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• RB LED promoted the number of shoots and leaves of in vitro Kaempferia parviflora plants, while red LED improved the length of the shoots,. • The production of photosynthetic pigments was increased under white, blue and RGB light,. • Red LED induced the accumulation of carbohydrates, while RB LED increased the production of proteins, with the highest antioxidant activity of Kaempferia parviflora observed under white LED. Black ginger (Kaempferia parviflora) is a popular plant in Thailand and Malaysia that is valued for its medicinal properties, especially its aphrodisiac qualities. Light-emitting diodes (LEDs) have successfully induced regeneration and various growth responses of black ginger plants in vitro. This study aims to investigate LED-induced photomorphogenesis of black ginger and to evaluate its physiology state. Shoot explants were grown in vitro under irradiation of white (400–750 nm), red (660 nm), blue (460 nm), RB (440 nm; 660 nm), and RGB (400 – 660 nm) to determine the vegetative responses of black ginger plants under the influence of light quality after six weeks. Biochemical analyses such as photosynthetic pigments, total carbohydrate content, protein estimation and free radical scavenging activity were also performed. The highest percentage of shoots was obtained at 96.67 % under blue light, but the maximum number of shoots and leaves were produced under RB LED with 3.21 ± 0.25 and 3.92 ± 0.28, respectively. The red light significantly promoted shoot length with an average length of 3.07 ± 0.21 cm. Rooting was spontaneously induced in all light treatments, with the highest number of roots recorded under RGB lighting at 11.80 ± 1.30. In general, RGB light significantly promoted the synthesis of photosynthetic pigments such as total chlorophyll content, carotenoids and porphyrins with 0.68 ± 0.02 µg/ml, 248.67 ± 3.38 µg/g and 3.94 ± 0.11 µg/g, respectively. The highest carbohydrate and protein contents were obtained with red and RB lights at 80.07 ± 9.15 mg/g and 309.33 ± 0.58 µg/ml, respectively. The control plants with white LED light showed the highest DPPH radical scavenging activity 94.34 ± 0.04%. Our results indicate that different light qualities induce photomorphogenesis of in vitro black ginger plants. The spectral combination with green light significantly improved the morphology and physiology of the plants. Therefore, the green spectrum should be considered as an important light source to promote plant growth in controlled environment agriculture. [ABSTRACT FROM AUTHOR]

Tetraphenylethene and its derivatives have become increasingly attractive as aggregation-induced emission luminogens (AIEgens) due to their superior luminescence efficiency and low contamination. In this paper, a tetraphenylethene derivative (4,4′,4″,4‴-(ethene-1,1,2,2-tetrayltetrakis-(benzene-4,1-diyl)) tetrakis-(1-allylpyridin-1-ium), TPE-1) synthesized with unique fluorescent properties, was integrated into a fluorescent nanocomposite with polyoxometalate (Na9[Eu-(W5O18)2]·32H2O, EuW10) in an aqueous solution using an ionic self-assembly strategy. The TPE-1/EuW10 nanocomposite is composed of spherical particles with a uniform particle size of about 40 nm, and compared with the original material TPE-1, its quantum yield grows from 18.27% to 39.88%. The experimental results suggest that the negatively charged groups of EuW10 may interact electrostatically with the positively charged nitrogen atoms of TPE-1, leading to the aggregation of TPE-1 molecules to enhance the fluorescence. Mixing the TPE-1/EuW10 nanocomposite with commercially available blue and green phosphor can yield a white emitting phosphor with the CIE coordinate of (0.33, 0.34), which is close to the standard white light. This ionic self-assembly strategy of TPE-1 and EuW10 with easy preparation is of great significance for the simple construction of an AIE light-emitting system applicable to optoelectronic devices. [ABSTRACT FROM AUTHOR]

ABSTRACT Light is a determining factor in plant morphophysiology, as it influences the growth and development of agricultural crops. Thus, the objective was to investigate the effects of light sources on the growth and development of “biquinho” pepper cultivars. The experiment was performed in two stages (Exp1 and Exp2), evaluating two cultivars (BRS Moema; Airetama biquinho) in five light sources (white LEDs, red LEDs, blue LEDs, red/blue LEDs, and fluorescent lamps). In Exp1 the plants were kept in a controlled condition, with a completely randomized design, in a 2x5 factorial scheme (cultivars x light sources) until 76 days after emergence (DAE), in which growth variables and photosynthetic pigments were evaluated. In Exp2, the plants were removed from the above conditions and transplanted in pots, being kept in greenhouse for more 76 DAE. At 152 DAE, the same variables as Exp1 were evaluated, as well as gain of shoot fresh and dry mass, and gain of root fresh and dry mass. In both experiments, growth variables were affected by cultivar and the light sources, however, the behavior did not follow the same trend for all variables, indicating that the light quality influences the growth of the crops, and impacting during greenhouse conditions.

Novel rare-earth (RE; e.g., europium (Eu3+), samarium (Sm3+), and praseodymium (Pr3+)) and transition metal (TM4+; e.g., manganese (Mn4+)) ion single-/co-doped double-perovskite Ca2InTaO6 (CITO) phosphors were prepared and investigated with respect to their crystal structure and photoluminescence (PL) properties. Among them, the CITO:Eu3+ phosphors were found to exhibit an ultra-high internal PL quantum yield (89.1%) and good thermal stability (78.7% at 423 K relative to the initial value at 303 K). As such, the corresponding packaged white light-emitting diode (LED) was able to display a remarkable color rendering index (CRI; = 91.51@10 mA). Besides, the potential in applications of anti-counterfeiting fields and a novel LED structure based on flexible phosphor-converted films was also studied. Moreover, due to their different thermal quenching, trivalent lanthanide (Ln3+)/Mn4+ co-doped CITO phosphors were designed for optical thermometry based on the luminescence intensity ratio (LIR) between different 4f transitions of various Ln3+ ions and 2Eg → 4A2g (Mn4+) transition. Particularly, the LIR between the 4G5/2 → 6H9/2 and 2Eg → 4A2g peaks of the CITO activated with 5 mol% Sm3+ and 0.3 mol% Mn4+ exhibited the most excellent relative sensitivity (Sr; = 3.80 %·K−1) with beneficial temperature uncertainty of 0.0648 K. Overall, these results are of significance to offer valuable databases for constructing multifunctional high-performance optical platforms using single-/co-doped double-perovskite tantalates.

