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Trung T.Q.,Sungkyunkwan University | Ramasundaram S.,Korea Institute of Science and Technology | Hong S.W.,Korea Institute of Science and Technology | Lee N.-E.,Sungkyunkwan University | And 2 more authors.
Advanced Functional Materials | Year: 2014

A new class of temperature-sensing materials is demonstrated along with their integration into transparent and flexible field-effect transistor (FET) temperature sensors with high thermal responsivity, stability, and reproducibility. The novelty of this particular type of temperature sensor is the incorporation of an R-GO/P(VDF-TrFE) nanocomposite channel as a sensing layer that is highly responsive to temperature, and is optically transparent and mechanically flexible. Furthermore, the nanocomposite sensing layer is easily coated onto flexible substrates for the fabrication of transparent and flexible FETs using a simple spin-coating method. The transparent and flexible nanocomposite FETs are capable of detecting an extremely small temperature change as small as 0.1 C and are highly responsive to human body temperature. Temperature responsivity and optical transmittance of transparent nanocomposite FETs were adjustable and tuneable by changing the thickness and R-GO concentration of the nanocomposite. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Xu J.,SKKU Advanced Institute of Nanotechnology SAINT | Xu J.,Center for Human Interface Nanotechnology | Jang S.K.,SKKU Advanced Institute of Nanotechnology SAINT | Jang S.K.,Center for Human Interface Nanotechnology | And 6 more authors.
Journal of Physical Chemistry C | Year: 2014

We report a new method for the codoping of boron and nitrogen in a monolayer graphene film. After the CVD synthesis of monolayer graphene, BN-doped graphene is prepared by performing power-controlled plasma treatment and thermal annealing with borazine. BN-doped graphene films with various doping levels, which were controlled by altering the plasma treatment power, were found with Raman and electrical measurements to investigate exhibit p-doping behavior. Transmission electron microscopy, electron energy loss spectroscopy, and X-ray photoelectron spectroscopy were used to demonstrate that the synthesized BN-doped graphene films have a sp2 hybridized hexagonal structure. This approach to tuning the distribution and doping levels of boron and nitrogen in monolayer sp2 hybridized BN-doped graphene is expected to be very useful for applications requiring large-area graphene with an opened band gap. © 2014 American Chemical Society.

Seo S.-W.,Sungkyunkwan University | Chae H.,Sungkyunkwan University | Seo S.J.,SKKU Advanced Institute of Nanotechnology SAINT | Chung H.K.,SKKU Advanced Institute of Nanotechnology SAINT | Cho S.M.,Sungkyunkwan University
Applied Physics Letters | Year: 2013

We report on an extremely bendable moisture barrier for the thin-film encapsulation of organic light-emitting diodes (OLEDs). Hybrid barriers with various dyads of alternating aluminum oxide (Al2O3) and plasma-polymerized layers, which are utilizable for the thin-film encapsulation of flexible OLEDs, were prepared by atomic layer deposition and plasma chemical vapor deposition, respectively. When the total thickness of Al2O 3 was fixed at 20 nm, an ultimate 200-dyad multilayer barrier showed change of less than 20 in water vapor transmission rate from its initial value of the order of 10-4 g/m2/day, even after 10 000 times of bending with a bending radius of 5 mm. © 2013 AIP Publishing LLC.

Park J.,Center for Superfunctional Materials | Lee W.H.,Pohang University of Science and Technology | Huh S.,Center for Superfunctional Materials | Sim S.H.,SKKU Advanced Institute of Nanotechnology SAINT | And 6 more authors.
Journal of Physical Chemistry Letters | Year: 2011

We have devised a method to optimize the performance of organic field-effect transistors (OFETs) by controlling the work functions of graphene electrodes by functionalizing the surface of SiO2 substrates with self-assembled monolayers (SAMs). The electron-donating NH2- terminated SAMs induce strong n-doping in graphene, whereas the CH 3-terminated SAMs neutralize the p-doping induced by SiO2 substrates, resulting in considerable changes in the work functions of graphene electrodes. This approach was successfully utilized to optimize electrical properties of graphene field-effect transistors and organic electronic devices using graphene electrodes. Considering the patternability and robustness of SAMs, this method would find numerous applications in graphene-based organic electronics and optoelectronic devices such as organic light-emitting diodes and organic photovoltaic devices. © 2011 American Chemical Society.

Lee C.,SKKU Advanced Institute of Nanotechnology SAINT | Baik S.,SKKU Advanced Institute of Nanotechnology SAINT
Carbon | Year: 2010

A membrane filter possessing both superhydrophobicity and superoleophilicity is of great interest for the possible separation of oil and water. Such a filter was realized in this study by synthesizing vertically-aligned multi-walled carbon nano-tubes on a stainless steel mesh. The dual-scale structure, nano-scale needle-like tubes on the mesh with micro-scale pores, combined with the low surface energy of carbon amplified both hydrophobicity and oleophilicity. For the tests, diesel was selected as a representative of low viscosity oils. The contact angles for diesel and water were 0° and 163 ± 4°. The nano-tube filter could separate diesel and water layers, and even surfactant-stabilized emulsions. The successful phase separation of the high viscosity lubricating oil and water emulsions was also carried out. The separation mechanism can be readily expanded to a variety of different hydrophobic and oleophilic liquids. The simple nano-tube filter might be practically employed in environmental and chemical separation processes including oil spill cleanup. © 2010 Elsevier Ltd. All rights reserved.

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