Improved UV Stability Research Articles

Fabrication of N-halamine/MWPPy-ZnO hybrids based cellulose nanofibril composite films with improved UV-protective, antibacterial, and biofilm control functions

The design and fabrication of synergistic hybrid antibacterial materials is a promising approach for achieving effective sterilization while compensating for the deficiency of a single component. Despite being highly effective biocidal components, the poor UV light stability of some N-halamines limits their applications. This study was conducted to address this issue by the rational integration of cyclic N-halamine precursor (PGHAPA) with microwaved zinc oxide (MWPPy-ZnO) nanoparticles via covalent bonds and the preparation of cellulose nanofibrils based antibacterial composite films after chlorination (CNF/MWPPy-ZnO-PGHAPA-Cl). The proposed films offered tight lamellar structure, considerable thermal stability and better mechanical properties. The results from the FT-IR and XPS experiments provided the evidence of chemical reactions among the PGHAPA, MWPPy-ZnO, and CNF film. Notably, the CNF/MWPPy-ZnO-PGHAPA-Cl films showed improved UV stability with a chlorine content of up to 0.16 % after 24 h of irradiation, which was much greater than that of the CNF/PGHAPA-Cl films. Furthermore, the CNF/MWPPy-ZnO-PGHAPA-Cl films displayed rapid bactericidal activity, inactivating all the contacted Staphylococcus aureus and Escherichia coli O157:H7 strains within 5 min, along with prominent biofilm disruption, indicating great potential for daily food packaging applications.

Improved UV stability of perovskite devices based on the synergistic effect of electron layer passivation engineering and component engineering

The electron transport layer is one of the key factors in constructing high-performance perovskite solar cells (PSCs). Pb2+ reduction induced by ultraviolet light can cause the generation of vacancies and defects, leading to the degradation of perovskite films and the reduction of PSCs performances. Ethylenediamine tetraacetic acid disodium salt (EDTA) is a chelating agent that can bind to Sn2+ divalent metal ions and hence change material properties. Herein, EDTA-SnO2/CeO2 composite electron transport layers were constructed to improve the ultraviolet light stability of PSCs. The oxygen defect in electron layers of tin dioxide could be passivated by the surface of EDTA; whilst rod-like CeO2 was used as a mesoporous electron transport layer and UV shielding agent, which can reflect UV light and prevent the absorption layer from being damaged. CeO2 has also a suitable band gap; this accelerates the charge extraction and transfer, suppresses the recombination of interfacial carriers. The experimental results showed that the ultraviolet light stability of PSCs was significantly improved. After continuous irradiation of ultraviolet light with energy of 80 mW/cm2 for 12 h, the unencapsulated device with CeO2 maintained nearly 90% the initial efficiency.

Optimizing the formulation of Erwinia bacteriophages for improved UV stability and adsorption on apple leaves

Fire blight is a bacterial disease that affects plants of the Rosaceae family and causes significant economic losses worldwide. Although antibiotics have been used to control the disease, concerns about their environmental impact and the potential to promote antibiotic resistance have arisen. Bacteriophages are being investigated as an alternative to antibiotics; however, their efficacy can be affected by environmental stresses, such as UV radiation. In this study, we optimized the formulation of Erwinia phages to enhance their stability in the field, focusing on improving their UV stability and adsorption using adjuvants. Our results confirmed that 4.5 % polysorbate 80 and kaolin improve phage stability under UV stress, resulting in an 80 % increase in PFU value and improved UV protection efficacy. Adsorption assays also demonstrated that polysorbate 80 and kaolin improved the absorption efficiency, with phages detected in plant for up to two weeks. These findings demonstrate the effectiveness of the auxiliary formulation of Erwinia bacteriophages against environmental stress.

Durable and rechargeable antimicrobial cotton driven by enhanced UV stability and real-time detection of biocidal factors

