A method for modifying a thiol group is provided. The method includes:
providing a first material containing at least one sulfhydryl group;
providing a second material containing at least one thiourea group; and
reacting the first material with the second material in the presence of
copper (II) ions to quickly form a disulfide bond between the sulfhydryl
group and the thiourea group, wherein the disulfide bond can be easily
reduced.