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Microplastics (MPs) experienced different aging processes in environment. Literatures about effect of artificially-accelerated aging on MPs behavior are still insufficient. The accelerated process induced by ultraviolet(UV)-activated persulfate (PS) is a promising technology for obtaining different aged MPs to understand long-term aging behavior. In the work, the aging behavior of polyvinyl chloride (PVC) accelerated by UV/PS system were investigated. It exhibited a dechlorination with 58.495 ± 6.090 mg/L Cl - release after 35 h UV-activated PS (0.01 M) process. The treatment led to significant alternations on surface morphology and chemical feature of PVC. The crystallinity was increased, and average size was reduced from 154.11 µm to 119.28 µm with aging time. Subsequently, many smaller size particles were produced. Furthermore, the process induced the breaking of backbone. Simultaneously, more oxygen-containing functional groups were identified. The oxidation reaction accelerated by sulfate radical (SO 4 •− ) and reactive oxygen species (ROS) was predominant, which immensely promoted aging process. Sustained high levels of free radical contributed to production of alcohols and carboxylic acids short chain organics. The study explored aging behavior of PVC accelerated by UV/PS system, which could be helpful for understanding environmental behavior and providing further information to assess potential risks of MPs.
The resorcinol diglycidyl acrylate (RDA) is firmly introduced to the surface of polyester (PET) fibers by a simple dip-rolling and baking method, and a free radical polymerization reaction is initiated on the surface of PET fabrics under ultraviolet light (UV) light to obtain three hydrogel layers with different structure, including polyacrylamide (PAAM), polyacrylic acid (PAAC) and poly-N-isopropylacrylamide (PNIPAAM). It is shown that the pretreatment-UV grafting method can be used to obtain hydrogel layers with porous structure on the surface of PET fabric, and all three hydrogel layers have better frictional properties than kelp. Among them, the friction coefficient of PET-PAAM surface can reach 0.02, which is 17% of the friction coefficient of kelp surface and 83% lower than that of the untreated PET fabric surface, giving the PET fabric surface excellent interfacial drag reduction characteristics. It can be applied to the surface of underwater activity equipment as well as ships to improve moving efficiency and reduce energy consumption.
A UV Nonlinear optical (NLO) crystal is one of the key devices in all-solid-state laser technology, and borate halides show outstanding potential due to their abundant structural diversity and short UV cut-off edges. In this article, the sizable UV NLO crystal of K3B6O10Br (KBOB) has been grown with lead-containing and lead-free fluxes systems using the high-temperature top-seeded solution growth (TSSG) method. Energy Dispersive X-ray Spectroscopy (EDS) and transmittance spectra illustrate the influence of Pb2+ions on the transmittance properties and laser-induced damage threshold (LDT). The thermal property, namely, thermal expansion, thermal conductivity, and thermal diffusivity curves, were characterized. Moreover, a small variation of thermal refractive indexes was analyzed to illustrate the advantage of KBOB in the application for temperature-fluctuated specific regions.Keywords:top-seeded solution growth;K3B6O10Br;nonlinear optical crystal;lead-free fluxes;optical property;thermal property
Three-dimensional (3D) cell culture using hydrogel scaffolds can closely resemble the natural extracellular matrix (ECM), which offers appropriate mechanical support for cells and regulates cellular behavior. In this study, a bacterial transpeptidase sortase A (SA) is used to prepare enzymatically cross-linked methacrylated hyaluronic acid (HA) peptides (HAMA-P) hydrogel, which reveals fast gel kinetics under high SA cross-linking concentrations and can be used as an injection hydrogel for tissue repair or extrusive 3D bioprinting. Furthermore, methacrylated gelatin (GelMA) is introduced to build the hybrid hydrogel (HAMA-P-GelMA) with double cross-linking of enzyme-UV, which has shown proper physical properties (mechanical properties, swelling, degradation rate, etc.) of the hydrogel matrix, and displayed desirable effects on cell viability, adhesion, and cell spreading, when compared to GelMA or HAMA-P single-network hydrogels. The HAMA-P-GelMA hybrid hydrogels provide a favorable 3D milieu for cell growth and can be used as a 3D bio-ink or a carrier of stem cells/cytokines for injectable tissue repair and filling.
