Effects of UV irradiation on the structural and optical properties of epoxy/dysprosium nanocomposite sheets for possible UV dosimetry and optoelectronic applications†

The exceptional properties of epoxy polymers are well-known because of their insulating properties, chemical resistance, and mechanical strength. Positioning them as favorable polymers compared to other polymers. But, despite these exceptional properties, epoxy materials have disadvantages, including brittleness and susceptibility to oxygen and UV light. To minimize these limitations and test the potential applications of epoxy polymers in UV sensing, we incorporated dysprosium ions (Dy³⁺) into the epoxy matrix using a simple chemical route by employing ethanol as a suitable solvent for both materials. The sheets were characterized using multiple techniques, including SEM, XRD, Raman, and PL. Using this technique, we achieved a PL emission enhancement up to 17 times that of pure epoxy and improved UV stability. Epoxy/Dy nanocomposite sheets showed sharp PL peaks with increasing Dy³⁺ ion concentrations, besides minor shifts in the PL emission peak centers, indicating possible tuning of the optical properties of the epoxy. The epoxy sheets containing 1% of Dy³⁺ ions were further exposed to UV light for different exposure times. The PL emission intensities of the irradiated sheets exhibited changes, including variations in peak position and FWHM of the spectra, with increasing UV exposure time. Additionally, the UV sensitivity in the nanocomposite sheets was found to be significantly improved. The linearity of these sheets' response was investigated using linear regression analysis, yielding a high adjusted R² of greater than 98%. This high R² confirmed their excellent linearity response, as well as their long-term PL intensity stability, retaining over 50% of the PL intensities after one month of irradiation. Therefore, the drastic increase in PL emissions due to the presence of Dy³⁺ ions in epoxy sheets, the linearity of the response, and the long-term stability of PL intensity, in addition to the reproducibility of the signals over a long time, validate the potential of these sheets for UV sensing and other optoelectronic device applications.