Journal of Nano Research Vol. 62

Abstract: We report our experiments based on the interfaces of a 5-period superlattice, containing GaAsP(3Å)/GaAs (190Å) heterostructures grown by molecular beam epitaxy (MBE). The atomic arrangement at the interfaces of GaAsP/GaAs is investigated using high resolution transmission electron microscopy (HRTEM). Our results indicate that the superlattice was grown coherently with strained layers. We propose that the atomic arrangement at the interface is GaP, assuming that phosphorus incorporation occurs primarily via substitution due to desorption of arsenic at the surface for substrate temperatures above 500°C. The incorporation of phosphorus has been investigated using fast Fourier transform (FFT) patterns and shows a form of strain distribution near the heterointerface. The FFT patterns of the superlattice reveal that strain distributes mostly near the interface and gradually decreases along the direction of growth. Phosphorus diffused into a GaAs layer changes the lattice constant in the growth direction, which reduces strain in the superlattice.

Abstract: Owing to its simple crystal structure, tetragonal FeSe has been considered as a perfect candidate for investigating the interplays among the superconductivity, magnetism and structural phase transition. Previous works had revealed that superconductivity could only be seen in samples with Se deficiency for the otherwise ferromagnetic tetragonal FeSe. In this study, we investigated the effect of vapor transport annealing on the crystalline quality of FeSe films deposited on flexible muscovite (mica) substrates by pulsed laser deposition. The annealing processes were conducted by sealing FeSe powder in tandem with the as-deposited FeSe films in a quartz tube. The FeSe powder was placed at a distance of about 18.5 cm from the FeSe films and the entire sealed quartz tube (about 1.2 cm in diameter) assembly was put into a Lindberg three-zone furnace and maintained a temperature gradient between the two ends of the quartz tube. The results showed that FeSe films successfully grown on flexible mica substrates and the annealing did improve the morphology and crystallinity of the films, however, the films appeared to have more inhomogeneous phases. We suspect that this might be due to uncompleted FeSe phase nucleation in non-optimum condition. The interface between the muscovite substrate and the FeSe films also could be the caused of the formation of other impurity phases, such as FeSe₂ and Fe₃Se₄. Consequently, the obtained films exhibited only paramagnetic behaviors, and there was no sign of zero-resistance down to 2 K.

Abstract: CuO nanorods were fabricated by a facile microwave-assisted synthesis method and applied to pseudo-capacitor. The CuO nanorods were characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. The capacitive behavior of nanorods was investigated by cyclic voltammetry and galvanostatic charge–discharge measurements. Electrochemical experiments reveal that CuO nanorods demonstrate better capacitance performance than granular CuOs prepared by chemical precipitation method. The CuO nanorods have a high specific capacitance of 317 F/g at a current density of 1 A/g and a fairly good cyclic stability.

Abstract: The main objective of the present study was to investigate the application of Box–Behnken design which is a type of optimization design of response surface methodology (RSM) to predict and optimize some aging condition of magnesium silica aerogel (MSA) for improving surface properties such as surface area, pore volume and pore size. Brunauer-Emmett-Teller (BET), Barrett-Joyner-Halenda (BJH), Fourier Transform Infrared spectroscopy (FTIR), Scanning Electron Microscopy (SEM) coupled with Energy Dispersive Spectroscopy (EDS) techniques, tap density method and helium pycnometer were used to characterize aerogels. The operating conditions were optimized as a function of the molar ratio of Mg:Si (0.35, 0.50 and 0.65), aging time (24 h, 60 h and 96 h) and aging temperature (50 oC, 70 oC and 90 oC). Lack of fit test indicates that the quadratic regression model was significant with the high coefficients of determination values for all three properties. Optimized aging factors for synthesis MSA with high BET surface area, high BJH pore volume and average BJH pore size were found to be 0.5 Mg:Si molar ratio, 79.62 oC and 61.51 h, respectively. Under these conditions, magnesium silica aerogels have great properties: 734 m².g^-1 BET surface area, 0.41 cm³.g^-1 BJH pore volume and 4.91 nm BJH pore size, 0.12 g.cm⁻³ density and 95 % porosity. Box-Behnken is useful optimization tool for production of nanoporous magnesium silica aerogel.

Abstract: Analytical modelling for a tri material cylindrical gate tunnel FET is developed in this paper. Poisson equation and parabolic approximation technique are employed to develop the analytical model of the proposed device. Inorder to eliminate the influence of short channel effects and the leakage current, a surrounding gate with three different work function materials is used. Stacked dielectric or hetero-dielectric is used to improve the ON current of device. Performance of the device has been analyzed with different gate material lengths such as 10 nm, 15 nm and 20 nm. The developed 2-D mathematical model is used to obtain results like drain current, surface potential and electrical field in the vertical and lateral direction. From the results, a reduction in the device limitations is inferred and the leakage current is also considerably reduced. It has been found from the presented results that the proposed device structure Tri Material Cylindrical Gate Tunnel FET (TM CG TFET) provides the improved ON state current (10^-3A/µm) and reduced OFF state current (10^-14A/µm). The accuracy of the results and characteristics of the device are evaluated using TCAD simulations.

