Red Light-emitting Diodes Research Articles

Wavelength and Light Intensity Affect Macro- and Micronutrient Uptake, Stomata Number, and Plant Morphology of Common Bean (Phaseolus vulgaris L.)

It is already known that light quality and intensity have major influences on the growth, etiolation, germination, and morphology of many plant species, but there is limited information about the effect of wavelength and light intensity on nutrient absorption by plants. Therefore, this study was established to evaluate the plant growth, stomata formation, chlorophyll index, and absorption of macro- and micronutrients by common bean plants under six light treatments. The experimental design was completely randomized and consisted of six treatments: strong blue (blue LED at high light intensity); weak blue (blue LED at low light intensity); strong red (red LED at high light intensity); weak red (red LED at low light intensity; pink (combined red + blue LED), and white (combined red + white led). The stomatal density (stomata mm−2); the SPAD index; plant height (cm); root length (cm); plant dry weight (g); root dry weight (g); and the concentrations of N, S, K, Mg, Ca, B, Zn, Mn, and Fe on leaf analysis were influenced by all treatments. We found that plant photomorphogenesis is controlled not only by the wavelength, but also by the light intensity. Etiolation was observed in bean plants under blue light at low intensity, but when the same wavelength had more intensity, the etiolation did not happen, and the plant height was the same as plants under multichromatic lights (pink and white light). The smallest plants showed the largest roots, some of the highest chlorophyll contents, and some of the highest stomatal densities, and consequently, the highest dry weight, under white LED, showing that the multichromatic light at high intensity resulted in better conditions for the plants in carbon fixation. The effect of blue light on plant morphology is intensity-dependent. Plants under multichromatic light tend to have lower concentrations of N, K, Mg, and Cu in their leaves, but the final amount of these nutrients absorbed is higher because of the higher dry weight of these plants. Plants under blue light at high intensity tended to have lower concentrations of N, Cu, B, and Zn when compared to the same wavelength at low intensity, and their dry weight was not different from plants grown under pink light. New studies are needed to understand how and on what occasions intense blue light can replace red light in plant physiology.

Proton-Prompted Ligand Exchange to Achieve High-Efficiency CsPbI3 Quantum Dot Light-Emitting Diodes

HighlightsA new proton-promoted in situ ligand exchange strategy based on CsPbI3 quantum dots.The ligand exchange strategy maintains the quantum confinement effect of quantum dots and significantly improves the stability and photophysical properties of CsPbI3 quantum dots.The performance of light-emitting diodes based on CsPbI3 quantum dots is significantly improved, the external quantum efficiency is increased from 18.63% to 24.45%, and the half-operational lifetime is increased by 70 times.

Improved Performance of AlGaInP Red Micro Light-Emitting Diodes by Sidewall Treatments of Citric Acid

Improved Performance of AlGaInP Red Micro Light-Emitting Diodes by Sidewall Treatments of Citric Acid

Effects of green light supplementation with red and blue combinations of LED light spectrums on the growth and transcriptional response of Haematococcus pluvialis.

Light management strategy is crucial for improving microalgal production in terms of higher biomass and economically valuable bioactive molecules. However, green light has received less attention in developing light managements for algae and higher plant due to its low absorption rate by chlorophyll. In this study, the effects of green light supplementation, in the combination with red and blue light were investigated in Haematococcus pluvialis. 10% and 20% of green light supplementations were applied in 3:2 ratios of red and blue LED light combinations as an expense of red-light. Growth rates, chlorophyll concentration, and dry weight were measured to assess the growth kinetics of H. pluvialis along with the relative transcript accumulations of four mRNAs: Rubisco, PTOX2, PsaB, and PsbS. Growth rates, chlorophyll concentrations and dry weight were found significantly higher in presence of 10% green light supplementation compared to red and blue light combinations. The relative transcript accumulations of Rubisco and PsbS genes showed significant upregulation at the end of the experiments (with the fold change of 42.91 ± 12.08 and 98.57 ± 27.38, respectively, relative to the beginning of the experiments) compared to combinations of red and blue light (fold change of 19.09 ± 3.0 and 47.77 ± 14.21, respectively, relative to beginning of the experiments). PsaB and PTOX2 transcripts did not show significant accumulation differences between treatments. It seems that green light has a dose dependent additive effect on the growth rate of H. pluvialis. The upregulation of Rubisco and PsbS may indicate green light dependent carbon assimilation and light-harvesting response in H. pluvialis.

