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The electrochemical synthesis of polyaniline on stainless steel and its corrosion performance
?zyılmaz,M. Erbil,B. Yazıcı 한국물리학회 2006 Current Applied Physics Vol.6 No.1
Polyaniline (PANI) coatings were synthesized on stainless steel electrode by applying two different scan rates (10 and 50mVs1) in 0.1M aniline containing 0.3M oxalic acid solution. The synthesized polymer films were strongly adherent and homogenous in both cases. The corrosion performances of polyaniline coatings were investigated in 0.1M HCl solution, by using electrochemical impedance spectroscopy. Also, the open circuit potential–time (Eocp–t) diagrams were used. It was shown the polymer film deposited at low scan rate exhibited a better barrier property than the polymer film produced high scan rate. The PANI film coated at low scan rate provided important protection to stainless steel for longer periods, in such aggressive medium. Also, it was found out that the polymer film coated at low scan rate decreased the corrosion rate, by its catalytic behaviour on formation of ferric and chromium oxide layers.
Graphene-P(VDF-TrFE) Multilayer Film for Flexible Applications
Bae, Sang-Hoon,Kahya, Orhan,Sharma, Bhupendra K.,Kwon, Junggou,Cho, Hyoung J.,Ö,zyilmaz, Barbaros,Ahn, Jong-Hyun American Chemical Society 2013 ACS NANO Vol.7 No.4
<P>A flexible, transparent acoustic actuator and nanogenerator based on graphene/P(VDF-TrFE)/graphene multilayer film is demonstrated. P(VDF-TrFE) is used as an effective doping layer for graphene and contributes significantly to decreasing the sheet resistance of graphene to 188 ohm/sq. The potentiality of graphene/P(VDF-TrFE)/graphene multilayer film is realized in fabricating transparent, flexible acoustic devices and nanogenerators to represent its functionality. The acoustic actuator shows good performance and sensitivity over a broad range of frequency. The output voltage and the current density of the nanogenerator are estimated to be similar to 3 V and similar to 0.37 mu Acm(-2), respectively, upon the application of pressure. These values are comparable to those reported earlier for Zn0- and PIT-based nanogenerators. Finally, the possibility of rollable devices based on graphene/P(VDF-TrfE)/graphene structure is also demonstrated under a dynamic mechanical loading condition.</P>
Roll-to-roll production of 30-inch graphene films for transparent electrodes
Bae, Sukang,Kim, Hyeongkeun,Lee, Youngbin,Xu, Xiangfan,Park, Jae-Sung,Zheng, Yi,Balakrishnan, Jayakumar,Lei, Tian,Ri Kim, Hye,Song, Young Il,Kim, Young-Jin,Kim, Kwang S.,Ö,zyilmaz, Barbaros,Ahn, J Springer Science and Business Media LLC 2010 Nature nanotechnology Vol.5 No.8
Property Control of Graphene by Employing “Semi‐Ionic” Liquid Fluorination
Lee, Jong Hak,Koon, Gavin Kok Wai,Shin, Dong Wook,Fedorov, V. E.,Choi, Jae‐,Young,Yoo, Ji‐,Beom,Ö,zyilmaz, Barbaros WILEY‐VCH Verlag 2013 Advanced functional materials Vol.23 No.26
<P><B>Abstract</B></P><P>Semi‐ionically fluorinated graphene (s‐FG) is synthesized with a one step liquid fluorination treatment. The s‐FG consists of two different types of bonds, namely a covalent C‐F bond and an ionic C‐F bond. Control is achieved over the properties of s‐FG by selectively eliminating ionic C‐F bonds from the as prepared s‐FG film which is highly insulating (current < 10<SUP>−13</SUP> A at 1 V). After selective elimination of ionic C‐F bonds by acetone treatment, s‐FG recovers the highly conductive property of graphene. A 10<SUP>9</SUP> times increase in current from 10<SUP>−13</SUP> to 10<SUP>−4</SUP>A at 1 V is achieved, which indicates that s‐FG recovers its conducting property. The properties of reduced s‐FG vary according to the number of layers and the single layer reduced s‐FG has mobility of more than 6000 cm<SUP>2</SUP> V<SUP>−1</SUP> s<SUP>−1</SUP>. The mobility drastically decreases with increasing number of layers. The bi‐layered s‐FG has a mobility of 141cm<SUP>2</SUP> V<SUP>−1</SUP> s<SUP>−1</SUP> and multi‐layered s‐FG film showed highly p‐type doped electrical property without Dirac point. The reduction via acetone proceeds as 2C<SUB>2</SUB>F<SUB>(semi‐ionic)</SUB> + CH<SUB>3</SUB>C(O)CH<SUB>3(l)</SUB> → HF + 2C<SUB>(s)</SUB> + C<SUB>2</SUB>F<SUB>(covalent)</SUB> + CH<SUB>3</SUB>C(O)CH<SUB>2(l)</SUB>. The fluorination and reduction processes permit the safe and facile non‐destructive property control of the s‐FG film.</P>
