UV Light Stability Research Articles

Mechanically and Ultraviolet Light Stable Ultrathin Organic Solar Cell via Semi-Embedding Silver Nanowires in a Hydrogen Bonds-Based Polyimide.

Ultrathin organic solar cells (OSCs) with both high power conversion efficiency (PCE) and operational stability are of great significance for the industrial applications but still challenging. Here, a polyimide (PI) substrate for high-performance and stable ultrathin OSCs, which is physically crosslinked via strong hydrogen bonds (denoted as HB-PI) to enhance the mechanical, thermal, solvent-resistant, and UV filtering properties (with a cut-off wavelength of 376nm), is synthesized. An ultrathin flexible transparent composite electrode (FTCE, ≈7µm) is fabricated via semi-embedding AgNWs in the HB-PI substrate. The FTCE possesses excellent optoelectronic property, smooth surface, and high mechanical stability simultaneously. Based on this FTCE, an ultrathin OSC is constructed with a PCE of 13.52% (average of 13.22%). Moreover, the ultrathin OSC shows outstanding mechanical stability (PCE decreased by less than 4% after 1000 bending cycles at a small bending radius of 0.5mm) and superior UV light stability (no evident PCE degradation after irradiation under UV light for 10h). This work will provide a new avenue for fabricating high-performance and stable ultrathin OSCs.

Mixed-surfactant perovskites with enhanced photostability

Blue and green emitting methylammonium lead bromide perovskite particles with improved UV-light stability have been developed by tuning structure and stabilization with a mixture of different single- and double-tailed surfactants. The ratio of the long alkyl chain surfactants to the methyl ammonium bromide allows for tailoring of the emission color of ready to use perovskite particles without further purification processes. The combination of single and double tailed surfactants exceeds the properties and geometries of the perovskite particles obtainable with a single surfactant. With a mixture of octylammonium bromide and dimethyldioctadecyl bromide, the perovskite particles show a highly anisotropic shape with a layered pyramid structure. The effect of surfactant composition on the perovskite particles’ structure, morphology and light-emitting properties has been elucidated. As these mixed surfactant perovskites are more robust against UV-light than other perovskite particles, they bear great potential for applications in optical devices such as LEDs.

AIE Molecules UV‐Filtering Effect Improves the Photostability of Organic Solar Cells

AbstractDue to the poor stability of organic solar cells (OSCs), especially ultraviolet light (UV) stability, they are not yet up to the standard for commercial applications. Inverted devices based on the ZnO electron transport layer (ETL) are relatively thermal‐ and air‐stable, while their UV light stability is poor. Moreover, the active layer materials undergo severe degradation under UV light, which also causes the degradation of the device. Here, aggregation‐induced emission (AIE) molecules as an optical barrier layer are coated between ZnO‐ETL and active layer to fabricate efficient OSCs with excellent UV photostability. AIE molecules can avoid direct photodegradation of the active layer materials by absorbing UV light. At the same time, they can passivate the oxygen defects on the ZnO surface and prevent photocatalytic degradation of the active layer materials. Therefore, the ZnO/TPIZ‐based devices maintain 84% of the original power conversion efficiency (PCE) with continuous irradiation by 5 mW cm–2 UV light (365 nm) for 1500 h, and similarly T80 for more than 700 h under 20 mW cm–2 UV light exposure. Moreover, the ZnO/TPIZ‐based devices also preserve excellent thermal stability accompanying the upgrading of PCE.

Effect of UV, pH and solvent on the photophysical properties of novel xanthylium fluorophore in solid and liquid state

The current work describes the comparative study of the photophysical properties of new series of xanthylium fluorophore in different organic solvents, the effect of pH, and the effects of UV light irradiation and stability. The designed molecule plays a significant role in the stability. We disclosed the synthesized molecule's stability from UV–Vis, fluorescence, theoretical studies, the molecule sensitivity to solvent polarity, and pH due to its structural nature. The decrease in absorbance and fluorescence intensity with UV–visible light irradiation for the solid and liquid samples were studied. The dye discoloration rate was estimated. The mechanism for the same has been explored, and the information is given in detail. The electrostatic potential, surface mapping analysis, and the stability of the synthesized dye molecules were studied theoretically and compared with the experimental outcome. The stability study and other factors allowed us to predict the suitable application of the synthesized xanthylium fluorophore.

