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This paper investigates the structure, morphology and antimicrobial properties of silver-containing nanocomposites based on interpolyelectrolyte complexes (IPEC) of pectin with polyethylenimine, cationic starch or chitosan as a cationic polyelectrolyte. The reduction of silver ions was carried out by thermochemical technique by heating of the interpolyelectrolyte–metal complexes, which in turn prepared by adsorption of ions on IPEC. The chemical reduction was also performed using ascorbic acid as reductant. The temperature and time needed to produce the nanocomposites at which completely reduction of silver ions occurs are 150 °C and 30 min. It is revealed that during thermochemical reduction depending on the type of cationic polyelectrolyte (PEI, cationic starch, chitosan), silver nanoparticles with an average size of 4.1, 5.3 and 4.7 nm, respectively, are formed. Various mechanisms of thermochemical reduction for interpolyelectrolyte–metal complexes containing polymers with aminogroups or polymers with the glucopyranose units are considered. It is found that the silver-containing nanocomposites, formed by thermochemical reduction, exhibited higher antimicrobial activity against strains of S. aureus and E. coli than ones obtained using ascorbic acid. [ABSTRACT FROM AUTHOR]

The structure and properties of Cu/Cu2O-containing nanocomposites formed by chemical reduction of Cu2+ ions in interpolyelectrolyte–metal complexes (IMC) at different molar ratios [NaBH4]: [Cu2+] and reduction times were studied by methods of wide- and small-angle X-ray scattering, transmission electron microscopy, thermomechanical analysis, and antimicrobial tests. Optimal conditions ([NaBH4]: [Cu2+] = 6.0, reduction time ≥ 120 min) for the formation of copper-containing nanocomposites based on interpolyelectrolyte complexes and Cu/Cu2O core–shell nanoparticles have been established by X-ray diffraction analysis. Owing to the above conditions, the structural manifestation of the metal copper phase is fully realized. Applying transmission electron microscopy, it was found that at molar ratio [NaBH4]: [Cu2+] = 6.0, and reduction time of 40 min and 180 min, accordingly, the nanocomposites with average nanoparticles size of 4.1 nm and 12.4 nm are derived from IMC, respectively, what correlates with effective size of the nanocomposites' heterogeneity regions, lp. Thermomechanical analysis has shown that raise in the amount of reducing agent or the duration of reduction of Cu2+ ions in IMC is accompanied by elevation in the glass transition temperature, which reaches a constant level, boost in the temperature of transition to the viscous state Tf and decrease in the relative deformation of nanocomposites. The antimicrobial investigations of the elaborated nanocomposites revealed they possess an antimicrobial activity against S. aureus and E. coli strains. [ABSTRACT FROM AUTHOR]

The structure and properties of silver-containing nanocomposites formed by the method of thermochemical reduction of Ag+ ions in polyelectrolyte-metal complexes pectin–Ag+–polyethyleneimine were studied using X-ray diffraction analysis, thermogravimetric analysis, pyrolysis mass spectrometry, transmission electron microscopy and antimicrobial test. The optimal parameters for the formation of nanocomposites based on interpolyelectrolyte complexes of pectin–polyethyleneimine and Ag nanoparticles (reduction temperature T = 150 °C, reduction time t = 30 min) have been found by X-ray diffraction analysis, in which the structural manifestation of the silver metal phase is fully realized. Using transmission electron microscopy, it was found that nanocomposite formed by thermochemical reduction of Ag+ ions at 150 °C for 30 min has an average nanoparticle size of 4.1 nm that less than for nanocomposite obtained at T = 120 °C during the same reduction time (average nanoparticle size is 5.8 nm). Ag nanoparticles obtained by using a typical reducing agent (NaBH4) have an average size equals 3.8 nm. It was revealed that nanocomposites obtained by thermochemical method have significantly higher antimicrobial activity compared with nanocomposites obtained by chemical reduction of Ag+ ions using NaBH4. A mechanism of thermochemical reduction of silver ions in IMC pectin–Ag+–polyethyleneimine, which is based on the transfer of electrons from the nitrogen atoms of amino groups PEI to Ag+ ions, has been investigated by destructive processes that occur at the same time. [ABSTRACT FROM AUTHOR]