Professor James Economy's Group
Highly Effective Bactericides Based on Silver Coated Fiber Glass
Activated carbon has been widely used in water purification due to its high adsorption rates and capabilities. The inherent drawback of carbon materials, however, is that they have excellent biocompatibility with bacteria. Bacteria may breed on carbon during the purification process, thus making carbon materials themselves pollutants. To get around this problem, some researchers have explored depositing colloidal-sized silver, a wide-spectrum antibiotic, onto carbon substrate as bactericides1-5. Our experiments showed there are a number of problems with this approach. First of all, the silver coated activated carbon has limited antibacterial activity. Secondly, high temperatures required for carbonizing and activating activated carbon fibers cause silver particles to coalesce and form large particles that have inferior antibacterial activities. Thirdly, severe attrition of silver particles not only cause antibacterial activities to deteriorate dramatically, but may potentially cause Argyria as well.
In this study, we developed a new kind of antibacterial fibers by chemically coating fiber substrates of glass with colloidal sized silver particles. The antibacterial activities were evaluated against E.coli and compared with their regenerability has been investigated as well.
Antibacterial fibers based on activated carbon fibers were prepared with different carbon contents. As shown in Figure 1, while silver contents remained at 3%(wt), the higher the carbon content, the higher the number of E.coli left live, the less efficient these fibers were as bactericides. Silver coated activated carbon fiber with 18% carbon content killed up to 4 orders of E.coli in the contaminated water, while with 90% carbon content, only minimal bioactivity was observed. It appeared the uncovered carbon surface still has excellent affinity to bacteria. To eliminate bacteria breeding, fiberglass was chosen over activated carbon fibers as fiber substrate, and quantitative removal of E. coli was achieved.
study on the effect of silver content of activated carbon
fibers on their antibacterial activities revealed
activated carbon has very limited tunability as fiber
substrate. ACF-15 was coated with various amount of
silver, as can be seen from Figure 2, BET surface area of
these antibacterial fibers decreased dramatically as
silver content increased, and larger silver particles (1
~ 10um) were more likely to form on the activated carbon
surfaces. As a result, biological activities against E.
coli decreased, but only slightly. This suggested
that antibacterial activities of silver coated activated
carbon fibers were not sensitive to fiber properties,
such as surface area and silver content, which made it
difficult to tailor the antibacterial activities. As
comparison, antibacterial fibers made from fiberglass
substrate were easily modified by changing silver
content, fiber diameter and surface morphology to achieve
quantitative removal of bacteria in minutes.
1. Oya, A. and Yoshida, S. (1993). Antibacterial activated fiber derived from phenolic resin containing sliver nitrate. Carbon 31, 71-73
2. Oya, A., Wakahara, T. and Yoshida, S. (1993). Preparation of pitch-based antibacterial activated carbon fiber. Carbon 31, 1243-1247.
3. Oya, A., Kimura, M., Sugo, T., Kataki, A., Abe, Y., Iizuka, T., Makiyama, N., Linares-Solano, A., and Salinas-Martinez de Lecea (1994). Antibacterial activated fiber derived from methyl methacrylate-grafted phenolic resin fibers. Carbon 31, 107-110.
4. Li, Ch.Y., Wan, Y.Z., Wang, Y.L., Jiang, X.Q., and Han, L.M. (I998) Preparation and Characterization of antibacterial pitch-based activated carbon fiber supporting silver. Carbon 36, 61-65.
5. Wang, Y.L., Wan, Y.Z., Dong, X.H., Cheng, G.X., Tao, H.M., and Wen, T.Y. (I998) Preparation and Characterization of antibacterial viscose-based activated carbon fiber supporting silver. Carbon 36, 1567-1571.