In this research, a 3D printing technique was employed for processing biobased composites of polyacrylated epoxidized soybean oil (AESO) with modified ethyl cellulose macromonomer (ECM). In this 3D printing process, objects are built in a layer-by-layer fashion by depositing formulated liquid solutions on a platform and rapidly transformed into a solid film cured by UV light. The sustainable materials consisting of ECM and AESO biopolymer were examined for their physical and thermal properties. Samples with different ECM and AESO weight ratios were prepared. Tensile test results showed the ECM-AESO composites had higher strength and stiffness than AESO alone. Their tensile strengths with ECM weight contents from 30 wt.% to 5 wt.% are between 11.5 MPa and 5.9 MPa and Young's moduli are between 167 MPa and 56 MPa, compared to AESO polymer itself with 4.3 MPa and 27.4 MPa, respectively. Further, the glass transition temperatures of all ECM-AESO composites were increased from 57.4 to 82.2°C, compared to AESO polymer itself with 47.1°C. Thermal properties of the ECM-AESO composites are stable up to 325°C. These materials may be of great environmental interest because these composites consist of high amounts of agricultural resources.
Designing soy protein (SP)-based composite films with great toughness and high strength remains an intractable challenge. In this work, a facile strategy for preparing SP-based composite films by incorporating polyethyleneimine (PEI) as plasticizer and lignin-Ag nanoparticles (NPs) as green reinforcer is proposed. The fabricated films exhibit great toughness of 15.22 MJ m −3 , high tensile strength of 10.44 MPa, which are 375.6 % and 493.2 % increase compared with that of the neat glycerol-toughened SP film. The films also perform a high strain at failure of 188.48 %. In addition, the developed composite films have good biodegradability and excellent UV-shielding performance, which can block 100 % of the UV spectrum. This work offers a novel method for fabricating SP-based films with great toughness, ductility, and strength for many potential applications, such as packaging engineering and UV-blocking areas.
Polymeric coatings are usually threatened by some harsh environment factors, which induce the formation of cracks or loss of functional components. Traditional extrinsic self-healing coatings usually have only one single repair mode (crack-repairing or function-restoring mode) that may not be powerful enough to meet the complex repair needs in practical applications. Herein, we first report a UV-responsive, dual-functional, fully-utilized microsphere-based system for highly efficient self-healing coatings, in which the UV-reversible coumarin crosslinking shells can not only encapsulate and release functional compounds as the function-repairing agents, but also participate in self-healing process as the crack-repairing agents, thus realizing two modes of repair with 100% of utilization efficiency of microspheres.
Carbon-based fluorescent security labels are effective methods to prevent counterfeiting. However, the properties of poor optical stability, complex and energy-consuming synthesis processes and weak bonding with substrates of carbon-based fluorescent materials limit their application prospects. Here, a novel in situ fluorescent patterning strategy is developed to achieve covert, chemically stable and solvent-tolerant cellulose-based security labels by UV exposure. The unsaturated double bonds as the origin of the fluorescence were generated during the photodegradation process under UV exposure. The fluorescent emission of cellulose-based materials reveals excellent stability under acidic, alkaline, reducing, oxidizing and non-polar solvent environments. These advantages give the cellulose nanofiber based security label fantastic potential applications.