In this study, graphene oxide/N-halamine nanocomposite was synthesized through Pickering miniemulsion polymerization, which was then coated on cotton surface. The modified cotton exhibited excellent superhydrophobicity, which could effectively prevent microbial infestation and reduce the probability of hydrolysis of active chlorine, with virtually no active chlorine released in water after 72 h. Deposition of reduced graphene oxide nanosheets endowed cotton with ultraviolet-blocking properties, attributing to enhanced UV adsorption and long UV paths. Moreover, encapsulation of polymeric N-halamine resulted in improved UV stability, thus extending the life of N-halamine-based agents. After 24 h of irradiation, 85 % of original biocidal component (active chlorine content) was retained, and approximately 97 % of initial chlorine could be regenerated. Modified cotton has been proven to be an effective oxidizing material against organic pollutants and a potential antimicrobial substance. Inoculated bacteria were completely killed after 1 and 10 min of contact time, respectively. An innovative and simple scheme for determination of active chlorine content was also devised, and real-time inspection of bactericidal activity could be achieved to assure antimicrobial sustainability. Moreover, this method could be utilized to evaluate hazard classification of microbial contamination in different locations, thus broadening the application scope of N-halamine-based cotton fabrics.

Design and characterization of polyurethane based electrospun systems modified with transition metals oxides for protective clothing applications

This paper reports the design and the fabrication of novel fiber membranes based on electrospun polyurethane (PU) fibers modified with copper and zinc oxide as potential systems for protective clothing. A one-step in-situ methodology is proposed to modify the PU systems. The modified PU membranes are widely characterized in terms of spectroscopic, morphological, thermal and barrier properties. Evaluation of surface charge and analysis of retention degree, obtained by testing four model systems (H2O, H2O/NaOH, lemon juice and sweat simulant), are even carried out. Then, to evaluate the protection against UV rays, weathering tests are accomplished while the carbonyl index gives a proof of the improved UV stability. The estimation of ultraviolet protection factor allowed to prove the total resistance to UV-A and UV-B rays. Finally, cytostatic effect against Gram+ and Gram- bacteria is evaluated. The reported results allow for stating that the designed materials show great potential as high-performance systems for protective clothing applications.

Enhanced UV stability of 2D perovskites (HO(CH2)4NH3)2(MA)n−1PbnI3n+1 due to hydrogen bonding

The 2D perovskites (HO(CH2)4NH3)2(MA)n−1PbnI3n+1 showed improved UV stability due to the hydrogen bonds between the hydroxyl groups of the organic spacer cations HO(CH2)4NH3+, compared with that of (CH3(CH2)3NH3)2PbI4 without the hydrogen bonds.

Learning From Plants: Lycopene Additive Passivation toward Efficient and “Fresh” Perovskite Solar Cells with Oxygen and Ultraviolet Resistance

AbstractCurrently, the photovoltaic performance of perovskite solar cells (PSCs) is closely linked to undermined defects in the perovskite, and the correct approach to ensure stability under practical conditions is still in dispute. Therefore, natural, healthy, and low‐cost additives are expected to not only reduce the trap sites but also drastically improve stability. In this work, the natural antioxidant additive lycopene extracted from tomatoes is introduced into PSCs. The results indicate that lycopene can passivate the grain boundaries, improve the crystallinity, reduce trap density, and facilitate the α phase formation of perovskite at room temperature. As a result, the power conversion efficiency (PCE) is considerably improved from 20.57% to 23.62% with vastly enhanced Jsc and Voc. Additionally, lycopene can eliminate the UV‐induced free radicals in the light aging process. The target device displays the enhanced hydrophobic, antioxidative properties, which demonstrates high O2 stability with 91.2% average PCE for 960 h, improved UV stability and long‐term stability with an average PCE of 92.4% after 3500 h. This work provides a strategy to solve the existing efficiency and stability issues in PSC devices through learning from natural plants, which paves the way for the development of environmentally friendly PSCs with high efficiency and stability, on the path toward industrialization.

Simple, green, ultrasound-assisted preparation of novel core-shell microcapsules from octyl methoxycinnamate and oligomeric proanthocyanidins for UV-stable sunscreen.

Without sunscreens, UV rays in sunlight cause skin damage, ranging from dark spots and premature aging to skin cancer. Present sunscreens, however, are readily photodegraded, producing highly reactive radicals that can damage cells. To address this problem, we have now used ultrasound to prepare core–shell microcapsules, which offer improved protection against UV light and improved UV stability. The composite microcapsules have oligomeric proanthocyanidins (OPCs), which are amphiphilic plant-derived secondary metabolites, as the shell and octyl methoxycinnamate (OMC), which is a UVB absorber, as the core. The polyphenolic flavonoid structure of OPCs improves the UV stability of OMC and thus avoids the skin damage caused by OMC photodegradation products. In the microcapsules, π–π stacking interactions between OPCs and OMC molecules enhance the ability of OMC to absorb UV radiation and extend the absorption range from the UVB region (280–320 nm) to include the UVA and UVC regions (200–400 nm). The composite microcapsules were shown to be stable on storage and to be non-irritant to human skin. The ultrasound-assisted preparation of OMC/OPCs composite microcapsules is simple, efficient and green and provides a feasible strategy for the development of novel, more effective, sunscreens.

