NANOSCALE
Year:2019 | Volume:6 | Issue:2 |Papers Count:12

The coal has been considered as a suitable carbon source in recent years because the specific nanostructures have been synthesized from carbon cyclic fragments in it. The Synthesis condition in the solid phase was studied for the first time and it can be shifted the path of pyrolysis and carbonization processes to carbon nanostructures synthesis. In this study, amorphous porous carbon nanotubes and nanorods are synthesized by using direct co-carbonization of bituminous coal in the presence of 7% by weight of catalyst at 800° C. The temperature and duration of carbonization are 800° C and 60 minutes, respectively. By using of Ferrocene as a catalyst, amorphous carbon nanotubes (inner diameter: 50-200nm and thickness: 1-2 nm) are synthesized, while the magnetite nanoparticles with a diameter of 50-70nm result in the formation of nanorods with an average outer diameter of 80 nm as same as the diameters of catalyst nanoparticles. The samples have been analyzed by Scanning and Transmission electron microscopy and X-ray diffraction. The results show that iron nanoparticles due to Ferrocene and magnetite nanoparticles at 800° C lead to the growth of carbon nanostructures.

Hydrogen evolution via water splitting was investigated over the nanostructured TiO2/clinoptilolite photocatalyst with the aim of exploring the natural zeolitic support potential on the photocomposite reactivity. To this aim, a clinoptilolite supported TiO2 photocatalyst with 30 wt% titania content was synthesized by the facile solid state dispersion (SSD) method. The samples were characterized by XRD, FESEM, EDX, BET, FTIR, PL and UV-vis techniques. The characterization results indicated that clinoptilolite utilization could not only reduce the recombination of electron– hole pairs but also promote the distribution of metallic particles and decrease the TiO2 particle agglomerations. The high photocatalytic activity, 134. 16 µ mol g-1-1 h, was obtained for the TiO2/clinoptilolite sample which was about 2 times more than that of bare TiO2. Furthermore, TiO2/clinoptilolite photocatalyst showed sufficient reusability, making it a good choice for photocatalytic water splitting applications.

In this paper [Si/SiO2] stacks and silicon nitride as substrate were used to design a one-dimensional photonic crystal for application in visible light filters. In normal mode, transmission spectrum a has a forbidden transmission region, but by inserting the TiO2 thin film as a defect layer between the stacks, a transmission gap with a width of a few nanometers was created in the forbidden band. In addition, with a simple innovation and with the help of a relatively symmetric structure we managed to create two gaps in the band of visible and infrared wavelengths. By simple calculations, the location of the two gaps by changing the layer thicknesses, can be quite engineered and adjusted. It should be noted that in some structures three adjustable gaps were created which can have a variety of applications. All calculations have been carried out based on a 2 × 2 transfer matrix method (TMM) using MATLAB software.

Nowdays, Organic solar cells (OSCs) have attracted great interest due to their low cost, light weight, and flexibility. However, their efficiencies still need to be improved for many practical applications. The most conventional electrode for OSCs is indium tin oxide (ITO) which does not present high flexibility and robust mechanical properties. Additionally, this material is not appropriate for mass production due to the limited indium reserves. Here, we have proposed nanohole array-based plasmonic silver electrodes in order to design ITO-free OSCs. Numerical simulations based on finite-difference time-domain (FDTD) method have been employed to minimize the reflectance of the OSC while increasing the photoactive layer absorption. The designed nanostructure is a great potential to realize large-area and flexible energy harvesting.

In this paper, the interaction of light with coupled metallic nanoparticles by different models are studied. To investigate nonlocal effects simple suggested model and hydrodynamic model are utilized. Metalic nanoparticles are simulated, by taking account nonlocal effects in a simple model. Therefore metal is replaced by a thin composite layer on the metal-dielectric interface. The simulation is done by finite element method. The extinction-cross section spectra of the desired structure comparison are calculated by a local, nonlocal and simple model. Nonlocal models have blue shift regarding local model, for desired structure the blue shift of the first peak in the extinction cross section spectra is 0. 19 eV. The extinction-cross section spectra of various separation distance of nanoparticles are shown. Furthermore, the influence of increasing nanoparticles radius on extinctioncross section is analyzed in details. The results reveal that by reducing nanoparticles radius or gap, surface plasmon peaks are increased, due to the stronger nonlocal response. In a smaller radius, the blue shift is significantly larger by the nonlocal model relative to the local model.

Self-assembly of silver nanoparticles on functionalized glasses via APTES was used to fabricate SERS substrates. For this purpose, silver nanoparticles were synthesized by the wet chemical method and the size distribution of 35 nm was determined, using dynamic light scattering (DLS). UV-Vis spectroscopy was used to characterize the optical properties of the colloidal nanoparticles and also the prepared substrate. After the selfassembly of nanoparticles, the results indicate a slight red shift in the surface plasmon resonance (SPR) peaks. The SEM images showed a uniform distribution of silver nanoparticles on the surface of the glass. Rhodamine B (RB) dye was used as the analyte for studying substrate performances in SERS. However, no significant signals were observed in the Raman spectra of powder and solutions of the RB molecule due to a fluorescence background but using the prepared substrate and its fluorescence quenching effect, the Raman modes were clearly detected in a 10-5 M solution. By decreasing the concentration of the solution to 10-6 M, the Raman peak intensities were greatly reduced in a way that only some of them were detected.

