Controllable synthesis of floatable nanocrystalline Ag2S and Ag by a silane coupling agent-modified solvothermal method

Nanocrystalline Ag2S and Ag have been synthesized by a silane coupling agent (SCA) modified solvothermal method, followed by thermal treatment in N2 atmosphere. The key of this method is to select bifunctional SCAs with HS or NH2 ends, which easily couple Ag+ prior to the solvothermal process, while the (H3CO)3Si ends of SCA easily change into (HO)3Si ends by hydrolysis reactions. These factors are favorable for the production of nanocrystalline Ag2S and Ag with small nanoparticle size during the solvothermal processes, meanwhile distributed homogeneously in the networks resulting from the polymerization of (HO)3Si groups. The formed networks effectively inhibit the aggregation and growth of Ag2S and Ag crystallites and keep their monodispersion. The resulting spherical Ag2S and Ag nanoparticles with average diameter of about 10 nm are floatable in water, attributed to the small nanoparticle size and to the formed silane-coupling link.