Method for producing an oxide shell around nanocrystals

A colloidal atomic layer deposition (c-ALD) method for producing core-shell nanocrystals consisting of a metal-containing nanocrystal core and a shell layer comprising at least one metal oxide material, the method comprising:

• a) providing metal-containing nanocrystal cores selected from the group consisting of a semiconductor, a metal, a metal oxide, and a combination thereof,
• wherein the semiconductor is selected from the group consisting of CdSe, ZnSe, InP, Zn3P2, InSe, CsPbX3 (wherein X is Br, I, or Cl), and a combination thereof,
• wherein the metal is selected from the group consisting of Ag, Au, Pt, Pd, and a combination thereof, and
• wherein the metal oxide is selected from the group consisting of CeO2, ZnO, TiO2, SiO2, and a combination thereof,
• b) dispersing metal-containing nanocrystal cores in an organic solvent under inert gas to provide a reaction mixture and maintaining the reaction mixture under inert gas atmosphere,
• c) introducing one or more highly reactive organometallic compounds to the reaction mixture, wherein the one or more highly reactive organometallic compounds are able to produce volatile secondary products during the reaction and are selected from the group consisting of trimethyl aluminum, dimethylzinc, tetrakis(dimethylamido)titanium(IV), trymethylindium, trymethylgallium, and a combination thereof,
• d) waiting for sufficient time to allow reaction and then deposition of the one or more highly reactive organometallic compounds on the surface of the metal-containing nanocrystal cores,
• e) introducing the pure oxygen to the reaction mixture,
• f) waiting for sufficient time to obtain formation of a metal oxide layer on the surface of the metal-containing nanocrystal cores and thereby growth of a metal oxide shell on the surface of the metal-containing nanocrystal cores,
• g) sequentially repeating steps c) to f) until an optimal thickness of the metal oxide shell is obtained on the surface of the metal-containing nanocrystal cores;
• h) introducing terminating ligands selected from the group consisting of a fatty acid, a C12-C18 long chain amine and a phosphine oxide, and a combination thereof, to the reaction mixture to stop the growth of the metal oxide shell.