UV Shielding Research Articles

Green synthesis of carbon quantum dots from wasted enzymatic hydrolysis lignin catalyzed by organic acids for UV shielding and antioxidant fluorescent flexible film

Biomass wastes have been demonstrated to be sufficient sources for the synthesis of carbon quantum dots (CQDs) using green and sustainable hydrothermal technology, and has been applied in many fields. However, the yield of CQDs from biomass directly hydrothermal is extremely low. This study aimed at prove the feasibility of conducting blue emissive CQD by a hydrothermal technology using enzymatic hydrolysis lignin (EHL) from biomass waste as the precursor and three organic acids such as citric acid (CA), DL-malic acid (DLMA) and oxalic acid (OA) for modification. HR-TEM analysis revealed that CQDs modified by organic acids had superior water solubility and smaller particle size than that of CQDs without organic acids (EHL CQDs). In particular, the citric acid-modified CQDs (CA-EHL CQDs) resulted in an increase in the fluorescence intensity and effective quantum yield (QY) up to 500 % and 4.5 %, respectively, displaying a narrower size distribution and a mean particle size of ca. 3.1 nm. In addition, the CQDs/PVA fluorescent nanocomposite films with UV shielding and antioxidant capacity were also developed in this work, which proved great application prospect in information protection, anti-counterfeiting materials, food packaging and other fields. These results are great contributions towards adopting low-cost, sustainable and green process to produce CQDs with high quantum efficiency and expanding the application range of lignin based CQDs. • A 500 % meliorative fluorescence intensity of the modified lignin-based CQDs. • The effective quantum yield (QY) increases from 0.8 % to 4.5 %. • The modified CQDs are hardly affected by external acid-base conditions. • CQDs/PVA fluorescent film with excellent UV shielding and antioxidant capacity.

Relationship between cellulolytic enzyme lignin structural and lignin nanoparticle-polyvinyl alcohol membrane property: Insights from monolignols and molecular dynamics simulations

Lignin is an abundant and sustainable biopolymer that presence great potential in the production of biofuels and biomaterials. In this work, cellulolytic enzyme lignin (CEL) was obtained from eucalyptus, pine, bamboo, and pennisetum in order to investigate the relationship between their structural and utilization in the production of lignin nanoparticle-polyvinyl alcohol (LNP-PVA) composite film. Results showed that CELs obtained from softwood contained the larger amount of G-type lignin, while CELs obtained from hardwood had more S-type lignin. The particle size of the LNPs was in the order of CEL-PI > CEL-PE > CEL-BB > CEL-EP. In addition, the existence of phenolic hydroxyl group in LNP was beneficial to the improvement of the UV shielding performance of LNP-PVA composite film. The higher content of H-type lignin in LNPs was, the better UV shielding performance of LNP-PVA composite film could be observed. The hydrophobicity of the composite films enhanced in the presence of LNPs with the order of BB-PVA > PE-PVA > PI-PVA > EP-PVA. Moreover, the higher amount of S-type lignin in LNPs was, the better mechanical properties of LNP-PVA composite film could be obtained. EP-PVA showed the best elongation with the respect to breakage and tensile strain performances. Molecular dynamic simulation indicated that the interaction between lignin monomers and PVA is mainly van der Waals force, and the position of methoxy group will affect their interaction strength. This study provided a new strategy for high-value utilization of lignocellulose.

Antioxidant and antibacterial PBAT/lignin-ZnO nanocomposite films for active food packaging

