Small-Scale Nanoparticles Pyrolyzed from Layered Hydrotalcite between Graphene Interlayers as Intermediates for Self-Assembly into Metal Oxide Nanosheets and Hollow Nanospheres

Although significant advances have been made in the synthesis of various two-dimensional (2D) nanomaterials, problems of inefficient and difficult to scale applications remain. Here, a novel strategy is reported for obtaining 2D nanosheets from the 2D interlayer space of a graphene oxide (GO) membrane through combustion, which provides a simple and rapid method for the fabrication of 2D nanosheets as well as hollow nanospheres. Layered hydrotalcite from metal nitrates is formed between GO interlayers, which can be pyrolyzed into small-sized oxide nanoparticles (3-5 nm) and then aggregated as intermediates into large-sized nanosheets by combustion with Co, Ni, and Cr nitrates. However, the oxide intermediates self-assemble into hollow oxide nanospheres for nitrates of more active Cd, Ce, and Eu. Moreover, the intermediates of inactive Ag, Pb, and Bi nitrates are reduced by GO into metal nanoparticles, which can fuse into Ag nanofiber network films, or Pb and Bi composite spheres because of their low melting point. This work is helpful to understand the nature of 2D space and develops a class of micro-scale reactors between graphene layers.