Ultraviolet Screening Research Articles

PVC-Based Ultraviolet Screening Films Modified by Chitosan Capped ZnO–Hydroxyapatite

PVC-Based Ultraviolet Screening Films Modified by Chitosan Capped ZnO–Hydroxyapatite

Fabrication of CeO2/CaO nanocomposite as ultraviolet screening agent and its application in sunscreen

In order to improve CeO2 ultraviolet absorption performance and transparency, this paper puts forward that different proportions of calcium oxide are doped during the formation of CeO2. Doping calcium ions with larger ion size and lower valence leads to the formation of oxygen defects by inhibiting the precipitation of oxygen from cerium oxide and keeps the fluorite structure of cerium oxide stable. The effects of CaO doping on the crystal structure, morphology, and optical characteristics of CeO2 were analyzed by XRD, SEM, TEM, TGA, XPS, UV–vis spectrophotometry. The pH of sunscreen, spread ability and some physical as well as chemical evaluations were carried out, while to study its UV protection performance the sunscreen SPF test was performed. The UV–vis results revealed that CeO2/20%CaO showed highly efficient UV absorption capacity. After adding calcium oxide, the catalytic activity of the material is reduced, due to which the generation of free radicals is demoted, and the harm to human body is decreased. After the addition of 3 wt% nanomaterials into sunscreen, the sun protection factor（SPF ）values of pure cerium oxide and CeO2/20%CaO are 1.95 and 2.81, and their sun protection coefficient is increased by 69.39%. Therefore, it is an ideal candidate as a component of ultraviolet screening agent in sunscreens and provides a new idea for the research direction of cerium oxide in anti-ultraviolet applications.

Screening of Ultraviolet-Induced Thermotolerant Yeast Mutants and Their Performance

The simultaneous saccharification and fermentation (SSF) technique holds promise for the conversion of lignocellulose to ethanol. However, the optimal fermentation temperature of yeast is lower than the enzymatic hydrolysis temperature of the saccharification process, which leads to the temperature of the actual production process of SSF usually being lower than 38 °C. In this work, two ultraviolet (UV)-induced mutations were performed step by step using Saccharomyces cerevisiae BY4742 as the original strain to enable the yeast to perform well at higher temperatures. Thermotolerant strains obtained through mutagenesis and screening, YUV1-1 and YUV2-2, were utilized for fermentation and SSF at a targeted temperature of 40 °C. They obtained ethanol yields comparable to those at 38 °C in SSF, whereas the ethanol yields of the original strain at 40 °C decreased by about 10% compared to those at 38 °C. This study proves that thermotolerant strains adapted to elevated fermentation and SSF temperatures can be obtained through UV mutagenesis and screening, thereby increasing the stability of the fermentation and SSF processes and lowering the subsequent distillation costs.

Solid SiO2-Sealed Mesoporous Silica for Synergistically Combined Use of Inorganic and Organic Filters to Achieve Safe and Effective Skin Protection from All-Band UV Radiation.

To effectively shield the full band of ultraviolet (UV) radiation and provide desirable protection, the combination of inorganic and organic filters was often used to protect human skin from the serious harm of UV exposure. However, the incompatibility of different filters and their mutual negative effect limit the production of multifilter sunscreen. In addition, the hazard of reactive oxygen species (ROS) produced by inorganic filters after UV exposure and the skin permeability of organic filters remain unresolved problems. In this study, titanium dioxide (TiO2) and diethylamino hydroxybenzoyl hexyl benzoate (DHHB), two kinds of common filters with complementary UV shielding range, were first encapsulated into large mesoporous silica nanoparticles (MSN, ∼300 nm) to obtain MSN-TiO2 and MSN-DHHB. Also, a SiO2 coating was then made to seal and stabilize the MSN-TiO2 and MSN-DHHB. The structure, UV screen function, and safety of the SiO2-coated filters, MSN-TiO2@SiO2 and MSN-DHHB@SiO2, were evaluated. The good mechanical stability exhibited by the solid SiO2 layer prevented the release and skin penetration of the sealed DHHB and the photocatalysis of TiO2. Furthermore, the combination of MSN-TiO2@SiO2 and MSN-DHHB@SiO2 in sunscreen cream showed excellent UV shielding performance on covering the whole UV radiation range without mutual interference. Therefore, coating SiO2 over MSN is a feasible strategy for entrapping various filters to improve their photostability, preventing skin penetration and ROS generation, and enhancing their compatibility with different sunscreen formulations.

