White LED Lamp Research Articles

Effects of LED light quality on the growth of pepper seedling in plant factory

The extensive environment, especially low temperature and weak lighting in winter and spring, which limits the growth of pepper (Capicum annuum L.) seedlings, the use of plant factory with artificial lighting technology can effectively control the lighting environment to produce high-quality seedlings. In this study, white LED lamps with R:B ratio of 0.7 (L0.7) and 1.5 (L1.5) and red-blue LED lamps with R:B ratio of 3.5 (L3.5) were used to cultivate seedlings of “CAU-24” pepper in the light intensity of 250 μmol/m2·s and photoperiod of 12 h/d, white fluorescent lamps with R:B ratio of 1.7 (F1.7) was used as control. The results showed that plant height, stem diameter, hypocotyl length, biomass accumulation, light energy use efficiency (LUE) and electric energy use efficiency (EUE) of pepper seedling under L1.5 were the highest. After 36 days of sowing, the dry weight of shoot reached 302.8±45.2 mg/plant. Leaf area reached maximum value of 153.5±22.0 cm2 under L0.7. The contents of chlorophyll a, chlorophyll b and total chlorophyll of pepper seedling leaves under all kinds of LED light were greater than F1.7, but there was no significant difference in net photosynthetic rate. The total dry weight with lamp electric power consumption of L1.5 were 3.0 g/(kW·h) which was 1.5, 2, and 3 times greater than that of L3.5, L0.7, and F1.7, respectively. Therefore, compared with fluorescent lamp and other LED lamps, the white LED light quality with R:B ratio of 1.5 is suitable for pepper seedling production in plant factory because of the high LED lighting efficiency, greater LUE and EUE. Keywords: pepper seedlings, LED light quality, R: B ratio, light energy use efficiency (LUE), electric energy use efficiency (EUE) DOI: 10.25165/j.ijabe.20191205.4847 Citation: Liu N, Ji F, Xu L J, He D X. Effects of LED light quality on the growth of pepper seedling in plant factory. Int J Agric & Biol Eng, 2019; 12(5): 44–50.

Application of efficient photocatalytic process using a novel BiVO/TiO2-NaY zeolite composite for removal of acid orange 10 dye in aqueous solutions: Modeling by response surface methodology (RSM)

The purpose of the present study was to investigate the photocatalytic properties of a novel synthesized BiVO4/TiO2-NaY zeolite composite using the hydrothermal method for the removal of acid orange 10 (AO10), a typical azo dye, from aqueous solutions. In this respect, the experimental results revealed that the as-prepared BiVO4/TiO2-NaY zeolite composite had exhibited higher visible light photocatalytic performance for AO10 degradation than other materials under the irradiation of 12 W white LED lamp. The enhanced photocatalytic efficiency was due to the fact that reduction in the recombination of electrons and holes had been supported by zeolite. The structural properties of the studied materials were also confirmed by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), energy-dispersive X-ray spectroscopy (EDXA), fourier-transform infrared spectroscopy (FT-IR), and diffuse reflectance spectroscopy (DRS). Moreover; the optimization of the experiments was performed using response surface methodology (RSM). At the optimum conditions, the observed maximum AO10 removal efficiency was reported by 99.91% of initial dye concentration: 10 mg/L, initial pH: 3, reaction time: 50 min, as well as catalyst dosage: 0.17 g/100 ml. Thus, this novel BiVO4/TiO2-NaY zeolite could be used as an effective catalyst to reduce AO10 dye from contaminated water.

Identification of dual luminescence centers from a single site in a novel blue-pumped Ca3Sc2Ge3O12:Ce3+ phosphor.

