Synthesis of au/co hollow microspheres via galvanic replacement reaction in organic solvent

摘要

Cobalt/gold hollow microspheres were successfully prepared through galvanic replacement in an organic solvent. The diameters of these hollow microspheres ranged from 800 nm to 1 μm. However, the surface of the hollow microsphere was very rough. Nanospikes of various lengths from about 40 to 100 nm were grown on the surface of these spheres. Initially, particles with "island-like" rough surfaces were found with the addition of 4 ml chloroauric acid (HAuCl_4). When the volume of HAUCl_4 increased from 4 to 5 ml, microspheres with a hollow structure were formed. Some broken microspheres were observed when HAuCl_4) was further increased to 6 ml. X-ray diffraction results showed a high-intensity sharp peak of gold when the HAuCl_4 in the sample increased. After the galvanic replacement reaction, the cobalt content in the sample decreased meanwhile the gold content increased. This can be seen from energy dispersive X-ray analysis spectroscopy and also evident from the thermo gravimetric analysis result. The hollow Au/Co microspheres showed two broad plasmonic peaks in the ultraviolet-visible measurement. The plasmonic peaks at longer wavelengths shifted to the near-infrared region with the addition of HAUCl_44.