Journal of Nano Research Vol. 30

Abstract: Copper Oxide (CuO) nanoparticles were synthesized by the wet chemical method. The crystal structure and grain size of the particles were determined, using X-ray diffraction (XRD). The particle size and morphology were studied using the scanning electron microscope (SEM). The dielectric properties of CuO nanoparticles were carried out at different temperatures. The variation of the dielectric constant and dielectric loss were studied. The dielectric constants of the CuO nanoparticles are high at low frequencies, and decrease rapidly when the frequency is increased. Further, electronic properties like valence electron plasma energy, Penn gap, Fermi energy and electronic polarizability of the CuO nanoparticles, were estimated.

Abstract: Polymers and their composites find use in many engineering applications as alternative products to metal-based ones and, nowadays, have wide technical applications. One of the most used composite materials is the epoxy resins (EP), which is a thermoset polymer matrix. After cure, this material displays some excellent mechanical, thermal, electrical and chemical properties. For these reasons, it has been widely used for a wide range of automotive and aerospace applications, as well as for shipbuilding or electronic devices. However, EP has poor resistance to crack propagation and is brittle. So, in recent years, a considerable amount of research has been carried out to improve the performance of the toughness of EP. The most common studied technique consist to reinforce the EP matrix with rigid nanoparticle fillers, such as alumina, silica, mica, talc, organoclays, nanoclays, carbon nanotubes, TiO₂, among others. Among these nanofillers type, nanosize alumina particles has not been widely studied. However, recent studies have reported that the use of functionalized nanosize alumina particles as nanofiller can significantly improve the properties of the nanocomposite, even with low contents. These results, combined with the low cost of the alumina, show that the reinforcement of EP with alumina nanoparticles is a viable solution. In this paper, an attempt is made to review and highlight some recent findings and also some trends to show future directions and opportunities for the development of polymer nanocomposites reinforced with alumina nanoparticles.

Abstract: In this research, anatase TiO₂ nanoparticles were electrophoretically deposited on the FTO glass. This investigation was focused on the self-cleaning property of TiO₂ coatings and the effects of different parameters on this characteristic such as: applied voltages during electrophoretic depositions and durations of UV irradiation. Electrophoretic depositions of suspensions were performed in different voltages of 10, 30 and 60 V (for 10 s) at room temperature. TiO₂ coatings were sintered in 450°C for 1 hr. The phase transformation of TiO₂ films was considered using XRD. Morphology, average particle size and the thickness of TiO₂ films was analyzed using FESEM microscope. The photocatalytic activity of TiO₂ films was evaluated by the degradation of aqueous methyl orange (MO) under UV irradiation. The ultraviolet-visible spectrophotometer was used to record the changes of the adsorbancy of the MO solution. Hydrophilicity of TiO₂ films was determined by measuring contact angle of water droplet with the surface of TiO₂ films. Results represented that decomposition rate of MO solution by TiO₂ films enhances from 6.5% to 31% by increasing applied voltage of deposition from 10 to 60V and from 5% to 40% by increasing UV illumination duration from 1 to 5 hours. It was also observed that the contact angles of water droplet with the surface of TiO₂ films decrease from 34^o to 6.6^o by increasing applied voltage from 10 to 60V.

Abstract: Nitrogen-doped carbon nanotubes (N-CNTs) have beenprepared on FeNi catalyst by plasma-enhanced chemical vapor deposition in amixture of N₂, O₂, and CH₄. On the opened topof CNT, multi-layer graphene grown self-assembly was observed by transmissionelectron microscopy and high resolution transmission electron microscopy. Thenanohybrid film analyzed by scanning electron microscopy exhibited a porous and3D morphology and pyridinic and graphitic nitrogen structure confirmed by x-rayphotoelectron spectroscopy. Electrochemical measurement indicated that the filmfacilitated about three-electron transferpathway for oxygen reduction reaction in neutral medium and two-electronreductions in both alkaline and acidic solutions.

Abstract: The frustules of diatoms have excellent elasticity and high strength, but their main composition, amorphous silica, is a kind of typical brittle material. Molecular dynamics simulations of the uniaxial tension were carried out to study the size effect on the mechanical properties of amorphous silica. Stress-strain behavior, the radius of biggest void, radial distribution functions and bond angle distribution were analyzed. Our results show the small model exhibits a better ultimate strength, ductility and toughness than the large model, and the generation and expansion of voids plays an important role in the fracture behavior of the model. For the small model, some of Si-O bonds are stretched, and the average of O-Si-O bond angle decreases from 108o to 95o, which makes the model have a capability to perform larger plastic deformation and lead to a better ductility. However, for the large model, except the change of Si-O-Si bond angle, its structure has no other significant changes. Our results demonstrate that changes of size have significant impact on the mechanical properties and deformation mechanism of intrinsically brittle materials at the nanoscale.

