Surface structures for enhancement of quantum yield in broad spectrum emission nanocrystals

Abstract

Disclosed are inorganic nanoparticles comprising a body comprising cadmium and/or zinc crystallized with selenium, sulfur, and/or tellurium; a multiplicity of phosphonic acid ligands comprising at least about 20% of the total surface ligand coverage; wherein the nanocrystal is capable of absorbing energy from a first electromagnetic region and capable of emitting light in a second electromagnetic region, wherein the maximum absorbance wavelength of the first electromagnetic region is different from the maximum emission wavelength of the second electromagnetic region, thereby providing a Stokes shift of at least about 20 nm, wherein the second electromagnetic region comprises an at least about 100 nm wide band of wavelengths, and wherein the nanoparticle exhibits has a quantum yield of at least about 10%. This abstract is intended as a scanning tool for purposes of searching in the particular art and is not intended to be limiting of the present invention.

1 . An inorganic nanoparticle comprising:
 a. a body comprising Cd and/or Zn crystallized with selenium, sulfur, and/or tellurium;   b. a surface covered with a multiplicity of surface ligands, wherein phosphonic acid ligands comprise at least about 20% of the total surface ligand coverage; and   c. a diameter of less than about 3.0 nm,   wherein the nanocrystal is capable of absorbing energy from a first electromagnetic region and capable of emitting light in a second electromagnetic region,   wherein the maximum absorbance wavelength of the first electromagnetic region is different from the maximum emission wavelength of the second electromagnetic region, thereby providing a Stokes shift of at least about 20 nm,   wherein the second electromagnetic region comprises an at least about 100 nm wide (FWHH) band of wavelengths, and   wherein the nanoparticle exhibits has a quantum yield of at least about 10%.   
     
     
         2 . The nanoparticle of  claim 1 , wherein the second emission electromagnetic region comprises wavelengths of from about 420 nm to about 710 nm. 
     
     
         3 . The nanoparticle of  claim 1 , wherein the first electromagnetic region comprises light with a wavelength of less than about 450 nm. 
     
     
         4 . The nanoparticle of  claim 1 , wherein the first electromagnetic region comprises light with a wavelength of about 414 nm. 
     
     
         5 . The nanoparticle of  claim 1 , wherein the nanoparticle comprises at least one of cadmium selenide, cadmium sulfide, or cadmium telluride, or a mixture thereof. 
     
     
         6 . The nanoparticle of  claim 1 , wherein the nanoparticle comprises at least one of zinc sulfide, zinc selenide, zinc telluride, magnesium sulfide, magnesium selenide, magnesium telluride, or a mixture thereof. 
     
     
         7 . The nanoparticle of  claim 1 , further comprising an optically transparent inorganic shell at the surface of the nanoparticle. 
     
     
         8 . The nanoparticle of  claim 7 , wherein the optically transparent inorganic shell comprises zinc sulfide or magnesium sulfide. 
     
     
         9 . The nanoparticle of  claim 1 , further comprising an organic ligand coating at the surface of the nanoparticle. 
     
     
         10 . The nanoparticle of  claim 9 , wherein the organic ligand coating comprises at least one of a hexadecylamine residue, a dodecylphosphonic acid residue, a tri-n-butylphosphine residue, a tri-n-octylphosphine oxide residue, or a mixture thereof. 
     
     
         11 . The nanoparticle of  claim 1 , wherein the nanoparticle was not produced by an etching process. 
     
     
         12 . A method of preparing an inorganic nanoparticle comprising the steps of:
 a. heating to a temperature of greater than about 300° C. a reaction mixture comprising a C 4  to C 22  alkyl- or aryl-phosphonic acid and a source of cadmium or zinc in a molar ratio of from about 1:5 to about 1:1 Cd/Zn:phosphonic acid;   b. adding to the reaction mixture an injection mixture comprising a C 2  to C 16  trialkyl- or triarylphosphine and a source of selenium, sulfur, or tellurium; and   c. decreasing the temperature of the reaction mixture to less than about 300° C.   
     
     
         13 . The method of  claim 12 , wherein the injection mixture further comprises a C 6  to C 24  hydrocarbon, provided in a ratio in the injection solution of less than about 90:10 to the C 2  to C 16  trialkyl- or triarylphosphine. 
     
     
         14 . The method of  claim 13 , wherein the C 6  to C 24  hydrocarbon is octadecene. 
     
     
         15 . The method of  claim 13 , wherein the C 2  to C 16  trialkyl- or triarylphosphine is tri-n-butylphosphine. 
     
     
         16 . The method of  claim 12 , wherein the inorganic nanoparticle prepared has a quantum yield of at least about 10%. 
     
     
         17 . The method of  claim 12 , further comprising the step of adding a solvent to the reaction mixture so as to decrease the temperature of the reaction mixture to less than about 250° C. 
     
     
         18 . The method of  claim 12 , wherein the source of cadmium or zinc comprises cadmium oxide. 
     
     
         19 . The method of  claim 12 , wherein the source of cadmium or zinc comprises zinc oxide. 
     
     
         20 . The method of  claim 12 , wherein the source of selenium, sulfur, or tellurium comprises selenium powder.