Blue Light Radiation Research Articles

Luminescence enhancement of Ca3Sr3(VO4)4:Eu3+, Sm3+ red-emitting phosphor by charge compensation

A series of red-emitting phosphors Ca3Sr3(VO4)4:0.05Eu3+; Ca3Sr3(VO4)4:0.05Eu3+, xSm3+; and Ca3Sr3(VO4)4:0.05Eu3+, 0.05Sm3+, yM+ (M = Li, Na, and K) were fabricated with the combustion method. The microstructure and photoluminescence properties of the phosphors were investigated via X-ray powder diffraction, scanning electron microscopy, and photoluminescence spectroscopy. The obtained results revealed that all samples perfectly matched the rhombohedral structure with R3c space group. The results showed that the luminescence properties of Eu3+ ions could evidently be improved by co-doping with Sm3+ ions. When the doping mole fraction of Sm3+ ions was 5%, the relative luminous intensity at 619 nm was maximal under an excitation of 464 nm. Moreover, incorporation of charge compensators (i.e., Li+, Na+, and K+) could improve both the luminescence intensity and thermal stability of phosphors under an excitation of 464 nm and this paper discusses and interprets the underlying reason. The optimal concentration of the charge compensator M+ (M = Li, Na, and K) was 5%. In particular, the Li+-doped sample exhibited significantly enhanced emission intensity and thermal stability under an excitation wavelength of 464 nm and its emission intensity was approximately 1.9-fold of that of Ca3Sr3(VO4)4:0.05Eu3+, 0.05Sm3+. Furthermore, the CIE chromaticity coordinate of Ca3Sr3(VO4)4:0.05Eu3+, 0.05Sm3+, 0.05Li+ phosphor was found to be closer to the standard red-emitting point (x = 0.67, y = 0.33) compared to Ca3Sr3(VO4)4:0.05Eu3+, 0.05Sm3+. The luminescence performance of Ca3Sr3(VO4)4:Eu3+, Sm3+, Li+ upon excitation with blue light radiation makes this a potential red-emitting phosphor for application in blue-based white light emitting diodes.

Facile one-step synthesis and luminescent properties of red-emitting Ca2Si5N8:Eu2+ phosphors

Ca2Si5N8:Eu2+ phosphors have been synthesised in a facile one-step route using raw materials including α-Si3N4, CaCO3, Ca(CH3COO)2 and Eu2O3. Compared with the prevailing conventional methods, an inexpensive and simple method under atmospheric pressure with a relative short reaction time is achieved. The reaction process is optimised to obtain Ca2Si5N8:Eu2+ phosphors with high crystallinity and purity. The phosphors exhibit a red emission peaking at 592 nm under a blue light radiation and show a broad excitation band between 250 and 550 nm. The characteristics of broad excitation band and red emission imply a promising application in blue light-based red light-emitting diode and white light-emitting diode (LED). These results indicate a promising prospect for the efficient and economic route in preparing Ca2Si5N8:Eu2+ phosphors for LED applications.

Active-Site pKa Determination for Photoactive Yellow Protein Rationalizes Slow Ground-State Recovery

The ability to avoid blue-light radiation is crucial for bacteria to survive. In Halorhodospira halophila, the putative receptor for this response is known as photoactive yellow protein (PYP). Its response to blue light is mediated by changes in the optical properties of the chromophore para-coumaric acid (pCA) in the protein active site. PYP displays photocycle kinetics with a strong pH dependence for ground-state recovery, which has remained enigmatic. To resolve this problem, a comprehensive pKa determination of the active-site residues of PYP is required. Herein, we show that Glu-46 stays protonated from pH 3.4 to pH 11.4 in the ground (pG) state. This conclusion is supported by the observed hydrogen-bonded protons between Glu-46 and pCA and Tyr-42 and pCA, which are persistent over the entire pH range. Our experimental results show that none of the active-site residues of PYP undergo pH-induced changes in the pG state. Ineluctably, the pH dependence of pG recovery is linked to conformational change that is dependent upon the population of the relevant protonation state of Glu-46 and the pCA chromophore in the excited state, collaterally explaining why pG recovery is slow.