Mimicking orchids lure bees from afar with exaggerated ultraviolet signals.

Flowers have many traits to appeal to pollinators, including ultraviolet (UV) absorbing markings, which are well-known for attracting bees at close proximity (e.g., <1m). While striking UV signals have been thought to attract pollinators also from far away, if these signals impact the plant pollinia removal over distance remains unknown. Here, we report the case of the Australian orchid Diuris brumalis, a nonrewarding species, pollinated by bees via mimicry of the rewarding pea plant Daviesia decurrens. When distant from the pea plant, Diuris was hypothesized to enhance pollinator attraction by exaggeratedly mimicking the floral ultraviolet (UV) reflecting patterns of its model. By experimentally modulating floral UV reflectance with a UV screening solution, we quantified the orchid pollinia removal at a variable distance from the model pea plants. We demonstrate that the deceptive orchid Diuris attracts bee pollinators by emphasizing the visual stimuli, which mimic the floral UV signaling of the rewarding model Daviesia. Moreover, the exaggerated UV reflectance of Diuris flowers impacted pollinators' visitation at an optimal distance from Da.decurrens, and the effect decreased when orchids were too close or too far away from the model. Our findings support the hypothesis that salient UV flower signaling plays a functional role in visual floral mimicry, likely exploiting perceptual gaps in bee neural coding, and mediates the plant pollinia removal at much greater spatial scales than previously expected. The ruse works most effectively at an optimal distance of several meters revealing the importance of salient visual stimuli when mimicry is imperfect.

Carbon black production from various sources by thermal cracking method

Petroleum-based feedstock (PBFS) and Coal tar-based feedstock (CTBFS) were used for the synthesis of carbon black (CB) via thermal cracking method named as Petroleum-based feedstock carbon black (PBFS-CB) and Coal tar-based feedstock carbon black (CTBFS-CB) in a furnace reactor at a temperature of 1800 °C, for utilizing industrial waste products. The obtained distinguish carbon black samples are characterized for determining functional groups, morphology, and surface area using advanced instruments. Further, investigated physical and mechanical properties of obtained different CB samples mixed into the natural rubber. The small clusters morphology is observed in CBs. There are slight changes in spectra peaks and there no significant new peaks are observed. The same minerals observed at same theta values in XRD pattern corresponding to PBFS-CB and CTBFS-CB. The tensile strength, modulus 300% and abrasion loss of samples into rubber were determined as per international ASTM standards. The results revealed that, there are negotiable values observed in both samples due to minimal changes observed in surface area of the CB samples. These samples can be used for various applications viz rubber reinforcement, conductivity agent, colouring agent, and ultraviolet screening agent etc.

UV light blocking and conversion by porous europium-doped titanium dioxide (TiO2-Eu) thin films for potential protection of photovoltaic devices

In recent years, transparent thin films capable of screening and converting ultraviolet (UV) photons into visible spectrum gained significant interest in the protection of photovoltaic devices. We investigated the optical properties and UV screening capability of europium-doped titanium oxide (TiO2−Eu) thin films deposited by the spin-coating method from a solution precursor for the first time in this study. We showed that TiO2-Eu thin films demonstrate europium concentration-dependent optical properties, and the quantum yield of the optimized sample was found to be ∼10.2%. Transmittance and photoluminescence measurements suggested that TiO2−Eu thin film can effectively block UV photons (∼30.5% at 320 nm) at glass substrate and convert them to the red emission thanks to 5D0 →7Fj (j = 0, 1, 2, 3, and 4) Eu (III) electronic transitions. Photodegradation experiments with methylene blue dye revealed that TiO2−Eu thin films offer better UV protection compared to uncoated samples. We strongly believe that porous TiO2−Eu thin films can be effectively utilized as a UV blocking and light conversion coating.

