Semiconductor nanocrystals, or “quantum dots,” are another of nanotech’s “miracle molecules” whose quantum properties promise a wide range of applications across several industrial sectors.
Why Are Quantum Dots Important?
Companies are exploiting the unique optical effects that occur when semiconductor nanomaterials change size - as the particles are reduced in size, they emit distinctly different colors. The particles can be attached to or incorporated in materials, including biological materials, to act as a kind of barcode or tracking device. One project underway aims to incorporate quantum dots in inks or polymers used in the manufacture of paper money as a way to combat counterfeiting. Currently, quantum dots are used for labeling live biological material in vitro and in vivo in animals (other than humans) for research purposes - they can be injected into cells or attached to proteins in order to track, label or identify specific biomolecules.
Using Quantum Dots in Medical Applications
In January 2004, Carnegie Mellon University researchers - collaborating with scientists from Quantum Dot Corporation (QDC) - announced that quantum dots injected in animals circulated in the blood for hours and continued emitting their distinctive colors for eight months. (Once they stopped circulating, the nanocrystals collected in the liver, spleen, lymph nodes and bone marrow, suggesting that the particles were picked up by immune cells whose job it is to sweep up circulating debris.) The hope is that one day quantum dots will be used in humans to treat and monitor diseases such as cancer.
The Question Regarding the Possible Toxicity of Quantum Dots
Researchers will have to proceed with caution because the core material in most semiconductor nanocrystals is highly toxic cadmium and “formal or systematic studies” to determine toxicity of quantum dots have not been conducted. Comprehensive toxicological data on quantum dots are crucial and will determine the likelihood of extensive in vivo applications in humans.