Fabrication of uvioresistant poly(p‐phenylene benzobisoxazole) fibers based on hydrogen bond

ABSTRACTThe poly(p‐phenylene benzobisoxazole) (PBO) fiber with excellent performance is vulnerable to the irradiation of UV light, which significantly limits their application in advanced composites. Therefore, finding feasible and efficient ways to improve the uvioresistant properties of PBO fiber is of significance. In this work, a facile one‐pot method is developed for continuously preparing the PBO/poly(2,5‐dihydroxy‐1, 4‐phenylpyridimidazole) (PIPD) copolymer fiber to greatly enhance the anti‐UV properties of PBO fibers. The experimental results demonstrate that the fabricated PBO/PIPD copolymer fiber (molar ratio of 7:1) with greatly improved surface wetting properties (the maximum increase can reach about 179%) possesses satisfactory and desired uvioresistant performance, which is 30.8% higher than that of pure PBO fibers after 480 h UV aging irradiation. The fabricated PBO/PIPD copolymer fiber with improved UV stability has the potential to be applied to many important application areas even in a severe and harsh environment. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020, 137, 48432.

Patina-green coloured light emitting polycarbonate films: A synergistic extraction of improved UV endurance and considerate spectral down-conversion

Abstract A dramatic increase in UV endurance of polycarbonate (PC) films were achieved via thoughtful intercalation of cesium zincate (Cs2ZnO2) nanoparticles (NPs). The augmented UV endurance of PC/Cs2ZnO2 nanocomposite (NC) films were analyzed via yellowing index quantification and Fourier Transform Infrared (FTIR) measurements at 1713 cm−1. The foundation for improved UV stability was owed to Cs2ZnO2 NPs induced lessening of undesirable photo-degradation reactions. Moreover, the introduced NPs act to dissipate the high energy UV photons via polymer-nano metal oxide induced synergistic spectral down-conversion. The novel spectral down-conversion abilities and patina-green light emitting properties of PC/Cs2ZnO2 NC films were valued with UVA-transilluminator coupled fluorescence microscopic studies. Eventually, the synergistic combination of Cs2ZnO2 NPs with PC host, wherein the metal oxide offers protection against undesirable photo-degradation reactions, while the polymeric host guards the luminescence centers of nanostructured metal oxides are highly desirable for various photonic and opto-electronic applications.

Rhodium and platinum hydrosilylation catalysts for increasing UV stability of poly(dimethylsiloxane) in geostationary environment

Poly(dimethylsiloxane) (PDMS) resins are widely used for aerospace applications due to their unique properties, such as a high flexibility, good thermal stability and optical transparency in the visible-near-infrared spectral region. Generally, PDMS networks are obtained by hydrosilylation with highly active platinum catalysts (Pt (0) Karstedt). The exposure of such PDMS resins to strong UV irradiations leads to the formation of colloïdal platinum species, and consequently to a loss of optical transparency. Various organometallic derivatives such as chloro (1,5-cyclooctadiene) rhodium (I) dimer (Rh 1), chloronorbornadiene rhodium (I) dimer (Rh 2), and dichloro (1,5-cyclooctadiene) platinum (II) (Pt 2) were studied as alternative catalysts for the cross-linking of PDMS. These catalytic systems show high cross-linking efficiencies leading to transparent PDMS resins with small size colloids formation as compared to the Karstedt system. The properties of cross-linked PDMS resins before and after UV irradiations were investigated by dynamic mechanical analysis, thermogravimetric analysis, differential scanning calorimetry, and Vis-NIR spectroscopy. The thermal stability of cross-linked PDMS by all new catalytic systems was increased from 405 °C to 480 °C. After UV irradiations under geostationary conditions, an improved UV stability (up to 12.2%) was observed for the wavelength range 250–400 nm with the Pt 2 catalyst.