Responses of Crepis japonica induced by supplemental blue light and UV-A radiation

Crepis japonica (L.) D.C. (Asteraceae), a weed with antioxidant, antiallergenic, antiviral and antitumor properties displays both medicinal properties and nutritional value. This study aims to assess the effects of a supplementation of blue light and UV-A radiation on the growth, leaf anatomical structure and phenolic profile of the aerial parts of Crepis japonica. Plants were grown under two light treatments: W (control - white light), W + B (white light supplemented with blue light) and W + UV-A (white light supplemented with UV-A radiation). We recorded the length, width, and weight of fresh and dry leaves, the thickness of the epidermis and mesophyll, and stomata density. The phenolic profiles of the aqueous extracts of the aerial parts were analyzed by HPLC-DAD. There was an increase in the leaf size, stomatal density, and phenolic production, and a thickening of the mesophyll and epidermis. UV-A radiation increased the phenolic production more than blue light. Blue light and UV-A radiation both improved the production of caffeic acid by about 6 and 3 times, respectively, in comparison to control. This compound was first reported as a constituent of the extract from the aerial parts together with caftaric acid. UV-A also promoted the production of chlorogenic acid (about 1.5 times in comparison to the control). We observed that the morphological and chemical parameters of C. japonica are modified in response to blue light and UV-A radiation, which can be used as tools in the cultivation of this species in order to improve its medicinal properties and nutritional value.

Hydrothermal synthesis of narrow-band red emitting K2NaAlF6:Mn4+phosphor for warm-white LED applications

The truncated octahedron shaped K2NaAlF6:Mn4+was preparedviahydrothermal route, which emits red light under blue light radiation. Warm WLEDs fabricated by the obtained red phosphor show lower color temperature and higher color rendering index.

The treatment of crigler-najjar syndrome by blue light as explained by resonant recognition model

The Crigler-Najjar syndrome is extremely rare genetic disease, that is manifested by severe jaundicedue to lack of UDP glucuronosyltransferase 1-A1 (UDP) activity. The main treatment is to use the blue lightphototherapy, during the prolong time, during the day every day. Here, we analyzed human UDP’s correlation with the blue light phototherapy using the nonlinear physico-mathematical model: Resonant Recognition Model (RRM), which proposes that protein activation is electromagnetic in nature within the frequency range of infrared and visible light. We found that human UDP’s are characterized by specific RRM frequency that is related to the blue light radiation. This could be the explicit explanation, why phototherapy with the blue light could replace lack of UDP activity. However, the blue light treatment is less effective with ageing, due to decrease of the blue lightpenetration through skin. Thus, there is a need for alternative treatments. Here, we propose to design de-novopeptide, using this specific RRM frequency. Such peptide, according to RRM, is proposed to have the samebiological function as UDP glucuronosyltransferase 1-A1 and thus can be used for alternative treatment of Crigler-Najjar syndrome.

Dual Improvement of Red Emission and Ferroelectric Properties in Plumbum-Free Ba4La0.666−x Eu x Nb10O30 Ceramics

Luminescent ferroelectric materials (LFM) have attracted considerable attention in recent years for the design and development of new multifunctional devices. In this work, different from conventional perovskite and bismuth layer-structured LFM, new plumbum-free LFM comprised of Ba4La0.666−xEuxNb10O30 (BLEN-x) were synthesized. All BLEN-x possess tetragonal tungsten bronze (TTB) structure with space group P4bm. Strong red emission, corresponding to the transitions of 5D0 to 7FJ (J = 1, 2, 3, 4), is observed that can be availably excited by both near ultraviolet (NUV) and blue light radiation. Meanwhile, greatly enhanced ferroelectric properties are also demonstrated. The effective regulation of luminescent and ferroelectric properties in present TTB-type compounds provides a reasonable route to develop LFM in the future.

