Facile diamond synthesis from lower diamondoids

Carbon-based nanomaterials have exceptional properties that make them attractive for a variety of technological applications. In this talk, I discuss the use of diamondoids (diamond-like hydrocarbons) as promising precursors for laser-induced high-pressure, high-temperature diamond synthesis. The lowest pressure and temperature (P-T) conditions that yielded diamond were 12 GPa (at ~2000 K) and 900 K (at ~20 GPa), respectively. This represents a significantly reduced transformation barrier compared with diamond synthesis from conventional (hydro)carbon allotropes. At 20 GPa, diamondoid-to-diamond conversion occurs rapidly within < 19 us, forming diamond in a range of sizes ~tens of nm to ~4 um crystals, depending on the synthesis conditions. Molecular dynamics simulations indicate that once dehydrogenated, the remaining diamondoid carbon cages reconstruct themselves into diamond-like structures at high P-T. The surprisingly low P-T regime necessary to grow diamond from diamondoids is attributed to the similarities in the structure and bonding of diamondoids and bulk diamond. This study is the first successful mapping of the P-T conditions and onset timing of the diamondoid-to-diamond conversion and elucidates the physical and chemical factors that facilitate diamond synthesis.