International Journal of Nano Dimension
Year:2017 | Volume:8 | Issue:4|Papers Count:10

Room temperature dielectric and antibacterial behavior of thiosemicarbazide capped low dimension Silver and Gold nanoparticles were studied. The effect of size on the properties, by capping silver (Ag) and gold (Au) nanoparticles by thiosemicarbazide (TSC) was investigated. The nanoparticles were synthesized by chemical reduction method. The structural formation, surface morphology, phase stability and crystalline nature were characterized by UV-Vis spectroscopy, Fourier transform Infra Red (FT-IR) spectroscopy, Differential scanning calorimeter (DSC), Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM) and Powder X-ray diffraction (PXRD). Room temperature dielectric and Impedance spectroscopy were performed to understand the electrical transport behavior and the results indicated that TSC capped Ag nanoparticles have demonstrated better electrical properties. Also, antibacterial studies were performed on human pathogenic bacteria by agar well diffusion method which attested TSC capped Ag nanoparticles have better antibacterial properties.

In this work, Co3O4 nano rods were successfully prepared by microwave-assisted solid state decomposition of rod-like CoC2O4.2H2O precursor within a very short reaction time (6 min) without the use of a solvent/ surfactant and complicated equipment. The as-obtained Co3O4 nano rods were fully characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), Raman spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), ultraviolet–visible spectroscopy (UV–Vis), energy-dispersive X-ray spectroscopy (EDX), and magnetic measurements. TEM and SEM images showed that the Co3O4 nano rods have a length of 1-3 μm and diameter of 40-80 nm. FT-IR, XRD, EDX and selected area electron diffraction demonstrated that the nano rods are composed of pure cubic phase Co3O4. Magnetic measurements at room temperature suggested the existence of a weak ferromagnetic behavior. The optical spectrum indicated two direct band gaps at 2.20 and 3.60 eV with a blue shift compared with the bulk sample. The photo catalytic activity of Co3O4 nano rods was investigated for the degradation of methylene blue (MB) as a model of dye pollutants in the presence of H2O2 as a green oxidant. The Co3O4 nano rods showed high efficiency for the degradation of MB dye by using H2O2 under visible light irradiation. Trapping experiments indicated that hydroxyl (•OH) radicals were the main reactive species for dye degradation in the present photo catalytic system. In addition, the possible photo degradation mechanism was also proposed based on the trapping experiment results.

Multi-walled carbon nanotubes (CNTs) are synthesized with the assistance of water vapor in a horizontal reactor using methane over Co-Mo/MgO catalyst through chemical vapor deposition method. The application of Adaptive Neuro-Fuzzy Inference System (ANFIS) technique for modeling the effect of important parameters (i.e. temperature, reaction time and amount of H2O vapor) on the quality of the CNT process is investigated. Using experimental data, qualities of CNTs are determined for training, testing and validation of developed ANFIS model. From the analysis carried out by the ANFIS-based model, the mean square deviation and a regression coefficient are found to be 4.4% and 99%, respectively. The validation results confirm that the ability of the proposed ANFIS model for predicting the quality of the CNT process over a wide range of operational conditions. In addition, sensitivity analysis indicates that the temperature has the significant effect (i.e.94%) on the quality of the CNT process.

Y2Ce2O7 nano powders were synthesized via sol-gel reactions at 900 (S1), 1000 (S2) and 1100 (S3) ˚C for 4 h using yttrium acetate (C6H9O6Y.xH2O), ammonium cerium nitrate ((NH4) 2Ce (NO3) 6) and stearic acid (C18H36O2) as raw materials at stoichiometric 1: 1 Y: Ce molar ratio. The synthesized materials were characterized by powder X-ray diffraction (PXRD) technique and Fourier transforms infrared (FTIR) spectroscopy. Structural analysis was performed by the FullProf program employing profile matching with constant scale factors. The results showed that the patterns had a main cubic Y2Ce2O7 structure with space group of Fm3m. The data showed that the lattice parameters were increased with increasing the reaction temperature. FESEM images showed that the synthesized Y2Ce2O7 particles had mono-shaped sphere morphologies. However, with increasing the reaction temperature to 1100 ˚C, the particle size scale was in micrometre range. Ultraviolet–isible spectra analysis showed that the nanostructured Y2Ce2O7 powder (S2) possessed strong light absorption property in the ultraviolet light region. The direct optical band gap was calculated as 3.15 eV. Besides, the photoluminescence spectrum for the obtained material (S2) was investigated at lex=230 nm as excitation wavelength. It showed a strong emission peak at 425 nm. Catalytic performance of the synthesized nanomaterial (S2) was also investigated in alcohol oxidation reactions which showed excellent efficiency as 75%.

In this work, separation performance of supported carbon membranes produced from Novolac Phenolic resin as the main precursor and carbon nanotubes as nano filler were investigated for separation of CO2 from N2 and CH4. Supports were produced by carbonization of Novolac Phenolic resin-activated carbon mixture, and selective layer was coated by dip coating of prepared supports into solutions with different concentrations of Novolac Phenolic resin/carbon nanotubes. The composite membranes were pre-oxidized and carbonized under vacuum condition up to 160 °C and 700 °C, respectively. Carbon membranes were characterized using FE-SEM, BET, and gas permeation test. Results revealed that the best proportion of Novolac Phenolic resin/ activated carbon was 40/60 wt% to make a defect-free and applicable support, most pores of which had sizes less than 10 nm. Membranes were tested at different pressures, and the results showed that CO2 permeability increased with pressure. The carbon membrane made with 40 wt% Novolak phenolic resin and 1 wt% carbon nanotubes showed the best separation performance with CO2/CH4 and CO2/N2 selectivity of 19.5 and 18.3 in 10 bar, respectively.