In present works, the lignin-zinc oxide (LZn) hybrid particles composed with lignin nanoparticles (LNP) and zinc oxide (ZnO) were prepared by a simple hydrothermal method under different pH conditions. Results from infrared spectra, thermogravimetric analysis, and elemental analysis evidenced the successful synthesis of LZn hybrids. The bacterial survival rate of LZn-9 (pH=9) against E. coli and S. aureus decreased to 9% and 49%, while the value of LNP was 69% and 80%, respectively. Then glyceryl methacrylate (GMA) was grafted on poly (butyleneadipate-co-terephthalate) (PBAT), following by the addition of LZn hybrid to prepare the master batches. Finally, the master batches were catalyzed by trimethylamine, and the PBAT-G-xLZn composite films were produced. The tensile modulus and yield strength of PBAT-G-3LZn increased by 35.2% and 28.6% compare with pure PBAT, respectively. The PBAT/LZn composite films were found to have obvious UV shielding, antioxidant and antibacterial activities. Composites belong to the contact type antibacterial, the bacterial adhesion rates of PBAT-G-xLZn were obviously reduced compare with pure PBAT. The transmittance at λ = 320 nm of PBAT-G-3LZn film was only 0.16%, and the radical scavenging activity (RSA) value was 11.6%. The Zn2+ migration concentration of PBAT-G-3LZn was only 3.3 μg/L. Therefore, the PBAT/LZn composite films were believed to be applied for active food packaging.

Valorization of enzymatic hydrolysis lignin for the multifunctional stabilization of polypropylene

Environmental toxicity of conventional stabilizers for polymers and their degradation products is raising severe concerns. There is an urgent need for the development of environmental-friendly, high-efficiency, and multifunctional stabilizers for polymers. Herein, Lignin nanoparticles (LNP), which were produced from enzymatic hydrolysis lignin (EHL) isolated from corncob residue, were demonstrated as a multifunctional stabilizer for polypropylene (PP). LNP fabricated by the anti-solvent method has distinct surface properties from the raw EHL, which lends it a better dispersion state in PP, and a higher free radical scavenging and UV absorption ability. The addition of 1 wt% LNP significantly enhances the thermo- and photo-oxidation stability of PP. The oxidation induction time of PP increases from 6.1 min to 12.3 min by 102 % with the addition of 1 wt% EHL, while it further increases to 20.1 min by 230 % for PP/LNP. Compared with PP, the oxidation degree of PP/EHL during thermo-oxidation for 8d is reduced by 27 % while that of PP/LNP is reduced by 60%. In addition, the UV degradation diffusion from the surface to the inner part of PP/LNP is significantly suppressed. These results highlight the excellent stabilization effects of LNP on PP and provide a promising path for the high-value-added lignin. • Lignin nanoparticles (LNP) were fabricated from enzymatic hydrolysis lignin via antisolvent method. • LNP significantly enhanced both thermo- and photo-oxidation stability of polypropylene (PP). • The stabilization roles of LNP were attributed to its better dispersibility in the PP matrix, enhanced free radical scavenging ability, and stronger UV shielding effect.

Salicylaldehyde and D-(+)-galactose functionalized chitosan oligosaccharide nanoparticles as carriers for sustained release of pesticide with enhanced UV stability

Sustainable food consumption is intertwined with sustainable agriculture development, which focuses on the production and protection of agricultural crops in a safe and effective fashion. Herein, amphiphilic functionalized chitosan oligosaccharide nanoparticles (CSD) were formed by a Schiff base reaction grafted with salicylaldehyde and D-(+)-galactose (D-Gal). Avermectin (AVM) was used as a model pesticide and self-assembled onto CSD to obtain AVM@CSD nanoparticles with an encapsulation efficiency of 74.94%. AVM@CSD nanocarrier exhibited excellent anti-UV property to retain more AVM, due to their Schiff base structure and salicylaldehyde for UV shielding. Compared with bare AVM and commercial AVM emulsifiable concentrates, AVM@CSD preserved high insecticidal activity after UV irradiation. Additionally, CSD carrier promoted cucumber seed germination and seedling growth. These data suggested the potential utilization of the amphiphilic chitosan oligosaccharide as carriers for pesticides to improve their delivery and release properties and opens a novel avenue towards the application of water-dispersible and biological CSD in the field of pest management and plant growth.

