Absorption Of Ultraviolet Radiation Research Articles

UV Irradiation and Near Infrared Characterization of Laboratory Mars Soil Analog Samples

The search for molecular biosignatures at the surface of Mars is complicated by an intense irradiation in the mid- and near- ultraviolet (UV) spectral range for several reasons: (i) many astrobiologically relevant molecules are electronically excited by efficient absorption of UV radiation and rapidly undergo photochemical reactions; (ii) even though the penetration depth of UV radiation is limited, aeolian erosion continually exposes fresh material to radiation; and (iii) UV irradiation generates strong oxidants such as perchlorates that can penetrate deep into soils and cause subsurface oxidative degradation of organics. As a consequence, it is crucial to investigate the effects of UV radiation on organic molecules embedded in mineral matrices mimicking the martian soil, in order to validate hypotheses about the nature of the organic compounds detected so far at the surface of Mars by the NASA Mars Science Laboratory’s Curiosity rover, as well as organics that will be possibly found by the next rover missions Mars 2020 (NASA) and ExoMars 2022 (ESA-Roscosmos). In addition, studying the alteration of possible molecular biosignatures in the martian environment will help to redefine the molecular targets for life detection missions and devise suitable detection methods. Here we report the results of mid- and near-UV irradiation experiments of Mars soil analog samples obtained adsorbing relevant organic molecules on a clay mineral that is quite common on Mars, i.e. montmorillonite, doped with 1 wt% of magnesium perchlorate. Specifically, we chose to investigate the photostability of a plausible precursor of the chlorohydrocarbons detected on Mars by the Curiosity rover, namely phthalic acid, along with the biomarkers of extant life L-phenylalanine and L-glutamic acid, which are proteomic amino acids, and adenosine 5’-monophosphate, which is a nucleic acid component. We monitored the degradation of these molecules adsorbed on montmorillonite through in situ spectroscopic analysis, investigating the reflectance properties of the samples in the Near InfraRed spectral region. Such spectroscopic characterization of molecular alteration products provides support for two upcoming robotic missions to Mars that will employ NIR spectroscopy to look for molecular biosignatures, through the instruments SuperCam on board Mars 2020, ISEM, Ma_Miss and MicrOmega on board ExoMars 2022.

Fiber fines for fabricating lignocellulose films and the effect of lignin

Excess lignocellulose fines in some fiber processing mills cause issues and hurt product quality. To use this type of biomaterial as a resource, surplus fines can be separated and dissolved with solvents for further transformation. Therefore, 1-butyl 3-methyl imidazolium chloride ionic liquid (IL) was used as a powerful green solvent for a rapid dissolution process. However, a low degree of polymerization (DP) of the cellulose in fines and the effects of lignin content and its structure on the process and film properties are controversial subjects. This study demonstrated that the three dimensional structure of lignin did not permit the raw bagasse fines (prior to pulping) to dissolve in the IL even after several hours. However, following decomposition of the lignin structure by pulping, the fiber fines were readily dissolved. Further, all the fabricated films from the fiber fines exhibited satisfactory strength properties, despite the fact that the cellulose had a low DP. The films from bleached fiber fines showed higher tensile strength than those containing lignin, although the cellulose chain was longer and had a higher DP for the latter. Lignin resulted in reduced transparency, and higher absorption of ultraviolet radiations, but it did not affect the surface roughness of the films.

Effects of titanium dioxide nanoparticles and sheep manure biochar on the behavior of methylene blue organic contaminant in sandy loam and loam soils

