1,1,1-Trifluoroethyl-PEG4-azide is a crosslinker containing an azide group and a trifluoroethyl group. The azide group enables Click Chemistry. The hydrophilic PEG spacer increases solubility in aqueous media. The trifluoroethyl group is used to react with lysine and other primary amine groups in proteins, antibody and other molecules and surfaces.