Fast-Charging Li4Ti5O12 Anode Driven by Light

Lithium-ion batteries with fast charging capabilities are crucial for widespread adoption of electric vehicles, as they will increase acceptance of the technology and reduce range anxiety for drivers. To achieve this, advanced fast charging technologies and alternative methods to enhance the slow electrochemical processes are desperately required. This study applied light-emitting diode (LED) photo-assisted fast charging to Li4Ti5O12 (LTO), a large bandgap cubic spinel material, to enhance charging speed through electronic-structure coupling. UV LED-generated light irradiation on to the electrode interface boosted the ion diffusion and lithium cation addition by a factor of 1.3 during electrochemical lithiation, resulting in a 30% decrease in charging time under ambient conditions. Red LED light was not effective in accelerating the reaction as it does not provide sufficient energy. The first-principles calculations support the concept that UV illumination generates charges by overcoming the material’s bandgap and effectively reducing it through the introduction of additional titanium defect states.

An efficiently excited Eu3+ luminescent site formed in Eu,O-codoped GaN

For the development of III-nitride-semiconductor-based monolithic micro-light-emitting diode (LED) displays, Eu,O-codoped GaN (GaN:Eu,O) is a promising material candidate for the red LEDs. The luminescence efficiency of Eu-related emission strongly depends on the local atomic structure of Eu ions. Our previous research has revealed that post-growth thermal annealing is an effective method for reconfiguring luminescent sites, leading to a significant increase in light output. We observed the preferential formation of a site with a peak at ∼2.004 eV by the annealing process. In this study, we demonstrate that it is a previously unidentified independent site (OMVPE-X) using combined excitation–emission spectroscopy and time-resolved photoluminescence measurements. In addition, we perform excitation power-dependent photoluminescence measurements and show that this OMVPE-X site dominates the emission at a low excitation power region despite its small relative abundance, suggesting a high excitation efficiency. Most importantly, applying our annealing technique to an LED exhibits a reasonably increased electroluminescence intensity associated with OMVPE-X, confirming that this site has a high excitation efficiency also under current injection. These results demonstrate the importance of OMVPE-X as a notable luminescent site for brighter and more efficient GaN:Eu,O-based LEDs.

Photoregulation of the biosynthetic activity of the edible medicinal mushroom Lentinula edodes in vitro.

The findings of the study demonstrate the impact of low-intensity laser and quasi-monochromatic light on the biosynthetic activity of the edible medicinal fungus L. edodes during submerged cultivation. An artificial lighting installation based on matrices of light-emitting diodes (LED) emitting light at 470nm (blue), 530nm (green), 650nm (red), and argon gas laser (488nm) was used. Irradiation with blue and red LED and laser led to a shortening of the lag phase by 2days and an increase in the mycelial mass. Irradiation with laser light resulted in the highest mycelial mass yield (14.1g/L) on the 8th day of cultivation. Irradiation in all used wavelength ranges caused an increase in the synthesis of both extracellular and intracellular polysaccharides. Laser light at 488nm and LED at 470nm proved to be the most effective. Irradiation with red, green, and blue laser light caused an increase in the total amount of fatty acids in the mycelial mass compared to the control. A significant distinction in qualitative composition was observed: short-chain acids C6‒C12 compounds were produced under red light irradiation, whereas long-chain C20‒C24 were formed under green light irradiation. The most significant changes in the aromatic profile of the mycelial mass and culture liquid were recorded upon irradiation with green light. The content of aromatic components increased 24.6 times in the mycelial mass and 38.5 times in the culture liquid. The results suggest the possibility of using low-intensity quasi-monochromatic light for targeted regulation of L. edodes biosynthetic activity.

