Abstract: A method is disclosed for synthesizing core-shell nanoparticles or microparticles in an aqueous solution. A displacement reaction produces a protective, noble metal shell around nanoparticles or microparticles, for example a copper shell around cobalt nanoparticles. In an electroless displacement reaction in an aqueous solution, a less noble metal core is oxidized by cations of a more noble metal in solution, and the noble metal ions are reduced by the less noble atoms of the metal core, forming a thin layer of the reduced noble metal on the surface of the core metal. The formation of the nanoscale shell is self-terminating once the core is fully covered, because the core metal is then inaccessible for further redox reaction with ions in solution. The magnetic core is preferably a ferromagnetic metal, e.g., Co, Fe, Ni. The shell is a more noble metal, e.g., Cu, Ag, Au, Pt, or Pd.

Abstract: An inexpensive apparatus and method of fabricating completely polymeric (e.g., SU-8, PMMA, and PEEK) microfluidic reactors suitable for the synthesis of chemicals, particularly nanoparticles (e.g., mono, bi, tri, alloy, core-shell, polymeric, and metal-polymer nano-particles), is disclosed. A high precision process uses polymeric microfluidic patterning techniques and a new microfluidic sealing technique, referred to as “flexible semi-solid transfer,” to fabricate high aspect ratio polymeric micro-reactors. In one embodiment, high quality microfluidic channels are patterned onto a support substrate. The microfluidic structure is then sealed by transferring a polymeric material from a sacrificial substrate to the microfluidic structure, and cured. Then, the structure is bonded to a second support structure to form a micro-reactor.