The present study aimed to evaluate the effects of titanium dioxide nanoparticles (T: 1 and 3%), sheep manure biochar (B: 1 and 3%), and their combination (T0.5% + B0.5% and T1.5% + B1.5%) on the degradation/sorption of methylene blue (MB: 100, 200, and 300 mg/kg soil) in sandy loam (SL) and loam (L) soils with variable light radiation (ultraviolet(UV) and visible(VS)). According to the results, the application of T (especially with UV radiation exposure), B, and their combination significantly reduced the MB concentration in the soils compared to the control treatment (without T and B). In addition, the combined application of T and B (T1.5% + B1.5%) was significantly more efficient than the other treatments in the reduction of the MB extraction in the studied soils. However, B and T application decreased the soil MB concentration, but due to the competition between the ions in the soils and MB for adsorption on the B and T surfaces, insufficient water in the soils to form appropriate amounts of degradable hydroxyl radicals, low absorption of UV radiation by T (due to the high thickness of the soil layer), and consumption of large amounts of T for soil organic matter degradation, the efficacy of these amendments decreased. Moreover, lack of using specialized biochar for this cationic contaminant (modification of the B functional groups) diminished the efficiency of this adsorbent in the soil, which requires further investigations.

Insight into Antioxidant and Photoprotective Properties of Natural Compounds from Marine Fungus.

This computational and experimental work aims to elucidate physicochemical and photophysical natures of free radical scavenging and ultraviolet radiation (UVR) filtering activities of five terpenoids available in the extract of marine fungus. The antioxidant activities of ochraceopone F (C1), aspertetranone D (C2), cycloechinulin (C3), wasabidienone E (C4), and mactanamide (C5) are evaluated by using density functional theory (DFT) at the M05-2X/6-311++G(d,p) level of theory in the gas phase, water, and pentyl ethanoate (PEA). Double antioxidant mechanisms allowing the second (H+/e-) donation such as double hydrogen atom transfer (dHAT), double single electron transfer-proton transfer (dSET-PT), and double sequential proton loss-electron transfer (dSPL-ET) are considered. Reaction enthalpies (ΔrH0), standard Gibbs free energies (ΔrG0) and potential energy surfaces of reactions toward HOO• radical are then established to evaluate the hydrogen transfer (HT) and radical adduct formation (RAF) mechanisms. The computational results are supported by DPPH• and ABTS•+ antioxidant essays. Results show that all compounds C1-C5 are able to scavenge two free radicals via dHAT, dSET-PT, and dSPL-ET mechanisms. Among the compounds, C3 and C4 represent the most potential antioxidants, especially via HAT and RAF mechanisms in all the reaction media. Their rate constants for both HAT and RAF reactions are remarkably higher than that of Trolox and ascorbic acid. The kinetic calculations on activation Gibbs free energies (ΔG⧧) and rate constants (kTST) based on conventional transition state theory (TST) reveal that HAT and RAF processes are in competition in solvents. Photophysical processes occurring during UVR exposure are investigated using the time dependent density functional theory (TD-DFT) combined with UV-vis experiments. The obtained results highlight the promising activities of C1-C5 in UVR absorption in the ranges of UVA and UVB. Among them, C3 and C4 also show better UV absorption properties with the easiest excitations (band gaps equal to 4.06 and 3.65 eV). This study suggests the natural candidates possibly used in organic sunscreen.

Antioxidants and cactus extract enhances the sun protection factor of octocrylene and oxybenzone solution

Ultraviolet (UV) filters such as octocrylene and oxybenzone in topical photoprotection products work effectively in absorbing UV radiation, thus minimizing sun damage to the skin. Antioxidants are incorporated into sunscreen products to enhance the photoprotection ability of the products. However, the effectiveness of the antioxidants on the sun protection factor (SPF) of UV filters is not well established. Hence in this study, the effect of caffeine, nicotinamide, β-carotene, α-tocopherol, and cactus extract on the SPF of octocrylene and oxybenzone were investigated. The UV absorbance of octocrylene (5 µg/mL) and oxybenzone (20 µg/mL) in 95% ethanol, with different concentrations of the antioxidants (0.1–100 µg/mL) and cactus extract were measured from 290-320nm. The UV absorbance values were converted to SPF values by the Mansur equation. Statistical analysis was performed by ANOVA test and Post Hoc test (Dundett T3 test) with a significance level of p<0.05 using SPSS software. The antioxidants and cactus extract were found to significantly increase the SPF of octocrylene and oxybenzone solutions in a concentration-dependent manner. Out of the antioxidants tested, β-carotene and α-tocopherol were the most effective antioxidants to increase the SPF of octocrylene solution and oxybenzone solutions, respectively. The results supported that it is beneficial to incorporate antioxidants and cactus extract into the formulation of topical photoprotection products.

