Smart packaging materials incorporating titania-based photocatalytic hydrogels for ultraviolet and sunlight exposure monitoring

This work demonstrates the fabrication of UV-responsive devices made of common packaging materials and photocatalytically active hydrogels. Using bubble wraps, a common packaging material as enclosures of a UV-sensitive photocatalytic probe, a readily deployable device was created for visualizing exposure-dependent color changes induced by varying doses of UV exposure. The signal occurred from the photocatalytic decomposition of a colored dye (methyl orange) by TiO 2 , entrapped in agarose hydrogel that is stored within the pouches of bubble cushion wrap. Sensitivity to UV radiation dose could be tuned by varying the amount of catalyst (from 8.3 to 50 mg L 1 ) and the concentration of indicator dye (from 0.02 to 0.04 % w / v ) or by using photoprotective coatings composed of PVA membranes enriched with a hydrophilic sunscreen agent (1.25–3.75 mg sunscreen per g of PVA). The probe was sensitive to a wide range of UV radiation spanning from UVC (254 nm) to UVA (365 nm), enabling its application to a variety of applications involving UV exposure. As a demonstration, the devices were used to monitor sunlight exposure under variable conditions involving direct solar exposure, intermittent exposure, and in aquatic environments. The reactivity of the probe could be tuned from 1.8 × 10 6 J m −2 , which is adequate to qualitatively indicate the UV radiation doses for the synthesis of vitamin D and the induction of erythema to fair skin types, to 7.2 × 10 6 J m −2 with a PVA membrane enriched with a sunscreen agent. Such high doses can be used to alert potential sunburn for darker and brown skin types from prolonged exposure to UV light and sunlight. • Common packaging material transformed into smart UV light sensor. • Photocatalytically active hydrogels incorporated in bubble wraps. • Tunable sensitivity up to very high doses of sunlight radiation. • Flexible and portable UV dosimeter device with visual observation or imaging devices. • Intermittent and underwater UV light monitoring capability.