Reaction mechanisms of graphene oxide chemical reduction by sulfur-containing compounds

We used density functional theory to study the reaction mechanisms of chemical reduction of graphene oxide (GO) by the sulfur-containing compounds HSO₃⁻ and H₂SO₃. We studied the reaction energy profiles for the following reactions: dehydroxylation of GO with one and two hydroxyl groups, de-epoxidation of GO with one or two epoxy groups and decarboxylation and decarbonylation of GO with carboxyl and carbonyl groups. We found that hydroxyl and epoxide groups could be easily reduced because of the lower energy barriers, whereas decarboxylation and decarbonylation reactions are not kinetically and thermodynamically easy because of the higher energy barriers. These reaction mechanisms at the atomistic level are not only supported by Chen’s experimental results [J. Phys. Chem. C 2010, 114, 19885], but are also beneficial for the development of new agents that could efficiently reduce GO.     

Evaluation of P2O5 distribution inside the main clinker minerals by the application of EPMA method

The formation of Portland clinker phases has taken place in thermodynamically non-equilibrium state between macro-oxides CaO, SiO₂, Al₂O₃, Fe₂O₃ and MgO from raw meal and P₂O₅ from bone meal. The paper deals with the study of clinker minerals as solid solutions with P₂O₅ during the clinkerization of raw mixture containing bone meal (BM). The ash of BM has contributed as a raw material to the formation of different clinker phases. Electron probe microanalysis (EPMA) method was used to determine the preferential distribution of P₂O₅ inside calcium silicate phases and its influence upon C₂S/C₃S ratio. Basing on these results, composition of solid solution of C₂S and C₃S was established.     

Effect of sputtering power on the electrical and optical properties of Ca-doped ZnO thin films sputtered from nanopowders compacted target

In the present work, we have deposited calcium doped zinc oxide thin films by magnetron sputtering technique using nanocrystalline particles elaborated by sol–gel method as a target material. In the first step, the nanoparticles were synthesized by sol–gel method using supercritical drying in ethyl alcohol. The structural properties studied by X-ray diffractometry indicates that Ca doped ZnO has a polycrystalline hexagonal wurzite structure with a grain size of about 30 nm. Transmission electron microscopy (TEM) measurements have shown that the synthesized CZO is a nanosized powder. Then, thin films were deposited onto glass substrates by rf-magnetron sputtering at ambient temperature. The influence of RF sputtering power on structural, morphological, electrical, and optical properties were investigated. It has been found that all the films deposited were polycrystalline with a hexagonal wurtzite structure and preferentially oriented in the (0 0 2) crystallographic direction. They have a typical columnar structure and a very smooth surface. The as-deposited films show a high transmittance in the visible range over 85% and low electrical resistivity at room temperature.     

Effects of vacancies on electronic and optical properties of GaN nanosheet: A density functional study

In this work, electronic and linear optical properties of GaN nanosheet are investigated through density functional theory and the dielectric tensor is derived within the random phase approximation (RPA). Electronic band structure calculations indicate that Ga atom vacancies in the 2D GaN system leads to n-type semiconductor, whereas the N atom vacancies change the electronic structure to a p-type semiconductor. Dielectric function, absorption coefficient, optical conductivity, extinction index, reflectivity, loss function and the refraction index of the GaN nanosheet and the Ga-defected or N-defected GaN systems are studied for both parallel (E∥x) and perpendicular (E∥z) applied electric field polarizations. Our results confirm that GaN nanosheet is a semiconductor which is sensitive to the type of vacancies and shows optical anisotropy at both polarizations states.     

Operating conditions of OOK signal regenerator with feed-forward control

The optimum operating conditions for a signal regenerator employing a hybrid optical-electrical scheme for intensity-modulated signals are experimentally investigated. The scheme comprises an optical coupler, a photo-detector, and a Mach–Zehnder intensity modulator, and can suppress the intensity noise, accompanying extinction ratio degradation. It is shown that the operating conditions that achieve the lowest bit error rate (BER) after regeneration depend on the extinction ratio and the optical signal-to-noise ratio of the input signal. We also investigate the noise suppression effect under conditions that do not change the extinction ratio.     

Factors inhibiting Australian office automation

Several factors are inhibiting the advance of office automation in Australia. These include a lack of suitable training, lack of understanding of OA by managers, fear of failure and fear of injury.     

Warm with high color rendering index white light from hybridization of Ca2BO3Cl:Eu2+ yellow phosphor and CdSe/ZnS nanocrystals

Yellow emitting Ca₂BO₃Cl:Eu²⁺ phosphor was prepared by solid state reaction at 900 °C. The particle was monoclinic crystal structure, and showed broad band emission at around 540–590 nm due to the 5d–4f transition. Single Ca₂BO₃Cl:Eu²⁺ phosphor converted white LED exhibited the CIE coordinates of (0.3441, 0.2675) with low CRI of 67.4. Hybridization of Ca₂BO₃Cl:Eu²⁺ with 535 and 610 nm emitting CdSe/ZnS nanocrystals contributed to increasing white spectrum and generated the warm color temperature (4055 K) with high CRI (83.9) of white light. The acceptable color stability was also observed from (0.3687, 0.3051) at 20 mA to (0.3645, 0.3101) at 80 mA.     

Biodegradation in coals and other organic-rich rocks

Biodegraded material and the remains of micro-organisms have been shown by transmission electron microscopy to be widespread in a range of Australian coals. Virtually all of this alteration, which has had significant effects on the properties subsequently attained by the coal, must have occurred at a very early stage of deposition. The micro-organisms appear to be mainly fungi and bacteria which have not only modified higher plant tissues but also represent significant amounts of added organic matter. Important amongst the latter are small but abundant occurrences of lipid-rich material of relevance in relation to the generation of hydrocarbons. The results suggest the need for reinterpretation of some light microscopic observations.     

Spectroscopic and magnetic properties of the garnet Ca2NaNi2V3O12Ca2NaMg2V3O12 solid solution

The vibrational, electronic (reflectance) and EPR spectra, as well as the magnetic properties of the garnet Ca₂NaNi₂V₃O₁₂ and its solid solution Ca₂NaMg_2-xNi_xV₃O₁₂ were investigated. The results show that a fraction of the vanadium (V) ions can be replaced by vanadium (IV), depending on the thermal history of the samples. Besides, the existence of some kind of antiferromagnetic interactions as well as the presence of a Ni spin forbidden transition in the electronic spectrum can be inferred. Likewise, the vibrational study suggests that in the case of garnets, the Raman spectroscopy would be a very useful tool to study the substitutional processes in this type of material.     

Amphiphilic light-emitting dendrons with oligo(phenylene vinylene) branches and oligo(ethylene oxide) terminal chains

We have recently synthesized new amphiphilic light-emitting dendrons with oligo(phenylene vinylene) core–branches and oligo(ethylene oxide) terminal chains (designated as: OPPV-d-OPEO). Due to the amphiphilic properties arising from the large difference in solubility between the two components, unique concentration- and temperature-dependent photoluminescence emissions were observed for aqueous solutions of the amphiphilic conjugated dendrons. The synthesis and amphiphilic behaviour of the OPPV-d-OPEO in solution are reported in this paper. Effects of the amphiphilic behavior on fluorescence emissions of the dendrons are discussed.