Organically modified metal nanoparticles

An organically modified metal oxide nanoparticle wherein a hydrocarbon group is directly bonded to a surface of each metal oxide nanoparticle through a linkage from the hydrocarbon group selected from the group consisting of an ether bond, an ester bond, a bond through an N atom, a bond through an S atom, a metal-C— bond, a metal-C═ bond, and a metal-(C═O)— bond, wherein said hydrocarbon group is a hydrocarbon group with a chain having 1, 2 or 3 carbon atoms, or a long-chain hydrocarbon group with a chain having 4 or more carbon atoms, or said hydrocarbon group is a substituted or unsubstituted straight-chain or branched-chain alkyl group, and said metal oxide is an oxide of a metal element selected from group consisting of an element of group VIII, an element of group IB, an element of group IIB, an element of group IIIB, an element of group IVB, an element of group VB, an element of group VIB, and an element of groups IA to VIIA, in the long-period periodic table, provided that TiO2 is excluded from said metal oxides, wherein the organically modified metal oxide nanoparticle is produced by reacting an organic modifying agent (organic modifier) with the surface of a metal oxide nanoparticle in the reaction field of water at a pressure of 10 MPa or above and at a temperature of 250° C. or above to form said organically modified metal oxide nanoparticle wherein the hydrocarbon group is covalently bonded to the surface of said metal oxide nanoparticle.