Enhancement of pressure-sensitive paint emission using localized surface plasmon resonance for shock tunnel applications

To apply Pressure-Sensitive Paint (PSP) to unsteady or short-duration tests like hypersonic shock tunnels, we need to solve the two fundamental problems. First, polymer-based PSP shows slow time response so that the thickness of PSP film must be reduced to a submicron range. However, such a thin paint film displays a very low Signal-to-Noise Ratio (SNR) because the number of photons detected by a camera is reduced with film thickness. To solve these conflicting problems, it is required to develop a new PSP that emits strong luminescence even though its film thickness is thin enough for unsteady measurements. In this study, systematic experiments were conducted to explore the potential of using Localized Surface Plasmon Resonance (LSPR) of silver (Ag) nanoparticles to enhance the luminescent emission of polymer-based PSP. PSP coupons containing Ag nanoparticles of different sizes and concentrations were prepared and their luminescent intensities were compared. It was found that the luminescent intensity of PSP sample was enhanced about 3-fold by the addition of 35-nm Ag nanoparticles. The same principle was applied to a 0.3-μm thick of Poly(TMSP)-based PSP and the advantage of nanoparticle addition was evaluated in a shock tunnel. It was confirmed that the SNR could be enhanced 1.6-fold using LSPR excitation.