Dispersion of bare nanoparticles in nonpolar solvents

Abstract

Methods are disclosed for dispersing nanoparticles in solvents, involving the use of a cationic species and an anionic species, where at least one of the ionic species is soluble in the nonpolar solvent and the other ionic species has a relatively strong affinity for the surface of the nanoparticles. The cationic species and the anionic species together form a cluster of ion pairs shielding the nanoparticles and enhancing their dispersibility in the nonpolar solvent.

What is claimed is: 
     
         1 . A stable dispersion of nanoparticles in the presence of anionic species and cationic species in a nonpolar solvent, wherein the anionic and cationic species are present in solvent stabilizing amounts, wherein the stabilizing amounts of the anionic species and the cationic species are such that the molar ratios of the anionic species and of the cationic species, respectively to the nanoparticles, are different, and wherein the anionic and cationic species together form ionic or hydrogen bonds therebetween in the dispersion, wherein a first one of the anionic or the cationic species has a higher relative affinity for the nanoparticles in the solvent, and the other of the anionic or cationic species has a greater relative solubility in the nonpolar solvent than the first ionic species; and
 wherein the anionic and cationic species are together capable of forming an ionic compound that is soluble in the non-polar solvent to provide the anionic and cationic species in the stabilizing amounts; and,   wherein the stable dispersion is non-precipitating under stabilized conditions for a stabilized period of time wherein, in the absence of the anionic and the cationic species, the nanoparticles would precipitate under the stabilized conditions within the stabilized period of time;   wherein the ionic compound is an ionic liquid at a temperature at which the dispersion is stabilized, or under the stabilized conditions; and,   wherein the ionic liquid is N-butylammonium oleate ([C4NH3][oleate]), N-octylammonium oleate ([C8NH3][oleate]), tri-ethylammonium oleate ([HN222][oleate]), tri-N-butylammonium oleate ([HN444][oleate]), tri-N-octylammonium oleate ([HN888][oleate]), N-octylammonium dodecylbenzenesulfonate ([C8NH3][DBS]), butylammonium dodecyl benzenesulfonate, tri-ethylammonium dodecyl benzenesulfonate, tri-N-butylammonium dodecyl benzenesulfonate, or tri-N-octylammonium dodecyl benzenesulfonate.   
     
     
         2 . The stable dispersion of nanoparticles of  claim 1 , wherein the ionic liquid is N-butylammonium oleate ([C4NH3][oleate]). 
     
     
         3 . The stable dispersion of nanoparticles of  claim 1 , wherein the ionic liquid is N-octylammonium oleate ([C8NH3][oleate]). 
     
     
         4 . The stable dispersion of nanoparticles of  claim 1 , wherein the ionic liquid is tri-ethylammonium oleate ([HN222][oleate]). 
     
     
         5 . The stable dispersion of nanoparticles of  claim 1 , wherein the ionic liquid is tri-N-butylammonium oleate ([HN444][oleate]). 
     
     
         6 . The stable dispersion of nanoparticles of  claim 1 , wherein the ionic liquid is tri-N-octylammonium oleate ([HN888][oleate]). 
     
     
         7 . The stable dispersion of nanoparticles of  claim 1 , wherein the ionic liquid is N-octylammonium dodecylbenzenesulfonate ([C8NH3][DBS]), butylammonium dodecyl benzenesulfonate, tri-ethylammonium dodecyl benzenesulfonate, tri-N-butylammonium dodecyl benzenesulfonate or tri-N-octylammonium dodecyl benzenesulfonate. 
     
     
         8 . The stable dispersion of nanoparticles of  claim 1 , wherein the nonpolar solvent has a dielectric constant of less than 15. 
     
     
         9 . The stable dispersion of nanoparticles of  claim 1 , wherein the stabilized conditions comprise an average or maximum gravitational force during the stabilized period of 1 gravity and an ambient temperature or a temperature above a freezing point or below a boiling point of the dispersion. 
     
     
         10 . The stable dispersion of nanoparticles of  claim 1 , wherein the nanoparticles comprise a nanoparticle that is comprised substantially of a metal, a metalloid, a metal oxide, a metalloid oxide, carbon, cellulose or a mixture thereof. 
     
     
         11 . The stable dispersion of nanoparticles of  claim 10 , wherein the metal or metalloid oxide comprises silicon oxide, iron oxide or aluminum oxide; the carbon comprises carbon black or carbon nanotubes; or, the cellulose comprises cellulose nanocrystals. 
     
     
         12 . The stable dispersion of nanoparticles of  claim 1 , wherein the nanoparticles comprise a nanoparticle comprising an element selected from the group consisting of Fe, Al, Ag, Au, Co, Mo, N, Ni, Pd, Pt, S, Sn, Si, Ti, W, or Zn. 
     
     
         13 . The stable dispersion of nanoparticles of  claim 1 , wherein the nanoparticles have an average dimension ranging from 1 nm to 100 nm. 
     
     
         14 . The stable dispersion of nanoparticles of  claim 1 , wherein the nanoparticles comprise a nanoparticle that has a charged particle surface in the dispersion. 
     
     
         15 . The stable dispersion of nanoparticles of  claim 14 , wherein the charged particle surface is positively charged. 
     
     
         16 . The stable dispersion of nanoparticles of  claim 14 , wherein the charged particle surface is negatively charged. 
     
     
         17 . The stable dispersion of nanoparticles of  claim 1 , wherein the nanoparticles comprise a nanoparticle that does not have a charged particle surface in the dispersion. 
     
     
         18 . The stable dispersion of nanoparticles of  claim 1 , wherein the stabilization period is 1 day, 1 week, 1 month or 1 year. 
     
     
         19 . The stable dispersion of nanoparticles of  claim 1 , wherein the nanoparticles are present in the dispersion in an amount ranging from 0.001 wt. % to 50 wt. % relative to the dispersion weight. 
     
     
         20 . The stable dispersion of nanoparticles of  claim 1 , wherein a weight ratio of the combined anionic and cationic species to the nanoparticles in the dispersion ranges from 1:10 to 10:1 combined species to nanoparticles.