New solvents help create better semiconductor nanocrystals

University of Arkansas researchers have used new solvents to create safe, inexpensive, high-quality semiconductor nanocrystals for use in industry.Their work appears as a ‘Hot Paper’ in the current issue of Angewandte Chemie, an international chemistry journal.

In the article, the authors – Xiaogang Peng, assistant professor of chemistry and biochemistry, and W. William Yu, postdoctoral research associate – present a new approach for developing synthetic chemistry to produce high quality semiconductor nanocrystals.

Because high quality nanocrystals are not readily available, the need for safe, simple, and inexpensive synthetic methods is of interest to scientists working in many different scientific fields.

In the past ten years, all relatively successful synthetic methods for creating semiconductor nanocrystals have been based on carefully selected co-ordinating solvents. The research of Peng and Yu is said to show that non-co-ordinating solvents make a better media for the synthesis of colloidal semiconductor nanocrystals.

‘The molecules of the non-coordinating solvents are chemically inert to the metal ions and the resulting nanocrystals,’ said Peng. This means that scientists can tune the chemical binding status of the metal ions using binding elements in the non-coordinating solvents.

Thus, the chemical reactivity of the metal ions can be fine-tuned to meet the desired balance between the nucleation – the stage generating seeds for the resulting nanocrsytals – and the growth of the seeds generated in the nucleation step.

This reportedly allows researchers better control over the formation of nanocrystals of uniform size. ‘Many properties of semiconductor nanocrystals, including their emission colours, are strongly size dependent,’ Peng said. ‘As a result, it is necessary to synthesise nanocrystals with nearly monodisperse size distribution in order to take full advantage of these novel materials.’

The flexibility provided by this approach opens possibilities for developing ‘greener,’ cheaper and simpler synthetic schemes for producing important high quality nanocrystals.