Preparation of PCU/PPy composites with self-healing and UV shielding properties

Polycarbonate-based polyurethanes (PCU) are frequently used in airship envelope materials because of its outstanding mechanical performances and aging resistance. However, the surface of PCU is likely damaged during processing and operating and the emerged minuscule cracks will lead to deterioration of perfomances for airship’s envelope materials. Herein, self-healing PCU/polypyrrole nanoparticles (PPy) composites were prepared by solution blending and quick healing of specific area for PCU was realized due to the high photo-thermal conversion merit of PPy. The results show that, the mechanical properties of PCU/PPy composites can be restored to more than 80% and the gas barrier properties can also be basically repaired when irradiating the destroyed surface using near-infrared light for only 60s. In addition, the ultraviolet visible (UV-vis) shielding performance of the PCU/PPy composites was enhanced significantly and the UV-vis transmittance was less than 14% and 2% with 0.25wt% and 0.5wt% PPy, respectively. Meanwhile when 0.25wt% PPy was added, the tensile strength increased from 17.9MPa to 21.7 MPa and the elongation at break increased from 647% to 829%. Besides, the thermal decomposition temperature at 5wt% loss increased from 277.8°C to 300.7°C and 304.88°C with 0.25 wt% and 0.5 wt% PPy, respectively. The prepared composites show promising application in aerospace domain.

Simultaneous strengthening and toughening lignin/cellulose nanofibril composite films: Effects from flexible hydrogen bonds

Inspired by the lignin-cellulose network in natural wood, we developed a strategy to produce cellulose nanofibril (CNF) composite films using lignin nanoparticles (LNPs) with varied contents of phenolic hydroxyl (Ph-OH) groups as a reinforcing agent. Regulated LNPs with lower molecular weight, higher Ph-OH content, and uniform morphology were successfully prepared by phenolation and anti-solvent precipitation. CNFs mixed with phenolated LNPs of high Ph-OH content (8.23 mmol/g) exhibited a higher tensile strength (∼190 MPa), increased toughness (∼15 MJ/m3), and enhanced UV-blocking ability (∼99 %) compared to lignin-free CNFs and CNF composites with lower Ph-OH content. Thus, hydrogen bonds between Ph-OH groups on lignin and hydroxyl groups on CNFs are vital for enhancing the mechanical strength of composite films. Similar enhanced mechanical properties were found by adding phenolated LNPs into polyvinyl alcohol as a fortifier. This study provides novel insights into producing lignin-reinforced cellulose composite films with UV shielding, thermal stability, and biodegradability.

Biodegradable poly(butylene succinate‐co‐butylene furandicarboxylate): Effect of butylene furandicarboxylate unit on thermal, mechanical, and ultraviolet shielding properties, and biodegradability

AbstractBiobased co‐polyesters poly(butylene succinate‐co‐butylene furandicarboxylate) (PBSF) is prepared by transesterification and polycondensation of dimethyl succinate (DSMu), dimethyl 2,5‐furandicarboxylate (MDFD) and 1,4‐butanediol (1,4‐BDO). GPC analysis shows that PBSF has high molecular weight with weight average molecular weight (Mw) up to 11 × 104 g/mol. Due to the low ‐COOH content, PBSF also has excellent thermal stability, which is beneficial to the polyester processing. Differential scanning calorimetry (DSC) analysis shows that PBSF are semi‐crystalline materials, with Tm ranging from 116 to 101°C. Tensile tests showed that theses polymers possess high tensile strength (30–22 MPa) and elongation at break as high as 562%, which is prominently higher than that of commercial poly(butylene succinate) (PBS) and most biodegradable packaging materials. It should be noted that the increase of BF units improves the UV shielding properties of polyester materials. Moreover, the incorporation of furan ring promoted the enzymatic degradation of PBS, and PBSF showed a significantly faster biodegradation rate when the BF unit content is 5%. PBSF polyester has excellent thermal properties, tensile properties, UV shielding properties and biodegradable properties. Therefore, these new bio‐based polymers have great potential to be applied as environmentally friendly and sustainable plastic packaging.

In Situ Growth of a Stable Metal-Organic Framework (MOF) on Flexible Fabric via a Layer-by-Layer Strategy for Versatile Applications.