Graphene for Controlled and Accelerated Osteogenic Differentiation of Human Mesenchymal Stem Cells
Nayak, Tapas R.,Andersen, Henrik,Makam, Venkata S.,Khaw, Clement,Bae, Sukang,Xu, Xiangfan,Ee, Pui-Lai R.,Ahn, Jong-Hyun,Hong, Byung Hee,Pastorin, Giorgia,Ö,zyilmaz, Barbaros American Chemical Society 2011 ACS NANO Vol.5 No.6
<P>Current tissue engineering approaches combine different scaffold materials with living cells to provide biological substitutes that can repair and eventually improve tissue functions. Both natural and synthetic materials have been fabricated for transplantation of stem cells and their specific differentiation into muscles, bones, and cartilages. One of the key objectives for bone regeneration therapy to be successful is to direct stem cells’ proliferation and to accelerate their differentiation in a controlled manner through the use of growth factors and osteogenic inducers. Here we show that graphene provides a promising biocompatible scaffold that does not hamper the proliferation of human mesenchymal stem cells (hMSCs) and accelerates their specific differentiation into bone cells. The differentiation rate is comparable to the one achieved with common growth factors, demonstrating graphene’s potential for stem cell research.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/ancac3/2011/ancac3.2011.5.issue-6/nn200500h/production/images/medium/nn-2011-00500h_0004.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/nn200500h'>ACS Electronic Supporting Info</A></P>
Ni, Guang-Xin,Zheng, Yi,Bae, Sukang,Kim, Hye Ri,Pachoud, Alexandre,Kim, Young Soo,Tan, Chang-Ling,Im, Danho,Ahn, Jong-Hyun,Hong, Byung Hee,Ö,zyilmaz, Barbaros American Chemical Society 2012 ACS NANO Vol.6 No.2
<P>The technical breakthrough in synthesizing graphene by chemical vapor deposition methods (CVD) has opened up enormous opportunities for large-scale device applications. To improve the electrical properties of CVD graphene grown on copper (Cu-CVD graphene), recent efforts have focused on increasing the grain size of such polycrystalline graphene films to 100 μm and larger. While an increase in grain size and, hence, a decrease of grain boundary density is expected to greatly enhance the device performance, here we show that the charge mobility and sheet resistance of Cu-CVD graphene is already limited within a single grain. We find that the current high-temperature growth and wet transfer methods of CVD graphene result in quasi-periodic nanoripple arrays (NRAs). Electron-flexural phonon scattering in such partially suspended graphene devices introduces anisotropic charge transport and sets limits to both the highest possible charge mobility and lowest possible sheet resistance values. Our findings provide guidance for further improving the CVD graphene growth and transfer process.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/ancac3/2012/ancac3.2012.6.issue-2/nn203775x/production/images/medium/nn-2011-03775x_0005.eps'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/nn203775x'>ACS Electronic Supporting Info</A></P>
Graphene–Ferroelectric Hybrid Structure for Flexible Transparent Electrodes
Ni, Guang-Xin,Zheng, Yi,Bae, Sukang,Tan, Chin Yaw,Kahya, Orhan,Wu, Jing,Hong, Byung Hee,Yao, Kui,Ö,zyilmaz, Barbaros American Chemical Society 2012 ACS NANO Vol.6 No.5
