One-pot synthesis of hexagonal ZnO nanosheets with a novel structure-directing agent and their application in cell imaging.

Recently, ZnO nanostructures with various morphologies have been synthesized with different structure directing agents. Among these works, little reports have been focused on the syntheses of the ZnO nanostructures at nearly neutral pH and relatively low temperature. This work explores a novel structure-directing agent, tris(hydroxymethyl)aminomethane (tris), for one-pot synthesis of hexagonal ZnO nanosheets at nearly neutral pH (i.e., 7.3) and low temperature (i.e., 80 degrees C). From the XRD and TEM results, the obtained ZnO nanosheets possess the perfect single crystalline structures. The tris molecule acts not only as the hydroxide anion generator, but also as the surface modification agent, as evidenced by the FT-IR spectrum. The yield of the products can be up to about 1.0 g per pot, indicating the industrial prospects for its large-scale and low-cost synthesis. The mechanism of nucleation and growth of the ZnO nanosheets has been proposed. The obtained ZnO nanosheets own the sharp strong fluorescence at 590 nm, which can be attributed to the defects on the surface of the ZnO nanostructures. In virtue of the fluorescent properties, the ZnO nanosheets have been successfully used for cell imaging, suggesting their promising clinic and biomedical applications.