A simple method for functionalization of polypyrrole-coated cotton fabrics by reduced graphene oxide for UV screening

Here, the modified Hummer’s method was used to prepare reduced graphene oxide (RGO) nanostructures. The functional properties of the prepared RGO nanostructures were studied by using the X-ray diffraction method (XRD), and scanning electron microscopy (SEM). Using the in situ polymerization process, polypyrrole (PPy) was prepared. During polymerization, an ultrasound-assisted coating process was used to coat the cotton fabrics. In addition, the Nafion@RGO composite mixture was deposited on the surface of PPy- coated cotton fabric by dip and dry method. The presence of cellulose crystal structure was confirmed by conducting a structural study of the coated and uncoated (UC) cotton fabrics. The presence of a characteristic functional group was confirmed by the Fourier transform infrared spectroscopy–Attenuated total reflection (FTIR–ATR) study of the fabrics. Wrinkled-like morphology with a proper binding of PPy with RGO was revealed by SEM analysis. Our results showed that the RGO coated fabrics could be distributed on the cotton fabric and possessed better thermal stability and wettability properties than uncoated cotton fabric. Ultraviolet (UV)-screening properties of the coated and uncoated fabrics confirmed the better performance of the coated cotton fabrics in the order of Nafion/RGO coated fabrics (RGPC) > PPy/Cotton (PC) > UC. The transmission and screening efficiency of RGO coated fabrics were 0.02% and 99.98%, respectively. Thus the Nafion/RGO/PPy fabrics is a safe and promising UV screening and have great potential application in the all wearable textile sector.

Ultraviolet screening by slug tissue and tight packing of plastids protect photosynthetic sea slugs from photoinhibition

One of the main mysteries regarding photosynthetic sea slugs is how the slug plastids handle photoinhibition, the constant light-induced damage to Photosystem II of photosynthesis. Recovery from photoinhibition involves proteins encoded by both the nuclear and plastid genomes, and slugs with plastids isolated from the algal nucleus are therefore expected to be incapable of constantly repairing the damage as the plastids inside the slugs grow old. We studied photoinhibition-related properties of the sea slug Elysia timida that ingests its plastids from the green alga Acetabularia acetabulum. Spectral analysis of both the slugs and the algae revealed that there are two ways the slugs use to avoid major photoinhibition of their plastids. Firstly, highly photoinhibitory UV radiation is screened by the slug tissue or mucus before it reaches the plastids. Secondly, the slugs pack the plastids tightly in their thick bodies, and therefore plastids in the outer layers protect the inner ones from photoinhibition. Both properties are expected to greatly improve the longevity of the plastids inside the slugs, as the plastids do not need to repair excessive amounts of damage.

Carrier transport and shielding properties of rod-like mesoporous TiO2–SiO2 nanocomposite

Synthesizing material candidates having both high ultraviolet (UV) absorbing capacity and low photoactivity is a paramount challenge. The present study reports the sonosynthesis of titanium oxide (TiO2) - silicon dioxide (SiO2) nanocomposite that possesses good UV screening efficacy but reduced photoactivity. It was observed that the synthesized TiO2–SiO2 (TS11) composite with a 1:1 M ratio of TiO2 and SiO2 precursors showed lower photoactivity (25.91% pollutant degradation in 300 min) while maintaining its UV shielding properties (20% UV transmittance in 200–400 nm region). The surface area and average pore diameter of TS11 nanocomposite was found to be 2 m2g-1 and 18.8 nm as per Barrett- Joyner- Halenda (BJH) analysis. Low photoactivity could be accounted to the reduced surface area and unique rod-like morphology of the TS11 composite that probably trapped the photoactive TiO2 particles within the SiO2 rods. The TS11 nanocomposite showed tunable band gap in comparison to that of bare TiO2 and SiO2 which is desirable for optoelectronic applications. The carrier transport properties were evaluated by fabricating an ITO/TS11/Al based Schottky diode. Lower carrier mobility, diffusion length and higher transit time under illumination in comparison to other TiO2 composites appears consistent with reduced photoactivity.

