نشریه پژوهش های نوین فیزیک
سال هفتم شماره 2 (پیاپی 15، پاییز و زمستان 1402)

Surface plasmon resonance (SPR) biosensors have wide applications in the detection and analysis of biomolecules and biochemicals. Here, an SPR biosensor using 2D dichalcogenide WS2 material deposited on Ag and Ni metal layers was presented to detect ambient analyte concentration. This SPR biosensor works based on the principle of total reflection reduction. The thickness of the silver and nickel metal layers are considered to be 31 nm and 4 nm, respectively, and the thickness of the two-dimensional material WS2 can be changed and varies between 1 and 2 layers. By using a WS2 layer, the sensor sensitivity was obtained as high as 400.28 degrees per refractive index unit (RIU) and also for this sample, the performance index FOM=61.87 (/RIU) was obtained. Also, the refractive index of the sensor medium ranges from 1.33 to 1.335.

In this paper, we have used the time-of-flight method of a charge packet, which has been calculated by a voltage pulse of the driving speed and mobility of holes in organic semiconductors. This technique involves applying a voltage to the anode and calculating the time delay of the injection of charge carriers to the other electrode. This method is a simple method to check the properties of charge transport in organic semiconductors. In this section, under the influence of different voltages at room temperature, using the time-of-flight method, we have calculated the mobility of holes by applying the Scheer-Montreal model in organic semiconductors.Also, the effect of the electric field on the mobility at two voltages of 100 V and 50 V was investigated for the flight time arrangement and it was observed that the mobility of the cavity at 100 V is higher than other voltages. The mobility of the hole, which was checked at different voltages at room temperature, is the best and most appropriate mobility for the hole in organic semiconductors, which corresponds to the applied voltage of 40 V to the sample.

Treatment planning systems (TPSs) should be prepared to identify various tissues of body. This process requires a CT-ED curve as an input to TPS. In this process, a phantom with various inhomogeneities is scanned with CT and then the CT numbers of corresponding materials of the phantom are obtained. By knowing the electron density of these materials, The CT-ED curve can be entered into the TPS and the system can identify the material of different tissues and perform dose calculations based on the tissue type using this curve. The purpose of this study is to design and fabricate a phantom with 6 different inhomogeneities to be used in the process of commissioning TPSs.

The electron density phantom with code M062 made by CIRS company of America was chosen as the reference phantom. The body of the new phantom was designed using Solidworks software. A cylindrical phantom with height of 15cm and diameter of 20cm was designed by considering various inhomogeneities. The CT images were obtained from two phantoms under same conditions. After determining the CT numbers and the electron densities of the materials, the CT-ED curves were obtained and compared with each other using Excel software.

The results obtained from both phantoms were close to each other and subsequently the CT-ED curves of both phantoms had the same structure with great similarity to each other.

The fabricated phantom is equivalent to the reference phantom and has all three main parts: lung, soft tissue and bone and can be used in radiotherapy centers instead of the reference phantom for commissioning TPSs.

Nitrate compounds III-N with a wide band gap have an important role in the field of optoelectronics and electronic devices with high frequency and power. Gallium nitride (GaN) has emerged as one of the most important and widely used semiconducting material among them. In this article, the electron mobility in one dimensional nanoribbon gallium nitride in the presence of impurities has been investigated and we compare our results with electron mobility of two dimensional systems. The Boltzmann transport equation and relaxation time approximation with considering the ionized impurity potential are used in calculations. The influence of different relevant physical parameters such as width of nanoribbon strips, Fermi energy and impurity density on the mobility is examined. Finally the electron mobility as a function of Fermi energy, distance between impurity with carriers and width of nanoribbons for gallium nitride is plotted. As it is expected, numerical results show that the mobility of GaN nanoribbon for very large width move toward mobility in two dimensional electron gas.

Silicon nanowires have attracted the attention of many researchers in recent years due to their electrical and mechanical properties and also its potential applications in many fields such as biosensors. In this study, we theoretically investigated the phonon transport through silicon nanowires in the presence of isotope impurities. Heat transfer properties of silicon nanowires in the <100> direction were studied using the non-equilibrium Green’s function method and the impurity atoms were placed in the middle part of the structure. The results of this research showed that, in the presence of isotope impurity, thermal conductivity decreases. The effect of impurity atom mass was also investigated and the results of this study also indicated that with the increase in the mass of the impurity atom, the thermal conductivity decreases more and the reason for this should be investigated in the dependence of the phonon frequency on the mass.

Production of gaseous products through non-thermal plasma technology is an innovative method for refining heavy oil or petroleum residues. In this study, plasma sparks were generated in gas bubbles to break the hydrocarbon bonds in oil and produce valuable gaseous products. This research aims to develop a more efficient and sustainable method for refining heavy oil or distillation column residues using non-thermal plasma. This study describes the construction of a reactor designed at the Plasma Research Institute of Kharazmi University, the stages and circuitry for generating plasma sparks, the method of gas collection, and the analysis techniques for gaseous products. Heavy oil was poured into the reactor, and argon gas was used to purge the circuit of oxygen. Additionally, plasma sparks were generated in argon gas bubbles injected into the oil. The paper examines the utilization and optimization of gas usage in the process. The primary gaseous products obtained, forming the highest percentage of the gas mixture, were hexane (13.8%) , pentane (15.7%) , and 2-methylbutane (12.75%). After plasma application and gaseous product storage, the remaining heavy oil exhibited no significant changes in its state and remained suitable for its original uses.