“… 81–89 Significantly, high-intensity ultrasound irradiation was able to extremely create small Au nanoclusters, Ag nanoclusters, and Cu nanoclusters (less than 2 nm) by using some polymer molecules ( e.g. , polymethylacrylic acid) as a capping agent, 90–94 and such nanoclusters were likely to develop widespread applications in bioimaging, biosensing, and single-molecule studies.…”