The luminescence spectra of some trivalent rare-earth ions in a garnet host present interesting multisite structures; however, their mechanism is still not fully understood. In this study, for the first time, we directly observed two luminescence centers of Ce3+ at a single site in a novel garnet Ca3Sc2Ge3O12 phosphor. The spectral characteristics of the two luminescence centers were clearly identified using site-selective and time-resolved spectroscopy. Luminescence excitation was observed at 425 nm and 450 nm, corresponding to emissions at 490 (Ce(i)) nm and 530 (Ce(ii)) nm. The decay curves confirmed the existence of energy transfer from Ce(i) to Ce(ii). The potential mechanisms of the multisite luminescence are also discussed. This study gives a new insight into the concentration-dependent red-shift and inhomogeneous broadening of the Ce3+ emission band in the garnet phosphor. The title phosphor showed excellent thermal stability, with more than 90% of the initial intensity at the functioning temperature (323 K). Finally, a white LED lamp was fabricated, which exhibited an excellent color rendering index (82.3) and a proper correlated color temperature (3582 K). These results demonstrate that Ca3Sc2Ge3O12:Ce3+ is highly promising to serve as a blue-pumped phosphor for white LEDs.

On the development of an effective image acquisition system for diamond quality grading.

In this paper, an effective diamond image acquisition system is proposed for capturing images of the diamond sample under inspection separately with transmitted and reflected light. The proposed system consists of two parts: a lighting system and an imaging system. The lighting system is a newly designed integrating sphere that can control the light distribution in the image plane and provide uniform illumination to the diamond sample while it is being inspected under white LED lamps with a specific spectral power distribution. The imaging system comprises industrial-grade lenses, cameras, and a sample loading plate. One set of lenses and a camera is installed at the port of the lower hemisphere. This arrangement ensures that all light rays illuminated to the image plane are transmitted light. On the other hand, all light captured by the other set of lenses and a camera installed on the upper hemisphere is reflected light. The proposed design utilizes the ray tracing processing method based on the physical properties of materials and adjusts the parameters of each optical component. When properly designed, the signal-to-noise ratio of captured diamond images is significantly improved, so that imperfections inside the diamond or on its surface can be clearly distinguished. The proposed image acquisition system is cost-effective and compact. The experimental results agree well with the theoretical analysis and verify the effectiveness of the proposed image acquisition system. The proposed system will facilitate, improve, and simplify automated diamond quality grading.

Effect of Two Levels of Temperature and Natural and Artificial Photoperiod on Growth and Metamorphosis of Bullfrog Tadpoles in an Intensive Rearing System

AbstractThe effect of two levels of temperature and natural and artificial photoperiods on the growth and metamorphosis of tadpoles of the American bullfrog Rana catesbeiana were evaluated in an intensive‐rearing culture environment. Four groups of tadpoles at Gosner stage 24–25 were subjected for 50 d to four different treatments: (1) Tadpole culture with temperature control system (25.9 ± 0.34°C) and natural photoperiod of 12.25 h light : 11.75 h dark (treatment T), (2) an artificial photoperiod of 10 h light : 14 h dark using a white LED lamp and no temperature control system (18.7 ± 1°C) (treatment P), (3) the combination of temperature control system (26.01 ± 0.44°C) and an artificial photoperiod (10 h light : 14 h dark) (treatment T/P), and (4) culture with no temperature control system (21.87 ± 1.09°C) and a natural photoperiod (12.25 h light : 11.75 h dark) (treatment N/S). The experiment was performed under greenhouse conditions. Tadpoles in treatments T and T/P had the best growth performance as measured by total length (45.34 ± 1.89 mm [mean ± SE] for T/P, 44.72 ± 2.13 mm for T), head length (17.15 ± 0.67 mm for T/P, 18.34 ± 0.70 for T), and weight (1.00 ± 0.03 g for T/P, 1.14 ± 0.013 g for T). Tadpoles reared using white light LED lamps had reduced growth. The best results for tadpole metamorphosis were obtained in treatment T/P (25.9%), while treatment P presented the highest survival (36.2%). This experiment demonstrates that having temperature regulation is important to achieve better tadpole growth in intensive rearing systems. The regulation of both variables (T and P) is recommended for activating metamorphosis in the final phases of the tadpole development.

