Interpretation of X-ray Powder Diffraction Patterns . By H. Lipson and H. Steeple. Pp. viii + 335 + 3 plates. (Mac-millan: London; St Martins Press: New York, May 1970.) £4.

X-Ray Diffraction

Understanding how light interacts with matter at the nanometre scale is a fundamental issue in optoelectronics and nanophotonics. In particular, many applications (such as bio-sensing, cancer therapy and all-optical signal processing) rely on surface-bound optical excitations in metallic nanoparticles. However, so far no experimental technique has been capable of imaging localized optical excitations with sufficient resolution to reveal their dramatic spatial variation over one single nanoparticle. Here, we present a novel method applied on silver nanotriangles, achieving such resolution by recording maps of plasmons in the near-infrared/visible/ultraviolet domain using electron beams instead of photons. This method relies on the detection of plasmons as resonance peaks in the energy-loss spectra of subnanometre electron beams rastered on nanoparticles of well-defined geometrical parameters. This represents a significant improvement in the spatial resolution with which plasmonic modes can be imaged, and provides a powerful tool in the development of nanometre-level optics.

Mapping surface plasmons on a single metallic nanoparticle

Multi-wavelength light is directed to an optic including a substrate and achromatic metasurface optical components deposited on a surface of the substrate. The achromatic metasurface optical components comprise a pattern of dielectric resonators. The dielectric resonators have nonperiodic gap distances between adjacent dielectric resonators; and each dielectric resonator has a width, w, that is distinct from the width of other dielectric resonators. A plurality of wavelengths of interest selected from the wavelengths of the multi-wavelength light are deflected with the achromatic metasurface optical components at a shared angle or to or from a focal point at a shared focal length.

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Achromatic Metasurface Optical Components by Dispersive Phase Compensation

Localized surface plasmon resonance (LSPR) in semiconductor nanocrystals (NCs) that results in resonant absorption, scattering, and near field enhancement around the NC can be tuned across a wide optical spectral range from visible to far-infrared by synthetically varying doping level, and post synthetically via chemical oxidation and reduction, photochemical control, and electrochemical control In this review, we will discuss the fundamental electromagnetic dynamics governing light matter interaction in plasmonic semiconductor NCs and the realization of various distinctive physical properties made possible by the advancement of colloidal synthesis routes to such NCs Here, we will illustrate how free carrier dielectric properties are induced in various semiconductor materials including metal oxides, metal chalcogenides, metal nitrides, silicon, and other materials We will highlight the applicability and limitations of the Drude model as applied to semiconductors considering the complex band structures 

Localized Surface Plasmon Resonance in Semiconductor Nanocrystals

The incessant demand for energy forces us to seek it from sustainable resources; and concerns on environment demands that resources should be clean as well. Metal oxide semiconductors, which are stable and environment friendly materials, are used in photovoltaics either as photoelectrode in dye solar cells (DSCs) or to build metal oxide p–n junctions. Progress made in utilization of metal oxides for photoelectrode in DSC is reviewed in this article. Basic operational principle and factors that control the photoconversion efficiency of DSC are briefly outlined. The d-block binary metal oxides viz. TiO2, ZnO, and Nb2O5 are the best candidates as photoelectrode due to the dissimilarity in orbitals constituting their conduction band and valence band. This dissimilarity decreases the probability of charge recombination and enhances the carrier lifetime in these materials. Ternary metal oxide such as Zn2SnO4 could also be a promising material for photovoltaic application. Various morphologies such as nanoparticles, nanowires, nanotubes, and nanofibers have been explored to enhance the energy conversion efficiency of DSCs. The TiO2 served as a model system to study the properties and factors that control the photoconversion efficiency of DSCs; therefore, such discussion is limited to TiO2 in this article. The electron transport occurs through nanocrystalline TiO2 through trapping and detrapping events; however, exact nature of these trap states are not thoroughly quantified. Research efforts are required not only to quantify the trap states in mesoporous metal oxides but new mesoporous architectures also to increase the conversion efficiency of metal oxide-based photovoltaics.

