A ligand design allows compact nanoparticle materials, such as quantum dots (QDs), with excellent colloidal stability over a wide range of pH and under high salt concentrations. Self-assembled biomolecular conjugates with QDs can be obtained which are stable in biological environments. Energy transfer with these ligands is maximized by minimizing distances between QDs/nanoparticles and donors/acceptors directly attached to the ligands or assembled on their surfaces.