Blue Light and Ultraviolet Radiation Exposure from Infant Phototherapy Equipment

Phototherapy is the use of light for reducing the concentration of bilirubin in the body of infants. Although it has become a mainstay since its introduction in 1958, a better understanding of the efficacy and safety of phototherapy applications seems to be necessary for improved clinical practices and outcomes. This study was initiated to evaluate workers’ exposure to Optical Radiation from different types of phototherapy devices in clinical use in Italy.During infant phototherapy the staff monitors babies periodically for around 10 min every hour, and fixation of the phototherapy beam light frequently occurs: almost all operators work within 30 cm of the phototherapy source during monitoring procedures, with most of them commonly working at ≤25 cm from the direct or reflected radiation beam.The results of this study suggest that there is a great variability in the spectral emission of equipments investigated, depending on the types of lamps used and some phototherapy equipment exposes operators to blue light photochemical retinal hazard.Some of the equipment investigated presents relevant spectral emission also in the UVA region. Taking into account that the exposure to UV in childhood has been established as an important contributing factor for melanoma risk in adults and considering the high susceptibility to UV-induced skin damage of the newborn, related to his pigmentary traits, the UV exposure of the infant during phototherapy should be “as low as reasonably achievable,” considering that it is unnecessary to the therapy. It is recommended that special safety training be provided for the affected employees: in particular, protective eyewear can be necessary during newborn assistance activities carried out in proximity of some sources. The engineering design of phototherapy equipment can be optimized. Specific requirements for photobiological safety of lamps used in the phototherapy equipment should be defined in the safety product standard for such equipment.

Session 21.8 – Challenges and Solutions to Light Pollution, RFI and Implementing IAU Resolution 2009 B5

AbstractThe closing session included a panel on the challenge of raising cultural awareness of the negative effects of light pollution and RFI, and a discussion about the means to implement the IAU Resolution on the Right to Starlight. The strongest arguments to the public are that light pollution wastes precious energy and adds greenhouse gases, and that artificial light at night can be damaging to human health and to the natural environment. As astronomers, our community is concerned that the world is blinding itself to the electromagnetic radiation connecting us to the Universe. An outcome of successful advocacy would be to create demand for commercial products that minimize blue light and upward radiation. Implementation of the resolution on the Right to Starlight has multiple aspects. The IAU, through its site protection commission, should provide a clear technical description of "astronomy friendly" lighting and specifications for protection of the near zones around optical observatories. In addition, the commission should provide reference materials for astronomers giving public presentations, provide a forum for those seeking stronger local or national regulation, seek IAU approval for endorsement of protected status of sites and regions, and support the process of gaining UNESCO World Heritage Status for observatories and their regions.

Long-term stability of CdSe/CdZnS quantum dot encapsulated in a multi-lamellar microcapsule

We developed a novel and easy encapsulation method for quantum dots (QDs) using a partially oxidized semi-crystalline polymeric material which forms a micron-sized granule with a multi-lamellar structure from a dilute solution. The QDs were highly dispersed in the granule in such a way that they were adsorbed on the lamella with ∼12 nm spacing followed by lamellar stacking. The QDs were heavily loaded into the granule to 16.7 wt% without aggregation, a process which took only a few minutes. We found that the quantum yield of the QDs was not degraded after the encapsulation. The encapsulated QD–silicone composite exhibited excellent long-term photo- and thermal stability with its initial photoluminescence intensity maintained after blue LED light radiation for 67 days and storage at 85 °C and 85% relative humidity for 119 days.

Analytical investigations of thermoluminescence glow curve on quartz for luminescence dating

Investigations of bleaching and thermoluminescence (TL) response to radiation dose of quartz are importance in luminescence dating. Although such research has been extensively carried out for various types of quartz, most work was performed on the basis of TL intensity integrated for a particular temperature range on the glow curve, without any peak separation. In this study we investigated bleaching by a blue light stimulation and radiation dose behaviour for separated TL glow peaks of quartz, which are thermally stable, by using the computerized glow curve deconvolution (CGCD) method combined with the Tm–Tstop method. The Tm–Tstop method indicates that the glow curve of quartz is the superposition of at least seven components (P1–P7) in the temperature range between room temperature and 450 °C. A bleaching experiment for four thermally stable glow peaks (P4–P7) using a blue light stimulation revealed that the bleaching rate of peak P4 exhibits three different exponential decays, whereas the peaks P5, P6 and P7 are bleached with two different exponential decays. After bleaching of 12 h, the TL intensity of peaks P4, P5, P6 and P7 were reduced to approximately 6%, 16%, 26% and 68% of the initial value, respectively. Additionally, in a study of the radiation dose response of the four thermally stable glow peaks, all peaks have a similar pattern, which are well fitted by a single saturating exponential function.