Chirality Transfer from Chiral Mesoporous Silica to Perovskite CsPbBr 3 Nanocrystals: The Role of Chiral Confinement

Chirality Transfer from Chiral Mesoporous Silica to Perovskite CsPbBr ₃ Nanocrystals: The Role of Chiral Confinement

Passivation of iodine vacancies of perovskite films by reducing iodine to triiodide anions for high-performance photovoltaics

Inverted perovskite solar cells (PSCs) exhibit great potential in large-scale fabrication due to the low-temperature manufacturing process and low cost compared to normal PSCs. However, defects at the surface and grain boundaries (GBs) of perovskite films, such as iodine vacancies, lead to low efficiency and poor stability. Herein, we report a strategy to passivate the defects in situ with tetrabutylammonium chloride (TABCl). Both the surface defects and GB defects are passivated after perovskite film growth. Moreover, TABCl modifies iodine vacancies by reducing I2 to iodide ions, leading to a decrease in charge recombination in the films and enhanced device performance. The power conversion efficiency (PCE) of devices increases from 18.52% to 20.36 % by TBACl modification, and TBACl also reduces the Voc loss in the PSCs. Meanwhile, TBACl enhances the UV light stability of devices tested by continuous UV light irradiation due to the decreased defects by TBACl. The PSCs could maintain over 90% PCE under continuous UV light irradiation for 450 min. This work not only presents a method to effectively passivate the defects in situ including the surface defects and GB defects but also demonstrates a novel strategy to modify the iodine vacancies by the reducibility of TBACl. In addition, the reducibility of TBACl suppresses the degradation of perovskite films, leading to improved stability.

Investigations of Fused Deposition Modeling for Perovskite Active Solar Cells.

The advent of Fused Deposition Modeling (FDM; or 3D printing) has significantly changed the way many products are designed and built. It has even opened opportunities to fabricate new products on-site and on-demand. In addition, parallel efforts that introduce new materials into the FDM process have seen great advances as well. New additives have been demonstrably utilized to achieve thermal, electrical, and structural property improvements. This combination of fabrication flexibility and material additives make FDM an ideal candidate for investigation of perovskite materials in new solar cell efforts. In this work, we fabricate and characterize a perovskite-based solar cell polymer designed for the FDM fabrication processes. Perovskite solar cells have garnered major research interest since their discovery in 2009. Perovskites, specifically methylammonium lead iodide, offer beneficial properties to solar cell fabrication such as long minority charge carrier distance, high light absorption, and simple fabrication methods. Despite the great potential of these materials, however, stability remains an issue in solar cell utilization as the material degrades under ultraviolet light, exposure to oxygen and water, as well as increased temperatures. To mitigate degradation, different fabrication methods have been utilized. Additionally, multiple groups have utilized encapsulation methods post-fabrication and in situ solution processed integration of polymer materials into the solar cell to prevent degradation. In this paper, we leverage the unique ability of FDM to encapsulate perovskite materials and yield a MAPbI3-PCL solar material as the active layer for solar cell use. In this manner, increased ability to resist UV light degradation and material stability from other environmental factors can be achieved. This study provides characterization of the material via multiple techniques like SEM (Scanning Electron Microscopy) and XRD (X-ray Diffraction) as well as absorbance, transmittance, and photocurrent response. Investigations of processing on perovskite degradation as well as initial solar simulated response are recorded. Unique aspects of the resulting material and process are noted including improved performance with increased operating temperature. Increased electron–hole pair generation is observed for 200 m FDM-printed PCL film, achieving a 45% reduction in resistance under peak incident flux of 590 W/m with the addition of MAPbl3. This work establishes insight into the use of FDM for full solar cell fabrication and points to the next steps of research and development in this growing field.

