فصلنامه نانو مقیاس
سال هشتم شماره 4 (پیاپی 32، زمستان 1400)

This work proposes and presents a study of a negative-capacitance field effect nano transistor (NCFET) based on two dimensional α-In2Se3 as the ferroelectric in order to reduce the sub-threshold swing. Phase transition as well as Curie temperatures of monolayer α-In2Se3 were studied, by employing Monte Carlo and ab-initio molecular dynamics simulations. The estimated Curie point is above room temperature, making monolayer α-In2Se3 a promising candidate for negative-capacitance field effect nano transistor devices. The Landau constants of monolayer α-In2Se3 are extracted which were utilized for analyzing the characteristics of a negative capacitance-field effect transistor with a monolayer MoS2 as the channel material. Sub-threshold swings in the range of 27-59 mV/dec for ferroelectric thicknesses between 25-5 nm were achieved.

MoSe2 two-dimensional nanostructure is a suitable candidate for optoelectronic applications due to its unique properties such as high absorption and direct band gap. One way to increase the absorption in such a monolayer is to place it as a defect in one-dimensional photonic crystal (PC). The location of defect in the PC can form either symmetrical or asymmetric PC, which affects the number and frequency of defect modes. In this paper, in order to achieve high absorption and adjustability of the defect mode wavelength, the effect of defect layer thickness, PC layers thickness, and periodicity are investigated in both symmetric and asymmetric PCs. In the optimal design, we have achieved a perfect absorption in the asymmetric structures with one defect mode in the middle photonic band gap and in asymmetric PCs with two defect modes the absorption was found to be 70%~80% On both sides photonic band gap. By changing the thickness of the defect layer and the wavelength of the design, the wavelength of the defect mode can be adjusted, which is useful for application in detectors and absorbent filters.

In this study a graphene oxide nanoparticles were synthesized based on the temperature-sensitive absorbent to selectively absorb diazinon from aqueous solutions. Infrared spectroscopy (FTIR), morphology (SEM) and thermal balance analysis (TGA) techniques were used to detect nanosorbent functional groups. Using these techniques, it was observed that the amine functional group was formed on the surface of the nanosorbent.To find the optimal removal conditions, the effect of effective parameters such as pH, temperature, adsorbent amount, initial analyte concentration and contact time were tested. The concentration of residual diazinon in aqueous solution was measured by Uv-Vis spectrophotometry. The synthesized nanosorbent can be used 7 times repeatedly to extract diazinon. Also, studies on absorption isotherms have shown that diazinon uptake follows the Langmuir equation. The application of synthesized nanosorbents in real samples indicates the high efficiency of this adsorbent in the selective removal and extraction of diazinon from aqueous environment.

In this research, first sila-fullerene and sila-fullerane structures have been investigated, then in terms of chemical properties, they have been compared with the corresponding carbon structures. Our findings show that silicon enters the fullerene structure only by decreasing symmetry, even at smaller sizes of fullerene geometry, it cannot form a stable structure. However, sila-fullerenas are as symmetrical and stable as carbon fulleranes; and also, have high chemical hardness and electron affinity, these two features make them suitable for use in chemical sensors. The electronic properties of the studied structures have been performed with density functional theory (DFT) under functional and basis set of B3LYP/6-31+G(d,p), and Time-dependent DFT calculations have been used to obtain the UV-VIS spectrum.

A major use of quantum dots (QDs) is their use in the development of biomedical nanosensor applications.Bioimaging, targeted drug delivery, and photodynamic therapy are main aspects of the applications of these materials.Four factors determine that which QDs are suitable for use in nuclear medicine applications as theranostics: (1) the ability to accumulate in tumors, (2) cytotoxicity, (3) ability to bind with radioisotopes and (4) fluorescence behavior. In this study, the bactericide effects of different concentrations of QDs sample (CdTe/CdS, CdTe and CdTe/Gd) were evaluated on pathogenic bacteria (E. coli (PTCC 1330), S. typhi (PTCC 1609) and P. aeruginosa (PTCC 1707)). The results showed that altering core/chell structures of QDs affected the toxicity of them considerably.

In this study, the localized surface plasmon resonance of Copper and Cobalt quantum dots embedded in diamond-like Carbon films, fabricated through radiofrequency plasma-enhanced chemical vapor deposition, were investigated. In addition, the Cobalt and Copper nanoparticles were fabricated through radiofrequency and direct current sputtering methods via co-deposition in a simultaneous sputtering process. Then, the ultravioletvisible-near-infrared spectroscopy, energy dispersive x-ray spectroscopy, atomic force microscopy and field emission scanning electron microscopy were used to analyze the samples and the effect of changes in sputtering conditions on plasmon resonance of Copper and Cobalt quantum dots were also studied. The results showed that the localized surface plasmon resonance of Copper and Cobalt quantum dots embedded in diamond-like Carbon occurred at wavelengths of about 600 and 230 nanometers, respectively. Furthermore, the simultaneous sputtering of elements led to the formation of two types of spectra from plasmon resonance of the samples.

