Professor James Economy's Group

[Bactericides Materials] [HDD Lubricants] [New materials for Fuel Cell] [Gas Hydrates]

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 bactericides^1-5. 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.

A related 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.
 

Figure 1. Effect of carbon content of silver coated fibers on their antibacterial activities	Figure 2. Effect of silver content on antibacterial activities

Figure 3. Surface morphology of silver coated fiberglass. (The white spots are silver particles).	Figure 4. Regeneration of silver coated fiberglass

References

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.

Gordon Nangmenyi