Rashba effect may play an important role in the nonlinear optical properties of heterojunction quantum dots. In this work, we have theoretically examined the effects of Rashba spin-orbit interaction on an electron in a cylindrical core/shell quantum dot (CCSQD). The modifications of various properties of cylindrical core/shell quantum dot such as transition energies, dipole transition matrix elements and linear and nonlinear optical properties due to change in Rashba coupling parameter, magnetic field and effective Rydberg energy were studied. We solved the Schrödinger equation using numerical methods and obtained energy eigenvalues as functions of the aforementioned parameters. It was observed that, the magnetic field has a considerable effect on absorption coefficients and refractive index. It was also observed that increasing the magnetic field shifts the resonances towards higher energies. Additionally, increasing in the Rashba coupling coefficient ( α R ) was found out to result an increase in absorption coefficients and refractive index. Our results demonstrated that, we can manipulate optical properties of cylindrical core/shell quantum dot using an external magnetic field.

Glioblastoma multiforme (GBM) is the most common and malignant form of astrocytoma with a median survival time of 1-2 years after diagnosis. The major treatment hurdle is the limited delivery of drugs to the brain due to the insurmountable blood brain barrier (BBB). Literature review reveals that nanoparticulate delivery system, in particular, magnetic polymeric nanoparticles in the presence of an external magnetic field may have enhanced permeation across the BBB. Therefore, the objective of this study was to fabricate the core of the polymeric nanoparticles with magnetic property. This core was fabricated by a modified seed synthesis method using tris(acetylacetonate) iron (III) [Fe(acac)3] as a precursor. To prevent the oxidation of Fe(acac)3, an overcoating with oleic acid was performed. The resulting oleic acid magnetic nanoparticle (OAMNP) was successfully prepared with a yield of 187.5 +/- 4.2 mg. The particle size of the core was 9 +/- 0.3 nm with a polydispersity index (PDI) of 0.189 +/- 0.001. OAMNP was dispersed within the polymeric matrix comprising of poly(lactic acid)-methoxy poly(ethylene oxide) (PLA-PEG) and poly(lactic-co-glycolic acid) (PLGA) (PEG PLGA) by single emulsion solvent evaporation technique. The resulting nanoparticle had a particle size of 201 +/- 2.1 nm with a PDI of 0.197 +/- 0.003. The presence of co-polymer block linkage on the surface of OAMNP was qualitatively confirmed by proton NMR and FT-IR analysis. The mean entrapment efficiency of OAMNP within the PEG PLGA matrix was 43%. The iron concentration was 60 +/- 3.1 mu g/ml which was below is cytotoxic concentration, and in line with published literature. Furthermore, in the presence of an external magnetic field superior efficacy of OAMNP PEG PLGA NPS in U-138 cells was observed.

In this work, the influence of biaxial strain on electronic, optical, and effective masses characteristics of Janus MSSe (M = Mo, W) have been investigated through first-principles calculations as implemented in WIEN2k package. From the obtained results, we remark that MoSSe and WSSe monolayers exhibit, respectively, a direct and indirect bandgap transition at equilibrium. Our achieved results demonstrate that the biaxial strain fundamentally alters the electronic states of Janus MSSe monolayers, and mainly, a semiconductor-metal transition phase has been determined to occur at a biaxial strain ratio of 12%. Moreover, it has been revealed that both electrons and holes effective masses of MSSe monolayers can be tuned by biaxial strain. For the optical properties of Janus monolayers, the polarization direction of the incident light plays a vital role in defining the light absorption domain. The MSSe Janus monolayers are shown to have a wide range of absorption spectrum, including the visible light domain with perpendicular polarized light. Furthermore, our computations of the dielectric function indicate that the optical responses of Janus monolayers MoSSe and WSSe strongly depend on the applied strain ratio; particularly, for the high photon energy domain. Overall, the findings revealed that both Janus MoSSe and WSSe monolayers could be potential materials for applications in optoelectronics.

In this paper, we report a recent theoretical study of the calculation of the binding energy and photoionization cross section of a single dopant in a spherical hollow or core/shell quantum dot taking into account the interaction of the electron with longitudinal optical phonons. Using Frolich approach and Lee-low Pines transformation, we determine the impact of different parameters such as shell thickness and dopant position on the energy and optical response of a bound polaron for two types of ionic II–VI semiconductors CdTe and ZnSe with different phonon coupling constants. Regardless of the material used, the electron–phonon interaction visibly reduces binding energy. For photoionization cross section, a redshift of resonance peaks was found when the effect of phonons is taken into consideration or when the donor is moved away from the shell center. These calculations provide us insights when choosing between materials for optoelectronic applications.

