A ligand which is a copolymer comprising at least 2 monomers and having the following formula I: x y, wherein A comprises at least one anchoring monomer comprising a first moiety M A having affinity for the surface of a nanocrystal, B comprises at least one hydrophilic monomer comprising a second moiety M B having a high water solubility comprising at least one zwitterionic moiety selected from the group of an aminocarboxylate, an aminosulfonate, a carboxybetaine moiety wherein the ammonium group may be included in an aliphatic chain, a five-membered cycle, a five-membered heterocycle comprising 1, 2 or 3 further nitrogen atoms, a six-membered cycle, a six-membered heterocycle comprising 1, 2, 3 or 4 further nitrogen atoms, a sulfobetaine moiety wherein the ammonium group may be included in an aliphatic chain, a five-membered cycle, a five-membered heterocycle comprising 1, 2 or 3 further nitrogen atoms, a six-membered cycle, a six-membered heterocycle comprising 1, 2, 3 or 4 further nitrogen atoms, a phosphobetaine wherein the ammonium group may be included in an aliphatic chain, a five-membered cycle, a five-membered heterocycle comprising 1, 2 or 3 further nitrogen atoms, a six-membered cycle, a six-membered heterocycle comprising 1, 2, 3 or 4 further nitrogen atoms, a phosphorylcholine, a phosphocholine moiety, and combinations thereof or a PEG moiety; and each of x and y is independently a positive integer, wherein when A comprises a moiety M A which is an imidazole moiety, then B comprises a second moiety M B which is not a sulfobetaine, a carboxybetaine or a phosphobetaine moiety; when B comprises a monomer comprising a second moiety M B which is a PEG moiety, then B further comprises at least one monomer comprising a second moiety M B which is not a PEG moiety. x y, wherein A comprises at least one anchoring monomer comprising a first moiety M A having affinity for the surface of a nanocrystal, B comprises at least one hydrophilic monomer comprising a second moiety M B having a high water solubility comprising at least one zwitterionic moiety selected from the group of an aminocarboxylate, an aminosulfonate, a carboxybetaine moiety wherein the ammonium group may be included in an aliphatic chain, a five-membered cycle, a five-membered heterocycle comprising 1, 2 or 3 further nitrogen atoms, a six-membered cycle, a six-membered heterocycle comprising 1, 2, 3 or 4 further nitrogen atoms, a sulfobetaine moiety wherein the ammonium group may be included in an aliphatic chain, a five-membered cycle, a five-membered heterocycle comprising 1, 2 or 3 further nitrogen atoms, a six-membered cycle, a six-membered heterocycle comprising 1, 2, 3 or 4 further nitrogen atoms, a phosphobetaine wherein the ammonium group may be included in an aliphatic chain, a five-membered cycle, a five-membered heterocycle comprising 1, 2 or 3 further nitrogen atoms, a six-membered cycle, a six-membered heterocycle comprising 1, 2, 3 or 4 further nitrogen atoms, a phosphorylcholine, a phosphocholine moiety, and combinations thereof or a PEG moiety; and each of x and y is independently a positive integer, wherein when A comprises a moiety M A which is an imidazole moiety, then B comprises a second moiety M B which is not a sulfobetaine, a carboxybetaine or a phosphobetaine moiety; when B comprises a monomer comprising a second moiety M B which is a PEG moiety, then B further comprises at least one monomer comprising a second moiety M B which is not a PEG moiety.