Detonation Nanodiamonds
The synthesis of nanodiamonds with sizes of only a few nanometers by the detonation of explosives has been known for many years. In a collaborative study with Daicel Corporation, we focused on the formation process of detonation nanodiamonds and investigated the doping of silicon based on the proposed formation mechanism.
Time-resolved measurements of the emission spectrum during detonation revealed emission from atomic carbon, whereas no characteristic emission from diatomic carbon (C₂) was observed. Based on these results together with previously reported molecular dynamics simulations, we proposed the “C₆ mechanism,” in which six-membered carbon rings, namely C₆ structures originating from TNT, aggregate while retaining their ring structures and subsequently transform into diamond through a liquid phase.
Based on this formation mechanism, triphenylsilanol (TPS), which contains C₆ structures and silicon, was added to the explosive as a dopant. As a result, nanodiamonds with a size of approximately 7 nm were obtained. When irradiated with a green laser, a characteristic emission peak of silicon-vacancy (SiV) centers was observed at approximately 738 nm [1]. These results demonstrated the formation of nanodiamonds containing SiV centers.
Various methods have been proposed for synthesizing nanodiamonds containing doped elements. A major advantage of the detonation method, however, is its ability to produce nanodiamonds only a few nanometers in size with high productivity.
[1] Y. Makino, T. Mahiko, M. Liu, A. Tsurui, T. Yoshikawa, S. Nagamachi, S. Tanaka, K. Hokamoto, M. Ashida, M. Fujiwara, N. Mizuochi, and M. Nishikawa, “Straightforward synthesis of silicon vacancy (SiV) center-containing single-digit nanometer nanodiamonds via detonation process,” Diamond & Related Materials, Vol. 112, Article 108248, 2021. DOI: 10.1016/j.diamond.2021.108248.