Effect of Polysaccharide Additions on the Anion-Exchange Deposition of Cobalt Ferrite Nanoparticles

Текст статьи не публикуется в открытом доступе в соответствии с политикой журнала.A facile and rapid method easily reproducible in ordinary laboratory settings is proposed for preparing nanosized cobalt ferrite powders, where the precipitate used is a strongly basic anion exchange resin in the OH form. The effects caused by additions of polysaccharides having various chain natures and various molar weights on the composition, yield, and particle size of the deposition product are studied. Suggested mechanisms underlying these effects are studied. This method makes it possible to appreciably reduce the precursor annealing temperature compared to that in the state-of-art methods for preparing similar oxide systems due to the formation of highly reactive precursors. Optimal conditions are found to prepare stoichiometric precursors such that, once annealed at 600°C, would form a CoFe2O4 pure phase with particle sizes of 10–20 nm. The stability of hydrosols of the thus-prepared cobalt ferrite nanoparticles is studied by dynamic and electrophoretic light scattering. The prepared material is found to be useful for the design of magnetic core–shell hybrid nanostructures. © 2020, Pleiades Publishing, Ltd

Resistive Gas Sensors Based on Porous Sp-Containing Films Obtained by Dehydrohalogenation of PVDC and PVDC-PVC Copolymer

Resistive sensing responses of the thin films obtained by dehydrohalogenation of polyvinylidene chloride (PVDC) and polyvinylidene chloride–polyvinyl chloride (PVDC-PVC) copolymer were investigated. The structure of the samples was studied by transmission electron microscopy, Fourier-transform infrared spectroscopy and Raman spectroscopy. The analyses demonstrate the formation of a porous structure based on polyyne–polyene chains. The formation of a foam-like oxidized sp-rich structure was observed for the samples obtained via the chemical treatment of the PVDC. However, a loose film with a developed structure and a lower fraction of sp-hybridized carbon was observed for KOH-treated PVDC-PVC. The resistive sensing responses of both of the dehydrohalogenated structures were measured for various concentrations of acetone, acetic acid, ammonia hydroxide, methanol, ethanol, benzene and water. The interplay between the efficiency of the dehydrohalogenation of the films, their structure and sensing selectivity is discussed