Department of Physics, Ben-Gurion University of the Negev, Be'er-Sheva, Israel.
J Phys Condens Matter. 2012 Jun 6;24(22):225302. doi: 10.1088/0953-8984/24/22/225302. Epub 2012 May 3.
Intrinsic paramagnetic defects in ∼5 nm sized nanodiamonds, produced by various dynamic synthesis (DySND) techniques (detonation, shock-wave, pulsed laser ablation of solid carbon containing targets), have been studied by multi-frequency electron paramagnetic resonance (EPR). X-band (9-10 GHz) EPR spectra of DySND, in addition to the main intensive singlet Lorentzian-like EPR signal, reveal a low intensity doublet pattern within the half-field (HF) region (g ∼ 4). On transferring spectra to the Q-band (34 GHz) the shape of the HF pattern changes and splitting between doublet components is reduced from 10.4 to 2.6 mT. The HF patterns observed are attributed to the 'forbidden' ΔM(S) = 2 transitions between the Zeeman levels of some spin-triplet (S = 1) centers. The model of two triplet centers with g ∼ 2.003 and zero-field splitting parameters D(1) = 0.095 cm(-1) (TR1) and D(2) = 0.030 cm(-1) (TR2) satisfactorily describes experimental results at both microwave frequencies. The spin-triplet-type defects are observed in a wide variety of DySND samples irrespective of industrial supplier, cooling and carbon soot refinement methods, initial purity, disintegration, or subsequent targeted chemical modification. This indicates that the intrinsic defects with S = 1 in DySND systems are of universal origin.
采用各种动态合成（DySND）技术（爆炸、冲击波、固态含碳靶的脉冲激光烧蚀）制备的约 5nm 纳米金刚石中的固有顺磁缺陷，通过多频电子顺磁共振（EPR）进行了研究。DySND 的 X 波段（9-10GHz）EPR 谱除了主要的密集单重洛伦兹型 EPR 信号外，还在半磁场（HF）区域（g≈4）内揭示了一个低强度的双重模式。将光谱转移到 Q 波段（34GHz）时，HF 模式的形状发生变化，双峰分量之间的分裂从 10.4 减少到 2.6mT。观察到的 HF 模式归因于某些自旋三重态（S=1）中心的 Zeeman 能级之间的“禁戒”ΔM（S）=2 跃迁。两个具有 g≈2.003 的三重态中心和零场分裂参数 D（1）=0.095cm-1（TR1）和 D（2）=0.030cm-1（TR2）的模型在两种微波频率下都很好地描述了实验结果。自旋三重态缺陷在广泛的 DySND 样品中都可以观察到，无论工业供应商、冷却和碳 soot 细化方法、初始纯度、崩解还是随后的靶向化学修饰如何。这表明，DySND 系统中具有 S=1 的固有缺陷具有普遍的起源。
