Multi-Layer-Coated Quantum Dot Beads

Abstract

Coated beads made of a primary matrix material and containing a population of quantum dot nanoparticles. Each bead has a multi-layer surface coating. The layers can be two or more distinct surface coating materials. The surface coating materials may be inorganic materials and/or polymeric materials. A method of preparing such particles is also described. The coated beads are useful for composite materials for applications such as light-emitting devices.

What is claimed is: 
     
         1 . A process for making coated quantum dot beads, the process comprising:
 providing a powder comprising a plurality of beads, wherein each bead comprises: a primary matrix material, and a population of quantum dot nanoparticles incorporated into the primary matrix material; and   agitating the powder while repeatedly exposing the powder to atomic layer deposition (ALD) precursors.   
     
     
         2 . The process recited in  claim 1 , wherein exposing the powder to ALD precursors comprises exposing the powder to pulses of reactant gas comprising the ALD precursors. 
     
     
         3 . The process recited in  claim 2 , wherein agitating the powder comprises exposing the powder to pulses of inert gas. 
     
     
         4 . The process recited in  claim 3 , wherein the powder is simultaneously exposed to pulses of reactant gas and pulses of inert gas. 
     
     
         5 . The process recited in  claim 3 , wherein the powder is alternatingly exposed to pulses of reactant gas and pulses of inert gas. 
     
     
         6 . The process recited in  claim 5 , wherein the pulses of the inert gas have a flow rate between 300 and 6,000 sccm. 
     
     
         7 . The process recited in  claim 5 , wherein the pulses of the inert gas have a duration between 0.1 and 5 seconds. 
     
     
         8 . The process recited in  claim 3 , wherein exposing the powder to pulses of reactant gas comprises delivering the reactant gas into an ALD reaction chamber through a first set of gas lines and wherein exposing the powder to pulses of inert gas comprises delivering inert gas into the ALD reaction chamber through a different set of gas lines. 
     
     
         9 . The process recited in  claim 3 , wherein the reactant gas and the inert gas are delivered into an ALD reaction chamber using a same set of lines. 
     
     
         10 . The process recited in  claim 2 , wherein exposing the powder to pulses of reactant gas comprises exposing the powder to a first number of pulses of the reactant gas, mechanically disaggregating the powder, and then exposing the powder to a second number of pulses reactant gas. 
     
     
         11 . The process recited in  claim 10 , wherein the first number of pulses is between 1 and 500. 
     
     
         12 . The process recited in  claim 10 , wherein first number of pulses is between 10 and 40. 
     
     
         13 . The process recited in  claim 1 , wherein the quantum dot nanoparticles are semiconductor nanoparticles. 
     
     
         14 . The process recited in  claim 1 , wherein the quantum dot nanoparticles comprise indium and phosphorus. 
     
     
         15 . The process recited in  claim 1 , wherein the quantum dot nanoparticles are essentially free of cadmium. 
     
     
         16 . The process recited in  claim 1 , wherein the primary matrix material is silica, a resin, a polymer, a monolith, a glass, a sol-gel, an epoxy, a silicone, or a (meth)acrylate. 
     
     
         17 . The process recited in  claim 1 , wherein the primary matrix material comprises silica and the bead surfaces have been treated with an acrylate monomer and subsequently polymerized to provide a polymeric surface barrier layer. 
     
     
         18 . The process recited in  claim 1 , wherein each bead comprises about 1000 to about 10,000 quantum dot nanoparticles. 
     
     
         19 . The process recited in  claim 1 , wherein each bead comprises about 10,000 to about 100,000 quantum dot nanoparticles. 
     
     
         20 . The process recited in  claim 12 , wherein the ALD precursors comprise one or more of trimethylaluminum (TMA), ethylene glycol (EG) and water (H 2 O).