Vitaliy V. Slabko

Laser-induced wavelength-controlled self-assembly of colloidal quasi-resonant quantum dots.

Self-assembly of colloidal semiconductor quantum dots controlled solely by laser-induced interaction is demonstrated for the first time. Pairs of CdTe nanoparticles are formed under irradiation with nanosecond pulses at wavelengths 555 or 560 nm. Formation of pairs is justified by corresponding changes of absorption spectra. Conditions of the experiment are in excellent agreement with those predicted by the theory of laser-induced dipole-dipole interaction of QDs. The fraction of QDs assembled into pairs is up to 47%.

Synthesis and Characterization of Chitosan‐Based Polyelectrolyte Complexes Doped with Xanthene Dyes

Biocompatible chitosan-based polyelectrolyte complexes (PECs) doped with xanthene dyes (fluorescein, eosin Y, erythrosin B, rhodamine 6G) were synthesized and characterized by scanning electron microscopy, dynamic light scattering, zeta potential measurements, and absorption and luminescence (including polarized, time-resolved, and phosphorescence) spectroscopy. The results are discussed in terms of the mechanism and rigidity of dye-PEC binding, the heavy-atom effect in dyes and PEC stability. Eosin Y is found to be the optimal dopant, providing both a high dye content in PECs and a high quantum yield of fluorescence.

Simulating the absorption spectra of pairs of nanoparticles

Absorption spectra of pairs of particles with single resonance transitions are simulated in the dipole-dipole approximation. The results can be used in analyzing the spectra of samples obtained in studying the formation of pairs using quasi-resonant laser radiation.

Laser-induced Interaction of Multilevel Quantum Dots

A theoretical model is developed for describing the laser-induced interaction of a pair of multilevel semiconductor quantum dots. Spectral dependencies of interaction energy are calculated in dipole-dipole approximation for a pair of CdSe quantum dots in a quasi-resonant laser field, for cases of two identical quantum dots and those with differing transition wavelengths. Interaction energy of pair of multilevel quantum dots in the long-wavelength potential well is much higher than that of pair of two-level quantum dots. The increase of difference of resonance wavelengths of two interacting quantum dots leads to decrease of the potential well depth.

Synthesis and characterization of chitosan-based polyelectrolyte complexes, doped by quantum dots

Doping of polymer particles by a fluorophores results in the sensitization within the visible spectral region becoming very promising materials for sensor applications. Colloids of biocompatible chitosan-based polyelectrolyte complexes (PECs) doped with quantum dots (QD) of CdTe and CdSe/ZnS (with sizes of 2.0-2.4 nm) were synthesized and characterized by scanning electron microscopy, dynamic light scattering, ζ-potential measurements, absorption and luminescence (including time-resolved) spectroscopy. The influence of ionic strength (0.02-1.5 M) on absorption and photoluminescence properties of encapsulated into PEC and unencapsulated quantum dots was investigated. The stability of the emission intensity of the encapsulated quantum dots has been shown to be strongly dependent on concentration of quantum dots.

On the possibility of inversion-free amplification of light by dichroic molecules in an external orienting field

The possibility of inversion-free amplification of light by dichroic molecules that can be oriented selectively over states by application of an external field is analyzed. The effect of the relation between the life-time of the excited state and the time of stabilization of orientation equilibrium on the amplification factor is considered on the basis of the coupled system of Boltzmann equations for the ground and excited states, which are characterized by different energies of interaction with the orienting field.