A simple room temperature solution-phase method has been developed to synthesize pure phase single-crystalline hexagonal beta-Co(OH)(2) nanoplates. The chemical composition and morphology of the as-prepared beta-Co(OH)(2) nanoplates were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), and selected area electron diffraction (SAED). The results indicated that the as-prepared beta-Co(OH)(2) nanoplates were composed of pure brucite-like beta-Co(OH)(2) phase with single-crystalline feature. The effect of polyethylene glycol (PEG), NH4OH, and NaOH on the morphology and size of beta-Co(OH)(2) nanocrystals were discussed in detail. The growth mechanism of the as-synthesized nanoplates was also discussed in detail based on the experimental results. (C) 2010 Elsevier B.V. All rights reserved.