Fabrics have been used broadly in daily life for an enormous variety of applications due to their intrinsic advantages, such as flexibility, renewability, and good processability. Integrating natural fabrics with metal-organic frameworks (MOFs) is an effective strategy to improve the added value of textiles with special functionalities. Here, a facile, low-cost, and scalable technology is reported for the in situ growth of MOFs on cotton fabrics. A uniform and dense coating of regular octahedral Cu-1,3,5-benzenetricarboxylic acid (CuBTC) crystals was formed on the fiber surface, followed by treatment with 1H,1H,2H,2H-perfluorooctyltriethoxysilane and triethoxyoctylsilane to create a superhydrophobic CuBTC@cotton fabric (SMCF), which greatly improved its water stability and extended superhydrophobic CuBTC's potential applications. The as-prepared MCF has a specific surface area of 229 m2/g, which is 11 times that of pristine fabrics (21 m2/g). This high porosity further endows the fabric with enhanced loading capacity of essential oils to enable excellent antibacterial ability. Moreover, the SMCF also exhibits excellent self-cleaning, UV shielding, and anti-icing performances. In addition, we performed COMSOL simulations to investigate the dynamic freezing process of water on the surface of samples, which agrees well with our experimental observations. By combining the merits of both fabrics and MOFs, the MCF is expected to extend the applications of traditional textiles in antifouling, safety, the fragrance industry, and healthcare for the next-generation multifunctional fabrics.

Long-term Photo-degradation of Nanofibrous Composites Based on Poly(3-hydroxybutyrate) Electrospun Fibers Loaded with Zinc Oxide Nanoparticles

Composite mats based on submicron biopolyester fibers, such as poly(3-hydroxyalkanoate)s, and zinc oxide (ZnO) nanoparticles have been exploited in medicine and environmental areas, as antibacterial wound dressings or filters. Generally, the resulting mats have to be subjected to UV irradiation in order to promote the formation of reactive oxygen species, thus activating the antimicrobial or photocatalytic effect of ZnO. Therefore, investigation related to the influence of ZnO on poly(3-hydroxyalkanoate)s photo-degradation is required. In this context, the present paper addresses the long-term photo-degradation of nanofibrous poly(3-hydroxybutyrate) (PHB)/ZnO composites derived from two complementary electro-hydrodynamic techniques, namely electrospinning or electrospinning/electrospraying tandem processes. A thorough investigation of the as-obtained PHB/ZnO fibrous composites implying the utilization of ATR-FTIR, SEC, and SEM analysis pre- and post-aging under UV irradiation (313 nm) for a period of time of 500 h to study the effect of electro-hydrodynamic technique utilized and the ZnO content on the UV shielding properties of PHB mats.

Simultaneous enhancement of the thermal oxygen and ultraviolet aging resistance of asphalt by incorporating antioxidant intercalated layered double hydroxide

• Antioxidant 1222 intercalated LDHs (LDHs-1222) was successfully prepared. • LDHs-1222 has good UV shielding and free radical capture properties. • LDHs-1222 has good compatibility with asphalt. • LDHs-1222 enhanced thermal oxygen and UV ageing resistances of asphalt simultaneously. This research aims to enhance the anti-thermal oxygen and anti-ultraviolet aging properties of asphalt binder simultaneously with antioxidant intercalated UV-shielding material. For this purpose, the antioxidant 1222 with excellent thermal oxygen resistance was used to modify UV-shielding material layered double hydroxides (LDHs) to synthesize antioxidant 1222 intercalated LDHs (LDHs-1222). The crystal phase, chemical structure and micro-morphology of LDHs-1222 were characterized. The physical properties, storage stability, rheological properties and aging resistance of LDHs-1222 modified asphalt before and after thermal oxygen and UV aging were also investigated. The results showed that CO 3 2– in LDHs was substituted by phosphate group from antioxidant 1222, indicating the successful intercalation of antioxidant 1222. LDHs-1222 maintained the sheet structure and demonstrated a UV reflectivity of 70% and a radical scavenging efficiency of 84.53%, endowing it with desirable UV shielding property and free radical capture property. The incorporation of LDHs-1222 improved the storage stability of modified asphalt. LDHs-1222 modified asphalt exhibited lower complex modulus aging index, carbonyl index and sulfoxide index than LDHs, antioxidant 1222, and composite anti-ageing agent modified asphalts, indicating superior thermal oxygen ageing and UV aging resistance. 4% LDHs-1222 showed the most significant enhancement effect on anti-aging properties of asphalt.