Nanocomposites of polyethylene and ternary (Mg + Zn/Al) layered double hydroxide modified with an organic UV absorber

In this research work, ternary (Mg + Zn:Al; M2+:M3+ = 2:1) layered double hydroxides (LDH) intercalated with nitrate and p-aminobenzoate anions were synthesized through the co­precipitation method at constant alkaline pH. These materials were characterized by several instrumental techniques and used as functional fillers in low-density polyethylene (LDPE), obtaining homogeneous nanocomposites by means of injection molding. In the samples prepared with percentages of 0.5, 2, 4, 6 and 10% by weight in relation to LDPE, maintenance or slight improvement of the mechanical properties was observed for all samples. In the LDPE nanocomposites the UV absorption showed to be higher than neat polyethylene. Weathering experiments performed with the neat LDPE and LDPE nanocomposites containing 5% of maleic anhydride and 5% of LDH intercalated with p­aminobenzoate demonstrated a decrease of oxidation product generated due to ultraviolet radiation absorption because the organic intercalated specie, indicating that the ternary LDH is a potential filler to protect polymers from UV radiation degradation.

Antioxidative, Anti-Inflammatory, and Anti-Aging Properties of Mycosporine-Like Amino Acids: Molecular and Cellular Mechanisms in the Protection of Skin-Aging.

Prolonged exposure to ultraviolet (UV) radiation causes photoaging of the skin and induces a number of disorders, including sunburn, fine and coarse wrinkles, and skin cancer risk. Therefore, the application of sunscreen has gained much attention to reduce the harmful effects of UV irradiation on our skin. Recently, there has been a growing demand for the replacement of chemical sunscreens with natural UV-absorbing compounds. Mycosporine-like amino acids (MAAs), promising alternative natural UV-absorbing compounds, are a group of widely distributed, low molecular-weight, water-soluble molecules that can absorb UV radiation and disperse the absorbed energy as heat, without generating reactive oxygen species (ROS). More than 30 MAAs have been characterized, from a variety of organisms. In addition to their UV-absorbing properties, there is substantial evidence that MAAs have the potential to protect against skin aging, including antioxidative activity, anti-inflammatory activity, inhibition of protein-glycation, and inhibition of collagenase activity. This review will provide an overview of MAAs, as potential anti-aging ingredients, beginning with their structure, before moving on to discuss the most recent experimental observations, including the molecular and cellular mechanisms through which MAAs might protect the skin. In particular, we focus on the potential anti-aging activity of mycosporine-2-glycine (M2G).

Development and Validation of UV-Visible Spectrophotometric Method for the Determination of 5-Hydroxymethyl Furfural Content in Canned Malt Drinks and Fruit Juices in Ghana

A simple, rapid, accurate, and less expensive spectrophotometric method has been developed for the quantitation of 5-hydroxymethyl furfural (5-HMF) levels in canned malt drinks and fruit juice drinks sampled in the Kumasi Metropolis, Ghana. The quantitation is based on the selective maximum absorption of ultraviolet radiation by 5-HMF at the wavelength (λmax) of 284 nm using acetonitrile : water (50 : 50 v/v) as the solvent system. The method was established to be specific, precise, and accurate over a concentration range of 0.001 mg/ml–0.02 mg/ml. 5-HMF levels in fruit juice samples (A1–A10) were between 0.132 mg/ml and 0.438 mg/ml, and these levels were shown to be comparable (t = 2.200;p=0.0553) to the contents in the canned malt samples (M1–M10) which were between 0.3140 mg/ml and 0.7170 mg/ml. The study failed to show any dependence of 5-HMF levels on the composition of the product as well as the manufacturing process adopted. The length of storage did also not significantly affect the 5-HMF levels in the products.

