سال:1395 | دوره: | شماره: |تعداد مقالات:10

Bioactive products from snail slime of “Helix” specie have potential applications in preventing and/or treating several human diseases and in cancer diagnosis. However, the poor pharmacokinetics characteristics of these natural compounds limit their use. Nanotechnology offers promising solutions for the enhanced formulation of these molecules through the synthesis of nanosized drug delivery systems. These vectors are characterized by facilitated transport across the biological barriers, enhanced bioavailability, targeted delivery and the capacity to protect sensitive compounds from biological and environmental degradation. Overall, this review focus on the description of bioactive natural substances derived from snails belonging to the genus helix and their successfully combinations with nanosized vectors.

This review paper provides researchers with a comprehensive information about the Carbon nano tubes and the catalyst parameters that influences the production and morphology of the of Carbon nano tubes. Carbon nano tubes, referred to as CNTs, are one of the most important materials used in electrical, mechanical, thermal, chemical and textile industries. Since the discovery of CNTs in 1991, many scientists, research groups, and industries have attempted to attain large scale production of CNTs, considering the costs and yields. Catalyst plays an important role in the production of CNTs. In this review various factors that affect CNT production via using different catalysts are reviewed. Factors which are important when choosing a suitable catalyst are also discussed.

In this paper, an energetic coordination compound namely pentamminenitratocobalt (III) nitrate, [Co (NH 3)5 (NO3)] (NO3)2, was used as a new precursor for the preparation of Co3O4 nanoparticles. The results showed that the complex is easily decomposed into the Co3O4 nanoparticles at low temperature (200oC) without employing a surfactant or solvent and any complicated equipment. The product was characterized by differential scanning calorimetry (DSC), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), transmission electron microscopy (TEM) and energy-dispersive X-ray spectroscopy (EDX).Optical and magnetic properties of the product were studied by UV-visible (UV-vis) spectroscopy and a vibrating sample magnetometer (VSM), respectively. FT-IR, XRD and EDS analyses con rmed the formation of highly pure spinel-type Co3O4 phase with cubic structure. TEM images showed that the Co3O4 nanoparticles are approximately in the range of 10 to 24 nm with a mean size of around 17 nm. The optical spectrum of the Co3O4 nanoparticles revealed the presence of two band gaps at 3.45 and 2.20 eV which are blue-shifted relative to reported values for the bulk sample. The magnetic measurement of the product showed a weak ferromagnetic order at room temperature.

In this study, the structures, the IR spectroscopy, and the electronic properties of AunCum (n+m£5) bimetallic clusters were studied and compared with those of pure gold and copper clusters using the generalized gradient approximation (GGA) and exchange correlation density functional theory (DFT). The study of an O2-AunCum system is important to identify the promotion effects of each of the two metals and their effect in catalysts, sensors, energy sources, or many other applications. This study also demonstrated that the O2 molecule preferred to adsorb at the Cu site rather than at the Au site in bimetallic clusters. O2 adsorption at a bridge site is energetically more favored over the other sites (1- both oxygen atoms are bonded to the same substrate atom 2- O2 is connected to a Cu atom through a single bond) for oxygen adsorption on these clusters. Further, it was concluded that after the adsorption of the O2 molecule on the bimetallic clusters, the Au-Cu interaction is strengthened and the O-O interaction is weakened, the reactivity improvement of the oxygen molecule was clear.

A high pressure drop happens when heavy oil with high viscosity moves through the oil pipeline. A variety of methods to avoid this pressure drop is available. One of which is injection of chemicals to reduce the viscosity and ultimately reduce pressure drop. Using the Pipesim software, the effect of dispersion of nano and micro-particles into the oil has been simulated to study the amount of the pressure drop pipelines. The effects of the parameters such as the type and concentration of particles, temperature, oil rate, inside diameter of pipe and the flow type were examined. Simulating the experimental data by the software, gives promising experimental results. The results show that the copper micro-particles with 0.1 wt% concentrations have the lowest pressure drop per unit length. At low temperatures the effect of concentration of micro particle is important and at high temperatures effects of temperature is dominant. It is noteworthy that in higher rates, the presence of any amount of particles has a favorable impact on the pressure drop. For laminar and turbulent flow, pressure drop will decrease when the oil viscosity decreases. On the contrary for transient flow, pressure drop will increase when the viscosity reduces.