Fabrication and Determination of the Sun Protection Factor and Ultraviolet Protection Factor for Piscean Collagen/Bischalcone Derivative (B1) Composite Films with Wide-Range UV Shielding.

The present study investigates the development of distinct UV-A and UV-B radiation filtering materials through the introduction of a heterocyclic bischalcone derivative [(3,5-bis{[4-(methylsulfanyl)phenyl]methylidene}piperidin-4-one] (B1) into the matrix of PVA/Piscean collagen blend films (1:1) prepared through the solution casting method and characterized. The dopant concentration varied from 0.25 to 4%. The scanning electron microscopy images showed the rough surface due to the uniform dispersion of dopant B1. The addition of different concentrations of B1 altered the mechanical strength with a proportional increase in Young’s modulus (146–317 MPa), tensile strength (23.3–39.21 MPa), and decrease in its elongation at break (158.8–105.2%). As the dopant B1 belongs to the bischalcone class of compounds which absorb in the UV–vis region (370 nm λmax) due to the α, β unsaturated keto group, it was selected for doping. Dopant concentration-dependent increase in density was observed in films (31–162 mg/cm3). The bathochromic shift in UV absorption from 370 to 390 nm for λmax as well as hyperchromism was evidenced with proportional increase in the concentration of B1, indicating its capacity to block UV rays. On determining the UV filtering ability for all the prepared films, the one with 4% dopant showed a higher sun protection factor (SPF) with a value of 27.53 and ultraviolet protection factor (UPF) with a value of 58.23. In addition, the degradation of supercoiled PBR322 DNA on UV irradiation was effectively inhibited by these films with a dopant concentration of 0.5–4.0%, which might cause less harm to the skin. The inferences of the experiments would indicate the use of these water-insoluble films as UV blocking potential materials with a merit of SPF and UPF characteristics.

Water Shielding in the Terrestrial Planet-forming Zone: Implication for Inner Disk Organics

The chemical composition of the inner region of protoplanetary disks can trace the composition of planetary-building material. The exact elemental composition of the inner disk has not yet been measured and tensions between models and observations still exist. Recent advancements have shown UV shielding to be able to increase the emission of organics. Here, we expand on these models and investigate how UV shielding may impact chemical composition in the inner 5 au. In this work, we use the model from Bosman et al. and expand it with a larger chemical network. We focus on the chemical abundances in the upper disk atmosphere where the effects of water UV shielding are most prominent and molecular lines originate. We find rich carbon and nitrogen chemistry with enhanced abundances of C2H2, CH4, HCN, CH3CN, and NH3 by >3 orders of magnitude. This is caused by the self-shielding of H2O, which locks oxygen in water. This subsequently results in a suppression of oxygen-containing species like CO and CO2. The increase in C2H2 seen in the model with the inclusion of water UV shielding allows us to explain the observed C2H2 abundance without resorting to elevated C/O ratios as water UV shielding induced an effectively oxygen-poor environment in oxygen-rich gas. Thus, water UV shielding is important for reproducing the observed abundances of hydrocarbons and nitriles. From our model result, species like CH4, NH3, and NO are expected to be observable with the James Webb Space Telescope (JWST).

κ-carrageenan-based pH-sensing films incorporated with anthocyanins or/and betacyanins extracted from purple sweet potatoes and peels of dragon fruits

Natural indicators (anthocyanins and betacyanins) were mixed in different volumetric ratios (3:1, 3:2, 1:1, 2:3 and 1:3) and used for the preparation of κ-carrageenan-based pH-sensing films. Anthocyanins and betacyanins were fixed into films by hydrogen bond, which changed the spatial structure of the κ-carrageenan films. Betacyanins reduced the crystallinity of κ-carrageenan films while anthocyanin had little effect on the crystallinity of the films. Betacyanins significantly improved the thermal stability of the film, while anthocyanins had little effect on it. In addition, anthocyanins and betacyanins significantly improved the oxidation resistance, water vapor permeability, ammonia sensitivity and UV shielding performance of the films. The complex films showed good color stability. It monitored the physical and chemical indexes of pork during storage, and measured the color change of indicator film during this process. Results showed that the color change of the film containing anthocyanins/betacyanins mixture in the volume ratio of 3:1 was the most significant with the pork spoilage. According to the correlation analysis and principal component analysis, total color differences(ΔE) can indicate the freshness of pork. Therefore, the pH sensing film prepared by us provides a reference for the freshness indication of pork.

