L. I. Gurinovich

The effect of an external electric field on photoluminescence of CdSe colloidal nanoparticles of different topologies

Photoluminescence of CdSe colloidal nanocrystals of different topologies in an external electric field has been studied. It has been found that quenching of photoluminescence, which takes place in quantum dots, is proportional to the square of the field, and in elongated nanocrystals quenching of photoluminescence is proportional to the square root. A physical model of the mechanism of quenching based on tunneling of free charges through potential barrier nanocrystal/matrix has been proposed.

LUMINESCENCE SPECTRA OF WATER-SOLUBLE CdSe NANOCRYSTALS UNDER A PROLONGED LASER IRRADIATION

For biological applications of quantum dots it is important to develop the technology for water soluble highly luminescent cadmium selenide nanocrystals. Obviously, the as-synthesized hydrophobic nanocrystals can not be utilized as fluorescent markers in immunoanalysis since such material must be water compatible [1-2]. The problem of synthesis and photostability of high fluorescent aqueous solutions for the visible based on soluble semiconductor nanocrystals is a topical question.

Electro-absorption of an ensemble of close-packed CdSe quantum dots

Highly monodisperse CdSe quantum dots 1.8 nm in size were synthesized capped with surface monolayer of 1-thioglycerol. The optical absorption of thin films of matrix free close- packed and isolated in PMMA matrix quantum dots was studied at various electric field biases. The broadening and red shift of optical transitions in close-packed ensemble against isolated is attributed to the formation of collective electronic submini-bands between interacting nanocrystals. The reversible collapse of collective electronic subminibands has been achieved by applying of strong electric field to the thin film of close-packed quantum dots.

Electrons and photons in mesoscopic structures: quantum dots in a photonic crystal and in a microcavity

Mesoscopic structures with characteristic size either of the order of an electron de Broglie wavelength in semiconductors (1 - 10 nm) or close to the optical photon wavelength (100 - 1000 nm) exhibit non-trivial properties due to modified electron or photon density of states. 3D spatial confinement of electrons in nanocrystals (quantum dots) results in size- dependent energies and probabilities of optical transitions. The photon density of states can be modified in structures with strong modulation of the refractive index in three dimensions (photonic crystals) and in microcavities. Because of the essentially different electron and photon wavelengths, electron and photon densities of states can be engineered separately within the same mesostructure. We report here on synthesis and properties of semiconductor quantum dots corresponding to the strong confinement limit embedded either in a photonic crystal exhibiting a pseudogap or in a planar microcavity. We show that the interplay of electron and photon confinement within the same structure opens a way towards novel light sources with controllable spontaneous emission. Spontaneous emission which is not an inherent property of quantum systems but a result of their interaction with electromagnetic vacuum can be either promoted or inhibited depending on the modification of the photon density of states in a given mesostructure.