فصلنامه نانو مقیاس
سال هفتم شماره 1 (پیاپی 25، بهار 1399)

We study quantum charge and spin pumping in a graphene nanoribbon under two dephase ac gate voltages by using non-equilibrium Green’s function method. Our proposed device consists of two leads and a channel with ferromagnetic insulator. We find that, the device can pump fully spin polarized current and the spin polarization can be easily tuned by setting the Fermi energy. We also investigate the effects of width zigzag silicene nanoribbons ZSNR and compare them with zigzag graphene nanoribbon GNR and show that the pumped charge current in the ZSNR is nearly the same for odd and even numbers of silicon chains but in the zigzag graphene nanoribbon ZGNR strongly depends on nanoribbon width such that the maximum pumped current for width with even numbers of carbon chains is at least five times larger than that with odd numbers.

A magnetic metal-organic framework MOF composite, MIL-101Fe @PDopa@Fe3O4, was synthesized as the stable adsorbent for removal of Congo red CR from water. A very thin film of 3,4-dihydroxy-L-phenylalanine L-Dopa was used as an efficient and environmentally friendly binder between Fe3O4 nanoparticles and MIL-101Fe. The synthesized nanocomposite was investigated by SEM, TEM, FT-IR, XRD and TGA analyzes. Magnetic properties of the composite were studied by vibrating sample magnetometer VSM. Zeta potential analysis was also performed to determine the surface charge of the nanocomposite. Influencing factors such as pH, contact time, adsorbent dosage, temperature, and initial dye concentration on the adsorption ability of the MIL-101Fe @PDopa@Fe3O4 were investigated. The very excellent adsorption capacity about 909 mg/g for CR was achieved. Adsorption kinetics and isotherms studies indicated that CR adsorption followed Langmuir isotherm model and pseudo second-order kinetic model. Studies have also shown that The MIL-101Fe @ PDopa@Fe3O4 was found to be recyclable for removal of CR.

Zinc oxide ZnO is one of the most widely used semiconductor metal oxides with extensive applications in the manufacture of optical instruments do to its unique properties. The specificity of the films prepared by the use of this material depends directly on its deposition conditions. In this work, during the preparation of ZnO films by the pulsed laser deposition method, we fixed the volume and pressure parameters and considered the temperature factor as a varied factor by cooling down the substrate temperature to investigate the effect of thermodynamic parameters. The results of UV-visible absorption spectroscopy, microscopic and SEM images of the samples indicate that the quality of the films improves effectively under stable thermodynamic conditions.

The world´s population is rising and supplies of drinking water are declining. Water pollution by pesticides is considered as one of the environmental problemsand the removal of pesticides from water sources has been of interest to researchers. One of the methods for removing toxins from water sources is the use of catalyst and photocatalyst materials. One of the most widely used materials in this field is titanium dioxide, which has been one of great interest to researchers for its photocatalytic properties. Studies have shown that this substance is used to remove phenol. However, few studies have been carried out to remove Carbendazim. In this research, it has been attempted to study and analyze the conditions for removal and degradation of Carbendazim as a pollutant by obtaining a catalyst based on titanium dioxide with a nanostructure. For this purpose, Titanium dioxide nanoparticles were synthesized by sol-gel methodand some copper was added as a pollutant. To identify and study the X-ray diffraction patterns XRD, scanning electron microscopy SEM, infrared IR spectroscopy, porosimetry BET, ultraviolet-visible spectroscopy UV-VIS and energy X-ray Diffraction EDX was used. The results showed that the synthesized nanoparticle size was about 40-50 nm and the morphology of particles is spherical. The synthesized catalyst at 400 ° C had anatase phase. The anatase phase of this material was used for degradation of Carbendazim under photocatalytic conditions and the pH parameter was also optimized. In fact, with the increase of the copper impurity at the value of 0.5 gr, the optical band gap has decreased and the absorbance has been shifted to the bulkier wavelengths. So, titania-copper composite with anatase phase and degradation of fungicidal Carbendazim with 88 yield, it can be used as a nanostructure photocatalyst for the removal of water pollutants.

The use of hydrogen fuel is of great importance as an alternative to fossil fuels. Storage of hydrogen is one of the major challenges of using this fuel, so study of the absorption and storage of hydrogen by carbon nanotubes is essential. The absorption of hydrogen in carbon nanotubes depends on various physical factors, that the most important of these factors are temperature and pressure. The aim of this study was to evaluate the effects of temperature and pressure on the hydrogen adsorption of the nanotube bundle. In this study, the amount of hydrogen absorption on carbon nanotube bundle was studied by molecular dynamics simulation, and then analyzed pressure and temperature variations. Hydrogen adsorption simulations were carried out on a quad carbon nanotube bundle and in nine different temperatures from 50 Kelvin to 200 Kelvin. The results show that hydrogen adsorption is highly dependent on temperature and pressure, so that the amount of adsorption increases significantly at low temperatures. It was found that the amount of adsorption was constant in a carbon nanotube bundle at temperatures range of 110 to 210 K, and was linear with increasing of temperature from 50 to 110 K. The results also show that the pressure variations are linear as first order with the temperature.