Comparing the effect of whey protein preheating temperatures on the color expression and stability of anthocyanins from different sources

Anthocyanins (ACN) are natural colorants that provide bright colors to food products. However, their limited stability in food matrices represents a challenge to their application. Whey protein (WP) has the potential to interact with ACN and enhance their color stability. This study compared the effects of WP preheating temperature on color, stability (heat, UV light and storage) and antioxidation capacity of three different commercial ACN-based colorants. WP (1 mg/mL) was preheated from 40 to 80 °C for 30 min. ACN from grape, purple corn or black carrot were added to the preheated or native WP solutions and the mixtures were stored in the dark at 4 °C for 4 weeks to evaluate their storage stability. Antioxidation capacity was measured using the DPPH method. Heat stability was tested by heating WP-ACN mixtures at 90 °C for 2 h. UV light stability was measured by exposing the samples to 254 nm UV light for up to 150mins. WP addition improved ACN color stability during storage, with the smallest color change occurring when WP was preheated to 50 °C. UV light-induced ACN color degradation decreased by 10–20% (p < 0.05) with WP addition. Antioxidant capacity decreased significantly (p < 0.05) after addition of WP, while increased ACN survival. Increasing WP preheating temperature resulted in higher ACN heat stability and antioxidant capacity but lower UV-light stability. WP protected ACN from degradation, and this protection was affected by WP pre-heating temperatures as well as ACN structures. ACN and WP could be combined to improve the performance of commercially available anthocyanin-based food colorants.

Enhanced degradation of ultra-violet stabilizer Bis(4-hydroxy)benzophenone using oxone catalyzed by hexagonal nanoplate-assembled CoS 3-dimensional cluster

As UV-light stabilizers, Bis(4-hydroxy)benzophenone (BBP), are extensively consumed to quench radicals from photooxidation, continuous release of BPs into the environment poses serious threats to the ecology in view of their xenohormone toxicities, and BBP shall be eliminated from water to avoid its adverse effect. Since sulfate radical (SR)-based chemical oxidation techniques have been proven as effective procedures for eliminating organic emerging contaminants, this study aims to develop useful SR-based procedures through activating Oxone for degrading BBP in water. In contrast to the conventional Co3O4, cobalt sulfide (CoS) is particularly proposed as an alternative heterogeneous catalyst for activating Oxone to degrade BBP because CoS exhibits more reactive redox characteristics. As structures of catalysts predominantly control their catalytic activities, in this study, a unique nanoplate-assembled CoS (NPCS) 3D cluster is fabricated via a convenient one-step process to serve as a promising heterogeneous catalyst for activating Oxone to degrade BBP. With NPCS = 100 mg/L and Oxone = 200 mg/L, 5 mg/L of BBP can be completely eliminated in 60 min. The catalytic activity of NPCS towards Oxone activation also significantly surpasses the reference material, Co3O4, to enhance degradation of BBP. Ea of BBP degradation by NPCS-activated Oxone is also determined as a relatively low value of 42.7 kJ/mol. The activation mechanism as well as degradation pathway of BBP degradation by NPCS-activated Oxone was investigated and validated through experimental evidences and density functional theory (DFT) calculation to offer valuable insights into degradation behaviors for developing SR-based processes of BBP degradation using CoS catalysts.

Ultraviolet light exposure degradation effect on the properties of nanocrystalline cellulose-reinforced polyvinyl alcohol composite film

PVA used in packaging applications has been faced with a UV light degradation challenge, which often reduces its durability while in use. The UV light stability enhancement effect of nanocrystalline cellulose (NCC) reinforcement in PVA was studied. Polyvinyl alcohol composite film was reinforced with NCC from palm oil waste (PVA-NCC film) and exposed to UV light (22 W, SUV-16 254 nm) for different time duration to study the material durability enhancement. The percentage weight loss of the samples was measured to observe the UV light degradation effect. Furthermore, the samples’ structural, morphological, and tensile properties were studied before and after exposure to UV light with FT-IR, scanning electron microscopy (SEM), and tensile test. The results showed physical degradation, morphological and tensile properties enhancement of PVA with NCC’s addition. The addition of NCC to the PVA matrix reduced the degradation rate under UV light significantly. Also, the percentage of weight loss was observed to change with the exposure time to UV light.