Stable and efficient pure blue quantum-dot LEDs enabled by inserting an anti-oxidation layer

The efficiency and stability of red and green quantum-dot light-emitting diodes have already met the requirements for commercialization in displays. However, the poor stability of the blue ones, particularly pure blue color, is hindering the commercialization of full-color quantum-dot light-emitting diode technology. Severe hole accumulation at the blue quantum-dot/hole-transport layer interface makes the hole-transport layer prone to oxidation, limiting the device operational lifetime. Here, we propose inserting an anti-oxidation layer (poly(p-phenylene benzobisoxazole)) between this interface to take in some holes from the hole-transport layer, which mitigates the oxidation-induced device degradation, enabling a T50 (time for the luminance decreasing by 50%) of more than 41,000 h with an initial brightness of 100 cd m−2 in pure blue devices. Meanwhile, the inserted transition layer facilitates hole injection and helps reduce electron leakage, leading to a peak external quantum efficiency of 23%.

Copper oxide incorporated ball-mill produced less-defective graphene for hybrid supercapacitors

Here, to increase the conductivity and the electrochemical performance of copper oxide electrodes, D-sorbitol assisted ball-mill synthesized graphene is utilized and copper oxide/graphene supercapacitor electrode materials are prepared in an environmentally benign solvothermal-assisted method. The characterization studies indicated the formation of well-dispersed Cu2O and CuO over less-defective few layered graphene with strong Cu-O-C interactions and the electrochemical studies indicated the synergistic effect of copper oxides and graphene in the supercapacitor performance of the electrodes. The nanocomposite in its best composition of copper oxides with graphene showed the highest specific capacitance of 1589 F/g at a current density of 2 A/g and 100 % capacitance retention after 10,000 continuous charge-discharge cycles. The diffusive contribution to the capacitance of the nanocomposite is greater due to the pseudocapacitive effect of copper oxides. The symmetrical coin cell fabricated using copper oxide/graphene showed a specific capacitance of 27.23 mF/cm2 at a current density of 0.01 mA/cm2. The practical applicability of the fabricated supercapacitor devices in lighting up a red LED is also displayed here.

Nucleophilic Reaction-Enabled Chloride Modification on CsPbI3 Quantum Dots for Pure Red Light-Emitting Diodes with Efficiency Exceeding 26 .

High-performance pure red perovskite light-emitting diodes (PeLEDs) with an emission wavelength shorter than 650 nm are ideal for wide-color-gamut displays, yet remain an unprecedented challenge to progress. Mixed-halide CsPb(Br/I)3 emitter-based PeLEDs suffer spectral stability induced by halide phase segregation and CsPbI3 quantum dots (QDs) suffer from a compromise between emission wavelength and electroluminescence efficiency. Here, we demonstrate efficient pure red PeLEDs with an emission centered at 638 nm based on PbClx -modified CsPbI3 QDs. A nucleophilic reaction that releases chloride ions and manipulates the ligand equilibrium of the colloidal system is developed to synthesize the pure red emission QDs. The comprehensive structural and spectroscopic characterizations evidence the formation of PbClx outside the CsPbI3 QDs, which regulates exciton recombination and prevents the exciton from dissociation induced by surface defects. In consequence, PeLEDs based on PbClx -modified CsPbI3 QDs with superior optoelectronic properties demonstrate stable electroluminescence spectra at high driving voltages, a record external quantum efficiency of 26.1 %, optimal efficiency roll-off of 16.0 % at 1000 cd m-2 , and a half lifetime of 7.5 hours at 100 cd m-2 , representing the state-of-the-art pure red PeLEDs. This work provides new insight into constructing the carrier-confined structure on perovskite QDs for high-performance PeLEDs.