Tyrosinase is a key metalloenzyme for the biosynthesis of melanin that plays a critical role in the prevention of skin damage caused by ultraviolet (UV) radiation. However, the overproduction of melanin may cause a variety of skin diseases. Due to the toxicity and inefficiency of existing tyrosinase inhibitors, it is urgent to identify safe and potent alternatives from natural sources. Theaflavin, a single-component extracted from black tea, has been found to possess a variety of pharmacological activities. Herein, the inhibition kinetics of theaflavin on tyrosinase and inhibitory mechanism were determined using spectroscopy, molecular docking, and zebrafish model. The results showed that theaflavin inhibited the diphenolase activity of tyrosinase in a reversible mixed type manner with IC 50 of 229.75 μmol/L and hindered the synthesis of melanin in zebrafish. This may be due to the formation of eight hydrogen bonds and hydrophobic effects between theaflavin and tyrosinase according to the results of molecular docking. To study the possible effects on the prevention of free radical-mediated skin cancer and photoaging caused by UV radiation, the antioxidation and UV filter properties of theaflavin were further verified. This study demonstrates that theaflavin is a potential multifunctional compound that can be used in cosmetic and medicinal products.
The efficiency of Congo red (CR) removal by low-pressure ultraviolet photolysis of nitrate (UV/NO 3 − ) process was investigated in this study. Results showed that CR degradation through direct UV (254 nm) photolysis could be ignored, but CR was obviously removed in UV/NO 3 − process. Moreover, the contributions of UV, NO 2 and OH to the degradation of CR were explored to be roughly 0.63%, 17.46% and 81.90%, respectively. In addition, the observed pseudo-first-order rate constants for the degradation of CR ( k obs ) were assessed by the effects of different water matrices and operation conditions, including NO 3 − dosage, CR concentration, solution pH, chloride ion (Cl − ), natural organic matter (NOM) and carbonate/bicarbonate (CO 3 2− /HCO 3 − ). The k obs was increased by nearly 12.9 times with the addition of NO 3 − dosage from 1 mM to 200 mM due to the generation of more active components (e.g., OH and NO 2 ). Higher doses of CR reduced the k obs , which could be attributed to the filter effects of CR on UV irradiation. Although the photolysis of NO 3 − could be expedited under acidic conditions, the k obs was decelerated because of the protonation of CR (pKa = 4.1, 25 °C). While in alkaline conditions, the k obs was also reduced as the decrease in redox potential of OH. The presence of Cl − (0–7 mM) exhibited no scavenging effect on the k obs , which suggested the secondary radicals (i.e., chlorine radicals (e.g., Cl , Cl 2 − )) could oxidize CR effectively. NOM restricted the degradation of CR significantly, resulting from the filter effects of NOM ( ε = 0.11 L mgC −1 cm −1 ) on UV and the effects of radical scavenging. The k obs was improved obviously with the participation of CO 3 2− /HCO 3 − (0–7 mM), ascribing to the oxidation of carbonate radical (CO 3 − ) and the increased steady state concentration of NO 2 . The degradation of CR in UV/NO 3 − process has the potential for practical applications in real water. Furthermore, eight intermediates were proposed by Liquid chromatography-tandem mass spectrometry (LC-MS/MS). Hydroxylation, nitrification and other aromatic products in the reaction of CR with OH and/or NO 2 were readily produced by H-abstraction, addition reaction and electron transfer.
ABSTRACT In recent years, the combination of perovskites with other materials to improve the photoelectric performance has received widespread attention. In this work, we demonstrate a hybrid heterostructure photodetector with the combination of GaN microwire array and perovskite. Compared to perovskite and GaN microwire array photodetectors, the hybrid CH 3 NH 3 PbI 3- x Cl x /GaN microwire array photodetector exhibits more excellent photoelectric performances in a wide detection range from ultraviolet to visible. Under 325 nm laser irradiation, the hybrid photodetector generates a large photocurrent (1.04 ×10 -5 A), a high on/off ratio (>10 4 ), a fast response time (raise time of 0.66 ms and decay time of 0.71 ms), and higher responsivity , detectivity. Meanwhile, when the perovskite is combined with the GaN microwire array, the device also has a higher photocurrent, on/off ratio, and faster photoresponse compared with the perovskite photodetector in the visible light region. This is interpreted as the effective separation photogenerated carriers at the hetero-interface, and the directional transfer of carriers within the one-dimensional GaN microwire array. This study sheds light on fabricating high-performance heterostructures photodetectors.
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