Partial 13C isotopic labeling of carbon Materials: Why ∼20-50 at% is sufficient

Abstract

Carbon-13 (C-13) isotopic labeling is a central experimental tool in carbon materials research, yet commercially available labeled carbon precursors are most often supplied at enrichment levels exceeding 99 at% C-13, at substantial cost. Here it is argued that, for a broad range of studies involving diamond, diamond-like carbon, graphite, graphene, carbon nanotubes, porous carbons, amorphous carbons, and mixed sp/sp(2) carbon networks, such extreme isotopic purity is frequently unnecessary. Instead, enrichment in the range of approximately similar to 20-50 at%-and in some cases even lower-often provides sufficient isotopic contrast to enable spectroscopic sensitivity, growth-mechanism discrimination, and carbon-source attribution. The analysis highlights why the scientific return of isotopic labeling saturates well below isotopic purity and why broader availability of partially enriched carbon feedstocks would benefit the carbon materials community.