Solar simulators are instruments used for controllable measurements of the properties of solar cells in indoor environments. The purpose of this paper is to examine the peculiarities of the photoresponses of CdTe/CdSeTe and microcrystalline Si solar cells and to reveal the pathways to reduction of spectrum mismatch effects when using light-emitting diode (LED)-based or hybrid LED and halogen lamp-based solar simulators of an A+-class spectrum with a small number of sources. While only four different LED types are needed to achieve an A+-class spectrum under updated IEC 60904-9:2020 standard requirements, as demonstrated by our results, additional ultraviolet LEDs are necessary to reduce the spectrum mismatch. For hybrid solar simulator configurations, the combination of cool white LED arrays and halogen emitters can serve as a main light source. Optimized for both solar cell types, hybrid simulators have a lower spectral deviation and better spectrum coverage compared to LED-only simulators with the same number of distinct source types. In addition, our results predict lower spectral mismatch errors for optimized simulators when compared with conventional Xe lamp-based simulators. [ABSTRACT FROM AUTHOR]

Micro-light-emitting diodes (micro-LEDs) with high modulation rates and low power consumption could attract growing attention as visible light communication (VLC) technology advances. The designed and fabricated semi-polar micro-LEDs have achieved high bandwidth at low current injection due to the reduced quantum-confined Stark effect (QCSE), which was significantly greater than that of typical c-plane at the same current injection. Semi-polar green micro-LEDs got a −3 dB bandwidth that surpasses 500 MHz and 1 GHz at low current densities of 43.8 A/cm2 and 120.6 A/cm2, while blue micro-LEDs exceed 500 MHz at low current densities of 76.6 A/cm2, respectively. Additionally, the free space VLC system has shown semi-polar blue and green micro-LED transmission data rates of 3.495 Gbps (433 A/cm2) and 3.483 Gbps (402 A/cm2) respectively. Semi-polar micro-LEDs, which can achieve low power consumption and high bandwidth, are anticipated to play a significant role in the development of energy-efficient VLC in the future.

In this work, we investigate the performance improvement of N-polar AlGaN-based deep ultraviolet light-emitting diodes (DUV LEDs) by the inversion of the hole injection layer from N-polar to Ga-polar. The influence of different inversion points on the performance and the energy band of DUV LED is systematically studied, and the principle of performance improvement of DUV LED is explained in detail through the analysis of the energy band. Furthermore, according to the simulation results and practical application, an appropriate inversion point is selected. Under the current of 120 mA, with polarity inversion of the hole injection layer, the light output power of the DUV LEDs increases from 21.34 mW to 29.71 mW, and the applied voltage reduces from 16.06 V to 9.63 V. The DUV LED with polarity inversion has a 132% increase in wall-plug efficiency (WPE) compared with the DUV LED which is totally along [000-1] direction. Therefore, polarity inversion is an effective way to achieve high-performance UV-LEDs.

Perovskite light‐emitting diodes (PeLEDs) are advancing because of their superior external quantum efficiencies (EQEs) and color purity. Still, additional work is needed for blue PeLEDs to achieve the same benchmarks as the other visible colors. This study demonstrates an extremely efficient blue PeLED with a 488 nm peak emission, a maximum luminance of 8600 cd m−2, and a maximum EQE of 12.2% by incorporating the double‐sided ethane‐1,2‐diammonium bromide (EDBr2) ligand salt along with the long‐chain ligand methylphenylammonium chloride (MeCl). The EDBr2 successfully improves the interaction between 2D perovskite layers by reducing the weak van der Waals interaction and creating a Dion–Jacobson (DJ) structure. Whereas the pristine sample (without EDBr2) is inhibited by small stacking number (n) 2D phases with nonradiative recombination regions that diminish the PeLED performance, adding EDBr2 successfully enables better energy transfer from small n phases to larger n phases. As evidenced by photoluminescence (PL), scanning electron microscopy (SEM), and atomic force microscopy (AFM) characterization, EDBr2 improves the morphology by reduction of pinholes and passivation of defects, subsequently improving the efficiencies and operational lifetimes of quasi‐2D blue PeLEDs. [ABSTRACT FROM AUTHOR]

• The establishment of micropropagation protocol for Cameron Highlands White Strawberry. • High multiplication rate in full-strength MS medium + 8 µM TDZ. • No damage to the cellular arrangement was observed on the treated in vitro plants in any of the light treatments using scanning electron microscopy (SEM). • Maximum acclimatization efficiency in hydroponic solution (100% survival rate). White strawberry is botanically a member of the Fragaria genus, which is a part of the Rosaceae family, which is primarily found in Japan, where it is a well-known premium fruit. Experiments were conducted to develop a micropropagation method for Cameron Highlands white strawberries (Fragaria x Ananassa). Freshly extracted achenes were surface sterilised with 30 and 40% Clorox®. Achenes germination was studied in vitro under various light spectra [cool white LED (17.0 μ mol/s), red LED (29.30 μ mol/s), blue LED (15.70 μ mol/s), red + blue LEDs (44.80 μ mol/s)] to study how light and different LED spectra affected shoot, root, and leaf growths of seedlings in the culture. Because both treatments have a 0% contamination rate and the same germination rate which is 78.77%, the 30% Clorox® treatment was chosen as the best surface sterilisation protocol for white strawberry achene germination. Scanning electron microscopy (SEM) studies of seedlings germinated under various light treatments demonstrated that no damage to the cellular arrangement was observed in any of the light treatments. However, the stomata of seedlings treated with blue LED were found to be damaged and exhibit uneven structures. Shoot multiplication in the culture was determined by testing various concentrations of 6- benzylaminopurine (BAP) and thidiazuron (TDZ) using shoot tips (0.5 to 0.8 cm) from the 5-leaf stage of the in vitro plants. The highest mean number (6.50 ± 1.05) of shoots differentiated on MS medium with 8 µM TDZ. The regenerated plantlets were rooted on MS medium with indole-3-butyric acid (IBA) and 1-Naphthaleneacetic acid (NAA) at 0 (control), 1, 2, 3, and 5 µM. Rooting (50%) was the highest success with 1 µM IBA. All the rooted plantlets were successfully acclimatized using hydroponics and field transfer. [ABSTRACT FROM AUTHOR]

