Synthesis, properties, and surface enhanced Raman scattering of gold and silver nanoparticles in chitosan matrix

We present here a facile route to in-situsynthesis of free-standing metal (gold or silver) nanoparticles-embedded chitosan films by thermal treatment. The produced nanoparticles were confirmed by UV-vis spectroscopy and transmission electron microscopy (TEM). Interestingly, an exquisite dendritic structure was observed in the resulting silver-chitosan film, which was not present in pure chitosan and gold-chitosan samples. We speculated that the formation of dendritic structures may be due to the presence of nano-sized silver particles which has an influence on the crystallization behavior and thereby the morphology of biopolyer chitosan. The application of the as-prepared metal-chitosan films in surface-enhanced Raman spectroscopy (SERS) was investigated by using Rhodamine 6G (R6G) as probe molecules. It was found that the resultant metal-chitosan samples, especially silver-chitosan one, could be used as SERS substrates exhibiting excellent enhancement ability.