Copper thin coating deposition on natural pollen particles

We have deposited thin copper coatings on micro-sized natural pollen partic les by electroless plating, using palladium as the catalyst, copper sulfate as the source of deposited metal, and formaldehyde as the reducing agent. A two-step pretreatment process is used to activate the pollen surface with stannous chloride and palladium chloride. The results of XRD, SEM, AES, an d cross-section metallography show that the pollen particles are completely coated by a pure and porous FCC-structured crystalline copper film about 1 mum thick. The film is composed of spherical and some needle-shaped metall ic copper particles. The latter are attributed to the strong aggregation te ndency among neighboring nano-sized copper particles grown with rapid hydro gen release. We find that lightweighted pollen particles are good candidate s for fabricating metallic composite microspheres with core-shell structure s. (C) 2001 Elsevier Science B.V. All rights reserved.