Novel self assembly behavior for γ-alumina nanoparticles

In this study, self assembly behavior was induced for gamma-alumina nanoparticles by adsorption of dimethyl disulfide. Following this trend, we have developed a chemical process to obtain gamma-alumina in the nano scale. Scanning electron microscopy images of the prepared gamma-alumina showed big and strong agglomeration of the nanoparticles indicating that these nanoparticles have strong surface forces. Transmission electron microscopy images confirmed that the gamma-alumina nanoparticles 3-7 nm in size were converted to uniform spherical shape in the size range of 1-2 mm after shaking with dimethyl disulfide in the presence of n-hexane at room temperature. This phenomenon did not appear in the case of alumina in the micro scale. The surface properties of the prepared gamma-alumina in the nano scale were characterized and compared with the gamma-alumina in the micro scale by using low temperature nitrogen adsorption-desorption system, indicating that the specific surface area of the prepared gamma-alumina nanoparticles is larger than that of the gamma-alumina in the micro scale. Furthermore, micro- and mesa-pores were observed for the gamma-alumina nanoparticles while only mesoporous structure was detected for the gamma-alumina in the micro scale. These experimental results suggested that the self assembly behavior of the gamma-alumina nanoparticles may be due to the selective adsorption of dimethyl disulfide in the micropores of these nanoparticles to act as bridge linking the nanoparticles. (c) 2012 Chinese Society of Particuology and Institute of Process Engineering, Chinese Academy of Sciences. Published by Elsevier B.V. All rights reserved.