Multifunctional acrylic fibers prepared via in-situ formed silver nanoparticles: Physicochemical, UV radiation protection, and antistatic properties

A single treatment that makes textiles multifunctional is very attractive to the textile chemical processors. In this study, multifunctional acrylic fibers were produced by in situ forming silver (Ag) nanoparticles at various concentrations of Ag and trisodium citrate (TSC). The exhaustion of silver into acrylic fibers and the reduction of Ag to Ag nanoparticles were carried out at 90 °C, well above the glass transition temperature (Tg) of this fiber in water. The effect of the concentration of Ag, Ag to TSC ratio, pH, and reaction time on the color strength, ultraviolet (UV) radiation absorption, surface electrical resistance and mechanical properties of the treated fibers were systematically investigated. It was found that if the concentration of Ag was less than 1% on the weight of acrylic fibers or the Ag to TSC ratio was less than 1:2, no color was produced. The color strength and UV radiation absorption capacity of the treated acrylic fibers increased with an increase in the concentration of Ag, and Ag to TSC ratio, and also with a decrease in the pH. On the other hand, the surface resistance of the treated acrylic fibers decreased with an increase in the concentration of Ag and a decrease in the treatment pH. The treated fibers showed excellent antibacterial activity, UV radiation absorption capacity, and also very good antistatic properties along with an excellent colorfastness to washing. Moreover, the developed treatment is highly durable to washing as after 20 washes the treated fibers lost their antibacterial activity only marginally.

Recent Advances of ZnO Based Nanowires and Nanorods Devices

This paper presents the recent advances of the Zinc Oxide (ZnO) based nanowires and nanorods devices. ZnO has gained a substantial interest in the research area of the wide bandgap semiconductors due to its unique electrical, optical and structural properties. ZnO is considered as one of the major candidates for electronic and photonic applications. Also, it has distinguished and interesting electrical and optical properties. ZnO is considered as a potential contender in optoelectronic applications such as solar cells (SCs), surface acoustic wave devices, and ultraviolet (UV) emitters. The ZnO as a nanostructured material exhibits many advantages for nanodevices. ZnO nanostructured material has the ability to absorb UV radiation and immense in many optical applications. Recently, ZnO nanostructured based devices have gained much attention due to their various potential applications. ZnO as nanomaterial has been used in many devices such as UV photodetectors (PDs), light emitting diodes (LEDs), and transistors. The recent aspects of ZnO nanowires and nanorods based devices are presented and discussed.

Poly(vinyl Chloride) Photostabilization in the Presence of Schiff Bases Containing a Thiadiazole Moiety.

Five Schiff bases containing a thiadiazole moiety have been used as poly(vinyl chloride) photostabilizers at low concentrations. The efficiency of Schiff bases as photostabilizers was investigated using various techniques, for example, the changes in poly(vinyl chloride) infrared spectra, molecular weight, chain scission quantum yield, and surface morphology were monitored upon irradiation with an ultraviolet light. Evidently, all the additives used inhibited poly(vinyl chloride) photodegradation at a significant level. The most efficient Schiff base exhibited a high level of aromaticity and contained a hydroxyl group. It seems possible that such photostabilization could be due to the direct absorption of ultraviolet radiation by the additives. In addition, Schiff bases could act as radical scavengers and proton transfer facilitators to stabilize the polymeric materials.

