فصلنامه نانو مقیاس
سال نهم شماره 3 (پیاپی 35، پاییز 1401)

Terahertz electromagnetic emission is useful for many applications, including imaging and spectroscopy. In this paper, the emitter is optimized with respect to layer thickness by modeling the terahertz emission field. the effect of sapphire, glass, W and MgO substrates on the optimal thickness of the Fe/Pt spinterahertz emitter was investigated. The model used in this paper considers spin polarization, spin scattering and spin accumulation in Fe and Pt layers, and the electrical and optical properties of the layers.

In this paper, the optical properties of nanosheet and (6,6) armchair As2GeSe nanotube (the real and imaginary part of dielectric function, spectrum of energy loss, refractive index, extinction coefficient, and absorption coefficient) are investigated based on the density functional theory. The results obtained from the optical properties of the nanosheet show the anisotropy of this compound, especially at low and middle energies. The behavior of the dielectric function of this material is like a semiconductor material. The main peaks of the imaginary part of dielectric function for in-plane and nanotube growth directions start from low energies up to about 6 eV. The optical transmissions below the Fermi level are associated with the p-orbitals for the As, Ge, and S atoms and above the Fermi level to the p-orbitals of the Se and As atoms. Our results show that the highest reflectance for both in-plane-direction at the energy of 5.66 eV is 46%.

Due to the unique properties of core shell nanostructures and the fact that different advantages can be achieved simultaneously, in recent years core-shells has received much attention. The synthesis method presented in this research is based on electrostatic adsorption between the core and the shell, which is a new method in the synthesis of core shell nanostructures. This method has advantages such as simplicity, high speed, high quality, repeatability and no need for complex preparation steps.Silica nanoparticles were synthesized by Stober method and after surface modification by APTES, which is a surfactant; it was used as a mold. The Unique dual core shell nanostructure of the silica-gold-platinum synthesized based on the electrostatic adsorption between the core and the shell.Field emission scanning electron microscopy (FE-SEM), high-resolution transmission electron microscopy (HR-TEM), elemental mapping, X-ray diffraction (XRD) pattern and Fourier transforms infrared spectroscopy (FTIR employed to characterize the structures.

Herein, a facile, nontoxic, economic and fast green synthesis method was utilized to prepare carbon quantum dotes (CQDs). The CQDs were prepared via microwave-assisted hydrothermal method using Ferula assa-foetida. plant as carbon source. The effects of microwave power and irradiation time on optical and photoluminescence properties of CQDs were investigated. The CQDs prepared under optimum power and irradiation time (100 W, 10 min) have the average diameter of ~ 6 nm and emitted a bright blue light, when they were excited under a UV light with λex = 360 nm. The florescent quantum yield (QY) of the CQDs was 33 % which is higher than other CQDs prepared by bio-source carbons. FTIR and SEM-EDS mapping results confirmed the presence of nitrogen and sulfur elements in the CQDs structure. The CQDs were implemented into polyvinyl alcohol (PVA) matrix to prepare PVA-CQDs films. The prepared films also emitted an intense bule light with CIE index of (0.185, 0.121). The green-synthesized CQDs and PVA-CQDs film via a fast, facile and economic approach, have great potential to be used in various application fields.

Separation of oil derivatives and contaminants from water is one of the important fields in industry and industrial oil wastewater treatment. Synthesis of nano micro-mineral structures on porous materials is a very effective method to separate petroleum derivatives from water under relatively high temperatures and pressures. In this study, cobalt-phosphorus nanostructures were deposited on nickel foam using a single-step electrochemical method. Then, after cobalt-phosphorus deposition process on nickel foam, two types of diesel oil and edible oil solutions were investigated to separate the oil from the water. In this method, the effect of sodium hypophosphite concentration and application of pulse voltages on the electrolyte was investigated. Different concentrations of sodium hypophosphite were created in the amount of 100 mM, 300 mM, 500 mM and without sodium hypophosphite in the electrolyte solution. It was then coated on nickel foam. The morphology and identification of the coatings were investigated using field emission scanning electron microscopy, energy dispersive X-Ray analysis, Fourier transform infrared spectroscopy, X-ray diffraction pattern, atomic emission spectroscopy and contact angle. Next, the performance of oil separation from water was investigated using weight separation efficiency and oil contact angle.

In this article, turbulent flow characteristic of GO-water nanofluids is thoroughly reviewed. Also presents the effects of some important parameters such as, GO nanoparticles concentration, and Reynolds number on heat transfer rate. The range of nanofluid concentration is considered as 0.0%-1.0% of volume concentration and in a double tube heat exchanger counter flow under turbulent flow conditions which Reynolds number of the turbulent flow is chosen between 80000 and 180000; the effect of graphene oxide nanocatalysts on heat transfer has been investigated. The viscosity of nanofluid has a maximum of 23% increase in comparison to the base fluid (water). There was a 25.4% growth in thermal conductivity in the present nanofluid compared to the minimum amount of that for water. Considering the data obtained from this study, the Nusselt number, the convective heat transfer coefficient, the friction factor, and the thermal performance coefficient are investigated. In order to validate the data, the results of this study are compared with preceding studies and experimental data. Maximally, the nanofluid has a 23% increment in the friction factor, 69.7% augmentation in the convective heat transfer coefficient, 37% growth in Nusselt number in comparison to the base fluid. However, the thermal performance coefficient maximally increments by 1.85. According to the achieved results, the present nanofluid can be used in heat exchangers.

The aim of this study is to investigate the adsorption of mercaptopyridine (MCP) on the surface of pristine and Co doped boron phosphide (B12P12) nanocage using density functional theory. For this purpose, different positions of mercaptopyridine (MCP) are considered on the surface nanocage and then all the considered models are optimized using cam-B3LYP / Lanl2DZ method by Gaussian software (09). Using optimized structures, geometrical parameters, quantum, thermodynamic, and electronic parameters are calculated and the results are analyzed. The results showed that due to MCP adsorption, the electronic structure of the nanocage changes and the energy gap between HOMO and LUMO orbitals and global hardness of system decrease significantly, which increases the conductivity and reactivity of the nanocage. This results suggests that Co doped nanocage could be a good option for MCP sensors in biological systems. The calculated results of the adsorption energy and thermodynamic properties of the system show that the adsorption of the drug on the nanocage is favorable and this nanocage can be used as a carrier of the drug in the biological system in the human body. The results of quantum atom theory in molecules (QAIM) and reduced density gradient (RDG) parameters show that the bond of MRC drug on the surface of nanocage is electrostatic type.