The aims of this study were to evaluate how different light qualities alter the physiological and biochemical characteristics, of Dendrobium nobile. To determine the best light quality for in vitro culture of D. nobiles plantlets, the relationships between growth, antioxidant capacity, nutrient and chlorophyll contents, and chlorophyll fluorescence were evaluated. Growth under five Light-Emitting Diode (LED) light treatments, red light (R), blue light (B), 8R:2B, 7R:3B, and 5R:5B, were compared to white fluorescent light. The 8R:2B and 7R:3B mixtures of red and blue LED light were beneficial to root number, root length, root activity, fresh and dry weight, antioxidant ability, and chlorophyll content and fluorescence. The carotenoid content and ΦPSII significantly correlated with root length, while NPQ significantly correlated with root activity, length of root, fresh and dry weight and SSC. qP was significantly correlated with fresh and dry weight and the activities of FPC, POD and APX. Comprehensive scores, derived from Principal Component Analysis (PCA), of the plants grown under the 8R:2B and 7R:3B light treatments were similar to each other, while significantly higher than plants grown under the other light treatments. In conclusion, D. nobile seedlings grown under 8R:2B and 7R:3B exhibited suitable plant architecture for the controlled environment. [ABSTRACT FROM AUTHOR]

Light is a determining factor in plant morphophysiology, as it influences the growth and development of agricultural crops. Thus, the objective was to investigate the effects of light sources on the growth and development of "biquinho" pepper cultivars. The experiment was performed in two stages (Exp1 and Exp2), evaluating two cultivars (BRS Moema;Airetama biquinho) in five light sources (white LEDs, red LEDs, blue LEDs, red/blue LEDs, and fluorescent lamps). In Exp1 theplants were kept in a controlled condition, with a completely randomized design, in a 2x5 factorial scheme (cultivars x light sources) until 76 days after emergence (DAE), in which growth variables and photosynthetic pigments were evaluated. In Exp2, the plants were removed from the above conditions and transplanted in pots, being kept in greenhouse for more76 DAE. At 152 DAE, the same variables as Exp1 were evaluated, as well as gain of shoot fresh and dry mass, and gain of root fresh and dry mass. In both experiments, growth variables were affected by cultivar and the light sources, however, the behavior did not follow the same trend for all variables, indicating that the light quality influences the growthof the crops, and impacting during greenhouse conditions. [ABSTRACT FROM AUTHOR]

Microgreens are environmentally friendly and have health benefits in addition to their basic nutritional contents. The effect of white (W), white–blue (W + B), and white–red (W + R) light on the bioactive compounds, nutrient composition, and antioxidant potential of red and white cabbage microgreens were investigated using light-emitting diodes (LEDs). The results showed that protein, fat, ash, chlorophylls, and carotenoids were the highest in microgreens under W light, while phenolic compounds were highest in microgreens under W + B light. Supplementation with white light, as well as red or blue light, resulted in higher levels of sugars and total fiber in both white and red microgreens. Twenty-six and thirty-three phenolic compounds were identified in white and red cabbage microgreens, respectively. The identified phenolics belonged to three classes, including phenolic acids, flavonols, and anthocyanins. The antioxidant potential of both cabbage microgreens was determined by four methods (ABTS, DPPH, ORAC, and FRAP). It was found that the highest antioxidant potential was observed in microgreens grown under the W + B light combination. On the other hand, the W + R light combination increased the content of β-sitosterol and campesterol. The results may be helpful in the selection of the type of LED lighting that determines the high nutritional and health-promoting potential of white and red cabbage microgreens. [ABSTRACT FROM AUTHOR]

Pinus pseudostrobus Lindl. is a species endemic to Mexico and is widely used in reforestation programmes, as it is highly adapted to poor, shallow, limestone soils and has high commercial importance. However, it is necessary to preserve this genetic material since it is in trouble due to high rates of deforestation, land use change, and forest fires, so it is necessary to have effective strategies to obtain good quality seedlings. Due to the properties of LED (light emitting diode) lamps used for illumination in the production of in vitro plants, the effects of two different lighting systems (LED and fluorescent) on an in vitro culture were analysed for the morphological characteristics of the growth and photosynthetic pigment content in P. pseudostrobus seedlings. The length and root size of the seedlings were affected by the type of illumination, where a red LED light was the most effective at 30 days of evaluation. However, a blue LED light was equally effective as a red LED light at 60 days of seedling development. On the other hand, the fluorescent light was better in terms of the number of needles in the first stage, but we found the blue LED light to be better in the second stage. For the photosynthetic pigment content, the highest values were found with the blue LED light. The results showed that the LED lighting system favours the growth, development, and photosynthetic pigment content of the species under study.

