The optical absorption of colloidal suspensions made of silver nanoparticles with polyhedral shapes is studied experimentally and theoretically. The influence of the shape on the optical response is investigated by comparing the measured absorbance with theoretical results for icosahedral, decahedral, and cuboctahedral silver nanoparticles. The theoretical spectra are obtained within the discrete dipole approximation. We find that colloidal suspensions of silver nanoparticles with a small dispersion of size distribution show very few structural shapes.

Cancer cells develop resistance to chemotherapy, and the side effects encountered seriously limit the effectiveness of treatments. For these reasons, the search for alternative therapies that target cancer cells without affecting healthy tissues is currently one of the most active areas of research on cancer. The present study focuses on a recently proposed approach for cancer cell destruction based on the targeted triggering of cancer cell spontaneous death through the mechanical vibration of anisotropic magnetic micro/nanoparticles attached to the cell membranes at low frequencies (∼20 Hz) and in weak magnetic fields (∼30 mT). The study was conducted in vitro, on human renal cancer cells with superparamagnetic-like particles. Three types of such particles made of NiFe or magnetite were prepared and characterized (either synthetic antiferromagnetic, vortex or polycrystalline with random grain anisotropy). The triggering of the apoptosis of these cancer cells was demonstrated with NiFe vortex particles and statistically characterized by flow-cytometry studies. The death pathway via apoptosis and not necrosis was identified by the clear observation of caspase activation.

We present a very efficient recursive method to calculate the effective optical response of metamaterials made up of arbitrarily shaped inclusions arranged in periodic 3D arrays. We apply it to dielectric particles embedded in a metal matrix with a lattice constant much smaller than the wavelength of the incident field, so that we may neglect retardation and factor the geometrical properties from the properties of the materials. If the conducting phase is continuous the low frequency behavior is metallic, and if the conducting paths are thin, the high frequency behavior is dielectric. Thus, extraordinary-transparency bands may develop at intermediate frequencies, whose properties may be tuned by geometrical manipulation.

We use a homogenization procedure for Maxwell's equations in order to obtain in the local limit the frequency-dependent macroscopic dielectric-response tensor ⑀ ij M ͑͒ of metamaterials made of a matrix with inclusions of any geometrical shape repeated periodically with any lattice structure. We illustrate the formalism calculating ⑀ ij M ͑͒ for several structures. For dielectric rectangular inclusions within a conducting material we obtain an anisotropic response that may change from conductorlike at low to dielectriclike with resonances at large , attaining a very small reflectance at intermediate frequencies which can be tuned through geometrical tailoring. A simple explanation allowed us to predict and confirm similar behavior for other shapes, even isotropic, close to the percolation threshold.

Silicon carbide n-type metal-oxide-semiconductor field effect transistors (MOSFETs) with different p-body acceptor concentrations were characterized by Hall effect. Normally OFF MOSFETs with good transfer characteristics and low threshold voltage were obtained with a peak mobility of ∼145 cm2 V−1 s−1 for the lowest acceptor concentration. The results are explained in terms of an increase of Coulomb scattering centers when increasing the background doping. These scattering centers are associated to fixed oxide and trapped interface charges. Additionally, the observed mobility improvement is not related to a decrease of the interface states density as a function of background doping

The effects of doping concentration and temperature upon the transport properties in the channel of lateral n-channel SiC MOSFETs have been studied using current-voltage and Hall-effect measurements. To interpret the electrical measurements, numerical TCAD simulations have been performed. A simulation methodology which includes the calculation of the Hall factor in the channel of SiC MOSFETs has been developed and applied. In addition, a new model for the bulk mobility has been suggested to explain the temperature dependence of the MOSFET characteristics with different background doping concentrations. Based on the good agreement between the simulated and measured results, scattering mechanisms in the channel of SiC MOSFETs have been studied.

We present a very efficient recursive method to calculate the effective optical response of nanostructured metamaterials made up of particles with arbitrarily shaped cross sections arranged in periodic two-dimensional arrays. We consider dielectric particles embedded in a metal matrix with a lattice constant much smaller than the wavelength. Neglecting retardation our formalism allows factoring the geometrical properties from the properties of the materials. If the conducting phase is continuous the low frequency behavior is metallic. If the conducting paths are nearly bloqued by the dielectric particles, the high frequency behavior is dielectric. Thus, extraordinary-reflectance bands may develop at intermediate frequencies, where the macroscopic response matches vacuum. The optical properties of these systems may be tuned by adjusting the geometry.Sketch of a nanostructured metamaterial slab with a dielectriclike or metallic-like behavior depending on the frequency of the incoming light.

We develop a formalism for the calculation of the macroscopic dielectric response of composite systems made of particles of one material embedded periodically within a matrix of another material, each of which is characterized by a well-defined dielectric function. The nature of these dielectric functions is arbitrary, and could correspond to dielectric or conducting, transparent or opaque, absorptive and dispersive materials. The geometry of the particles and the Bravais lattice of the composite are also arbitrary. Our formalism goes beyond the long-wavelength approximation as it fully incorporates retardation effects. We test our formalism through the study of the propagation of electromagnetic waves in two-dimensional photonic crystals made of periodic arrays of cylindrical holes in a dispersionless dielectric host. Our macroscopic theory yields a spatially dispersive macroscopic response which allows the calculation of the full photonic band structure of the system, as well as the characterization of its normal modes, upon substitution into the macroscopic field equations. We can also account approximately for the spatial dispersion through a local magnetic permeability and analyze the resulting dispersion relation, obtaining a region of left handedness.