Journal of Optoelectronical Nanostructures
Volume:9 Issue: 2, Spring 2024

Recent progress in high-technology equipment enables the fabrication of quantum dots such as GaAs, and GaAlAs confining a finite number of excitons and allowing for control of the properties of quantum dots. Biexciton quantum dots are the simplest example that can be used to upgrade optoelectronics technologies. This theoretical research investigates a model of the biexciton state in the strongly oblate ellipsoidal quantum dot with the relativistic corrections of mass and Hamiltonian in the framework of the quantum field theory due to the importance of the relativistic effect for this type of quantum dot shapes. The Sturmian function transformation and Wick ordering method to calculate the vacuum state energy eigenvalue of the biexciton system are utilized. Based on the relativistic behavior of interactions, the mass corrections to the Hamiltonian are defined. Dependence of the relativistic mass on the distances between electrons and the constituent mass to the coupling constant is obtained. The results show that as increasing quantum dot size, the relativistic mass and Hamiltonian corrections terms decrease.

In this paper the influence of different parameters such as active layer thickness, light intensity and charge separation distance on the photocurrent-voltage, short circuit current density (Jsc) and open circuit voltage (Voc) characteristics in MEH-PPV:PCBM BHJ devicesis studied. For this purpose, the numerical continuum modelbased on drift-diffusion approximation is used. The J-V characteristics of MEH-PPV:PCBM BHJ devices under illumination change considerably with varying the active layer thickness from 40nm to 280nm. In these devices, as the active layer thickness increases from 40 nm to 120 nm the short-circuit current density increases dramatically. The open circuit voltage (Voc) is partially affected by varying the active layer thickness. In these devices, as the light intensity increases, the current density would increase at low voltages. Also, as the charge separation distance “a” increases, The exciton dissociation rate (kdissnexc) and current density would decrease.

In this paper, the influence of host liquid’s properties on far-field intensity distribution of a continuous Gaussian laser beam passing through the synthesized colloidal gold nanoparticles (AuNPs) is experimentally and numerically studied considering the different form of heat transfer modes. Our results reveal that dispersed NPs in liquids with more viscosity or less thermal expansion coefficient, lead to more concentric far-field diffraction patterns. By changing the viscosity and thermal expansion coefficient, the form of diffraction patterns due to the convection effect, can dramatically change compared to the strength of the thermal nonlinear refraction. The effect of the linear absorption coefficient of the medium on diffraction patterns of the colloids is also investigated. It is shown that by increasing the linear absorption coefficient of the medium, the number of the rings and the beam divergence increase under exposure of the 532 nm laser beam. Our observations show the excellent sensitivity of the diffraction ring pattern technique to characterize the different modes of heat transfer and thermo-optical nonlinear properties of the NPs colloids.

This paper presents a new environmental, and remarkably efficient heterogeneous magnetic nanocomposite, NCP@POCl2-x (Fe3O4@SiO2@CS@POCl2-x), designed for the regioselective production of cyanide compounds from epoxides using NaCN, subsequently facilitating the synthesis of α,β-unsaturated carboxylic acids. The reactions were conducted under mild conditions, demonstrating the catalyst's remarkable performance with high yields. The presence of POCl2-x and the influence of water and heat facilitated the transformation of epoxides into cyanohydrin and α,β-unsaturated carboxylic acids. Remarkably, the reactions demonstrate excellent regioselectivity, producing clean and quantitative products. NCP@POCl2-x is a heterogeneous magnetic nanocatalyst with a strong magnetic core of Fe3O4 surrounded by chitosan as a green layer and functionalized by the POCl2-x group. This catalyst can be easily separated using external magnetic force. The combination of heterogeneity, magnetic properties, easy recovery, and exceptional performance establishes NCP@POCl2-x as a valuable tool for efficient and selective transformations of epoxides.

In this present paper, the linear optical absorption coefficient in an array of quantum wires under the external electric and magnetic fields is studied. The effects of the external fields and structural parameters such as wires' radius, the number of wires, the distance between wires, and the Al composition on the optical absorption are investigated. Results indicate that the resonant peak of the absorption coefficient shifts toward the lower photon energies with increasing structural parameters. Also, results reveal that the absorption frequency is in the terahertz range and shifts to the higher (lower) energies by increasing the electric (magnetic) field.  The resonant peak value of the linear optical absorption decreases by increasing the wires' radius, the distance between wires, and the Al composition. However, it changes non-monotonically with the number of wires.  Also, the optical absorption reduces with the increase of the electric field and changes non-monotonically with the magnetic field.

In this research, the interaction of electromagnetic fields and sizes on the energy levels and specific functions of a GaAs nanowire coated with, along with the spin-orbit effect, has been carefully investigated. The magnetic field is applied in the direction parallel to the axis of the wire and the electric field is applied both in the plane perpendicular to the axis of the wire and in the direction parallel to it. To investigate the effects of the spin-orbit effect, in most cases, from the explicit form of the wave functions resulting from the solution of the Schrödinger equation Use related to the problem. We have shown that spin-orbit coupling together with external fields have a significant effect on the electronic properties of the wire. Since external magnetic field amplifies the intrinsic magnetic field, thus energy splitting due to SOI is bigger at higher B values. Because of the stronger role of magnetic field and weak effects of radial electric field on the SOI this phenomenon is not sensible when electric filed is radial.