In this work, self-coloured nanocomposites containing Azo functional groups based on polyamide (PA) reinfoced with surface modified magnesium hydroxide nanoparticles were prepared, and their structure and properties were investigated. PA was synthesized by direct polycondensation and its structure confirmed by FTIR and NMR. The solubility test results indicated that the synthesized PA easily dissolved in aprotic organic solvents such as dimethyl formamide (DMF) at room temperature. Modified magnesium hydroxide nanoparticles (MMH) were prepared via two steps including coprecipitation reaction and then surface modification in the presence of azo dicarboxylic acid. Nanocomposites (PAN) were prepared with PA and appropriate amounts of MMH via casting solution method. The results of XRD and FE-SEM indicated that nanoparticles were uniformly dispersed in the PA matrix. Thermal properties of PA and related nanocomposites were studied by using thermogravimetric analysis (TGA). According to TGA results, MMH had a good effect on the thermal stability of polyamide. With addition of 8 mass% of modified nanoparticles in the PA matrix, T5 and T10 values increased 30ᵒC.

One of the most widely used structures in nanotechnology, which has entered the field of biological sciences, are carbon nanotubes, which due to their small size, special ability to cross the cell membrane, can be used as a drug carrier to identify and kill cancer cells. In this research, to achieve better biocompatibility, the addition of some chemical groups to carbon nanotube was studied using molecular dynamic simulation, which resulted in improved targeted drug delivery performance by surface modification. Also, to evaluate the effect of functional groups, first, the nanostructure without functional group along fluorouracil anticancer drug was investigated. Among the analyzes used to investigate the drug-carbon nanotube interaction with the POPE lipid bilayer membrane in the aqueous medium, we can mention the mean squared displacement, etc that Among these, the analysis of the radial distribution function to compare the water concentration around carbon nanotube and Mass center distance analysis was performed to evaluate the stability of the drug inside the carbon nanotube and then the diffusion coefficients of the carbon nanotube-membrane were compared with different chemical agents through the mean squared displacement. From the results, it was found that the binding of tetraethylene glycol increases the concentration of water around the nanotube as well as the stability of the loaded drug. However, the presence of tetraethylene glycol Led to a decrease in the diffusion coefficient of the nanocarrier.

A nanosystem containing a quantum dot within an optical cavity is a platform for the study of important quantum phenomena such as photon antibunching, entanglement, single photon generation, and quantum information. The use of such a system in these technologies depends on achieving a strong coupling mode between the quantum dot and the optical cavity. In this study, using a quantum optical approach, the energy Eigen values of a system including a quantum dot within an optical cavity were calculated. Then, for different quantum dots and optical cavities, the threshold conditions were studied to achieve strong coupling mode. The results showed that with increasing the coupling constant, the energy levels splitting increases and the threshold conditions are more favorable for achieving strong coupling mode. The energy level splitting threshold for the quantum dot with a decay rate of 2 μeV within optical cavities with a decay rate of 45 to 205 μeV occurred at a coupling constant of 10.75 to 50.75 μeV. In fact, it was observed that in order to achieve a strong coupling mode in such systems, it is necessary to go to the engineering of cavities with lower decay rates because the change in quantum dots does not have a significant effect on achieving this goal. Also, in a system with such a quantum dot, which has a coupling constant of 35 μeV within an optical cavity with energies of 20 to 140 μeV, the quality factor is in the range of 4930 to 5060.

Amyloid aggregations are the major biomarkers of various chronic diseases. Currently, one of the most common tests for in-vitro quantification of amyloid fibrillation kinetics is Thioflavin T assay, which is based on the flurescence emission of Thioflavin T. Inspite of its helpfulness, still has some drawbacks, and hence, introducing other tests to confirm its results is indispensible. Herein, we used Z-scan method to find the nonlinear refractive indices of silver nano particles at various concentrations. According to the results, silver nano particles altered the order of the aggregations from 10-10 to 10-9 such way that the magnitude of the nonlinear refractive indices and the florescence intensities increased and decreased, respectively with increment in the concentrations. Having the maximum diminution in the fluorescence intensity and the and the largest magnitude of nonlinear refractive index, 0.24 μg/ml was recorded as the optimal concentration. Therefore, the results of Thioflavin T and Z-scan, aligned perfectly with each other in a way that the more the concentrations of the silver nano particles were, the more the magnitude of the nonlinear refractive indices, and the more decrement in the fluorescence intensities, and thus, silver nano particles can wipe out the aggregations, which is quantitatively measurable.

