Journal of Nano Research Vol. 28

Abstract: A transition metal ion Cr⁴⁺(3d² spins) doped ZrO₂ of small crystallites presents tailored magnetic, electrical and optical properties useful for magnetodielectric and spintronic applications. A liquid polymer precursor gel (Cr⁴⁺ and Zr⁴⁺ complex with glycerol) when heated in an autoclave at a small pressure 0.6-0.7 atm at 420–470 K results in a compound Zr_0.8Cr_0.2O₂ with an average 5 nm crystallite size of a stabilized cubic (c)-ZrO₂-type phase (after 2 h annealing at 773 K in air). A broad Raman band is observed at ~300 cm^-1 in acoustic and transverse optic phonons characteristic of the c-ZrO₂-type structure, with a prominent O–Cr–O stretching band at 878 cm^-1 in a ferromagnetic order. A CrO₂/Cr₂O₃ surface layer exhibits two weak bands at ~1011 cm^-1 and 1032 cm^-1. The sample exhibits an ‘S’-shaped ferromagnetic hysteresis loop (does not saturate below 60 kOe fields) at 5 K, with a magnetization M = 85.79 emu/g (in the CrO₂ part) at 60 kOe and coercivity H_c = 100 Oe. With warming above 5 K, the loop converges progressively with only a weak ferromagnetism at room temperature, M = 9.08 emu/g and H_c = 54.2 Oe. As a pinning barrier, the uncompensated spins in the surface layer supports coercivity at low temperature. A model magnetic structure describes the magnetic properties in correlation to the microstructure.

Abstract: Conventional plasmonic devices involve metals, but metal-based plasmonic resonances are mainly limited to λ_res < 1 μm, and thus metals interact effectively only with light in the UV and visible ranges. We show that highly doped ZnO can exhibit λ_res ≥ 1 μm, thus moving plasmonics into the IR range. We illustrate this capability with a set of thin (d = 25–147 nm) Al-doped ZnO (AZO) layers grown by RF sputtering on quartz glass. These samples employ a unique, 20-nm-thick, ZnON buffer layer, which minimizes the strong thickness dependence of mobility (μ) on thickness (d). A practical waveguide structure, using these measurements, is simulated with COMSOL Multiphysics software over a mid-IR wavelength range of 4–10 μm, with a detailed examination of propagation loss and plasmon confinement dimension. In many cases, L_plas < λ_light, thus showing that IR light can be manipulated in semiconductor materials at dimensions below the diffraction limit.

Abstract: In this work we have synthesized TiO₂ nanostructures using a modified autoclave-free hydrothermal method from bulk powders. In the absence of pressure, Toluene was used as the dispersing agent to prohibit particle aggregation during the thermal treatment. Toluene to Ti mole ratio (X) was varied from 0 up to 30 to obtain different morphologies of TiO₂. X-ray diffraction (XRD) analysis demonstrated the Anatase phase for all the samples. FTIR analysis indicated that samples are free of carbon rich compounds and carbon contaminants. SEM images showed that with the increase of Toluene to Ti ratio, the morphology of the powders change from spherical particles with an average size of about 45 nm for X=0 to broccoli-shape structure for X=10, nanotubes for X=20 and nanosticks/wires for X=30. The synthesized TiO₂ nanotubes have been used as photoanode in a dye synthesized solar cell (DSSCs). The efficiency of the fabricated solar cell without any further modification was obtained about 2.3%.

Abstract: In the search to reduce the side effects, toxicity and assuring the desired effectiveness of the drugs, many efforts has been made to improve specific drugs’ delivery characteristics. Several carrier nanoparticles have been used to assist the drugs incorporation, absorption and transport through the bloodstream. However, most chemical synthesis routes are multistep and time-consuming treatments and, also, many carrier nanoparticles have toxic effects. In this work, we report a simple one-pot approach for the synthesis of CoFe₂O₄ nanoparticles (20 to 100 nm). The magnetic measurements revealed nanoparticles with a magnetic saturation nearly one third of that for bulk CoFe₂O₄. In vitro assays showed no hemolytic potential and negligible toxicity. By in vivo experiments using adult male mice we found no potential risk alterations by the nanoparticles administration. Therefore, the CoFe₂O₄ nanoparticles, synthesized by the current approach, can be a model drug-carrier, which makes them useful for the biomedical applications.

Abstract: Polycrystalline of (1-x)ZnAl₂O₄ – xSiO₂ compound with compositions of x = 0.00, 0.05, 0.10, 0.15, 0.20 and 0.25 have been prepared using sol-gel method. Structural properties was investigated by atomic force microscopy (AFM) and x-ray diffractometer (XRD). The AFM images analysis showed that the surface roughness of the highest composition had rougher surface compared with other samples. XRD measurement indicated that the crystallite size also increased with average crystallite size around 18 nm with cubic phase had been found. The dielectric permittivity value were measured with frequency range of 1 Hz to 1 MHz. It is showed that the dielectric value decreased as the freqeuncy was applied to the samples. The performance of the patch antenna showed that the antenna resonated at 3.30 GHz and give-13.87 dB with frequency range about 2 – 4 GHz.

Abstract: In this research, the CNT/TiO₂ nanocomposite solution was prepared using sol-gel method process. Definite amounts of CNT (0.06 g) were sonicated in 30 ml anhydrate 2-propanol. The measured quantities of Titanium (IV) Tetraisopropoxide (TTIP) – 5 ml were introduced into the CNT/2-propanol solution. The CNT/TiO₂ paste was doctor-bladed onto the FTO glass and consequently annealed at 250 °C, 350 °C and 450 °C for 30 min. The effect of annealing temperatures on the CNT/TiO₂ thin films was discussed. The CNT/TiO₂ thin films were characterized for morphological and electrical performance by Field Emission Scanning Electron Microscopy (FESEM), X-ray Diffraction (XRD), Incident Photon to Charge Carrier Efficiency (IPCE) and IV-Curve Efficiency analysis. The XRD patterns show the thin films major peak at (101) with average anatase phase crystallite size. The CNT/TiO₂ thin film's morphological structure composed of compressed and porous distributed composition. The crystal structures were changed upon increasing the annealing temperature. The IV measurement shows that the dye-sensitized solar cell (DSSC) at 450 °C produced highest photoelectric conversion efficiency (η) with 3.88 %. IPCE graph shows the solar cell absorb light within the UV spectrum region. It is revealed that annealing temperature has influence toward photovoltaic performance of the assembled DSSC.

Abstract: In this study, a freestanding thin film composed of lithium triflate (LiTf) salt (30-40 wt.%) and epoxidized-30% poly (methyl methacrylate)-grafted natural rubber (EMG30) (50, 54.6, 62.3 mol %) were prepared by a solvent cast technique. The EMG30 were found to increase the ionic conductivity of EMG30-LiTf by one order of magnitude compared to MG30-LiTf. The highest ionic conductivity achieved was 5.584 x10^-3 Scm^-1 at room temperature when 40 wt.% of LiTf salts were introduced into 62.3 mol % EMG30. The ionic conduction mechanisms in EMG30-LiTf electrolytes obey Arrhenius rule in which the ion transport in these materials is thermally assisted.