Abstract:
Silver nanoparticles were synthesized by chemical reduction, then intercalated
into a layer of kaolinite, one of an important raw material in ceramic industries was
performed. Three kinds of weak reducing agents : Ascorbic acid, D-glucose and UV
irradiation, were used to reduce the absorbed silver ion (Ag+) to metallic silver
nanoparticles (Ag0) for antimicrobial purpose. Prior to this step, the lamellae of kaolin
was enlarged by intercalation of dimethyl sulfoxide (DMSO), then it was suspended in
aqueous AgNO3 solution with various ratios of Ag to kaolin at 0.1, 0.3, 0.5, 0.7 and
1 wt %. The results indicated that 0.4 M ascorbic acid was the optimum reducing agent
because it could produce the highest percent yield and the smallest particle size of Ag
particles. Phase analysis of the as-prepared modified kaolin which is so called as silver
clay characterized by XRD, microstructure observed by SEM and TEM showed that
there were silver particles in the silver clay which was correlated to the initial ratio of Ag
to kaolin. Finally, antibacterial activities against E.coli of the as-prepared silver clay and
the as-calcined silver clay at 1200 C were tested by spread plate technique to find the
minimum inhibitory concentration (MIC) of silver nanoparticle. The result showed that
0.3 wt % Ag/kaolin was the MIC for both of the as-prepared and the as-calcined
samples. Moreover, the result of antibacterial activity performed by disc diffusion
method also clearly observed that the mean diameters of inhibition zone were 17 and
15 mm for the as-prepared and the as-calcined Ag clay, respectively.