Fabrication and characterization of curcumin-loaded nanoparticles using protein from brewers’ spent grain

Using plant-derived proteins as delivery materials to encapsulate lipophilic bioactive compounds is of great interest. Three protein fractions from brewers’ spent grain (BSG) were extracted by the alkaline or alcoholic method with different procedures, and their potential to encapsulate curcumin was evaluated by preparing composite nanoparticles stabilized by lecithin using a pH-cycle method. The three protein fractions showed considerably different encapsulation properties. The particle size and entrapment efficiency varied from 173 to 306 nm and 21.2% to 83.9%, respectively. Compared with the other two fractions, the one extracted with 55% (v/v) ethanol showed better encapsulation performance. Curcumin after encapsulation exhibited an enhanced UV light and thermal stability while its antioxidant activity maintained. These results suggested that BSG protein could be a promising delivery material to encapsulate the water-insoluble bioactive compounds.

Co-assembled photoactive organic molecules into layered double hydroxide as fluorescent fillers for silicone films

In this study, photoactive organic molecules (PAO) and polymer stabilizer (anti-oxidant (AO) and light stabilizer (UV)) are co-intercalated into the galleries of layered double hydroxides (LDH) to form a series of new hybrid luminescent LDH fillers, LDH-AO/PAO and LDH-UV/PAO, adjusting the anion ratio of PAO (%). The structure of the hybrid materials is characterized by X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FT-IR). The optical properties of the hybrid materials and in particular their absolute photoluminescent quantum yields (PL QYab) are underlining that the series LDH-(AO or UV)/PAO is excited with varying degrees of efficiency by blue and/or UV-commercial LEDs. Interestingly, it demonstrates that UV and AO hydroxyl-bearing cyclic molecules used here as spacer to disperse PAO molecules are not deleterious to the luminescence. However, less cyclic AO spacer is here preferred to UV light stabilizer to avoid π-π stacking with PAO dyes. An optimal PAO concentration for each composition is determined for the highest PL QYab. Subsequently, the different samples are dispersed as fillers into silicone to obtain homogeneous luminescent composite films. These results highlight that LDH-(AO or UV)/PAO hybrid materials are suitable candidates to immobilize fluorescent organic dyes and that the associated films are potentially of interest as phosphors materials for several applications.

Improvement of thermal and UV-light stability of β-carotene-loaded nanoemulsions by water-soluble chitosan coating

β-Carotene is a vitamin A precursor and antioxidant with well-known health benefits; however, it is unstable and poorly soluble in water. In this study, β-carotene-loaded nanoemulsions (BC-NEs) and water-soluble chitosan-coated BC-NEs (WSC-BC-NEs) were prepared to improve the stability of β-carotene against high temperature and UV-light. WSC-BC-NEs were round droplets with two distinct layers and an average diameter of 218 nm and zeta potential of +40 mV. The thermal and UV light stability of the WSC-BC-NEs were improved compared to those of both free β-carotene and BC-NEs. Free β-carotene degraded readily during storage, particularly when exposed to high temperature and UV light. By contrast, the WSC-BC-NEs retained 82.0% of β-carotene after 21 days of storage at 37 °C, and 77.6% after 21 days of UV light exposure (253 nm) at room temperature. Furthermore, compared with the BC-NEs, the WSC-BC-NEs improved the thermal stability of β-carotene by about 45.1% after 21 days at 37 °C, and by 28.6% after 21 days of UV light exposure (253 nm). Therefore, the WSC-BC-NEs effectively increased the stability of the encapsulated β-carotene, and show potential for application in the food and beverage industries.

