فصلنامه نانو مقیاس
سال دهم شماره 3 (پیاپی 39، پاییز 1402)

The presence of different concentrations of dopamine can be a reason for the health or unhealthiness of some parts of the body. In this research, a sensor is made based on the plasmon theme phenomenon in one-dimensional photonic crystal. For this purpose, one-dimensional photonic crystal was fabricated by electron gun method and the sample was exposed to different concentrations of dopamine with the help of microfluidic channel. The results of measuring the theme mode displacement in the sample with different polarizations and dopamine concentrations show a sensitivity of 16.96 nm per concentration.

Graphene oxide functionalized by pyrimidinium hydrogen sulfate (GO@Pyrim.H-HSO4) is an efficient and environmentally benign catalyst for the synthesis of bis-coumarins. At first, graphene oxide was prepared according to a modified Hummers method from the oxidation of graphite using violent oxidants such as concentrated sulfuric acid, sodium nitrate, potassium permanganate, and Hydrogen peroxide. It was subsequently modified by 2-aminopyrimidine through amide formation and then treated with sulfuric acid to reach the catalyst as pyrimidinium hydrogen sulfate (GO@Pyrim.H-HSO4). The catalyst was characterized by X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDS), field emission scanning electron microscopy (FESEM), thermogravimetric analysis (TGA), and FTIR spectroscopy. The synthesis of bis-coumarins was implemented through a one-pot process using no solvent by the reaction of 4-hydroxycoumarin and functionalized benzaldehydes. The scope and limitations of the procedure were examined using aromatic aldehydes with various functional groups. The functional groups had no significant effect on the product yields. The catalyst exhibited efficient properties such as simple work-up, no byproducts, sustainability, nonmetal and safe components, stability under reaction conditions, and recoverability. The synthetic route shows significant properties including sustainable, simple work-up, solvent-free condition, short reaction times, and no by-product.

In the present work, ZnCo2O4 nanostructures were successfully synthesized using hydrothermal method. In order to investigate the morphology of the nanostructures on their gas sensing performance, we used three different concentrations of urea (5, 10, 15 mmol) in growth process which caused three different morphologies of ZnCo2O4. The structure and morphology of the products were respectively analyzed by XRD and SEM. To study the gas sensing parameters, the nanostructures were dispersed in ethanol and then settled on a gold coated glass electrode. The results showed that the sensor including ZnCo2O4 nanostructure grown under 5 mmol urea has 9.5 response, 25 seconds response time, and 49 seconds recovery time for 100 ppm acetone gas at 240 oC work temperature. In addition, we observed that this sensor has a good selectivity for acetone gas in compare to ethanol, methanol, benzene, and toluene gases. The high response of ZnCo2O4 flower shaped microrod grown under 5 mmol urea could be related to its large specific area and rod morphology.

In this paper, we study the properties of electronic transport in MXene Zr2CO2 nanoribbons of armchair type (AMNR). By using the tight-binding method, we obtain the band structure of this material and investigate the electron conductance with the non-equilibrium Green's function approach. It can be seen that increasing the width of the ribbon from 5-AMNR to 20-AMNR reduces the energy gap from 1.77 eV to 1.40 eV and also increases the maximum conductance from 7 e^2⁄(h )to 18 e^2⁄(h ). Increasing the width of the ribbon to 55-AMNR will eventually lead to the reduction of the energy gap to a limit value of 1.39 eV. For a nanoribbon with a certain width of 5-AMNR, we consider carbon and zirconium vacancies in three central, edge, and linear positions and show that the vacancy can reduce the energy gap up to 1.62 eV and eliminate the step mode of conductivity. Also, in the presence of vacancy, we see a decrease in the maximum conductance, and in some cases, this decrease reaches from 7 e^2⁄(h ) (in the case without vacancy) to less than 3 e^2⁄(h ). The results of this paper indicate the ability to adjust the band gap by changing the width of the ribbon and also control the conductance by applying the vacancy. These properties show the potential applications of this kind of MXene in nanoelectronic devices.

Magnetic field sensors based on magneto-electric structures have various applications in industries such as biosensors. Through simulation using the finite element method (FEM), sensors with appropriate main frequency and sensitivity can be designed, paving the way for the fabrication of bio-magnetic sensors. In this article, we utilized magneto-electric structures based on patterned Galfenol alloy nanostructures as the magnetostrictive layer and aluminum nitride as the piezoelectric layer. The designed cantilever-type structure has a magnetoelectric coefficient of 5850 V/cm.Oe at the resonance frequency of 3051.9 Hz and is capable of measuring magnetic fields in the range of one Pico tesla.

In this study, SiO2, CeO2/SiO2, ZnO/SiO2, and ZnO/CeO2/SiO2 nanostructures were synthesized by sol-gel method in two ways using TEOS, cerium nitrate, and zinc nitrate as precursors. In the first method, salts were added at the end, but in the second method, TEOS was added at the end. With the difference in the order of adding materials, the distribution of materials in the composites and the size of the particles changed significantly. The best conditions in terms of material composition and particle size were for the ZnO/CeO2/SiO2 nanocomposite synthesized by the second method. EDS, FT-IR, FESEM, BET, and XRD analyzes were performed for the samples to confirm the formation of the expected nanostructure. Finally, the ZnO/CeO2/SiO2 nanocomposite synthesized by the second method was evaluated to determine the electrochemical hydrogen storage capacity. With the chronopotentiometric method, its hydrogen storage capacity was recorded as 708.75 mAh/g, which is a significant amount compared to the reported capacities. The comparison of this number with the storage capacity of silica and ceria nanostructures also shows the constructive effect of these materials on each other. According to the results, the second synthesis method is a more suitable method for making these nanomaterials for electrochemical hydrogen storage.