A series of highly fluorinated polyimide/allomelanin nanoparticles (FPI/AMNPs) films were prepared with FPI as the matrix and AMNPs as the filler. Due to the formation of hydrogen bonds, significantly reinforced mechanical and UV-shielding properties are acquired. Stress–strain curves demonstrated a maximum tensile strength of 150.59 MPa and a fracture elongation of 1.40% (0.7 wt.% AMNPs), respectively, 1.78 and 1.56× that of pure FPI. The measurements of the UV-vis spectrum, photodegradation of curcumin and repeated running tests confirmed the splendid UV-shielding capabilities of FPI/AMNPs films. The enhancement mechanisms, such as synergistic UV absorption of the charge transfer complexes in FPI and AMNPs and photothermal conversion, were the reasons for its exceptional UV shielding. The excellent comprehensive properties above enable FPI/AMNPs nanocomposites to be potential candidates in the field of UV shielding.Keywords:polyimide;allomelanin;mechanical properties;UV-shielding properties;nanocomposite
Wang Chao,Zhang Rong,Zhang Jianhua,Zhang Xueqian,Zhang Hengjie,Cao Huan,Yang Zhen,Li Yiwen
Agents with robust ultraviolet (UV) absorption capabilities play a vital role in safeguarding organisms and inorganic materials from UV damage. Nonetheless, the synthetic procedures towards these UV absorbers are usually lengthy and complicated, accompanied by undesirable side reactions and the generation of toxic substances. In nature, allomelanin, a class of melanins variant found in melanized fungi near the Chernobyl nuclear power plant, plays crucial roles in the cell wall of melanized fungi, offering resistance to harsh external environments and promising UV resistance capabilities. Notably, allomelanin can be rapidly biosynthesized via the polymerization of 1,8-dihydroxynaphthalene in presence of enzymes in fungi. Inspired by this, we report here a green enzymatic polymerization strategy to efficiently and eco-friendly synthesize polydihydroxynaphthalene (PDHN)-based artificial allomelanin nanoparticles (NPs) with interesting features. Theoretical calculations and experimental results demonstrated that the PDHN NPs exhibited excellent UV absorption capacity, surpassing another widely used artificial melanin, polydopamine (PDA). Moreover, the light absorption mechanism of PDHN NPs was systematically elucidated for the first time. Then, the PDHN NPs were incorporated with polyvinyl alcohol (PVA) to create an anti-aging composite film with significantly enhanced UV shielding ability. The potential of these composite films in safeguarding plants from UV damage was meticulously verified. Remarkably, these PDHN NPs were first found to produce hydroxyl radicals (•OH) under UV irradiation, offering antibacterial properties that expand their potential applications.
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