Nanomaterials simulation

Optical properties of a three-dimensional composite medium consisting of an amplifying matrix with inclusion of silver nanoparticles of various shapes are investigated theoretically. Behaviour of the amplification coefficient of active component required for compensating energy dissipation at metal inclusions is studied. Results of exact electrodynamical calculations of conditions for obtaining the unit refractive index and that performed using electrostatic approximation (Maxwell-Garnett approach) are compared

Finite element models of single-walled and multi-walled carbon nanotubes in their perfect and fundamental forms (zigzag and armchair) were constructed. Then, after obtaining the mechanical properties of perfect carbon nanotubes, three types of imperfections, ie, doping with Si atoms, carbon vacancy and perturbation of the ideal location of the carbon atom were introduced in different amounts to the perfect models to make them imperfect. Finally, the mechanical properties of the imperfect carbon nanotubes were numerically simulated and ...

Using the Maxwell-Garnett model, a complex effective index of refraction of a matrix metal-dielectric composite medium with silver inclusions of spheroidal shape is investigated. A possibility of observing the unit refractive index in the visible spectral region is shown, with the effective absorption coefficient being less than 0.1. The results of analytical calculations based on the electrodynamic Maxwell-Garnett model are compared with those obtained by an exact electrodynamic calculation.

It is theoretically shown that a thin composite slab comprised of a transparent host and uniformly oriented disc-like silver nanoparticles deposited onto a glass surface can act as an anti-reflection coating. The applicability of the effective-medium model for describing the optical properties of thin heterogeneous layers with moderate volume fraction of inclusions is verified using full-wave finite-element simulations.

A design of ultrathin composite layer with metal nanoparticles on a dielectric surface is proposed for interference reduction of Fresnel reflection. The structural and material parameters of the antireflection composite are calculated within the Maxwell−Garnett effective-medium approximation. The results of the approximate analytical calculation are in good agreement with the exact numerical solution to theMaxwell equations.

The present review paper traces the development of nanocrystalline copper (Nc-Cu) and nanocrystalline nickel
(Nc-Ni) and their mechanical properties. The objective is to summarise the various results available in the literature.
The mechanical properties discussed are elastic modulus, Poisson’s ratio, hardness, yield stress, ultimate tensile stress, strain/elongation to failure, superplasticity, creep, fatigue and fracture properties. The review is limited to bulk nanocrystalline materials. Shortcomings and limitations of the various studies that have been conducted are also highlighted. The present compilation is expected to be useful for researchers engaged in experimental work and computer modelling in this area.

The optical properties of a composite medium comprised of a transparent host and uniformly oriented prolate silver nanoparticles are investigated theoretically. The results demonstrate that it is possible to fabricate an ultrathin-film polarizer with high performance in transmission and reflection in the visible region of light.

We present results of Brownian dynamics simulations of tethered nanospheres and tethered nanorods. Immiscibility between tether and nanoparticle facilitates microphase separation into the bicontinuous, double gyroid structure (first reported by Iacovella et al. [Phys. Rev. E 75, 040801(R) (2007) ] and Horsch et al. [J. Chem. Phys. 125, 184903 (2006)] , respectively). We demonstrate the ability of these nanoparticles to adopt distinct, minimal energy local packings, in which nanospheres form icosahedral-like clusters and nanorods form splayed hexagonal bundles. These local structures reduce packing frustration within the nodes of the double gyroid. We argue that the ability to locally order into stable structures is key to the formation of the double gyroid phase in these systems.

In terms of the effective medium approximation, the optical properties of heterogeneous composite materials with disordered nanosized metal inclusions of spheroidal shape with plasmon resonances lying in the visible spectral range are studied. The conditions are analyzed under which the optical characteristics of the composite with axial symmetry of the inclusion orientation distribution with respect to a certain preferential direction significantly depends on the electric field direction in the electromagnetic wave. It is shown that, in the vicinity of the plasmon resonance of inclusions, the composite layer of subwavelength thickness may exhibit a high polarization selectivity in both eflection and transmission with moderate absorption. The effect of the orientational disorder of inclusions on the optical characteristics of a polarization splitter of this kind is discussed. The predictions based on equations of quasielectrostatic effectivemedium model agree well with the results of exact numerical solution of the Maxwell equations.

We consider optical properties of metal-dielectric composite media which have active laser medium as one of components. For various concentrations of components using exact electrodynamical calculations, we investigate the behavior of amplification coefficient which is necessary to compensate the absorption at metallic inclusions.

A single-step method to coat and bifunctionalize water-reduced gold nanoparticles (NPs) with two distinct reactive groups is reported. The coating is based on a peptide that bonds to the NPs surface by its N-cysteine amino acid, terminates with a C-terminal lysine, and stabilizes the colloids, thanks to the surface organization provided by the rest of the non-polar chain. The process yields stable, non-cytotoxic NPs presenting reactive amine and carboxylic groups on the surface; these allow rapid, selective and modular conjugation of virtually any chosen biomolecule or fluorophore. Functionalized and conjugated nanostructures are analyzed by electrophoresis, SEM, SERS; their biocompatibility and delivery capability are tested by cellular-uptake experiments.A single-step method to coat and bifunctionalize water-reduced gold nanoparticles (NPs) with two distinct reactive groups is reported. The coating is based on a peptide that bonds to the NPs surface by its N-cysteine amino acid, terminates with a C-terminal lysine, and stabilizes the colloids, thanks to the surface organization provided by the rest of the non-polar chain. The process yields stable, non-cytotoxic NPs presenting reactive amine and carboxylic groups on the surface; these allow rapid, selective and modular conjugation of virtually any chosen biomolecule or fluorophore. Functionalized and conjugated nanostructures are analyzed by electrophoresis, SEM, SERS; their biocompatibility and delivery capability are tested by cellular-uptake experiments. Electronic supplementary information (ESI) available: SEM pictures, UV-Vis spectra and DLS measurements of bare, coated and functionalized gold nanospheres, confocal fluorescence images of cell-internalized systems with PI-staining, electrophoresis of AuNs coated with glutathione and of AuNsK and AuNsN in the presence of glutathione. See DOI: 10.1039/c0nr00350f

Advances in nanomaterials/nanostructures offer the possibility of fabricating multifunctional materials for use in engineering applications. Carbon nanotube (CNT)-based nanostructures are a representative building block for these multifunctional materials. Based on a series of in silico studies, we investigated the possibility of tuning the thermal conductivity of a three-dimensional CNT-based nanostructure: a single-walled CNT-based super-nanotube. The thermal conductivity of the super-nanotubes was shown to vary with different connecting carbon rings and super-nanotubes with longer constituent single-walled CNTs and larger diameters had a smaller thermal conductivity. The inverse of the thermal conductivity of the super-nanotubes showed a good linear relationship with the inverse of the length. The thermal conductivity was approximately proportional to the inverse of the temperature, but was insensitive to the axial strain as a result of the Poisson ratio. These results provide a fundamental understanding of the thermal conductivity of the super-nanotubes and will guide their future design/fabrication and engineering applications.