Keyword: «nanodiamonds»

After heat treatment, the ratio of hydroxyl and carboxyl groups, according to IR spectra, both in samples of natural nanodiamonds and in nanodiamonds obtained by detonation synthesis, decreases. An increase in the amount of carboxyl groups on the surface of nanodiamonds after heat treatment in air indicates the oxidation of functional groups under experimental conditions. In the IR spectra of nanodiamonds after heat treatment, the bands in the absorption region of the diamond lattice become more distinguishable, which is explained by the partial purification of the diamond crystalline core from the graphite-like shell. In the IR spectra of natural nanodiamonds after heat treatment, bands appear in the absorption region of nitrogen defects of types A and B, which makes it possible to attribute the sample under study to type I-AB.

A comparative analysis was conducted on the morphology and structural characteristics of primary particles in powders of natural nanodiamonds (NND) and detonation-synthesized nanodiamonds (DND), obtained by mechanical grinding and detonation synthesis methods respectively. The study employed high-resolution scanning electron microscopy techniques. Differences were observed in particle size, shape, and density defect between both types of powder. Interplanar distances and structural parameters of nanoparticles were determined. It was shown that NND nanocrystals are characterized by a wide variety of shapes and sizes, whereas DND particles demonstrate greater uniformity, although structural defects in the core of DNA particles occur more frequently.

The effect of thermal treatment on the composition of functional groups in detonation and natural nanodiamonds was studied using X-ray photoelectron spectroscopy. It was shown that annealing in air at 400–550 °C leads to a decrease in the fraction of sp²-hybridized carbon atoms and an increase in the sp³ component. Changes in oxygen- and nitrogen-containing functional groups were revealed, indicating oxidation processes and restructuring of surface chemical bonds in nanodiamond particles.

The detonation and natural nanodiamonds were investigated using nuclear magnetic resonance (NMR) spectroscopy before and after thermal treatment. The NMR spectra of the initial samples revealed signals from sp³- and sp²-hybridized carbon atoms corresponding to the diamond core and disordered carbon shell. Thermal annealing at 550 °C leads to a decrease in non-diamond sp² carbon and changes in the surface functional groups. The results confirm the effectiveness of thermal purification of nanodiamonds.

The effect of thermal treatment on the composition of oxygen-containing functional groups in natural (NND) and detonation (DND) nanodiamonds was studied using FTIR spectroscopy and Boehm titration. It was found that annealing in air at 550 °C alters the ratio of hydroxyl and carbonyl groups, removes non-diamond carbon forms, and improves the ordering of the surface structure. The results are consistent with XPS data and confirm the effectiveness of thermal treatment for nanodiamond purification.