Sergei A. Cherevkov

Comparative analysis of Raman spectra of PbS macro- and nanocrystals

A comparative analysis of the Raman spectra of bulk PbS and PbS nanocrystals with average diameters of 6.6 and 3.8 nm has been performed. It is shown that the bands due to the LO phonons at the Γ point of the Brillouin zone dominate in the first- and second-order Raman spectra of the nanocrystals. Based on the analysis of the relative band intensities for the first- and second-order spectra a qualitative conclusion is drawn: the electron-LO-phonon interaction in PbS nanocrystals increases with a decrease in their size.

Optical properties of ordered superstructures formed from cadmium and lead chalcogenide colloidal nanocrystals

The optical properties of three-dimensional ordered superstructures formed on glass substrates by self-assembly of cadmium selenide or lead sulfide nanocrystals (NCs) are investigated and compared to the optical properties of the initial NC colloidal solutions. The formation of the superstructures is strongly correlated to the presence of oleic acid molecules on the surface of the NCs. It is found that the absorption band of the NCs in the superstructures is broadened and shifted to shorter wavelengths in comparison with the absorption band of the NCs in solution. The luminescence spectra of the NCs in the superstructures also differ from the spectra of the NCs in solution. The observed modification of optical properties of superstructures is a manifestation of interactions between the NCs and the chemical environment within the superstructures.

Self-organization of lead sulfide quantum dots of different sizes

X-ray structural analysis is used for investigation of structures, obtained by self-organization from nanoparticles - lead sulfide (PbS) quantum dots (QDs) of different sizes - deposited on a glass substrate or embedded in a porous matrix. These nanostructures obtained by both methods represent ordered close-packed structures of the nanoparticles. The configuration of obtained structures does not depend on the nanoparticle size and type of substrate and matrix.

Cadmium Chalcogenide Nano-Heteroplatelets: Creating Advanced Nanostructured Materials by Shell Growth, Substitution, and Attachment

The current direction in the evolution of 2D semiconductor nanocrystals involves the combination of metal and semiconductor components to form new nanoengineered materials called nano-heteroplatelets. This Review covers different heterostructure architectures that can be applied to cadmium chalcogenide nanoplatelets, including variously shaped shell, metal nanoparticle decoration, and doped and alloy systems. Here, for the first time a complete classification of nano-heteroplatelet types is provided with recommended notations and a systematization of the existing knowledge and experience concerning heterostructure formation techniques, addressing the morphology, optoelectronic and magnetic properties, and novel features of different heterostructures. This Review is also devoted to possible applications of these heterostructures and of one-component nanoplatelets in multiple fields, including light-emitting devices and biological imaging.

Nonradiative resonant energy transfer between PbS QDs in porous matrix

Nonradiative fluorescence resonance energy transfer (FRET) between lead sulfide quantum dots (QDs) of two different sizes embedded in porous matrix is observed by a fluorescence spectroscopy. Analysis of decays of photoluminescence from QD mixture shows that energy transfer in studied systems is determined by static quenching, specific for direct contact between QD-donor and QD-acceptor in the QDs close-packed ensembles. From steady-state spectral analysis it was found that efficiency of energy transfer depends on the molar ratio QD-donor/QD-acceptor and energy transfer from the donor to the acceptor passes by several channels.

Raman analysis of chemical substitution of Cd atoms by Hg in CdSe quantum dots and rods

Abstract. We investigate nanocrystals of ternary compounds CdXHg1−XSe with 0<X<1 using a Raman scattering technique at room temperature. We obtained the correlation between nanocrystal (NC) chemical composition and the frequencies of CdSe-like LO and the HgSe-like TO and LO-modes. It is shown that the crystalline structure of the original CdSe NCs used for Cd/Hg substitution, either zinc blende or wurtzite, strongly affects the structural properties of the resultant CdXHg1−XSe quantum dots and rods.

X-ray structural analysis of two-dimensional assembling lead sulfide nanocrystals of different sizes

Abstract. We report on the structural investigation of self-organized assemblies of PbS nanocrystals (NCs) of different sizes, which were deposited on a glass substrate or embedded in a porous matrix. Regardless of the NC size and the type of the substrate and matrix, the assemblies were ordered in two-dimensional superlattices with densely packed NCs.