فصلنامه نانو مقیاس
سال نهم شماره 4 (پیاپی 36، زمستان 1401)

Graphene as a two-dimensional material of carbon atoms in a honeycomb lattice show that this substance is applicable in nano- and micro-scale electrical devices. In this research, small graphene flakes and large area graphene were produced through micromechanical exfoliation and chemical vapor deposition (CVD), respectively. They were further transferred on silicon nitride (SiN) insulating substrates that were previously decorated by electrical contacts. These contacts were obtained by direct and reduced photolithography. Surface characterization with optical and atomic force microscopies and Raman spectroscopy determined the number, extension, continuity of layers and purity of the surface. Current-voltage and resistance measurements were carried out via dynamic and static 4-point probes, respectively. The effect of type and dimensions of the contacts, purity of the surface and the number of graphene layers were explored. Our results demonstrated linear and nonlinear voltage behavior in single-layer and multi-layer graphene sheets, respectively.

In this study, the effect of the weight percentage of multi-walled carbon nanotubes (MWCNT) and the distribution medium of carbon nanotubes were used as the main factor to investigate the rheological and viscoelastic properties of epoxy/MWCNT composites. To distribute carbon nanotubes, pure epoxy media and a mixture of tetrahydrofuran (THF) solvent and epoxy polymer were used. The quality of the distributor medium was evaluated using rheology, dynamic-thermo-mechanical (DMTA) and scanning electron microscope (SEM) tests. The results of the rheology test showed the values of G and G for the composites produced after distribution of carbon nanotubes in the epoxy/solvent environment were higher than those without solvent. After evaluating the DMTA data, it was found the highest and lowest storage modulus (ʹE) in the glass state and at 37 ℃ for nanocomposite 1-50W22.5RS and pure epoxy were obtained, which were 2855 and 2100 MPa, respectively (about 36% increase for nanocomposite). Also, nanocomposite 1-50W22.5RS, compared to a similar sample without solvent, has increased the storage modulus by 19%. The distribution of 1% by weight of MWCNT in epoxy in the presence of solvent increased the activation energy of nanocomposite 1-50W22.5RS by 26.5% compared to the sample without solvent 1-50W22.5R. The viscoelastic behaviour was modeled by drawing Cole-Cole diagrams using DMTA test results, and the Perez model was used to analyse the viscoelastic behaviour of nanocomposites. The results of tests and analysis of the Perez model showed the best rheological and viscoelastic properties were obtained for the dispersion of 1% by weight of MWCNT in THF/epoxy medium. Comparing Perez's model and DMTA data of nanocomposites, the χ parameter was estimated to be 0.47 and 0.55 for nanocomposites 1-50W22.5RS and 1-50W22.5R, respectively. This decrease indicates the proper distribution of carbon nanotubes in the epoxy field, which is consistent with results of electron microscope images.

In this study thin film composite nanofiltration (TFC/NF) membranes was prepared by interfacial polymerization between piperazine and trimesoyl chloride monomers and GOQD or SO3H-functionalized GOQD as a hydrophilic modifier. The surface morphology and hydrophilicity of the prepared NF membranes were studied by field emission scanning electron microscopy (FESEM) and water contact angle measurements, respectively. The analyses showed the rough surface and the higher hydrophilicity of the modified membranes. Also, the separation performance of the membranes was investigated by cross-flow filtration system using different salt solutions. The NF membrane modified with 0.006 wt% GOQD presented the best separation performance of 38.2% and 94.3% for two salts of NaCl and Na2SO4, respectively. By contrast, the highest water flux for the two salts mentioned above was obtained 60.1 L/m2 h and 63.1 L/m2 h, respectively, for the modified nanofiltration membrane with 0.004 wt% GOQD.The fouling resistance of the membranes was also evaluated using borine serum albumin (BSA) protein as a fouling agent, based on the water flux decline during the filtration process. After optimizing the nanofiltration membrane with GOQD, a membrane modified with GOQD-SO3H with the same weight percentage was fabricated and it was found that the presence of GOQD-SO3H in the polyamide layer improves anti-fouling properties of the membrane compared to the pure TFC membrane and membrane containing GOQD. Collectively, this study reveals that the separation performance of nanofiltration membranes can be effectively modulated through tuning the various functional groups on the GOQD surface.

