فصلنامه دنیای نانو
پیاپی 56 (پاییز 1398)

One of the most important issues in human societies today is environmental protection and recycling materials, and given the limited resources of oil, coal and gas that drive industrial wheels. Humanity is looking for a way to optimal use of these non-renewable industries. Porous carbon due to its high surface area and high porosity can be used in the fields: Catalytic, Recycling, Isolation, Storage, Pharmaceuticals and.The molecular design of porous carbon materials to adjust their intrinsic properties Such as: Gas and electric conduction or checking their interaction with guest molecules. This paper examines two top-down and down-and-up strategies towards the production of porous amorphous and crystalline carbon، Types of templates for the synthesis of porous carbon، Factors affect in design of porous carbon cavities، Various types of porous carbon and finally, the application of porous carbon materials.

Molecular dynamics simulation is one of the computerized computational techniques that can be used to reconstruct the fluid behavior on surfaces from molecular scale. In recent years, many researchers have been interested in investigating the wettability of nanostructures such as graphene and nanoparticles as well as metal surfaces because the control of wettability on surfaces has many applications in various sciences, especially in the manufacture of smart surfaces. Molecular dynamics simulations can be used to complement or confirm experimental data on fluid-bed interaction. In the study of wettability by molecular dynamics simulation approach, the following quantities are usually calculated as described in the present work. Contact angle, surface tension, fluid density profile on the surface, hydrogen bond number, molecular orientation, order parameter, interaction energy between fluid and surface, and diffusion coefficient. Among the above quantities, the two quantities of contact angle and surface tension are also empirically measurable and can provide valuable information about the wettability phenomenon. Due to the amount of bonding force between the water molecules and the adhesion force between the water molecules and the surface, the amount of contact angle and consequently the surface wettability are affected. Where the surface is rough, two main Wenzel and Cassie Baxter models are presented to explain the drop behavior on the surface. In Wenzel´s model, the space between the surface roughness is filled by fluid. On the other hand, fluid behavior in the vicinity of the surface is greatly affected by the nature of the surface and the determination of surface tension plays an important role in understanding the above behaviors.

Miniaturization, portability, high sensitivity, and selectivity, as well as a wide linear range, are characteristics of electrochemical sensors. In screen-printed sensors SPEs, electrode system consist of working, reference, and auxiliary electrodes are printed on a single substrate. SPEs can be the most suitable sensors for in-situ analysis, due to the fast and linear responses, low energy requirement, easy to prepare and ability to work at room temperature. The surface of SPEs can be modified with noble metals, inorganic or carbon nanoparticles, enzymes, DNA sequences, and molecularly imprinted polymers to improve their performance. A variety of bio-sensors are developed based of SPEs modified with enzymes for detection of pesticides. The electro active species are generated via enzymatic reactions and can be determined by electrochemical reactions. At the presence of pesticides, as inhibitor, the enzyme activity and electrical current are decreased, proportionally.

In this paper, a nano-sensor based on a crystalline photonic square ring resonator is designed and simulated based on the variation of silicon refractive index and resonance wavelength. This nanosensor is recommended for measuring pressure in the range of 0 GPa to 8 GPa. In order to detect the wavelength range of the pressure sensor, in the calculation of the photonic band gap, the flat-wave expansion method is used, as well as in the time domain finite difference method to obtain the operating parameters of the sensor. The sensitivity and quality factor of the designed nano pressure sensor are 8 nm / GPa and 995.55, respectively. Due to its compact size, the sensor structure is suitable for use in the nanoelectric industry of optical mechanics and nanotechnologies.

The purpose of this research is to investigate the adsorption of NO2 gas on the nanocages B12N12 and B12P12 by computational method. For this purpose, it was considered the different configurations to adsorb NO2 gas on the surface of these nanocages and it was optimized the considered structures using density functional theory DFT by M062X method and using 6-31G bases set. Then, it was calculated each of the thermodynamic parameters as well as the quantum parameters. The results relevant to the thermodynamic parameters including adsorption energies showed that the stronger adsorption was relevant to adsorption of two oxygen atoms of NO2 on two nitrogen atoms in nanocage B12N12 while it was stronger adsorption of one oxygen atom of NO2 on the boron atom in nanocage B12P12 among the different adsorption modes. It was confirmed by the quantum parameters. In addition, investigation of bonding nature by the software atom in molecule AIM showed that the most appropriate adsorption modes were van der waals weak and ionic-electrostatic strong bonding, respectively.

In this paper, electronic properties of a new carbon allotrope, named H18, have been studied using first principle calculations based on density functional theory DFT, and generalized gradient approximation GGA. This structure has a dual sp2-sp3 hybridization and composed of eighteen atoms per unite cell. Electronic properties, including band structure, electronic density of states, and charge density in different crystal planes, have been calculated. The analysis of the band structure revealed that H18 carbon phase has a metallic feature. It was observed that the atoms do not have the uniform distribution of density of states, and the largest contribution of electron density near the Fermi level belongs to the Px orbital of the C3 atoms, and the C2 atoms have almost no effect on the density of the states around the Fermi level.

Thin metal layers are of particular interest due to their wide application in the fields of solar cell, sensor, electron microscopy and spectroscopy, diagnosis and treatment of cancerous tissues, aerospace, telecommunications, lasers, automobiles, etc. In this paper, the physical vapor deposition process of aluminum Al, copper Cu, tin Sn and silver Ag functional metals is simulated and investigated by thermal evaporation using finite element method. The results showed that the type of metal has a great influence on the thickness of the thin films but the uniformity of the film thickness is independent of this parameter. Also, the variation of vapor pressure changed the thickness distribution but did not affect the uniformity of the film thickness. Finally, the deposition rate of the above metals was presented at vapor pressures of 50 and 100 Pa.