1：Experimental Design and Method Selection:

The synthesis involves a two-stage non-thermal plasma reactor for the synthesis and immediate passivation of TiN nanocrystals. The first stage nucleates and grows TiN nanoparticles, and the second stage coats them with a protective silicon-containing shell.

2：Sample Selection and Data Sources:

Free-standing TiN-based nanoparticles are produced and either collected as freestanding powder or impacted onto a substrate to create a thin film.

3：List of Experimental Equipment and Materials:

The setup comprises two capacitively-coupled non-thermal plasma reactors powered by two independent 13.56 MHz radio frequency (RF) power supplies. Materials include Ar, TiCl4, NH3, and Ar-SiH4 gas.

4：56 MHz radio frequency (RF) power supplies. Materials include Ar, TiCl4, NH3, and Ar-SiH4 gas. Experimental Procedures and Operational Workflow:

4. Experimental Procedures and Operational Workflow: TiN nanoparticles are synthesized in a gas mixture comprising Ar, TiCl4 and NH3. The aerosol is then dragged into a second plasma reactor where it is coated with a silicon-based shell.

5：The aerosol is then dragged into a second plasma reactor where it is coated with a silicon-based shell. Data Analysis Methods:

5. Data Analysis Methods: Structural and chemical characterization was performed with a high-resolution STEM, XPS, and UV-VIS-NIR spectrophotometer. FDTD simulations were used to assess the effect of material oxidation on the LSPRs.