Cadmium-free quantum dots, tunable quantum dots, quantum dot containing polymer, articles, films, and 3d structure containing them and methods of making and using them

Abstract

Quantum dots that are cadmium-free and/or stoichiometrically tuned are disclosed, as are methods of making them. Inclusion of the quantum dots and others in a stabilizing polymer matrix is also disclosed. The polymers are chosen for their strong binding affinity to the outer layers of the quantum dots such that the bond dissociation energy between the polymer material and the quantum dot is greater than the energy required to reach the melt temperature of the cross-linked polymer.

1 . A method for synthesizing II-VI-VI semiconductor nanocrystals (SCNs) of the formula WY x Z (1−x)  having a predetermined emission wavelength, wherein W is a Group II element, Y and Z are different Group VI elements, and 0<X<1, comprising:
 heating a II-VI-VI SCN precursor solution to a temperature sufficient to produce the II-VI-VI SCNs, wherein the II-VI-VI SCN precursor solution comprises a Group II element, a first Group VI element, a second Group VI element, and a pH controller in one or more solvents together comprising one or more C 12  to C 20  hydrocarbons and one or more fatty acids; and   wherein the amount of pH controller is adjusted to provide the predetermined emission wavelength from the SCNs.   
     
     
         2 . The method according to  claim 1 , wherein the Group II element is one or more selected from Cd, Zn and Hg. 
     
     
         3 . The method according to  claim 1 , wherein each of the first Group VI element and the second Group VI element is one or more selected from S, Se, Te, Po, and O. 
     
     
         4 . The method according to  claim 1 , wherein the C 12  to C 20  hydrocarbons are one or more selected from hexadecene, octadecene, eicosene, hexadecane, octadecane and Icosane. 
     
     
         5 . The method according to  claim 1 , wherein the fatty acids are one or more selected from myristoleic acid, palmitoleic acid, sapienic acid, oleic acid, elaidic acid, vaccenic acid, linoleic acid, linoelaidic acid, α-Linolenic acid, arachidonic acid, eicosapentaenoic acid, erucic acid, docosahexaenoic acid, stearic acid, palmitic acid, and arachidic acid. 
     
     
         6 . The method according to  claim 1 , wherein the pH controller is an oxide or carboxylic acid salt of a Group II element. 
     
     
         7 . The method according to  claim 1 , wherein pH controller is selected from zinc salts of acetic acid, citric acid, lactic acid, propionic acid, butyric acid, tartaric acid, and valeric acid. 
     
     
         8 . The method according to  claim 1 , wherein the II-VI-VI SCN precursor solution is prepared by: dissolving the Group II element, the first Group VI element, and the second Group VI element in a solvent comprising the pH controller, octadecene and a fatty acid to provide the II-VI-VI SCN precursor solution. 
     
     
         9 . The method according to  claim 1 , wherein the II-VI-VI SCN precursor is prepared by preparing a first solution by dissolving the Group II element and the first Group VI element in a first solvent comprising octadecene and a fatty acid; preparing a second solution by dissolving the second Group VI element in a second solvent comprising octadecene; mixing the first and second solutions to provide a II-VI-VI SCN precursor solution;
 adding the pH controller to one or both of the first and second.   
     
     
         10 . The method according to  claim 1 , wherein the II-VI-VI SCN precursor solution is prepared by:
 preparing a first solution by dissolving a Group II element in a first solvent comprising octadecene and a fatty acid;   preparing a second solution by dissolving a first Group VI and a second Group VI element in a second solvent comprising octadecene;   adding the pH controller to one or both of the first and second solutions; and   mixing said first and second solutions to provide a II-VI-VI SCN precursor solution.   
     
