Whispering gallery modes in photoluminescence and Raman spectra of a spherical microcavity with CdTe quantum dots: anti-Stokes emission and interference effects

We have studied the photoluminescence and Raman spectra of a system consisting of a polystyrene latex microsphere coated by CdTe colloidal quantum dots. The cavity-induced enhancement of the Raman scattering allows the observation of Raman spectra from only a monolayer of CdTe quantum dots. Periodic structure with very narrow peaks in the photoluminescence spectra of a single microsphere was detected both in the Stokes and anti-Stokes spectral regions, arising from the coupling between the emission of quantum dots and spherical cavity modes

CdTe Quantum Dot/Dye Hybrid System as Photosensitizer for Photodynamic Therapy

We have studied the photodynamic properties of novel CdTe quantum dots—methylene blue hybrid photosensitizer. Absorption spectroscopy, photoluminescence spectroscopy, and fluorescence lifetime imaging of this system reveal efficient charge transfer between nanocrystals and the methylene blue dye. Near-infrared photoluminescence measurements provide evidence for an increased efficiency of singlet oxygen production by the methylene blue dye. In vitro studies on the growth of HepG2 and HeLa cancerous cells were also performed, they point toward an improvement in the cell kill efficiency for the methylene blue-semiconductor nanocrystals hybrid system

A preliminary factor analytic investigation into the first-order factor structure of the Fifteen Factor Plus (15FQ+) on a sample of Black South African managers

The original publication is available at http://www.sajip.co.zaMoyo, S. & Theron, C. 2011. A preliminary factor analytic investigation into the first-order factor structure of the Fifteen Factor Plus (15FQ+) on a sample of Black South African managers. SA Journal of Industrial Psychology, 37(1), 1-22, doi: 10.4102/sajip.v37i1.934.Orientation: The Fifteen Factor Questionnaire Plus (15FQ+) is a prominent personality questionnaire that organisations frequently use in personnel selection in South Africa. Research purpose: The primary objective of this study was to undertake a factor analytic investigation of the first-order factor structure of the 15FQ+. Motivation for the study: The construct validity of the 15FQ+, as a measure of personality, is necessary even though it is insufficient to justify its use in personnel selection. Research design, approach and method: The researchers evaluated the fit of the measurement model, which the structure and scoring key of the 15FQ+ implies, in a quantitative study that used an ex post facto correlation design through structural equation modelling. They conducted a secondary data analysis. They selected a sample of 241 Black South African managers from a large 15FQ+ database. Main findings: The researchers found good measurement model fit. The measurement model parameter estimates were worrying. The magnitude of the estimated model parameters suggests that the items generally do not reflect the latent personality dimensions the designers intended them to with a great degree of precision. The items are reasonably noisy measures of the latent variables they represent. Practical/managerial implications: Organisations should use the 15FQ+ carefully on Black South African managers until further local research evidence becomes available. Contribution/value-add: The study is a catalyst to trigger the necessary additional research we need to establish convincingly the psychometric credentials of the 15FQ+ as a valuable assessment tool in South Africa.Publisher's versio

Electrically Switchable Photonic Molecule Laser

We have studied the coherent intercavity coupling of the evanescent fields of the whispering gallery modes of two terahertz quantum-cascade lasers implemented as microdisk cavities. The electrically pumped single-mode operating microcavities allow to electrically control the coherent mode coupling for proximity distances of the cavities up to 30-40 \mu\m. The optical emission of the strongest coupled photonic molecule can be perfectly switched by the electrical modulation of only one of the coupled microdisks. The threshold characteristics of the strongest coupled photonic molecule demonstrates the linear dependence of the gain of a quantum-cascade laser on the applied electric field.Comment: 4 pages, 4 figure

Plasmonic Control of Radiative Properties of Semiconductor Quantum Dots Coupled to Plasmonic Ring Cavities

In recent years, a lot of effort has been made to achieve controlled delivery of target particles to the hotspots of plasmonic nanoantennas, in order to probe and/or exploit the extremely large field enhancements produced by such structures. While in many cases such high fields are advantageous, there are instances where they should be avoided. In this work, we consider the implications of using the standard nanoantenna geometries when colloidal quantum dots are employed as target entities. We show that in this case, and for various reasons, dimer antennas are not the optimum choice. Plasmonic ring cavities are a better option despite low field enhancements, as they allow collective coupling of many quantum dots in a reproducible and predictable manner. In cases where larger field enhancements are required, or for larger quantum dots, nonconcentric ring-disk cavities can be employed instead