• The highest Fv/Fo was obtained in R LED light under foliar glycine exposure to 80 mg.l−1. • Glycine-exposed plants under light treatments exhibited higher fluorescence yield at F0, Fm, and Fv compared to normal light conditions. • Plants exposed to control light under foliar glycine treatment at 80 mg. l−1 resulted in higher Vj and Vi than those of different lighting conditions. • Under B LED light conditions, ∆b*, ∆E*, ∆C* and ∆h* were increased in comparison with normal light conditions. • Plants under B LED light upon exposure to glycine treatment at 40 mg. l−1 revealed the highest stomatal conductance. Light quality plays an important role in all growth and development stages particularly in photosynthesis properties of plant species. The light-emitting diodes (LEDs) present maximum efficiency on biological processes among artificial lighting systems. The current study was aimed to investigate different LED light color (Blue, Red and White) and glycine concentrations (0, 40 and 80 mg L−1) on photosynthetic efficiency of black henbane (Hyoscyamus niger L.) plant in a completely randomized design (CRD) with three to five replications. Results showed that the maxiumu quantum yield of PSII (0.839) was obtained in R LED light spectrum exposed plants upon glycine treatment at 80 mg. L−1, howevre, the lowest Fv/Fm (0.659) was detected in plants subjected to W LED spectrum. The highest Fv/Fo was obtained in plants grown under R LED lighting with glycine treatment at 80 mg. L−1; however, C (normal light conditions) showed the lowest Fv/Fo among the light treatments. Under B LED light conditions, ∆b*, ∆E*, ∆C* and ∆h* were increased in comparison with normal light condition. Results showed that changing trends of these traits were consistent with those of chlorophylls and carotenoids contents under different LED-based light regimes. Moreover, compared with chlorophylls content under B LED light spectrum with glycine, the carotenoids content under W LED light source was found to be a dominant pigment in black henbane plants. [ABSTRACT FROM AUTHOR]

Light-emitting diodes (LEDs) are commercially used as a light source to improve plant growth and antioxidants accumulation. Growth and antioxidant system in Chinese kale microgreens illuminated with blue, red and white LEDs and sunlight, as a control, with the same duration of illumination were investigated. The red LED with low light intensity significantly enhanced hypocotyl length and fresh weight of microgreens, while blue and white LEDs and sunlight showed fairly comparable effects. The synergistic effect of blue, green and red LEDs, as white LED was the most effective in enhancing the accumulation of secondary metabolites, namely, total glucosinolates, phenolic compounds and total ascorbic acid. Microgreens grown with blue and white LEDs showed higher DPPH (1,1-diphenyl-1-picrylhydrazyl) radical scavenging activity and ferric reducing antioxidant power, whereas ABTS [2,2'-Azino-bis (3-ethylbenzothiazoline-6-sulfonic acid)] radical cation (ABTS) fared better under sunlight and blue LEDs. Overall, microgreens treated with red LED significantly reduced H2O2 and lipid peroxidation by only secondary metabolites. While blue and white LEDs treated samples utilised secondary metabolites, as well as, catalase and ascorbate peroxidase when compared to less effective superoxide dismutase in the control samples. The results suggest that light wavelength was a majority factor in enhancement antioxidant accumulation. [ABSTRACT FROM AUTHOR]

Novel near-infrared (NIR) phosphors are in demand for light-emitting diode (LED) devices to extend their suitability for new applications and, in turn, support the sustainable and healthy development of the LED industry. The Cr3+ has been used as an activator in the development of new NIR phosphors. However, one main obstacle for the Cr3+-activated phosphors is the low luminescence efficiency due to the spin-forbidden d-d transition of Cr3+. The rare-earth (RE) huntite minerals that crystallize in the form of REM3(BO3)4 (M = Al, Sc, Cr, Fe, Ga) have a large family of members, including the rare-earth scandium borates of RESc3(BO3)4. Interestingly, in our research, we found that the luminescence efficiency of Cr3+ in the CeSc3(BO3)4 host, whose quantum yield was measured at 56%, is several times higher than that in GdSc3(BO3)4, TbSc3(BO3)4, and LuSc3(BO3)4 hosts. Hereby, the energy conversion and transfer in the luminescence of CeSc3(BO3)4:Cr3+ phosphor were examined. The Stokes shift of electron energy conversion within the Cr3+ 4T2g level for the emission at 818 nm and excitation at 625 nm in CeSc3(BO3)4 host was evaluated to be 3775.1 cm−1, and the super-large splitting energy of the 2F5/2 and 2F72 sub-states of the Ce3+ 4f1 state, about 3000 cm−1, was found in CeSc3(BO3)4 host. The typical electronic thermal vibration peaks were observed in the excitation spectra of CeSc3(BO3)4:Cr3+. On this basis, the smallest phonon energy, around 347.7 cm−1, of the CeSc3(BO3)4 host was estimated. Finally, the energy transfer that is responsible for the far higher photoluminescence of Cr3+ in CeSc3(BO3)4 than in other hosts was proven through the way of Ce3+ emission and Cr3+ reabsorption. [ABSTRACT FROM AUTHOR]

This work reports an optomechanical, electronic system consisting of LEDs emitting light in the near-infrared region. The 147 light-emitting diodes were distributed in a semi-spherical dome so that each focused light upon the center of the radius. The LEDs received electrical polarization so that the optical power of each provided 16 ± 0.36 mW for a total of 2.4 W. The developed system allows multifunctional applications in phototherapy, making it possible to perform this clinical technique for the treatment of skin lesions and contusions at the musculoskeletal level. The geometry of the developed system also allows the use of phototherapy in the treatment of neurological pathologies. In terms of instrumentation, the three-dimensional light intensity distribution and the thermographic images were obtained using three working distances from the system to the target. Three-dimensional light intensity distributions were obtained considering each working distance. These were inserted in the thermographic images as indications of the emitted temperature distributions. This work verified that the optomechanical and electronic system developed with LEDs may be used for multiple applications in phototherapy. [ABSTRACT FROM AUTHOR]

Alternative therapeutic approaches to mental, neurological and physiological diseases present cures and treatments based on light-emitting electromagnetic radiation. Low-level laser therapy was introduced half a century ago in various medical fields. Nowadays, in the search for cheaper and less absorbed light doses with which the same therapeutic results can be achieved, light-emitting diodes enter boldly into medical practice. Light-emitting diodes have gained popularity though there is no sufficient evidence on the response of various neuromodulators to electromagnetic radiation at a molecular level. This study was intended to clarify the effect of light-emitting diode red and laser near-infrared light on smooth muscles' reactivity to 5-hydroxytryptamine. The smooth muscle tissues were in vitro irradiated in a self-designed system named wet organ bath, and the specific mechanograms were depicted. Our results demonstrate that in both irradiation cases (light-emitting diode red or laser near-infrared light), smooth muscle contractility is potentiated, which is mediated by the activation of 5-hydroxytryptamine. [ABSTRACT FROM AUTHOR]

