Serial Ionic Exchange for the Synthesis of Multishelled Copper Sulfide Hollow Spheres

摘要

In recent years, ion exchange has been widely used as a general means for chemical transformation of inorganic nanostructured materials. In particular, both cation and anion exchange have been investigated rather thoroughly and a considerable number of inorganic nanoparticles and nano-structures have been synthesized by this approach. Compared to cationic species, anionic diffusion rates in general are slower owing to their larger sizes. By selecting different diffusion pairs, variation in diffusivity has been utilized in creating a central void space for nanoparticles during the chemical transformation. The nanoscale Kir-kendall effect has been widely employed to generate interior voids for nanoparticles, and it has for example been recently exploited in the anion-exchange reactions between O~(2-) and S~(2-) anions. Apart from single-shelled hollow particles, the solution synthesis of multishelled functional materials is a fundamental challenge for synthetic chemistry owing to a significant increase in structural complexity. Indeed, this field of research has advanced rapidly in recent years. Nevertheless, there have been no reports to date on forming multishelled hollow spheres by employing an ion-exchange method, despite its great popularity in general transformation of nanomaterials. Herein, we exploited the capacity of the ionic exchange reaction for forming multishelled structures and found that with proper manipulation of a precursor system and thus reaction kinetics, a series of anionic exchanges with a solid precursor can actually be conducted in a consecutive manner, which leads to formation of single-, double-, triple-, or even quadruple shells. More specifically, as shown in Figure 1, we will use a hybrid of cuprous oxide (cuprites, a p-type metal oxide) and polyvinylpyrrolidone) (PVP) as a precursor solid to establish some general principles in controlling ionic exchange and the hollowing process for fabrication of complex multishelled Cu2S (chal-cocite) hollow spheres.