The study of the structure and improvement of particle properties in nanoscale has been one of the applications of the nanomanipulation process. Atomic force microscope is one of the most efficient study tools in the field of nanotechnology with applications such as imaging, manipulation, extraction of material properties and use in lithography. In this article, in order to identify the cancerous tissue of the head and neck and in order to improve the process of recognizing and treating the disease, atomic force microscopy has been used. Research has been performed in liquid media including water, ethanol, methanol and plasma. Investigation of intermolecular forces of van der Waals, Hydration and Electrostatic double layer in different liquid environments are other important cases in this research. Finally, after the simulations, the lowest critical force and time, which is one of the important goals of the first phase of nanomanipulation, are equal to 0.759 μN and 0.299 sec in plasma, respectively, and the highest value is equal to 0.821 μN and 0.340 sec in water. High levels of intermolecular forces in the water environment have been identified as causes of high critical force and time.

In this research the electrical and mechanical properties of the flexible polyurethane-graphene (P / G) composite films were investigated. The results show that the addition of graphene (G) leads to making the conductive paths in the polymer matrix. By increasing the mass fraction of G in composition, Young’s modulus increases, as well as the tensile strength decreases. P/G with 5wt% exhibits a high sheet resistance about the human skin range, which has a good tensile strain (154%). Besides the good sheet resistance of P/G with 20wt% of G (135 Ω/sq), the relative differentiation of resistance as a function of bending angle and tensile is determined, and the results show strong reversibility and capabilities as wearable electronics and strain sensing applications.

Titanium dioxide nanotubes are electrochemically anodized on titanium foil. In the present work, a titanium dioxide nanotube membrane with an open and closed bottom is separated from the titanium substrate and a comparison is made between the dye sensitized solar cells made of them. We used the potential shock method to have open-bottomed nanotubes. The optimum shock parameters of the potential to have a strong nanotube membrane with a fully open bottom, a shock voltage of 160 V and an application time of 180 s were calculated. We show that the use of such a nanotube membrane can lead to a significant increase in the efficiency of dye sensitized solar cells (ƞ=8.73%). Intensity modulated photocurrent spectroscopy (IMPS) as well as Intensity modulated photovoltage spectroscopy (IMVS) showed faster electron transport and longer recombination time in photoanodes made of open-bottom nanotubes compared to closed-bottom nanotubes. X-ray diffraction (XRD) spectra show similar crystal properties in both structures.

Synthesizing of ZnAuO Nanoparticle is made using the sol-gel process. The sol-gel process is a friendly and green synthesis technique in gelatin media. This formula is Zn1-x Au xO, which x is equal 0.0, 0.03, 0.06 and 0.09. This component, for 2 hours, remained at fixed calcination at 650 °C temperature. Morphology and structure of these NPs were investigated utilizing transmission electron microscopy (TEM) and X-ray diffraction analysis (XRD). The decrease in intensity peaks in XRD patterns shows that the ZnO crystalline sizes decreased as the Au concentration increases that can be related to defects that occur due to the presence of Au atoms in ZnO lattice. TEM images express mono-crystalline, closely spherical NPs. By decreasing dopant concentration, the particle size of the doped samples decreases. The single crystalline nature of the samples also proved by XRD patterns, and that exhibits the hexagonal wurtzite phase. Size–strain plot (SSP) method and the Scherrer formula were used to calculate lattice strain and crystallite size. The estimated difference between SSP and Scherrer methods is because SSP calculates the strain contribution on the peak broadening, but the Scherrer method cannot demonstrate this strain contribution.