     
         11 . The method according to  claim 1 , wherein the II-VI-VI SCN precursor is prepared by:
 preparing a first solution by dissolving a Group II element in a first solvent comprising octadecene and a fatty acid;   preparing a second solution by dissolving a first Group VI element in a second solvent comprising octadecene;   preparing a third solution by dissolving a second Group VI element in a third solvent comprising tributylphosphine;   adding the pH controller to one or more of the first, second, or third solutions; and   mixing the first, second, and third solutions to provide a II-VI-VI SCN precursor solution.   
     
     
         12 . The method according to  claim 1 , wherein said fatty acid is oleic acid. 
     
     
         13 . The method according to g  claim 1 , wherein the temperature is between about 270° C. and 330° C. 
     
     
         14 . II-VI-VI semiconductor nanocrystals made according to the method of  claim 1 . 
     
     
         15 . A II-VI-VI semiconductor nanocrystal comprising Cd, S and Se, where in the nanocrystal has been modified by a zinc alkylcarboxylate pH controller. 
     
     
         16 . A method of tuning a II-VI-VI semiconductor nanocrystal of known emission wavelength, the method comprising:
 providing a II-VI-VI semiconductor nanocrystal having a known emission wavelength;   heating the II-VI-VI semiconductor nanocrystal in a solution comprising a pH controller, one or more C 12  to C 20  hydrocarbons and one or more fatty acids to form an SCN solution;   adding a solution comprising dialkyl zinc, hexaalkyldisilathiane and trialkylphosphine; and   heating to a temperature sufficient to produce a capped II-VI-VI semiconductor nanocrystal;   wherein the amount of pH controller is adjusted to provide a predetermined emission wavelength shift from the known emission wavelength of the II-VI-VI semiconductor nanocrystal.   
     
     
         17 . The method according to  claim 16 , wherein the C 12  to C 20  hydrocarbons are one or more selected from hexadecene, octadecene, eicosene, hexadecane, octadecane and Icosane. 
     
     
         18 . The method according to  claim 16 , wherein the fatty acids are one or more selected from myristoleic acid, palmitoleic acid, sapienic acid, oleic acid, elaidic acid, vaccenic acid, linoleic acid, linoelaidic acid, α-Linolenic acid, arachidonic acid, eicosapentaenoic acid, erucic acid, docosahexaenoic acid, stearic acid, palmitic acid, and arachidic acid. 
     
     
         19 . The method according to  claim 16 , wherein the pH controller is an oxide or carboxylic acid salt of a Group II element. 
     
     
         20 . The method according to  claim 16 , wherein pH controller is selected from zinc salts of acetic acid, citric acid, lactic acid, propionic acid, butyric acid, tartaric acid, and valeric acid. 
     
     
         21 . The method according to  claim 16 , wherein the dialkyl zinc is dimethyl zinc, the hexaalkyldisilathiane is hexamethyldisilathiane and the trialkylphosphine is trioctylphosphine, 
     
     
         22 . The method according to  claim 16 , wherein the temperature is between about 150° C. and 350° C. 
     
     
         23 . A tuned II-VI-VI semiconductor nanocrystal made according to  claim 16 . 
     
     
         24 . A capped II-VI-VI semiconductor nanocrystal comprising:
 a core comprising a II-VI-VI semiconductor nanocrystal comprising Cd, S and Se, wherein the nanocrystal has been modified by a zinc alkylcarboxylate; and   a cap layer selected from the group consisting of a layer comprising ZnS, a layer comprising Al 2 O 3 , and a multi-layer cap comprising a first layer comprising ZnS and a second layer comprising Al 2 O 3 .   
     
     
         25 . A cadmium free “Cd-free” semiconductor nanocrystal comprising one or more group II elements, one or more group III elements, and one or more group VI elements, wherein the semiconductor nanocrystal is substantially free of cadmium. 
     
     
         26 . The Cd-free semiconductor nanocrystal according to  claim 25 , wherein the semiconductor nanocrystal does not contain cadmium. 
     
     
         27 . The Cd-free nanocrystal according  claim 25 , wherein the Cd-free nanocrystal have an emission wavelength in the near ultraviolet to far infrared range. 
     
