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n-Doping of Single-walled Carbon Nanotubes Using Pyridine-boryl Radicals
Naoki Tanaka,Aoi Hamasuna,Tsuyohiko Fujigaya 한국고분자학회 2021 한국고분자학회 학술대회 연구논문 초록집 Vol.46 No.2
The chemical doping of single-walled carbon nanotubes (SWCNTs) using electron donor and acceptor molecules is a crucial step for controlling the frontier orbital energy gap of SWCNTs. This means that SWCNTs are a promising material for electronics applications such as thermoelectric conversion and thin-film transistors, due to their flexibility, stability and light weight. Among all chemical dopants, 2 organic dopants containing hetero atoms are important materials as they permit fine controllability of the doping level; they also provide stability due to the flexibility of their structural design. In this study, we found that pyridine-boryl (py-boryl) radicals serve as efficient electron-doping reagents for SWCNTs, in which the doping mechanism comprises electron transfer from the py-boryl radical to the SWCNT. The formation of a stable py-boryl cation is essential for efficient doping; the captodative effect of the py-boryl cation is important to this process.
Hiroto Miura,Yuki Motoishi,Naoki Tanaka,Tsuyohiko Fujigaya 한국고분자학회 2021 한국고분자학회 학술대회 연구논문 초록집 Vol.46 No.2
Trifluoromethanesulfonylimide-grafted polybenzimidazole (PBI-TFSI) was synthesized for proton exchange membrane (PEM) applications. Its proton conductivity was a) less dependent on humidity and b) higher than that of conventional fluorine-based PEM (Nafion) and propanesulfonicacid-grafted PBI (PBI-PS) at a relative humidity of 40%. The chemical structure of PBI-TFSI was investigated using 1H and 19F nuclear magnetic resonance and Fourier transform infrared spectroscopy. The membranes yielded good transparency, flexibility, and thermal stability up to 350 °C. Membranes with different side-chain grafting ratios were prepared, and the water uptake and hydration number of the PBI-TFSI membranes were lower than those of the PBI-PS membranes most likely because of the hydrophobicity of the side chain. The higher proton concentration provided by TFSI with stronger acidity than PS might be the reason for the higher proton conductivities of PBI-TFSI.
Gate-enhanced photocurrent of (6,5) single-walled carbon nanotube based field effect transistor
Park, Ki Hong,Lee, Seung-Hoon,Toshimitsu, Fumiyuki,Lee, Jihoon,Park, Sung Heum,Tsuyohiko, Fujigaya,Jang, Jae-Won Elsevier 2018 Carbon Vol.139 No.-
<P><B>Abstract</B></P> <P>A visible sensing field effect transistor (FET) with a channel length of 100 nm for individual (6,5) single-walled carbon nanotubes (SWCNTs) is fabricated via a selective sorting method using 9,9-dioctyfluorenyl-2,7-diyl–bipyridine (PFO–BPy) polymer. The FET of the (6,5) SWCNTs shows <I>p</I>-type behavior with hundreds of on-off ratios and on-state conductivity of 50 ± 4.0 (Ω m)<SUP>−1</SUP>. In addition, the photocurrent of the FET of the (6,5) SWCNTs in the visible range increases (maximum 200 times at 620 nm) with higher gate voltage. E<SUB>22</SUB> transition and PFO-BPy transition are observed in the FET of the (6,5) SWCNTs without application of a gate voltage. Interestingly, exciton-phonon coupled E<SUB>22</SUB> transition due to gate-doping (<I>p</I>-type), which has been reported in photoluminescence and absorption studies, is expected to occur in the photocurrent of the FET at negatively higher gate voltage (≤−4 V). In addition, the exciton-phonon coupled E<SUB>22</SUB> transition is prominently observable when carrier concentration by gate doping becomes approximately two-hundred sixty times (260 ± 43) larger than carrier concentration without application of a gate voltage. This demonstration would be useful for the development of SWCNT-based visible sensors with gate control in the SWCNT devices.</P>
Graphene oxide and laponite composite films with high oxygen-barrier properties.
Yoo, JongTae,Lee, Sang Bong,Lee, Chang Kee,Hwang, Sung Wook,Kim, ChaeRin,Fujigaya, Tsuyohiko,Nakashima, Naotoshi,Shim, Jin Kie RSC Pub 2014 Nanoscale Vol.6 No.18
<P>The design and fabrication of oxygen barrier films is important for both fundamental and industrial applications. We prepared three different thin films composed of graphene oxide (GO) and laponite (LN), a typical low cost inorganic clay, with the GO/LN volume ratios of 1.9/0.1, 1.7/0.3 and 1.5/0.5 together with a double layer film of the GO and LN. We found that the films with GO/LN = 1.9/0.1 and the double layers exhibited high oxygen barrier and oxygen transmission rate values that reached 0.55 and 0.37 cm(3) per m(2) per atm per day, respectively, which were much lower than those of the films prepared from the pure GO, only LN and GO/LN = 1.7/0.3 and 1.5/0.5. This study is important for the design and fabrication of a film from GO-based all inorganic nanomaterials for applications in gas-barrier membranes.</P>