We have examined the adsorption behaviors of carbon monoxide (CO) molecule on TiO2 anatase supported Au overlayers. The results of density functional theory (DFT) calculations were used in order to gain insights into the effects of the adsorption of CO molecules on the considered hybrid nanostructures. We have investigated different adsorption geometries of CO over the nanoparticles. CO molecule is preferentially adsorbed on the surface of Au atoms with significant adsorption energies. It was found that the CO molecule moves preferentially towards the Au atoms when it was positioned at the top Au sites of the nanoparticle. Here, we have focused on the adsorption of CO on the studied system, and the major point is that the charge is transferred from the CO molecule to the nanoparticle. The results suggest that the oxygen atom has a little mutual interaction with the surface Au atoms. We have summarized the results of density functional theory calculations including adsorption energies, Mulliken charge analysis and electronic density of states. Charge analysis based on Mulliken charges reveals a substantial charge transfer from the CO molecule to the TiO2 supported Au over layers. With the inclusion of van der Waals (vdW) interactions, the results show an increase in the adsorption energy values. TiO2 supported Au over layers have strong sensing capability for the detection of CO molecules, indicating the higher adsorption ability of these modified nanostructures. The goal of this study was to report on results that provide new insights, or significantly expand our understanding of the structural and electronic properties of novel TiO2 supported Au over layers for chemical sensing of CO molecules.

The p-i-n carbon nanotube (CNT) devices suffer from low ON/OFF current ratio and small saturation current. In this paper by band bending engineering, we improved the device performance of p-i-n CNT field effect transistors (CNTFET). A triple gate all around structure is proposed to manage the carrier transport along the channel. We called this structure multi-segment gate (MSG) CNTFET. Band to band tunneling (B-B tunneling) is a dominant transport mechanism in p-i-n structures which is more controlled here by band bending engineering. Gate metal at source side causes more bands bending at channel to source interface and the gate metal at drain side acts as a filter which reduces the leakage current. Results demonstrate that by parameter engineering of gate metal, the proposed structure improves the saturation current, leakage current, current ratio, sub threshold swing, breakdown voltage and cut-off frequency in comparison with conventional structure. Also, to obtain the optimum parameters, design considerations has been done in terms of difference in work functions and change in the length of each part of gates. Simulations and comparisons have been performed using none equilibrium Green’s function and self-consistent solution between Poisson and Schrodinger equations.

Nano emulsion is an alternative and promising approach to overcome insolubility and bioavailability problems of bioactive compounds. In this study, the sonication parameter for preparing nano emulsions with high a- tocopherol and linolenic acid content were optimized by using response surface methodology and their stability were evaluated during 2 months’ storage. The response surface analysis results indicated that the variability of four responses could be depicted as a quadratic function of ultrasonic processing variables. This investigation revealed that, ultrasound cavitation is a powerful promising approach for controlled production of nano emulsion with small average droplet size in a range of 94.5 ± 1.14 nm with a polydispersity index of 0.1 ± 0.022 with high a- tocopherol and linolenic acid content which are 851 ± 11.62 mg/L and 43 ± 1.27 mg/L, respectively. This study showed that applying appropriate time and intensity of low frequency ultrasound is considerable importance to maintain the nutritional value of nano emulsions in bioactive delivery system.

Dental caries is one of the most prevalent chronic diseases of people worldwide. In the development of caries a major role play bacteria of the Streptococcus and Lactobacillus genera which are acidogenic and aciduric. In this work, the antibacterial effect of silver nanoparticles was investigated on Streptococcus mutans, Streptococcus sobrinus, Lactobacillus caseiand Lactobacillus acidophilus for inhibition and inactivation of cell growth. We successfully synthesized uniformly dispersed silver nanoparticles with a uniform size and shape using salmonella typhirium. The formation of silver nanoparticles was confirmed by UV-Visible spectrophotometer, dynamic light scattering (DLS) and transmission electron microscopy (TEM). Silver nanoparticles synthesized were in size ranging 4–11 nm with an average size of 7.5 nm. Silver nanoparticles exhibited high antibacterial activity againstS. mutans, S. sobrinus, L casei and L. acidophilus and guided towards the fact that silver nanoparticles have emerged as a promising ant icariogenic agent to treat dental diseases.

Considering many applications of functionalized metal oxide nanoparticles in magnetic resonance imaging, drug delivery, neutron irradiation, electronics, catalysis and optics; herein, a new strategy is developed to functionalize magnetite nanoparticles to improve their performances in the delivery of acyclovir. In this study, magnetite Fe3O4 nanoparticles are synthesized by hydrothermal method. Then, the surface hydroxyl groups were extended by treating with TEOS (tetraethyl orthosilicate); Finally, TMPA (trimethoxysilylpropylamine) was anchored to the surface hydroxyl groups to produce amino-functionalized Fe3O4@SiO2-NH2 magnetic nanoparticles. The synthesized sample was characterized by UV-Vis, FESEM, FT-IR, and XRD. Afterward, the functionalized nanoparticles were examined in the delivery of acyclovir as an active antiviral drug model involving amine and hydroxyl functional groups. For this purpose, the amount of loading/release of the drug was investigated in different pHs, including mouth and stomach pH values. The screened experimental parameters in this study revealed that the prepared magnetite nanoparticles decorated with amine functional groups are successful in the controlled delivery of acyclovir.