The present paper is performed using the density functional theory at the quantum level of B3LYP / 6-311 + G (d, p) to determine the reactivity properties of phenylzine adsorption as an antidepressant on C60 (ih) as a drug carrier in the gas phase. Chemical properties (dipole moment), thermodynamic properties (Gibbs free energy, enthalpy, entropy and heat capacity) and electronic parameters (σ, μ, ω, χ, and η) were calculated for this drug. Based on quantum calculations, phenylzine shows good stability and reactivity. Due to the chemical structure of phenylzine, three active sites have been found for the chemical bonding of phenylzine with fullerene, all of which show thermodynamic stability with respect to the positive frequency value and the negative bond energy.

The problem of water shortage due to very low rainfall and its improper distribution has caused economic and agricultural problems. In this regard, the usual sources of water supply, such as water wells, have suffered irreparable economic and social consequences due to over-harvesting. One of the solutions available in recent decades is the use of available resources in water harvesting such as the water harvesting in the air. In this research, we have investigated the issue of water supply from air humidity by polymer layers with titanium dioxide nanoparticles. For this purpose, the effect of different concentrations of titanium dioxide nanoparticles on the rate of water harvesting by the desired layers at 90% humidity and at the temperature 15 and 5 ° C was investigated. Also, the amount of water collected was measured in terms of hours for 5 hours and according to the characteristics of the layers were analyzed. The results showed that the prepared layers have the ability to absorb air moisture and convert it into available water droplets due to the presence of TiO2nanoparticles in the layers. Although the efficiency of the layers is higher at low temperatures due to the faster condensation of water vapor, the results show that temperature changes have a significant effect on dew harvesting of water by layers with different percentages of TiO2nanoparticles, as the layers containing higher and lower concentrations of TiO2 nanoparticles have the highest power dew harvesting of water at temperatures of 5 and 15 ° C, respectively.

In this paper, a new structure of the SiC metal-semiconductor field effect transistor (SiC-MESFET) is presented. In the proposed structure of the upper part of the channel under the gate, a semiconductor with very low impurity density is used and at the bottom of the channel, a semiconductor with a high impurity density is used. The most important electrical characteristics of the proposed transistor such as breakdown voltage, drain current, threshold voltage, electric field and gate capacitor are simulated and compared with these characteristics in conventional transistor. According to the simulation results, the proposed structure reduces the maximum electric field in the channel and thus increases the breakdown voltage from 127 V to 136.5 V compared to the conventional structure. The new structure also increases the saturation drain current by 30% compared to the conventional structure. The high density of impurities in the channel bottom causes a negative shift in the threshold voltage in the provided transistor. According to the obtained results and increasing the drain current and the breakdown voltage, the proposed transistor can be used in high power applications.

The safety and standard rules of industrial, medical, and research centers have restricted using heat sources for sensing the flammable and toxic gases because of the reduction of the probable risks. Accordingly, in this work, ZnO nanoparticles were synthesized by the hydrothermal method. The resistive gas sensors were fabricated based on the as-prepared ZnO nanoparticles to detect ethanol gas. The results obtained indicated that the performance of the sensors was significantly improved for sensing ethanol. Sensitivity of 40 and 113% to 800 ppm ethanol was obtained under UV irradiation at room temperature and 80 ° C, respectively. The other features of this sensor include short response time, selectivity, and stability, linear calibration curve. Therefore, this sensor could be applied in environments where operating sensors at high temperatures have many challenges due to potential risks.

The present study is an applied-developmental study that investigates the increase in efficiency and improvement of the properties of single-walled boron nitride nanotubes (6,6) as nanocarriers for dacarbazine. In this research, the loading of dacarbazine on boron nitride nanotube (6,6) was investigated theoretically and the electron delocalization effects, electrostatic interaction, steric repulsion effects on the structural, electronic properties, and reactivity of dacarbazine on the boron nitride nanotube substrate were studied using quantum mechanical calculations of DFT (Density Functional Theory) evaluated at the B3LYP/6-31G* level of theory. The molecular orbitals distribution was investigated to understand changes in the electronic structures, adsorption energies (Ead), and electrical conductivity during the adsorption process. Frequency calculations were performed to determine the thermodynamic functions and vibrational frequencies in the gas phase. NBO (Natural Bond Orbital analysis) analysis was used to calculate the electronic transition effects as well as electrostatic interactions and other properties of the studied systems. The role of structural parameters, electron transfers, donor-acceptor orbital energies, orbital populations, and NBO charges on the boron nitride nanotube in interaction with dacarbazine were discussed. To determine the electrical conductivity and chemical properties of boron nitride nanotubes reacting by dacarbazine, electron energies, the dipolar moment was calculated and investigated.

