A Molecular Template Designed by the Modification of a Helix-Forming β-1,3-Glucan Polysaccharide To Fabricate One-Dimensional Nanostructures

We report the development of a new templating molecule designed by the modification of a helix-forming beta-1,3-glucan polysaccharide to the cationic semiartificial one and its application to the fabrication of one-dimensional (1D) gold nanostructures by simple photoirradiation. Transmission electron microscopy observation showed that Au(III) ions are primarily reduced to gold nanoparticles self-assembling into the ID array with the aid of the cationic beta-1,3-glucan polysaccharide, which gradually fuse into the ID gold nanostructure with the tapelike structure. The gold nanotape structure could not be created by neutral beta-1,3-glucan polysaccharides or random coil synthetic cationic polymers. These findings consistently support the view that Au(III) ions are reduced by unmodified OH groups to gold nanoparticles under the photoirradiation, which are wrapped in the helical structure of the cationic beta-1,3-glucan polysaccharide and eventually fuse into gold nanotapes. One may regard, therefore, that this cationic beta-1,3-glucan polysaccharide can act as an all-in-one template playing three roles of reduction, ID arrangement, and fusion of gold nanoparticles. In addition, we found an interesting phenomenon that the obtained gold nanotapes coated with cationic beta-1,3-glucan polysaccharides show unique surface-enhanced Raman scattering for anionic porphyrines organized on the surface of gold nanotapes through the electrostatic interaction.