Journal of Nano Structures
Volume:8 Issue: 3, Summer 2018

Optimization of continuous synthesis of high purity carbon nanotubes (CNTs) using chemical vapour deposition (CVD) method was studied experimentally and theoretically. Iron pentacarbonyl (Fe(CO)5), acetylene (C2H2) and Ar were used as the catalyst source, carbon source and carrier gas respectively. The synthesis temperature and flow rates of Ar and acetylene were optimized to produce CNTs at a large scale. A flow rate of 30-120 sccm of acetylene and 500-3000 sccm of Ar at temperatures between 650-950 °C were examined. Using the fundamental trial and error method it was found that the maximum yield of pure CNTs can be produced at 750 °C with flow rates of 40-45 sccm of acetylene and 1500 sccm of Ar. In theoretical part, an artificial neural network (ANN) and the Bees Algorithm (BA) were used to model and optimize the CNTs production, based on the experimental data. The Bees Algorithm used the ANN as the fitness function and the optimum variables found as 60 sccm for acetylene, 555 sccm for argon and 759 °C for temperature. The computational results have relatively good agreement with the experimental results.

Optimization of continuous synthesis of high purity carbon nanotubes (CNTs) using chemical vapour deposition (CVD) method was studied experimentally and theoretically. Iron pentacarbonyl (Fe(CO)5), acetylene (C2H2) and Ar were used as the catalyst source, carbon source and carrier gas respectively. The synthesis temperature and flow rates of Ar and acetylene were optimized to produce CNTs at a large scale. A flow rate of 30-120 sccm of acetylene and 500-3000 sccm of Ar at temperatures between 650-950 °C were examined. Using the fundamental trial and error method it was found that the maximum yield of pure CNTs can be produced at 750 °C with flow rates of 40-45 sccm of acetylene and 1500 sccm of Ar. In theoretical part, an artificial neural network (ANN) and the Bees Algorithm (BA) were used to model and optimize the CNTs production, based on the experimental data. The Bees Algorithm used the ANN as the fitness function and the optimum variables found as 60 sccm for acetylene, 555 sccm for argon and 759 °C for temperature. The computational results have relatively good agreement with the experimental results.

A new chromium(III) complex containing 4ʹ-hydroxy-2,2ʹ:6ʹ,2ʺ-terpyridine (tpyOH) has been prepared by the reaction of CrCl3. 6H2O with tpyOH in the presence of metallic zinc to afford the new complex [CrCl3(tpyOH)] (1). The complex 1 was used as a suitable precursor for the preparation of Cr2O3 nanoparticles by the simple calcination method at three different annealed temperatures of 400, 600, and 800 ˚C. The structures of the products have been fully characterized by IR, powder X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) and energy-dispersive X-ray spectroscopy (EDX). The average particle size using Scherrer’s equation is calculated to be about 27-36 nm. The results suggest that temperature is an effective way to tailor the morphology and crystallinity of the prepared nanoparticles. The photophysical properties and thermal gravimetric analysis (TGA) of the complex 1 have also been investigated. The emission of 1 exhibits the high-energy intense π→π* intraligand and low-energy MLCT transitions in DMSO solution. The TGA results show the stability of the complex up to 400 ˚C after stepwise decomposition of the coordinated ligands.

Nanostructured TiO2 and S and Fe co-doped TiO2 thin films with high transparency were prepared on glass substrate through ultrasonic-assisted spray pyrolysis technique. The effects of doping on morphological, optical and structural properties of TiO2 were studied by scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), photoluminescence spectroscopy, Raman spectroscopy, and UV-visible absorption spectroscopy techniques. Because of the high uniformity and monodispersity of the prepared thin films, they have high visible light transparency. All of the prepared thin films have anatase crystal structure, however, introduction of the dopants, especially S dopant, in the lattice of TiO2 creates some structural defects in the TiO2. Because of the presence of defects as charge trapping center in the structure of the doped TiO2samples, these thin films have lower electron–hole recombination rate than undoped TiO2. Furthermore, simultaneous doping of S and Fe considerably narrows the band gap energy of TiO2.

