation of Magneto-Plasmonic Alloys Nanostructures
In this article, we investigated the optical response of Ag—Fe, Au—Fe, and Ag—Fe—Au bimetallic and trimetallic alloy nanostructures as a function of size, shape, and composition by using discrete dipole approximation DDA method. We observed that the localized surface plasmon resonance LSPR peak position in considered alloy nanostructures is enhanced by changing the particle size and shape, further strongly affected by rectangular shape in comparison to prolate, cube, triangular, and spherical shapes.
It has been found that the rectangular shape nanostructure show enhancement to LSPR peaks and their corresponding efficiencies in comparison to prolate, cube, triangular, and spherical shapes.
The effect of size and shape on relative efficiency has also been studied. An increasing number of peaks appear in the optical spectra of considered nanostructures with higher gold concentration and show a broadening of LSPR peaks. Furthermore, it has been found that the optical response of alloys can be enhanced by varying the metal composition. The obtained results indicate the potential use of suitable magnetic-plasmonic nanostructures in medical diagnostics and biological imaging. The author, Pradeep Bhatia, thanks B.
Draine and P. Pradeep Bhatia is also very thankful to S. The optical absorption of the Au nanoparticle deposited onto glass substrates was characterized by a Cary UV-visible spectrophotometer. Investigation of the effect of thermal annealing on the nanoparticle optical properties was performed by measuring the absorption spectra in the UV-VIS spectral range for different samples at increasing annealing time.
The experimental setup with the relative signal data processing is designed in such a way that either optical and MO excitation is achievable on the same sample. In particular, MO signal in transversal configuration is obtained by the external modulation of magnetic field, namely with magnetic field applied parallel to the sample plane and perpendicular to the light incidence plane.
A monochromator is placed between the source of light and the sample, allowing the analysis of plasmonic and MO effect as a function of wavelength.