Under hydrothermal conditions, we prepared gamma-A1OOH 1D nanorods and 2D nanoflakes by manipulating the amount of a base in the reaction mixture (i.e., pH control). The acidic conditions turned out to be favored toward the formation of the nanorods, and the basic conditions toward the formation of the nanoflakes. One possible mechanism for the formation of these materials was proposed. The nanorods exhibited a blue shift in the emission spectrum, but the nanoflakes did not. Our simple and straightforward method might be applied to prepare other nanocrystals with controllable sizes and shapes. (c) 2007 Elsevier B.V. All rights reserved.