Synthesis of soluble and size controlled SnO2 and CeO2 nanocrystals: application of a general concept for the low temperature, hydrolytic synthesis of organically capped oxide nanoparticles

Metal oxide (CeO2, SnO2) sols were prepared in such a way as to hinder the inorganic condensation reactions. Acetylacetone was added to cerium nitrate solutions before hydrolysis with ammonia solution, while solvolysis of anhydrous tin chloride with methanol was used for preparing SnO2 sols. The sols were then injected into dodecylamine at 160 °C, followed by heating at the resulting temperature for 1 h. A clear sol was obtained, from which the products were extracted by precipitation with methanol and dried. Analysis by X-ray diffraction and TEM demonstrated the presence of CeO2 and SnO2 nanocrystals, whose size depended on the metal concentration in the starting sol, ranging from 2.6 to 3.5 nm for CeO2 and from 1 to 1.9 nm for SnO2. The nanocrystals were soluble after the synthesis and redispersable in organic solvents, forming stable suspensions. The process appears to be easily generalizable to systems having similar hydrolytic chemistry.