Using video processing to classify potato plant and three types of weed using hybrid of artificial neural network and partincle swarm algorithm

Fighting weed is an effective way to increase crop yield, which can be achieved with mechanical methods or spraying herbicides. Although the latter type is the most used, it can cause environmental pollution and food poisoning. For this reason, precision farming technologies are applied to minimize the required amount of herbicides, spraying only in small areas where weeds appear. The aim of this study is to locate and identify potato plants and three common types of weeds (Chenopodium album, Secale cereale L, and Polygonum aviculare L.) using a novel machine vision system. This system comprises two main subsystems: (1) a video processing subsystem capable of detecting green plants in each frame; and (2) a machine learning subsystem to classify weeds and potato plants. A hybrid approach, consisting of artificial neural networks (ANN) and particle swarm optimization algorithm (PSO), is used in classification. This approach is able to optimize the number layers, neurons per layers, network functions, weights and bias. Image capture was performed in four farms of Agria potato variety located in the Iranian province of Kermanshah, under controlled lighting conditions using white LED lamps. After shooting, plants were segmented and 30 color, texture and shape features were extracted from each one. Then, a decision tree is used to select the 6 most significant features, in terms of difference between potato plants and weeds. Finally, ANN-PSO method is applied to classify the inputs as potato plants or weeds. A comparison is performed using a Bayesian classifier. The experimental results show that ANN-PSO and Bayesian achieved an accuracy of 99.0% and 71.7%, respectively, on the training set, and 98.1% and 73.3%, respectively, for the test set. These results indicate that a precise site-specific sprayer can be designed using the proposed approach, optimizing the use of herbicides in precision farming.

Synthesis, crystal structures and photocatalytic properties of four silver(I) coordination polymers based on nitroterephthalic acid

A new family of Ag(I) coordination polymers, [Ag(pyz)(Hntph)]·2H2O (1), Ag(dpyz)2/2(Hntph) (2), Ag(epyz)2/2(Hntph) (3) and Ag(4,4′-bipy)(Hntph) (4), has been solvothermally prepared by the assembly of Ag(I), H2ntph and various N-donor ligands, respectively (H2ntph = nitroterephthalic acid, pyz = pyrazine, dpyz = 2,5-dimethyl pyrazine, epyz = 2,3,5,6-tetramethylpyrazine, 4,4′-bipy = 4,4′-bipyridine). Complex 1 exhibits a 1D structure constructed by the binuclear [Ag2(Hntph)2] units and pyz ligands. Complex 2 is a robust 3D metal organic compound with a novel 66 topological net. Complex 3 shows a 2D layer with binuclear [Ag2(Hntph)2] unit which different from complex 1 and complex 4 exhibits a 1D coordination polymer construction. The structures of complexes 1–4 have been determined by single-crystal X-ray diffraction analyses and characterized by infrared spectra (IR), thermogravimetric analyses (TGA) and powder X-ray diffraction (PXRD) analyses. Moreover, the optical band gaps of 1–4, and the photocatalytic properties of 3, 4 under the light of 90 W white LED lamp have also been investigated.

Excellent Luminous Efficacy and Color Homogeneity of White Light-Emitting Diodes with YPO4:Ce3+:Tb3+ Phosphor

In this paper, we focus on researching the method, which the color homogeneity and the lumen output of multi-chip white LED lamps (MCW-LEDs) need to support for increasing the efficiency. The successful results can be achieved by mixing the green YPO4:Ce3+:Tb3+ phosphor with their phosphor compounding. Through experiment results, we assert that the MCW-LEDs can achieve the significant consequence in performance by following that method and it is also again confirmed that when the concentration of YPO4:Ce3+:Tb3+ has tendency to increase, which impulse the development of the color uniformity and the luminous efficacy of MCW-LEDs with average correlated color temperatures (CCT) of 8500 K, while the color quality scale shows signs of gradual decline. It is not difficult to gain incredible presentation of MCW-LEDs if we are clever in choosing the suitable concentration and size of YPO4:Ce3+:Tb3+.

