we will present a detailed investigation of intersubband transitions process in core-multi shells quantum dots. the confined wave functions and eigenenergies of electrons in quantum dots have been calculated under the effective-mass approximation by solving a three-dimensional schrodinger equation. excellent dependence is found between size effects, time relaxation and degenerate four wave mixi...

Carbon quantum dots (C-QDs) are becoming a desirable alternative to metal-based QDs and dye probes owing to their high biocompatibility, low toxicity, ease of preparation, and unique photophysical properties. Herein, we describe fluorescence bioimaging of zebrafish using C-QDs as probe in terms of the preparation of C-QDs, zebrafish husbandry, embryo harvesting, and introduction of C-QDs into e...

We determine the level shifts induced by cotunneling in a Coulomb blockaded carbon nanotube quantum dot using leading-order quasidegenerate perturbation theory within a single nanotube “shell.” It is demonstrated that otherwise degenerate and equally tunnel coupled K and K ′ states are mixed by cotunneling and therefore split up in energy except at the particle-hole-symmetric midpoints of the C...

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The luminescent capability of graphene quantum dots (GQDs) was investigated and compared with that of carbon nanodots (C-dots) obtained from the same functionalization process. It was found that the optical gain of GQDs is higher than that of C-dots due to their geometrical advantages such as larger surface area to volume ratio and smaller volume. Under optical excitation at 266 nm, lasing emis...

We report the relatively large red-shift effect observed in down-shifting carbon quantum dots (CQDs) that is anticipated to have a positive impact on the power conversion efficiency of solar cells. Specifically, with an excitation wavelength of 390 nm, CQDs of different sizes, exhibited down-shifted emission peaks centered around 425 nm. However, a solution comprised of a mixture of CQDs of dif...

We investigate linear and nonlinear transport in interacting single-wall carbon nanotubes (SWCNTs) that are weakly attached to ferromagnetic leads. For the reduced density matrix of a SWCNT quantum dot, equations of motion which account for an arbitrarily vectored magnetisation of the contacts are derived. We focus on the case of large diameter nanotubes where exchange effects emerging from sho...

We have measured the differential conductance of individual multiwall carbon nanotubes. Coulomb blockade and energy level quantization are observed. The electron levels are nearly fourfold degenerate (including spin) and their evolution in magnetic field (Zeeman splitting) agrees with a g factor of 2. In zero magnetic field the sequential filling of states evolves with spin S according to S = 0...

Ferromagnetic contacts put in proximity with carbon nanotubes induce spin and orbital polarizations. These polarizations affect dramatically the Kondo correlations occurring in quantum dots formed in a carbon nanotube, inducing effective fields in both spin and orbital sectors. As a consequence, the carbon nanotube quantum dot spectral density shows a fourfold split SU(4) Kondo resonance. Furth...