Nitrogen-Directed Diamond Nanothreads for Ultrahigh-Sensitivity Humidity Sensing and Noncontact Human-Machine Interfaces.

Diamond nanothreads (DNThs) are an emerging class of one-dimensional carbon materials that combine exceptional mechanical robustness with structural flexibility and tunable surface chemistry. While significant progress has been achieved in the synthesis and structural characterization of DNThs, their functional applications remain relatively unexplored. Here, we employ pyrazine as a nitrogen-containing precursor to synthesize diamond nanothread materials under high-pressure and high-temperature (HPHT) conditions (10 GPa and 400°C). Structural characterization suggests the formation of predominantly sp3-bonded one-dimensional carbon frameworks containing abundant polar surface functionalities. Benefiting from the synergistic effects of the one-dimensional architecture and hydrophilic surface sites, the fabricated DNThs-based humidity sensors exhibit outstanding performance over a broad humidity range (11%-96% RH), including ultrahigh sensitivity (1679.11/%RH), rapid response (5.2 s) and recovery (5.4 s), excellent reproducibility, and long-term stability. Mechanistic investigations indicate that efficient water adsorption and humidity-induced ionic conduction play critical roles in the sensing process, while the one-dimensional framework facilitates efficient charge transport. Furthermore, by integrating DNThs sensor arrays with a microcontroller platform, we demonstrate a non-contact human-machine interface (HMI) capable of gesture recognition and touch-free phone dialing. This work highlights the potential of diamond nanothread-based materials for next-generation intelligent sensing and interactive electronic systems.