Transformation behavior of layered LaOCl to La(OH)3 nanostructures in water

LnOCl (Ln = La, Nd, and Sm) with layered structure was transformed into Ln(OH)3 in water. The electron microscopy images of La(OH)3 showed various nanostructures such as nanoneedles, nanowires, nanoneedle chains, nanoneedle bundles, and nanochain bundles. Although the formation mechanism is not accompanied by a typical exfoliation of LaOCl into individual sheets because of no existence of true van der Waals gap between layers, this transformation proceeds in highly controlled manner to yield regular nanostructures. The nanoneedles are the fundamental building blocks for the evolution of other complex one-dimensional structures, depending on their assembly fashions. The length and number of nanoneedles constituting single bundle structure can be slightly controlled by adjusting the pH values of aqueous solutions. The shape of LaOCl precursor plays a key role in the final size, morphology, and alignment of La(OH)3 nanoneedles at room temperature.