Fabrication of metal-coated organic microcrystals

For the improvement of third-order nonlinear optical susceptibility, we fabricated the metal-coated organic microcrystals by nonelectrolytic plating method. Silver and gold coating were examined to polydiacetylene (PDA) microcrystal as a core. In case of gold coating using tetrachloroauric acid (HAuCl₄), there was no promising way to obtain Au-coated PDA microcrystals. On the other hands, silver coating using ammine complex of silver salt, [Ag(NH₃)₂]NO₃, onto the fibrous PDA microcrystals was successfully performed by simple silver mirror reaction. Besides the plating on PDA microcrystals with 100 nm in size, the reduction of silver using glucose yielded fine silver-coated PDA microcrystals. This difference in coating between Ag and Au is related to the electrostatic interaction between metal ion and ζ-potential of microcrystal surface.