Formation of Carbon-Carbon Interlinkage Bonds under High Pressure

The formation of carbon-carbon interlinkage bonds (CCIBs) via the chemical binding of interlayer carbon atoms of many sp²-bonded carbon precursors is an essential step for synthesizing various diamond and diamond-like materials. Although the existence of CCIBs may be reasonably assumed under high-pressure conditions, direct experimental evidence has been scarce. Micro-Raman spectroscopy is here employed to track in situ the evolution of C-C bonds in a pressure range from ambient to 54 GPa. A pressure-induced two-stage (polynomial and linear) shift of the G peak and new generation of the CCIB peak at about 1550 cm^-1 are observed in multiple types of layer-structured carbon precursors, including glassy carbon, natural graphite, and carbon nanotubes. The experimental discovery of CCIBs holds significance in comprehending phase transitions of sp²-bonded carbon materials and has implications for the advancement of novel carbon structures.