ACS PRF | ACS
All e-Annual Reports
42542-G10
Colloidal Synthesis of High-Quality Lanthanide-Oxide Nanocrystals
The primary goal of this proposed research is to develop new synthesis methods for producing high-quality lanthanide-oxide nanocrystals. The new synthesis is based on a high-temperature colloidal method without precursor injection. Such synthesis, without precursor injection, is easy for small-scale laboratory synthesis, and more importantly, it can open an opportunity to the industrial preparation of high-quality nanocrystals in a large quantity at a low cost. The ability to produce nanocrystals at low cost and high quality is important to technological applications such as chemical and biological detection, catalysts, solar cells, lasers, and light-emitting diodes (LED).
In past two years, our research work focused on three directions. The first direction is the synthesis and assembly of lanthanide-oxide nanocrystals. In the second direction, we extend the principles—which we gain from the research of synthesizing lanthanide-oxide nanocrystals—to make size- and shape-controlled II-VI semiconductor nanocrystals via a synthesis without precursor injection. In the third direction, we have developed a new synthesis for making high-quality actinide oxide nanocrystals such as UO2.
Our accomplishments are listed as follows. (1) We have mapped out detailed synthesis conditions for making lanthanide oxide nanocrystals such as Gd2O3, Eu2O3, and Sm2O3. We have systematically studies the assemblies of these nanocrystals using TEM, XRD, UV-Vis absorption and fluorescence spectroscopy. (2) We have developed a non-injection synthesis for making high-quality II-VI semiconductor nanocrystals. Such a new synthesis allows the control of crystal structure of these nanocrytals, by which we have make zinc-blende CdSe nanocrystals. Interestingly, zinc-blende CdSe nanocrystals exhibit different properties from wurtzite CdSe. For zinc-blende and wurtzite CdSe, nanocrystals with an identical absorption peak position for the first exciton transition band exhibit a nearly identical size. However, the fine structures in their absorption spectra are different. The gap between the first (1S3/21Se) and second (2S3/21Se) exciton transition peaks for zinc-blende particles is clearly wider than that for wurtzite ones. The results herein open a new opportunity to design new functional materials by controlling their crystal structures. In addition, we have achieved shape-controlled synthesis of II-VI nanocrystals such as CdS, CdSe nanorods and nanowires. (3) We have developed a new method for producing monodispersed, colloidal uranium-dioxide nanocrystals. In addition, we have systematically mapped out the functions of the solvents (oleic acid, oleylamine, and 1-octadecene) in the synthesis, and we found that N-(cis-9-octadecenyl)-oleamide—a product of the condensation of oleic acid and oleylamine—can substantially affect the formation of UO2 nanocrystals. Importantly, these results provide fundamental insight into the mechanisms of UO2 nanocrystal synthesis. Moreover, because a mixture of oleic acid and oleylamine has been widely used in synthesizing a variety of high-quality metal or metal-oxide nanocrystals, the results herein should also be important for understanding the detailed mechanisms of these syntheses.
So far, some of these results have been published in two papers: one communication in Angew. Chem. Int. Ed., and one communication in the Journal of American Chemical Society. In addition, two more manuscripts are under preparation
