Making Nanocrsytals Stable in Solution

Newswise — Nanocrystals in solution interest researchers because their optical properties vary depending upon the crystal's size, making them potential candidates for use in biosensors, medical diagnostic technology and drug delivery. But research has been hindered by the challenge of processing stable, high-quality nanocrystals. A team of University of Arkansas researchers has found a way to create stable nanocrystals by enclosing them in chemical boxes.

Xiaogang Peng, associate professor of chemistry and biochemistry, and Wenzhuo Guo, J. Jack Li and Y. Andrew Wang reported their findings in the article, "Luminescent CdSe/CdS Core/Shell Nanocrystals in Dendron Boxes: Superior Chemical, Photochemical and Thermal Stability," by and Xiaogang Peng, published in the Journal of the American Chemical Society.

Nanocrystals in solution often become unstable when subjected to heat, light and chemical procedures. This instability lies, in part in the interactions between organic elements in the solutions and inorganic nanocrystals.

Peng and his colleagues solved this problem by using the organic material to create a box for the inorganic nanocrystals. They cross-linked organic surface ligands called dendrons, on each semiconductor nanocrystal. The global cross-linking of the dendron ligands sealed each nanocrystal in a dendron "box." The stability of CdSe box-nanocrystals against chemical, photochemical and thermal treatments dramatically improved when compared to the original dendron-nanocrystals, creating "super-stable" box nanocrystals.

The super-stable box nanocrystals can resist photo-oxidation for as long as 27 days. The inorganic nanocrystals inside the dendron boxes also can be dissolved out, resulting in the formation of empty dendron boxes, which one day may be useful in drug delivery devices.