Surface treated Al 2 O 3, CeO 2, SiO 2, γ-Fe 2 O 3, α-Fe 2 O 3 or Fe 3 O 4 nanoparticles with a mean particle size ranging from 1.0 nm to 900.0 nm; comprising a stargraft copolymer with looped and/or linear polymeric structure on a star-graft copolymer, obtainable by a heterogeneous polymerization reaction in the nanoparticle surface proximity, encapsulating at least a portion of said nanoparticles, said surface treatment comprising: Si w x y z wherein w, x, y, and z are tetrafunctional, trifunctional, difunctional, and monofunctional monomeric units, respectively and are present in an amount of 0-50.0 mole percent, 0-50.0 mole percent, 5.0-99.0 mole percent, and 0-5.0 mole percent, respectively, wherein: w is tetraethylorthosilicate; x is selected from the group consisting of γ-glycidoxypropyltrimethoxysilane, γ-methacryloxypropyltrimethoxysilane, methyltrimethoxysilane, n- propyltrimethoxysilane, isobutyltrimethoxysilane, n- hexyltrimetlioxysilane, n-octyltrimethoxysilane, n- octadecyltrimethoxysilane, phenyltrimethoxysilane, 3- (trimethoxysilyl)propylsuccinic anhydride, heptadecafluorotrimethoxysilane, 3-isocyanatopropyltrimethoxysilane, 2-(diphenylphosphino)ethyltrimethoxysilane, 3-aminopropyltrimethoxysilane, 3-mercaptopropyltrimethoxysilane, n-(trimethoxysilylpropyl)EDTA, pentafluorophenylpropyltrimethoxysilane, trifluoropropyltrimethoxysilane, and the triethoxy-containing counterparts of these monomers; y is selected from the group consisting of dicyclohexyldimethoxysilane, diethyldietkoxysilane, dimethyldichlorosilane, dimethyldiethoxysilane, dimethyldimethoxysilane, diphenyldiethoxysilane, diphenyldimethoxysilane, di-n-hexyldichlorosilane, n-hexylmethyldichlorosilane, methyldodecyldiethoxysilane, n-octylmethyldimethoxysilane, and the diethoxy-containing counterparts of these monomers; z is selected form the group consisting of n-octadecyldimethylmethoxysilane, triethylsilanol, trimethylethoxysilane, trimethylmethoxysilane, and the ethoxy-containing counterparts of these monomers. w is tetraethylorthosilicate; x is selected from the group consisting of γ-glycidoxypropyltrimethoxysilane, γ-methacryloxypropyltrimethoxysilane, methyltrimethoxysilane, n- propyltrimethoxysilane, isobutyltrimethoxysilane, n- hexyltrimetlioxysilane, n-octyltrimethoxysilane, n- octadecyltrimethoxysilane, phenyltrimethoxysilane, 3- (trimethoxysilyl)propylsuccinic anhydride, heptadecafluorotrimethoxysilane, 3-isocyanatopropyltrimethoxysilane, 2-(diphenylphosphino)ethyltrimethoxysilane, 3-aminopropyltrimethoxysilane, 3-mercaptopropyltrimethoxysilane, n-(trimethoxysilylpropyl)EDTA, pentafluorophenylpropyltrimethoxysilane, trifluoropropyltrimethoxysilane, and the triethoxy-containing counterparts of these monomers; y is selected from the group consisting of dicyclohexyldimethoxysilane, diethyldietkoxysilane, dimethyldichlorosilane, dimethyldiethoxysilane, dimethyldimethoxysilane, diphenyldiethoxysilane, diphenyldimethoxysilane, di-n-hexyldichlorosilane, n-hexylmethyldichlorosilane, methyldodecyldiethoxysilane, n-octylmethyldimethoxysilane, and the diethoxy-containing counterparts of these monomers; z is selected form the group consisting of n-octadecyldimethylmethoxysilane, triethylsilanol, trimethylethoxysilane, trimethylmethoxysilane, and the ethoxy-containing counterparts of these monomers.