PVA-assisted hydrothermal synthesis of copper@carbonaceous submicrocables: Thermal stability, and their conversion into amorphous carbonaceous submicrotubes

Ultralong Cu@carbonaceous submicrocables with diameters of 0.4-0.6 mu m and lengths up to and exceeding 100 mu m have been fabricated successfully by a poly(vinyl alcohol)- (PVA-) assisted hydrothermal carbonization process using copper chloride and maltose as materials. In this one-pot synthesis, poly(vinyl alcohol) (PVA) played an important role in the formation of these submicrocables as a structure-directing agent to effectively restrain the formation of carbonaceous spheres that are normally nucleated from bulk solutions. In addition, the combined synergistic effects of both the carbohydrates and the PVA enable the formation of elegant Cu@carbonaceous submicrocables. Furthermore, control of the initial pH value (similar to 7-8) and reaction temperature (similar to 180 degrees C) is also essential for the formation of cablelike structures. The effects of other saccharides such as glucose, beta-cyclodextrin, and starch on the formation of Cu@carbonaceous submicrocables were also examined under similar conditions. The thermal stability of as-prepared Cu@carbonaceous submicrocables was studied. In addition, removal of the copper cores of Cu@carbonaceous submicrocables at ambient temperature in a mixed solution of hydrochloric acid and H2O2 can form well-defined amorphous carbonaceous submicrotubes.