International Journal of Nanoscience

In this paper, we have examined the effect of quantum confinement of carriers on the threshold voltage of strained-silicon (s-Si) nanoscale Metal Oxide Semiconductor Field Effect Transistors (MOSFETs). Using results from quantum theory and two-dimensional simulation, we show that strain-induced threshold voltage roll-off in s-Si nanoscale MOSFETs can be overcome by decreasing s-Si layer thickness. Based on our simulation study, we provide an optimization between threshold voltage, strain and s-Si layer thickness.

The indirect exchange interaction between two magnetic impurities in a two-dimensional electron system under a strong magnetic field is studied. The nuclear spin coupling is mediated by Landau electrons bound to these impurities. We consider the contact hyperfine coupling of the bound Landau electrons, which is an s-type wave function and is therefore significant. The d electrons are indirectly involved in the contact interaction through their resonance scattering potential, which is found to be spin selective and therefore binds Landau electrons with proper spin polarization. Thus, the resulting superexchange interaction between two different sites involves the bound Landau states of one site and the impurity d states of the second site, resulting in an antiferromagnetic interaction between the nuclear spins of the impurities. The coupling constant between these nuclear spins, J, is found to depend strongly on the ratio of the impurity separation over the magnetic length. Possible applications of these results may include a long-range mechanism for coupling between two nuclear spins to be used as a qubit interaction with a spacing distance of the order of magnitude of the magnetic length.

In this paper, we study the electrical transport and Negative Differential Resistance (NDR) in a single molecular conductor consisting of a cysteine sandwiched between two Au(111) electrodes via the Density Functional Theory-based Nonequilibrium Green's Function (DFT-NEGF) method. We show that (surprisingly, despite their apparent simplicity, these Au/cysteine/Au nanowires are shown to be a convenient NDR device) the smallest two-terminal molecular wire can exhibit NDR behavior to date. Experiments with a conventional or novel self-assembled monolayer (SAM) are proposed to test these predictions.

The projected density of states (PDOSs) and transmission coefficients T(E) under various external voltage biases are analyzed, and it suggests that the variation of the coupling between the molecule and the electrodes with external bias leads to NDR.

The Discrete Ordinates Radiation Element Method (DOREM), which is radiative transfer code, is applied for solving phonon transport of nano/microscale materials. The DOREM allows phonon simulation with multi-dimensional complex geometries. The objective of this study is to apply the DOREM to the nano/microstructured materials. It is confirmed that significant changes of the heat transport phenomena with different characteristic length scales and geometries are observed. This study also discusses further variations for understanding of heat transport mechanisms.

This is a first case ever reported on the fullerene-based low toxic nanocationite particles (porphyrin adducts of cyclohexl fullerene-C₆₀) designed for targeted delivery of the paramagnetic magnesium stable isotope to the heart muscle providing a sharp clinical effect close to about 80% recovery of the tissue hypoxia symptoms in less than 24 h after a single injection (0.03–0.1 LD₅₀). A whole principle of this therapy is novel: ²⁵Mg²⁺-magnetic isotope effect selectively stimulates the ATP over-production in the oxygen-depleted cell due to ²⁵Mg²⁺ released by nanoparticles. Being membranotropic cationites, these "smart nanoparticles" release the over-activating paramagnetic cations only in response to the metabolic acidic shift. The resulting positive changes in the heart cell energy metabolism may help to prevent and/or treat the local myocardial hypoxic disorders and, hence, to protect the heart muscle from a serious damage in a vast variety of the hypoxia-caused clinical situations including both Doxorubicin and 1-methylnicotineamide cardiotoxic side effects. Both pharmacokinetics and pharmacodynamics of the drug proposed makes it suitable for safe and efficient administration in either single or multi-injection (acute or chronic) therapeutic schemes.

Molecular dynamics simulations have been employed to investigate the static and dynamic properties of unsupported spherical Cu particles with size ranging between 1 and 10 nm. The potential energy, the structural arrangement, and the mobility of atomic species were studied for each nanometer-sized particle within the temperature range between 300 K and the melting point. Two distinct regions, namely an internal domain and a surface layer, can be identified within each nanoparticle on the basis of the radial profiles of such quantities. The atomic species belonging to the interior of the particle display a bulk-like behavior. By contrast, the surface layer is characterized by an excess potential energy associated with a disordered structure. At relatively low temperatures, the surface atoms possess structural and energetic features intermediate between the ones of a superheated bulk solid and of an undercooled bulk liquid. Pre-melting processes at the surface are also evident at temperatures close to the melting point. The nanometer-sized particles can be thus regarded as heterogeneous two-state systems consisting of roughly distinguishable bulk-like and surface regions.

Wide bandgap II–VI semiconductor quantum dots embedded in glass matrix have shown great potential for opto-electronic device applications. The current problem is to achieve low size dispersion, high volume fraction, and better control over the size of the quantum dots in glass matrix. In this work, a modified growth method has been proposed to achieve a greater control over the size of quantum dots, to reduce their size dispersion and to increase their volume fraction. A theoretical model has been developed to quantitatively estimate the various parameters of the quantum dots. The effects of aging on various parameters of quantum dots in Semiconductor-Doped Glass (SDG) samples have also been discussed in the present work.

A novel sonochemical method is developed to coat multi-walled carbon nanotubes (MWCNTs) on expandable thermoplastic (acrylonitrile and methylacrylonitrile polymer) microspheres (Expancel). These polymeric thermoplastic microspheres were further fabricated in a form of foam panels using a compression molding technique. The test coupons were cut precisely from the as-prepared panels and characterized by scanning electron microscopy (SEM), X-ray diffraction, thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The SEM studies have shown that the MWCNTs are well dispersed over the entire volume of the matrix with minimal agglomeration. The foam cell structures are well-ordered, spherical in shape, and uniform in size. The TGA and DSC analyses indicate that the nanocomposite foam samples are thermally more stable than the corresponding neat foam samples. The compression tests have been carried out for both nanocomposite and neat foam samples. These test results show a significant increase in compressive strength and modulus for nanocomposite foam samples as compared to the neat foam samples. These enhancements in compressive properties have been observed repeatedly for multiple batches. The details of synthesis procedure, thermal and mechanical characterization are presented in this paper.

A novel feature of electron transport is explored through a thin film of varying impurity density with the distance from its surface. The film, attached to two metallic electrodes, is described by simple tight-binding model and its coupling to the electrodes is treated through Newns–Anderson chemisorption theory. It is observed that in the strong disorder regime the amplitude of the current passing through the film increases with the increase of the disorder strength, while it decreases in the weak disorder regime. This anomalous behavior is completely opposite to that of conventional disordered systems. Our results also predict that the electron transport is significantly influenced by the finite size of the thin film.