Romana Mikšová

Insight into the Mechanism of the Thermal Reduction of Graphite Oxide: Deuterium-Labeled Graphite Oxide Is the Key

For the past decade, researchers have been trying to understand the mechanism of the thermal reduction of graphite oxide. Because deuterium is widely used as a marker in various organic reactions, we wondered if deuterium-labeled graphite oxide could be the key to fully understand this mechanism. Graphite oxides were prepared by the Hofmann, Hummers, Staudenmaier, and Brodie methods, and a deuterium-labeled analogue was synthesized by the Hofmann method. All graphite oxides were analyzed not only using the traditional techniques but also by gas chromatography-mass spectrometry (GC-MS) during exfoliation in hydrogen and nitrogen atmospheres. GC-MS enabled us to compare differences between the chemical compositions of the organic exfoliation products formed during the thermal reduction of these graphite oxides. Nuclear analytical methods (Rutherford backscattering spectroscopy, elastic recoil detection analysis) were used to calculate the concentrations of light elements, including the ratio of hydrogen to deuterium. Combining all of these results we were able to determine graphite oxides thermal reduction mechanism. Carbon dioxide, carbon monoxide, and water are formed from the thermal reduction of graphite oxide. This process is also accompanied by various radical reactions that lead to the formation of a large amount of carcinogenic volatile organic compounds, and this will have major safety implications for the mass production of graphene.

Use of deuterium labelling—evidence of graphene hydrogenation by reduction of graphite oxide using aluminium in sodium hydroxide

Highly hydrogenated graphene is one of the main focuses in graphene research. Hydrogenated graphene may have many unique properties such as fluorescence, ferromagnetism, and a tuneable band gap. The most widely used techniques for the fabrication of highly hydrogenated graphene are based on technically challenging methods concerning the usage of liquid ammonia reduction pathways with alkali metals or plasma hydrogenation. However, the reduction of graphene oxide by nascent hydrogen is a simple and effective method leading to the formation of highly hydrogenated graphene at room temperature. Using deuterium labelling, we studied the hydrogenation of graphene oxides prepared by chlorate and permanganate methods. The nascent hydrogen/deuterium was formed by the reaction of aluminum powder with a solution of sodium deuteroxide in deuterated water. The synthesis of hydrogenated graphene was confirmed and it was characterized in detail.

Comparison of SIMS and RBS for depth profiling of silica glasses implanted with metal ions

Ion implantation of metal ions, followed by annealing, can be used for the formation of buried layers of metal nanoparticles in glasses. Thus, photonic structures with nonlinear optical properties can be formed. In this study, three samples of silica glasses were implanted with Cu+, Ag+, or Au+ ions under the same conditions (energy 330 keV and fluence 1 × 1016 ions/cm2), and compared to three identical silica glass samples that were subsequently coimplanted with oxygen at the same depth. All the implanted glasses were annealed at 600 °C for 1 h, which leads to the formation of metal nanoparticles. The depth profiles of Cu, Ag, and Au were measured by Rutherford backscattering and by secondary ion mass spectrometry and the results are compared and discussed.