High pressure and high temperature induced polymerization of C60 quantum dots**Project supported by the National Key R&D Program of China (Grant No. 2018YFA0305900), the National Natural Science Foundation of China (Grant Nos. 11634004 and 11404036), “the 13th Five-year” Planning Project of Jilin Provincial Education Department Foundation, China (Grant No. 20190504), JLU Science and Technology Innovative Research Team, China (Grant No.

Abstract

We synthesized C60 quantum dots (QDs) with a uniform size by a modified ultrasonic process and studied its polymerization under high pressure and high temperature (HPHT). Raman spectra showed that a phase assemblage of a dimer (D) phase (62 vol%) and a one-dimensional chain orthorhombic (O) phase (38 vol%) was obtained at 1.5 GPa and 300 °C. At 2.0 GPa and 430 °C, the proportion of the O phase increased to 46 vol%, while the corresponding D phase decreased to 54 vol%. Compared with bulk and nanosized C60, C60 QDs cannot easily form a high-dimensional polymeric structure. This fact is probably caused by the small particle size, orientation of the disordered structure of C60 QDs, and the barrier of oxide function groups between C60 molecules. Our studies enhance the understanding of the polymerization behavior of low-dimension C60 nanomaterials under HPHT conditions.