We have systematically investigated and found surprising superior catalytic activities of very short DNAzymes for copper(I)-catalyzed azide-alkyne cycloaddition (CuAAC), both in solution and on surface. As a key reaction of the "click chemistry" class, CuAAC is a highly efficient and specific covalent conjugation tool with demonstrated applications in organic synthesis, bioconjugation, and surface functionalization; however, it requires the presence of the Cu(I) catalyst, which is an unstable species in aqueous solutions. We show here that one ultrashort, 14-nucleotide-truncated fragment of an earlier