  A recent article by Lee et al. in Nature Communications has reported an
intriguing phenomenon that gold nanostructures, AuNSs, can be spontaneously
formed in aqueous microdroplets with dissolved tetrachloroaurate ions. The
authors suggested three possible electron donors for the reduction of AuCl4-,
including the strong electric field at the microdroplet surface, the hydroxyl
ions, and the AuCl4- itself. However, we find that the hydrogen peroxide
spontaneously produced at the microdroplets might be also responsible for the
AuCl4- reduction.
