Exciton spin dynamics and photoluminescence polarization of CdSe/CdS dot-in-rod nanocrystals in high magnetic fields

The exciton spin dynamics and polarization properties of the related emission are investigated in colloidal CdSe/CdS dot-in-rod (DiR) and spherical core/shell nanocrystal (NC) ensembles by magneto-optical photoluminescence (PL) spectroscopy in magnetic fields up to 15 T. It is shown that the degree of circular polarization (DCP) of the exciton emission induced by the magnetic field is affected by the NC geometry as well as the exciton fine structure and can provide information on nanorod orientation. A theory to describe the circular and linear polarization properties of the NC emission in magnetic field is developed. It takes into account phonon mediated coupling between the exciton fine structure states as well as the dielectric enhancement effect resulting from the anisotropic shell of DiR NCs. This theoretical approach is used to model the experimental results and allows us to explain most of the measured features. The spin dynamics of the dark excitons is investigated in magnetic fields by time-resolved photoluminescence. The results highlight the importance of confined acoustic phonons in the spin relaxation of dark excitons. The bare core surface as well as the core/shell interface give rise to an efficient spin relaxation channel, while the surface of core/shell NCs seems to play only a minor role.Comment: 18 pages, 15 figure

Surface spin magnetism controls the polarized exciton emission from CdSe nanoplatelets

The surface of nominally diamagnetic colloidal CdSe nanoplatelets can demonstrate paramagnetism owing to the uncompensated spins of dangling bonds (DBSs). We reveal that by optical spectroscopy in high magnetic fields up to 15 Tesla using the exciton spin as probe of the surface magnetism. The strongly nonlinear magnetic field dependence of the circular polarization of the exciton emission is determined by the DBS and exciton spin polarization as well as by the spin-dependent recombination of dark excitons. The sign of the exciton-DBS exchange interaction can be adjusted by the nanoplatelet growth conditions

CdSe/CdS dot-in-rods nanocrystals fast blinking dynamics

The blinking dynamics of colloidal core-shell CdSe/CdS dot-in-rods is studied in detail at the single particle level. Analyzing the autocorrelation function of the fluorescence intensity, we demonstrate that these nanoemitters are characterized by a short value of the mean duration of bright periods (ten to a few hundreds of microseconds). The comparison of the results obtained for samples with different geometries shows that not only the shell thickness is crucial but also the shape of the dot- in-rods. Increasing the shell aspect ratio results in shorter bright periods suggesting that surface traps impact the stability of the fluorescence intensity

Electron and hole g-factors and spin dynamics of negatively charged excitons in CdSe/CdS colloidal nanoplatelets with thick shells

We address spin properties and spin dynamics of carriers and charged excitons in CdSe/CdS colloidal nanoplatelets with thick shells. Magneto-optical studies are performed by time-resolved and polarization-resolved photoluminescence, spin-flip Raman scattering and picosecond pump-probe Faraday rotation in magnetic fields up to 30 T. We show that at low temperatures the nanoplatelets are negatively charged so that their photoluminescence is dominated by radiative recombination of negatively charged excitons (trions). Electron g-factor of 1.68 is measured and heavy-hole g-factor varying with increasing magnetic field from -0.4 to -0.7 is evaluated. Hole g-factors for two-dimensional structures are calculated for various hole confining potentials for cubic- and wurtzite lattice in CdSe core. These calculations are extended for various quantum dots and nanoplatelets based on II-VI semiconductors. We developed a magneto-optical technique for the quantitative evaluation of the nanoplatelets orientation in ensemble

Addressing the exciton fine structure in colloidal nanocrystals: the case of CdSe nanoplatelets

We study the band-edge exciton fine structure and in particular its bright-dark splitting in colloidal semiconductor nanocrystals by four different optical methods based on fluorescence line narrowing and time-resolved measurements at various temperatures down to 2 K. We demonstrate that all these methods provide consistent splitting values and discuss their advances and limitations. Colloidal CdSe nanoplatelets with thicknesses of 3, 4 and 5 monolayers are chosen for experimental demonstrations. The bright-dark splitting of excitons varies from 3.2 to 6.0 meV and is inversely proportional to the nanoplatelet thickness. Good agreement between experimental and theoretically calculated size dependence of the bright-dark exciton slitting is achieved. The recombination rates of the bright and dark excitons and the bright to dark relaxation rate are measured by time-resolved techniques

Linguistic Mechanisms in Marketing Names on the Example of Company Names

Obiektem bliższej obserwacji w niniejszym artykule są różnego rodzaju nazwy firm. Należą do nich zarówno nazwy sklepów, salonów i hurtowni, jak również nazwy zakładów handlowych, rzemieślniczych i usługowych różnorodnych branż: budowlanej, finansowej, gastronomicznej, kosmetycznej, medycznej, motoryzacyjnej, turystycznej itd. Przedmiotem niniejszego opracowania jest ustalenie i analiza językowych mechanizmów służących brandingowi, czyli tworzeniu nazw marketingowych we współczesnej chrematonimii na przykładzie polskiego nazewnictwa firmowego. Materiał badawczy został zebrany na podstawie Katalogu Firm Serwisu „TuWroclaw.com” dla Wrocławia. Biorąc pod uwagę sposoby tworzenia nazw firmowych w Polsce można zauważyć, że mechanizmy te reprezentują dużą otwartość słowotwórczą i wynikające z tego bardzo zróżnicowane struktury: 1) jedno- i wielowyrazowe, 2) złożone zarówno z elementów rodzimych, jak i bardzo modnych współcześnie członów obcego pochodzenia, 3) motywowane bezpośrednio, jak i w sposób pośredni lub 4) całkowicie nieczytelne pod względem słowotwórczym i semantycznym. Analiza nazw firmowych, wpisujących się w język marketingowy i związanych z intensywnym rozwojem cywilizacyjnym, pozwala zauważyć coraz silniej uwidaczniającą się tendencję do ekonomiczności języka.The aim of this paper is to determine and analyse language mechanisms used in branding, i.e. creating marketing names in contemporary chrematonyms on the example of Polish company names. The object of the analysis are various establishment names. These include names of shops, salons and wholesale warehouses, as well as trade, craft and service industries of various sectors: construction, finance, catering, cosmetics, medical, automotive, tourism, etc. The research material was collected on the basis of the Directory of Companies for Wrocław "TuWroclaw.com". Taking into account the ways in which company names are created in Poland, it can be seen that these mechanisms represent a great openness to word formations and, as a result, a great openness to very diverse structures: 1) single- and multi-word structures, 2) structures composed of both native and (at present very fashionable) foreign elements, 3) structures motivated directly or indirectly, 4) completely illegible structures in terms of word formations and semantics. The analysis of company names which belong to the marketing language and are related to the intensive development of civilization in recent decades allows us to notice an increasingly visible tendency to economise with language