International Journal of Nanoscience

The interaction between the quantum dot (QD) level and the 2D continuum of a quantum well (QW) is investigated theoretically. Due to interference from these states, the Fano-like resonance states appear in the 2D continuum of the QW. Also, the free-electron energy band of the QW is changed because of QD potential influence. We have calculated the position and the broadening of Fano resonances, and also modified the band structure of free states in the QW. The obtained results are used further for research on tunneling from the QW to the QD.

In this paper, we analyze dopant redistribution in a multilayer structure during laser scan annealing of radiation defects for the production of an implanted-junction rectifier, taking account of the temperature dependence of the diffusion coefficient. It is shown that inhomogeneity of the structure leads to increase in the sharpness of the implanted-junction rectifier and the homogeneity of the dopant distribution in the doped area. Some conditions on properties of the considered multilayer structure, which correspond to increase in the sharpness and the homogeneity, are determined.

The assembly of multiwalled carbon nanotube (MWCNT) films through dielectrophoresis is described and the electrical response of aligned and randomly oriented MWCNT films to temperature variations is evaluated. The resistance of the randomly oriented MWCNT films was found to decrease exponentially with temperature. The decrease was less marked when the films were annealed and kept dehydrated during the electrical measurements. Alignment of MWCNTs led to an apparent reduction in the electrical response of the films with temperature changes and a small measurement-to-measurement variability, suggesting that dielectrophoresis-aligned MWCNT films would be more reproducible detectors in applications exploiting CNT-mediated electronic sensing.

Metal–insulator transition in doped semiconductors is investigated in the presence of intense magnetic fields. A variational procedure within the effective mass approximation is employed using the Thomas–Fermi screening function and the exact quasi-Q2D Lindhard dielectric function. The Hubbard model results are justified using an effective mass that depends on interimpurity separation. The nonparabolicity of the subband is included using an energy-dependent effective mass. Though an increase of ionization energy with a magnetic field is observed for isolated donor models, the metallization occurs with an intense magnetic field at a higher concentration for a particular well width. The diamagnetic susceptibility of a hydrogenic donor impurity in GaAs/Ga_{1 - x}Al_xAs quantum well systems is discovered in the observation of metal–insulator transition. It is shown that the diamagnetic susceptibility diverges for all critical concentrations for a given well width. The large diamagnetic susceptibility (> 6) is observed at the transition. All the calculations are carried out for infinite and finite barriers, and the results are compared with the existing literature.

We consider the electrons bound in the conduction band of a double quantum well interacting with a strong monochromatic electromagnetic field in the terahertz (THz) region. Using a variant of the stationary perturbation theory, we have obtained the quasienergies and Floquet eigenvectors. The main features of power broadening and the dynamic Stark shift are retained. The sensitivity to the field parameters, such as intensity and frequency of the electric field on the state populations, can be used in various optical semiconductor device applications.

The anomalous electrodynamic characteristics (dielectric permittivity and electrical conductivity) of MRET water subjected to applied EMF (electromagnetic field) in the area of a very low range of frequencies were discovered during experiments conducted at Moscow State University, Russia. This confirmed the high level of long range dynamic structuring of water molecules in polarized-oriented multilayer formations in activated water produced with the help of the MRET activation process. The similarity of molecular formations of cell water and MRET-activated water contributes to their compatibility, easy bioavailability and assimilation of MRET-activated water into biological systems. The introduction of MRET water into biological systems can contribute to the enhancement of the cellular transduction mechanism and the proper functioning of cells in biological systems. The significant positive effect of MRET-activated water regarding tumor resistance in animals was observed in experiments conducted on 500 mice at Kiev Institute of Experimental Pathology, Oncology and Radiobiology, Ukrainian Academy of Science.

ZnIn₂S₄ nanofilms were grown on In₂S₃ substrates. The band gap of ZnIn₂S₄ barriers was approximately 2.8 eV at room temperature. The morphology and structure of the obtained nanofilms were already investigated via transmission electron microscope (TEM), scanning electron microscope (SEM) and X-ray diffraction analyses.^1,2 In this paper, thermal analyses are performed via a photothermal technique, which has been used to indirectly evaluate the specific heat capacity of the obtained Zn-doped nanofilms. The yielded value for an optimal zinc-to-indium ratio, x (0.33), at the mean room temperature (T_∞ = 301 K), was C_s ≈ 411.5 J K^-1kg^-1.

A sonochemical technique is developed to infuse titanium carbide nanoparticles into phenolic balsa foam material. Commercially available phenolic balsa foam resin solution (part A) is mixed with titanium carbide (TiC ~ 80 nm) nanoparticles, and irradiated with a high intensity ultrasonic horn. In the next step, the modified phenolic balsa foam resin solution containing titanium carbide nanoparticles is mixed with part B (containing phenol sulfonic acid, a catalyst) through a high speed mechanical stirrer. The reaction mixture is then cast into a rectangular mold to fabricate nanophased foam panels. Test coupons are cut precisely from the panels to carry out thermal, morphological and mechanical characterizations. The as-prepared foams are characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray diffraction (XRD), differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The SEM studies show that the particles are well dispersed over the entire volume of the matrix, with minimal agglomeration. The foam cell structures are well-ordered and uniform in size and shape. The TGA analysis indicates that the nanophased foams are thermally more stable than the corresponding neat systems. Quasi-static compression tests have been carried out for both nanophased and neat foam systems. The test results show a significant increase in the compressive strength (108%) and modulus (135%) compared to the neat system. These improvements in compressive properties have been observed repeatedly for multiple batches and with a minimum of five specimens tested from each batch. Details of the synthesis procedure and thermal and mechanical characterizations are presented in this paper.