In this study, PbWO4 nanopowders were prepared by a simple and cost-effective co-precipitation method. The prepared nanoparticles' structural, optical, scintillation, photocatalyst, and antibacterial properties were investigated. X-ray diffraction (XRD) showed that the structure was successfully synthesized and assigned to the Scheelite phase with the tetragonal structure of PbWO4. The scanning electron microscope (SEM) images showed that the prepared particle's size is ~80 nm. Fourier Transform Infrared Spectroscopy (FTIR) and Energy Dispersion X-Ray (EDX) confirmed the strong bonds of related elements and the presence of Pb, W, and O elements in the structure. Luminescence studies under ion beam and ultraviolet radiation showed that the prepared nanoparticles have strong blue-green scintillation sensitivity at room temperature. The photocatalytic performance was studied using the degradation of methylene blue (MB) dye under UVA light irradiation. It was observed that the prepared nanopowder has 95.6% decolorization properties in 60 minutes under light irradiation. The physical and scintillation characteristics obtained from the synthesized nanopowders show that these nanomaterials can be used in optical applications, industrial wastewater treatment, and ionizing radiation detectors.

Failure to detect food corruption, especially meat products, will in many cases lead to food poisoning and finally cases death. Therefore, knowledge of the quality of used foodstuffs and, specially, the detection of meat products corruption can have a significant role in reducing the complications of consumption of corrosive meat products. Meat, when it begins to decompose, produces compounds known as biogenic amines such as cadaverine and putrescine. Hence, in this study, a high-precision nanosensor based on carbon quantum dots was designed to identify these as the first sign of meat corruption at the lowest possible concentration at the fastest time. When the quantum dot is exposed to a specific gas, its ability to transfer electrical current undergoes changes that can be identified by the type of gas. A stronger reaction between the gas and the surface of the carbon quantum dots will cause more changes in the structure as well as the energy levels of the adsorbent. The adsorption energy of putrescine and cadaverine adsorbed on carbon quantum dots is equal to -3.64 and -4.56 eV, respectively, which indicates a strong chemical absorption. Band gap changes of carbon quantum dots when the putrescine molecule is adsorbed on the surface is equal to 0.71 eV and when cadaverine is adsorbed it is equal to 0.59 eV.

The CuMn2InSe4 compound with a tetragonal crystal structure is one of the diamond-like compounds which has special magneto-optical properties due to the presence of magnetic ions in its structure. In order to study the structural, optical and electronica properties of this compound, we have performed first-principles calculation with the pseudo-potential method based on density functional theory. The total and partial density of states for this compound has been studied for spin-up and spin-down states. The results indicate a high magnetization and high hybridization of the orbitals of Cu atoms. Band structure results for spin-Up and spin-Down states proves the half-metallic property for this compound. Phonon dispersion investigation has been used to investigate the optical and acoustic modes. Finally, unique optical properties was observed for the electrical conductivity, absorption coefficient and reflectivity of CuMn2InSe4.

In this study, ZnO/TiO_2 : Ag composite fibers were prepared by a simple stretching method. The prepared fiber nanocomposites' structural, optical and photocatalytic properties were investigated. X-ray diffraction (XRD) results showed that the structure was successfully synthesized. Scanning electron microscopy (SEM) images showed that the diameter of the prepared fibers was about 10 micrometers. Fourier transform infrared (FTIR) spectroscopy and EDX energy scattering confirmed the strong bonds of the relevant elements and their presence in the composite structure. Increasing the calcination temperature improved the structure and purity of the composite. The photocatalytic performance of nanofiber composites for the degradation color of methylene blue (MB) under UVA light was studied. It was observed that the prepared nanofibers have suitable physical-optical properties and photocatalyst properties (98%) under UVA light exposure in 100 min for the treatment of industrial wastewater containing dyes.

In this paper, for the design and processing of electromagnetic wave absorbing Nano coatings, we have studied various factors in creating the property of absorbing waves in polymer paints and identified the materials that are commonly used in this field. In this research, the imitation-based optimization algorithm has been used. To conduct this research, first, the types of absorption methods and radar frequencies used were extracted and it was determined that by using external electromagnetic field radiation on composite materials and considering the boundary conditions of radiation waves, a different structure of materials can be observed. In this study, samples of epoxy paint and lanthanum aluminate (LaAlO3) Nano powder were applied and the absorption percentage of this sample was measured using a network analysis device. For lanthanum aluminate sample, the reflectance loss was -13.8 dB, equivalent to the absorption coefficient of 83%.