Science and Technology of Nanomaterials

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Authors: N. Buang, M. Aziz, S. Sanip, J.C. Tee, Z.H.Z Abidin, Ahmad Faris Ismail
Abstract: Carbon are well known as active materials for energy storage and conversion. They are preferred because carbon materials have high electrical conductivity, low cost, high surface area, porosity, formability and possess good chemical and electrochemical resistivity. The most recently discovered novel carbon material is the carbon nanotubes, having unique geometrical structure and stable mechanical and chemical properties. The starting materials for carbon nanotubes production widely used are high purity graphite. Thus, two types of carbons were studied and thermal treatments were conducted at temperatures ranging from 600 – 800 °C for several hours. The effect of the pretreatment upon their morphology and surface area were looked into. It was found that significant changes occurred for the natural carbons while the synthetic carbons showed little or no changes at the particular temperature range. The thermal treatment has resulted in the exposure of fresh edge planes and microparticles as well as changes in the specific surface area and enhances their adsorption properties.
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Authors: C.G. Hu, W.L. Wang, Bo Feng
Abstract: The carboxyl modified carbon nanotubes were obtained by treating them in the concentrated nitric acid with a little surfactant. The complete electrochemical combustion of phenol has been found under 5 M at the carboxyl modified carbon nanotube electrode in phosphate buffer solution. The reaction was discussed in details. Due to the porous tubule of the structure of the carbon nanotube and large quantity of hydroxyl exists in the carboxyl modified carbon nanotube electrode, which were necessary for the continually electrochemical combustion of phenol. Long time potentiostatic oxidation showed that the phenol could be eliminated from the aqueous media without any foul at the carbon nanotube electrode.
289
Authors: X.W. Sun, C.X. Xu, B.J. Chen, Y. Yang
Abstract: Zinc oxide (ZnO) microtube has been fabricated by heating the mixture of ZnO and graphite powders in the atmosphere. The ZnO microtubes showed perfect hexagonal profiles with bell-mouth or normal hexagonal tops. Both X-ray diffraction (XRD) and high-resolution transmission electron microscopy (TEM) demonstrated that the product was composed of ZnO with typical hexagonal structure grown predominantly along (002) direction. The growth process was interpreted by means of vaporliquid-solid mechanism combining with the evaporation of metallic zinc.
293
Authors: Z.L. Tsakadze, K. Ostrikov, R. Storer, S. Xu
Abstract: Large area, highly uniform vertically aligned carbon nanotips (VACNTP) and other nanostructures have been grown on silicon (100) substrates with Ni catalyst in the low-temperature, lowfrequency, high-density inductively coupled plasmas (ICP) of methane-hydrogen-argon gas mixtures. The control strategies for the morphology, crystalline structure and chemical states of the resulting nanostructures by varying the growth conditions are proposed. XRD and Raman analyses confirm that the nanotips are well graphitized, which is favorable for the field emission applications.
297
Authors: Andreas K. Schaper, Hao Qing Hou, Werner Treutmann, Fritz Phillipp
Abstract: Electron microscope studies are reported of MWCNTs without and with metallic encapsulations prepared by pyrolysis of organo-metallic precursors such as iron(II)phthalocyanine and ferrocene/anthracene mixtures. For straight and well-ordered MWCNTs, we obtained clear evidence of a scroll type structure with uniform chirality. Conical growth implicated the opening of the tube walls by termination of the graphene layers at the wall surfaces. Evidence is provided of the participation of iron carbide as an intermediate phase during graphite formation. Coercivities of the nanowire material up to 2550 Oe at 5 K, and constant saturation magnetization were measured.
301
Authors: C.G. Hu, W.L. Wang, K.J. Liao, Y.T. Wang
Abstract: Electrochemical behaviors of epinephrine and ascorbic acid have been studied at the carbon nanotube electrode using cyclic voltammetry. Electrocatalysis has been found for epinephrine redox reactions at the carbon nanotube electrode in the comparison with the glassy carbon electrode. A well-defined oxidative peak for ascorbic acid was observed at the carbon nanotube electrode with the peak potential negative shift versus the glassy carbon electrode. Low level of epinephrine can be determined at the carbon nanotube electrode selectively with high sensitivity in the presence of a large excess of ascorbic acid in the acidic media and in the physiological pH buffer solution.
305
Authors: W.L. Wang, K.J. Liao, C. Cai, C.G. Hu, Y. Ma, J.W. Lu
Abstract: The piezoresistive effect in iodine-doped carbon nanotube films was investigated by a three-point bending test. Carbon nanotubes were synthesized by hot filament chemical vapor deposition. The experimental results showed that the gauge factor for I-doped and undoped carbon nanotube films under 500 microstrain was about 350 and 65 respectively at room temperature, exceeding that of polycrystalline silicon (30) at 35°C. The origin of the piezoresistivity in the films may be ascribed to a strain-induced change in the band gap for the doped tubes and the intertube contact resistance and defects for the undoped tubes.
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Authors: C.G. Hu, W.L. Wang, Bo Feng, G.B. Liu
Abstract: The carbon nanotubes with carboxyl groups were obtained by using different chemical treatment methods. The electrical properties of the carbon nanotube films were investigated and voltammetric responses for Fe3+ / Fe2+ were measured at the carbon nanotube film electrodes.
313
Authors: S. Rajagopalan, S.J. Sharma, V.Y. Nanotkar
Abstract: In the present work, ultrasonic velocity measurements have been carried out in solutions of silver nanoparticles in the polymer matrix of poly(sodium, 4-styrene sulphonate) using Sing-Around technique, operated at 2 MHz.. The ultrasonic velocity of propagation shows an abnormal behaviour, indicating the existence of the phase separations in nano-colloidal solution. The effect of polymer is observed to be predominant in the phase separation at the lower concentrations of polymer in the mixture. At higher concentrations of the polymer in the mixture the phase separation seems to subside at higher temperature.
319
Authors: Anjali A. Athawale, Prachi P. Katre
Abstract: Silver nanoparticles were synthesized by irradiating silver nitrate solution (10-4 M) (methanol:water as a solvent) with different concentrations of aniline as a stabilizer in a 60Co g-ray source at a dose rate of 1.1 kGy. The particles exhibiting maximum stability up to a period of 7 days were obtained at the concentration of 0.1M aniline. The average particle size of the nanoparticles as estimated from XRD and TEM was found to be ~23 nm. Silver-Polyaniline (Ag-Pani) nanocomposite was prepared by oxidative polymerization of aniline. The applicability of synthesized nanocomposite as a sensor was tested by exposing the same to different chemical vapors viz. alcohols, amines, ammonia, chloroform etc. The results revealed its selectivity towards ammonia vapors and a long term stability of response is observed up to a period of two months. The above results are well supported by FT-IR spectroscopy.
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