MnO2 Nanoparticle‐Loaded Self‐Doped (N/O) Porous Carbon Derived from Orychophragmus Violaceus for Application as a High‐Performance Supercapacitor

AbstractWaste orychophragmus violaceus was used to prepare a novel 3D self‐doped (N/O) porous carbon (OPC). The aim was to expand the application and increase the value of waste orychophragmus violaceus. In order to improve its specific capacitance, composites OPC@MnO2x of OPC and MnO2 were prepared by simple hydrothermal method. In 6 M KOH, specific capacitance obtained by OPC at 1 A g−1 is 268 F g−1, surprisingly, specific capacitance of OPC@MnO232 can be up to 419 F g−1 at 1 A g−1 and its capacitance retention rate is as high as 83.62 % after 10000 cycles (20 A g−1). The energy density of OPC@MnO232//OPC asymmetric supercapacitor in 1 M Na2SO4 can even reach 14.22 Wh kg−1 at 400 W kg−1, besides, it showed good cycling stability after 10000 cycles (20 A g−1), with capacitance retention rate of up to 86.64 %. Finally, the device is tested in an application. Connecting two identical asymmetric supercapacitors in series enables red LED to emit greater than 90 s. Overall, this study confirms that the waste orychophragmus violaceus derived porous carbon can reduce the wastage of waste resource, additionally, the composite material prepared is an electrode material for high‐performance supercapacitors with broad prospects.

Efficient InGaN‐Based Red Light‐Emitting Diodes by Modulating Trench Defects

AbstractTrench defects in multi‐quantum wells (MQWs) have been considered as flawed structures that severely degraded the internal quantum efficiency (IQE) of light‐emitting diodes (LEDs) in the past. In this research, trench defects are innovatively utilized to enhance the efficiency of red InGaN LEDs. Specifically, dual‐color MQWs structures are applied to modulate trench defects. The upper red MQWs, grown on top of green MQWs with a high density of trench defects, exhibit a significant wavelength redshift of 68 nm and ≈ 6‐fold luminescence enhancement compared to those without intentionally introduced trench defects. Red InGaN LEDs with an IQE of 16.4% are achieved with this epitaxy growth strategy. Such wavelength redshift is attributed to the more indium incorporation due to the strain relaxation effect of trench defects. Moreover, the luminescence enhancement originates from the strong emission of the red MQWs inside trench defects, mainly attributed to strain relaxation and defect shielding by the wide and deep trenches. Achieving red emission by modulating trench defects is simple and reproducible without requiring additional substrate designs, which provides a novel way toward high‐efficiency red InGaN LEDs.

Red light-emitting diode therapy minimizes the functional deleterious effects of the antiretroviral ritonavir on osteoblasts in vitro.

Long-term human immunodeficiency virus (HIV)-infected patients are considered at higher risk for osteoporosis. Among the various causes that lead these patients to lower bone health, there is the use of antiretroviral drugs (ARVs), especially protease inhibitors (PI), such as ritonavir (RTV). In this context, emerge the potential benefits of LED therapy, whose effects on bone cells are currently being extensively studied, showing a modulation in cell differentiation. However, it remains unclear if photobiostimulation might interfere with RTV effects on osteoblast differentiation. In the present study, we investigated the effects of red LED (625nm) irradiation (15 mW/cm2, 0.2J/cm2, and 8 mW/cm2, 0.12J/cm2) on osteoblast cell line MC3T3-E1 treated with RTV (2.5, 5, and 10μg/mL). Our results indicated that red LED irradiation was able to reverse, or at least minimize, the deleterious effects of RTV on the osteoblasts. Neither the ARV treatments 5 and 10μg/mL (104.4% and 95.01%) nor the LED protocols (100.3% and 105.7%) statistically altered cell viability, assessed by the MTT assay. Also, the alkaline phosphatase activity and mineralization showed a decrease in osteoblast activity followed by ARV exposure (39.3-73%), which was attenuated by LED in more than 70% with statistical significance (p < 0.05). In conclusion, photobiostimulation with red LED at 625nm was associated with improved beneficial biological effects as a potential inducer of osteogenic activity on RTV-affected cells. This is the first study that investigated the benefits of red LED irradiation over ARV-treated in vitro osteoblasts.

Generalization and discrimination of inhibitory avoidance differentially engage anterior and posterior retrosplenial subregions.

