CF® dye picolyl azide reacts with alkyne to form 1,2,3-triazole by 1,3-dipolar Huisgen cycloaddition through the use of a much lower copper (I) concentration without sacrificing reaction efficiency. CF® dyes are Biotium's line of next-generation fluorescent dyes with advantages in brightness, photostability, and conjugate specificity compared to other fluorescent dyes. Far-red fluorescent CF®647 dye has excitation/emission at 650/665 nm.