Impact of different crosslinking agents on functional properties of curcumin-loaded gliadin-chitosan composite nanoparticles

The impact of different crosslinking agents (tripolyphosphate, phytic acid and sodium phytate) on functional properties of gliadin-chitosan composite nanoparticles was exploited in this study. The composite nanoparticles were testified as promising encapsulation and delivery system for curcumin. Addition of chitosan could increase the encapsulation efficiency of curcumin in gliadin nanoparticles. In the presence of crosslinking agents, sodium tripolyphosphate modified curcumin-loaded gliadin-chitosan composite nanoparticles, leading to the highest encapsulation efficiency of curcumin. Fluorescence spectroscopy and Fourier transform infrared analyses revealed that sodium tripolyphosphate could interact with the nanoparticles through exposure of more amino acid residues and formation of noncovalent interactions. Correspondingly, curcumin in the composite nanoparticles modified by phytic acid and sodium phytate exhibited better thermal and UV light stability than that in sodium tripolyphosphate modified particles. The composite nanoparticles treated by sodium phytate showed the best neuroprotective effect in neuronal cells with the lowest level of NO production, IL-1β and IL-6. Therefore, sodium phytate had a potential in delivery system for a better protection and release of curcumin in vitro. Furthermore, the application of crosslinking agents was potential in the fabrication of composite nanoparticles to enhance the functional attributes of bioactive compounds.

Construction of Chlorine Labeled ZnO–Chitosan Loaded Cellulose Nanofibrils Film with Quick Antibacterial Performance and Prominent UV Stability

Inside Cover: In article number 2000228, Xuehong Ren, Xinyu Zhang, and co-workers reportsa facile, universal, and cost-effective technique of preparing CNF/ZnO-CS-Cl films, combining vacuum filtration and heat-press processing without the use of any organic solvent. The produced biocompatible CNF/ZnO-CS-Cl hybrids have a quick antibacterial activity, good UV light stability, and favorable physical property, which are applicable for food packaging materials.

Construction of Chlorine Labeled ZnO–Chitosan Loaded Cellulose Nanofibrils Film with Quick Antibacterial Performance and Prominent UV Stability

AbstractIn this study, novel “green” and highly stable biocidal materials composed of cellulose nanofibrils (CNF) and ZnO–chitosan (ZnO–CS) hybrids are constructed by combing vacuum filtration and heat‐press processing without the use of any organic solvent. CNF/ZnO–CS films are soaked in a 10% sodium hypochlorite aqueous solution to endow antibacterial activity. The chlorinated CNF/ZnO–CS samples and chlorinated CNF/ZnO‐CS (CNF/ZnO‐CS‐Cl) possess quick antimicrobial activity against Staphylococcus aureus and Escherichia coli within 30 min of contact compared with CNF and CNF/ZnO–CS controls. The addition of ZnO endows the films with remarkable UV light stability. After exposure to a UV chamber for 24 h, the chlorine loadings on the prepared samples decrease to 0.13%, where 76% of the chlorine loss can be regained after rechlorination. Furthermore, cytotoxicity evaluations reveal the feasibility of the films for in vitro applications. The prepared rechargeable CNF/ZnO–CS–Cl films will have many promising antibacterial applications.

Calcium phosphate coated core-shell protein nanocarriers: Robust stability, controlled release and enhanced anticancer activity for curcumin delivery.

Composite protein and inorganic nanodelivery systems can realise a pH-responsive release and effectively improve the stability and anti-cancer proliferative activity of hydrophobic molecules. In this study, a novel core-shell structure of NaCas (Sodium Caseinate)@CaP (Calcium Phosphate) as a nanodelivery system with NaCas as the core for increasing solubility and CaP as the shell for enhanced stability was built. By using Cur (Curcumin) as a model bioactive molecule, (Cur@NaCas)@CaP nanoparticles (NPs) demonstrated a uniform size distribution of 150-200nm with a distinct nano-composite structure. After exposure to 80°C for 2h, the NaCas@CaP loaded Cur still retained 80% stability while under the same conditions only 12% of free Cur remained intact. UV-light stability was remarkably enhanced 8.56 fold by the protection of the core-shell structure. More importantly, pH-responsive release was achieved owing to the CaP surface coating. The encapsulated Cur by NaCas@CaP NPs exhibited an enhanced cellular anti-oxidant activity (CAA) based on MGC-803 cell monolayer models. The confocal laser-scanning microscopy (CLSM) images and cancer-cell-proliferation assay illustrated that (Cur@NaCas)@CaP NPs showed significantly improvements of cellular uptake and anti-cancer activity against A549 cancer cells than free Cur. These novels core-shell NaCas@CaP NPs are very promising for intensifying the stability and bioactivity of hydrophobic compounds in drug delivery and cancer treatment.