In a variety of behavioral procedures animals will show selective fear responding in shock-associated contexts, but not in other contexts. However, several factors can lead to generalized fear behavior, where responding is no longer constrained to the conditioning context and will transfer to novel contexts. Here, we assessed memory generalization using an inhibitory avoidance paradigm to determine if generalized avoidance behavior engages the retrosplenial cortex (RSC). Male and female Long Evans rats received inhibitory avoidance training prior to testing in the same context or a shifted context in two distinct rooms; one room that had fluorescent lighting (Light) and one that had red LED lighting (Dark). We found that animals tested in a light context maintained context-specificity; animals tested in the same context as training showed longer latencies to cross and animals tested in the shifted context showed shorter latencies to cross. However, animals tested in the dark generalized their avoidance behavior; animals tested in the same context and animals tested in the shifted context showed similarly-high latencies to cross. We next examined expression of the immediate early gene zif268 and perineuronal nets (PNNs) following testing and found that while activity in the basolateral amygdala corresponded with overall levels of avoidance behaviors, anterior RSC (aRSC) activity corresponded with learned avoidance generally, but posterior RSC (pRSC) activity seemed to correspond with generalized memory. PNN reduction in the RSC was associated with memory formation and retrieval, suggesting a role for PNNs in synaptic plasticity. Further, PNNs did not reduce in the RSC in animals who showed a generalized avoidance behavior, in line with their hypothesized role in memory consolidation. These findings suggest that there is differential engagement of retrosplenial subregions along the rostrocaudal axis to generalization and discrimination.

A novel highly thermal-stable Ba2GdSbO6:Sm3+ phosphor with intrinsic deep-red emission for personal identification and plant cultivation LEDs

The novel Sm3+-activated Ba2GdSbO6 (BGSO) antimonate phosphors with double perovskite structure were first synthesized via a high-temperature solid-state reaction. The products' crystallographic structure, phase purity, micro-morphology, and luminescent properties were analyzed. The Ba2GdSbO6:Sm3+ phosphor could be effectively excited by 406 nm irradiation, and four sharp peaks accompanied by a broad band were presented. The dominant peak was located at 602 nm, corresponding to the typical 4G5/2 → 6H7/2 transition of Sm3+ ions, while the deep-red emission band at 675 nm is owing to the BGSO host intrinsic emission. Impressively, the product shows high thermal stability with its emission intensity of 88.8% at 420 K. Moreover, its thermal quenching temperature exceeds 480 K. The electroluminescent spectrum of the red light-emitting diode (LED) device fabricated by BGSO:0.02Sm3+ overlapped well with the absorption spectra of the phytochromes, suggesting its potential for plant cultivation light source. The sample with the best doping concentration was selected for surface modification with oleic acid (OA). In latent fingerprint and lip print detection, the phosphor showed high resolution, high contrast, and low background interference applied on different substrates. Hence, the BGSO:Sm3+ phosphor can be considered a promising material in plant cultivation LEDs and latent fingerprint and lip print visualization.

Brassica microgreens cabbage (Brassica oleracea), radish (Raphanus sativus) and rocket (Eruca vesicaria) (L.) Cav: application of red‐light emitting diodes lighting during postharvest storage and in vitro digestion on bioactive compounds and antioxidant activity

SummaryMicrogreens grow best under light‐emitting diodes (LED), an artificial light source. In this study, LED lights (red, blue and far‐red) were tested on brassica microgreens to see if they induced an increase in bioactive compounds (glucosinolates and phenolics). In vitro digestion also measured bioavailable bioactive compounds in the intestinal phase. LED lights (red, blue and far‐red) were applied for 6 h in storage at 5 °C and 85% RH for 5 days on cabbage (Brassica oleracea), radish (Raphanus sativus) and rocket (Eruca vesicaria (L.) Cav). Red light significantly enhanced ascorbic acid, total phenols, kaempferol and quercetin glycoside concentrations in all three Brassica microgreens and antioxidant activities. Exposure to red LED light increased 4‐methoxyglucobrassicin (cabbage), glucoraphenin (radish), glucoraphanin A and glucoerucin (rocket). Red light stress may have resulted in secondary metabolite production in immature plants. An in vitro digestion showed higher concentrations of phenolic compounds, glucosinolate components and antioxidants in the intestinal phase. Red LED light is recommended as a postharvest treatment for improving cabbage, rocket and radish bioactive compounds.