In this research, alcohol oxidase was immobilized at platinum electrode surface using chitosan to design an accurate and sensitive electrochemical biosensor for detection and measurement of ethanol in liquid phase. Amperometric studies were carried out in 0.1 M phosphate buffer solution containing ethanol. According to the obtained results, the optimal conditions for biosensor operation were acquired at the temperature of 35 °C and pH 8. In order to improve the biosensor performance, gold nanoparticles were used in its construction and the comparison of obtained results from designed biosensor before and after adding these nanoparticles showed four-fold enhancement in current intensity produced by ethanol oxidation. The linear range of the gold nanoparticles modified biosensor, its Michaelis-Menten constant value, and its sensitivity were calculated to be 0.016-2.66 mM, 1 mM, and 2 µA/ mM cm2 respectively.

Electronic and optical properties of the pure and Cr-doped ZnS nanosheets have been studied via adopting a plane-wave pseudopotential approach at the DFT-PBE level of theory. It is found that adding Cr atoms as the impurity decreases the band gap down to 1.5 eV and gives rise to half-metallic characteristics. Moreover, values of the dielectric function and the extinction coefficient of the doped monolayer decrease compared to the pure one, leading to some peaks in the visible range. The loss function also takes lower values due to doping and makes the plasmon peaks shift to lower energy range. However, the refractive index has an increasing trend at low energies so that the doped nanosheet could be considered as a high-refractive index material. Increase in the reflective coefficient also indicates the higher metallic feature of the doped monolayer compared to the pure one. Furthermore, the optical reflective and the extinction coefficients vanish for values larger than 13 and 21 eV, respectively. Our results could be of great importance for improving the performance of electronic and optical devices.

Copper thin films are widely used in security sensors, medical sensors, solar panels, mode locked laser, cancer treatment, and so on. Thermal evaporation is a common technique for deposition of copper thin films. The distance between the copper source and the substrate is an important parameter that has not been investigated yet. Therefore, the effect of this parameter on the process of copper thin film deposition by thermal evaporation is investigated theoretically in this paper. The results showed that the copper vapor pressure on the substrate surface, the deposition rate and the thickness of the thin layer decreased with increasing this distance, whereas the uniformity of the film thickness improved with increasing the distance. The deposition rate decreased from 5.57nm/s to 1.12 nm/s and the thickness uniformity increases from 56 nm to 120 nm with increasing distance from 13 cm to 33 cm. Also, the dependence of thickness uniformity and deposition rate on the source-to-substrate distance were presented to select the appropriate distance according to the application of the thin layer.

 In this study CS/nFHA composite at different compositions 90/10-50/50-40/60 w/w synthesized by sol-gel method. This nanocomposite is used as biocompatible materials for bone tissue engineering. The appropriate amounts of P/F solution was added dropwise to the Ca solution to yield a stoichiometric ratio of Ca/P1.67 and P/F6. The Phase analysis, powder morphology, the bonds configuration, functional groups, thermal behaviors and biological assesment of the sinthesized samples were studied by X-ray Diffraction XRD, Scanning Electron Microscopy SEM, Fourier transform infrared spectroscopy FTIR, Thermo-gravimetric and Differential Thermal Analysis TG-DTA and Cell culture method respectively. The XRD and SEM results showed that increasing chitosan content in the composite decreased the average FHA nanocrystallite size. The results of FTIR showed the presence of flour-hydroxyapatite phase. The result of Cell culture indicates that the addition of 10 w/w FHA has a positive effect on the cell proliferation.

In this paper, adsorption and electric conductivities of Cu2O-GS and ZnO-GS nanostructures were investigated to fabricate of non-enzymatic glucose sensor. The calculations are based on density functional theory DFT. The calculation results showed that glucose is well adsorbed by Cu2O-GS and ZnO-GS nanostructures. Also, these results showed that the electrical conductivity of Cu2O-GS nanostructure increased after glucose detection. While glucose adsorption on ZnO-GS decreases the electrical conductivity. The presented work demonstrated that the Cu2O-GS and ZnO-GS nanostructures could act as effective electron mediators for the fabrication of efficient non-enzymatic glucose sensors.