Although precise regulation of the
crystalline structures of metal
oxides is an effective method to improve their antibacterial activities,
the corresponding mechanisms involved in this process are still unclear.
In this study, three kinds of cuprous oxide (Cu2O) samples
with different structures of cubes, octahedra, and rhombic dodecahedra
(c-Cu2O, o-Cu2O, and r-Cu2O) have
been successfully synthesized and their antibacterial activities are
compared. The antibacterial activities follow the order of r-Cu2O > o-Cu2O > c-Cu2O, revealing
the significant
dependence of the antibacterial activities on the crystalline structures
of Cu2O. Quenching experiments, as well as the NBT and
DPD experiments indicate that CuIIOO• superoxo and CuIIOOH peroxo,
instead of •OH, O2
•–, and
H2O2, are the primary oxidizing species in the
oxidative damage to E. coli. Raman
analysis further confirms the presence of both CuIIOO• superoxo and CuIIOOH peroxo on the surface of r-Cu2O. On the other
hand, the NCP experiment reveals that Cu+, instead of Cu2+, also contributes to the antibacterial process. This study
provides new insight into the antibacterial mechanisms of Cu2O.