Extension and characterization of pressure-sensitive molecular film

Pressure-sensitive paint (PSP) has the potential as a diagnostic tool for pressure measurement in high Knudsen number regime because it works as a so-called “molecular sensor”. However, there are few reports concerning application of PSP to micro-devices, because conventional PSPs are too thick owing to polymer binders. In our previous work, we adopted the Langmuir–Blodgett (LB) technique to fabricate the pressure-sensitive molecular film (PSMF) using Pd(II) Mesoporphyrin IX (PdMP), which has pressure sensitivity only in the low pressure range (below 130 Pa). In this study, aiming for pressure measurement under an atmospheric pressure condition, we have constructed four samples of PSMFs composed of Pt(II) Mesoporphyrin IX (PtMP), Pt(II) Mesoporphyrin IX dimethylester (PtMPDME), Pt(II) Protoporphyrin IX (PtPP) and Cu(II) Mesoporphyrin IX dimethylester (CuMPDME) as luminescent molecules. The pressure sensitivity of those PSMFs was measured, and it was clarified that the pressure sensitivity of PSMF-PtMP is the highest among the four samples. Moreover, the temperature dependency of PSMF-PtMP was investigated, and we found that the temperature dependency of PSMF is dominated not by the oxygen diffusion in the layer, but by non-radiative deactivation process of excited luminescent molecules.