Advanced Materials Research Vols. 55-57

Abstract: CuO nanostructures were synthesized by oxidizing copper thin films. The copper thin film was grown on alumina substrates by evaporation copper powder at pressure of 0.04 mtorr. The copper thin films were then oxidized 800, and 900oC for 12, 24 and 48 hr, respectively. The obtained CuO nanostructures were investigated by Energy Dispersive Spectroscopy (EDS), Field Emission Scanning Electron Microscope (FE-SEM) image, and X-Ray Diffraction (XRD). The diameter of CuO nanostructure is around 100-600 nanometers and it is depends on oxidation reaction time and temperature. These CuO nanostructures have a potential application for nanodevices such as nano gas sensor or dye-sensitized solar cells.

Abstract: In the present work, we demonstrate a method to synthesis SiO2 nanopowder from rice husk ash by using a vibro-milling followed by a heat treatment technique. Rice husk ash was milled by vibro-milling for 4 h to obtain nanopowder. In order to eliminate carbonaceous material, the nanopowder was heat at 1000°C for 3 h. Characteristic of the powder was then investigated by XRF, XRD, and SEM techniques. The silica nanopowder with 95% purity was obtained after the heat-treatment. The result indicated that the present method is a beneficial process to produce the silica nanopowders of low cost and high mass productivity.

Abstract: Nano-crystalline boehmite (AlOOH) proposed as a precursor for g-Al2O3 production was prepared using precipitation process. The mixture of two starting solutions of AlN3O9.9H2O and Na2Al2O4 was formed and NaOH was used as pH adjustment. Various preparation conditions, starting pH and temperatures were applied. The results suggested that high purity AlOOH powder could be obtained at solution temperature above 60oC and starting pH was in range 7-11. Their crystalline size increased from 2.4 to 3.9 nm with increasing pH. According to the results, AlOOH from pH 8 and temperature 80oC was selected for producing the g-Al2O3 by calcination in the temperature range of 350oC-1100oC. Transformation from AlO(OH) to g-Al2O3 could be readily observed from the whole temperature range and g-Al2O3 crystalline size was increased with increasing calcination temperature. After the temperature reached 1100oC, transformation to a- and q- phases were also found. Morphology of g-Al2O3 powder shows a strong aggomeration.

Abstract: The nanostructural zinc oxide (ZnO) particles have been synthesized by two techniques, solid-state reaction and solvothermal method. The solid-state reaction method, the ZnO nanoparticles were carried out by reacting zinc acetate with sodium hydroxide in sodium dodecyl sulfate (SDS) and beta-cyclodextrin (b-CD). The effects of reaction condition on the nanocrystal morphology were investigated. The physical properties of ZnO were characterized using X-ray diffraction technique and transmission electron microscopy. The results showed that the obtained ZnO nanorods were in the wurtzite structure with various sizes of single crystals. FT-IR analysis also confirmed the binding of SDS with ZnO nanorods. For the solvothermal technique, ZnO nanostructures with various morphologies were synthesized from the treatment of zinc acetate at 80°C with the selected polymeric surfactant, poly(vinyl pyrrolidone) (PVP), in aqueous solution and ethylene glycol. The results showed that the selected surfactant and solvent play a different role in controlling the morphologies of the ZnO nanocrystals. The ZnO nanorods and nanoparticles were successfully obtained. The XRD result revealed that the ZnO is in the wurtzite structure with the particle size in range of 270-1300 nm. The optical properties of the samples were also studied via UV-vis spectrophotometer.

Abstract: This paper demonstrates synthesis of gold nanocubes with uniform size about 30 nm by a simple electrochemical method. The surfactant cetyltrimethylammonium bromide (CTAB) and tetradodecylammonium bromide (TTAB) were used as the stabilizer and micelle template to control the size and shape of gold nanocubes. In this study, acetone solvent was injected to the electrolyte solution with surfactant, changing the surfactant micelle-template, leading to the formation of gold nanocubes. The gold nanocubes have a surface plasmon resonance (SPR) band at a wavelength of about 530 nm. The gold nanodumbbells have been determined to be single-crystalline with a face-centered cubic (fcc) structure by X-ray diffraction (XRD) analysis.

Abstract: A simple seeded mediated growth (SMG) method with addition of vitamin C solvent to prepare novel gold nanodogbones is reported. In SMG method, gold nanodogbones are produced in reasonable yield by chemical reducing HAuCl4 in surfactant solution, with small seed gold particles added as nucleation centers for the preparation of large size nanoparticles. Besides, the surfactant absorbs strongly (as a bilayer) along the crystal face of the nanoparticle. The surfactant is usually considered to be a soft micelle-template, which controls the size and shape of the nanoparticles. In this study, the role of vitamin C is found to alter gold nanoparticles shape from rod structures to dogbone-like structures. The aspect ratio of gold nanodogbones can be easily controlled by addition amount of vitamin C solvent from 10 to 30 µL.

