Preparation and characterization of silver loaded montmorillonite modified with sulfur amino acid

Abstract

• The silver loaded l -cystine modified MMT (Ag@AA-MMT-3) with Ag content of 10.93 wt% was obtained. • The XPS and FT-IR confirmed the strong interaction between sulfur and silver. • Ag + on Ag@AA-MMT-3 was turned to Ag NPs to get Ag@AA-MMT-UV with good slow release, antibacterial property. • The existence of uniform Ag NPs on Ag@AA-MMT-UV was proved by TEM and UV–vis. • The mechanism for the growth of the Ag NPs on the amino acid modified MMT was also discussed. The Na + montmorillonite (MMT) was modified with sulfur containing amino acid ( l -cystine, l -cysteine or l -methionine) and characterized by energy dispersive spectrometer (EDS), X-ray diffraction (XRD) and Fourier transform infrared spectrum (FT-IR). The results showed the modification was smooth and the surface condition of MMT was changed with sulfur containing groups. Then silver was loaded on the modified MMTs via ion-exchange reaction under microwave irradiation, the spectra of X-ray photoelectron spectroscopy (XPS), EDS and FT-IR confirmed the successful loading of massive silver and the strong interaction between sulfur and silver, the silver loaded l -cystine modified MMT (Ag@AA-MMT-3) with a silver content of 10.93 wt% was the highest of all. Further more, the Ag@AA-MMT-3 was under the irradiation of a UV lamp to turn silver ions to silver nano particles (Ag NPs). The XPS, specific surface area (SSA), transmission electron microscopy (TEM), XRD patterns and UV–vis spectra proved the existence of uniform nano scaled metallic Ag NPs. By contrast, the UV irradiated Ag@AA-MMT-3 (Ag@AA-MMT-UV) showed a much better slow release property than Ag@AA-MMT-3 or Ag@MMT. The Ag@AA-MMT-UV showing a large inhibition zone and high inhibition ratio presented very good antibacterial property.