D-glucose-derived polymer intermediates as templates for the synthesis of ultrastable and redispersible gold colloids

A two-stage hydrothermal process was developed for the synthesis of highly dispersed Au colloids. In the first stage, a novel glucose-derived polymer template was prepared by the hydrothermal treatment of glucose at 160°C. This template was then further used in the next step to synthesize highly dispersed gold (Au) colloids by hydrothermal treatment with HAuCl₄. The templates treated at 160°C with changing reaction times had different templating effects toward Au species. The 3-h treated template was able tightly adhere to the Au colloids. As a result, an unusual stability was observed for the prepared Au particles that could be repeatedly precipitated and redispersed with the template in H₂O and were also stable against heating (below 160°C) and aging. Meanwhile, the 5-h and 7-h treated templates had much poorer templating effects to Au species, leading to severe aggregation of the Au colloids immobilized on them. The various templating effects were correlated to the different structural features of the templates. Compared to die 5- or 7-h treated templates that were deeply carbonized, the 3-h treated template was only slightly carbonized, thus possessing a lot of functional and hydrophilic O-containing groups that could bind to Au species. These differences in templating ability were also observed in the Au samples prepared by the sonication-assisted method. The highly dispersed Au colloids immobilized on the 3-h treated template were tested for CO oxidation, and a good catalytic activity and stability for CO oxidation was observed.