Photobiological safety of the recently introduced energy efficient household lamps.

Nowadays more and more newly introduced light sources (tungsten-halogen, compact fluorescent (CFL) and light-emitting diode (LED) lamps) are used in households. It is important to know whether their radiation poses any possible risk for human health or not. These light sources emit optical radiation not solely in the visible spectrum. Other bands emitted by these sources, i.e., ultraviolet and infrared, are potentially hazardous for human health. The visible light, especially the blue light, could also damage human retina. The purpose of this study was to determine the ultraviolet (UV) and blue light (BL) emissions from halogen bulbs, CFLs and LED lamps, and to evaluate them from the point of view of possible health risks for general public. The exposure of UV and BL emissions from 19 types of CFLs, 11 types of halogen lamps and 4 types of LED lamps produced by different manufacturers were measured at 200 mm distance from the source. The exposures to UV and BL were below the International Commission on Non-Ionizing Radiation Protection (ICNIRP) exposure limits in spite of the very conservative assumption of the assessment. Results of this study indicate that the UV and BL radiation from the newly introduced lamps does not exceed the current exposure limit values and thus, in comparison with the former incandescent bulbs, does not result in a higher risk for general public.

Suppression of Cucumber Powdery Mildew by Supplemental UV-B Radiation in Greenhouses Can be Augmented or Reduced by Background Radiation Quality.

This study demonstrates that the spectral quality of radiation sources applied with ultraviolet-B (UV-B; background radiation) affects the suppression of cucumber powdery mildew (Podosphaera xanthii) by UV-B. Suppression provided by daily UV-B exposure of 1 W/m2 for 10 min was greatest in the presence of red light or by a complete lack of background light, and powdery mildew suppression was least in the presence of ultraviolet-A (UV-A) or blue radiation compared with plants exposed only to 16 h of daily natural light supplemented with high-pressure sodium lamps that supply broad-spectrum radiation with peaks in the yellow-orange region. Exposure of powdery mildew-inoculated plants to supplemental red light without UV-B, beginning at the end of the daylight period, also reduced disease severity; however, supplemental blue light applied in the same fashion had no effect. Daily application of UV-B at 1 W/m2 beginning on the day of inoculation significantly reduced the severity of powdery mildew to 15% compared with 100% severity on control plants. Maximum suppression of powdery mildew was observed following 15 min of exposure to UV-B (1.1% severity compared with 100% severity on control plants) but exposure time had to be limited to 5 to 10 min to reduce phytotoxicity. There was no additional disease suppression when plants were exposed to UV-B beginning 2 days prior to inoculation compared with plants exposed to UV-B beginning on the day of inoculation. UV-B inhibited germination, infection, colony expansion, and sporulation of P. xanthii. The results suggest that efficacy of UV-B treatments, alone or in combination with red light, against P. xanthii can be enhanced by exposure of inoculated plants to these wavelengths of radiation during the night, thereby circumventing the counteracting effects of blue light and UV-A radiation. The effect of UV-B on powdery mildew seemed to be directly upon the pathogen, rather than induced resistance of the host. Night exposure of plants to 5 to 10 min of UV-B at 1 W/m2 and inexpensive, spectral-specific, light-emitting diodes may provide additional tools to suppress powdery mildews of diverse greenhouse crops.

