Fabrication and characterization of gold nanoflowers formed via chitosan-tripolyphosphate template films for biomedical applications.

Flowerlike gold nanostructure was facilely prepared by the seed-mediated growth of gold nanoparticles in chitosan-TPP template films. Firstly, chitosan nanoparticles, spontaneously formed by inter and/or intra cross-linking with TPP, were transformed into gel-type of chitosan-TPP films under strong sonication process. After then, gold seeds (1-3 nm) were entrapped in chitosan-TPP films via electrostatic interactions, and the resulting films were subsequently used as a template for growing gold nanoparticles and subsequent formation of anisotropic gold nanoflowers. The size and optical properties of gold nanoflowers were controlled simply by changing the ratio of gold salts to chitosan-TPP template films. Gold nanoflowers consisted of many aggregated nanodots exhibited broad Plasmon-derived absorption bands with strong red-shift into NIR wavelength, which might be a good prospect for SERS and biomedical applications.