Diacetylene-Zinc(II)-Zinc Oxide Nanocomposites for Colorimetric Detection of Ultraviolet-A Light

Polydiacetylenes (PDAs) have received widespread attention as chromatic sensors of various stimuli. The utilization of PDA materials for detecting ultraviolet-A (UVA) light, however, is quite rare. This study introduces a facile approach for enhancing the UVA-responsive property of PDAs. The incorporation of zinc oxide (ZnO) nanoparticles into the assemblies of diacetylene monomers, 10,12-pentacosadiynoic acid (PCDA), creates PCDA/Zn2+/ZnO nanocomposites. We have found that the nanocomposites change from colorless to blue upon exposure to UVA light. The intensity of blue color systematically increases with the UVA dose. The sensitivity to UVA light can be enhanced by increasing the ZnO ratios within the nanocomposites. Various types of UVA colorimetric sensors can be fabricated by incorporating the nanocomposites into a filter paper, hydrogel, and coconut oil. Interestingly, coconut oil-based sensors exhibit a color transition from colorless to blue with increasing UVA dose in sunlight from 0 to 50 J/cm2. This property allows their utilization for colorimetric detection of minimal erythema dose of UVA light, 33.27 J/cm2, for all skin types of normal people. The preparation of the nanocomposites is simple and cheap, suitable for large-scale production. The nanocomposites can be further developed for colorimetric detection of UVA radiation from sunbeds tanning, phototesting, and UV curing applications.