Abstract: Nickel films are grown by radio frequency magnetron sputtering on Corning glass, polyimide foils and on the native oxide of Si (100) wafers at low (1x10^-3 mbar) and relatively high (2.5x10^-2 mbar) Argon pressure at 100 °C. The base pressure of the high vacuum chamber is 1x10^-7 mbar. X-ray diffraction experiments are performed to reveal the different texture of various Ni films. Magneto-optical Kerr effect hysteresis loops and magnetic force microscopy images show correlation between Argon pressure, texture and magnetic anisotropy of the films. The results are discussed with respect to relevant measurements of Ni/NiO magnetic multilayers prepared under similar experimental conditions.

Abstract: Different size of colloidal CdSe quantum dot (QD) was synthesized through a simple solvothermal route and their structural, morphological and optical properties were characterized with X-ray diffraction (XRD), transmission electron microscope (TEM), UV-visible absorption spectroscopy and fluorescence spectrometer. XRD and TEM measurement confirmed the formation of CdSe QDs. The red shift of absorption and fluorescence peaks indicated that the size of CdSe QDs increased with prolonging reaction time. The size of QDs varied from 2.2 nm to 3.4 nm by varying reaction time from 1 h to 7 h. The absorption spectra of CdSe/TiO₂ electrodes proved that the loading of CdSe QDs on TiO₂ can be greatly improved by MPA pretreatment. The effect of size of CdSe QDs on the performance of CdSe QDs sensitized solar cells was investigated. Due to the change of absorption range in the visible region and the conduction band shift for different size of CdSe, the photo-electric power conversion efficiency first increased and then decreased with increasing size of CdSe. The devices fabricated with 3.1 nm diameter CdSe nanoparticles exhibited the highest conversion efficiency of 0.70% under AM 1.5 G irradiation (100 mW cm⁻²).

Abstract: In₂O₃ thin films with a top layer of SnO₂ were deposited onto glass substrates by DC reactive-magnetron sputtering. After deposition, In₂O₃/SnO₂ samples were annealed in vacuum at 400oC. Structural, optical, and chemical composition was investigated by X-ray diffraction, UV-Vis spectroscopy and XPS, respectively. X-ray data showed that films grow polycrystalline, where indium oxide crystallized in cubic as the main phase, with a preferential growth at the [0002] direction and lattice parameter of 10.11 Å. Signals of rhombohedral phase were also detected. XPS depth profiles show that tin coexists in Sn²⁺ and Sn⁴⁺, while indium maintains the In₂O₃ stoichiometry. Binding energy of Sn⁴⁺ bound to oxygen was detected at 468 eV while In²⁺ bound to oxygen at 444.7 eV. Nor tertiary compounds were detected at the In₂O₃/SnO₂ interface, neither In or Sn in metallic state.

Abstract: Surfactant assisted synthetic route was followed to prepare silver selenide (β-Ag₂Se) nanoparticles. The effect of three different surfactants viz., Triton X100, SDS and CTAB in the formation of silver selenide nanoparticles had been examined. Pure and crystalline β-Ag₂Se nanophase was obtained in the presence of Triton X100 and SDS. However, the presence of CTAB leads to metallic silver formation. Nano Composite of β-Ag₂Se and ZnS was fabricated in the presence of glycine as a molecular linker. The products were characterized by different techniques such as XRD, FT-IR, SEM and TEM. Room temperature photoluminescence spectrum of the ZnS/ β-Ag₂Se nanocomposite exhibited two emission peaks at around 286 nm and 392 nm with enhanced intensity (l_ex = 250 nm).

Abstract: This study aimed to biosynthesize and optimize the process of iron oxide nanoparticles producing by Penicillium waksmanii isolated from soil by employing mathematical methodology. The synthesized nanoparticles were formed with fairly well-defined dimensions with good monodispersity determined by SEM (Scanning Electron Microscopy), AFM (Atomic Force Microscopy), DLS (Dynamic Light Scattering), UV-Visible spectroscopy, zeta potential, polydispersity index (PDI) and correlogram of nanoparticles. The effects of different factors such as pH, temperature and concentration of FeCl₃ on the particle size were investigated by Box-Behnken experimental design. The R² value was calculated to be 0.9992 indicating the accuracy and ability of the polynomial model.