Low-temperature route for precision synthesis of metal oxide nanoparticles

A method for making core-shell nanoparticles, the method comprising:

• providing a solution comprising RCOOH and a corresponding metal carboxylate comprising RCOO− and a metal cation M, wherein M is a group IIIA metal, a group IVA metal, a transition metal, or a combination thereof, and R is saturated or unsaturated C1-C21 aliphatic;
• combining the solution with a solvent comprising R′OH to produce a mixture, wherein R′ is saturated or unsaturated C2-C22 aliphatic, and wherein the solvent is preheated to a temperature T1 of 100-290° C. prior to combining the solution with the solvent;
• maintaining the mixture at a temperature T2 for an effective period of time to form crystalline metal oxide nanoparticles, wherein T2 is less than the thermal decomposition temperature of the corresponding metal carboxylate;
• and
• depositing a metal oxide shell onto the crystalline metal oxide nanoparticles by
• combining the crystalline metal oxide nanoparticles with R′″OH to produce a mixture, where R′″ is saturated or unsaturated C2-C22 aliphatic,
• heating the mixture to a temperature T3 of ≦200° C.,
• providing a solution comprising R″COOH and a corresponding metal carboxylate comprising R″COO− and a metal cation M′, where M′ is a group IIIA metal, a group IVA metal, a transition metal, or a combination thereof, M′ and M are different metals, and R″ is saturated or unsaturated C1-C21 aliphatic;
• combining the solution with the mixture, and
• maintaining the combined solution and mixture at a temperature T4 of ≦200° C. for an effective period of time to form core-shell nanoparticles comprising a crystalline metal oxide core including M and a metal oxide shell including M′ deposited onto the metal oxide core.

A method for making nanoparticles, comprising:

• providing a C1-C5 metal carboxylate comprising a metal cation M, wherein M is a group IIIA metal, a group IVA metal, a transition metal, or a combination thereof;
• combining the C1-C5 metal carboxylate with a molar excess of RCOOH, wherein R is saturated or unsaturated C5-C21 aliphatic;
• heating to convert at least a portion of the C1-C5 metal carboxylate to a metal carboxylate comprising RCOO− and M, thereby forming a solution comprising RCOOH and the metal carboxylate comprising RCOO− and M;
• preheating a solvent comprising R′OH to a temperature ranging from 100° C.-290° C. to form a preheated solvent, wherein R′ is saturated or unsaturated C6-C22 aliphatic;
• injecting the solution at a rate of up to 0.5 mL/min into the preheated solvent to produce a mixture, wherein [R′OH]>[RCOOH]>[M];
• maintaining the mixture at a temperature ranging from 100° C.-290° C. under flowing nitrogen or air for an effective period of time to form crystalline nanoparticles comprising a metal oxide;
• precipitating the crystalline nanoparticles;
• and
• isolating the crystalline nanoparticles.