Luminescent Pressure-Sensitive\nPaints with Embedded\nAg@SiO<sub>2</sub> Nanoparticles

Designing pressure-sensitive paint (PSP) to achieve high\nluminescence\nand high pressure sensitivity at near-atmospheric pressures increases\nthe signal-to-noise ratio of the luminescence images, facilitating\naerodynamic studies of low-speed flows. Here, we investigate a PSP\nformulation that incorporates silica-coated silver nanoparticles (Ag@SiO<sub>2</sub>), along with Pt(II) <i>meso</i>-tetra(pentafluorophenyl)porphine\n(PtTFPP) embedded in a sol–gel matrix. The Ag@SiO<sub>2</sub> nanoparticles enhance the luminescence of PtTFPP by localized surface\nplasmon resonance (LSPR)-induced electric field enhancement rather\nthan through altering the radiative decay rate of PtTFPP. The thickness\nof the silica layer and the mass ratio of Ag/PtTFPP are essential\nfor optimizing the luminescence enhancement. In comparison to Ag-free\nPSP, the Ag@SiO<sub>2</sub>-doped PSP exhibits a 2-fold luminescence\nenhancement while maintaining a high pressure sensitivity of 0.94%/kPa\nnormalized to atmospheric pressure data. The high luminescence and\npressure sensitivity not only offer increased signal strength for\nimaging low-speed airflows but also hold promising potential for future\ndesigns of PSP formulations using MEL.