فصلنامه دنیای نانو
پیاپی 65 (زمستان 1400)

Cellulose nanofibers are widely used in medical materials, aerodynamic structures, and building industries. The lightness and heat-resistance are the most significant features of these nanofibers that result from the molecular mechanism of their assembly. Cellulose fibers are built of d-glucose monomers that are connected by glycosidic linkages. Synthesis of cellulose nanofibers in the living cells (Mainly plant cells with the cell wall) is known to be carried out by the Cellulose-Synthase enzyme. Yet the molecular mechanism of the fibers assembly that leads to large building units that are used in cell wall or other medical/industrial applications is poorly understood. Herein, atomistic Molecular Dynamics (MD) simulations were carried out to investigate the molecular mechanism of cellulose nanofiber assemblies. The simulations showed that hydrogen binding is the major interaction between these fibers. Two types of “cylindrical” and “plane” assemblies were formed by the fibers. The cylindrical assembly was shown to be the first building unit that is formed by the fibers and is maintained by a network of hydrogen bonds. While the plane is the second type of assembly that requires more than two fibers to stabilize. These in-silico findings could unravel the molecular mechanism of cellulose microfibers assemblies that could be engineered for industrial purposes.

The purpose of this paper is to obtain the threshold intensity of laser radiation for burning human tissue and also to simulate and extract graphs related to the phenomenon of multi-photon ionization caused by laser light irradiation on water in living tissue, which has many applications including medical science. Since most human tissue is made up of water, we consider water to be the target substance. To simulate the effects of laser light hitting the surface of the body, we use the "quantum photonic" theory. During simulation, photons pass through different layers. For each layer, we examine in detail the possibility of photon absorption, molecular ionization and molecular decomposition for each layer.We repeat the steps mentioned in the article for 10 layers and in each layer the percentage of ionized atoms is determined.Then, according to the obtained results, we will conclude about the intensity of radiation and the percentage of ionization.

The fast spread of COVID-19 in the world has raised as a serious threat for human health and global economy and is considered as a new challenge in medicine. In this paper, complete information is presented about treatment of viruses with the aid of nano-particles via attachment to the virus, release of reactive oxygen species, or destructive ions. In the present paper, present and potential applications of nano-technology to deal with viruses are reviewed, in the synthesis of various nano-based materials such as nano-delivery systems for treatment, personal protective equipment, and diagnostic devices. Here, the role of nano-materials in drug delivery is similar to other fields in nano-medicine; however, their intrinsic accumulation in macrophages is favorable for COVID-19. Nano-materials can be used in masks for longer usage times or air filters to ensure more protection. The new nano-based diagnostics are faster and sometimes more accurate than the traditional PCR method. The discussed nano-particle based methods for COVID-19 can also be considered for new viruses that will appear in future.

In this research, cadmium tungstate (CWO) nanoparticles were produced in two simple and low cost methods sol-gel and co-precipitation. Morphological studies and characterization analyzes by XRD, SEM, and TEM showed that the size of crystallites in sol-gel and co-precipitation methods was approximately equal (30 and 32 nm); sol-gel method produces larger nanoparticles (100 nm) with a more uniform distribution; the co-precipitation method produces smaller nanoparticles (62 nm) with a wider distribution; the aggregation rate in the co-precipitation method was higher than the sol-gel method. The characteristic of s1Na at 1070 eV in the XPS results of sol-gel nanoparticles along with the peaks of the main elements of cadmium tungstate such as Cd3d, W4f, and O1s at around 415, 40, and 537eV indicated that higher particle purity in the co-precipitation method. EDXS-map shows the uniform presence and distribution of atoms in nanoparticles, so both methods can be good methods for producing CWO nanoparticles with suitable structural properties for use in various fields, including the fabrication of photovoltaic and scintillator components.

Human survival and growth are inseparable from energy and facing serious ultimatum and threats. With the rapid growth of the world's population and the development of the global economy, the energy demand is growing. This leads to unbalanced development of the environment, energy, and population. Currently, most renewable resources are stored and transmitted as electrical energy. Energy storage using an emerging technology that can improve energy usage efficiently and be environmentally friendly at the same time has attracted widespread attention from academics and policy-makers. Batteries and supercapacitors are complementary electrochemical energy storage systems and are the most promising technologies for storing electrical energy. Metal-organic frameworks (MOF) are among the newest materials introduced in the last two decades, with the possibility of energy storage and energy conversion usage. This study mainly introduces and reviews the applications of MOF-derived metal oxide composites in batteries (Lithium-ion batteries (LIBs), Li-S, sodium-ion batteries (SIBs), and lithium-oxygen batteries (LOBs)) and supercapacitors.

Epoxy resin is one of the most important thermoset polymers due to its resistance to thermal stress and degradation, which is widely used in coatings and polymer composites. By studying the degradation kinetics of epoxy resins and epoxy nanocomposites, the temperature range and long life of the system are determined. Degradation kinetics modeling is tool for engineers to predict the thermal durability of materials before use in industry, which leads to reduced costs and quality of the designed product. The four most important factors in the study of thermal stability of epoxy nanocomposites in the presence of graphene oxide nanoplatelets are dispersion, weight percentage, type of sample preparation and aspect ratio. In this study, the effect of graphene oxide nanoplatelets and modified graphene oxide nanoplatelets on morphology, mechanical properties, thermal stability and degradation kinetics of epoxy resin has been reported.In this study, the effect of graphene oxide nanoplatelets and modified graphene oxide nanoplatelets on morphology, mechanical properties, thermal stability and degradation kinetics of epoxy resin has been reported.

Natural gas is considered as the main raw material in the chemical industry and gas refining processes are of great importance. Although methane is a major component of natural gas, there are significant amounts of other nuisance gases in addition to methane. Therefore, one of the most important stages of natural gas purification is the removal of these gases. One of these gases is carbon dioxide, which is found in gas deposits along with methane. The purpose of this project is to investigate the performance of zeolite membrane to remove this type of nuisance gases. In this regard, methane/carbon dioxide gas mixture was investigated and the process of separation of carbon dioxide from methane by MFI zeolite membrane was investigated by molecular dynamics simulation method. In order to separate this gas mixture, external hydrostatic pressure was applied to the system and the effect of temperature rise on the separation performance was examined. Also, the effect of feed composition in the separation process was investigated. The results showed that carbon dioxide molecules were able to pass through the membrane but methane gas molecules were not able to pass. Therefore, it can be said that MFI zeolite membrane can be a suitable membrane for separation of methane/carbon dioxide mixture in industry.