Low-temperature synthesis of Au/polyaniline nanocomposites: Toward controlled size, morphology, and size dispersity

Varying the concentration and molar ratio between aniline and AuCl ₃ leads to a series of Au/polyaniline (PANI) nanocomposites with a wide range of morphologies ranges from nanosphere, nanorod, to complex nanosheet assemblies. These nanocomposites consist of an ensemble of very small Au nanoparticles held together by a PANI matrix, which arise from the oxidation of aniline by metal ions. Using a steric stabilizer such as poly(vinyl pyrrolidone), we have demonstrated control over size dispersity and morphology to achieve monodispersed nanocomposites. These nanoparticles embedded in the PANI matrix are coupled electronically and thus lead to a shift of plasmonic absorption from 500 nm down to 900 nm depending on the Au nanoparticle size and morphology. PANI that is bound to the nanoparticles can be washed off with N-methyl-2-pyrrolidone (NMP) to release individual nanoparticles to form a stable Au nanoparticle solution. On the basis of the above results, we propose a possible formation mechanism of hybrid nanocomposites encompassing Au nanoparticles in a PANI matrix.