High-temperature and spectroscopic study of thorium phosphates

Double thorium phosphates M ^k Th_3−k (PO₄)_4−k (M^I = Li, Na, Ag, K, Rb, Tl, Cs; M^II = Cd, Ca, Sr, Pb) and thorium phosphate diphosphate Th₄(PO₄)₄P₂O₇ were synthesized by a high-temperature solid-phase reaction. The double thorium phosphates crystallize in the monoclinic system [space group C2/c for M^ITh₂(PO₄)₃ and P2₁/n for M^IITh(PO₄)₂], and the compound Th₄(PO₄)₄P₂O₇, in the rhombic system (space group Pcam). The bands in the IR spectra were assigned. The double thorium phosphates exhibit high thermal stability. The compounds KTh₂(PO₄)₃, CaTh(PO₄)₂, and Th₄(PO₄)₄P₂O₇ were studied by high-temperature X-ray diffraction.     

Study of DNA interaction with cobalt ferrite nanoparticles

Interaction of cobalt ferrite nanopowder and nucleic acid was investigated. Superparamagnetic cobalt ferrite nanoparticles (6-12 nm) were prepared by mechanochemical synthesis. Structure of the nanopowder was characterized using X-ray diffraction. It was shown that cobalt ferrite nanoparticles were associated with ssDNA and dsDNA in Tris-buffer resulting in bionanocomposite formation with mass weight relation nanoparticles: DNA 1:(0.083 +/- 0.003) and 1:(0.075 +/- 0.003) respectively. The mechanism of interaction between a DNA and cobalt ferrite nanoparticles was considered basing on the whole set of obtained data: FTIR-spectroscopy, analyzing desorption of DNA from the surface of the particles while changing the chemical content of the medium, and on the modeling interaction of specific biomolecule fragments with surface of a inorganic material. It was supposed that the linkage was based on coordination interaction of the phosphate groups and oxygen atoms heterocyclic bases of DNA with metal ions on the particle surface. These data can be used to design specific magnetic DNA-nanoparticles hybrid structures.     

Optical absorption and structure of energy bands of GdNi<Subscript>5 − x</Subscript>Cu<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript> intermetallic compounds

Optical properties of intermetallic compounds GdNi_{5 ? x} Cu _x (x = 0, 0.5, 1, 1.5, and 2) have been studied in a spectral range from 0.22 to 15 μm using the ellipsometry method. The substitution of copper for nickel has been found to lead to local changes in the interband optical conductivity spectra. A new quantum-absorption band, whose intensity increases substantially with increasing copper content, has been found at 3–4 eV. The relaxation and plasma frequencies of conduction electrons, which were calculated using data on the optical parameters, also depend on the concentration. Self-consistent calculations of the electronic structure of the intermetallic binary GdNi₅ compound have been performed using the LSDA + U method. The density of electronic states for two spin projections and the frequency dependence of the interband optical conductivity of the compound have been calculated.