No abstract

Silver nanoparticles were synthesized at 293÷353 K temperature range by NaBH4 and HCOOH solutions with low concentration at polyethyleneglycol having average molecular weight of 40000 and 200 kDa gum arabic medium. Obtained silver nanoparticles were studied using methods of X-ray diffraction, UV-Vis, FTIR spectroscopy, scanning electron microscope. It was determined that sizes of silver nanoparticles which stabilize at polymer medium vary from 12 to 26 nm range depending on mole ratio, temperature and reduction medium of initial substances. It was shown by FTIR-spectroscopy that -OH and -COOH groups in polymer take an active part in stabilization of silver nanoparticles. It was determinated by UV-Vis study of silver nanoparticles containing polymer composition in aqueous condition that 412 nm which is specific to silver atoms do not change sharply for 4-5 days.

The work presents the results of a thermodynamic study of the Er-Te system by the method of electromotive forces (EMF) in the temperature range of 300-450 K. From the EMF measurements of the concentration cells relative to the Er and ErTe electrodes, the partial thermodynamic functions of ErTe and Er in the alloys are determined, based on which the standard thermodynamic formation functions and the standard entropies of the intermediate compounds ErTe3, Er2Te3, and ErTe are calculated. A comparative analysis of the obtained data with the literature is carried out.

The quartenizeid chloride derivative of natural polyaminosaccharide chitosan was synthesized in two stages with acetate aldehyde and methyl iodide chemical reaction and ion replacement, which could be soluble in the water and wide pH ranges. The synthesis of the homopolymer was initially carried out with acetate aldehyde in Schiff reaction, and reduction was held on with the presence of NaBH4. The quaternization was accomplished in the acetonitrile medium with methyl iodine by continuous exposure of N2.7-8% quartenized N,N-diethyl, N-methyl chitosan iodine were synthesized with 89-91% yield, obtained by deprotonation of amine groups, with reaction of CH3J and N,N-diethyl chitosan. The ion exchange was carried out at 10% NaCl solution during 24 hours and N,N-diethyl, N-methyl chitosan chloride was obtained. Synthesis was performed with simpler and chemically effective methods compared to previous studies. The structure of product was characterized by FT-IR, UV-Vis, NMR, SEM, TGA, DTA and elemental analysis was determined. Functional changes in the structure of macromolecules were monitored with NMR and UV-Vis, and it was proved that, the main intermediate product was composed to be N,N-diethyl carbocation carrying >C=N-chromophore group. The increasing percent of carbon in content while alkylation is depeering and the presence of halogenated ions (Cl-or J-) after quaternization were observed. It has been determined that, the solubility of N,N-diethyl,N-methyl chitosan chloride or iodide in water and in pH =1-10 increased frequently. Key words. Chitosan; alkylation; diethylmethyl chitosan iodine; quartenization; UV-Vis; NMR

No abstract