Divalent silver oxide-diatomite hybrids: Synthesis, characterization and antibacterial activity

To produce better antibacterial and low water-soluble submicron powders of divalent silver oxide (AgO), divalent silver oxide-diatomite (AgO-d) hybrids were studied. AgO-d hybrids were prepared by chemical oxidation, using silver nitrate and diatomite as raw materials and potassium persulfate as oxidant. The results show that AgO-d hybrids with AgO weight percentage up to 20.8% are obtained by oxidation of Ag+ adsorbing on diatomite in alkaline solution (n(KOH)/n(AgNO3)=7.5) for 1.5 h at 333.15 K. Products were characterized by laser particle sizer, SEM, XRD, XPS, FT-IR and atomic absorption spectrophotometer (AAS). AgO-d hybrids are composed of tetragonal cristobalite, amorphous silica, monoclinic divalent silver oxide and a few of cubic silver oxide. Element Ag can be released from AgO-d hybrids but the dissolution speed is slow, which is about 3.20×10−2 mg (L h)−1. Antibacterial effectiveness of AgO-d hybrids was tested against Staphylococcus aureus (S. aureus ATCC6538) and Escherichia coli (E. coli ATCC8099) by the shake-flask method. Results show that AgO-d hybrids possess excellent antibacterial properties. When the concentration of AgO-d hybrids is 10 mg L−1 and the contact time with S. aureus and E. coli is 30 min, the bactericidal rates reach up to 99.974% and 99.944%, respectively.