Traditional photocatalytic oxidation of nitrogen oxide (NO) may cause the more toxic NO2 generation after longtime reaction, and even the ideal final production nitrate may also inevitably cause the poisoning of photocatalysts. Thus, utilizing photocatalytic reduction to remove NO into N2 should be considered more practical but is still challenging currently. Herein, a novel S‐scheme β‐Bi2O3/Bi/g‐C3N4 heterojunction photocatalyst is developed via a one‐step in situ thermal reduction method. The photocatalytic degradation efficiency over this S‐scheme photocatalyst exhibits around 88.7% degradation rate for NO with little NO2 generation under light‐emitting diode light irradiation, which is significantly higher than that of the pristine g‐C3N4 (60%). Interestingly, both reduction of NO into N2 and oxidation of NO into NO3− exist synchronously in the system. The increased degradation efficiency and the efficient reduction pathway occurring should be ascribed to the enhanced generation, separation, and transfer of the photogenerated carriers through the Bi‐bridge S‐scheme heterojunction. This study has provided a new route for regulating the photocatalytic reaction pathway for NO removal through a simple synthesis method.

Solar simulators are instruments used for controllable measurements of the properties of solar cells in indoor environments. The purpose of this paper is to examine the peculiarities of the photoresponses of CdTe/CdSeTe and microcrystalline Si solar cells and to reveal the pathways to reduction of spectrum mismatch effects when using light-emitting diode (LED)-based or hybrid LED and halogen lamp-based solar simulators of an A+-class spectrum with a small number of sources. While only four different LED types are needed to achieve an A+-class spectrum under updated IEC 60904-9:2020 standard requirements, as demonstrated by our results, additional ultraviolet LEDs are necessary to reduce the spectrum mismatch. For hybrid solar simulator configurations, the combination of cool white LED arrays and halogen emitters can serve as a main light source. Optimized for both solar cell types, hybrid simulators have a lower spectral deviation and better spectrum coverage compared to LED-only simulators with the same number of distinct source types. In addition, our results predict lower spectral mismatch errors for optimized simulators when compared with conventional Xe lamp-based simulators.

This study was conducted to investigate the inhibitory effects of light-emitting diodes (LEDs) on exosome biogenesis and angiogenesis capacity in Ishikawa endometrial cancer cells. To this end, cells were exposed to different energy densities (fluences) of 4, 8, 16, 32, and 64 J/cm2 for 5 days (once every 24 h), and cell viability was determined using an MTT assay. Based on data from the MTT panel, cells were exposed to 4 and 16 J/cm2 for subsequent analyses. Exosome biogenesis was also monitored via monitoring the expression of CD63, ALIX, and Rab27a and b. The size and morphology of exosomes in the supernatant were measured using scanning electron microscopy (SEM), and dynamic light scattering (DLS). Using Transwell insert, the migration capacity of these cells was studied. The angiogenic effects of irradiated Ishikawa cell secretome at different fluences were monitored on human endothelial cells using in vitro tubulogenesis. Results indicated LED can reduce the viability of Ishikawa cells in a dose-dependent manner. According to our data, 4 and 64 J/cm2 groups exhibited minimum and maximum cytotoxic effects compared to the control cells. Data revealed a close proportional relationship between the power of laser and exosome average size compared to the non-treated control cells (p < 0.05). Real-time PCR analysis showed the suppression of Rab27b and up-regulation of Rab27a in irradiated cells exposed to 4 and 16 J/cm2 (p < 0.05). These effects were evident in the 16 J/cm2 group. Likewise, LED can inhibit the migration of Ishikawa cells in a dose-dependent manner (p < 0.05). Tubulogenesis activity of endothelial cells was suppressed after incubation with the secretome of irradiated Ishikawa cells (p < 0.05). These data showed tumoricidal properties of LED irradiation on human adenocarcinoma Ishikawa cells via the inhibition of exosome biogenesis and suppression of angiogenesis capacity. [ABSTRACT FROM AUTHOR]

Caper seeds present difficulties in their germination, which has been studied by several research teams. It is known that light can release dormancy in some seeds, but its effect on caper seed germination has not yet been deeply studied. The main aim of this study was to analyze the response of caper seeds germination to light exposure. The study analyzed the germination response of seeds to lighting with different wavelengths (white, red, blue, red + blue and darkness) and to the He-Ne laser light, using both dry seeds and seeds that had been previously soaked in water. Overall, it could be stated that caper seeds are insensitive to light during the germination process. Thus, germination could be carried out in lightness or darkness, so germination in nurseries could be carried out in the darkness, leading to substantial energy savings. Caper seed irradiation with a He-Ne laser during short exposure times improved the germination percentage for the seeds previously soaked in water, germinating all viable seeds. However, applying a solution of gibberellic acid was always required in all the cases studied. [ABSTRACT FROM AUTHOR]

A colloidal quantum dot (CQD) package with convex-surface solder reflectors of various diameters exhibited more favorable thermal characteristics and optical reliability performance than did the traditional in-chip package. The results indicated that solder balls provided a direct cooling path on the top of the LED chip to accelerate heat dissipation, and blue photons were reflected by the ball surfaces to enhance their recycling. The areal temperature results decreased from 88.4 °C (in-chip) to < 70 °C (solder ball) at a current of 180 mA. By contrast, continuous aging tests indicated that the devices with metal structures exhibited lifetimes four to six times longer than that of the in-chip device. The metal embedded structures not only provided a relatively low operating temperature but also extended the operating time of the packaged CQDs. This study pushes the envelope in the endeavor to integrate high-thermal-conductivity components into quantum dot photonic devices. [ABSTRACT FROM AUTHOR]

