Preparation and high bacteriostatic action of the activated carbons possessing ultrafine silver particles

The new carbon composites possessing ultrafine silver particles (0.001 wt%, size 1.8–2.5 nm) show high bacteriostatic action toward bacteria such as Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus and Bacillus subtilis and a yeast fungus like Candida albicans. The present carbon composite was prepared by the steam activation of a mixture of a petroleum pitch and N,N-dimethylamino-methylphenylsilver (0.012 mg/g) at 930 °C for 15–19 min. The growth inhibitory effect for Gram-negative bacteria such as E. coli and P. aeruginosa varies greatly depending on the amount of ultrafine silver particles, while the Gram-positive bacteria show little effect by the amount of silver particles used. A yeast fungus like C. albicans exhibits relatively small biostatic action as compared with bacteria, but it shows enough activity when we used the carbon material possessing 0.01 wt% of Ag particles.