Abstract: An inorganic-organic hybrid vanadate complex, Zn2(en)V2O7 (en = ethylenediamine) has been hydrothermally synthesized and characterized by single-crystal X-ray crystallography, TG analysis, IR spectroscopy, and elemental analysis. The title compound crystallizes in the monoclinic space group P21 with a = 7.0885(7), b = 8.6040(9), c = 8.1869(8) Å, b = 112.224(2)° and V = 462.22(8) Å3, T = 298±2 K and R1[I>2s(I)] = 0.0291 for 2170 observed reflections. The structure consists of undulating sheets constructed from helical chains that share Zn coordination centers with repeating units propagated into a helix by the two-fold screw axes at 0, y, ½ and pillared with alternating VO4 tetrahedra to generate a 3D chiral network. Neighboring helices are interconnected by µ2-O bridges to form the three-dimensional network. The strength of the network is reinforced by hydrogen bonding. TG analysis shows thermal stability of the network up to 283 °C.

Abstract: Poly(3-hexylthiophene) (P3HT) is one of the most studied conjugated polymer for molecular electronics especially for organic field effect transistors (OFETs) and organic light-emitting devices (OLEDs). This is mainly due to the fact that P3HT provides excellent electrical properties and showed high carrier mobility. In this research we studied the photo generated charge carrier transport of P3HT film by the time-of-flight (TOF) method. For device fabrication, P3HT was dissolved in chloroform with concentration of 8 mg/ml then the solution was spun directly onto an ITO pattern coated on glass substrate. Then the aluminum electrode was prepared on film by thermal evaporation. In TOF measurement, the constant voltage was applied to electrode of sample and the film were photo-excited by irradiation of a short pulsed laser light (λ=650 nm). This caused charge separation within the film. The generated charge carrier was used to calculate the mobility of the film. The TOF mobility was determined as a function of applied voltage and light condition.

Abstract: The optical properties of metal-free and metal phthalocyanine were calculated by using density functional theory with various metals including copper, zinc, cobalt, iron and manganese. The polymorphic form of these crystals was employed only for β from. The molecules were optimized with the symmetry of D4h. For the alignments of the molecule in the crystal structures of this polymorphic form which have not been reported in detail, the variation of total energy was examined as a function of the align angles. The align angle at minimum total energy was used for the band calculation. The density functional theory and plane-wave pseudopotential method were used to calculate the energy band structure and electron density of state. The calculated band structures of various metal phthalocyanines can be divided in two groups according to the peak wavelength of the maximum absorption. The first group with the peak wavelength at about 230 nm consists of β-CuPc, β-H2Pc, and β-MnPc while the wavelength of another group for β-CoPc, β-FePc, and β-ZnPc occurs at 350 nm. From the density of state calculation, it indicates that these two transitions originate from the different band and the ratio of the absorption between these states depending on the type of metal in phthalocyanine. The optical absorption was derived to examine the absorption spectra for various metal compositions while the variation in intrinsic electrical conductivity can be estimated from the shape of the band. The phonon and infrared spectra were also determined in order to investigate the vibration mode of molecule in the crystals

Abstract: In this work, the sodium salt of 2-acrylamido-2-methylpropanesulfonic acid (Na-AMPS) was photopolymerised in aqueous solution with ethylene glycol dimethacrylate (EGDM) added as a crosslinking agent and 4,4'-azo-bis(4-cyanopentanoic acid) as the water-soluble photoinitiator. The aqueous solution was poured into a vertical sheet-forming mould consisting of two parallel plates covered with Teflon® sheets as release liners. Spacers were used to control the sheet thickness with a polymer mesh inserted in the middle to strengthen the hydrogel. The hydrogel sheets obtained were of 1.2 ± 0.2 mm thickness and showed good transparency, flexibility and skin adhesion. On immersion in distilled water at 37°C, it was found that the equilibrium water content (EWC) reached 98 ± 1% within 20 mins following which the equilibrium water retention (EWR) in ambient air was 21 ± 1% over a period of about 4 hrs. The water vapour transmission rate (WVTR) was measured at 37 °C and was found to be 82 ± 2 g m-2 hr-1. It is concluded that this Na-AMPS hydrogel sheet has properties which show potential for biomedical use as a wound dressing.