Hydrogen-terminated graphene by laser vaporization-controlled condensation of graphite oxide. Observation of hydrogen-capped carbon chains C nH-, CnH+, and CnH 2+ (n = 2-30) in the gas phase

Abstract

We report the development of a facile process for the synthesis of hydrogen-terminated graphene using the laser vaporization-controlled condensation (LVCC) method. The method allows rapid deoxygenation of bulk graphite oxide (GO) in an atmosphere of helium or a helium-hydrogen mixture to produce hydrogen-terminated graphene (HTG) nanosheets without the need for any chemical reducing agents or solvents. Direct laser vaporization/ionization (LVI) of bulk GO in a vacuum coupled with a beam expansion of a carrier gas produces the carbon cluster series Cn with n in the range 4-30, in addition to hydrogenated carbon ions with a significant enhancement in the ion intensity of the n-even ions suggesting the formation of hydrogen-capped polyyne chains corresponding to the H-(Cî - C)n-H+ and H-(Cî - C)n- formulas. In contrast, LVI of bulk graphite under identical experimental conditions generates mainly the carbon cluster series Cn without any significant hydrogenation in both the positive and negative ion modes. The results confirm that the LVCC method of bulk GO produces HTG nanosheets which can be ionized and dissociated in a vacuum to produce the observed hydrogen-capped polyyne chains. These species could be deposited from the gas phase to form one-dimensional conducting molecular wires for a variety of potential applications in nanoelectronics, sensors, and devices. © 2013 American Chemical Society.