Photo-oxidation of Graphene in the Presence of Water

Oxygen molecules are found to exhibit nonnegligible reactivity with graphene under strong light irradiation in the presence of water. The reaction is triggered by the laser Raman spectroscopy measurement itself, and the D band (ca. 1340 cm^–1) becomes larger as the laser irradiation is prolonged. The electronic transport properties of the graphene derivative are also investigated and both the electron and hole mobility are found to be reduced. These results are attributed to oxidation of graphene. This primitive modification method can be exploited to manipulate the structural and electronic properties of graphene

Electron and Hole Injection via Charge Transfer at the Topological Insulator Bi_2–<i>x</i>Sb_<i>x</i>Te_3–<i>y</i>Se_<i>y</i>–Organic Molecule Interface

As a methodology for controlling the carrier transport of topological insulators (TIs), a flexible tuning in carrier number on the surface states (SSs) of three-dimensional TIs by surface modifications using organic molecules is described. The principle of the carrier tuning and its type conversion of TIs presented in this research are based on the charge transfer of holes or electrons at the TI–organic molecule interface. When 2,3,5,6-tetra­fluoro-7,7,8,8-tetra­cyano­quino­di­methane (F4-TCNQ) as an electron acceptor or tetra­cyano­quino­di­methane (TCNQ) as a donor is employed for n- and p-Bi_2–<i>x</i>Sb_<i>x</i>Te_3–<i>y</i>Se_<i>y</i> (BSTS) single crystals, successful carrier conversion from n- to p-type and its reverse mode is demonstrated depending on the electron affinities of the molecules. The present method provides a nondestructive and efficient method for local tuning in carrier density of TIs and is useful for future applications