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Rapid Identification of the Layer Number of Large-Area Graphene on Copper
Qi, Zhikai,Zhu, Xudong,Jin, Hongchang,Zhang, Tiezhu,Kong, Xianghua,Ruoff, Rodney S.,Qiao, Zhenhua,Ji, Hengxing American Chemical Society 2018 Chemistry of materials Vol.30 No.6
<P>Chemical vapor deposition (CVD) on Cu foils emerged as an important method for preparing high-quality and large-area graphene films for practical applications. However, to date it remains challenging to rapidly identify the structural features, especially the layer numbers, of CVD-graphene directly on Cu substrate. Herein, we report an O<SUB>2</SUB>-plasma-assisted approach for identifying the coverage, wrinkles, domain size, and layer number of large-area graphene films on Cu foils by optical microscopy. The wrinkles and grain boundaries of five-layer graphene can be observed with a grayscale increment of ∼23.4% per one graphene layer after O<SUB>2</SUB>-plasma treatment for only 15 s, which allows for checking graphene on Cu foils with a sample size of 17 cm × 20 cm in a few minutes. The Raman spectroscopy and X-ray photoelectron spectroscopy presents a strong layer number dependence of both the plasma induced graphene defects and Cu oxides, which, as indicated by molecular dynamic simulation, is responsible for the improved image contrast as a result of the interaction between O-ions and graphene with different layer numbers. We expect that this O<SUB>2</SUB>-plasma-assisted method would be applied to meter-scale samples if atmospheric-pressure plasma is used and therefore will be beneficial for the fast evaluation of CVD-graphene in both laboratory and industry.</P> [FIG OMISSION]</BR>
Qi, Zhikai,Shi, Haohao,Zhao, Mingxing,Jin, Hongchang,Jin, Song,Kong, Xianghua,Ruoff, Rodney S.,Qin, Shengyong,Xue, Jiamin,Ji, Hengxing American Chemical Society 2018 Chemistry of materials Vol.30 No.21
<P>Bernal-stacked bilayer graphene is uniquely suited for application in electronic and photonic devices because of its tunable band structure. Even though chemical vapor deposition (CVD) is considered to be the method of choice to grow bilayer graphene, the direct synthesis of high-quality, large-area Bernal-stacked bilayer graphene on Cu foils is complicated by overcoming the self-limiting nature of graphene growth on Cu. Here, we report a facile H<SUB>2</SUB>O-assisted CVD process to grow bilayer graphene on Cu foils, where graphene growth is controlled by injecting intermittent pulses of H<SUB>2</SUB>O vapor using a pulse valve. By optimizing CVD process parameters fully covered large area graphene with bilayer coverage of 77 ± 3.6% and high AB stacking ratio of 93 ± 3% can be directly obtained on Cu foils, which presents a hole concentration and mobility of 4.5 × 10<SUP>12</SUP> cm<SUP>-2</SUP> and 1100 cm<SUP>2</SUP> V<SUP>-1</SUP> s<SUP>-1</SUP>, respectively, at room temperature. The H<SUB>2</SUB>O selectively etches graphene edges without damaging graphene facets, which slows down the growth of the top layer and improves the nucleation and growth of a second graphene layer. Results from our work are important both for the industrial applications of bilayer graphene and to elucidate the growth mechanism of CVD-graphene.</P> [FIG OMISSION]</BR>
Tang, Lijun,Zhou, Pei,Qi, Zhikai,Huang, Zhenlong,Zhao, Jia,Cai, Mingjun Korean Chemical Society 2013 Bulletin of the Korean Chemical Society Vol.34 No.8
A new quinoline-based acylhydrazone (1) has been synthesized and applied as a fluorescent probe. Probe 1 exhibits high selectivity and sensitivity to $Cu^{2+}$ with fluorescence "ON-OFF" behavior in HEPES buffered (1‰ DMSO, HEPES 20 mM, pH = 7.4) solution. The on-site generated 1-$Cu^{2+}$ complex displays excellent selectivity to sulfide ions with fluorescence "OFF-ON" performance through copper displacement approach.
Li-Jun Tang,Pei Zhou,Zhikai Qi,Zhenlong Huang,Jia Zhao,Mingjun Cai 대한화학회 2013 Bulletin of the Korean Chemical Society Vol.34 No.8
A new quinoline-based acylhydrazone (1) has been synthesized and applied as a fluorescent probe. Probe 1 exhibits high selectivity and sensitivity to Cu2+ with fluorescence “ON-OFF” behavior in HEPES buffered (1‰ DMSO, HEPES 20 mM, pH = 7.4) solution. The on-site generated 1-Cu2+ complex displays excellent selectivity to sulfide ions with fluorescence “OFF-ON” performance through copper displacement approach.