A In this study, to create superhydrophobic surfaces on titanium; surfaces with contact angles higher than 150 ° by achieving hierarchical roughness (micro-nanoscale roughness); the anodizing process has been used and the effect of changing the electrolyte concentration on the surface microstructure is investigated. In anodized samples, which obtained the low surface energy by applying stearic acid, a different wetting angle of 126 to 154 degrees was obtained by changing the concentration of ammonium fluoride from 0.01 to 1 M. The results of scanning electron microscopy showed that Pine cone-shaped structures had grown on the surface with micrometer-scale dimensions consisting of a nanoflake structure in the sample made at low concentrations of ammonium fluoride. The dimensions of these Pine cones decrease with increasing the concentration of ammonium fluoride to 0.5 M and the number of them increases per unit area. In addition, the nanoporous structure is obtained, which resulted in the superhydrophobicity in this sample. By further increasing the concentration of ammonium fluoride to 1 M, the Pine cones structure are vanished and the surface of the oxide layer resulting from anodizing is seen as a smooth and nanoporous surface, which has led to a wetting angle of

In this research, the effect of nitrogen ion implantation on the crystalline and surface structure of copper oxide thin film has been investigated. For this purpose, a thin film with a thickness of 150 nm was deposited on the silicon substrate by copper oxide sputtering method. Then, the nitrogen ion implantation was performed using an electrostatic accelerator with 50 keV energy for 3 seconds with a fluence of 2×1014 particles per square centimeter. The measured current in this experiment was obtained using a profile device and its fitting to a Gaussian function in the range of several milliamperes. From the results of XRD analyzes, it was observed that the number of peaks and the crystal structure have changed. The results of SEM analysis show that the surface structure is defected due to implantation and the measurement of AFM roughness parameters showed that the thin layer of copper oxide became more uniform after ion implantation and its roughness or stiffness is decreased. By measuring the energy gap of copper oxide, it was found that after ion implantation, its value increased from 2.26 eV to 2.34 eV, which can be tuned to make different types of sensors.

The aim of this study was to investigate the photocatalytic effect of magnetocite-copper(II) oxide core-shell nanocomposites on the rate of degradation of bisacodyl using 20 W light emitting diode lamp. For this purpose, the effect of parameters such as drug concentration, nanocomposite content, pH of the solution, the effect of stirring the solution and the effect of dissolved oxygen under photocatalytic process has been investigated. research findings showed the effective efficiency of core-shell magnetite-copper(II) oxide nanocomposite and 20 W light emitting diode lamp in photocatalytic degradation of bisacodyl drug in optimal parameters, ie bisacodyl concentration of 20 mg / L, amount of core-shell magnetite-copper(II) oxide nanocomposite 0/1 g and the pH of solution 7 and stirring speed 750 rpm in air atmosphere. In this study, the results obtained in the process of photocatalytic degradation of bisacodyl using nanocomposites of core-shell magnetite-copper oxide in the presence of 20 watt light emitting diode lamp, shows the effective efficiency of this analytical method.

In a perovskite solar cell, the photoactive layer is sandwiched between the electron and hole transfer layers (ETL and HTL). ETL and HTL play a very important role in photovoltaic performance. So far, record efficiency has been achieved using spiro-OMeTAD as HTL. But the high cost and complex synthesis process may limit its large-scale application. Inorganic semiconductors are a promising alternative due to their high mobility, stability, and the ability to synthesize and deposition by simple and inexpensive solution-based methods. In this study, a low-temperature carbon paste with Cu2ZnSnS4 (CZTS) nanomaterials were applied to transport and collect hole carriers. CuInS2 NPs were applied as the reference HTM. CZTS nanoparticles which are synthesized by heating-up method have a crystalline phase of wurtzite and a Zn-rich composition. The presence of the HTM layer at the perovskite/carbon interface has a significant effect on improving photovoltaic performance. The spin rate and number of HTM layers were investigated by spin-coating method. In the case of two-time deposition of nanomaterials, the maximum efficiencies of 12.61%, 13.38%, 10.74%, 11.40% were obtained for spin rates of 3000, 4000, 5000 and 6000 rpm, respectively. Increasing the number of HTM layers reduces the efficiency and current density. The spin rate of 4000 rpm and two-times deposition were obtained as optimal conditions. CIS-based device as a reference showed an efficiency of 15.5%. High performance compared to CZTS is affected by less defects and quality of perovskite surface coverage, which was confirmed by EIS, PL, VOC decay and AFM analyzes.