Ultraviolet (UV) light is known to be harmful to human health and cause organic materials to undergo photodegradation. In this Research Article, bioinspired dopamine-melanin solid nanoparticles (Dpa-s NPs) and hollow nanoparticles (Dpa-h NPs) as UV-absorbers were introduced to enhance the UV-shielding performance of polymer. First, Dpa-s NPs were synthesized through autoxidation of dopamine in alkaline aqueous solution. Dpa-h NPs were prepared by the spontaneous oxidative polymerization of dopamine solution onto polystyrene (PS) nanospheres template, followed by removal of the template. Poly(vinyl alcohol) (PVA)/Dpa nanocomposite films were subsequently fabricated by a simple casting solvent. UV irradiation protocols were set up, allowing selective study of the extra-shielding effects of Dpa-s versus Dpa-h NPs. In contrast to PVA/Dpa-s films, PVA/Dpa-h films exhibit stronger UV-shielding capabilities and can almost block the complete UV region (200-400 nm). The excellent UV-shielding performance of the PVA/Dpa-h films mainly arises from multiple absorption because of the hollow structure and large specific area of Dpa-h NPs. Moreover, the wall thickness of Dpa-h NPs can be simply controlled from 28 to 8 nm, depending on the ratio between PS and dopamine. The resulting films with Dpa-h NPs (wall thickness = ∼8 nm) maintained relatively high transparency to visible light because of the thinner wall thickness. The results indicate that the prepared Dpa-h NPs can be used as a novel UV absorber for next-generation transparent UV-shielding materials.
High-entropy alloys have received considerable attention in the field of catalysis due to their exceptional properties. However, few studies hitherto focus on the origin of their outstanding performance and the accurate identification of active centers. Herein, we report a conceptual and experimental approach to overcome the limitations of single-element catalysts by designing a FeCoNiXRu (X: Cu, Cr, and Mn) High-entropy alloys system with various active sites that have different adsorption capacities for multiple intermediates. The electronegativity differences between mixed elements in HEA induce significant charge redistribution and create highly active Co and Ru sites with optimized energy barriers for simultaneously stabilizing OH* and H* intermediates, which greatly enhances the efficiency of water dissociation in alkaline conditions. This work provides an in-depth understanding of the interactions between specific active sites and intermediates, which opens up a fascinating direction for breaking scaling relation issues for multistep reactions.
Sepia eumelanin (SE), a biomacromolecule,
was developed to prepare
the excellent UV-shielding polymer material with better photostability.
UV–vis transmittance spectra showed that poly(vinyl alcohol)
PVA/SE film blocked most ultraviolet light below 300 nm even with
a low concentration of SE (0.5 wt %), which still kept its high transparency in the
visible spectrum. Rhodamine B photodegradation measurement further
confirmed the excellent UV-shielding properties of PVA/SE film. FTIR
indicated that the carbonyl absorption bands resulting from phtodegradation
for PVA/SE film did not change after UV exposure for 2700 h. The tensile
properties of neat PVA were deceased intensely after UV irradiation;
however, those of PVA/SE film were reduced a little. Moreover, AFM
indicated that the surface roughness of PVA/SE film was much lower
than that of a neat PVA one. It could be concluded that SE reduced
the PVA degradation rate dramatically, revealing enhanced photostability
of PVA/SE film. The mechanism for outstanding UV-shielding properties
and photostability of PVA/SE film was illuminated, based on the formation
of charge transfer complexes (CTCs) between SE and PVA, photothermal
conversion, and the well-known radical scavenging capabilities of
SE.
PHB/PBS and PHBV/PBS blends are prepared via in situ compatibilization using DCP as a free‐radical grafting initiator. A considerable reduction in PBS particle size and a significant increase in the interfacial adhesion between the PHB(V) and PBS phases are observed after the compatibilization. The elongation at break of the PHBV/PBS blends was considerably increased. The local deformation mechanism indicates that matrix yielding together with dilatation, deformation, and fibrillation of the PBS particles are responsible for the improved tensile toughness of the compatibilized PHBV/PBS blends. The tensile strength, impact toughness, and elongation at break of injection‐molded PHB(homopolymer)/PBS blends are also increased after in situ compatibilization.magnified image
Tuning surface strain is a new strategy for boosting catalytic activity to achieve sustainable energy supplies; however, correlating the surface strain with catalytic performance is scarce because such mechanistic studies strongly require the capability of tailoring surface strain on catalysts as precisely as possible. Herein, a conceptual strategy of precisely tuning tensile surface strain on Co S /MoS core/shell nanocrystals for boosting the hydrogen evolution reaction (HER) activity by controlling the MoS shell numbers is demonstrated. It is found that the tensile surface strain of Co S /MoS core/shell nanocrystals can be precisely tuned from 3.5% to 0% by changing the MoS shell layer from 5L to 1L, in which the strained Co S /1L MoS (3.5%) exhibits the best HER performance with an overpotential of only 97 mV (10 mA cm ) and a Tafel slope of 71 mV dec . The density functional theory calculation reveals that the Co S /1L MoS core/shell nanostructure yields the lowest hydrogen adsorption energy (∆E ) of -1.03 eV and transition state energy barrier (∆E ) of 0.29 eV (MoS , ∆E = -0.86 eV and ∆E = 0.49 eV), which are the key in boosting HER activity by stabilizing the HER intermediate, seizing H ions, and releasing H gas.
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