Study on in situ synthesis of konjac glucomannan/silver nanocomposites via photochemical reduction

Konjac glucomannan (KGM)/Silver nanocomposites have been prepared directly in the dilute hydrosol of KGM using photochemical reduction of Ag+. The KGM/Ag nanocomposites have been characterized by means of Fourier transform infrared (FTIR) spectra, transmission electron microscopy (TEM), and thermalgravimetry (TG). The results of FTIR showed that the wavenumbers and the strengths of some characteristic peaks of KGM treated by silver nanoparticles were changed obviously, the characteristic peaks of the O-H stretching and the C-O- (H) stretching became wider with increasing concentrations of the reactants, and the characteristic peaks of the C-H stretching and the C-O- (H) stretching shifted to high wavenumbers with increasing time of photochemical reduction. The images of TEM indicated that Ag nanoparticles were finely dispersed inside the KGM films with different shapes, such as sphere-like (average diameters of 9 +/- 4 nm) and star-like (edge lengths of about 20 nm), respectively. These suggested that the morphology and the agglomerated state of Ag nanoparticles in the composites changed with the conditions of the preparation, especially with the concentrations of Ag+ and KGM as well as the time of photochemical reduction. The KGM and KGM/Ag films had remarkably different thermal properties from the TG curves. The mechanism of interaction between the polysaccharide and the silver nanoparticles has also been generally discussed.