ESR in a disordered network of nanographene sheets
ESR in a disordered network of nanographene sheets
复制标题
纳米石墨烯片无序网络中的 ESR
DOI：
10.1088/1742-6596/334/1/012040
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发表时间：
2011
期刊：
影响因子：
--
通讯作者：
et al
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文献类型：
--
作者：
M.Hagiwara;et al
利用电子自旋共振（ESR）技术在20 GHz（K波段）和35 GHz（Q波段）对随机网络化的纳米石墨烯片进行了研究。纳米石墨烯具有自旋极化的非键合π电子态（边缘态自旋），其位于锯齿形边缘区域中。我们研究了活性炭纤维在两种不同的微波功率下的ESR信号的温度依赖性。在任何微波功率下，信号强度随着温度的降低而平滑地增加。具有洛伦兹线形的ESR信号的线宽在冷却时线性减小，然后在约20 K处取最小值后急剧增加，而与微波功率无关。前者被解释为定域边缘自旋和导电π载流子的Korringa关系。后者可能是由来自随机分布的具有不同尺寸的纳米石墨烯片的ESR信号的不均匀谱线展宽引起的，这是由于纳米石墨烯片之间的电子跳跃（即电子局域化）的抑制。在1 μW的X波段ESR中，没有观察到20 K附近的谱线不连续展宽和信号强度下降，这可能是由于微波功率高于1 μW或样品中有一定量的氧吸附。
Randomly networked nanographene sheets have been studied by electron spin resonance (ESR) technique at 20 GHz (K-band) and 35 GHz (Q-band). Nanographene has spin-polarized non-bonding π-electron states (edge-state spins) localized in the zigzag edge region. We have investigated the temperature dependence of an ESR signal of activated carbon fibers at two different microwave powers for each frequency. The signal intensity smoothly increases with decreasing temperature at any microwave power. The line width of ESR signal with a Lorentzian line shape decreases linearly upon cooling, and then increases steeply after taking a minimum at about 20 K irrespective of microwave power. The former is interpreted as the Korringa relation in the localized edge spins and conduction π carriers. The latter may be caused by inhomogeneous line broadening of the ESR signal from randomly distributed nanographene sheets with different sizes due to the suppression of electron hopping between nanographene sheets, ie electron localization. The discontinuous line broadening and the signal intensity drop at around 20 K reported in the previous X-band ESR at 1 μW were not observed, probably because of either higher microwave power than 1 μW or some amount of oxygen adsorption in our sample in the present study.