In this work, we investigated the influence of the geometrical confinement effects on the fundamental thermal properties of rutile and anatase TiO2 for both cylindrical nanostructures (CNSs) and nanotubular structures (NTSs), respectively. Calculations of energy levels are developed in the framework of effective mass approximation by generalizing the resolution of Schrödinger equation in a truncated cylinder. The energy spectrum is then used in the determination of thermodynamic properties by using the Boltzmann-Gibbs distribution. Numerical computations done for both rutile and anatase TiO2 nanomaterials reveal a strong localization of the electron orbitals along to the lateral surface for all the studied are CNS and NTS. The average energy, heat capacity, entropy, and Helmholtz free energy calculated for different thicknesses for NTS and different cross-sections of CNS. Our numerical investigation shows that all thermodynamic properties depend on the temperature, the cross-section for the CNS, and the shell thickness for the NTS. We demonstrated that for low thickness, the heat capacity shows a Schottky-like anomaly at low temperatures. We also show that the Rutile structure is more stable than anatase. We hope that the thermodynamic properties concluded from this study can be considered as useful information for understanding the thermodynamic properties of TiO2 nanofibers.

This work is based on a recent theoretical study of how the hydrostatic pressure and core/shell sizes affect the optical properties associated with the transition from the ground state to first excited state (1s–1p), of an exciton confined in spherical core/shell quantum dots (SCSQDs). We have computed under an effective mass framework, linear, third-order nonlinear, and total absorption coefficients (AC) and refractive index (RI) as functions of photon energy for different sizes of SCSQDs with varying hydrostatic pressure. Our results show that the optical absorption is deeply dependent on the incident light intensity. Both AC and RI significantly influenced by the confinement and pressure effects.

Monoclinic VO_2 is a known polymorph of vanadium dioxide that has received much attention due to its oxidative capabilities, geometric configuration, and promising applications in functional windows. VO_2 can usually be obtained through a hydrothermal method under high pressure. In this work we report a synthesis of VO_2 doped with Manganese using a rapid single-step hydrothermal process with V_2O_5, manganese (II) acetate and citric acid as precursors. Different syntheses were carried out in which the concentration of V_2O_5 and citric acid remained constant whereas the concentration of manganese (II) acetate was varied. The reactants underwent a stirring phase for 30 minutes before being loaded into a hydrothermal reactor for 2.5 hours at 200°C. The resultant was washed three times to remove the residual precursors. Imaging and spectroscopy characterizations such as TEM, SEM and UV-VIS-NIR have been performed on different doping concentration and the results display a dependence on doping concentrations.

In this paper, we report a study of the effect of a lateral electric field on a quantum confined exciton in a thin PbS quantum disk. Our approach was performed in the framework of the effective mass theory and adiabatic approximation. The ground state energy and the stark shift were determined by using a variational method with an adequate trial wavefunction, by investigating a 2D oscillator strength under simultaneous consideration of the geometrical confinement and the electric field strength. Our results showed a strong dependence of the exciton binding and the Stark shift on the disk dimensions in both axial and longitudinal directions. On the other hand, our results also showed that the Stark shift's dependence on the electric field is not purely quadratic but the linear contribution is also important and cannot be neglected, especially when the confinement gets weaker.

We have studied the effect of hydrostatic pressure on the confined exciton in a spherical core-shell quantum dot. Using a simple variational approach under the framework of effective mass approximation, we have computed the excitonic binding energy as a function of the shell thickness under the applied hydrostatic pressure. Our results show that the ground state binding energy of exciton depends greatly on the shell thickness, which tends to the two-dimensional limit of 4R(X), when the ratio a/b tends to unity. The numerical calculations also suggest that the applied hydrostatic pressure favors the attraction between electrons and holes so the excitonic binding energy increases when pressure increases.

Magnetic and fluorescent nanoparticles are widely studied in biomedical research such as drug delivery, imaging, etc. Hybrid nanoparticles combining both magnetic and fluorescent properties are particularly interesting. In this manuscript, we report a recent study on Fe3O4-Au hybrid nanoparticles displaying fluorescence. Fe3O4-Au hybrid nanoparticles were synthesized via solution phase chemical reaction in inert N-2 atmosphere. The synthesized hybrid nanoparticles were characterized by UV-Vis-NIR spectroscopy and fluorescence spectroscopy, XRD, TEM, etc. The optimal synthesis condition yields stable, uniform hybrid nanoparticles without impurities. The correlation between fluorescent life-time and sizes, compositions, shapes of hybrid nanoparticles was discussed. Biomedical applications of synthesized hybrid nanoparticles, utilizing their fluorescent and magnetic properties, are still undergoing.