Antimicrobial Cellulose Modified with Nanotitania and Cyclic N-Halamine

Organic–inorganic composites have the drawn attention of researchers due to their combined properties. In this work, poly[5,5-dimethyl-3-(3′-triethoxysilylpropyl)hydantoin] (PSPH) was synthesized and coated onto cotton fibers together with titania nanoparticles (TiO2) by chemical binding in a one-bath process. The treated cotton with improved UV stability can produce biocidal properties against S. aureus (ATCC 6538) and E. coli O157:H7 (ATCC 43895) upon chlorination with diluted sodium hypochlorite solutions. The characteristics of the coated cotton were determined by SEM, FTIR, XRD, and XPS, and the washing stability and antibacterial efficacies were tested. Moreover, the N–Cl bond and compound stability under UV irradiation were measured. It was found that the treated cotton showed excellent antimicrobial properties within a brief contact time and great washing stability. The N–Cl bond and compound itself showed excellent stability under UV light irradiation.

Analysis of the degradation mechanism of ITO-free organic solar cells under UV radiation

This work reports on the stability of encapsulated ITO-free bulk heterojunction organic solar cells (BHJ-OSC) under UV radiation in ambient air with the layer sequence Cr/Al/Cr/photoactive layer (PAL)/poly (3, 4-ethylenedioxythiophene) poly (styrenesulfonate) (PEDOT:PSS)/metal-grid. The PAL consisted of poly(3-hexylthiophene) (P3HT) as a donor and (6,6)-phenyl-C60 butyric acid methyl ester (PCBM) as an acceptor. BHJ-OSC with this setup showed remarkable stability under continuous illumination (1000W/m2) with a low UV content. In contrast, the devices degraded significantly under UV radiation which was characterized by a reduction in fill factor and short-circuit current density. Additional experiments revealed an increase of the sheet resistance of the PEDOT:PSS layer which was interestingly much more pronounced in pure PEDOT:PSS samples as compared to samples where a PAL was deposited underneath. In addition, current extraction by linear increasing voltage (CELIV) measurements indicated a decrease of the effective charge carrier mobility of the PAL. Numerical simulations based on the experimentally determined parameters showed good agreement of the solar cell performance as a function of UV exposure duration. This suggests that the increase of the sheet resistance of the polymeric hole contact and to a lesser extent the change of the effective mobility of the PAL are the main factors governing the deterioration of the photovoltaic performance upon UV exposure. A comparison to devices with a setup ITO/ZnO/PAL/PEDOT:PSS and a full metallization showed clearly improved UV stability, although the absorption of UV in the PAL is very similar. This further supports our interpretation that the degradation of the PAL plays a very minor role. The issue with the degradation of the PEDOT:PSS can easily be solved by incorporating an UV-filter into the device or preferably the use of UV-stabilized PEDOT:PSS formulations.

Improved UV stability of antibacterial coatings with N-halamine/TiO2

The outstanding advantages of N-halamine materials over other antimicrobial materials are their durable and rechargeable antimicrobial properties, as well as their efficacies in inactivating a broad spectrum of pathogens. Theoretically, the oxidative chlorine of antimicrobial cotton coated with N-halamine hydantoin diol can be restored upon loss of its biocidal efficacy after exposure to ultraviolet light. In this work nano-titania particles were added into the coating solutions containing N-halamine diol and 1,2,3,4-butanetetracarboxylic acid (BTCA), and the coatings were applied to produce antimicrobial cellulose with improved UV stability. The treated cotton fabrics were characterized by FT-IR, SEM, XRD, and XPS. The effects of the coatings on tensile strength and wrinkle recovery angle were investigated. Biocidal efficacies of fabrics coated with hydantoin diol and diol/TiO2 against Staphylococcus aureus (ATCC 6538) and Escherichia coli O157:H7 (ATCC 43895) were determined using a modified AATCC 100-1999 method and showed excellent antimicrobial properties against these two bacterial species within a brief contact times. It was found that the addition of Nano-TiO2 in the antimicrobial coatings, especially rutile titanium dioxide, could improve the UV light stability of the chlorinated fabrics coated with hydantoin diol significantly. The UV light stability of N-halamine coatings were enhanced with increasing amounts of rutile TiO2.

