Interaction of kappa-carrageenan with nickel, cobalt, and iron hydroxides

In a previous paper, it was shown that the functional polysaccharide kappa -carrageenan acts as an efficient stabilizer to prevent the precipitation o f iron oxides and hydroxides up to very high pH values (Jones, et al. Collo id Polym. Sci. 2000, 278, 491-501). Here, this process was investigated for its application to synthesize stable cobalt and nickel oxide particles. Ni ckel hydroxide nanoparticles were well stabilized for long periods, while t he hydroxide of cobalt(II), although initially stable at pH 13, progressive ly showed some complex structure rearrangement, invoked by alkaline oxidati on of the primary particles. The final product of this oxidation/self-assem bly process are spherical, fluffy superstructures of cobalt(III) oxide plat elets with an overall diameter of 12 mum, in coexistence with 65-75% of fre e kappa -carrageenan.