Preparation and characterization of emamectin benzoate nanocapsules based on the dual role of polydopamine.

Developing pesticide-controlled release formulations with foliage adhesion has become the focus of current research in the field of crop protection. In this study, an excellent adhesive nanocapsule loaded with emamectin benzoate (Eb@PDA) was prepared via emulsion interfacial polymerization based on the self-polymerization ability and adhesion properties of polydopamine (PDA). The physicochemical properties of the Eb@PDA were characterized by scanning electron microscopy, transmission electron microscopy, particle size statistics, Fourier transform infrared spectroscopy and X-ray diffraction. The Eb@PDA presented a regular spherical shape, with an average particle size of 163.8 nm. Compared with conventional formulations, it had higher pesticide-loading content (34%) and excellent adhesion onto corn leaf. In addition, Eb@PDA showed sustained-release characteristics, facilitating the release of Eb at low pH and high temperature. Eb@PDA could effectively protect Eb against photodegradation and had a longer effective period for controlling Spodoptera frugiperda and Spodoptera exigua. Furthermore, acute toxicity tests showed that the 50% lethal concentration (LC50 ) was 80.91 and 57.91 mg kg-1 at 7 and 14 days, respectively, indicating a lower toxicity of the Eb@PDA to earthworms. The cells (L02) treated with Eb@PDA showed a higher cell viability but a lower apoptosis rate (only 5.75%), demonstrating the lower cytotoxicity of the Eb@PDA. The self-prepared Eb@PDA could be used as a formulation with the advantages of slow release, UV shielding, strong leaf adhesion, superior insecticidal properties, sustained effectiveness and biosafety. It will also facilitate the development of an efficient and safe pesticide delivery system. © 2022 Society of Chemical Industry.

Design of a ZnO@Plant Polyphenol/Poly(vinyl alcohol) Film via Plant Polyphenol-Induced Cross-Linking and Its Enhanced UV Shielding and Antibacterial Performance

Design of a ZnO@Plant Polyphenol/Poly(vinyl alcohol) Film via Plant Polyphenol-Induced Cross-Linking and Its Enhanced UV Shielding and Antibacterial Performance

Transparent and ultra-tough PVA/alkaline lignin films with UV shielding and antibacterial functions

Lignin and its derivatives can be used to make membranes with natural polymer materials for its properties including ultraviolet adsorption, biodegradable, antibacterial, and antioxidant. However, the lignin film has poor transparency due to the dark color, and how to control the proportion of each component to enhance properties is the main research topic. In this study, a polyvinyl alcohol /alkaline lignin (PVA/AL) composite film with excellent UV-shielding and visible-transparent performance successfully prepared by solution casting. By mixing with the N-halamine precursor 3-(2,3-dihydroxypropyl)-5,5-dimethylhydantoin (DPDMH), the composite film after chlorination showed superb antibacterial efficacy and could inactivate 6.85 log Escherichia coli (E. coli) and 6.57 log Staphylococcus aureus (S. aureus) respectively within 5 min of contact. Moreover, the composite film with 5 wt% AL exhibited ultra-high elongation of 449 % and toughness of 92 MJ/m3, and the toughness and malleability was greatly improved. In addition, with the introduction of AL, the composite film could shield 100 % of the UVB (320–275 nm) and UVC (275–200 nm) spectra and most of the UVA (400–320 nm) spectrum. The films prepared in this work are expected to find applications in promising fields such as in packaging materials and ultraviolet shielding.

