Carbon-Encapsulated Metal/Metal Carbide/Metal Oxide Core-Shell Nanostructures Generated by Laser Ablation of Metals in Organic Solvents

Laser ablation of metal in organic solvents (LAMOS) has been proven to be an efficient technique for one-step synthesis of carbon-encapsulated metal/metal carbide/metal oxide core-shell nanostructures. However, the correlation between the influential factors and the final products, such as composition of the core and crystalline structure of the carbon shell, is still unclear to date; moreover, the precise control of this is full of challenges. Herein, comparative experiments of 16 transition metals (Cu, Ag, Au, Pt, Pd, Ti, V, Nb, Cr, Mo, W, Ni, Zr, Mn, Fe, and Zn) were performed to clarify the panorama of LAMOS, including metal atomization and liquid decomposition into carbon and reductive gases, subsequent metal carbonization, surface precipitation, and metal-catalyzed graphitization to form amorphous and graphitic carbon shells. Importantly, it is found that the carbon solubility in metals and the affinity of metals to oxygen are the critical factors in determining the core composition: (1) inert metals Cu, Ag, Au, Pt, Pd are directly transformed into pure metal cores; (2) active metals Ti, V, Nb, Cr, Mo, W, Ni, Zr evolve into metal carbide cores, but Mn, Fe, and Zn give birth to the mixture of metal and metal oxides cores.