Abstract: In the present study, the hybrid nanoflower PON1-Ca²⁺ (hNF-PON1) structure was synthesized and characterized and some antilipid drugs effects were investigated on hybrid paraoxonase (PON1) activity. Firstly, the hPON1 enzyme was purified 304.5 fold with 76.4% yield from human serum using the triple phase separation technique (TPP). Then, the hNF-PON1 was prepared in a one-step procedure using biomimetic mineralization. The catalytic activity of the hybrid enzyme with an 88.49% binding rate increased by 26.40%. The characterization of hNF-PON1 structure was performed with SEM, TEM, EDX, FT-IR and XRD analyzes. The effects of some lipid-lowering drugs (Valeric acid, phenoxy – isobutyric acid, N-desmethyl rosuvastatin) were also investigated on the activity of hNF-PON1 enzyme. When the re-usability of the enzyme was tested 10 times in succession, the enzyme was determined to protect the activity by 60%. Inhibition kinetics (IC₅₀ and Ki values) of hybrid structure was determined. In the last stage of the study, the potential toxic effect of hNF-PON1 structure was evaluated using zebrafish embryos. To this end, zebrafish embryos were exposed to hNF-PON1 with 50-2000 ppm concentrations and monitored at 24, 48, 72 and 96 hpf. Survival rate, hatching rate and body malformations were evaluated during this period and it was determined that the hNF-PON1 structure did not exhibit any toxicity on zebrafish embryos.

Abstract: In this work, a low-cost method to produce ZnO nanostructured materials for the treatment of water polluted with model organic pollutants (e.g. dyes) is presented. Zinc and silver-coated Zn (Ag/Zn) films, fabricated via sputtering method were naturally oxidized via a simple, low-temperature, scalable thermal process. During oxidation, Ag/ZnO nanorods were grown on Zn foils after treating their surface with various agents (e.g. acids) and annealing in an oven at temperatures 385-400 °C. The ZnO and Ag/ZnO films on Zn were characterized by X-ray diffraction, scanning electron microscopy and photoluminescence spectroscopy. The cationic dye Methylene Blue (MB) was selected as model pollutant dissolved in water, and a batch photo-reactor was fabricated and used to to study the adsorption capacity and photocatalytic performance of films. The transient varation of MB concentration in aqueous solutions was measured with UV-Vis spectroscopy. Ag/ZnO demonstrated a strong MB adsorbion capacity in dark conditions, and a satisfactory MB photocatalytic degradation under UV light irradiation.The optimized doping of Ag in Ag/ZnO film enhanced its photocatalytic activity, and seems well-promising for the potential scale-up of Ag/ZnO films, and use in large-scale systems for water purification under UV light irradiation.

Abstract: In this work, we studied the ZnO film thickness effect on the photocatalytic performance of n-ZnO/p-NiO heterostructures. The ZnO and NiO films were prepared by sol-gel dip-coating technique and the thickness of the ZnO film was varied by changing the number of coatingsfrom 2 to12. The formation of the p-NiO/n-ZnO heterostructure was confirmed by X ray diffraction (XRD). The obtained ZnO films present a wurtzite structure with a preferred orientation along (002) direction while the NiO film present a cubic structure highly oriented along (200) direction. UV-visible transmittance spectra of the prepared heterostructures revealed a good transparency in the visible region. The photocatalytic propertiesof the n-ZnO/p-NiO heterostructures were investigated by measuring the degradation rate of methylene blue. All the samples exhibit a good photocatalytic activity under solar light irradiation. The photocatalytic activity of p-NiO/n-ZnO heterostructureswas strongly correlated with the number of ZnO coatings. The highest photocatalytic activity was obtained at 6 coatings with a degradation rate of methylene blue equal to 98.67% for 4.5h of irradiation.

Abstract: This study attempted to evaluate the physicochemical characteristics of essential oil nanoliposomes from three plants by two preparation methods including thin film sonication and heating. Also, the durability of fumigation toxicity of the essential oil nanoliposome and pure essential oil of Mentha pulegium against Tribolium castaneum Herbst adults were compared. The smallest mean size of the nanoliposome was prepared by the thin film sonication method (P<0.05). The encapsulation efficiency of the nanoliposome was higher than 96%. Nanoliposmes prepared by using two methods showed high stability during storage. The release profile of essential oils at the heating method showed that the essential oil diffusion from the nanoliposome was in the following order: Mentha pulegium > Ferula gummosa > Zattaria multiflora. These findings indicate that both preparation methods had the same effect on the formation of nanoliposomes, their characteristics, and their storage stability. The durability of fumigation toxicity of the nanoliposome M. pulegium essential oil had a significant effect on mortality of T. castaneum adults in comparison with pure essential oil of this plant. The result showed that nanoliposome encapsulation of M. pulegium essential oil significantly increased fumigation toxicity against T. castaneum. Therefore, essential oil encapsulation into a nanoliposome carrier can potentially be used in pest management.

Abstract: The present paper investigates the nonlocal buckling of Zigzag Triple-walled carbon nanotubes (TWCNTs) under axial compression with both chirality and small scale effects. Based on the nonlocal continuum theory and the Timoshenko beam model, the governing equations are derived and the critical buckling loads under axial compression are obtained. The TWCNTs are considered as three nanotube shells coupled through the van der Waals interaction between them. The results show that the critical buckling load can be overestimated by the local beam model if the small-scale effect is overlooked for long nanotubes. In addition, a significant dependence of the critical buckling loads on the chirality of zigzag carbon nanotube is confirmed, and these are then compared with: A single-walled carbon nanotubes (SWCNTs); and Double-walled carbon nanotubes (DWCNTs). These findings are important in mechanical design considerations and reinforcement of devices that use carbon nanotubes.