A novel heterogeneous photo-Fenton catalyst was prepared by solid-state ion exchange Method. Synthesis of Fe-modified Bentonite (Fe-B) was performed at 100 and 200 ° C for 0.5, 1, and 2 minutes. Fe-B was characterized by scanning electron microscopy (SEM), Elemental dispersive X-ray spectroscopy (EDX) and X-ray diffraction (XRD). The activity of prepared Fe-B catalyst was assayed in the degradation of Methylene blue (MB) in the peresence of H2O2 and under UV irradiation. The effects of reaction parameters such as initial dye concentration, H2O2 concentration, Fe-B catalyst loading and initial solution pH on the degradation of MB were also investigated. Between different prepared Fe-B catalysts, the sample prepared at 100 °C and 2 min was selected as the optimum conditions for synthesis. Under Optimal conditions (pH=4.0, 200 ppm H2O2, and ), ~100% discoloration of 200 ppm MB can be achieved in 90 min. The result of reusability studies shows the acceptable reusability of the catalyst. These results were satisfactory to recommend Fe-modified Bentonite prepared by solid-state ion exchange method as a novel catalyst.

Multi-walled carbon nanotubes (MWCNTs) were immobilized on the surface of a glassy carbon electrode (GCE) in the presence of cetyltrimethylammonium bromide (CTAB) to form a MWCNTs-CTAB nanocomposite-modified electrode. The electrocatalytic response of the modified electrode towards tryptophan (Trp) was investigated by cyclic voltammetry (CV) and differential pulse voltammetry (DPV). The surface morphology of the modified electrode was characterized by scanning electron microscopy. Under the optimized conditions, a significant electrochemical improvement was observed toward the electrooxidation of tryptophan on the modified electrode surface relative to the unmodified electrode. The limit of detection of 1.6 µmol L-1 (S/N = 3) and linear calibration range of 4.9 – 64.1 µmol L-1 was obtained for tryptophan determination using a differential pulse voltammetric method in phosphate buffer (0.1 M, pH 3.0). Real sample studies were carried out in human blood serum, which offered good recovery (94.1-104.08%). The electrode showed excellent reproducibility, selectivity and antifouling effects.

Synthesis of organic compounds using nano-catalysts is more and more attention due to the numerous advantages such as cost-effectiveness, high catalytic activity, ease of product separation, recovery of the catalyst, repeated recycling potential and good stability. In this work, TiCl2/nano-γ-Al2O3, as a novel type of green heterogeneous solid acid was prepared by the immobilization of TiCl2 on the surface of nano-γ-Al2O3 and characterized by Fourier transform-infrared spectroscopy (FT-IR), X-ray diffraction (XRD), field emission-scanning electron microscope (FE-SEM), energy dispersive X-ray (EDX), X-ray fluorescence spectroscopy (XRF), Brunauer–Emmett–Teller (BET) and thermal gravimetric analysis (TGA). One-pot multicomponent reactions (MCRs) have been extensively studied for their simple procedures, high selectivity, and superior atom economy. The activity of TiCl2/nano-γ-Al2O3 was probed via the synthesis of 1,4-dihydropyridine derivatives of three components coupling reaction of aldehyde, 1,3-dicabonyl compound and ammonium acetate under solvent free condition with excellent yields in short time. The obtained 1,4-dihydropyridine derivatives were characterized by FT-IR and 1H NMR spectra.

Today, Li-ion batteries (LIBs) are the most common rechargeable batteries used in electronic devices. SnO2 with theoretical specific capacity of 782 mAh/g is among the best anode materials for LIBs. In this report, Three-dimensional SnO2 nanowires (NWs) on carbon nanotube (CNT) thin film (SnO2 / CNT) is fabricated using a combination of vacuum filtration and thermal evaporation techniques. The resulting 3D heterostructure SnO2/CNT was characterized by X-ray diffraction, transmission electron microscopy (TEM) and scanning electron microscopy (SEM). This fabricated SnO2/CNT electrode has been tested as a flexible and binder-free anode for LIB, which exhibits high initial discharge/charge capacity of 4.8/2.25 mAh/cm2 at a current density of 0.25 A/g, much larger than discharge/charge capacity of bare CNT film (2.2/0.3 mAh/cm2). Relatively high areal capacity of 1.23 mAh/cm2 has been achieved for the fabricated LIB with SnO2/CNT electrode after 20 cycles, proposing this material as a high performance flexible LIB anode material.