     
         28 . A method for synthesizing Cd-free semiconductor nanocrystals comprising:
 heating a precursor solution comprising one or more non-cadmium Group II elements, one or more Group III elements and one or more Group VI elements in one or more solvents together comprising one or more C 12  to C 20  hydrocarbons, one or more fatty acids and optionally one or more C 1  to C 22  alkyl thiols to a temperature sufficient to produce the Cd-free semiconductor nanocrystals.   
     
     
         29 . The method according to  claim 28 , wherein the Group II elements are one or more selected from Cu, Zn and Hg. 
     
     
         30 . The method according to  claim 28 , wherein the Group III elements are one or more selected from In, Ga, Al, and Tl. 
     
     
         31 . The method according  claim 28 , wherein the Group VI elements are one or more selected from S, Se, Te, Po, and O. 
     
     
         32 . The method according to  claim 28 , wherein the C 12  to C 20  hydrocarbons are one or more selected from hexadecene, octadecene, eicosene, hexadecane, octadecane and Icosane. 
     
     
         33 . The method according to  claim 28 , wherein the fatty acids are one or more selected from myristoleic acid, palmitoleic acid, sapienic acid, oleic acid, elaidic acid, vaccenic acid, linoleic acid, linoelaidic acid, α-Linolenic acid, arachidonic acid, eicosapentaenoic acid, erucic acid, docosahexaenoic acid, stearic acid, palmitic acid, and arachidic acid. 
     
     
         34 . The method according to  claim 28 , wherein the fatty acid is oleic acid. 
     
     
         35 . The method according to  claim 28 , wherein the temperature is between about 270° C. and 330° C. 
     
     
         36 . A Cd-free semiconductor nanocrystals made according to the method of  claim 28 . 
     
     
         37 . A Cd-free semiconductor nanocrystal according to  claim 1  that has been modified by a zinc alkylcarboxylate. 
     
     
         38 . A method of capping a Cd-free semiconductor nanocrystal comprising:
 providing a Cd-free semiconductor nanocrystal according to  claim 25 ;   heating the Cd-free semiconductor nanocrystal in a solution comprising one or more C 12  to C 20  hydrocarbons and one or more fatty acids to form an SCN solution;   adding a solution comprising dialkyl zinc, hexaalkyldisilathiane and trialkylphosphine; and   heating to a temperature sufficient to produce a capped Cd-free semiconductor nanocrystal.   
     
     
         39 . The method according to  claim 38 , wherein the C 12  to C 20  hydrocarbons are one or more selected from hexadecene, octadecene, eicosene, hexadecane, octadecane and Icosane. 
     
     
         40 . The method according to  claim 38 , wherein the fatty acids are one or more selected from myristoleic acid, palmitoleic acid, sapienic acid, oleic acid, elaidic acid, vaccenic acid, linoleic acid, linoelaidic acid, α-Linolenic acid, arachidonic acid, eicosapentaenoic acid, erucic acid, docosahexaenoic acid, stearic acid, palmitic acid, and arachidic acid. 
     
     
         41 . The method according  claim 38 , wherein the dialkyl zinc is dimethyl zinc, the hexaalkyldisilathiane is hexamethyldisilathiane and the trialkylphosphine is trioctylphosphine. 
     
     
         42 . The method according to  claim 38 , wherein the temperature is between about 150° C. and 350° C. 
     
     
         43 . A capped Cd-free semiconductor nanocrystal made according to the method of  claim 38 . 
     
     
         44 . A capped Cd-free semiconductor nanocrystal comprising:
 a core comprising a Cd-free semiconductor nanocrystal comprising a core of one or more group II elements, one or more group III elements, and one or more group VI elements, wherein the semiconductor nanocrystal is substantially free of cadmium, wherein the nanocrystal has been modified by a zinc alkylcarboxylate;   a cap layer selected from the group consisting of a layer comprising ZnS; and   a layer comprising Al 2 O 3 .   
     
