Ordered Arrays of Nanorods Obtained by Solid-Liquid Reactions of LaOCl Crystals

A new top-bottom approach is developed to prepare ordered arrays of nanorods, based on controlled etching, as exemplified by the case of LaOCl crystals. Molten-salt issued LaOCl was applied as a precursor, with highly anisotropic crystals oriented along the [001] axis. These LaOCl flat crystals are reactive toward aqueous solutions at room temperature, yielding ordered assemblies of rod-like crystals. Depending on the reaction mixture composition, nanorods of LaOCl itself or other La compounds can be obtained. The morphology of the products obtained in the solutions can be finely controlled by adding extraneous chemical species which modify the etching kinetics. Thus, LaOCl reacts with the acidic phosphate solutions, leading to the array's of LaPO4 nanorods, oriented along the [001] axis of the initial Solid. By contrast, reaction with aqueous HCl produced assemblies of perpendicular rods, oriented along the [100] and [010] axes. The catalytic properties of the nanorods as obtained were tested in the decomposition of isopropanol. Strong differences of acid-base properties of differently oriented LaOCl particles have been observed.