<P>Graphene has exceptional optical, mechanical, and electrical properties, making it an emerging material for novel optoelectronics, photonics, and flexible transparent electrode applications. However, the relatively high sheet resistance of graphene is a major constraint for many of these applications. Here we propose a new approach to achieve low sheet resistance in large-scale CVD monolayer graphene using nonvolatile ferroelectric polymer gating. In this hybrid structure, large-scale graphene is heavily doped up to 3 × 10<SUP>13</SUP> cm<SUP>–2</SUP> by nonvolatile ferroelectric dipoles, yielding a low sheet resistance of 120 Ω/□ at ambient conditions. The graphene–ferroelectric transparent conductors (GFeTCs) exhibit more than 95% transmittance from the visible to the near-infrared range owing to the highly transparent nature of the ferroelectric polymer. Together with its excellent mechanical flexibility, chemical inertness, and the simple fabrication process of ferroelectric polymers, the proposed GFeTCs represent a new route toward large-scale graphene-based transparent electrodes and optoelectronics.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/ancac3/2012/ancac3.2012.6.issue-5/nn3010137/production/images/medium/nn-2012-010137_0008.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/nn3010137'>ACS Electronic Supporting Info</A></P>
Toward Wafer Scale Fabrication of Graphene Based Spin Valve Devices
Avsar, Ahmet,Yang, Tsung-Yeh,Bae, Sukang,Balakrishnan, Jayakumar,Volmer, Frank,Jaiswal, Manu,Yi, Zheng,Ali, Syed Rizwan,Gü,ntherodt, Gernot,Hong, Byung Hee,Beschoten, Bernd,Ö,zyilmaz, Barb American Chemical Society 2011 Nano letters Vol.11 No.6
<P>We demonstrate injection, transport, and detection of spins in spin valve arrays patterned in both copper based chemical vapor deposition (Cu-CVD) synthesized wafer scale single layer and bilayer graphene. We observe spin relaxation times comparable to those reported for exfoliated graphene samples demonstrating that chemical vapor deposition specific structural differences such as nanoripples do not limit spin transport in the present samples. Our observations make Cu-CVD graphene a promising material of choice for large scale spintronic applications.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/nalefd/2011/nalefd.2011.11.issue-6/nl200714q/production/images/medium/nl-2011-00714q_0001.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/nl200714q'>ACS Electronic Supporting Info</A></P>
Ultrathin Organic Solar Cells with Graphene Doped by Ferroelectric Polarization
Kim, Keumok,Bae, Sang-Hoon,Toh, Chee Tat,Kim, Hobeom,Cho, Jeong Ho,Whang, Dongmok,Lee, Tae-Woo,Ö,zyilmaz, Barbaros,Ahn, Jong-Hyun American Chemical Society 2014 ACS APPLIED MATERIALS & INTERFACES Vol.6 No.5
<P>Graphene has been employed as transparent electrodes in organic solar cells (OSCs) because of its good physical and optical properties. However, the electrical conductivity of graphene films synthesized by chemical vapor deposition (CVD) is still inferior to that of conventional indium tin oxide (ITO) electrodes of comparable transparency, resulting in a lower performance of OSCs. Here, we report an effective method to improve the performance and long-term stability of graphene-based OSCs using electrostatically doped graphene films via a ferroelectric polymer. The sheet resistance of electrostatically doped few layer graphene films was reduced to ∼70 Ω/sq at 87% optical transmittance. Such graphene-based OSCs exhibit an efficiency of 2.07% with a superior stability when compared to chemically doped graphene-based OSCs. Furthermore, OSCs constructed on ultrathin ferroelectric film as a substrate of only a few micrometers show extremely good mechanical flexibility and durability and can be rolled up into a cylinder with 7 mm diameter.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/aamick/2014/aamick.2014.6.issue-5/am405270y/production/images/medium/am-2013-05270y_0007.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/am405270y'>ACS Electronic Supporting Info</A></P>