Loading...
Please wait, while we are loading the content...
Similar Documents
A single-step synthesis and the kinetic mechanism for monodisperse and hexagonal-phase NaYF4:Yb, Er upconversion nanophosphors.
| Content Provider | Semantic Scholar |
|---|---|
| Author | Shan, Jingning Ju, Yiguang |
| Copyright Year | 2009 |
| Abstract | A single-step synthesis for monodisperse and hexagonal-phase (beta) NaYF(4):Yb, Er upconversion nanophosphors (UCNPs) with a consistent hexagonal prism shape in the size range from 18 to 200 nm was achieved. The kinetic mechanisms for the particle phase transition and growth were examined. The beta-UCNPs were obtained via co-thermolysis of trifluoroacetate precursors in octadecene (ODE) with combined ligands of oleic acid (OA) and trioctylphosphine (TOP). The experimental results showed that the combined OA-TOP ligand was crucial for changing the surface energy and controlling the particle shape over a broad size range. It was found that the particle sizes could be controlled by varying the molar ratios of Na(CF(3)COO)/Re(CF(3)COO)(3) (Re = Y, Yb, and Er). A high Na/Re ratio accelerated the cubic-phase (alpha)-->beta transition and promoted the growth of smaller beta-UCNPs. The formation of beta-UCNPs was classified into kinetic and diffusion controlled stages, depending on the reaction temperature and the dominant crystalline phases formed in each stage. In stage I, 250-310 degrees C, NaF generation was the limiting step and alpha-UCNPs were formed via a 'burst of nucleation'. In stage II, above 310 degrees C, the alpha-UCNPs formed were re-dissolved and the growth of beta-UCNPs was a diffusion controlled process governed by the Gibbs-Thompson effect. A quasi-steady-state species assumption for NaF and a chemical potential equilibrium in the solution were introduced to explain the particle size dependence on Na/Re ratios. The study of UC luminescence showed that the UC intensity was proportional to the sizes of the beta-UCNPs. |
| Starting Page | 275603 |
| Ending Page | 275603 |
| Page Count | 1 |
| File Format | PDF HTM / HTML |
| DOI | 10.1088/0957-4484/20/27/275603 |
| PubMed reference number | 19531868 |
| Journal | Medline |
| Volume Number | 20 |
| Issue Number | 27 |
| Alternate Webpage(s) | http://engine.princeton.edu/Publications/Nanotechnology%202009.pdf |
| Alternate Webpage(s) | https://doi.org/10.1088/0957-4484%2F20%2F27%2F275603 |
| Journal | Nanotechnology |
| Language | English |
| Access Restriction | Open |
| Content Type | Text |
| Resource Type | Article |