Improving Lighting Performance of High Color Temperature White LED Packages Using (La,Ce,Tb) PO4:Ce:Tb Phosphor

Enhancement of the color uniformity, the lumen output of the multi-chip white LED lamps (MCW-LEDs) at high color correlated temperature is a big challenge for researchers. However, an innovative LED lamp designed with a phosphor compounding, which combines (La,Ce,Tb) PO4:Ce:Tb (LaTb) green phosphor with YAG: CE yellow phosphor, is proposed as an optimal solution to this requirement. Index, using LaTb green phosphor into MCWLEDs could bring a superior optical performance for MCW-LEDs. It is found that the lumen output of this new MCW-LED at a high color temperature of 8500 K significantly improves up to 1600 lm compared to MCW-LEDs without LaTb phosphor. The simulation results demonstrated that the CCT deviation sharply decreases from 9000 to 1000 at the LaTb concentration range from 0 to 1.8 %, while the Color Rendering Index ability (CRI) and the Color Quality Scale (CQS) slightly decrease. To obtain the highest lumen output and the best color uniformity, the particle size range within 6 - 8 µm should be suggested. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

A broad band yellow-emitting Sr8CaBi(PO4)7:Eu2+ phosphor for n-UV pumped white light emitting devices

A novel broad band yellow-emitting Sr8CaBi(PO4)7:Eu2+ (SCBP:Eu2+) phosphor was synthesized via conventional high-temperature solid-state reaction. It's crystal structure and phase were investigated with X-ray diffraction (XRD), Rietveld refinement method and transmission electron microscopy (TEM). The photoluminescence spectra as well as fluorescence decay curves were measured and discussed. The SCBP:Eu2+ phosphor can exhibit a broad excitation band in the range from 260 to 425 nm, while the emission spectrum exhibits a broad asymmetric yellow emission band peaking at 606 nm under 400 nm excitation. By analyzing their structure and fluorescence decay lifetimes, five different Eu2+ luminescence centers in SCBP:Eu2+ phosphor were confirmed. Then the concentration quenching mechanism as well as the thermal stability has been discussed in detail. Furthermore, a white LED lamp which can exhibit good performance has been fabricated via combining a 400 nm near-ultraviolet (n-UV) chip with the commercial BAM:Eu2+ phosphor and the present SCBP:0.04Eu2+ sample. These results suggest that the SCBP:Eu2+ can be a promising yellow-emitting n-UV phosphor for white light emitting diodes.

Suspended Silicon Microphotodiodes for Electrochemical and Biological Applications.

Local electric stimulation of tissues and cells has gained importance as therapeutic alternative in the treatment of many diseases. These alternatives aim to deliver a less invasively stimuli in liquid media, making imperative the development of versatile micro- and nanoscale solutions for wireless actuation. Here, a simple microfabrication process to produce suspended silicon microphotodiodes that can be activated by visible light to generate local photocurrents in their surrounding medium is presented. Electrical characterization using electrical probes confirms their diode behavior. To demonstrate their electrochemical performance, an indirect test is implemented in solution through photoelectrochemical reactions controlled by a white-LED lamp. Furthermore, their effects on biological systems are observed in vitro using mouse primary neurons in which the suspended microphotodiodes are activated periodically with white-LED lamp, bringing out observable morphological changes in neuronal processes. The results demonstrate a simplified and cost-effective wireless tool for photovoltaic current generation in liquid media at the microscale.

BiVO4/Mn3O4 a novel p–n heterojunction photocatalyst functionalized with metalloporphyrins: Synthesis, charge transfer mechanism, and enhanced visible‐light photocatalysis for degradation of dye pollutant