Ultraviolet Absorbing Efficacy and Photostability of Feruloylated Soybean Oil

AbstractFeruloylated soy glycerides (FSG) are a natural‐based, ultraviolet (UV) absorbing, antioxidant vegetable oil synthesized from the lipase‐catalyzed transesterification of ethyl ferulate and soybean oil. Commercial broad spectrum UV absorbing formulations contain multiple UV absorbing compounds that absorb UV radiation in specific regions. The most commonly used compounds are avobenzone (AVO, λmax 356 nm) and octinoxate (ONX, λmax 310 nm), which absorb primarily ultraviolet A and ultraviolet B radiation, respectively. The FSG chromophore is chemically similar to ONX but has a λmax of 328 nm, approximately the median λmax of AVO and ONX. Equimolar mixtures of AVO–ONX and AVO–FSG, 50 μM:50 μM, solutions in ethanol were compared to determine whether FSG was fungible for ONX in total absorbance capacity, photostability when exposed to UV radiation, and broad spectrum absorbance coverage before and after exposure to UV radiation. While it was determined that AVO–FSG mixtures possessed statistically indistinguishable total absorbance capacity compared to AVO–ONX solutions, AVO–FSG possessed slightly better photostability after 4 hours of UV exposure based on 95% confidence interval comparisons from weighted regression equations. Substituting FSG for half of the ONX (e.g., 50 μM:25 μM:25 μM AVO–ONX–FSG) resulted in the best mixture with total absorbance capacity and photostability statistically equal to the AVO–ONX mixtures but with statistically superior broad spectrum UV absorbance compared to AVO–ONX and AVO–FSG mixtures. The natural, vegetable oil‐based FSG can be substituted on an equimolar bases for ONX in mixtures with AVO to produce formulations with similar to superior efficacy.

From fundamental science to product: a bottom-up approach to sunscreen development.

Despite the pivotal role of ultraviolet (UV) radiation in sustaining life on Earth, overexposure to this type of radiation can have catastrophic effects, such as skin cancer. Sunscreens, the most common form of artificial protection against such harmful effects, absorb UV radiation before it reaches vulnerable skin cells. Absorption of UV radiation prompts ultrafast molecular events in sunscreen molecules which, ideally, would allow for fast and safe dissipation of the excess energy. However, our knowledge of these mechanisms remains limited. In this article, we will review recent advances in the field of ultrafast photodynamics (light induced molecular processes occurring within femtoseconds, fs, 10-15 s to picoseconds, ps, 10-12 s) of sunscreens. We follow a bottom-up approach to common sunscreen active ingredients, analysing any emerging trends from the current literature on the subject. Moreover, we will identify the main questions that remain unanswered, pinpoint some of the main challenges and finally comment on the outlook of this exciting field of research.

Vitamin E inhibits the UVAI induction of \u201clight\u201d and \u201cdark\u201d cyclobutane pyrimidine dimers, and oxidatively generated DNA damage, in keratinocytes

Solar ultraviolet radiation (UVR)-induced DNA damage has acute, and long-term adverse effects in the skin. This damage arises directly by absorption of UVR, and indirectly via photosensitization reactions. The aim of the present study was to assess the effects of vitamin E on UVAI-induced DNA damage in keratinocytes in vitro. Incubation with vitamin E before UVAI exposure decreased the formation of oxidized purines (with a decrease in intracellular oxidizing species), and cyclobutane pyrimidine dimers (CPD). A possible sunscreening effect was excluded when similar results were obtained following vitamin E addition after UVAI exposure. Our data showed that DNA damage by UVA-induced photosensitization reactions can be inhibited by the introduction of vitamin E either pre- or post-irradiation, for both oxidized purines and CPD (including so-called “dark” CPDs). These data validate the evidence that some CPD are induced by UVAI initially via photosensitization, and some via chemoexcitation, and support the evidence that vitamin E can intervene in this pathway to prevent CPD formation in keratinocytes. We propose the inclusion of similar agents into topical sunscreens and aftersun preparations which, for the latter in particular, represents a means to mitigate on-going DNA damage formation, even after sun exposure has ended.

Climate change-induced increases in precipitation are reducing the potential for solar ultraviolet radiation to inactivate pathogens in surface waters

Climate change is accelerating the release of dissolved organic matter (DOM) to inland and coastal waters through increases in precipitation, thawing of permafrost, and changes in vegetation. Our modeling approach suggests that the selective absorption of ultraviolet radiation (UV) by DOM decreases the valuable ecosystem service wherein sunlight inactivates waterborne pathogens. Here we highlight the sensitivity of waterborne pathogens of humans and wildlife to solar UV, and use the DNA action spectrum to model how differences in water transparency and incident sunlight alter the ability of UV to inactivate waterborne pathogens. A case study demonstrates how heavy precipitation events can reduce the solar inactivation potential in Lake Michigan, which provides drinking water to over 10 million people. These data suggest that widespread increases in DOM and consequent browning of surface waters reduce the potential for solar UV inactivation of pathogens, and increase exposure to infectious diseases in humans and wildlife.