Bright green emission in Ho doped Bi1/2Na1/2TiO3 ferroelectric ceramics

A series of Ho3+ doped Bi1/2Na1/2TiO3 (BNTO: x Ho3+, x=0.0, 0.002, 0.005, 0.01, 0.02, 0.03, 0.04, 0.05, and 0.07) ceramics were synthesized by a solid-state reaction, and their structural, photoluminescence, and ferroelectric properties were investigated. Bright green emission of BNTO: x Ho3+ was first observed at room temperature, and what is more, the green emission can be directly excited by blue light radiation which indicates BNTO: x Ho3+ can act as a highly efficient phosphor. Furthermore, the optimized photoluminescence is observed in BNTO: x Ho3+ with x=0.01 sample which also shows good ferroelectric properties. It is believed that BNTO: x Ho3+ with x=0.01 may act as a potentially multifunctional optical-electro material.

Photoluminescence and ferroelectric properties in Eu doped Bi4Ti3O12–SrBi4Ti4O15 intergrowth ferroelectric ceramics

Photoluminescence excitation (PLE) spectra monitored at 614 nm and photoluminescence (PL) spectra excited at 464 nm of BIT–SBTi: x Eu 3+ with x = 0.7 at room temperature. The left inset of this Figure shows a polarization–electric field ( P–E ) hysteresis loop of x = 0.7. The right inset of this Figure gives a luminescence photograph of x = 0.7 under the excitation of a blue light. • Photoluminescence of the BIT–SBTi: x Eu 3+ ceramics were first reported. • Bright red emission excited by blue light has been observed at room temperature. • Enhanced ferroelectric and dielectric properties were obtained for BIT–SBTi: x Eu 3+ . A series of Eu 3+ doped intergrowth Bi 4 Ti 3 O 12 –SrBi 4 Ti 4 O 15 (BIT–SBTi: x Eu 3+ ) (0.0 ⩽ x ⩽ 4) ceramics were prepared through a solid-state reaction method. Contrast with conventional ferroelectric (FE) research, here, we report the photoluminescence (PL) properties of BIT–SBTi: x Eu 3+ system for the first time. Bright red emission was observed at room temperature. It should be noted that the red emission of BIT–SBTi: x Eu 3+ can be excited by both blue light and near ultraviolet (NUV) radiation. Optimized emission intensity was obtained when x = 2 for BIT–SBTi: x Eu 3+ . Moreover, the FE and dielectric properties of BIT–SBTi: x Eu 3+ were also investigated. BIT–SBTi: x Eu 3+ with x = 0.7 ceramic exhibits optimized FE and dielectric behavior. The multifunctional properties of BIT–SBTi: x Eu 3+ ceramics were confirmed in this work.

Photoluminescence properties in Sm doped Bi1/2Na1/2TiO3 ferroelectric ceramics

Sm 3+ ions doped Bi 1/2 Na 1/2 TiO 3 (BNTO: x Sm 3+ ) polycrystalline samples with different Sm 3+ concentrations were synthesized through the solid-state reaction method. Their microstructural, photoluminescence, and ferroelectric (FE) properties were investigated. Strong reddish-orange emission centered at 597 nm has been successfully observed at room temperature. More importantly, the strong emission of BNTO: x Sm 3+ can be excited by both blue light and near ultraviolet radiation which indicates that BNTO: x Sm 3+ can act as a potential phosphor. Furthermore, the optimized photoluminescence is realized in BNTO: x Sm 3+ with x =0.02 sample which also shows relatively good ferroelectric properties.

Increased Antioxidant Activity and Changes in Phenolic Profile of Kalanchoe pinnata (Lamarck) Persoon (Crassulaceae) Specimens Grown Under Supplemental Blue Light

Antioxidant compounds protect plants against oxidative stress caused by environmental conditions. Different light qualities, such as UV-A radiation and blue light, have shown positive effects on the production of phenols in plants. Kalanchoe pinnata (Lamarck) Persoon (Crassulaceae) is used for treating wounds and inflammations. Some of these beneficial effects are attributed to the antioxidant activity of plant components. We investigated the effects of blue light and UV-A radiation supplementation on the total phenol content, antioxidant activity and chromatographic profile of aqueous extracts from leaves of K. pinnata. Monoclonal plants were grown under white light, white plus blue light and white plus UV-A radiation. Supplemental blue light improved the antioxidant activity and changed the phenolic profile of the extracts. Analysis by HPLC of supplemental blue-light plant extracts revealed a higher proportion of the major flavonoid quercetin 3-O-α-L-arabinopyranosyl (1→2) α-L-rhamnopyranoside, as well as the presence of a wide variety of other phenolic substances. These findings may explain the higher antioxidant activity observed for this extract. Blue light is proposed as a supplemental light source in the cultivation of K. pinnata, to improve its antioxidant activity.