The recent progress in III-nitride tunnel junction (TJ) contacts for optoelectronic devices is summarized in this review paper. Due to the rapid developments of various III-nitride based optoelectronic devices for different emerging applications, TJs are of interest for these devices to achieve more efficient device performance. This review paper first briefly describes the working principles of TJs and the advantages of employing TJs in optoelectronic devices. The significant advancements in III-nitride TJs realized by metalorganic chemical vapor deposition (MOCVD) and molecular beam epitaxy (MBE) are addressed, as well as their TJ device performances. Lastly, the critical challenges for employing III-nitride TJs in wide bandgap ultraviolet (UV) light emitters are discussed for future investigations. [ABSTRACT FROM AUTHOR]

Pinus pseudostrobus Lindl. is a species endemic to Mexico and is widely used in reforestation programmes, as it is highly adapted to poor, shallow, limestone soils and has high commercial importance. However, it is necessary to preserve this genetic material since it is in trouble due to high rates of deforestation, land use change, and forest fires, so it is necessary to have effective strategies to obtain good quality seedlings. Due to the properties of LED (light emitting diode) lamps used for illumination in the production of in vitro plants, the effects of two different lighting systems (LED and fluorescent) on an in vitro culture were analysed for the morphological characteristics of the growth and photosynthetic pigment content in P. pseudostrobus seedlings. The length and root size of the seedlings were affected by the type of illumination, where a red LED light was the most effective at 30 days of evaluation. However, a blue LED light was equally effective as a red LED light at 60 days of seedling development. On the other hand, the fluorescent light was better in terms of the number of needles in the first stage, but we found the blue LED light to be better in the second stage. For the photosynthetic pigment content, the highest values were found with the blue LED light. The results showed that the LED lighting system favours the growth, development, and photosynthetic pigment content of the species under study. [ABSTRACT FROM AUTHOR]

Abstract Background Nowadays, light-emitting diodes (LEDs) as a new lighting technology, have been emerged as an alternative source of light for plants due to their wavelength specificity, the narrow width of their bands, small size, solid structure, long lifetime, and low heat generation. Here we investigated the effect of different LED light sources on the essential oil components and antioxidant activity of Melissa officinalis. Two genotypes of lemon balm (Ilam and Isfahan) were subjected to four artificial light treatments, including white, red, blue, red + blue LEDs, and greenhouse light as natural lighting. Results The LED lights significantly increased shoot fresh and dry weights and leaf number in the two genotypes as compared to greenhouse condition. The results showed that the content and composition of essential oil in the two genotypes were variable under different light treatments and the total amount of compounds in the Ilam genotype was higher than the other genotype. The results of analysis of the essential oil by GC/MS indicated that the highest amount of monoterpenes in the genotypes was related to citronellal under red + blue LED lamps (15.3 and 17.2% in Ilam and Isfahan genotypes, respectively) but blue, white, and greenhouse condition had the most effect on sesquiterpenes content in both genotypes. The results showed that the observed variation between the two genotypes in the essentials oil composition was related to the relative percentage of the constituents and not to the appearance or lack of a specific component. Red + blue lighting also provided the highest radical scavenging activity in both genotypes (80.77 and 82.09% for Ilam and Isfahan genotypes, respectively). Based on principal component analyses (PCA), three main groups were identified regarding genotypes and all light treatments. Conclusions Overall, results indicated that the essentials oil composition of two genotypes of lemon balm was affected both qualitatively and quantitatively by different LED light sources; hence, LED lights might be used to improve monoterpenes, sesquiterpenes, and antioxidant activity in the selected genotypes.

Light-emitting-diodes (LEDs) are a lighting source useful for the precise evaluation of light quality effect on biological systems. Despite the importance of light spectra on the regeneration of land plant protoplasts ("naked cells"), this factor has not been tested yet on protoplasts from multicellular algae. This study reports on the effects of pure primary colors (red, blue, and green), dichromatic (red plus blue, RB, 1: 2) and white LEDs on protoplast regeneration from male and female Undaria pinnatifida gametophytes. We also evaluated the effect of different light spectra on pigment composition (chlorophyll a, chlorophyll c, and fucoxanthine), and the light intensities under the best condition on the regeneration process. In the early stages, blue or RB LEDs increased the percentage of dividing female protoplasts, whereas red, blue, and RB LEDs enhanced that of dividing male protoplasts. In the later stages, RB LEDs showed a positive effect only on the percentage of multiple rhizoid-like protrusions (male gametophyte). They also increased the final area of both regenerated gametophytes. The LEDs did not affect pigment composition in female gametophytes. In male gametophytes, in contrast, they reduced chlorophyll c, while blue, RB, and green LEDs decreased fucoxanthin. Under RB LEDs, the optimal light intensity was 80 µmol photons m-2 s-1 for female gametophytes and 40 to 60 µmol photons m-2 s-1 for male gametophytes. Our results suggest that dichromatic LED illumination (red-blue) improves regeneration of U. pinnatifida gametophyte-isolated protoplasts. Thus, dichromatic LEDs might a suitable light source for enhancing protoplast regeneration in brown seaweeds. [ABSTRACT FROM AUTHOR]

A high-speed c-plane InGaN/GaN blue micro-scale light-emitting diodes (Micro-LEDs) with a pixel diameter of $60~\mu \text{m}$ , and a high −3 dB modulation bandwidth of 1.53 GHz at the current density of 5996 A/cm2 were demonstrated. The ultra-thin quantum well (QW) structure with InGaN layer of 1 nm was designed, and optimized variable temperature growth processes were adopted to increase In incorporation and localization effect in the quantum wells, which greatly reduce the polarization field and increase the overlap of electron-hole wave functions. The differential carrier lifetime was effectively shortened, increasing the modulation bandwidth of the Micro-LED. And a data rate of 5.27 Gbps with a bit error rate (BER) of $3.1\times 10^{-{3}}$ was demonstrated with orthogonal frequency-division multiplexing (OFDM) signal for a 1 m free space real-time visible light communication (VLC) based on such high-speed micro-LED. Promising results in this work may support a great development of high-speed VLC applications. [ABSTRACT FROM AUTHOR]

