Water based colorants comprising semiconductor nanocrystals and methods of making and using the same

1. A water-based colorant comprising: an emulsion comprising a plurality of droplets dispersed in an aqueous phase wherein the droplets comprise semiconductor nanocrystals dispersed in a hydrophobic liquid to form a hydrophobic phase and the aqueous phase comprises a plurality of polymers dispersed in water, wherein the plurality of polymers have hydrophilic functional groups that interact with the aqueous phase and hydrophobic moieties that interact with the hydrophobic phase and are chosen from the group consisting of:

polyvinyl acetate polymer, polyvinyl alcohol polymer, and polyacrylic acid polymer or an ester thereof.

2. The water-based colorant of claim 1 , wherein the colorant is a paint, ink or dye.

3. The water-based colorant of claim 1 , wherein the semiconductor nanocrystals are group II-VI, III-V, IV-VI, or I-III-VI binary, ternary, or quaternary semiconductor nanocrystals which emit in the UV, visible, or infrared range.

4. The water-based colorant of claim 1 which can be detected after 30 days of exposure to sunlight.

5. The water-based colorant of claim 1 which can be detected after 90 days of exposure to sunlight.

6. A method of making the colorant of claim 1 , comprising the steps of:

dispersing semiconductor nanocrystals in a hydrophobic solvent to form a dispersion;

adding the dispersion to a mixture of water and a polymer;

subjecting the mixture to an emulsifying process to form an emulsion; and

mixing the emulsion with another water-based colorant, the other water-based colorant being chosen from the group consisting of: a paint, an ink, and a dye.

7. The method of claim 6 , wherein the emulsifying process is sonication or high shear mixing.

8. A method of using the colorant of claim 1 , comprising: applying the colorant to a substrate.

9. The method of claim 8 , wherein the substrate is an article of clothing, or other object in need of detection.