Preparation Of Erbium-Containing Endohedral Metallofullerenes And Optimized Synthesis And Properties Of Their Micro/-Nano Structures

Endohedral metallofullerenes（EMFs）can be formed when the carbon cages of hollow fullerenes are incased with metal atoms or clusters,which can transfer charges to the carbon cages,usually giving EMFs some unique physical and chemical properties.In addition,assembling EMFs into the well-defined and uniform micro/-nano structures through the liquid-liquid interface precipitation（LLIP）method provides broad potential applications in the field of optoelectronic devices.At present,very few researches on EMFs containing Er and their micro/-nano structures.In this contribution,we explored the self-assembly behavior of Er-containing EMFs using the some kinds of the pre-synthesizes Er-containing EMFs for the first time,and then invetigated photoelectric properties of these self-assemblies.The main research conclusions are as follows:（1）A series of Er endohedral metallofullerenes were prepared by the direct-current arc discharge method,and samples of Er₃N@I_h-C₈₀,Er₂@C_s（6）-C₈₂ and Er₂@C_3v（8）-C₈₂ were separated by the high performance liquid chromatography.Moreover,Er₂O@C_s（6）-C₈₂ was isolated for the first time.The Er-O bond lengths in the non-linear cluster units in the cage are 1.972（?）and 1.864（?）,respectively,and the bond angle is 147.65°.In contrast,the bond angle of the Sc₂O unit in Sc₂O@C_s（6）-C₈₂ is 156.63°.It is speculated that the radius of erbium atoms is larger than that of scandium atoms.There are 18 disordered positions of erbium in Er₂O@C_s（6）-C₈₂,which are distributed along the continuous hexagonal band on the inner surface of fullerene,similar to Sc₂O@C_s（6）-C₈₂.（2）Using the LLIP method,a variety of self-assembled Er-containing EMFs micro/-nano structures with the uniform size and smooth surface were prepared under the different good/poor solvent systems and volume ratios.We discovered that the formation of these micro/-nano structures mainly depends on the good/poor solvent systems.When the good solvent is carbon disulfide,it is easy to obtain a regular two-dimensional flake structures and three-dimensional rhombic dodecahedral,whereas when the good solvent changes to m-xylene,one-dimensional nanorods or nanoneedles were usually formed.In addition,the ratio of good/poor solvents will affect the size of the micro/-nano structures,and the experimental temperature will affect the uniformity of the micro/-nano structures.（3）The isomers molecules of Er₂@C_s（6）-C₈₂ and Er₂@C_3v（8）-C₈₂ respctively self-assemble into the similar needle-like nanostructures with the identical crystalline form（face centered cubic structure）in the m-xylene/IPA combination,indicating that the type of isomers has little effect on the self-assembled behavior of the EMFs containing Er.In addition,Er₃N@I_h-C₈₀,Er₂@C_s（6）-C₈₂ and Er₂@C_3v（8）-C₈₂micro/-nano structures show broader and stronger light absorption in the near-infrared region due to their regular crystalline nature as compared with that of original EMFs powder.Furthermore,Er₂@C_s（6）-C₈₂ nano needles exhibit a significant photoluminescence enhancement as compared to that of original powder attributing to their high crytallnity,suggesting the potential applications as optoelectronic devices.