A simple one‐pot hydrothermal method was successfully used to synthesize p–n heterojunction Mn3O4/BiVO4 composites with different contents of BiVO4. The experimental results show that the as‐prepared p–n heterojunction Mn3O4/BiVO4 composite exhibited higher visible light photocatalytic activity for the degradation of model dye methylene blue than the pure BiVO4 and Mn3O4 crystal under irradiation of 5 W white LED lamp. The enhanced photocatalytic efficiency is due to a large number of p–n heterojunctions in Mn3O4/BiVO4 composites, which effectively reduces the recombination of the electrons and holes by charge transfer from n‐type BiVO4 to p‐type Mn3O4 crystals. The prepared p–n heterojunction Mn3O4/BiVO4 composite was functionalized with cobalt, zinc, copper, and tin complexes of porphyrin. The energy diagrams of these prepared compounds were calculated via the electrochemical investigations and the electron transfer mechanism was discussed in details. The photocatalytic efficiency of the functionalized nanocomposites enhances significantly compared to the p–n heterojunction Mn3O4/BiVO4 under visible light irradiation. Between the prepared compounds, BiVO4/Mn3O4‐CoTCPP shows higher photocatalytic activity. This compound can destruct 98% of dye pollutant in 180 min under irradiation of 5 W white LED lamp. Furthermore, this photocatalyst shows proper stability after four cycle degradation test. © 2017 American Institute of Chemical Engineers Environ Prog, 36: 1439–1448, 2017

Parameters Investigation of Phosphors for Solid State Lighting

Five types of phosphors for LED ribbon beam elements in white LED lamps have been studied. The phosphor composition and colorimetric parameters have been researched during the experiment. It is found that the larger and more uniform the grains of the phosphor, the higher the emission efficiency. The most similar in color to the white color coordinates of the sample No. 5 phosphor having also higher brightness compared with samples No. 1 – No. 4.

Improving the angular color uniformity and the lumen output for multi-chip white LED lamps by green Ce0.67Tb0.33MgAl11O19:Ce,Tb phosphor

In this paper, we propose and discuss how to enhance the color uniformity and the lumen output of multi-chip white LED lamps (MCW-LEDs). This can be done by combining the green Ce0.67Tb0.33MgAl11O19:Ce,Tb phosphor (CeTb) and phosphor compounding. We find that the proposed method can have a significant effect on MCW-LEDs performance. Through simulation results, it is confirmed that the color uniformity and the lumen output of MCW-LEDs with average correlated color temperatures of 7000 and 8500 K grow with the concentration of CeTb, while the color rendering ability decreases. With proper choice of CeTb concentration, good performance of MCW-LEDs can be obtained.

Stabilization of Optical Properties of White LED lamp for lighting

Stabilization of Optical Properties of White LED lamp for lighting

Synthesis and luminescence properties of Ce3+-doped Y3Al3.5Ga1.5O12 green phosphor for white LEDs

A series of Ce3+-doped Y3Al3.5Ga1.5O12 green phosphors were successfully synthesized by a solid-state reaction method. The microstructure, morphology, luminescence spectra, luminescence quantum yield (QY) and thermal stability of the phosphor were investigated. The critical concentration of Ce3+ ions in Y3−mAl3.5Ga1.5O12:mCe3+ is m=0.06. The QY of Y2.94Al3.5Ga1.5O12:0.06Ce3+ phosphor is as high as 94% under excitation at 450nm and its luminescence intensity at 150°C still maintains 90% of that measured at 25°C, which are just a little worse than those of commercial Lu3Al5O12:Ce3+ green phosphor but much better than those of commercial (Sr,Ba)2SiO4:Eu2+ green phosphor. A white LED lamp was fabricated by employing Y2.94Al3.5Ga1.5O12:0.06Ce3+ as a green phosphor and commercial (Ca,Sr)AlSiN3:Eu2+ as a red phosphor (628nm), its Ra value, correlated color temperature (CCT), CIE1931 chromaticity coordinates and luminous efficiency is 84, 3081K, (x=0.4369, y=0.4142) and 102lm/W, respectively. The experimental results demonstrate that Y2.94Al3.5Ga1.5O12:0.06Ce3+ is a promising green phosphor not only can be used for high color rendering index white LEDs but also for high-power white LEDs.

Trap and nonradiative centers in Ba₃Si₆O₁₂N₂:Eu²⁺ phosphors observed by thermoluminescence and two-wavelength excited photoluminescence methods.