In the present study, a step by step process was applied to synthesize bimetallic electrocatalyst (Ru and Pt on VulcanXC-72R). This process can reduce the amount of platinum and increase the gas diffusion electrode (GDE) performance in the cathodic reaction of polymer electrolyte membrane fuel cells (PEMFCs). Using the impregnation by hydrothermal synthesis method, a series of electrocatalysts with different molar ratios of metals (Pt and Ru) were prepared and applied in the electrode fabrication process. The performance of the electrodes in Oxygen Reduction Reaction (ORR) was studied using electrochemical methods such as, linear sweep voltametery (LSV), electrochemical impedance spectroscopy (EIS), chronoamperometery techniques, and the membrane electrode assembly (MEA). Also, inductive coupled plasma (ICP), X-ray diffraction (XRD), and transmission electron microscopy (TEM) were employed to characterize the synthesized electrocatalysts. The obtained results indicated that the electrocatalyst with 1:1 molar ratio for Pt:Ru enhanced the cathode performance. This can be attributed to the positive effect of Ru on electronic properties of Pt along with the effect of catalyst distribution on the substrate which consequently provides the best three-phase zones.

In this present study, an environmentally friendly and rapid method for the synthesis of silver nanoparticles (SNPs) has been reported using Ziziphus Vulgaris (ZV) unripe fruit extract under mild conditions. The synthesized silver nanoparticles have been characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), fourier transform infrared spectroscopy (FT-IR) and ultraviolet-visible spectroscopy (UV–vis). Transmission electron microscopy analysis confirmed that the synthesized SNPs have spherical shape and their average size is about 20 nm. Moreover, antioxidant activity, total phenolic and flavonoid content of unripe fruit and seed were analyzed by DPPH free radical-scavenging, Folin Ciocalteu and aluminum chloride (AlCl3) assays, respectively. Different extracts of unripe fruit showed higher antioxidant activity, total phenol and flavonoid than seed of Ziziphus vulgaris. Moreover, antioxidant activity, total phenolic and flavonoid content of unripe fruit and seed were analyzed by DPPH free radical-scavenging, Folin Ciocalteu and aluminum chloride (AlCl3) assays, respectively. Different extracts of unripe fruit showed higher antioxidant activity, total phenol and flavonoid than seed of Ziziphus vulgaris.

TiO2 is a very well-known and well-researched material due to the stability of its chemical structure, biocompatibility, and its physical, optical and electrical properties. In this study, the synergistic effect of nano-TiO2 immobilized on activated carbon, zeolite Y and ZSM-5 on the removal of styrene vapors from polluted air was investigated. The prepared catalysts were characterized by SEM, BET and XRD analysis. The enhanced photocatalytic activity of AC, ZSM-5 and Y zeolite for the degradation of the styrene was attributed to the synergistic effect of TiO2. Photodegradation experiments were carried out at ambient temperature, different styrene concentrations (20, 100 and 300 ppm) and inflow of 0.5 l/min. The results indicate that adding TiO2 to the adsorbents increased the removal efficiency of styrene and among these catalysts; AC-TiO2 had a better performance. The high catalytic activity of AC-TiO2 should be attributed to the interaction between AC and TiO2, which provides the appropriate ability to adsorb reactants by AC and catalytic oxidation of styrene by TiO2. Better performances with this promising material – TiO2 deposited onto AC, ZSM-5 and Y zeolite – compared with bare TiO2 could be explained by the vicinity of photocatalytic and AC, ZSM-5 and Y zeolite adsorption sites. According to the results obtained from the adsorption capacity and the breakthrough and removal efficiency of catalysts, it can be concluded that coated adsorbents (AC, ZSM-5 and Y zeolite) with TiO2 can enhance the removal efficiency of styrene.

Common bean (Phaseolus vulgaris L.) is one of the most important and widely cultivated Legume in the world. The two-spotted spider mite (TTSM), is one of the most important agricultural pests. This research provided some evidence of the applicability of CuO nano particles and nano capsule for controlling TTSM. To evaluate the effect of copper nano-capsules on the populations of TSSM from red beans, Akhtar variety was used. This bean is a susceptible variety. To evaluate the effect of copper nano-capsules on the populations of TSSM from red beans, Akhtar variety was used. This bean is a susceptible variety. Five experiments were carried out, including spraying with copper nanocapsule (Cu2O) at 5 levels of concentration (1) without nano-capsule copper (2) nanocapsules 1 g / l (3) nano capsules 2.5 g / l (4) nano capsules 4 Grams per liter 5. Nanocapsule was 5.5 grams per liter. The time of spraying was the simultaneous appearance of the first flower buds in each plant. According to the results, the use of copper nanocapsules has a significant effect on decreasing population of the pest. This can be different by change the concentration of nanocapsules. Copper oxide nanoparticles were first synthesized via a fast precipitation method. The prepared products were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Fourier transform infrared (FT-IR) spectroscopy.