Starch-quercetin conjugate by radical grafting: synthesis and biological characterization

A novel flavonoid-polysaccharide conjugate was synthesized by free radical grafting of quercetin on starch. The covalent insertion of quercetin in the polymeric chain was confirmed by FT-IR, DSC and fluorescence analyses, while an estimation of the amount of quercetin bound per g of polymer was obtained by the Folin-Ciocalteu assay. The conjugate shows improved UV stability and retains the antioxidant properties of free quercetin, such as scavenging activity towards free radicals (DPPH and peroxynitrite); inhibition of the free radical formation (peroxidation of linoleic acid) and total antioxidant activity. The conjugate also prevented drug degradation and shows potential health functionality in the treatment of Alzheimer disease, diabetes and as skin-whitening agent.

Benzoyl germanium derivatives as novel visible light photoinitiators for dental materials

Objectives The objective of this study was to investigate the use of benzoyl germanium derivatives as a novel visible light photoinitiator of resin-based dental composites. Selected mechanical properties, such as flexural strength and flexural modulus, setting time, storage stability, and UV light stability, of the composites based on the novel photoinitiators benzoyltrimethylgermane (BTMGe) or dibenzoyldiethylgermane (DBDEGe) were investigated and compared to the properties of materials that are cured with a mixture of camphorquinone (CQ) and ethyl 4-( N, N-dimethylamino)benzoate (EMBO). Methods The flexural strength and flexural modulus of elasticity were determined according to ISO 4049. For this purpose, test specimens (2 mm × 2 mm × 25 mm) of the composites investigated were prepared in stainless steel moulds and light-cured (150 mW/cm 2, 2 s × 180 s). The flexural strength and flexural modulus of elasticity were measured after immersing the cured specimens in water for 24 h at 37 °C and in certain cases, after they had been boiled for 24 h in water. In addition, the setting time, curing depth, storage and UV stability of selected composites were determined. Results The novel photoinitiators BTMGe or DBDEGe can be used to substitute the binary photoinitiator CQ/EMBO in visible light-cured restorative composites. Especially, DBDEGe showed a significantly higher photocuring activity in composites with a filler load of about 60 wt. % in comparison to that of CQ/EMBO. In addition, composites based on BTMGe or DBDEGe showed an improved UV stability and a storage stability comparable to that of CQ/EMBO-based composites.

Natural weathering test for films of various formulations of low density polyethylene (LDPE) and linear low density polyethylene (LLDPE)

Natural (outdoor) weathering test was performed to investigate the UV stability of thin films (0.06 mm) of linear low density polyethylene (LLDPE) and low density polyethylene (LDPE). The PE films were prepared from various formulations of LLDPE and LDPE resins. Some of these films contained a single high molecular mass HALS only, along with a primary antioxidant (i.e. Irganox 1010) and a secondary antioxidant (i.e. Irgafos 168 or Alkanox TNPP), while others contained HALS and UVA (i.e. Chimassorb 81 or Tinuvin P or Tinuvin 326) along with these antioxidants. The HALS used was either an oligomeric or a synergistic mixture of a high molecular mass (HMM) hindered amine stabilizer and co-additives. The UV stability was investigated by exposing the prepared films at 45° towards south in the direct sunshine up to 365 days. Fifty percent of tensile strength retention was determined for all these exposed films and it was found that the films containing a single HALS gained improved UV stability by about two to 12 fold over the pure films. On the other hand, films that contained a combination of HALS and UVA obtained further improved UV stability over the films containing a single HALS (both have antioxidants). Films containing a single HALS reached 50% TS retention within 205 days, whereas, films containing a combination of HALS and UVA reached 50% TS retention within 590 days, which is about three times further improvement in UV stability.

P‐27: Polyarylate Films for Optical Applications with Improved UV‐Resistance

AbstractOptical films can be made by novel polyarylates with improved UV stability, light transparency and heat‐resistance. The present work relates to novel polyarylates made of bis(hydroxyphenyl)fluorene ortho disubstituted bisphenols. These materials feature a broad range of properties useful for optical applications, particularly for plastic and flexible FPD substrates.

Surface-Anchored Hindered-Amine Light Stabilizers for Improved UV Stability of Polyolefins

Abstract Hindered-amine light stabilizers (HALS) were surface anchored to polyolefin films by reacting the HALS, namely, 1,2,2,6,6-pentamethyl-4-piperidinol and 1,2,2,6,6-pentamethyl-4-aminopiperidine, with succinic anhydride functionalized polyolefin surfaces. The photostability of polyolefin films with surface-anchored HALS were compared with films stabilized with commercial HALS (Tinuvin 770) by melt blending. It is shown that the photostabilizing efficiency of surface-anchored HALS is superior that of melt-blended polyolefins.