Ekimov Evgeny, Shiryaev Andrey A, Grigoriev Yuriy, Averin Alexey, Shagieva Ekaterina, Stehlik Stepan, Kondrin Mikhail
Vereshchagin Institute for High Pressure Physics, Russian Academy of Sciences, Troitsk, 108840 Moscow, Russia.
Frumkin Institute of Physical Chemistry and Electrochemistry, Russian Academy of Sciences, 119071 Moscow, Russia.
Nanomaterials (Basel). 2022 Jan 22;12(3):351. doi: 10.3390/nano12030351.
Diamond properties down to the quantum-size region are still poorly understood. High-pressure high-temperature (HPHT) synthesis from chloroadamantane molecules allows precise control of nanodiamond size. Thermal stability and optical properties of nanodiamonds with sizes spanning range from <1 to 8 nm are investigated. It is shown that the existing hypothesis about enhanced thermal stability of nanodiamonds smaller than 2 nm is incorrect. The most striking feature in IR absorption of these samples is the appearance of an enhanced transmission band near the diamond Raman mode (1332 cm-1). Following the previously proposed explanation, we attribute this phenomenon to the Fano effect caused by resonance of the diamond Raman mode with continuum of conductive surface states. We assume that these surface states may be formed by reconstruction of broken bonds on the nanodiamond surfaces. This effect is also responsible for the observed asymmetry of Raman scattering peak. The mechanism of nanodiamond formation in HPHT synthesis is proposed, explaining peculiarities of their structure and properties.
人们对直至量子尺寸区域的金刚石特性仍知之甚少。由氯代金刚烷分子进行的高温高压（HPHT）合成可实现对纳米金刚石尺寸的精确控制。研究了尺寸范围从小于1纳米至8纳米的纳米金刚石的热稳定性和光学特性。结果表明，关于尺寸小于2纳米的纳米金刚石热稳定性增强的现有假设是不正确的。这些样品红外吸收中最显著的特征是在金刚石拉曼模式（1332厘米-1）附近出现了一个增强的透射带。按照先前提出的解释，我们将此现象归因于金刚石拉曼模式与导电表面态连续体共振所引起的法诺效应。我们假定这些表面态可能是由纳米金刚石表面上断裂键的重构形成的。这种效应也是观察到的拉曼散射峰不对称性的原因。提出了高温高压合成中纳米金刚石的形成机制，解释了其结构和特性的独特之处。