We have studied trap centers and nonradiative (NRR) recombination centers in a Ba3Si6O12N2:Eu2+ (BSON), one of promising materials for efficient and stable phosphors in white LED lamp applications. The energy distribution of four trap centers was obtained by thermo-luminescence (TL) with the excitation energy of 5.59eV. By superposing a below-gap excitation light of 1.77eV and observing the intensity change of the 5d-4f emission of Eu2+ centered at 2.36eV in our two-wavelength excited photoluminescence (TWEPL) measurement, both transient and steady state enhancement were observed. Such peculiar behavior of photo-stimulation is attributed to the coexistence of trap centers and NRR centers: the photoexcitation of electrons from trap centers generates the transient component, while that from NRR centers maintains the steady state component. An optical detection of relatively faint contribution of defects became possible in order to improve further the reliability and efficiency of phosphor materials.

Synthesis and photoluminescence properties of a cyan-emitting phosphor Ca3(PO4)2:Eu2+ for white light-emitting diodes

In this paper, a cyan-emitting phosphor Ca3(PO4)2:Eu2+ (TCP:Eu2+) was synthesized and evaluated as a candidate for white light emitting diodes (WLEDs). This phosphor shows strong and broad absorption in 250–450nm region, but the emission spectrum is prominent at around 480nm. The emission intensity of the TCP:Eu2+ was found to be 60% and 82% of that of the commercial BaMgAl10O17:Eu2+ (BAM) under excitation at 340nm and 370nm, respectively. Upon excitation at 370nm, the absolute internal and external quantum efficiencies of the Ca3(PO4)2:1.5%Eu2+ are 60% and 42%, respectively. Moreover, a white LED lamp was fabricated by coating TCP:Eu2+ with a blue-emitting BAM and a red-emitting CaAlSiN3:Eu2+ on a near-ultraviolet (375nm) LED chip, driven by a 350mA forward bias current, and it produces an intense white light with a color rendering index of 75.

Na0.60Ca0.40Sc0.60Mg0.40Si2O6:Eu2+,Mn2+: Tunable full-color-emitting solid-solution phosphor and its energy transfer property

Novel Na0.60Ca0.40Sc0.60Mg0.40Si2O6:Eu2+,Mn2+ (NCSMS:Eu2+,Mn2+) phosphors have been prepared, and the structural phase is derived from the solid-solution composition in (Na1−xCax)(Sc1−xMgx)Si2O6 (x=0.4). The as-prepared phosphor shows full-color white emission with a three-band profile, including the 5d–4f transition of Eu2+ in different emission centers (447 and 533nm) and the d–d transition of Mn2+ (654nm). Energy transfer (ET) from Eu2+ to Mn2+ in this system is also discussed. A white LED lamp was fabricated by using the composition-optimized phosphor, and the result verified that the phosphor is a promising candidate for w-LEDs application.

GaN-Based p–n Junction Blue-Light-Emitting Devices

Drastic improvements in the crystal quality of GaN enabled the conductivity control of both p- and n-type nitride semiconductors. This led the production of the high-brightness GaN-based p–n junction blue-light-emitting diode (LED) and the high-performance violet/blue laser diode (LD). The development of blue LEDs has allowed us to complete the set of three primary light colors with semiconductors. Coupled with available high-brightness red LEDs, blue/green LEDs are leading to the development of completely solid-state, full-color displays, traffic lights, signage, and specialized lighting applications. White LEDs composed of nitride-based blue/ultraviolet LEDs are more efficient than fluorescent lamps, and, as such, white LEDs are now being used in TVs, cellular phones, and computer displays. Moreover, white LED lamps are heading toward use in general lighting applications in houses, offices, and factories. Blue LEDs, together with available red LEDs, are also being applied as agricultural lighting sources. Nitride-based violet LEDs are being used for reading/writing data in optical disc systems. These nitride-based devices are robust in harsh environments, enable us to save a significant amount of energy, and provide a route to avoid the use of hazardous materials. The use of these devices will be one of our major weapons in the fight against global warming.