Photodegradation of bisphenol A polycarbonate under blue light radiation and its effect on optical properties

In this investigation, the degradation mechanisms of Bisphenol A Polycarbonate (BPA–PC) plates under blue light radiation are studied. The BPA–PC plates are used both in light conversion carriers in LED modules and encapsulantes in LED packages. Optical degradation of the products is mainly due to the degradation of BPA–PC encapsulants under blue light radiation. In this study, BPA–PC plates are irradiated with blue light at elevated temperature of 140°C for a period up to 1920h. Optical and chemical properties of the photo-aged plates were studied using UV–Vis spectrophotometer, FTIR-ATR spectrometer, integrated sphere, and Lambda 950 spectrophotometer. The results show that increasing the exposure time leads to the discoloration, loss of optical properties, decrease of light transmission, decrease in the relative radiant power value, and increase in the yellowing index (YI) of BPA–PC plates. The results also show that there are two stages in the yellowing of polycarbonate plates. The first stage is the so-called induction period in which there is no major change in the value of YI and the rate of yellowing is very slow. This stage takes until 500h, followed by the second yellowing regime, where the yellowing is accelerated and the rate of yellowing is comparatively faster. Both photo-Fries and photo-oxidation products are identified as the mechanisms of photo-degradation, with photo-Fries predominating as ageing time increases.

Effect of Light Emitting Diode Radiation on Antioxidant Activity of Barley Leaf

Antioxidant activity of extracts of barley leaves cultivated by light emitting diode (LED) radiation such as red, far-red, blue, blue-red, green, yellow, and white light was investigated. After measuring length and weight of the leaves cultivated, barley leaves were extracted using 70% ethanol. The Hunter color value, total phenolic compounds, and 1,1-diphenyl-2-picrylhydrazyl (DPPH) and 2,2′-azinobis (3-ethylbenzothiazoline-6-sulfonic acid) diammonium salts (ABTS) radical-scavenging activities of extracts were determined. Lengths of samples cultivated by red and green light radiation were 13.7 and 13.6 cm, respectively. Hunter L* values of samples cultivated by red, far-red, and UVA radiation were 65.29, 67.55, and 67.57, respectively. The content of total phenolic compounds of samples cultivated by blue light radiation was 1.62 mg/L of sample. The DPPH radical-scavenging activities of samples cultivated by blue, green, UVA, and white light radiation were 64.28, 48.92, 55.95, and 48.72%, respectively. The ABTS radical-scavenging activity of samples cultivated by blue light radiation scored higher compared with those of samples cultivated with other LED lights. Antioxidant activities of barley leaves showed different results depending on harvest time. Application of LED radiation during re-cultivation after the first harvest showed increasing tendency on antioxidant activity of barley leaves.

Effect of blue light radiation on curcumin-induced cell death of breast cancer cells

In the present study, we have successfully set up a novel blue light source with the power density of 9 mW/cm2 and the wavelength of 435.8 nm and then the novel light source was used to investigate the effect of light radiation on curcumin-induced cell death. The cytotoxicity was investigated 24 h after the treatment of curcumin and blue light radiation together using MTT reduction assay. Nuclear chromatin was observed using a fluorescent microscopy with Hoechst33258 staining. The results showed blue light radiation could significantly enhance the cytotoxicity of curcumin on the MCF-7 cells and apoptosis induction. These findings demonstrated that blue light radiation could enhance curcumin-induced cell death of breast cancer cells, suggesting light radiation may be an efficient enhancer of curcumin in the management of breast cancer.