Unravelling the photoprotective effects of freshwater alga Nostoc commune Vaucher ex Bornet et Flahault against ultraviolet radiations.

Several studies have suggested the direct relationship between skin complications, air pollution, and UV irradiation. UVB radiations cause various skin complications such as skin aging, skin inflammation, and skin cancer. The current study is designed to develop an ultraviolet (UV) absorbing MAA-loaded topical gel and to evaluate its UVA and UVB screening potential. MAA was extracted from the Nostoc commune Vaucher ex Bornet et Flahault (N. commune) and characterized by HPLC-PDA (with a retention time 2.6 min), UV-Visible (absorption maximum 334 nm), and mass spectrometry (m/z 346.2) techniques. The methanolic (10%) solution of MAA (50-150 μl) was dissolved in propylene glycol and mixed with hydrated gel (1.5 % of carbopol 934) by using EDTA (0.3%). Eight (F1-F8) formulations were evaluated for their physico-chemical characters. F7 retained its physio-chemical characters for 90 days. Further selected formulation (F7) was evaluated for its gelling strength (GSg), gelling temperature (GT), melting temperature (MT), apparent viscosity (cp), molecular mass (MMS), pH, physical appearance, homogeneity, and spreading diameter (SD). The stability study of the fabricated gel formulation was done as per International Committee on Harmonization guidelines and sunscreen potential was determined by in vitro sunscreen UV method. Findings revealed that GSg (337 ± 1.7 g/cm2), GT (22.8 ± 0.2 °C), cp (71.1 ± 0.2), MMS (424.177 ± 0.7), pH (6.2 ± 0.04), and SD (56 ± 0.2). For in vitro sunscreen potential determination, different concentrations of F7 (50-150 μl) were prepared. Topical application of the F7 displayed UV-A/UV-B photoprotection with SPF 1.13 folds greater then marketed formulation (Lotus herbals UV screen gel). Based on these findings, it was concluded that methanolic extract derived from N. commune contains Porphyra-334 which can be potentially used as photo protective compound in several cosmetic preparations. Development of sunscreen gel from Nostoc commune The current investigation is designed to develop ultraviolet (UV) absorbing MAA (mycosporine amino acid)-loaded topical gel from Nostoc commune to evaluate its UVA and UVB screening potential. LCMS characterization of HPLC-PDA purified MAA from N. commune methanolic extract demonstrated a prominent ion peak of a protonated molecule ([M + H]+) at m/z 346.2 [M+H]+ value confirmed the presence of Porphyra-334. Porphyra-334 is a broad-spectrum sun-protective compound evidenced for its potential in blocking UVA and UVB (Bhatia et al. 2010). Prepared sunscreen formulations remain stable for prolonged period and provide broad-spectrum protection against harmful UV range.

Tannic interfacial linkage within ZnO-loaded fabrics for durable UV-blocking applications

To defend against the impact of ultraviolet (UV) irradiation from daily life and even changes in climate and stratospheric ozone, wearing UV-protective clothing is a simple and effective approach to reduce risks to human health from excessive UV exposure. However, normal clothes with traditional dye or additional modifications have limited UV-blocking activity and low washing fastness, bringing huge pressure on the environment. Herein, we applied a bio-interfacial material, tannic acid, to enhance the π interaction for better reusability of the nanostructured zinc oxide (ZnO) modified highly-improved-UV-protective natural textiles, which ultraviolet protection factor (UPF) maintained 309 despite 50 washing cycles. Moreover, the UV-protective properties of cotton-based or wool-based samples have both been significantly enhanced to UPF 500, which increased up to 4200 % compared to the previous metal salt ultraviolet screening agent method. Additionally, the endowed UV-protective characteristic contributed to tensile mechanical properties of modified wool textiles even after 120-hour UV irradiation. This biomass-inspired interface facilitated in-situ synthesis method suggested a promising strategy to take full advantage of the inner and outer walls of natural hollow fibre substrates to deposit active materials for advanced protective textiles.

Secondary metabolites and related genes in Vitis vinifera L. cv. Tempranillo grapes as influenced by ultraviolet radiation and berry development.

