Semiconductor nanocrystals
A method of making a nanocrystal includes slowly infusing a M-containing compound and a X donor into a mixture including a nanocrystal core, thereby forming an overcoating including M and X on the core.
1. A method of making a nanocrystal comprising:
heating a mixture including a nanocrystal core to between 200° C. and 350° C.; and
while maintaining a constant temperature between 200° C. and 350° C., infusing a calculated amount of a non-organometallic M-containing compound and a X donor together into the mixture including the nanocrystal core, wherein the X donor is an alkyl thiol, at a rate of between 0.03 ml/minute and 0.07 ml/minute, thereby forming an overcoating including M and X on the core.
2. The method of claim 1 , wherein the M-containing compound is a metal salt.
3. The method of claim 2 , wherein the metal salt is a cadmium salt.
4. The method of claim 1 , wherein the X donor is a C 6 to C 18 alkyl thiol.
5. The method of claim 1 , wherein the infusion occurs over a period of 1 minute or longer.
6. The method of claim 5 , wherein the infusion occurs over a period of 10 minutes or longer.
7. The method of claim 6 , wherein the infusion occurs over a period of 30 minutes or longer.
8. The method of claim 1 , wherein infusing occurs continuously.
9. The method of claim 1 , wherein contacting the M-containing compound and the X donor with the nanocrystal core at a slow rate of infusion with a syringe pump.
10. The method of claim 1 , wherein the overcoated nanocrystal photoluminesces with a quantum yield of at least 90% at room temperature.
11. The method of claim 10 , wherein the overcoated nanocrystal photoluminesces with a quantum yield of at least 97% at room temperature.
12. The method of claim 1 , further comprising exposing the overcoated nanocrystal to an organic compound having affinity for a surface of the overcoated nanocrystal.
13. The method of claim 1 , wherein the nanocrystal core includes CdSe.
14. The method of claim 1 , wherein the overcoating includes CdS.
15. The method of claim 1 , wherein the nanocrystal core is a member of a substantially monodisperse population of nanocrystal cores.
16. The method of claim 1 , wherein the overcoated nanocrystal is a member of a substantially monodisperse population of overcoated nanocrystals.
17. The method of claim 16 , wherein the population emits light in a spectral range of no greater than about 34 nm full width at half max (FWHM).
18. The method of claim 17 , wherein the population exhibits less than a 10% rms deviation in diameter of the overcoated nanocrystal.
19. The method of claim 18 , wherein the population exhibits less than a 5% rms deviation in diameter of the overcoated nanocrystal.