Journal of Nano Research Vol. 9

Abstract: Quantum information theory is employed to analyze the growing behavior of nanostructured molecules through marginal H-type von Neumann informational entropies. This is achieved by performing ab initio electronic structure calculations at the Hartree-Fock level of theory to characterize the initial steps towards growing Polyamidoamine (PAMAM) dendrimers, starting from conformational structures of polymeric precursors up to generations G0 (with 84 atoms), G1 (228 atoms), G2 (516 atoms), and G3 (1092 atoms). Several physical descriptors like radius of gyration, asphericity factor, moments of inertia and dipole moments, along with chemical reactivity indexes such as total energies, hardness and electrophilicity are employed to provide evidence for the validity of dense-core model of dendrimers.

Abstract: The ability of nanostructured TiO2 in anatase phase to eliminate Escherichia coli (E. coli) by UV light irradiation was tested using titania films supported on glass substrates. The films were obtained by electrophoretic deposition of titania sol on sputtered Ti Corning glass substrates. Experimental procedure used to obtain these films and their characterizations are discussed in this paper. Nanostructure nature of the films was analyzed using scanning electron microscopy and atomic force microscopy. Optic microscopy was used to study the photocatalytic activity of films and their interaction with E. coli bacteria, in order to measure the reduction in E. coli colonies. The structure of anatase TiO2 was determined using grazing incidence X-ray diffraction.

Abstract: One of the interests on the study of doped materials with rare earths in their bulk or nanoscale size is owing to the enhancement of the intensity of light in their photoluminescence when a lanthanide exists in a receptor material, as ZnO in our case. Until now, one of the most useful theories for calculations of electronic properties in molecular and solid state systems is the Density Functional Theory (DFT), which is not capable to manage well the presence of high localized electrons, as in lanthanide compounds in general and the doped case in particular. We propose to study these materials with super cell model using some correction to the standard calculations. For this goal, we employ the WIEN2k [1] code using the LDA+U approximation to take into account the strong correlation of the f electrons coming from the lanthanide. We emphasise the study of deformation due to the presence of Eu ion in the structure of host material, optimizing the position of neighboring Oxygen atoms. This deformation has been related to Kondo Resonance [2] appearing around the Fermi Energy of the compound, due to hybridization [3] among the f electrons from rare earth and neighboring oxygen levels.

Abstract: The growth of tungsten oxide nanowires on silicon substrates without using any catalyst is demonstrated by means of close-spaced vapor transport (CSVT) technique at atmospheric pressure. The source was formerly prepared from a tungsten foil to produce a tungsten oxide film. CSVT array is completed with silicon substrates located at a distance of ~350 m over the tungsten oxide source at moderate temperatures (~750°C). Two distinct kinds of nanostructures were produced; a uniform distribution of free standing tungsten oxide wires of several micrometers in length with diameters less than 150 nm; and wires assembled to form nanowire bundle. The X-ray diffraction characterizations show that the phases of WO2.7 and WO2.9 are present.

Abstract: Fluorinated silicon oxide (SiOF) films have been prepared in a conventional atmospheric pressure chemical vapor deposition (APCVD) reactor. APCVD technique utilizes tetraethoxysilane, ozone and hydrofluoric anhydride as gas sources. SiOF films are deposited by changing the temperature of deposit. Substrate holder was maintained in the temperature range of 200 to 275°C. Films were characterized based on the deposition temperature. Chemical bonding structure of the films was evaluated by Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy and ellipsometry techniques. FTIR spectra revealed Si-F bond at about 935 cm-1. Incorporation of fluorine has a minimal contribution in the reduction of refractive index of SiOF films from 1.46 to 1.35.Therefore, the main mechanism responsible for this reduction of refractive index is the porosity generated by incorporation of fluorine atom in the SiOF films. Dielectric constant was reduced from 4.2 corresponding to that of SiO2 films, to the values in the range of 3.18 to 3.6 for SiOF films deposited by APCVD technique.

Abstract: Carbon nanofibers (CNF) were surface coated with a thin layer of poly (acrylic acid) (PAA) via plasma polymerization of acrylic acid (AA). The plasma polymerization treated CNF resulted in a significant change of its surface characteristics from hydrophobic to hydrophilic due to the polar groups in PAA-coating layer. Dispersion tests in water and ethanol confirmed a marked change in the hydrophobicity of the treated CNF. In addition, FTIR results showed a new signal for the treated CNF at 1046 cm-1, assigned to C-O groups and represented the presence of PAA. Morphology results by scanning electron microscopy (SEM) revealed that the untreated CNF has a very smooth surface, whereas the treated CNF showed certain roughness on its surface due to the deposited PAA coating layer.PAA coating on the treated CNF was also observed by transmission electron microscopy (TEM) and its thickness was determined to be between 14 to 18 nm. Dynamic Light Scattering (DLS) was used to show that plasma polymerization improved the dispersion of treated CNF and prevented its agglomeration in water versus the poor dispersion observed with untreated CNF.

Abstract: In the present work, nanofluids containing spherical TiO2 nanoparticles were mixed in water, to have various concentrations with the average particle diameter of 81.3 nm. Scanning electron microscopy, energy dispersive spectroscopy and X-ray diffraction techniques were used to characterize the TiO2 nanoparticles. Photothermal techniques, thermal lens spectrometry (TLS) and photopyroelectric (PPE) were used to measure the thermal diffusivity and thermal effusivity of the nanofluids respectively. The experimental results show that the thermal diffusivity (D) increased with the increase in TiO2 nanoparticle concentration. It was also possible to see that thermal effusivity (e) had a similar behavior as the thermal diffusivity, where both the values increased with the concentration rate and finally a comparison with literature values show good agreement with the thermal parameters of water.

Abstract: Nano - crystalline Al-Mg-Mn was synthesized by ball milling technique. Microstructure of these alloys has been studied from X-ray line broadening. The crystallite size of nano - crystalline Al-Mg-Mn system decreases by increasing the Mg content, While the micro-strain, median diameter,, and geometrical standard deviations,  increases by increasing the Mg content. Micro-hardness of our system has been investigated by Vickers hardness test. The hardness increases by increasing the Mg content.

Abstract: 1-methyl-2-phenylfulleropyrrolidine (1), 1-methyl-2-(4-(1-piperidyl)-phenyl)-fulleropyrrolidine (2), 1-methyl-2-(4-fluorophenyl)-fulleropyrrolidine (3) and 1-methyl-2-(3-hydroxy-2-naphtyl)-3,4-fulleropyrrolidine (4) were synthesized by Prato reaction and characterized in the reaction mixture by UV-Vis spectroscopy and matrix assisted laser desorption ionization (MALDI). A comparison of theoretical and experimental UV spectra was carried out.