Organic/inorganic nanostructured materials: towards synergistic mechanical and optical properties
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Two designs of inorganic/organic hybrid micro-structures are discussed: (1) silver nanowire reinforced layer-by-layer (LbL) polyelectrolyte composite film and (2) bimetallic silver-gold core-shell nanoparticles. In this work, zero-dimensional spherical gold nanoparticles (AuNPs), one-dimensional silver nanowires (AgNWs), and two-dimensional silver nanoplates (AgNPls) represent the inorganic component. Three-arm star polymer and polyelectrolytes represent the organic component. In the first design, the one-dimensional AgNWs serves as a mechanical reinforcement for the fabrication of mechanically isotropic and anisotropic polyelectrolyte composite films. The composite film is mechanically isotropic when the AgNWs are randomly oriented, and it is anisotropic when the AgNWs are unidirectionally oriented within the LbL polyelectrolyte matrix. Furthermore, above the AgNWs percolation threshold, the AgNWs reinforced LbL composite film is electrically conductive. Therefore, it can find application in ultrathin LbL film-based sensor. In the second design, the zero-dmensional AuNPs were assembled onto one-dimensional AgNWs and two-dimensional AgNPls by means of star polymer linker, or alternatively using polyelectrolytes via electrostatics interaction. The unique feature of these bimetallic silver-gold core-shell nanoparticles is their ability to greatly enhance electric field, due to the silver-gold intra-particle interaction. This allows it to serve as a single-nanoparticle surface enhanced Raman scattering (SERS) substrate for chemical sensing.