Nitrogen-doped graphitic carbon synthesized by laser annealing of sumanenemonoone imine as a bowl-shaped π-conjugated molecule.-猫眼课题宝

DOI：

10.1002/asia.201300500

发表时间：

2013-07

期刊：

Chemistry, an Asian journal

影响因子：

通讯作者：

中科院分区：

其他

文献类型：

作者：

Yuhi Inada;T. Amaya;Yasutomo Shimizu;A. Saeki;T. Otsuka;Ryotaro Tsuji;S. Seki;T. Hirao

氮掺杂石墨碳（NGC，图1a）由于其电学和催化性能而引起了人们的极大兴趣，从而对其潜在应用做出了重大贡献。[1-14]最近，许多研究人员揭示了影响其有效性的关键因素之一是石墨晶格中氮原子的键合模式。[4，15-18]然而，氮与碳的组成比（N/C）也是一个关键参数，因为掺杂的氮原子的量决定了性能。允许合理控制的合成方法使材料的设计更有效，从而提供容易的调节和性能的增强。所得NGC的N/C比在大多数先前报道的合成中受到控制，包括直接合成如基于化学气相沉积（CVD）的[6，19，20]分离[21]和电弧放电[1，22，23]方法，以及后合成如热[24-27]等离子体[8，10，28，29]肼还原[30，31]或激光[32]处理石墨烯、氧化石墨烯（GO）或具有各种氮源的石墨。然而，有必要调整多个参数，通过实验确定，以控制N/C比。因此，我们采用了一种方法，将具有固定N/C比的含氮碳基化合物（作为起始材料）转化为NGC，其中N/C比不变。形成NGC的石墨骨架通常通过使用炉[12，13，33-44]或激光处理的热解来进行。虽然碳化通常随着温度的升高而进行，但当加热到600- 800 ℃以上时，大多数氮原子在该过程中减少。因此，为了提高碳化程度并抑制氮原子的损失，必须设计有利于碳化的体系。[50]碗状化合物（以下称为“π碗”）[51]属于非平面π共轭化合物，也引起了人们的极大兴趣。[52-55] π碗被表示为富勒烯的部分结构，包括sumanene（1，C21 H12，图1b），[56] corannulene（C20 H10），[57]等等。与富勒烯和碳纳米管相比，π碗的研究有限。因此，我们一直在积极研究苏曼烯化学，以显示π碗的潜在特征。[49π碗的特征之一是归因于非平面π共轭形状的应变（图1c）。由于应变，我们预期与平面键相比，1的C2 H2O C键容易断裂，这可能支持碳化。此外，如上所述，已知激光是由于其光热效应而能够局部促进碳化的加热源之一，从而允许靶以位置选择性被快速加热。因此，这种方法被认为是有吸引力的潜在应用，如在电子设备。对于其他非平面π共轭化合物，已经报道了富勒烯C60的激光诱导电导率增加。[59-62]如果是单层-

Nitrogen-doped graphitic carbons (NGCs, Figure 1a) have attracted much interest owing to their electrical and catalytic properties, thus leading to significant contributions toward their potential applications.[1–14] Recently, many researchers have revealed one of the critical factors influencing their effectivities to be the bonding pattern of nitrogen atoms in the graphitic lattice.[4, 15–18] However, the composition ratio of nitrogen-to-carbon (N/C) is also a crucial parameter as the amount of doped nitrogen atoms determines the properties. Synthetic methods that allow rational control make the design of materials more efficient, thereby providing facile modulation and enhancement of the performance. The N/C ratio of the resulting NGC is controlled in most of the previously-reported syntheses, including direct synthesis such as chemical vapor deposition (CVD)-based,[6, 19, 20] segregation,[21] and arc-discharge [1, 22, 23] methods, and postsynthesis such as thermal,[24–27] plasma,[8, 10, 28, 29] hydrazine reduction,[30, 31] or laser [32] treatment of graphene, graphene oxide (GO), or graphite with various nitrogen sources. However, it is necessary to adjust multiple parameters, determined by experiments, to control the N/C ratio. Therefore, we adopted an approach to transform nitrogen-containing carbonbased compounds with a fixed N/C ratio (as a starting material) into NGC, with the N/C ratio unchanged. Forming the graphitic skeleton of NGCs is often performed by pyrolysis using a furnace [12, 13, 33–44] or laser treatment.[45–48] Although carbonization generally progresses with increasing temperature, most nitrogen atoms are diminished in the process when heated up above 600–8008C. Therefore, to increase the degree of carbonization and to suppress loss of nitrogen atoms, a system favorable to carbonization has to be designed.[50]Bowl-shaped compounds(hereinafter called by “π bowls”),[51] which belong to nonplanar π-conjugated compounds, have also attracted significant interest.[52–55] π Bowls are represented as partial structures of fullerene, including sumanene (1, C21H12, Figure 1b),[56] corannulene (C20H10),[57] and so on. There have been limited studies on π bowls as compared to those on fullerenes and carbon nanotubes. Therefore, we have been actively researching sumanene chemistry to show the potential characteristics of π bowls.[49, 52, 58] One of the features of π bowls is the strain attributed to the nonplanar π-conjugated shape (Figure 1c). Because of the strain, we expected a CÀC bond of 1 to be cleaved with ease as compared to those of planar ones, and this might support the carbonization. Moreover, as mentioned above, laser is known as one of the heating sources that can locally promote carbonization owing to its photothermal effect, thus allowing a target to be rapidly heated with positional selectivity. Therefore, this method is considered to be attractive for potential applications such as in electronic devices. As for the other nonplanar π-conjugated compounds, a laser-induced conductivity increase of fullerene C60 has been reported.[59–62] If monolay-

Nitrogen-doped graphitic carbon synthesized by laser annealing of sumanenemonoone imine as a bowl-shaped π-conjugated molecule.

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