Methods of Forming Nanoparticles

Abstract

The present invention provides a method for preparing nanoparticles of group IV elements, particularly nanoparticles of Si, Ge and Sn, and binary and ternary alloys of these elements. The method comprises the solution-phase decomposition of one or more group IV metal precursors at elevated temperature and under an inert atmosphere at atmospheric pressure, using a decomposition-promoting reagent. A surface-bonding agent is added to the reaction mixture to form an organic layer surrounding the nanoparticles and prevent aggregation.

1 . A method of preparing nanoparticles of one or more group IV metals or alloys thereof comprising the steps of: reacting, under an inert atmosphere, at atmospheric pressure and with heating, one or more group IV metal precursors with a decomposition-promoting reagent in a liquid reaction medium comprising a high temperature surfactant; adding a surface-bonding agent; and recovering the nanoparticles. 
     
     
         2 . A method as claimed in  claim 1 , wherein the group IV metal is Si, Ge or Sn. 
     
     
         3 . A method as claimed in  claim 2 , wherein the group IV metal is Ge. 
     
     
         4 . A method as claimed in  claim 1 , wherein the group IV metal precursor comprises a compound of the general formula: G(Ar) x Y 4−x ; wherein G is the group IV metal, Ar is aryl, Y is halo and x takes a value that is at least 0 and no greater than 4; or a compound of the general formula: G(Ar) y Y 2−y  wherein G is the group IV metal, Ar is aryl, Y is halo and y takes a value that is at least 0 and no greater than 2. 
     
     
         5 . (canceled) 
     
     
         6 . A method as claimed in  claim 4 , wherein Ar is optionally substituted phenyl. 
     
     
         7 . A method as claimed in  claim 6 , wherein Ar is phenyl. 
     
     
         8 . A method as claimed in  claim 1 , wherein the liquid reaction medium further comprises a high temperature solvent. 
     
     
         9 . A method as claimed in  claim 1 , wherein the decomposition-promoting reagent is selected from one of:
 a) a strong reducing agent; or   b) S, Se, Te, P or As or a compound comprising one or more of these elements in a zero valence state.   
     
     
         10 . A method as claimed in claim,  1  wherein the decomposition-promoting reagent is selected from S, Se, Te, P or As or a compound comprising one or more of these elements in a zero valence state; or from S, Se or a compound comprising one or both of these elements in a zero valence state. 
     
     
         11 . (canceled) 
     
     
         12 . A method as claimed in  claim 1 , further comprising the step of adding a quenching agent prior to adding the surface-bonding agent. 
     
     
         13 . A method as claimed in  claim 12 , wherein the step of adding a quenching agent is prior to adding the surface-bonding agent but after adding the decomposition-promoting reagent. 
     
     
         14 . (canceled) 
     
     
         15 . A method as claimed in  claim 1 , wherein the step of reacting comprises heating to a temperature between about 100° C. and about 400° C.; or between about 200° C. and about 400° C.; or about 300° C. 
     
     
         16 .- 17 . (canceled) 
     
     
         18 . A method as claimed in  claim 1 , wherein said nanoparticles have a monodisperse nanoparticle size distribution such that the nanoparticle diameter has a standard deviation of less than 20% of the mean diameter; or less than 5% of the mean diameter. 
     
     
         19 . (canceled) 
     
     
         20 . A method as claimed in  claim 1 , wherein the nanoparticles produce luminescence in response to optical excitation with a quantum efficiency in excess of 1%; or in excess of 20%. 
     
     
         21 . (canceled) 
     
     
         22 . A method as claimed in  claim 1 , wherein the surface-bonding agent is a carboxylic acid, aldehyde, amide or alcohol. 
     
     
         23 . A method as claimed in  claim 22 , wherein the surface-bonding agent is a carboxylic acid. 
     
     
         24 . A method as claimed in  claim 1 , wherein the surface-bonding agent comprises an alkenyl or alkynyl moiety. 
     
     
         25 . A method as claimed in  claim 1 , wherein the surface-bonding agent comprises a compound of the formula R—N, wherein R is alkyl, alkenyl or aryl and N is a functional group capable of bonding to the surface of the nanoparticles. 
     
     
         26 . A method as claimed in  claim 1 , further comprising reacting the nanoparticles with a hydride reducing agent in the absence of water and oxygen, to provide hydrogen-terminated nanoparticles. 
     
     
         27 . A method as claimed in  claim 26 , further comprising reacting the hydrogen-terminated nanoparticles with a compound of the formula L-R—N; wherein R represents an alkyl or aryl group, L is a group having the desired functionality and N is a functional group capable of bonding to the hydrogen-terminated nanoparticle surface; to provide chemically functionalised nanoparticles. 
     
     
         28 .- 35 . (canceled)