A 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 semiconductors, metals, metal oxides and combinations thereof,
• wherein the semiconductors are selected from the group consisting of CdSe, ZnSe, InP, Zn3P2, InSe, C-dot, CsPbX3 (wherein X is Br, I, or Cl), and combinations thereof,
• wherein the metals are selected from the group consisting of Ag, Au, Pt, Pd, and combinations thereof, and
• wherein the metal oxides are selected from the group consisting of CeO2, ZnO, TiO2, SiO2, and combinations 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 combinations 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;
• a) introducing terminating ligands selected from the group consisting of fatty acids, long chain amine and phosphine oxides, and combinations thereof, to the reaction mixture to stop the growth of the metal oxide shell.