Liang Changhao and Liu Jun, associate researchers, Institute of solid state, Chinese Academy of Sciences, have made progress in the synthesis of carbon coated transition metal nanoparticles

Recently, Liang Changhao and Liu Jun, associate researchers of the Institute of solid state physics, Chinese Academy of Sciences, have made progress in the synthesis of carbon coated transition metal based nanoparticles, and the relevant results were published in ACS applied nano materials (DOI: 10.1021 / acsanm 8b01541) In recent years, carbon coated nanomaterials have attracted more and more attention due to their unique physical and chemical properties, which are widely used in magnetic data storage, electrocatalysis, bioengineering and other fields Therefore, it is of great significance to develop a simple, effective, moderate and controllable universal method to prepare carbon coated transition metal nano materials with uniform size Laser ablation of metal targets in organic solvents has been proved to be an effective new method for the synthesis of carbon coated nano materials This is because the formation of carbon coated nano materials is promoted by the local high temperature and pressure environment formed on the target surface during laser ablation However, the factors that affect the "core" composition of carbon coated transition metal based nanomaterials and the evolution of carbon layer during laser ablation are still not known Based on this, Liang Changhao and Liu Jun, associate researchers of the Institute of solid state, selected different metals (M = Cu, Ag, Au, PD, Pt, Ti, V, Nb, Cr, Mo, W, Ni, Zr, Mn, Fe and Zn) targets with acetone as organic solvent, and successfully prepared a series of targets according to the affinity of metal and oxygen and the different solubility of carbon in metal Carbon coated metal (M @ C), carbon coated metal carbide (McX @ C) and carbon coated metal oxide (Moy @ C) The affinity of inert metals (M = Cu, Ag, Au, PD, Pt, etc.) with oxygen is very low, and the solubility of carbon in these metals is relatively low, so the final product is carbon coated metal (M @ C) nanoparticles However, for the metals (M = Ti, V, Nb, Cr, Mo, W, Ni, Zr, etc.) in which the solubility of carbon is high and the metal carbon bond energy is high, the final products are mainly carbon coated metal carbides (McX @ C) Among them, ZrO2 has higher stability than ZrC, for Zr metal, the final product contains a small amount of ZrO2; for Ni metal, because the metastable phase ni3c formed is easy to decompose into a single substance Ni, the final product contains a single substance Ni In addition, for Zn, Mn, Fe and other metals, due to their low carbon solubility and easy to combine with oxygen, they will eventually form carbon coated metal / metal oxide nanoparticles (M @ C / Moy @ C) In addition, the researchers found that the crystallinity of the carbon layer was related to the metal target, and the second irradiation of the ablation process would also have an important impact on the crystallinity of the carbon layer In order to further study the evolution process of carbon layer, Pt metal was selected as the research object Firstly, Pt target was melted in water, Pt nanoparticles were obtained, and then re dispersed into acetone for irradiation Because Pt metal can catalyze the decomposition of acetone to form carbon under laser irradiation, after 15 minutes of irradiation, the researchers found that carbon layer was formed on the surface of particles When the irradiation time was increased to one hour, the carbon layer became thicker and the crystallinity was greatly improved, which indicated that the catalysis of metal also played an important role in the formation of carbon layer The related work provides an important reference for the preparation of carbon coated metal matrix materials and the understanding of its formation mechanism This work has been supported by the national key basic research and development plan (973 project) of the Ministry of science and technology, the equipment development project of the Chinese Academy of Sciences, the National Natural Science Foundation and the international cooperation plan of innovation team.