Perylene Dye as a Local Thermal and Mechanical Sensor of Local Nanoscale Polymer Matrices

Studies on nanoscale materials often require new characterization methods to monitor thermal and mechanical material properties. Fluorescence spectroscopy, with its high sensitivity, allows trace levels of dyes to act as local non-contact probes. Perylene is a robust fluorophore with high quantum yield that has been previously shown to exhibit sensitivity to temperature and pressure, including being used as a local thermometer of the surrounding material. We characterize the temperature dependence of the perylene's emission spectrum doped into a range of different polymers: poly(methyl methacrylate) (PMMA), polystyrene (PS), poly(2-vinyl pyridine) (P2VP), and polycarbonate (PC). We find that with regard to a temperature-invariant reference point, the peak intensity shows a linear response to changes in temperature, where certain polymer matrices result in a stronger perylene sensitivity to temperature. Such qualitatively similar temperature dependencies across different polymers could be indicative of the material's thermal expansion and stiffness of the surrounding polymer matrix. Using a home-built apparatus to apply different pressures, we also characterize the pressure dependence of perylene's emission spectrum to infer the stress response of the system.