Metal Oxides for Dye-Sensitized Solar Cells

Control of the polarization distribution of light allows tailoring the electromagnetic response of plasmonic particles. By rigorously extending the generalized multiparticle Mie theory, we show that focused cylindrical vector beams (CVB) can be used to efficiently excite dark plasmon modes in nanoparticle clusters. In addition to the small radiative damping and large field enhancement associated to dark modes, excitation with CVB can give place to unusual phenomenology like the formation of electromagnetic cold spots and the generation of Fano resonances in highly symmetric clusters. Overall, the results show the potential of CVB to tailor the plasmonic response of nanoparticle clusters in a unique way.

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Dark modes and Fano resonances in plasmonic clusters excited by cylindrical vector beams.

Metallic nanostructures have received great attention due to their ability to generate surface plasmon resonances, which are collective oscillations of conduction electrons of a material excited by an electromagnetic wave. Plasmonic metal nanostructures are able to localize and manipulate the light at the nanoscale and, therefore, are attractive building blocks for various emerging applications. In particular, hollow nanostructures are promising plasmonic materials as cavities are known to have better plasmonic properties than their solid counterparts thanks to the plasmon hybridization mechanism. The hybridization of the plasmons results in the enhancement of the plasmon fields along with more homogeneous distribution as well as the reduction of localized surface plasmon resonance (LSPR) quenching due to absorption. In this review, we summarize the efforts on the synthesis of hollow metal nanostructures with an emphasis on the galvanic replacement reaction. In the second part of this review, we discuss the advancements on the characterization of plasmonic properties of hollow nanostructures, covering the single nanoparticle experiments, nanoscale characterization via electron energy-loss spectroscopy and modeling and simulation studies. Examples of the applications, i.e. sensing, surface enhanced Raman spectroscopy, photothermal ablation therapy of cancer, drug delivery or catalysis among others, where hollow nanostructures perform better than their solid counterparts, are also evaluated.

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Hollow metal nanostructures for enhanced plasmonics: synthesis, local plasmonic properties and applications

The optical activity of fabricated metallic nanostructures is investigated by complete polarimetry. While lattices decorated with nanoscale gammadia etched in thin metallic films have been described as two dimensional, planar nanostructures, they are better described as quasi-planar structures with some three dimensional character. We find that the optical activity of these structures arises not only from the dissymmetric backing by a substrate but, more importantly, from the selective rounding of the nanostructure edges. A true chiroptical response in the far-field is only allowed when the gammadia contain these non-planar features. This is demonstrated by polarimetric measurements in conjunction with electrodynamical simulations based on the discrete dipole approximation that consider non-ideal gammadia. It is also shown that subtle planar dissymmetries in gammadia are sufficient to generate asymmetric transmission of circular polarized light.

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Relation between 2D/3D chirality and the appearance of chiroptical effects in real nanostructures.

The width of the surface plasmon resonance of metallic particles increases as the particle size reduces due to confinement effects that modify the metal dielectric function. In the limit of very low particle concentration, particle size can be directly related to the plasmon width. However, as concentration increases, the interaction among particles induces additional broadening. Numerical computation of the effective dielectric function of systems consisting of monodisperse and randomly distributed particles embedded in a dielectric matrix enable us to quantify the influence of both size and interaction effects. It is shown that for noble metals the contribution of interparticle interaction to plasmon resonance width cannot be neglected even at volume concentrations of a few per cent. The results presented here can be useful in extending nanoparticle sizing from optical extinction spectroscopy beyond the dilute limit required by classical Mie theory.

http://iopscience.iop.org/article/10.1088/0957-4484/20/23/235706/pdf

Surface plasmon resonance broadening of metallic particles in the quasi-static approximation: a numerical study of size confinement and interparticle interaction effects.

Jordi Sancho-Parramon

Papers

Dark modes and Fano resonances in plasmonic clusters excited by cylindrical vector beams.

Hollow metal nanostructures for enhanced plasmonics: synthesis, local plasmonic properties and applications

Relation between 2D/3D chirality and the appearance of chiroptical effects in real nanostructures.

Surface plasmon resonance broadening of metallic particles in the quasi-static approximation: a numerical study of size confinement and interparticle interaction effects.

Optical properties of gold island films : a spectroscopic ellipsometry study