High-Yield Production\nof SiV-Doped Nanodiamonds for\nSpectroscopy and Sensing Applications

Nanodiamonds (NDs) containing optically active centers\nhave gained\nsignificant relevance as the material of choice for biological, optoelectronic,\nand quantum applications. However, current production methods lag\nbehind their real needs. This study introduces two CVD-based approaches\nfor fabricating NDs with optically active silicon-vacancy (SiV) color\ncenters: bottom-up (BU) and top-down (TD) methods. The BU approach\ngenerates nanoporous diamond films with a core–shell structure,\nwhile the TD method employs molten-salt thermal etching to create\nuniform porous structures from nanocrystalline diamond films. Comprehensive\ncharacterization using advanced techniques revealed distinct morphologies\nand optical properties for each approach. The BU method yielded higher-quality\ndiamond phases with top-surface incorporation of SiV centers, while\nthe TD method demonstrated efficient nondiamond phase removal. Ultrasonic\ndisintegration of both porous films produced NDs ranging from 40 to\n500 nm, with unique morphologies characteristic of each approach.\nPhotoluminescence measurements confirmed SiV centers (738 nm) in all\nNDs, exhibiting sensitivity to surface terminations, particularly\nin BU samples. Temperature-resolved spectroscopy shows the potential\nof the fabricated NDs for nano thermometry over a wide range of temperatures\nup to 100 °C. The zero-phonon line shows 0.022 ± 0.003 nm/K\nsensitivity, while the line width exhibits 0.068 ± 0.004 nm/K\nbroadening. The presented BU and TD methods offer significant advantages\nover existing techniques, including streamlined production processes,\nhigh-yield ND synthesis with tailored properties, and the potential\nfor scalable, cost-effective manufacturing.