Controlling the Structure of Carbon Deposit by Nitrogen Doping Catalytic Chemical Vapor Deposition Synthesis.

Nitrogen doped multi-walled carbon nanotubes and other carbon nanoparticles were synthesized by catalytic chemical vapor deposition of tripropylamine and acetylene on CaCO3-supported cobalt catalyst (5 wt%), prepared by impregnation, and various precursors. Each synthesis was performed by using either the pure nitrogenous organic compound or its mixture with acetone. Transmission electron microscopy studies revealed a significant difference both in the yield and the diversity of the carbon deposits. Every synthesis resulted in bamboo-like nanotubes, and nearly all of them also in onion-like structures. Electron energy loss spectroscopy studies of the samples indicated the presence of nitrogen and calcium (caused by the catalyst support). High-resolution transmission electron microscopy and X-ray diffraction measurements were also performed to characterize the samples.

Synthesis, Characterization and Photocatalytic Efficiency of ZnO/MWCNT Nanocomposites Prepared Under Different Solvent Conditions.

Here we report the application of zinc oxide (ZnO) coated multi-walled carbon nanotube (MWCNT) composites in the photocatalytic decomposition of acetaldehyde (AA). Zinc oxide nanoparticles were successfully coated on the multi-walled carbon nanotube via impregnation process using zinc acetate (Zn(CH3COO)2×2H2O) as precursor and sodium dodecyl sulfate (SDS) treated multiwalled carbon nanotube as raw material under different solvent conditions. The applied solvents during preparation were ethanol (EtOH) and water (H2O). As-prepared materials were characterized by thermal analysis (TG), X-ray diffraction (XRD), specific surface area measurement (BET) and transmission electron microscopy (TEM) techniques. Photocatalytic efficiencies of as-prepared composites were investigated in a stationary reactor equipped with UV lamp. Decomposition of acetaldehyde was followed by using gas chromatography (GC). Observations revealed that using impregnation method and different solvents the preparation of ZnO/MWCNT nanocomposites can be controlled easily. The highest degradation rate was achieved with the nanocomposite was synthetized using ethanol as solvent. The photocatalytic experiments revealed that the composite has higher photocatalytic activity than that of both the zinc oxide nanoparticles and the mechanical mixture of multi-walled carbon nanotube and zinc oxide.

Insights into Pore Size Control in Cellulose Nanopapers Through Modeling and Experiments.

An easy way of controlling pore sizes during the preparation of cellulose nanopapers using nanofibrillated cellulose and different solvents, such as water, ethanol and acetone, was applied in this study. A possible mathematical model is also presented, that describes the occuring processes, which model is based on simple probability theory computations taking the number of possible hydrogen bonds into consideration. This model allows the better understanding of the solvent dependence of pore formation on a molecular level. For the comparison of the effects of solvents two different series of cellulose nanopapers were prepared. In the cases of both series, an aqueous nanofibrillated cellulose suspension was used for the fabrication of nanopapers, and different solvents were used for their modification. Based on scanning electron microscopy images and mercury intrusion porosimetry data it has been concluded, that using different solvents was a crucial point in controlling pore sizes. A theory about the swelling effects, as well as the formation and decomposition of nanofibrillated cellulose aggregates based on the hydrogen bonding abilities of the solvents, was proposed and proven in this paper. As-prepared nanocellulose papers can be excellent candidates for further applications as support materials (e.g., virus filtration).

Novel bioactive glass-AuNP composites for biomedical applications.

The bioactive glasses doped with gold nanoparticles (AuNPs) are very attractive materials due to their potential in medical applications. In the present study Pluronic-nanogold hybrid nanoparticles were introduced during the sol-gel route of the SiO2-CaO-P2O5 glasses preparation. The obtained samples were characterized by UV-vis spectroscopy, X-ray diffraction, FT-IR spectroscopy, transmission electron and scanning electron microscopy and afterwards they were investigated in terms of bioactivity, protein adsorption and cells viability. The in vitro bioactivity assessment shows the increase of the number of agglomerated spherical shapes of apatite layers for all Au containing samples, but apatite like structure sizes are influenced by the AuNP content. Beside the spherical shapes, three-dimensional flower-like nanostructures were observed on the surface of the glass with 0.2mol% Au2O. Zeta potential and fluorescence spectroscopy measurements evidenced that the amount of serum albumin adsorbed onto the composites surface increases with the AuNP content. FT-IR measurements point out that the secondary structure of the adsorbed proteins presents few minor changes, indicating biocompatibility of the AuNP doped glasses. The good proliferation rate of Human keratinocytes cells obtained in the presence of samples with 0.15 and 0.2mol% Au2O is comparable with the values achieved from free AuNP, fact that proves the preservation of AuNP properties after their incorporation inside the bioactive glass matrices.

Speciation study of an imidazolate-bridged copper(II)-zinc(II) complex in aqueous solution.

The solution equilibrium and the binding mode of the species in the five-component system containing two metal ions (copper(II) and zinc(II)) and three ligands (A=diethylenetriamine, B=imidazole, C=tris(2-aminoethyl)amine) were investigated by pH-potentiometric titration, UV-visible spectrophotometry and EPR (electron paramagnetic resonance) spectroscopic titration in aqueous solution in the 2-11 pH range. An imidazolate-bridged heterobinuclear complex (ACuBH(-1)ZnC) was found to evolve above pH=7 and was stable between pH 7 and 11. The existence of the ACuBH(-1)ZnC complex (by determination of its molecular weight) was proved by mass spectrometry (ESI-MS (electrospray ionization mass spectrometry) and MALDI (matrix-assisted laser desorption/ionization) techniques). The electrochemical behaviour and the superoxide dismutase activity of this complex were also tested by cyclic voltammetry and the Riboflavin/NBT (nitro blue tetrazolium) assay, respectively.