Influence of dynamic LED irradiation mode on the content of nitrates, structural and functional characteristics of lettuce plants

One of the promising irradiation modes for plant is dynamic, when parameters change throughout the growing process depending on certain factors. In this work, lettuce plants were illuminated under different LED light sources, including white (2700 K), 30% white (2700 K) + 70% red (660 nm), 15% blue (445 nm) + 85% red (660 nm), 40% blue (445 nm) + 20% red (630 nm) + 40% red (660 nm) and dynamic mode for 35 days to investigate the effects. Photosynthetically active flux density was the same for all lettuce samples during the experiment (210 µmol m−2 s−1). The results showed the effects of photoregulation on the growth and development of lettuce plants. Optimal irradiation regime for lettuce plants was a dynamic regime formed using two colour components: white (2700 K) and red (660 nm) LEDs. Lettuce grown under dynamic conditions had a lower content of nitrates and developed faster than under stationary conditions.

Complementary use of visual and olfactory cues to assess capture of Bactrocera dorsalis (Hendel): Implementation and field verification via an IoT-based automatic monitoring system.

This study examined the effect of combining visual and olfactory cues to attract oriental fruit flies (OFFs). Six different colored light-emitting diodes (LEDs) served as a visual attractant and methyl eugenol served as olfactory bait to lure male flies. An internet of things (IoT)-based pest monitoring system, consisting of sensor nodes, a gateway, and automatic counting traps, was deployed in the field to automatically collect environmental data and pest counts. The results of the calibrated experiments indicated that green, yellow, or red LEDs exhibited better performance in attracting flies than white, purple, or blue LEDs or no LEDs. With an accurate combination of visual and olfactory cues, the proposed IoT-based pest monitoring system may be an effective tool in agricultural pest management, given its advantages for efficiently capturing OFFs in a labor and time saving manner, providing accurate information regarding increases in pest populations, and enabling long-term, real-time data collection.

Biosorption and desorption of chromium using hybrid microalgae-activated sludge treatment system

This study utilised a mixed culture of Chlorella vulgaris and bacteria from sludge to treat synthetic tannery wastewater (STWW) in modified stirred-tank photobioreactors (MSTPBRs). The MSTPBRs were fabricated locally and operated at irradiance value of 580 µmol/m2s supplied by red light-emitting diodes at 12:12 light–dark cycles and 100 ± 1 rpm continuous stirring. In each case, 50, 100 and 150 mg/L concentrations of STWW were inoculated with mixed culture of microalgae and bacteria in three MSTPBRs, with the control MSTPBR operating at 50 mg/L of STWW. Chromium concentrations were measured using colorimeter whilst Fourier transform infrared spectroscopy (FTIR) indicated possible Cr biosorption. Maximum Cr (VI) and total Cr removal efficiencies of 93 and 94% were achieved, with more than 78% total Cr recovery. Results from FTIR suggested involvement of Chlorella vulgaris in the Cr biosorption. The hybrid microalgae-bacteria system efficiently treated tannery wastewater with considerable Cr removal efficiencies. The potentials of the system in treating tannery wastewater in larger scale may require further investigation.

The Colors in Medieval Illuminations through the Magnificent Scriptorium of Alfonso X, the Learned

This pioneering work studied the medieval color palette of four manuscripts produced in the scriptorium of Alfonso X, king of the Crown of Castile (r. 1252-84), including the Songs of Holy Mary (Cantigas de Santa Maria, in Rich Codex and Musicians’ Codex), Lapidary (Lapidario), and Book of Games (Libro de los juegos). Scientific analysis based on fiber-optics reflectance spectroscopy in the visible and Raman spectroscopy showed a color palette based on lapis lazuli, indigo, azurite, vermilion, red lead, orpiment, yellow ochre, two different greens (bottle green and vergaut), lead white, carbon-based black, and most importantly, brazilwood pinks, reds, and purples. So, it is now the first reported use of this lake pigment in European medieval manuscript illumination. The painting technique is also discussed. The diversity of colors and techniques, with the presence of lapis lazuli, brazilwood lake pigments, purple, and gold, demonstrates Alfonso X’s desire to produce sumptuous manuscripts.