In situ growth of gold colloids within alginate films.

Gold-alginate bionanocomposite films were prepared by impregnation of alginate films with HAuCl(4) followed by reduction with glucose. The mannuronate over guluronate ratio (M/G) of the polymer as well as the initial polymer concentration were shown to influence the film thickness, the amount of trapped Au(3 + ) ions, and the volume fraction of Au(0) nanoparticles but not the size of these colloids (about 4 nm). The homogeneity of the gold colloid dispersion within the alginate gels was studied by transmission electron microscopy (TEM) and confirmed by simulation of the surface plasmon resonance (SPR) spectra using the Maxwell-Garnett model. The calculated spectra also provided fruitful information about the gold colloid/alginate interface. Overall, the whole process is controlled by the balance between the M/G ratio, defining the polymer affinity for Au(III) species, and the solution viscosity, controlling the diffusion phenomena.