The effects of UV radiation on Vitis vinifera cv Tempranillo grapes were studied under field conditions as influenced by ultraviolet (UV) band (UV-A and UV-B), UV-B level (ambient vs enhanced), grape phenological stage (pea-size, veraison, and harvest), grape component (skin, flesh, and seeds), and fraction from which phenolic UV-absorbing compounds (UVACs) were extracted (soluble vs insoluble). Ambient UV-B levels caused stronger effects than ambient UV-A. These effects included increases in flavonol contents (particularly quercetins and kaempferols), the expression of flavonol synthase and chalcone synthase genes (VvFLS4 and VvCHS1), and grape weight and size. In addition, the contents of flavanols and hydroxycinnamic acids increased under UV-B radiation at pea-size stage. All these compounds play physiological roles as antioxidants and UV screens. Synergic effects between UV-B and UV-A were observed. The responses of anthocyanins, stilbenes, and volatile compounds to UV were diffuse or nonexistent. Enhanced UV-B led to rather subtle changes in comparison with ambient UV-B, but differences between both treatments could be demonstrated by multivariate analysis. Pea-size and harvest were the phenological stages where the most significant responses to UV were found, while the skin was the most UV-responsive grape component. Soluble phenolic compounds were much more UV-responsive than insoluble compounds. In conclusion, UV radiation was essential for the induction of specific grape phenolic and volatile compounds. Given the physiological roles of these compounds, as well as their contribution to grape and wine quality, and their potential use as nutraceuticals, our results may have implications on the artificial manipulation of UV radiation.

Effect of Screen House on Disease Severity and Coat Protein Diversity of Begomovirus-infected Capsicum frutescens L. ‘Cempluk’ from Indonesia

Chili can be infected by Begomovirus through whiteflies (Bemisia tabaci) serving as a vector insect. Begomovirus infection causes dwarf plants and yellow curly leaves. The molecular detection of Begomovirus coat protein gene may serve as a preliminary identification of Begomovirus. This study was conducted to observe the differences in the symptom severity of Begomovirus infection in chilies (Capsicum frutescens L. ‘Cempluk’) planted inside and outside a screen house. This study also observed whether or not using a screen house in chili farming affects the diversity of the coat protein of Begomovirus. Symptom observation and sampling were conducted in Madurejo, Prambanan, Sleman. Molecular detection was performed by amplifying the coat protein (CP) gene using the universal primer Krusty and Homer. Results showed 7 plant samples with DNA bands ± 550 bp and confirmed that the plants were positively infected with Begomovirus. The amplified bands were purified and sequenced. The nucleotide sequences were analyzed using BLASTn, followed by phylogenetic analysis using MEGA. Planting chili in the screen house resulted in low disease severity and good crop conditions. The coat protein sequence showed different strains of Begomovirus infected the chili plants inside and outside the screen house. Pepper yellow leaf curl Indonesia virus (PepYLCIV) was found inside the screen house while PepYLCIV [Ageratum] was dominant outside the screen house. Both strains are closely related to other Pepper yellow leaf curl virus (PepYLCV) from various regions in Indonesia. Optical manipulation using an ultraviolet screen or screen house was effective in reducing Begomovirus infection and improving plant performance.

Ultraviolet light screen using cholesteric liquid crystal capsules on the basis of selective reflection.

Sunscreen can protect human skin from sunlight by decreasing exposure to ultraviolet (UV) light, specifically UV-B and UV-A. In this study, a new type of UV screen system is proposed using cholesteric liquid crystal (CLC) capable of selectively reflecting UV-A within the human skin temperature range of 32–36 °C. Polycaprolactone (PCL) capsules with CLC mixture which had a helical chiral pitch corresponding to the wavelength of UV light were made by a solvent evaporation method. The average diameter of the capsules was about 34 μm. Consequently, it was confirmed that the CLC mixture (COC : CN = 80 : 20) could reflect UV-A light over 350–380 nm within the human skin temperature range. Also, it was confirmed that the CLC/PCL microcapsules could block UV light over 290–400 nm by about 6%.