This paper reports a recent study on the polarizability and the photoionization cross section (PCS) of a hydrogenic impurity confined in a spherical AlAs/GaAs core/shell quantum dot under external electric field and hydrostatic pressure. In the framework of effective mass theory, a variational approach is used to determine the polarizability, binding energy, and the PCS of a single donor in a spherical core/shell quantum dot. Our numerical calculations reveal that all these fundamental parameters are deeply dependent on the core and shell radii. The study of the localization of the impurity inside the core/shell indicates that the Stark shift is more important when the impurity is positioned at the center of the core/shell and becomes less important when the donor moves toward the boundaries of the shell layer. In addition, a rapid decrease of the intensity of electric polarizability under hydrostatic pressure is observed. In order to understand the optical responses during the photoionization of the donor dopant, we investigated the PCS under hydrostatic pressure, electric field, ionized donor position, and core/shell sizes.

In this paper, we report a first hand study of plasmon-enhanced photocurrent observed in hybrid nanostructures based heterojunction solar cell. The heterojunction solar cell was fabricated, using chemically synthesized narrow gap, IV–VI group semiconductor nanoparticles (PbS) of 3~6nm diameter, wide gap semiconductor ZnO nanowires of 500nm~1 μm length and ~50nm diameter, and gold nanoparticles (~5nm to 30nm), by spin-coating (~20cycles) onto FTO glasses, in ambient conditions (25°C, 1atm). The synthesized nanostructures were characterized by XRD, UV-VIS absorption, SEM, TEM, solar simulator, etc. Nanostructures of variant sizes were integrated in to the heterojunction devices to study the effects on photocurrent and solar cell performance. The sizes, lengths, thickness of nanostructures were optimized to have best solar cell devices. The effects of fabrication conditions (such as growth temperature, growth time, anneal temperature, ligand treatments, in air or in N2, etc.) on device performance were also studied. The architecture of film stack, i.e., the positions of Au nanoparticles and PbS nanoparticles were also studied. It was confirmed that introducing Au nanopartiles with proper size would lead to the increase of photocurrent. The key challenges were to minimize the trap states and optimize the interface of nanostructures.

PbS nanoparticles (NPs) were synthesized by the hot-injection solution-phase method using sulfur powder as precursor. Pb-precursor (446 mg PbO) was dissolved with 1.5 ml oleic acid in 15 ml 1-octadecene (ODE) solvent inside a four-neck flask under N 2 atmosphere and nucleated at 120 °C for half an hour. S-precursor (S powder), dissolved in a mixture of 3 ml ODE and 1 ml Oleylamine, was then injected swiftly by a syringe into the flask with well-dissolved Pb-precursor. The growth time varied from 10 minutes to a few hours and growth temperature was maintained at from 90 to 120 °C after injection, which would result in nanoparticles of different sizes from 5 to 10 nm. The synthesized PbS NPs were characterized by TEM, XRD, and UV-Vis-NIR spectrometer. The morphology as well as absorption spectra were found to be highly sensitive to the synthesis conditions. The XRD spectra showed that the structures were less sensitive to synthesis conditions.

In this paper, we report a first hand study of enhanced photocurrent observed in nanostructure-based bulk heterojunction solar cell due to introduction of Au nanoparticles. The bulk heterojunction solar cell was fabricated using chemically synthesized narrow gap, IV–VI group semiconductor nanoparticles (PbS, ~3 nm), wide gap semiconductor ZnO nanowires (~1 μm length, ~50 nm diameter), and gold nanoparticles (~20 nm), by spin-coating method in N2-filled glove box. We have demonstrated that such a bulk heterojunction solar cell can be incorporated with metal nanoparticles (Au) to enhance solar device performance. Three types of solar cell devices were studied. An enhancement in the photocurrent due to introduction of Au nanoparticles was observed, compared to solar cell device without Au nanoparticles. The power conversion efficiency was also increased, possibly due to the plasmonic effects from Au nanoparticles. The fabrication procedures can be readily extended to other nanomaterial systems. Further optimization in the fabrication would be needed to realize high-efficient, stable solar cell devices.

The microstructure and magnetic properties of Fe3Se4 nanowire (NW) arrays in anodic aluminum oxide (AAO) porous membrane are studied. Cross-sectional SEM and plane-view TEM images show that the mean wire diameter (dw) and the center-to-center spacing (D) of Fe3Se4 nanowires are about 220 nm and 330 nm, respectively. The field-cooled magnetization dependent on the temperature indicates a Curie temperature around 334 K for the Fe3Se4 nanowires. The coercivities of Fe3Se4 nanowires at 10 K, obtained from the in-plane and out-of-plane hysteresis loops, are as high as 22.4 kOe and 23.3 kOe, which can be understood from the magnetocrystalline anisotropy and the magnetization reversal process.