The BC powders (particle size<10 .mu.m, Taiwan Paiho) are activated with surfactant sodium alginate under stirred for 1 h. The as-prepared BC powders (2 g) are immersed into 100 mL of biamminesilver nitrate ([Ag(NH.sub.3).sub.2]NO.sub.3) solutions, which are formed by adding 28 wt. % aqueous ammonia into AgNO.sub.3 solution at room temperature. After stirring for 1 h, dilute aqueous solutions of hydrazine monohydrate are separately prepared and introduced to the BC-AgNO.sub.3 solutions in appropriate quantities (molar ratio 1:1 with respect to silver nitrate) by a syringe. Stirring is continued under inert atmosphere at room temperature for another 4 h. The BC/Ag particles are separated and washed with deionized water and ethanol, then dried in vacuum at 60.degree. C. for overnight.