Green/red purity vs. total intensity, observed in the various lanthanide ion combinations.
The Molecular Foundry's Delia Milliron and colleagues have employed a powerful combinatorial approach to synthesize nanocrystals that glow in bright, pure colors when excited with near infrared light. – a process known as upconversion. These nanocrystals may allow for biological imaging with less harmful radiation than current methods, and can be more easily tracked and quantified due to their single color emission.
Milliron's team used a wide-sweeping approach to identify promising lanthanide ion combinations, using the automatic synthesis robot, WANDA, able to perform 96 different reactions in parallel. Ultimately four combinations of different ions were identified which responded to IR radiation by emission of pure red and pure green light.
The wealth of data acquired from the roughly 300 reactions performed was then used to develop a theoretical model which accurately predicts the color and purity of the upconverted light emitted by any combinations of ions.