Organically modified metal oxide nanoparticles containing two or more cores including a plurality of metal atoms and a plurality of oxygen atoms covalently bonded to the plurality of metal atoms; a first modifying group that is a ligand coordinated to each of the cores and selected from the group consisting of a carboxylic acid carboxylate, a sulfonic acid sulfonate, and a phosphonic acid phosphonate; and a second modifying group that is coordinated to each of the cores and is a ligand having a structure different from that of the first modifying group and/or an inorganic anion, in which organically modified metal oxide nanoparticles have a structure in which the cores are crosslinked through a coordinate bond by at least the first modifying group.