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Materials researchers at the National Institute of Standards and Technology (NIST) have developed a simplified, low-cost process for producing high-quality, water-soluble "quantum dots" for biological research. By using a laboratory microwave reactor to promote the synthesis of the widely used nanomaterials, the recently published* NIST process avoids a problematic step in the conventional approach to making quantum dots, resulting in brighter, more stable dots.

Quantum dots are specially engineered nanoscale crystals of semiconductor compounds. The name comes from the fact that their infinitesimal size enables a quantum electronics effect that causes the crystals to fluoresce brilliantly at specific, sharply defined colors. Bright, stable, tiny and tunable across a broad spectrum of colors, quantum dots that are engineered to attach themselves to particular proteins have become a popular research tool in areas such as cancer research for detecting, labeling and tracking specific biomarkers and cells.

Making good quantum dots for biological research is complex. First a semiconductor compoundtypically a mixture of cadmium and seleniummust be induced to crystallize into discrete nanocrystals of just the right size. Cadmium is toxic, and the compound also can oxidize easily (ruining the effect), so the nanocrystals must be encapsulated in a protective shell such as zinc sulfide. To make them water soluble for biological applications, a short organic molecule called a "ligand" is attached to the zinc atoms. The organic ligand also serves as a tether to attach additional functional molecules that cause the dot to bind to specific proteins.

The accepted commercial method uses a high-temperature reaction (about 300 degrees Celsius) that must be carefully controlled under an inert gas atmosphere for the crystallization and encapsulation stages. An intermediate ligand material that can tolerate the high temperature is used to promote the c
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