US Patent 7449237 - Quantum dot microspheres

http://www.freepatentsonline.com/7449237.html

This patent from M.I.T. teaches microspheres having quantum dots formed in the peripheral surface which provide a luminous biotag having chemical and light stability. Claim 1 reads:

1. A microsphere comprising:

a central region including a first inorganic material; and

a peripheral region on a surface of the central region, the peripheral region including a second inorganic material and a semiconductor nanocrystal incorporated in the second inorganic material and covalently linked to the second inorganic material.