Utkur MirsaidovI from the National University of Singapore was able to view the self-assembly of Au nanoparticle and Zn(NO3)2 nanocubes under the effects of a Transmission Electron Microscopy (TEM) beam and appropriate dark image processing using averaging and DRIFTS.
The nucleation phenomenon of gold nanocrystals from a Au(III) Chloride solution was preceded by observed phases that allow the condensation of atoms in a region. This condensation enables the formation of amorphous nanoclusters and is followed by nanocrystal formation and growth. As reported in Symposium SM07.01.01, Mirsaidovl’s team found that an electron beam can significantly affect the nucleation process because at higher beam intensities, the nucleation time of the Au(III)Cl solution could be accelerated. The beam then acts as a reducing agent, causing changes from the ionic Au3+ state to the metallic Au0.
But electron beams can sometimes damage or even destroy samples, such as seen by the Metal Organic Frameworks (MOFs) of Zn(NO3)2. This material is of cubic highly crystalline structure that could be imaged using TEM and can be viewed but the data collection must be made at intensities so low that the nucleation process is invisible. However, using image averaging and DRIFTS, the researchers were able to view the aggregation of the Zn(NO3)2 nanocubes in the same stepwise fashion as the gold nanoparticles (from solution, to dense fluid, to aggregates and finally to crystal).
If you are interested in learning more about Zn(NO3)2 MOFs or Au nanoparticles click here to view Dr. MirsaidovI’s presentation on the MRS Spring Meeting and Exhibit.