Converting nanoparticles in oil to aqueous suspensions

Abstract

An improved process for converting an oil suspension of nanoparticles (NPs) into a water suspension of NPs, wherein water, surfactant and a non-surfactant salt is used instead of merely water and surfactant, leading to greatly improved NP aqueous suspensions.

1 . A method of converting nanoparticles (NPs) in oil to NPs in aqueous suspension comprising: adding a surfactant and water and a non-surfactant salt in any order to a mix of NPs in oil, such that the concentration of the surfactant is above the critical micellar concentration, and stirring at a temperature above the boiling point of said oil and below that of water to form an aqueous suspension of NPs wherein said suspension of NPs contain more compact surfactant micelles than those formed in water without a non-surfactant salt. 
     
     
         2 . The method of  claim 1 , further comprising adding alcohol or amines or both to the mix of NPs in oil. 
     
     
         3 . The method of  claim 1 , wherein said surfactant is selected from anionic, cationic, nonionic, zwitterionic, or Gemini surfactants, and combinations thereof. 
     
     
         4 . The method of  claim 1 , wherein said surfactant is sodium 1,2-bis(2-ethylhexoxycarbonyl)ethanesulfonate (AOT). 
     
     
         5 . The method of  claim 1 , wherein said surfactant is selected from cetyl trimethyl ammonium bromide (CTAB), cetylpyridinium chloride (CPC), benzalkonium chloride (BAC), Benzethonium chloride (BZT), amine and imidazoline salts such as primary, secondary and tertiary amine hydrochlorides, imidazoline hydrochlorides alkyl poly(ethylene oxide), copolymers of poly(ethylene oxide) and poly(propylene oxide), alkyl polyglucosides, alkyl phenol ethoxylate, polyoxyethylene esters of fatty acids, polyoxyethylene fatty acid amides, alkyl polysaccharides, ethoxylates of alkyl amine, castor oil, end capped synthetic alcohol, tallow amine and alkanol amine mercaptan, dodecyl betaine, dodecyl dimethylamine oxide, docamidopropyl betaine, coco ampho glycinate and combinations thereof. 
     
     
         6 . The method of  claim 1 , wherein said non-surfactant salt comprises a cationic portion selected from the group consisting of alkali, alkaline earth metal, sodium, potassium, magnesium, calcium, and quaternary ammonium and an anionic portion selected from the group consisting of halide, acetate, malate, fumarate, citrate, succinate, phosphate, polyphosphates, hypochlorite, perchlorite, carbonate, bicarbonate, bisulphite, sulphite, sulphonate, and nitrate. 
     
     
         7 . The method of  claim 1 , wherein said non-surfactant salt is NaCl. 
     
     
         8 . The method of  claim 1 , wherein said NPs in oil comprises a mixture of two or more different NPs. 
     
     
         9 . A method of converting nanoparticles (NPs) in oil to NPs in aqueous suspension comprising:
 a. dissolving NPs into an oil having a boiling point lower than that of water;   b. preparing a surfactant solution in a non-surfactant salt-water such that the concentration of the surfactant is above the critical micellar concentration; and   c. adding the NP containing oil blend of step a) to the surfactant solution and stirring the resulting dispersion at a temperature above the boiling point of said oil and below that of water to form an aqueous suspension of NPs   d. wherein more compact surfactant micelles are formed in said non-surfactant salt-water than those form in water not containing a non-surfactant salt.   
     
     
         10 . The method of  claim 9 , further comprising adding alcohol or amines or both to the mix of NPs in oil. 
     
     
         11 . The method of  claim 9 , wherein said stirring occurs above the boiling point of said oil and below that of water. 
     
     
         12 . The method of  claim 9 , wherein said surfactant is selected from anionic, cationic, nonionic, zwitterionic, or Gemini surfactants, and combinations thereof. 
     
     
         13 . The method of  claim 9 , wherein said surfactant is sodium 1,2-bis(2-ethylhexoxycarbonyl)ethanesulfonate (AOT). 
     
     
         14 . The method of  claim 9 , wherein said surfactant is selected from cetyl trimethyl ammonium bromide (CTAB), cetylpyridinium chloride (CPC), benzalkonium chloride (BAC), Benzethonium chloride (BZT), amine and imidazoline salts such as primary, secondary and tertiary amine hydrochlorides, imidazoline hydrochlorides alkyl poly(ethylene oxide), copolymers of poly(ethylene oxide) and poly(propylene oxide), alkyl polyglucosides, alkyl phenol ethoxylate, polyoxyethylene esters of fatty acids, polyoxyethylene fatty acid amides, alkyl polysaccharides, ethoxylates of alkyl amine, castor oil, end capped synthetic alcohol, tallow amine and alkanol amine mercaptan, dodecyl betaine, dodecyl dimethylamine oxide, docamidopropyl betaine, coco ampho glycinate and combinations thereof. 
     
     
         15 . The method of  claim 9 , wherein said non-surfactant salt comprises a cationic portion selected from the group consisting of alkali, alkaline earth metal, sodium, potassium, magnesium, calcium, and quaternary ammonium and an anionic portion selected from the group consisting of halide, acetate, malate, fumarate, citrate, succinate, phosphate, polyphosphates, hypochlorite, perchlorite, carbonate, bicarbonate, bisulphite, sulphite, sulphonate, and nitrate. 
     
     
         16 . The method of  claim 9 , wherein said non-surfactant salt is NaCl. 
     
     
         17 . The method of  claim 9 , wherein said NPs in oil comprises a mixture of two or more different NPs.