In this paper, multi-wall carbon nanotubes (MWCNTs), gold nanoparticles (GNp) and glucose oxidase (GOD) was developed for the specific detection of glucose. MWCNTs were chemically modified with the H2SO4–HNO3 pretreatment to introduce carboxyl groups which were used to interact with the amino groups of poly(allylamine) (PAA) and cysteamine via 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide/N-hydroxysuccinimide cross-linking reaction, respectively. A cleaned Pt electrode was immersed in PAA, MWCNTs, cysteamine and GNp, respectively, followed by the adsorption of GOD, assembling the one layer of films on the surface of Pt electrode (GOD/GNp/MWCNTs/Pt electrode) and was used as working electrodes (anode) along with a platinum auxiliary electrode and the reference electrode Ag/AgCl (cathode). Working electrode was containing the Phosphate-buffered saline (PBS) with pH = 4, 6, 8 enzyme. To evaluate the performance of the constructed biosensor, it was put into a dish containing 0.05, 0.5 and 1 mmol lit-1 (mM) glucose concentrations which were dissolved in doubly distilled water. The produced current and its rate were measured by Potentiostat with transferring the electron from the working electrode to reference electrode which was released by the reaction of glucose in the presence of the enzyme. Glucose concentration and PBS pH design has been tested and analyzed by QUALTEK-4 software measure. According to the performed experiments and software analysis, with increasing concentration, the flow rate of current production is increased and pH deviance from neutral range reduces the flow. Optimal conditions was obtained in concentrations 1 mmol lit-1 and pH =6, respectively. After confirmation tests in optimum conditions, the rate of production was obtained, 21.67 mA, which with respect to the expected error rate of application, it was calculated to be 8.1%. This error rate demonstrates that the accuracy of tests is with high sensitivity and accuracy.

The effect of temperature variation on the growth of Carbon Nanotubes (CNTs) using Thermal Chemical Vapor Deposition (TCVD) is presented. Nickel and Cobalt (Ni-Co) thin films on Silicon (Si) substrates were used as catalysts in TCVD technique. Acetylene gas was used in the CNTs growth process at the controlled temperature ranges from 850-1000oC. Catalysts and CNTs characterization were carried out using Atomic Force Microscopy (AFM), Energy Dispersive X-ray (EDX), Field Emission Scanning Electron Microscopy (FESEM) and Raman spectroscopy. It was found that the CNTs diameters increased with the temperature. The CNTs diameters were continually increased from 70 nm to 180 nm in the temperature range. In addition, the degree of crystallinity of the grown CNTs decreased.

Adsorption of CO2 on the surface of Single-wall zigzag (5, 0) and armchair (4, 4) carbon nanotubes (SWCNTs) were studied through using density functional theory (DFT) calculations. Optimizations of geometric were performed at the B3PW91 level of 6-311++G** method standard basis set using GAUSSIAN 03 package of program. Structural models were optimized and adsorption energies, band gap, charge transfer and dipole momentum were obtained to investigate the nuclear magnetic resonance (NMR) and Nuclear Quadrupole Resonance (NQR) spectroscopy parameters for (CO2-CNTs) model of zigzag (5, 0) and armchair (4, 4) SWCNTs. Comparison of the results of the zigzag and armchair models with calculated chemical shielding, electric filed gradient tensors at the sites of carbon on the surface and open ended revealed that CO2 adsorption has a dramatic effect on the electronic structure of SWCNTs and adsorption on the surface is about -1.5747eV SWCNT-S (5, 0) nanotube.

In this work, hierarchical WO3 core-shell microspheres were synthesized via a facile template-free precipitation method. Gas sensing properties of the synthesized powder to acetone and some other volatile organic compounds were comparatively investigated with commercial WO3 nanoparticles. The synthesized and commercial powders were characterized by X-ray diffraction, scanning electron microscopy, particle size distribution analysis, Brunauer-Emmett-Teller and Barrette-Joyner-Halenda techniques. Gas sensors were fabricated by deposition of powders between/on interdigitated electrodes via sedimentation approach.The results show that both sensors are sufficiently sensitive to detect 1.8 ppm of acetone, diabetes diagnosis threshold in human exhaled breath. Indeed, the hierarchical based one is highly sensitive and more selective to acetone.

This paper reports the synthesis and characterization of CdS nanoparticles for investigation of photocatalytic degradation of 2, 4, 6-Trichlorophenol CdS nanoparticles were synthesized by microwave-assisted sol-gel method. Nano particles was characterized by various techniques such as X-ray diffraction, filed emission scanning electron microscopy, energy dispersive spectroscopy, fourier transform infrared spectroscopy and UV-visible spectroscopy. The average crystallite size was found to be 46 nm. The influences of catalyst amount, contaminant concentration and pH of the reaction solution were evaluated and optimized.After photocatalytic degradation, the remained of 2, 4, 6-Trichlorophenol was measured by UV-vis spectrophotometer. In the optimum condition, the highest degradation was obtained 90% after 3hours UV-C light irridiation.