We evaluate the potential of inserting metallic, metal-dielectric core-shell, and fully dielectric nanoparticles in ultrathin chalcopyrite solar cells to enhance absorption which experiences a significant drop for absorber thicknesses below 500 nm. For different integration positions at the front or at the rear of the solar cell structure theoretical expectations and potential benefits originating from light scattering, near-field enhancement and coupling into waveguide modes by the nanoparticles are presented. These benefits are always balanced against experimental challenges arising for particular geometries due to the very specific fabrication processes of chalcopyrite solar cells. In particular high absorber deposition temperatures as well as contact layers that are relatively thick compared to other devices need to be considered. Based on this, we will need to go beyond some geometries that have proven beneficial for other types of solar cells and identify the most promising configurations for chalcopyrite-based devices.

Ag–TiO2 hybrids are useful in various applications, such as photocatalysis, solar energy conversion, and biosensoring. In this study, oil-decorated TiO2 films were used to induce the formation of Ag nanoplates in AgNO3 solution via a photocatalytic method. Ag nanoplates in the products can be controlled by changing the oil-decoration time of films or changing the AgNO3 concentration of the solution. Oil decoration was found to be necessary in the formation of Ag nanoplates, and a critical concentration of AgNO3 solution was needed. The oil layer on the TiO2 films was demonstrated to play a role in the prevention of the reoxidation of the Ag atoms, and a growth model was proposed to interpret the formation of Ag nanoplates on the oil-decorated TiO2 films.

Energy resolution is one of the most important parameters in electron energy-loss spectroscopy. This is especially true for measurement of surface plasmon resonances, where high-energy resolution is crucial for resolving individual resonance peaks, in particular close to the zero-loss peak. In this work, we improve the energy resolution of electron energy-loss spectra of surface plasmon resonances, acquired with a monochromated beam in a scanning transmission electron microscope, by the use of the Richardson–Lucy deconvolution algorithm. We test the performance of the algorithm in a simulated spectrum and then apply it to experimental energy-loss spectra of a lithographically patterned silver nanorod. By reduction of the point spread function of the spectrum, we are able to identify low-energy surface plasmon peaks in spectra, more localized features, and higher contrast in surface plasmon energy-filtered maps. Thanks to the combination of a monochromated beam and the Richardson–Lucy algorithm, we improve the effective resolution down to 30 meV, and evidence of success up to 10 meV resolution for losses below 1 eV. We also propose, implement, and test two methods to limit the number of iterations in the algorithm. The first method is based on noise measurement and analysis, while in the second we monitor the change of slope in the deconvolved spectrum.

Nanoshells, concentric nanoparticles consisting of a dielectric core and a metallic shell, are simple spherical nanostructures with unique, geometrically tunable optical resonances. As with all metallic nanostructures, their optical properties are controlled by the collective electronic resonance, or plasmon resonance, of the constituent metal, typically silver or gold. In striking contrast to the resonant properties of solid metallic nanostructures, which exhibit only a weak tunability with size or aspect ratio, the optical resonance of a nanoshell is extraordinarily sensitive to the inner and outer dimensions of the metallic shell layer. The underlying reason for this lies beyond classical electromagnetic theory, where plasmon-resonant nanoparticles follow a mesoscale analogue of molecular orbital theory, hybridizing in precisely the same manner as the individual atomic wave functions in simple molecules. This plasmon hybridization picture provides an essential “design rule” for metallic nanostructures that can allow us to effectively predict their optical resonant properties. Such a systematic control of the far-field optical resonances of metallic nanostructures is accomplished simultaneously with control of the field at the surface of the nanostructure. The nanoshell geometry is ideal for tuning and optimizing the near-field response as a stand-alone surface-enhanced Raman spectroscopy (SERS) nanosensor substrate and as a surface-plasmon-resonant nanosensor.Tuning the plasmon resonance of nanoshells into the near-infrared region of the spectrum has enabled a variety of biomedical applications that exploit the strong optical contrast available with nanoshells in a spectral region where blood and tissue are optimally transparent.

One-dimensional metallic nanostructures such as nanorods and nanowires are of tremendous interest for electronic, sensing, and catalytic applications. Shape anisotropy introduces new optical properties in gold and silver nanoparticles, such as longitudinal plasmon resonance bands in the visible and near-IR portion of the spectrum. Different approaches employed for the shape-controlled synthesis of silver and gold nanocrystals include chemical, electrochemical, and physical methods. The chemical route for the synthesis of nanorods and nanowires, in which metal salts are reduced in an aqueous solution, is one of the most widely used methods. This route commonly employs a surfactant as the directing agent to introduce asymmetry in the nanocrystal shape. Variation in the concentration of precursor salt and the surfactant, the nature of the surfactant, the nature and concentration of reducing agents, the presence of external salts, and the pH of the reaction solution all affect nanocrystal shape, dimension, and yield. The size and shape of the nanocrystals affect the position of the plasmon bands, which in turn has been widely used in surface-enhanced spectroscopies that include both Raman and fluorescence. The aqueous, surfactant-directed route also promises the synthesis of more complex nanostructures with additional desirable properties.

This article provides a brief account of solution-phase methods that generate silver and gold nanostructures with well-controlled shapes. It is organized into five sections: The first section discusses the nucleation and formation of seeds from which nanostructures grow. The next two sections explain how seeds with fairly isotropic shapes can grow anisotropically into distinct morphologies. Polyol synthesis is selected as an example to illustrate this concept. Specifically, we discuss the growth of silver nanocubes (with and without truncated corners), nanowires, and triangular nanoplates. In the fourth section, we show that silver nanostructures can be transformed into hollow gold nanostructures through a galvanic replacement reaction. Examples include nanoboxes, nanocages, nanotubes (both single- and multi-walled), and nanorattles. The fifth section briefly outlines a potential medical application for gold nanocages.We conclude with some perspectives on areas for future work.