Nonthermal Plasma Synthesis of Titanium Nitride Nanocrystals with Plasmon Resonances at Near-Infrared Wavelengths Relevant to Photothermal Therapy

Titanium nitride has attracted attention for its plasmonic properties as a thermally stable, biocompatible, and cost-effective alternative to gold. In this work, we synthesized titanium nitride nanocrystals in a nonthermal plasma using tetrakis (dimethylamino) titanium (TDMAT) and ammonia as the titanium and nitrogen precursors. Extinction measurements of as-produced 6-8 nm titanium nitride nanocrystals exhibit a broad plasmon resonance peaking near 800 nm, possibly suitable for photothermal therapy treatments. Ammonia flow rate and plasma power were found to affect nanocrystal morphology and chemical composition, and therefore significantly impact the plasmonic properties. A moderate ammonia flow rate of 1.2 sccm and relatively high nominal plasma power of 100 W produced samples with the best plasmon resonances, narrower than those previously reported for plasma-synthesized titanium nitride nanocrystals.