Role of Nanodiamond Grains in the Exfoliation of WS Nanosheets and Their Enhanced Hydrogen-Sensing Properties.

Herein, for the first time, a combination of detonation nanodiamond (DND)-tungsten disulfide (WS) was devised and studied for its selective H-sensing properties at room temperature. DND-WS samples were prepared by a sonication-assisted (van der Waals interaction) liquid-phase exfoliation process in low-boiling solvents with DND as a surfactant. The samples were further hydrothermally treated in an autoclave under high pressure and temperature. The as-prepared samples were separated as two parts named DND-WS BH (before hydrothermal) and DND-WS AH (after hydrothermal). The exfoliated bilayer to few-layer DND-doped WS nanosheets were confirmed by ultraviolet-visible spectra, atomic force microscopy, and transmission electron microscopy studies. It was observed that the DND powder not only acted as a surfactant but also doped and expanded on WS nanosheets. The difference between samples BH and AH treatment was further investigated using Raman spectroscopy. The WS and DND-WS samples on SiO/Si were fabricated using a sputtered Pd/Ag interdigitated electrode and utilized for H gas-sensing measurements. Surprisingly, the DND-WS exhibits an ultrahigh sensor response of 72.8% to H at 500 ppm when compared to only 9.9% for WS alone. Also, the DND-WS shows a fast response/recovery time, high selectivity, and stability toward H gas. It can be attributed to the correlation of the intergrain phase of DND nanoparticles and WS nanosheets, which contributes to the easy transportation of charge carriers when exposed to the air and H gas atmosphere. Moreover, it is believed that DND-induced WS exfoliation might inspire future synthesis of transition metal dichalcogenides induced by DND in green solvents.