Synthesis of highly luminescent colloidal particles

A composition comprising a nanocrystal aggregate and at least one affinity molecule;

• wherein:
• the aggregate comprises two or more coated nanocrystals;
• the nanocrystals comprise a coating layer comprising one or more imidazole groups;
• the nanocrystals interact through the coating layer to form the aggregate;
• the aggregate comprises at least one functional group on its surface;
• and
• the at least one affinity molecule is linked to the functional group.

A composition comprising two to about twenty aggregated fluorescent semiconductor nanocrystals;

• wherein:
• the fluorescent nanocrystals comprise a coating layer;
• the coating layer comprises one or more imidazole groups;
• and
• the nanocrystals interact through their coating layers to form an aggregate, the aggregate being composed of from about two to about twenty fluorescent semiconductor nanocystals.

A method of detecting a target molecule in a sample, the method comprising:

• providing a sample suspected of containing a target molecule;
• providing one or more coated nanocrystal aggregates, said coated nanocrystal aggregates comprising a nanocrystal, an imidazole containing coating, and an affinity ligand having binding specificity for the target molecule;
• contacting the sample and the aggregates to form a treated sample, wherein the aggregates form a complex with the target molecule;
• exciting the complex with a wavelength of energy to form an excited complex;
• and detecting the excited complex.