مجله فیزیک کاربردی
سال هشتم شماره 2 (پیاپی 15، پاییز و زمستان 1397)

In this article, the use of magnetic nanoparticles as transport agents in various biological programs is investigated and a magnetic process is analyzed in which magnetic carrier particles are guided to an object by an external magnetic field for drug delivery to the target. In addition, the paths of magnetic nanoparticles are simulated using the COMSOL software. In order to accumulate the drug at tumor sites and to prevent its undesirable side effects on healthy cells, the drug needs to be targeted merely to lesion sites. Therefore, nanoparticles are used for targeted drug delivery to the tumor cells. Among these, several factors influence the movement of nanoparticles. The direction of particles is affected by strength of the magnetic field, the shape of the magnet, the size and the magnetic properties of the nanoparticles. The external magnetic field can be generated in several ways, which in this research we have simulated a magnetic field generated by two special magnets.

In this study, chitosan nanoparticles were prepared by ionic gelation method. Three concentrations of 2 mg/ml, 4 mg/ml and 10 mg/ml were prepared to evaluate the effect of chitosan concentration on the size of chitosan nanoparticles. The results showed that with increasing chitosan concentration, the particle size of the chitosan nanoparticles becomes larger. In the best conditions, particles with average size of 90 nm was obtained. In order to evaluate the effect of chitosan solution pH change on the size of chitosan nanoparticles, the effect of two pHs, 5.0 and 8.4 on all three concentrations of chitosan solution was investigated. The results showed that with increasing chitosan solution pH, the particle size of the chitosan nanoparticles becomes smaller. In the best conditions, in pH equal to 8.4, particles with average size of 90 nm for concentration of 2 mg/ml, average size of 106 nm for concentration of 4 mg/ml, average size of 124 nm for concentration of 10 mg/ml were obtained. In these two examinations, scanning electron microscope images show the chitosan nanoparticle’s sticking and sponge. FTIR spectra were recorded for the specimens and the formation of nanoparticles proved to be due to the disappearance of a peak in the spectrum of crossing and the creation of two new peaks in the spectrum due to the ionic crosslinking between phosphoric ions and amine groups ions.

The structural and electronic properties of the hydrogenated zigzag GaN nanoribbons with different widths 19.2, 24.85, 30.49 and 36.14 Å corresponding to numbers of the zigzag chain, 3, 5, 7, 9, have been studied. Density functional theory with full potential augmented plane wave approach and the generalized gradient approximation (GGA) are used for exchange-correlation functional. The curves of total and partial density of states and electronic density of the nanoribbons were drawn. These computations show that all of the nanoribbons have semiconducting behavior. Values of energy gap of the nanoribbons are 2.687 eV, 2.304 eV, 2.107 eV and 2.008 eV for the ribbons with 3, 5, 7 and 9 width, respectively. With increasing the width of the nanoribbons, the band gap is decreased. Also, these nanoribbons do not have magnetic property. In addition, in narrower ribbon, the partial density of states shows that the edge atoms have more constitution than that of inner atoms in density of states.

In this paper, the electronic and band structure of GaAs in the zinc-blende phase are calculated making use of Full Potential Linear Augmented Plan Wave (FP-LAPW) method in the framework of density functional theory (DFT) by Wien2k software. The exchange and correlation potentials are calculated within the scheme of LDA, PBE and GGA approximations. The calculated band gap for GaAs with the best approximation PBE shows that there is a direct band gap at the Γ point, which is equal to 0.8eV; so, GaAs is semiconductor. The results show that the calculated electronic and structural properties of this composition, including lattice constant and compressibility derivative, are in good agreement with experimental and theoretical results obtained in others’ works.

Solar cells have different efficiencies in different weather conditions and environments. Changing the environmental conditions leads to the change in the environmental refractive index. The change in the refractive index affects the efficiency of the solar cell. In this paper, we investigate and model the effect of changing the refractive index of the environment on a silicon solar cell with thickness of 500nm and silver ribbon nano-plates of width 25nm and height 50nm. We study the effect of refractive indices from 1 to 1.6 on the performance of the solar cell. The simulation results show that the best efficiency and absorption of plasmonic solar cell with silver ribbon nano-plates with width 25nm, height 50nm, and period 50nm are obtained in a refractive index of 1.2. The solar cell efficiency and fill factor are respectively evaluated as 12.45% and 83%. Finally, the open circuit voltage and short current density are calculated as 0.21V and 6.91mA/cm2, respectively.

Density of manufactured specimens by powder metallurgy method is very important in determining their final quality and useful life. Existing cavities and porosity can cause changes in the density of the samples and reduce their strength. The Archimedean method is used to examine the samples’ density, in which some parts with specific dimensions of the samples are cut and their density is calculated by measuring their weight and volume. The use of non-destructive methods is preferable because of their non-destructive nature during density measurement. In this study, digital radiography testing (DRT) is proposed for this aim. The basis of DRT is X-ray attenuation in the material and it is a non-destructive test. By this technique, the density of different auto parts was evaluated by industrial digital radiography and was compared with the Archimedean method. The results show that this method has the sufficient accuracy and efficiency to measure the density of parts without damaging them. Also, using this method, the internal structure of the object and its defects can be examined.