Synthesis and characterization of nanoparticles

Nanoparticles have potential applications as catalyst and in optical, electrical and magnetic devices. Metallic nanoparticles can be synthesized via physical vapor deposition. Nanoparticles synthesized using this technique has uniform particle size distributions. An example of uniform size distribution is provided for Pt nanoparticles.

Pt nanoparticles synthesized via electron beam evaporation has an average particle size of ~ 3 nm.

Built upon the knowledge of single layer metallic nanoparticles, we can synthesize three dimensional (3D) arrays of nanoparticles. This will take us one step closer for device applications.

Using physical vapor deposition, we can precisely control the spacing (h) between each layer of nanoparticles as shown schematically.

3D arrays of Cu nanoparticles have been synthesized in Mo matrix. First, using magnetron sputtering, nanolayers made of Cu 6 Å / Mo 200 Å were produced. Clear interface between Cu and Mo can be resolved by TEM. Furthermore, Cu has metastable bcc structure as evidenced from TEM studies. These nanolayers were then subjected to a controlled high vacuum annealing environment. Cu segregated along layer interfaces and formed nanoparticles. As a result 3D arrays of Cu nanoparticles embedded in Mo matrix was formed.

These Cu nanoparticles have an average particle size of 2 nm. Cu remains metastable bcc structures after annealing. The electronic properties of these nanolayers are also studied.

References

“Microstructure and electronic properties of CuÕMo multilayers and three-dimensional arrays of nanocrystalline Cu precipitates embedded in a Mo Matrix”, Journal of Applied Physics, 95 (2004) 3644. (PDF)