THIS MONTH IN NPG ASIA MATERIALS

Volume 4, November 2012

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November 23 2012

Original Article

Tuning the properties of graphene using a reversible gas-phase reaction

Lin Gan, Jian Zhou, Fen Ke, Hang Gu, Danna Li, Zonghai Hu, Qiang Sun and Xuefeng Guo

NPG Asia Mater 4: e31; doi:10.1038/am.2012.58

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Graphene, owing to its remarkable electronic and structural properties, has attracted considerable attention in both science and technology communities. However, a major roadblock to the realization of graphene-based field-effect transistors is the fact that large-area graphene behaves like a semimetal with zero bandgap, making it unsuitable for real applications in sensing, detecting and switching systems. Surface functionalization could result in the construction of periodic micro/nanostructures by breaking sp2 bonds and forming sp3 bonds. Therefore, direct chemical grafting might provide a useful way to covalently modify graphene for tailoring its properties. Owing to the inert reactivity of its surface, however, up to date only few chemical reactions were used to modify its atomic structure. Here, we demonstrate a controllable and efficient means of mild plasma methylation to manipulate the reversible interconversion of two distinct species of graphene (one crystalline and the other methylated). The strategy of incorporating diverse functional substituents (methyl group and hydrogen atoms here) into graphene instead of a single type of chemical groups could provide a useful route for the development of different applications, such as chemical/biosensors and multifunctional electrical circuits. Moreover, the methylated graphene with fine tunability is stable at room temperature, which suggests the intrinsic potential of novel applications in graphene-based optoelectronic devices that invites further studies.

Subject Category: Organic, carbon-based and soft materials

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November 09 2012

Original Article

Realizing a SnO2-based ultraviolet light-emitting diode via breaking the dipole-forbidden rule

Yongfeng Li, Wanjian Yin, Rui Deng, Rui Chen, Jing Chen, Qingyu Yan, Bin Yao, Handong Sun, Su-Huai Wei and Tom Wu

NPG Asia Mater 4: e30; doi:10.1038/am.2012.56

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It is commonly believed that bulk SnO2 is not a suitable ultraviolet (UV) light emitter due to the dipole-forbidden nature of its band-edge states, which has hindered its potential use in optical applications. Here, we demonstrate both theoretically and experimentally an effective method to break the dipole-forbidden rule in SnO2 via nano-engineering its crystalline structure. Furthermore, we designed and fabricated a prototypical UV-light-emitting diode (LED) based on SnO2 thin films. Our methodology is transferable to other semiconductors with ‘forbidden’ energy gaps, offering a promising route toward adding new members to the family of light-emitting materials.

Subject Category: Optics, photonics and optoelectronics

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