Synthesis of Carbon Dots with Carbogenic π-Conjugated Domains for Full-Band UV Shielding

Our skin and materials are constantly exposed to detrimental ultraviolet light (UV) rays from the sun. It is essential to protect our health and the life of materials by intercepting this detrimental high-energy radiation with UV absorbers. Carbon dots (CDs) with low toxicity and low cost have brought a choice for UV absorbers. However, high-efficiency absorption CDs that can achieve absorption in the full ultraviolet region have rarely been reported. Herein, we synthesized a full-band carbon dot ultraviolet absorber by expanding the CD π-conjugation domain. In addition, by encapsulating CDs in a polyurethane (PU) matrix, the absorptivity of the 5 wt % CDs@PU film in the ultraviolet region was 100%, and the transmittance reached 90% in the visible region, successfully protecting the two dyes from photodegradation. The UV shielding efficiency slightly decreased under the accelerated aging experiment of 288 h. Moreover, to remove the ultraviolet light in the light-emitting diode (LED), we applied a layer of the CD film to the surface of the LED lamp, and the results indicated that the UV light was successfully blocked by the CD film without affecting the LED luminescence performance. This study offers a valid method to evolve high-efficiency, nontoxic antiaging materials and healthy lighting devices.

Designing Photothermal Superhydrophobic PET Fabrics via In Situ Polymerization and 1,4-Conjugation Addition Reaction.

This study demonstrates a simple and fast method to integrate superhydrophobicity, UV protection, and photothermal effect onto PET fabrics. The surface of PET fabric forms a hierarchical rough structure through in situ oxidative polymerization of the pyrrole (Py). The 1,4-conjugate addition reaction between pentaerythritol tetraacrylate, 3-aminopropyltriethoxysilane, and octadecyl acrylate not only endows the PET fabric with superhydrophobicity but also forms a cross-linked network structure which improves the stability of multifunctional coatings on the surface of the PET fabric. In addition, the wettability of the prepared PET fabric is investigated by adjusting the Py monomer and octadecyl acrylate concentration. The results reveal that the prepared PET fabrics exhibit obviously superhydrophobic behavior with a contact angle of 155.8°. The surface temperature of the superhydrophobic PPy/PET fabric can rise to 91 °C under a simulated sunlight which is much higher than the pristine PET fabric, while reaching basically the same steady-state in five heating/cooling cycles. The prepared PET fabric also possesses excellent self-cleaning, UV shielding, and solar light absorption performances. Furthermore, the superhydrophobic PET fabric exhibited excellent stability against 180 °C high temperature, strong UV radiation, different pH solutions and organic solvent erosion, 8 h washing tests, and 25 sandpaper abrasion cycles. These findings provide a path for the future development of multifunctional fabrics using fluorine-free environmentally friendly materials.

Biomimetic Chiral Photonic Materials with Tunable Metallic Colorations Prepared from Chiral Melanin-like Nanorods for UV Shielding, Humidity Sensing, and Cosmetics.

Many biological species combine the helical organization of cellulose or chitin microfibrils with broadband light absorption of black melanin to produce brilliant structural colors with metallic and glossy effects and other diverse functions. In this work, based on core-shell CNC@PDA chiral nanorods consisting of cellulose nanocrystals (CNCs) as the core and melanin-like polydopamine (PDA) as the shell that can form well-defined chiral liquid crystal phases, we report chiral photonic materials that closely mimic the unique coloration mechanisms and functionalities mastered by several biological species. The photonic films formed by such single CNC@PDA nanorods have brilliant iridescent structural colors originating from selective reflection of circularly polarized lights by the helical organization of CNC@PDAs across the films. Furthermore, the colors of such films have background-independent brightness, high visibility, and metallic effects that arise from the light absorption of the PDA component. Especially, the color ranges and metallic effects of the films can be conveniently tuned by varying the thickness of the PDA shell. In addition, the UV absorption and hygroscopic properties of PDA endow these CNC@PDA films with efficient broadband UV shielding and sensitive humidity-induced dynamic color changes. Due to the mussel-like superior adhesion of PDA, CNC@PDA-based photonic coatings can be formed conformably onto diverse kinds of substrates. A shiny eye shadow with viewing angle-dependent colorful patterns was used to demonstrate the potential applications. With combinations of multiple unique properties in one photonic material fabricated from a single building block, these CNC@PDA-based films are expected to have potential applications in cosmetics, UV protection, anticounterfeiting, chiral reflectors, etc.