A property of central interest for theoretical study of nanoconfined fluids is the density distribution of molecules. The density profile of the hard-sphere fluids confined within nanoslit pores is a key quantity for understanding the configurational behavior of confined real molecules. In this report, we produce the density profile of the hard-sphere fluid confined within nanoslit pores using the fundamental-measure density-functional theory (FM-DFT). FM-DFT is a powerful approach to studying the structure and the phase behavior of nanoconfined fluids. We report the computational procedure and the calculated data for nanoslits with different widths and for a wide range of hard-sphere fluid densities. The high accuracy of the resulting density profiles and optimum grid-size values in numerical integration are verified. The data reveal a number of interesting features of hard spheres in nanoslits, which are different from the bulk hard-sphere systems. These data are also useful for a variety of purposes, including obtaining the shear stress, thermal conductivity, adsorption, solvation forces, free volume and prediction of phase transitions.

The nanostructuring of thin Ni and In films by postdeposition electric field treatment is presented. Electric-field-induced nanostructuring effects, such as organization into an array of nanoparticles, formation of nanowires and transition from amorphous to nanocrystalline states, are demonstrated. It is further shown that the nanostructures can be manipulated by simply changing the direction of the applied field. Control parameters include separation of field probes (2–5 mm), duration (20–60 s) and direction of the field applied, and thickness (10–100 nm). High fields cause field-induced emission in the films. It is observed that while the microstructural reconstruction of the surfaces can be manipulated, the amorphous–crystalline transition is irreversible.

We report on the structure and morphology of thermoexfoliated graphite (TEG) powders and TEG–metal (Co, Cu, Ni) powders. Electrodynamic parameters of the compacted TEG and TEG–metal specimens have been studied along the compacting axis (c axis) within the range of electromagnetic radiation frequencies between 25.5 and 37.5 GHz. Metal particles attached to the surface of the TEG particles yield enhanced radiation shielding within the entire frequency range. Moreover, it is observed that the absorption coefficient increases with the increase in conductivity of the metal particles and is enhanced due to a high concentration of TEG–metal boundaries, which promote multiple reflections.

The average density of CoFe₂O₄ particles treated by using ferric nitrate is decided from specific saturation magnetization of both untreated and treated particles. Besides, some characteristic parameters, depending on the density of particles, are determined for CoFe₂O₄ ionic ferrofluids. The magnetization of the ferrofluids exhibits abnormal behaviors and is interpreted in relation to aggregates self-assembled from particles in the ferrofluids. Ringlike aggregates in which particles' moments linked into closed flux cause the saturation magnetization measured to be less than the theoretical value. The aggregates with opposed-parallel moments ordering will break up into isolated particles in the first magnetization process, so that the second magnetization will be easier than the first. For the aggregates with head-to-tail linked moments ordering, the magnetization behavior of the self-assembly structure may be hard to distinguish from field-induced aggregates.

Cadmium sulfide nanoparticles were synthesized and grown on glass substrates by chemical bath deposition. The method involves the preparation of aqueous solutions containing cadmium chloride (CdCl₂) and thiourea [CS(NH₂)₂] as source materials for cadmium and sulfur components, respectively. Ammonium hydroxide (NH₄OH)–ammonium chloride (NH₄Cl) solution was used as a complexing agent in this study. The hexagonal and cubic crystal structure of as-deposited CdS films, determined by X-ray diffraction (XRD), is shown. The effects of Cd:S ratio variation on the surface morphology and optical properties of CdS films are also reported. The UV-vis transmission spectrum and SEM micrographs indicated that the Cd:S ratio in the aqueous solution had an impact on the band gap as well as the crystallite size and packing density of the CdS particles due to the quantum confinement effect.

Polyaspartic acid (PAsp) was tagged with rhodamine isothiocyanate (Rhod) or phenyl isothiocyanate (PITC) and used for adsorption on single-walled carbon nanotubes (SWNTs) to facilitate homogenous dispersion of SWNTs in water. Results from UV-vis, FTIR-spectroscopic and Raman-spectroscopic studies and fluorescence measurements show considerable interaction between SWNTs and fluorophores immobilized on PAsp. The images from atomic force microscopy and transmission electron microscopy also indicate the presence of adsorbed polymers on the surface of SWNTs. The results suggest that the PITC-tagged PAsp is the most effective compound among the three compounds investigated for dispersing and debundling SWNTs in aqueous solutions, and the aqueous solutions are stable for months.