Surface-modified nanoparticles wherein each nanoparticle includes an inorganic core and surface modifying groups, wherein the surface modifying groups include at least one triorganoborane-amine complex having the structure —Z—NHR1—B(R2)3 wherein: Z is a divalent organic group; R1 is H or an organic group; and each R2 is independently an organic group bound to the boron atom through a carbon atom. The inorganic core is typically an inorganic oxide core, e.g., silica, zirconia, or alumina.