Atomic dopants involved in the structural evolution of thermally graphitized graphene.

Thermally doped nitrogen atoms on the sp(2)-carbon network of reduced graphene oxide (rGO) enhance its electrical conductivity. Atomic structural information of thermally annealed graphene oxide (GO) provides an understanding on how the heteroatomic doping could affect electronic property of rGO. Herein, the spectroscopic and microscopic variations during thermal graphitization from 573 to 1,373 K are reported in two different rGO sheets, prepared by thermal annealing of GO (rGO(therm)) and post-thermal annealing of chemically nitrogen-doped rGO (post-therm-rGO(N(2)H(4))). The spectroscopic transitions of rGO(N(2)H(4)) in thermal annealing ultimately showed new oxygen-functional groups, such as cyclic edge ethers and new graphitized nitrogen atoms at 1,373 K. During the graphitization process, the microscopic evolution resolved by scanning tunneling microscopy (STM) produced more wrinkled surface morphology with graphitized nanocrystalline domains due to atomic doping of nitrogen on a post-therm-rGO(N(2)H(4)) sheet. As a result, the post-therm-rGO(N(2)H(4))-containing nitrogen showed a less defected sp(2)-carbon network, resulting in enhanced conductivity, whereas the rGO(therm) sheet containing no nitrogen had large topological defects on the basal plane of the sp(2)-carbon network. Thus, our investigation of the structural evolution of original wrinkles on a GO sheet incorporated into the graphitized N-doped rGO helps to explain how the atomic doping can enhance the electrical conductivity.

n-Type reduced graphene oxide field-effect transistors (FETs) from photoactive metal oxides.

Graphene is of considerable interest as a next-generation semiconductor material to serve as a possible substitute for silicon. For real device applications with complete circuits, effective n-type graphene field effect transistors (FETs) capable of operating even under atmospheric conditions are necessary. In this study, we investigated n-type reduced graphene oxide (rGO) FETs of photoactive metal oxides, such as TiO(2) and ZnO. These metal oxide doped FETs showed slight n-type electric properties without irradiation. Under UV light these photoactive materials readily generated electrons and holes, and the generated electrons easily transferred to graphene channels. As a result, the graphene FET showed strong n-type electric behavior and its drain current was increased. These n-doping effects showed saturation curves and slowly returned back to their original state in darkness. Finally, the n-type rGO FET was also highly stable in air due to the use of highly resistant metal oxides and robust graphene as a channel.

A strategically designed porous iron-iron oxide matrix on graphene for heavy metal adsorption.

The iron oxide nanoparticles were transformed to a matrix of iron-iron oxide on the graphene surface at an elevated temperature in a H(2)/Ar atmosphere. The resultant iron-iron oxide dispersed graphene was highly porous, robust and attractive for a variety of potential applications.