n this study, the kinetics of nanocrystallization of amorphous Finemet alloys is investigated under nonisothermal condition. In order to estimate kinetic parameters, differential scanning calorimetric analyses of the amorphous samples were performed at various heating rates. These results show that the crystallization of the α Fe phase starts at around 450 ̊ C. X-ray diffraction pattern samples confirm these results. According to the XRD results, the crystallite size of the sample annealed at 450 ̊ C and 550 ̊ C were 12 nm and 19 nm, respectively. The variable activation energy of crystallization was calculated, based on differential scanning calorimetric results and according to Vyazovkin advanced isoconversional method. Results show that, the activation energy is variable as a function of transformed fraction and increases from 290 to 390 kJ mol-1. Variation of activation energy confirms the complexity of the nanocrystallization process. Numerical reconstruction of the reaction model using experimental data showed that nanocrystallization mechanism could not be described with a single theoretical model. But it is closer to three dimensional phase boundary reaction mechanism. Rrounded and isotropic crystallites observed on the TEM images confirmed these results.

In this paper, the identification of methane (CH4) and carbon dioxide (CO2) and their separation from each other were studied using zinc oxide decorated on graphene sheets (ZnO-GS) nanostructure. In this set of calculations, adsorption mechanism, electron structures, density of energy states, charge transfer processes, and system electrical conductance were studied at room temperature for different configurations resulting from the adsorption of CH4 and CO2 on the ZnO-GS nanostructure. All calculations were done based on density functional theory (DFT) using DFTGGA and vdW-DF methods. The results indicated that the ZnO-GS nanostructure is useful in the identification and separation of CH4 and CO2 from each other. It can be used as a nanosensor for the identification of these gases. Further, the electrical conductance of ZnO-GS nanosensor at room temperature before and after the adsorption of CH4 and CO2 was investigated. The results revealed that at room temperature, the sensor’ s electrical conductance increases following the adsorption of these gases, which can be used as an index for CH4 and CO2 identification. Another result obtained from the calculations is the significant difference between the adsorption energy of CH4 and CO2 gases on the ZnO-GS nanostructure, having the potential to change this nanosensor into a suitable option for the separation of methane and carbon dioxide from each other. The results obtained from this study are in congruence with the results of experimental and theoretical studies in literature.

In this research, the blood as a fluid is assumed to be by considering Newtonian and non Newtonian with different particle concentration in a three-dimensional rectangular microchannel rotating in a chamber around a vertical axis at a constant angular velocity. Affected by direct current, numerical investigation. Numerical results on the number of different nanoparticles in Newtonian and non-Newtonian fluids were extracted and it was observed that increasing the number of particles indicates an increase in fluid velocity in different directions. With increasing volume fraction, the pressure increases along the channel. Also, numerical investigation of particle velocity and particle distribution has shown that velocity changes in non-Newtonian fluids are much less than in Newtonian fluids. In fact, the flow of non-Newtonian fluids requires a stronger electrical field.

In this research, the effect of nanostructure size and shape on the Curie temperature of gadolinium (Gd) nanostructures with spherical, nanorod and thin film is simulated based on the Monte Carlo algorithm using Vampire software. The Curie temperature of spherical Gd nanoparticles decreases from 289 K to 245 K by reducing the diameter size of Gd nanoparticle from 10 nm to 1 nm. It was observed that the curvature temperature of gadolinium nanorods increases with increasing nanorod diameter at a constant dimensional ratio as well as with constant length. In addition, the Curie temperature increases by increasing the thickness of Gd thin film. Finally, the simulation data are extracted from the equations presented by other researchers in the equation.

Methotrexate (MTX) as a chemotherapeutic agent has the potential to be used in the treatment of brain tumors, but it is less used due to insufficient penetration into the brain parenchyma. By designing nanotechnologybased systems, it can be possible to overcome these limitations. In this study, the sonication method was used to prepare MTX loaded human serum albumin (HSA) nanoparticles. The results indicated that MTX loaded HSA nanoparticles have the size less than 100 nm. The obtained values for drug loading and encapsulation efficacy were 3% and 47%, respectively; and the results of thermal analysis of nanoparticles demonstated the amorphous form of MTX in HSA. In the release profile, slow and controlled release of nanoparticles was also observed in the neutral environment. In addition, the results indicated the decreased cytotoxic effects of MTX loaded HSA nanoparticles in comparison with free MTX. Therefore, the proposed formulation can have high potential in drug delivery systems to glioblastoma cells.

In this study, new optical leaky wave antennas are proposed to form light in an arbitrary manner for operation at the standard optical telecommunication wavelength of 1550 nm. The proposed antennas are designed based on hybrid plasmonic structures in which pattern synthesis is provided by modulation of the thickness of the silicon layer. The modulation of thickness changes the light velocity in the structure leading to different leakage rates through the antenna. Comparing the structure proposed in this paper with previously reported optical leaky wave antennas, the proposed design has the potential for integration with other devices and also provides any desired radiation pattern in wide bandwidth of operation. The proposed antennas can have applications in Light Detection and Ranging System (LIDARS), optical wireless communication, and solar cell efficiency improvement.