     
         45 . A quantum dot-containing polymer resin comprising:
 a plurality of quantum dots, each having an outermost layer;   a polymer material cross-linked to the outermost layer such that the bond dissociation energy between the polymer material and the outermost layer is greater than the energy required to reach the melt temperature of the cross-linked polymer.   
     
     
         46 . The quantum dot-containing polymer resin of  claim 45 , wherein the plurality of quantum dots are selected from core-shell quantum dots, Cd-free quantum dots, or stoichiometrically tuned quantum dots. 
     
     
         47 . The quantum dot-containing polymer of  claim 46 , wherein the outermost layer is selected from a capping layer and a passivation layer. 
     
     
         48 . The quantum dot-containing polymer of  claim 46 , wherein the outermost layer is a Zns capping layer. 
     
     
         49 . The quantum dot-containing polymer of  claim 46 , wherein the outermost layer is an Al2O3 passivation layer. 
     
     
         50 . The quantum dot-containing polymer of  claim 46 , wherein the polymer material is an acrylate resin comprising:
 units derived from polymerizing one or monomers according to the formula:   
       
         
           
           
               
               
           
         
       
       wherein R 1  is hydrogen or methyl and R 2  is selected from the group consisting of methyl; ethyl; propyl; isopropyl; butyl; isobutyl; pentyl; cyclopentyl; isopentyl; linear, branched and cyclic hexyl; linear, branched and cyclic heptyl; and linear branched and cyclic octyl. 
     
     
         51 . The quantum dot-containing polymer of  claim 49 , wherein the acrylate resin further comprises units derived from polymerizing one or monomers according to the formula: 
       
         
           
           
               
               
           
         
         wherein each of R 3  and R 4  are independently selected from the group consisting of methyl; ethyl; propyl; isopropyl; butyl; isobutyl; pentyl; cyclopentyl; isopentyl; C 6  to C 12  linear, branched, cyclic and aromatic hydrocarbyl, and polyethylene glycol; and 
         wherein R 5  is selected from the group consisting of hydrogen, methyl; ethyl; propyl; isopropyl; butyl; isobutyl; pentyl; cyclopentyl; isopentyl; C 6  to C 12  linear, branched, cyclic and aromatic hydrocarbyl, and polyethylene glycol. 
       
     
     
         52 . A quantum dot containing polymer resin comprising:
 a plurality of quantum dots each having an Al 2 O 3  passivation layer;   a polymer material cross-linked to the Al 2 O 3  passivation layer,   
       wherein the bond dissociation energy between the polymer material and the Al 2 O 3  is greater than the energy required to reach the melt temperature of the cross-linked polymer. 
     
     
         53 . A quantum dot-containing polymer resin comprising:
 a homogenous plurality of multi-color, same-sized alloy-gradient quantum dots each having a ZnS capping layer and an Al 2 O 3  passivation layer;   a polymer material cross-linked to the Al 2 O 3  passivation layer,   
       wherein the bond dissociation energy between the polymer material and the Al 2 O 3  is greater than the energy required to reach the melt temperature of the cross-linked polymer. 
     
     
         54 . A quantum dot containing polymer resin comprising:
 a plurality of quantum dots each having a ZnS capping layer and an Al 2 O 3  passivation layer;   a polymer material cross-linked to the Al 2 O 3  passivation layer,   
       wherein the bond dissociation energy between the polymer material and the Al 2 O 3  is greater than the energy required to reach the melt temperature of the cross-linked polymer. 
     
     
         55 . An article comprising:
 at least one of a film, a multi-layer film, or a 3D object comprising a quantum dot-containing polymer, wherein polymer is bound to the quantum-dot such that the bond dissociation energy between the polymer material and the quantum dot is greater than the energy required to reach the melt temperature of the cross-linked polymer.