Large-scale production of carbon-coated copper nanoparticles for sensor applications.

Copper nanoparticles with a mean carbon coating of about 1 nm were continuously produced at up to 10 g h(-1) using a modified flame spray synthesis unit under highly reducing conditions. Raman spectroscopy and solid state (13)C magic angle spinning nuclear magnetic resonance spectroscopy revealed that the thin carbon layer consisted of a sp(2)-hybridized carbon modification in the form of graphene stacks. The carbon layer protected the copper nanoparticles from oxidation in air. Bulk pills of pressed carbon/copper nanoparticles displayed a highly pressure- and temperature-dependent electrical conductivity with sensitivity at least comparable to commercial materials. These properties suggest the use of thin carbon/copper nanocomposites as novel, low-cost sensor materials and offer a metal-based alternative to the currently used brittle oxidic spinels or perovskites.