Synthesis and Aqueous Colloidal Solutions of RE2(OH)5NO3•nH2O (RE = Nd and La)

A new, simple route leading to layered rare-earth hydroxy nitrates was developed. The pH-independent procedure uses ethanol containing alkali-metal hydroxide (KOH, RbOH, or CsOH) as a solvothermal medium. Two new, layered rare-earth hydroxy nitrates (LRHs), Nd-2(OH)(5)NO3 center dot nH(2)O and La-2(OH)(5)NO3 center dot nH(2)O, were prepared by this nonaqueous solvothermal reaction. Because the RE = Nd and La members have not yet been synthesized in an aqueous system, the successful synthesis of these compounds implies the completion of the RE2(OH)(5)NO3 center dot nH(2)O (RE = rare earths) series. The typical properties of a layered structure was demonstrated by ready ion-exchange reactions between NO3 and some orgame anions such as decanoate, decanesulfonate, and decyl sulfate. In particular, the as-synthesized hydroxide from solvothermal reaction, where the alkali-metal nitrates are partially intercalated in the interlayer gallery, form an aqueous colloidal solution under ultrasonic treatment. Hydration of the LRHs intercalated with alkali-metal salts results in the formation of colloidal LRH suspensions in water. The colloidal character of the LRH solutions is supported by the Tyndall effect, TEM, and AFM images. ((C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)