Иммобилизация РАО в перовскитоподобную матрицу

Выпускная квалификационная работа с., рис., табл., источников, прил. Ключевые слова: перовскит, иммобилизация радиоактивных отходов, самораспространяющийся высокотемпературный синтез, матричные материалы Объектом исследования является иммобилизация радиоактивных отходов в матричный материал методом СВС на основе перовскита. Цель работы – получение химически устойчивой матрицы для иммобилизации актиноидной фракции радиоактивных отходов методом СВС В процессе выполнения магистерской диссертации отработана технология получения матричного материала методом СВС. В результате исследования были определены закономерности образования фаз состава матриц. Степень внедрения: организация технологического процесса иммобилизации актиноидной фракции радиоактивных отходов методом СВС Область применения: атFinal qualifying work with., Fig., Tab., Sources, adj. Keywords: perovskite, radioactive waste immobilization, self-propagating high-temperature synthesis, matrix materials The object of research is the immobilization of radioactive waste in the matrix material by the SHS-based perovskite. The purpose of work - to obtain a chemically stable matrix for the immobilization of actinide fraction of radioactive waste by SHS In carrying out the master's thesis the technology of producing the matrix material by SHS. The study of the formation of the composition of the matrix phase have been identified. Degree of implementation: the organization of the process of immobilization actinide fraction of radioactive waste by SHS Scope: the nuclear industry

Computer Modeling the Excitonic Reflection and Photoluminescence Spectra of GaN Epitaxial Layers

Photoluminescence (PL) and reflection excitonic spectra o f GaN single layer grown on sapphire substrate by MOVPE were modeled with aim to estimate a basie parameters o f free A- and B- excitons. The calculations were performed in the frame o f two-oscillator model for dielectric function e(E). Three layered model o f crystal was used for fitting o f reflection spectrum which was measured at T=80K. In this way the dead layer thickness d=6 nm, resonance energies Eа=3.4916 eV and Eв = 3.5008 eV as well as the broadening parameters Га = 5.27 meV and Гв = 7.14 meV of the free excitons were obtained. These parameters were used then for fitting of PL spectra in assumption o f the thermal equilibrium for excitons taking into account the self-absorption of resonance emission. The values of diffusion coefficients Dа =0.3 cm²/s, Dв = 0.1 cm²/s and exciton lifetimes Ƭa = 37 ps, Ƭв = 17 ps were estimated

Strong coupling effects in hybrid plexitonic systems

Trabajo presentado a la 3rd International Conference on Applications of Optics and Photonics, celebrado en Faro (Portugal) del 8 al 12 de mayo de 2017.We investigated the interactions between localized plasmons in gold nanorods and excitons in J-aggregates and were able to track an anticrossing behavior of the hybridized modes both in the extinction and in the photoluminescence spectra of this hybrid system. We identified the nonlinear optical behavior of this system by transient absorption spectroscopy. Finally using magnetic circular dichroism spectroscopy we showed that nonmagnetic organic molecules exhibit magneto-optical response due to binding to a plasmonic nanoparticles. In our experiments we also studied the effect of detuning as well as the effect of off- and on resonance excitation on the hybrid states.We acknowledge financial support from Project Fis2016.80174-P (PLASMOQUANTA) from MINECO (Ministerio de Economía y Competitividad). L.L.-M. acknowledges funding from the European Research Council (ERC Advanced Grant 267867, Plasmaquo). This study was supported by the Ministry of Education and Science of the Russian Federation, grant no. 14.Y26.31.0011.Peer Reviewe

Electron-phonon interaction effects in semiconductor quantum dots: a non-perturbative approach

Multiphonon processes in a model quantum dot (QD) containing two electronic states and several optical phonon modes are considered by taking into account both intra- and nterlevel terms. The Hamiltonian is exactly diagonalized, including a finite number of multiphonon processes large enough to guarantee that the result can be considered exact in the physically important energy region. The physical properties are studied by calculating the electronic Green’s function and the QD dielectric function. When both the intra- and interlevel interactions are included, the calculated spectra allow several previously published experimental results obtained for spherical and self-assembled QD’s, such as enhanced two-LO-phonon replica in absorption spectra and up-converted photoluminescence to be explained. An explicit calculation of the spectral line shape due to intralevel interaction with a continuum of acoustic phonons is presented, where the multiphonon processes also are shown to be important. It is pointed out that such an interaction, under certain conditions, can lead to relaxation in the otherwise stationary polaron system.Fundação para a Ciência e a Tecnologia (FCT