The risk of extensive exposure of the human epidermis to solar ultraviolet radiation is significantly increased nowadays. It not only induces skin aging and solar erythema but also increases the possibility of skin cancer. Therefore, a simply prepared, highly sensitive, and optically readable device for monitoring the solar ultraviolet radiation is highly desired for the skin health management. Because of the photoinitiated polymerization triggered by graphene-carbon nitride (g-C 3 N 4 ) under ultraviolet radiation, g-C 3 N 4 is homogeneously distributed in the hybrid hydrogels containing N-isopropylacrymide (NIPAM), poly(ethylene glycol) methyl ether methacrylate (OEGMA 300 ), and sodium alginate (SA). By further immersing the hybrid hydrogels into calcium chloride solution, hybrid alginate-Ca 2+ /P(NIPAM-co-OEGMA 300 )/g-C 3 N 4 interpenetrating polymeric network (IPN) hydrogels are obtained. Due to the homogeneous distribution of g-C 3 N 4 and the existence of thermoresponsive polymers, the hybrid IPN hydrogels present good adsorption capability and high degradation efficiency for methylene blue (MB) especially at high temperature under ultraviolet radiation. Based on this unique property, the bracelet monitoring skin health is prepared by simply immersing the hybrid IPN hydrogels into the MB solution and then wrapping it with PET foil. Because the immersion time for the top, middle, and bottom parts of the hybrid IPN hydrogels is gradually increased, their colors vary from light to dark blue. A longer time is required for the discoloration of the darker part under solar ultraviolet radiation. Thus, the bracelet can be used to conveniently monitor the dose of solar ultraviolet radiation by simply checking the discoloration in the bracelet under sunshine. Due to the facile preparation and low cost of the bracelet, it is a promising candidate for wearable devices for skin health management.

The impact of thermal history on the kinetic response of thin thermoresponsive diblock copolymer poly­(diethylene glycol monomethyl ether methacrylate)-block-poly­(poly­(ethylene glycol) methyl ether methacrylate), abbreviated as PMEO2MA-b-POEGMA300, films is investigated by in situ neutron reflectivity. The PMEO2MA and POEGMA300 blocks are both thermoresponsive polymers with a lower critical solution temperature. Their transition temperatures (TTs) are around 25 °C (TT1, PMEO2MA) and 60 °C (TT2, POEGMA300). Thus, by applying different temperature protocols (20 to 60 or 20 to 40 to 60 °C), the PMEO2MA-b-POEGMA300 thin films experience different thermal histories: the first protocol directly switches from a swollen to a collapsed state, whereas the second one switches first from a swollen to a semicollapsed and finally to a collapsed state. Although the applied thermal histories differ, the response and final state of the collapsed films are very close to each other. After the thermal stimulus, both films present a complicated response composed of an initial shrinkage, followed by a rearrangement. Interestingly, a subsequent reswelling of the collapsed film is only observed in the case of having applied a thermal stimulus of 20 to 40 °C. The normalized film thickness and the D2O amount of each layer in the PMEO2MA-b-POEGMA300 films are consistent at the end of the two different thermal stimuli. Hence, it can be concluded that the thermal history does not influence the final state of the PMEO2MA-b-POEGMA300 films upon heating. Based on this property, these thin films are especially suitable for the temperature switches on the nanoscale, which may experience different thermal histories.

The enhanced adsorption of methylene blue in aqueous solutions is triggered by the phase transition of the thermoresponsive copolymer poly(di(ethylene glycol) methyl ether methacrylate-co-poly(ethylene glycol) methyl ether methacrylate) (P(MEO 2 MA-co-OEGMA 300 )) in alginate−Ca 2+ hydrogels containing the photocatalyst graphitic carbon nitride (g-C 3 N 4 ). The obtained hybrid alginate−Ca 2+ /P(MEO 2 MA-co-OEGMA 300 )/g-C 3 N 4 hydrogels possess an interpenetrating polymer network (IPN) structure. The embedded g-C 3 N 4 induces a porous structure, which not only significantly enhances the hydration ability but also improves the adsorption capability of methylene blue. The collapse of P(MEO 2 MA-co-OEGMA 300 ) causes the hybrid IPN hydrogels to become more porous when the temperature is increased to its transition temperature (TT, 45 °C). Thereby, the adsorption capability is further enhanced. Absorption of 100% methylene blue in the aqueous solution can be achieved in 2 h, which is three times faster than that at 40 °C (below TT). As the TT of acrylate-based thermoresponsive polymers is correlated to the number of ethoxy groups in the side chains, the collapse temperature of thermoresponsive hydrogels can be easily adjusted to the desired temperature by simply changing the types and molar ratios of the monomers. Due to the embedded g-C 3 N 4 , all adsorbed methylene blue can be degraded after placing in ambient conditions and exposure to visible light for 12 h. Thus, the hybrid IPN hydrogels are well recyclable. Based on the capability of enhanced adsorption and reutilization, the hybrid alginate− Ca 2+ /P(MEO 2 MA-co-OEGMA 300 )/g-C 3 N 4 IPN hydrogels can be used for the removal of dye pollutants from wastewater with high efficiency and good recyclability.

Graphitic carbon nitride (g-C3N4) exhibits an excellent photocatalytic performance as powder, especially under visible light irradiation. However, it encounters great challenges for practical applications. For instance, to avoid aggregation and...

Novel hydrogen evolution system based on hybrid nanogel films are successfully prepared with capabilities of spontaneous moisture collection and high light harvesting. Hybrid nanogels are synthesized by homogenously dispersing graphitic...