Light quality has been reported to influence the phytochemical profile of broccoli sprouts/microgreens; however, few studies have researched the influence on mature broccoli. This is the first study to investigate how exposing a mature glasshouse grown vegetable brassica, Tenderstem® broccoli, to different light wavelengths before harvest influences the phytochemical content. Sixty broccoli plants were grown in a controlled environment glasshouse under ambient light until axial meristems reached >1 cm diameter, whereupon a third were placed under either green/red/far-red LED, blue LED, or remained in the original compartment. Primary and secondary spears were harvested after one and three weeks, respectively. Plant morphology, glucosinolate, carotenoid, tocopherol, and total polyphenol content were determined for each sample. Exposure to green/red/far-red light increased the total polyphenol content by up to 13% and maintained a comparable total glucosinolate content to the control. Blue light increased three of the four indole glucosinolates studied. The effect of light treatments on carotenoid and tocopherol content was inconclusive due to inconsistencies between trials, indicating that they are more sensitive to other environmental factors. These results have shown that by carefully selecting the wavelength, the nutritional content of mature broccoli prior to harvest could be manipulated according to demand. [ABSTRACT FROM AUTHOR]

In this work, we numerically investigate the N-polar AlGaN-based deep ultraviolet light-emitting diodes (DUV LEDs) over the Ga-polar DUV LEDs. The light output power has increased from 7.1 mW of Ga-polar DUV LED to 18.8 mW of N-polar DUV LED at 60 mA, and the wall-plug efficiency (WPE) of N-polar DUV LED is boosted by 104% at 60 mA with the same structure of Ga-polar conventional DUV LED. Furthermore, the higher operation voltage of N-polar DUV LED induced by the large energy difference between the p-type interlayer and the p-GaN hole supplier is noted. To reduce the operation voltage of N-polar DUV LED, the structure with a staircase-like p-type interlayer is proposed. The incorporation of staircase-like aluminum composition p-type interlayer mitigates the large potential barrier for holes injection, and the operation voltage is comparable to the Ga-polar DUV LED. The reduced operation voltage further promotes the WPE of N-polar DUV LEDs. Thus, combined with the promoted electron blocking ability and the mitigated potential barrier for holes of N-polar DUV LED, the greatly enhanced WPE is as high as 4.9% at 60 mA, which is 2.88 times higher than the Ga-polar DUV LED.

Die-bonding materials are essential packaging materials for high-power light-emitting diodes (LEDs), which affects their heat dissipation and reliability. In this work, a die-bonding structure with high strength and low thermal resistance was proposed for high-power LEDs. A Cu-foam/Sn composite preform was prepared as the die-bonding material in this die-bonding structure. The composite preform is composed of high-melting-point Cu skeleton and low-melting-point Sn. The Cu-skeleton structure accelerates the bonding process and forms intermetallic compounds (IMCs) with high remelting point. Consequently, the die-bonding structure displays robust joints from the transient-liquid-phase (TLP) interconnection layer and high thermal conductivity from the Cu skeleton. The effects of bonding temperature on the mechanical and thermal properties of LEDs were investigated. After bonded with the Cu-foam/Sn composite preform, the LED achieves a low thermal resistance of 6.75 K/W, a low junction temperature change of 6.5 °C, and a high shear strength of 37.8 MPa. Moreover, the proposed die-bonding structure has a lower thermal resistance and higher light output power, which are 27.2% lower and 7.2% higher than the traditional die-bonding structure, respectively. [ABSTRACT FROM AUTHOR]

Controlled environment (CE) food crop production has existed in the United States for many years, but recent improvements in technology and increasing production warranted a closer examination of the industry. Therefore, our objectives were to characterize historical trends in CE production, understand the current state of the U.S. hydroponics industry, and use historical and current trends to inform future perspectives. In the 1800s, CE food production emerged and increased in popularity until 1929. After 1929, when adjusted for inflation (AFI), CE food production stagnated and decreased until 1988. From 1988 to 2014, the wholesale value of CE food production increased from $64.2 million to $796.7 million AFI. With the recent increase in demand for locally grown food spurring an increase in CE production, both growers and researchers have been interested in using hydroponic CE technologies to improve production and quality. Therefore, we surveyed U.S. hydroponic food crop producers to identify current hydroponic production technology adoption and potential areas for research needs. Producers cited a wide range of technology utilization; more than half employed solely hydroponic production techniques, 56% monitored light intensity, and more than 80% monitored air temperature and nutrient solution pH and electrical conductivity. Additionally, the growing environments varied from greenhouses (64%), indoors in multilayer (31%) or single-layer (7%) facilities, to hoop houses or high tunnels (29%). Overall, producers reported managing the growing environment to improve crop flavor and the development of production strategies as the most beneficial research areas, with 90% stating their customers would pay more for crops with increased flavor. Lastly, taking historical data and current practices into account, perspectives on future hydroponic CE production are discussed. These include the importance of research on multiple environmental parameters instead of single parameters in isolation and the emphasis on not only increasing productivity but improving crop quality including flavor, sensory attributes, and postharvest longevity.

Microgreens are environmentally friendly and have health benefits in addition to their basic nutritional contents. The effect of white (W), white–blue (W + B), and white–red (W + R) light on the bioactive compounds, nutrient composition, and antioxidant potential of red and white cabbage microgreens were investigated using light-emitting diodes (LEDs). The results showed that protein, fat, ash, chlorophylls, and carotenoids were the highest in microgreens under W light, while phenolic compounds were highest in microgreens under W + B light. Supplementation with white light, as well as red or blue light, resulted in higher levels of sugars and total fiber in both white and red microgreens. Twenty-six and thirty-three phenolic compounds were identified in white and red cabbage microgreens, respectively. The identified phenolics belonged to three classes, including phenolic acids, flavonols, and anthocyanins. The antioxidant potential of both cabbage microgreens was determined by four methods (ABTS, DPPH, ORAC, and FRAP). It was found that the highest antioxidant potential was observed in microgreens grown under the W + B light combination. On the other hand, the W + R light combination increased the content of β-sitosterol and campesterol. The results may be helpful in the selection of the type of LED lighting that determines the high nutritional and health-promoting potential of white and red cabbage microgreens.

