Stabilization of Nanodispersed Cerium Phosphate in Matrices Containing Cellulose Derivatives, Citric Acid and Metronidazole.

High-dispersion nanocomposite materials based on cerium(III) orthophosphate stabilized with different forms of cellulose (methylcellulose (MC), carboxymethylcellulose (CMC) and sodium carboxymethylcellulose (CMCNa)) with the addition of citric acid were synthesized by chemical precipitation. Experimental samples modified with metronidazole were obtained. A comprehensive analysis of their phase composition, morphology, and physicochemical characteristics was performed using X-ray diffraction, transmission electron microscopy and IR spectroscopy. According to the results of physicochemical studies all synthesized nanocomposites contained nanocrystals with a bimodal size distribution (width 3-6 nm, length 15-200 nm), depending on the matrix composition, and diffraction peaks characteristic of CePO4. IR spectroscopy suggested a mechanism for the formation of chemical bonds: cellulose polymer chains are retained on the CePO4 surface mainly through a branched network of weak hydrogen bonds, while the carboxylate groups of citric acid form coordination bonds with Ce3+. A positive effect of citric acid on limiting the linear dimensions of CePO4 crystallites in the presence of a cellulose matrix was established.