Graphene-based nanomaterials have received significant attention in the last decade due to their interesting properties. Its electrical and thermal conductivity and strength make graphene well suited for a variety of applications, particularly for use as a composite material in plastics. Furthermore, much work is taking place to utilize graphene as a biomaterial for uses such as drug delivery and tissue regeneration scaffolds. Owing to the rapid progress of graphene and its potential in many marketplaces, the potential toxicity of these materials has garnered attention. Graphene, while simple in its purest form, can have many different chemical and physical properties. In this paper, we describe our toxicity evaluation of pristine graphene and a functionalized graphene sample that has been oxidized for enhanced hydrophilicity, which was synthesized from the pristine sample. The samples were characterized by X-ray photoelectron spectroscopy, Raman spectroscopy, infrared spectroscopy, thermogravimetric analysis, zeta-potential, atomic force microscopy and electron microscopy. We discuss the disagreement between the size of imaged samples analyzed by atomic force microscopy and by transmission electron microscopy. Furthermore, the samples each exhibit quite different surface chemistry and structure, which directly affects their interaction with aqueous environments and is important to consider when evaluating the toxicity of materials both in vitro and in vivo.

Conductivity of In0.38Ga0.62As quantum wires grown on the (311)A plane of GaAs was studied using temperature dependent Hall effect. Detailed analysis of the scattering phenomena which control electron mobility along the wires indicates that the most significant scattering mechanism which limits electron mobility at low temperatures is scattering from interface roughness. This finding contributes to the general understanding of the potential to use self-assembled semiconductor quantum wires in the fabrication of thermoelectric devices where one-dimensionality and enhanced scattering at rough boundaries are important.

The band offsets for the β-(Al 0.21 Ga 0.79 ) 2 O 3 /β-Ga 2 O 3 (010) heterojunction have been experimentally measured by X-ray photoelectron spectroscopy. High-quality β-(Al 0.21 Ga 0.79 ) 2 O 3 films were grown by metal−organic chemical vapor deposition for characterization. The indirect band gap of β-(Al 0.21 Ga 0.79 ) 2 O 3 was determined by optical transmission to be 4.69 ± 0.03 eV with a direct transition of 5.37 ± 0.03 eV, while β-Ga 2 O 3 was confirmed to have an indirect band gap of 4.52 ± 0.03 eV with a direct transition of 4.94 ± 0.03 eV. The resulting band alignment at the heterojunction was determined to be of type II with the valence and conduction band edges of β-(Al 0.21 Ga 0.79 ) 2 O 3 being −0.26 ± 0.08 and 0.43 ± 0.08 eV, respectively, above those of β-Ga 2 O 3 (010). These values can now be used to help better design and predict the performance of β-(Al x Ga 1−x ) 2 O 3 heterojunctionbased devices.

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