Preparation and characterisation of acrylic resin for electro-deposited mono-coat coatings

ABSTRACT Acrylic resins are known for their multifarious characteristics. Diversified properties of acrylic resins have been utilised for the development of acrylic cationic electrodeposition multicolour mono-coat corrosion protective coatings by acrylic graft polymer of methyl acrylate, butyl acrylate, styrene, and methyl methacrylate in the presence of hydroxy propyl acrylate at 113–117°C in the presence of AIBN (Azo-bis iso-butyronitrile) as the initiator. The concept was to develop acrylic graft polymer wherein chemical bonds are protected against UV radiation 400 h or 18-month outdoor exposure. Developed acrylic resin has special characteristic e.g. excellent metal protection against corrosion 500 h salt spray test as per ASTM B117, excellent durability, economical primer, and finish coat in single application and meeting the International and National legislation. Resulting polymers were characterised by using FTIR spectroscopy, particle size analyser and other Morden instrumental techniques. Thus the obtained polymers have high solid content (72 ± 1%) and can be used in electrodeposition emulsion paint as a binder. The coatings are mono-coat prepared and their anticorrosion behaviour is discussed in this paper. The experimental results depict that the resin thus synthesised has high anticorrosive property, UV light stability, and excellent weather resistance.

Influence of Charge Transport Layers on Capacitance Measured in Halide Perovskite Solar Cells

Summary Capacitance-based techniques have been used to measure the electrical properties of halide perovskite solar cells (PSCs) such as defect activation energy and density, carrier concentration, and dielectric constant, which provide key information for evaluating the device performance. Here, we show that capacitance-based techniques cannot be used to reliably analyze the properties of defects in the perovskite layer or at its interface, because the high-frequency capacitance signature is due to the response of charge carriers in the hole-transport layer (HTL). For HTL-free PSCs, high-frequency capacitance can be considered as the geometric capacitance for analyzing the dielectric constant of the perovskite layer because there is no trapping and de-trapping of charge carriers in the perovskite layer. We further find that the low-frequency capacitance signature can be used to calculate the activation energy of the ionic conductivity of the perovskite layer, but the overlapping effects with charge transport materials must be avoided.

α-Lactalbumin and chitosan core-shell nanoparticles: resveratrol loading, protection, and antioxidant activity.

Resveratrol (RES)-loaded protein-polysaccharide nanoparticles were fabricated through simple electrostatic interactions with oppositely charged α-lactalbumin (ALA) and chitosan (CHI) with a mass ratio of 5 : 1 without the addition of NaCl at pH 6.5. The Z-average diameter and zeta-potential values of RES-ALA-CHI nanoparticles were 211.0 nm and 13.23 mV, respectively. Both TEM and AFM graphs confirmed that RES-ALA-CHI nanoparticles had a spherical shape, and were dispersed homogeneously at the nanoscale. The encapsulation efficiency (EE) and loading amount (LA) of RES in RES-ALA-CHI nanoparticles were 58.86% and 196.2 μg mg-1, respectively, in the presence of 400 μg mL-1 RES. XRD results confirmed that RES was in amorphous form in ALA-CHI nanoparticles. The interaction between RES and ALA-CHI nanoparticles was mainly driven by hydrophobic interaction and hydrogen bonding. Compared to RES (free), the UV light and heat stability, in vitro bioaccessibility, and antioxidant activity of RES in RES-ALA-CHI nanoparticles were pronouncedly enhanced. The information provided in this study should be of interest to the food industry to fabricate robust nanoscale delivery systems with ALA-CHI nanoparticles for RES and other hydrophobic bioactive compounds.