Formation of nanodiamonds at near-ambient conditions via microplasma dissociation of ethanol vapour

Abstract

Clusters of diamond-phase carbon, known as nanodiamonds, exhibit novel mechanical, optical and biological properties that have elicited interest for a wide range of technological applications. Although diamond is predicted to be more stable than graphite at the nanoscale, extreme environments are typically used to produce nanodiamonds. Here we show that nanodiamonds can be stably formed in the gas phase at atmospheric pressure and neutral gas temperatures o100°C by dissociation of ethanol vapour in a novel microplasma process. Addition of hydrogen gas to the process allows in flight purification by selective etching of the non-diamond carbon and stabilization of the nanodiamonds. The nanodiamond particles are predominantly between 2 and 5 nm in diameter, and exhibit cubic diamond, n-diamond and lonsdaleite crystal structures, similar to nanodiamonds recovered from meteoritic residues. These results may help explain the origin of nanodiamonds in the cosmos, and offer a simple and inexpensive route for the production of high-purity nanodiamonds.

Quantifying the distribution of nanodiamonds in pre-Younger Dryas to recent age deposits along Bull Creek, Oklahoma Panhandle, USA

“…First, the n-diamond structure can be considered the same as the cubic structure, but with partial carbon occupancy, hydrogen substitutions, and/or defects that allow the electron diffraction position {200} reflections to appear. Indeed, n-diamonds can form in the laboratory under very similar conditions to those under which cubic diamonds form, including through CVD processes (53,54). CVD diamond growth has also been identified directly for diamonds associated with meteorites and presolar grains (49).…”

Nanodiamond-Rich Layer across Three Continents Consistent with Major Cosmic Impact at 12,800 Cal BP

“…Alternately, the rounded shapes may result from a different mode of formation. For example, subrounded to rounded commercial lonsdaleite has been produced by microplasma dissociation of ethanol vapor (Kumar et al 2013), under conditions somewhat similar to those in an impact event, i.e., anoxic atmosphere and a carbon source. Below, we describe some analyses used to characterize the lonsdaleite-like crystals.…”

Atmospheric pressure synthesis of diamondoids by plasmas generated inside a microfluidic reactor

“…For example, the rapid continuous gas phase growth of semiconductor nanowires has been demonstrated [28], and the growth speed and morphology were shown to be influenced by the flow rate and precursor size. In addition, continuous flow microplasma reactors operated at atmospheric pressure have been used for the synthesis of metallic nanoparticles [29,30] and nanodiamond [31].…”