Pectin-Based Films with Cocoa Bean Shell Waste Extract and ZnO/Zn-NPs with Enhanced Oxygen Barrier, Ultraviolet Screen and Photocatalytic Properties.

In this work, pectin-based active films with a cocoa bean shell extract, obtained after waste valorisation of residues coming from the chocolate production process, and zinc oxide/zinc nanoparticles (ZnO/Zn-NPs) at different concentrations, were obtained by casting. The effect of the active additive incorporation on the thermal, barrier, structural, morphological and optical properties was investigated. Moreover, the photocatalytic properties of the obtained films based on the decomposition of methylene blue (MB) in aqueous solution at room temperature were also studied. A significant increase in thermal and oxidative stability was obtained with the incorporation of 3 wt% of ZnO/Zn-NPs compared to the control film. The addition of 5 wt% cocoa bean shell extract to pectin significantly affected the oxygen barrier properties due to a plasticizing effect. In contrast, the addition of ZnO/Zn-NPs at 1 wt% to pectin caused a decrease in oxygen transmission rate per film thickness (OTR.e) values of approximately 50% compared to the control film, resulting in an enhanced protection against oxidation for food preservation. The optical properties were highly influenced by the incorporation of the natural extract but this effect was mitigated when nanoparticles were also incorporated into pectin-based films. The addition of the extract and nanoparticles resulted in a clear improvement (by 98%) in UV barrier properties, which could be important for packaged food sensitive to UV radiation. Finally, the photocatalytic activity of the developed films containing nanoparticles was demonstrated, showing photodegradation efficiency values of nearly 90% after 60 min at 3 wt% of ZnO/Zn-NPs loading. In conclusion, the obtained pectin-based bionanocomposites with cocoa bean shell waste extract and zinc oxide/zinc nanoparticles showed great potential to be used as active packaging for food preservation.

Phototrophic biofilms and microbial mats from the marine littoral of the central Mediterranean

Phototrophic biofilm and microbial mat communities grow along the rocky coastline of the Maltese islands. This research involved studying phototrophs from the mediolittoral and supralittoral zones over a two-year period and seasonal changes were observed. Attachment of pioneer microorganisms to the porous eroded limestone bedrock was facilitated via a gelatinous matrix composed of exopolymeric substances (EPS). In submerged areas, such as undisturbed rock pools, these progressively formed green or brown compact biofilms, some of which thickened over the spring to form microbial mats via the production of more extensive EPS layers. Microbial mats gradually attained a lighter colouration due to the presence of ultraviolet (UV) screening pigments. In full summer, they were observed to shrink, detach from the exposed substrate, harden and progressively calcify. Biofilm microorganisms survived the harsh summer months in sheltered areas. The major biofilm formers were filamentous non-heterocytous cyanobacteria belonging to the Leptolyngbyaceae, Pseudanabaenaceae and Oscillatoriaceae. Their sheaths were thick, lamellated and often confluent. A higher biodiversity of phototrophs was observed in late autumn and winter, when tufts of heterocytous Calothrix sp. grew on thin compact biofilms of Nodosilinea sp., Toxifilum sp. and Phormidesmis spp., while Lyngbya spp. trichomes were surrounded by thick brown sheaths. Germlings of green and brown macroalgal species belonging to Ulva, Cladophora and Sphacelaria were embedded in biofilms and microbial mats and gradually grew to form extensive macroalgal covers submerged in rock pools. Erythrotrichia sp. filaments colonised the mediolittoral zone and were confined to areas that were exposed to wave action and submerged intermittently. Over the summer, macroalgal coverage diminished and microalgal biofilms and microbial mats prevailed in rock pools.

Feasibility of spectral pH measurement during the low-pH virus inactivation step of continuous therapeutic antibody production.

