Abstract: This invention pertains to a surface ligand; preparation of the ligand; colloidal nanoparticle, such as quantum dot bearing one or more of the ligand; and a bioconjugate characterized by a nanoparticle bearing one or more of the ligand conjugated to a biomolecule. The ligand is characterized by the presence of a first module containing atoms that can attach to an inorganic surface; a second module that imparts water-solubility to the ligand and to the inorganic surface that may be attached to the ligand; and a third module that contains a functional group that can, directly or indirectly, conjugate to a biomolecule. Order of the modules can be different and other modules and groups can be on the ligand. Preparation of the ligand includes the steps of reacting a compound having atoms that can attach to an inorganic surface with a water-solubilizing compound that imparts the property of water-solubility to the ligand and the inorganic surface to which it may be attached and purification thereof.