A viscous tertiary amine and triol, triethanolamine, is engaged in this work as a structure-shaping agent to prepare the high-quality ZnO nanosheets under mild conditions, i.e., at nearly neutral pH and low temperature. The X-Ray diffraction and transmission electron microscopic results validated that the obtained ZnO nanosheets show the perfect hexagonal nanostructures, with an average edge length of 46.6+/-8.5 nm. The triethanolamine molecule is deemed to act as the hydroxide anion generator as well as the surface modification agent, as evidenced by the FT-IR spectrum. The mechanism for the formation of ZnO nanosheets has been discussed. The simple strategy allows the efficient syntheses of fluorescent ZnO with the strong emission around 560 nm, which was attributed to the defect emission of the ZnO nanostructures. The predominant fluorescent properties have been successfully used in the field of cellular imaging, suggesting their promising biomedical applications. (C) 2011 Elsevier B.V. All rights reserved.