Patent ID: 8491768

Claim:
A method, comprising: providing a colloid that includes i) a first fluid, ii) unwanted matter, and iii) quantum dots that are dispersed in the first fluid, wherein the quantum dots have at least one characteristic dimension between 1 and 1000 nanometers, the quantum dots having electrical charge arising from being part of the colloid; applying, to at least a portion of the colloid, an electric field that is substantially spatially uniform over a distance that is at least equal to said characteristic dimension, so that at least some of the quantum dots move towards a collection surface as a result of the force arising between their electrical charge and the electric field, whereupon quantum dots are collected on the collection surface; separating the collection surface having quantum dots thereon and the first fluid from each other; and dispersing quantum dots on the collection surface into a second fluid, wherein the concentration of the unwanted matter in the second fluid is less than the concentration of the unwanted matter in the first fluid.