National Research Center "Kurchatov Institute", Moscow, Russia.
Kintech Lab Ltd, Moscow, Russia.
Phys Chem Chem Phys. 2021 Jan 6;23(1):674-682. doi: 10.1039/d0cp05533f.
Structural organization of hydrogen and oxygen functionalized nanodiamond (ND) particles in hydrosols was investigated using a cryo-TEM method. The formation of chain-like structures was observed for hydrogen functionalized NDs while oxygen functionalized NDs tend to form more compact structures. In order to understand possible interaction mechanisms between NDs in hydrosols and to explain these experimental results, first-principles calculations were performed. Charged H-terminated ND particles and particles with partially dissociated hydroxyl and carboxyl groups on the surface were investigated as models of a real ND particle in solution. For positively charged H-terminated particles, it was established that charge distribution is determined by the values of valence band maximum for the particle facets. For negatively charged oxygen functionalized particles, the charge is localized near functional groups. In both cases, interaction is determined by the interplay between Coulomb interaction and van der Waals attraction. For detailed analysis of the ND interaction, the continual model considering this interplay was developed. The results obtained with this model indicate that the formation of chain structures from linked ND particles is caused by charge separation inside the ND particle. For the H-terminated ND particles in water solution, strongly anisotropic distribution of electrostatic potential around the particles promotes formation of non-compact chain structures of particles via interaction between facets with opposite charges. This effect of charge separation is lower in the oxygen functionalized particles as the charge is localized at the uniformly distributed O-containing functional groups, thus, more compact structures can be formed. These general qualitative statements address the problem of interactions between the large number of ND particles and explain the presented cryo-TEM experimental results.
采用低温透射电镜方法研究了水溶胶中氢、氧功能化纳米金刚石（ND）颗粒的结构组织。氢功能化 ND 形成链状结构，而氧功能化 ND 则倾向于形成更紧凑的结构。为了理解水溶胶中 ND 之间可能的相互作用机制并解释这些实验结果，进行了第一性原理计算。以带电荷的 H 终止 ND 颗粒和表面部分离解的羟基和羧基颗粒作为溶液中真实 ND 颗粒的模型进行了研究。对于带正电荷的 H 终止颗粒，确定了价带最大值决定了颗粒表面的电荷分布。对于带负电荷的氧功能化颗粒，电荷定域在功能基团附近。在这两种情况下，相互作用由库仑相互作用和范德华吸引的相互作用决定。为了详细分析 ND 的相互作用，开发了考虑这种相互作用的连续模型。该模型的结果表明，由带电荷的 ND 颗粒之间的电荷分离导致了链状结构的形成。对于水溶液中的 H 终止 ND 颗粒，由于颗粒周围的静电势具有强烈的各向异性分布，因此通过具有相反电荷的晶面之间的相互作用促进了非紧凑的颗粒链状结构的形成。氧功能化颗粒中这种电荷分离的效果较低，因为电荷定域在均匀分布的含 O 功能基团上，因此可以形成更紧凑的结构。这些一般定性的陈述解决了大量 ND 颗粒之间相互作用的问题，并解释了所提出的低温 TEM 实验结果。