Excited-State Dynamics in O6-Methylguanosine: Impact of O6-Methylation on the Relaxation Mechanism of Guanine Monomers

Absorption of ultraviolet radiation by DNA bases results in ultrafast internal conversion to the ground state, which minimizes photodamage. However, exogenous and endogenous alkylating agents present in the cellular environment can methylate the nucleobases in DNA. In particular, methylation of guanosine at the O6 position in DNA leads to the formation of the O6-methylguanosine adduct, which may alter the photostability of DNA. This contribution demonstrates that O6-methylation of guanosine red shifts its ground-state absorption spectrum and slows down the rate of internal conversion to the ground state by ∼40-fold in aqueous solution. The 40-fold decrease in the rate of excited-state decay increases the probability of photodamage within cellular DNA. It is proposed that the longer decay lifetime corresponds to relaxation of the excited-state population in O6-methylguanosine along a C6-puckered reaction coordinate in the 1ππ*(La) potential energy surface that runs parallel to an ultrafast internal conversion pathway along a C2-puckered coordinate.

Phytochemical characterization of fruit extracts of Rubus adenotrichus and evaluation of their antioxidant power for dermocosmetics formulation

There are more than 700 species of the genus Rubus, popularly known as Mora (tropical highland blackberry). In Costa Rica, the species Rubus adenotrichus has been characterized by its high content of antioxidant substances, becoming one of the most cultivated species and that may have characteristics to be used in cosmetics or medicine. The objective of the present study is to identify the main phytochemical groups and to quantify the main markers in order to associate them with cosmetic or medicinal functions in pharmaceutical products. Ripe fruits of R. adenotrichius were fractionated with solvents of low, medium and high polarity, followed by a phytochemical screening according to the World Health Organization Guidelines for the Control of Quality of Products of Natural Origin. The antioxidant properties were evaluated by means of the H-ORAC and DPPH test; the concentration of total phenols by Folin-Ciocalteau and antocinanins by differential pH was determined. Finally, the physicochemical properties of the aqueous extract, such as pH, specific gravity, Brix grades, conductivity, and osmolarity was determined and an absorption spectrum from 260 to 700 nm was obtained. Phenolic compounds were found as condensed and non-condensed tannins, anthocyanins, flavonoids, terpenes, and alkaloids as major phytochemical groups, a high antioxidant power measured in H-ORAC 311 ±7.63 μg/mol Trolox Equivalent/g of dry fruit, and EC 50 118.46 mg/L for the aqueous extract. The total phenols found was 20.85 ± 0.27 mg/g of dry sample of gallic acid equivalents which makes the R. adenotrichus fruit an excellent component for bacteriostatic, anti-aging, anti-wrinkle, nourishing and moisturizing formulations, and the astringent effect also allows its application to small superficial wounds on the skin. Likewise, the acidic pH of 3.55 ± 0.1 is beneficial for maintaining the cutaneous acid mantle thereby favoring the normal flora of the skin, but may be a problem for the formulation of carbomer-based gels or the incorporation of preservatives. The aqueous extract is hyperosmotic (559.66 ± 3.21 mOs/kg) and has a high electrical conductivity (285 ± 2 μS/cm) due to the presence of electrolytes and a considerable amount of sugars, according to Brix degrees (7.543° ± 0.005°). Finally, the 4% w/w aqueous extract shows an absorption of ultraviolet radiation of 25% in the wavelengths from 260 to 400 nm, by which it also could be useful for formulating compositions for sun protection.