It has recently been proposed that back‐contacted III–V light‐emitting diodes (LEDs) could offer improved current spreading as compared to conventional mesa or double side contacted structures. This has inspired also experimental efforts to realize such structures, but fabrication methods for them have not yet been fully established. Herein, the use of unintentionally doped and partially carrier‐selective contacts (SC) is studied to realize back‐contacted indium gallium nitride (InGaN) LEDs. The sharp electroluminescence peak at 439 nm from the multiquantum well stack demonstrates that the approach allows fabricating back‐contacted InGaN LEDs without intentionally doped n‐GaN layers and without inflicting damage in the active region, often observed in alternative approaches relying on lateral doping and the use of high energy particles during fabrication. The samples are fabricated on a finger configuration with several finger widths between 1 and 20 μm. It is observed that the emission spreads most uniformly throughout the structure for fingers with the width of 5 μm. As shown by the simulations, with improved contact resistances, the structures reported herein could enable fabricating back‐contacted LEDs with unity injection efficiency and improved current spreading, offering a path toward large‐area LEDs without contact shading even in materials where n‐doping is elusive. [ABSTRACT FROM AUTHOR]

An electrothermal LED model for the design and simulation of light-emitting diode (LED) drivers based on the concept of the equivalent resistance is proposed in this article. The main contribution of this work is the integration of the temperature variables as the encapsulation temperature, heatsink temperature, and the ambient temperature in an electrical model based on the equivalent resistance of power LEDs. Therefore, an improved model is achieved by including these temperatures. This is because the LED temperatures are critical variables in the LED performance that could reduce the useful life of the LEDs or may even destroy them. Therefore, these temperatures must be considered in the design of LED drivers. The “equivalent resistance” concept has been previously used in the electrical modeling of power LEDs without considering the temperature variables, and this model was used to achieve fast simulations in LED-driver systems. The proposed model is oriented to the area of electronic engineering and it is recommended for the design and simulation of LED-converter systems. Experimental and simulation results are obtained that demonstrate the performance of the proposed model. [ABSTRACT FROM AUTHOR]

Abstract The aim of this work was to evaluate the effect of five light qualities [fluorescent lamps (FL); white (WL), red (RL), blue (BL), or red/blue LEDs (RBL)] and two types of flask sealing (with or without porous membranes) in the in vitro germination and growth of two Capsicum frutescens cultivars (Espaguetinho and Cayenne). For this, two seeds were inoculated per flask (350 mL) containing 50 mL of MS medium with 100 mg L-1 myo-inositol, 30 g L-1 sucrose, 6.0 g L-1 agar, and pH 5.8 ± 0.1. The plants were kept under culture room conditions (16-h photoperiod, 25 ± 2°C and irradiance of 40 μmol m-2 s-1). The experiment was arranged in CRD, 2x5x2 factorial scheme (Cultivar X Light qualities X Sealing type). At 42 days, the following traits were evaluated: percentage of germination; root and shoot length; number of green leaves, senescent leaves and nodal segments; and fresh and dry weight. Plants grown under RL and BRL, showed greater number of green leaves, and longer shoots and roots. The use of porous membranes remarkably reduced the number of senescent leaves. Thus, the use of porous membranes, RL and BRL are recommended since they improve growth and development of pepper in vitro.

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A white light-emitting diode (WLED) with chip-scale packaging (CSP) has wide applications due to its high power density, small size, and high process integration. The phosphor converter of the CSP WLED needs to endure huge heat shock from LED chips and phosphor conversion. In this work, we proposed a phosphor-in-glass (PiG)-based CSP for high-power WLEDs. A wafer PiG was prepared by printing and sintering a phosphor glass film on a glass plate and then cut into a chip-scale PiG for the fabrication of PiG-CSP WLEDs. The optical performances of PiG-CSP WLEDs were optimized by adjusting the film thickness of PiG. Consequently, the PiG-CSP WLED emits a cool white light with optimal light performances at a film thickness of 88 $\mu \text{m}$. The related luminous efficiency (LE), correlated color temperature (CCT), and chromaticity coordinate are 108.8 lm/W, 5796 K, and (0.3256 and 0.3467), respectively. The down-PiG-CSP structure achieves higher LE and lower CCT than the up-PiG-CSP structure. Compared with the traditional phosphor-in-silicone (PiS)-CSP WLED, the PiG-CSP WLED avoids the carbonization of the converter and displays excellent thermal stability under high input current. The results determine that the PiG-CSP is a reliable and efficient packaging technology for high-power WLEDs. [ABSTRACT FROM AUTHOR]

Recent advancements in ultraviolet light-emitting diodes (UV-LEDs) have allowed for their successful integration into continuous disinfection reactors including small-scale systems designed for low UV transmission (UVT) applications. This study characterized the performance of the first commercially available benchtop continuous-flow multiple-wavelength UV-LED system used for the treatment of juices and beverages in thin film. Three beverages (coconut water, blue lemonade, and pink lemonade), two juices (green juice blend and beet juice blend), and saline solution were inoculated with a non-pathogenic Escherichia coli indicator organism and treated at 281 nm. The volume averaged fluence delivered to the samples per pass ranged between 1.6 and 11.6 mJ cm−2 and was dependent on their absorption coefficients which ranged from 0.67 to 26.9 cm−1. Microbial inactivation ranging from 4.2 to 7.2 log10 was achieved within a reasonable number of passes or treatment time in pink and blue lemonade, coconut water, and saline solution which corresponded to an absorption coefficient below 6 cm−1 (UVT = 0.3%). Other than in beet juice blend, which had the highest absorption coefficient, a 1-log10 reduction fluence value in the range of other E. coli strains (previously reported in water) was reported (1.9–5.8 mJ cm−2). These results also suggest that the continuous-flow UV-LED system can be used to investigate inactivation kinetics and effects on nutritional and quality parameters at multiple wavelengths following treatment of low UVT water samples and high UVT juices and beverages with absorption coefficients up to 10–12 cm−1 (4.6e−3 to 6.3e−6% UVT). [ABSTRACT FROM AUTHOR]