Acidic virus inactivation is commonly used during production of biotherapeutic products to provide virus safety in case of undetected virus contamination. Accurate pH measurement is required to ensure the product pH reaches a virus-inactivating level (typically 3.5-3.7), and a level post-inactivation that is appropriate for later purification steps (typically 5.5-7.5). During batch low-pH inactivation in discrete tanks, potentiometric glass probes are appropriate for measuring pH. During continuous inactivation for 2-3 weeks in an enclosed product stream, probe calibration drift and lag may lead to poor accuracy, and operational difficulties when compensating for drift. Monitoring the spectral response of compounds (indicators) in the product stream whose spectra are pH-sensitive offers a possible alternative way to measure pH without these drawbacks. Such indicators can already exist in the stream (intrinsic) or can be added (extrinsic). Herein are reported studies evaluating the feasibility of both.Promising ultraviolet screening results with the two extrinsics studied, thiamine and ascorbic acid, led to the addition of both to product stream samples titrated to different potentiometric pH values in the 3.3-4.5 range (a representative range encountered during continuous inactivation), and attempts to model pH using sample ultraviolet spectra. One model, based on variability in six spectral attributes, was able to predict pH of an independent sample set within ±0.07 units at the 95% confidence level. Since a typical inactivating pH tolerance is ±0.1 units, the results show that extrinsic indicators potentially can measure inactivation pH with sufficient accuracy. Suggested future steps and an alternative approach are presented.

Ultraviolet screening increases with elevation in translucent bracts of Rheum nobile (Polygonaceae), an alpine ‘glasshouse’ plant from the high Himalayas

Abstract Specialized bracts of Himalayan ‘glasshouse’ plants are well known for adapting to diverse stresses in alpine environments, thus ensuring normal sexual reproduction. However, little information is available on how such specialized plants cope with the elevational increase in stress. In this study, we determine the elevational pattern of ultraviolet (UV) protection provided by the translucent bracts of Rheum nobile, a giant ‘glasshouse’ plant species, endemic to the high Himalayas, and examine its effect on pollen germination and pollen tube growth. Both UV-A and UV-B radiation in the open air increased with elevation, but their intensity beneath bracts remained constant with elevation, suggesting that the bracts of R. nobile growing at higher elevations have an increased ability to screen UV radiation. Enhanced UV-B radiation, equivalent to that experienced at higher elevations (4800 m a.s.l.) compared to that at lower elevations (4200 m a.s.l.), significantly reduced pollen germination and pollen tube growth. Pollen grains from plants at higher elevations were not more tolerant to UV-B radiation. UV absorbance and the content of flavonoids in bracts increased with elevation, but a similar trend was not found in either UV reflectance or adaxial trichome density, suggesting that bract UV absorbance may play a more active role than bract UV reflectance in helping plants cope with the increasing UV radiation. Our results indicate that the bracts of R. nobile have the ability to cope with enhanced UV radiation with increasing elevation through increased UV absorbance, thus protecting pollen grains from injury caused by higher levels of UV radiation, and consequently ensuring normal sexual reproduction in stressful high-alpine conditions.

Dual roles of a transparent polymer film containing dispersed N-doped carbon dots: A high-efficiency blue light converter and UV screen

We report the synthesis of a transparent plastic material with very high performance ultraviolet (UV)-blocking and blue-light (440 nm) emission. Polyvinyl alcohol (PVA) was employed as a transparent plastic matrix that disperses N-doped carbon dots (N-CDs) prepared via hydrothermal treatment of citric acid, ethylene diamine, and HCl solution. Luminescence of these N-CDs is excitation-independent and the quantum yield (QY) is maximal at an excitation wavelength range of 350–370 nm, in the UV-A radiation segment of the solar spectrum. By encapsulating N-CDs in a polyvinyl alcohol (PVA) matrix, the absolute QY achieves 91%, which is higher than in aqueous solution. As the particle concentration increases in PVA matrix or in solution, UV absorbance increases and QY decreases. On the other hand, UV absorbance of the film is proportional to thickness with no appreciable deterioration in QY, a quality that is beneficial for UV light absorption as well as conversion into blue light. We propose that this N-CD/PVA composite is an ideal transparent plastic for UV-ray shielding, as well as being useful for blue light emission, composed only of eco-friendly nontoxic elements. The high UV absorption and strong luminescence of N-CDs are beneficial also for other applications that include anti-counterfeiting (secret inks) and greenhouse sheathing that simultaneously blocks UV-rays while generating blue light to promote plant growth.