CuAlS 2 thin films – Dip coating deposition and characterization

Abstract CuAlS 2 thin films were deposited by a dip coating technique at room temperature. The X-ray energy dispersive (EDAX) and X-ray diffraction (XRD) analysis showed that the deposited CuAlS 2 thin film is nearly stoichiometric and possesses a tetragonal unit cell structure. The crystallite sizes determined from the XRD data employing Scherrer's formula and modified forms of Hall–Williamson relation like the uniform deformation model (UDM), uniform stress deformation model (USDM), uniform deformation energy density model (UDEDM), and the size–strain plot method (SSP) were in good agreement with each other. The transmission electron microscopy (TEM) and scanning electron microscopy (SEM) studies of the thin film revealed that the deposited film is uniform without any cracks and the film covers the whole of the substrates. The atomic force microscopy (AFM) of the as-synthesized thin film surfaces showed spherical grains having coalescences between them. The optical absorbance spectrum analysis showed that the thin films possess both direct and indirect band gaps. The semiconducting and p -type nature of the thin films was confirmed from dc – electrical resistivity versus temperature, room temperature Hall effect, and Seebeck coefficient versus temperature measurements. The effect of the different illuminations on the CuAlS 2 thin film showed that it can be used as a material for absorption of ultra-violet radiation. All the obtained characterization results are deliberated in detail.

Anchoring CeO2 nanoparticles on monodispersed SiO2 spheres to construct hydrophobic polymer coating with enhanced UV absorption ability

Tremendous effort has been devoted to develop CeO2/polymer nanocomposites due to their excellent ultraviolet radiation absorption properties. However, there still exists many challenges in the successful incorporation of CeO2 nanoparticles into the polymer matrix because the ease aggregation of CeO2 nanoparticles. Here, we addressed the above issue by anchoring CeO2 nanoparticles on functionalized SiO2 spheres before their introduction into polymeric matrix, in which monodispersed vinyl group coated SiO2 spheres were synthesized by co-condensing tetraethoxysilane and 3-methacryloxypropyltrimethoxysilane, followed by coating with small size CeO2 nanoparticles (CeO2@M-SiO2) through chemical precipitation. The polymer composite film prepared by importing CeO2@M-SiO2 into fluorinated polyacrylate through miniemulsion polymerization exhibited enhanced UV absorption capacity, accompanied with an obvious improvement in hydrophobicity due to the increase in the surface roughness and fluorine content. Furthermore, the formation mechanism of the nanocomposite film was proposed: a polymer layer would form around the nanoparticles after film formation. This fluorinated polyacrylate/CeO2@M-SiO2 composite film is anticipated to be practically applied as outdoor coatings.

Engineered PMMA-ZnO nanocomposites for improving the electric arc interruption capability in electrical switching applications: Unprecedented experimental insights

Polymer inorganic nanocomposites (PINCs) have been engineered for controlling the electrical arc and to improve the arc interruption capability of the electrical switching applications, like circuit breakers. Several PINCs are fabricated by formation of ZnO quantum dots (QDs) in a poly (methyl methacrylate) (PMMA) matrix via in-situ polymerization method to avoid agglomeration of QDs, leading to a good spatial distribution of QDs in the polymer matrix. These PINCs have been characterized in detail for the morphology of QDs, interaction between QDs and polymer matrix, and ultraviolet (UV) radiation absorption. ZnO QDs have been assessed to have particle diameter of 3.5 nm, and their presence in the PMMA is revealed by the unique luminescence characteristics of the QDs under UV light. The presence of ZnO QDs broadened the range of UV radiation absorption of PMMA and the absorption edge is gradually shifted from 270 nm to 338 nm with step-wise loading of ZnO QDs. The PINCs are tested to determine their reproducibility and impact on the electrical arcs of current 1.6 kA generated using a specially designed test-setup. Interaction of PINCs with the electrical arcs generates ablation of chemical species towards core of the electrical arc, resulting in increase of voltage leading to cool-down the arc temperature. This experimental study demonstrates for the first time that these PINCs are reproducible, reliable and provides superior arc interruption capability.