Graphene transistors are insensitive to pH changes in solution

We observe very small gate-voltage shifts in the transfer characteristic of as-prepared graphene field-effect transistors (GFETs) when the pH of the buffer is changed. This observation is in strong contrast to Si-based ion-sensitive FETs. The low gate-shift of a GFET can be further reduced if the graphene surface is covered with a hydrophobic fluorobenzene layer. If a thin Al-oxide layer is applied instead, the opposite happens. This suggests that clean graphene does not sense the chemical potential of protons. A GFET can therefore be used as a reference electrode in an aqueous electrolyte. Our finding sheds light on the large variety of pH-induced gate shifts that have been published for GFETs in the recent literature

Spectroscopic ellipsometry on Si/SiO2/graphene tri-layer system exposed to downstream hydrogen plasma: Effects of hydrogenation and chemical sputtering

In this work, the optical response of graphene to hydrogen plasma treatment is investigated with spectroscopic ellipsometry measurements. Although the electronic transport properties and Raman spectrum of graphene change after plasma hydrogenation, ellipsometric parameters of the Si/SiO2/graphene tri-layer system do not change. This is attributed to plasma hydrogenated graphene still being electrically conductive, since the light absorption of conducting 2D materials does not depend on the electronic band structure. A change in the light transmission can only be observed when higher energy hydrogen ions (30 eV) are employed, which chemically sputter the graphene layer. An optical contrast is still apparent after sputtering due to the remaining traces of graphene and hydrocarbons on the surface. In brief, plasma treatment does not change the light transmission of graphene; and when it does, this is actually due to plasma damage rather than plasma hydrogenation. (C) 2015 AIP Publishing LLC

Selective oxidation of methane to methanol over Au/H-MOR

Selective oxidation of methane to methanol by molecular oxygen is a fascinating route for upgrading abundant methane resource and represents one of the most challenging reactions in chemistry due to the overwhelmingly higher reactivity of the product versus the reactant. Here, we report that monometallic gold nanoparticles loaded on mordenite zeolite efficiently catalyze the selective oxidation of methane to methanol by molecular oxygen in the presence of carbon monoxide in aqueous medium. The methanol productivity reaches 1300 μmol gcat−1 h−1 or 280 mmol gAu-1 h-1 with 75% selectivity at 150 °C, outperforming most of those reported under comparable conditions. Both hydroxyl radicals and hydroperoxide species participate in the activation and conversion of methane; the lower affinity of methanol on gold mainly accounts for higher methanol selectivity