Light-emitting Diode Light Source Research Articles

Photoluminescence measurement of ruby excited by duty ratio-controlled pulse light-emitting diodes (LED) light source.

Photoluminescence (PL) spectra from ruby were obtained using a highly stable LED light source, employing pulse width modulation technique for excitation. The temporal variation in PL intensity caused by the increasing temperature of the LED used for excitation can be mitigated by adjusting the duty ratio (%) of the pulsed LED light to below 10% for cooling the LED. Stable PL spectra measurements were achieved with a duty ratio of less than 10% using a duty ratio-controlled pulsed LED light source, as temperature fluctuations in LED light intensity are minimized at duty ratios less than 10%. Furthermore, fluctuations in the measured PL intensity were diminished by setting the frequency of the pulsed LED light source to greater than 1kHz. This method enables more reliable, cost-effective, and stable PL measurements for material characterization in semiconductors, photonics, and nanotechnology.

TiO2-Coated Meltblown Nonwoven Fabrics Prepared via Atomic Layer Deposition for the Inactivation of E. coli as a Model Photocatalytic Drinking Water Treatment System

The controlled manufacturing of semiconductor photocatalysts is crucial to their development for drinking water treatment. In this study, TiO2-coated meltblown nonwoven fabrics prepared via Atomic Layer Deposition (ALD) are applied for the inactivation of Escherichia coli (E. coli). It is observed that in the presence of an ultraviolet light-emitting diode (UV-LED) light source (255 nm), 1.35 log E. coli inactivation is achieved. However, exposure to catalyst-coated fabrics in addition to the light source resulted in >4 log E. coli inactivation, suggesting a much higher rate of hydroxyl radical formation on the surface, leading to cell death.

Smartphone-based imaging colorimetric assay for monitoring the quality of curcumin in turmeric powder.

This research developed a colorimetric assay for semi-quantitative curcumin detection. The screening test was performed using a ferric chloride to form a brownish color which was further used to evaluate the amount of curcumin in the turmeric powder samples. The quantitative assay was performed based on the color intensity of the curcumin target using a smartphone digital image colorimetry with a developed lightbox constructed with a white light-emitting diodes (LED) light source as the measurement device. Images in red, green, and blue (RGB) color were processed to obtain relevant colors from the image and the color values were used to analyze curcumin concentrations. The intensity of the ΔB was correlated to the concentration of curcumin with high sensitivity. The method showed a linear range between 0.25 and 5mg L-1 with the LOD and LOQ of 0.12 and 0.41mg L-1, respectively. Sample analysis was carried out in turmeric powders. Curcumin in turmeric powder samples was simply extracted using acetonitrile followed by dilution 100 times for sample preparation. The accuracy was tested by spiking 0.25, 1.00, and 4.00mg L-1 of standard curcumin into the turmeric sample solution. The average percentage recoveries were acceptable in all samples (90-104%). The method was validated by comparing the results obtained from the proposed method and high-performance liquid chromatography (HPLC). There was no statistically significant difference between the two methods (P = 0.05).

Simulating PDT of port-wine stains in the in vivo chicken wattle model using Hemoporfin and radiation at 532 nm: Comparison of a LED and a laser source

Port-wine stain (PWS) birthmarks are congenital capillary malformations occurring in 0.3 %∼0.5 % of newborns. Hemoporfin-mediated vascular-acting photodynamic therapy (Hemoporfin PDT) is an emerging option for treating PWS. This in vivo study aimed to compare laser and light-emitting diodes (LED) as light source for Hemoporfin PDT. Chicken wattles were used as the animal model. Color and histopathological changes were evaluated after combining Hemoporfin with KTP laser or LED light source of 532 nm at the same doses. Both PDT approaches could induce significant vascular injury and color bleaching. Although the use of the laser resulted in a greater vascular clearance, the LED showed more uniform distribution both in the beam profiles and tissue reaction and exhibited better safety. This in vivo study suggests that the LED is a favorable choice for larger PWS lesion.

Dual-channel on-chip data transmission system using UV light based on GaN-on-Si wafer

The ultraviolet photonic integrated circuits possess application prospects in ultraviolet (UV) microscopy, bio-sensing, on-chip data communication, etc. Herein, we propose a UV light on-chip data transmission system based on epitaxial GaN on silicon. This simple system includes a light-emitting diode light source, a modulator, a Y-branch waveguide and two photodetectors. Both direct modulation and indirect modulation are configured into this system and demonstrated by experiment. Dual-channel communication is also implemented through Y-branch waveguide. As all the active devices share the same InGaN/AlGaN multiple quantum wells (MQW) diode structure, this 378 nm UV light data transmission system can be monolithically integrated through the compatible manufacturing processes. By adopting the integrated MQW modulator with relatively large active region area, a significant modulation effect can be achieved with modulation depth greater than 48% under reverse bias of 20 V.

Handheld Biosensor System Based on a Gradient Grating Period Guided-Mode Resonance Device.

Handheld biosensors have attracted substantial attention for numerous applications, including disease diagnosis, drug dosage monitoring, and environmental sensing. This study presents a novel handheld biosensor based on a gradient grating period guided-mode resonance (GGP-GMR) sensor. Unlike conventional GMR sensors, the proposed sensor's grating period varies along the device length; hence, the resonant wavelength varies linearly along the device length. If a GGP-GMR sensor is illuminated with a narrow band of light at normal incidence, the light resonates and reflects at a specific period but transmits at other periods; this can be observed as a dark band by using a complementary metal oxide semiconductor (CMOS) underneath the sensor. The concentration of a target analyte can be determined by monitoring the shift of this dark band. We designed and fabricated a handheld device incorporating a light-emitting diode (LED) light source, the necessary optics, an optofluidic chip with an embedded GGP-GMR sensor, and a CMOS. LEDs with different beam angles and bandpass filters with different full width at half maximum values were investigated to optimize the dark band quality and improve the accuracy of the subsequent image analysis. Substrate materials with different refractive indices and waveguide thicknesses were also investigated to maximize the GGP-GMR sensor's figure of merit. Experiments were performed to validate the proposed handheld biosensor, which achieved a limit of detection (LOD) of 1.09 × 10-3 RIU for bulk solution measurement. The sensor's performance in the multiplexed detection of albumin and creatinine solutions at concentrations of 0-500 μg/mL and 0-10 mg/mL, respectively, was investigated; the corresponding LODs were 0.66 and 0.61 μg/mL.

Direct immersion single-drop microextraction combined with fluorescence detection using an optical probe. Application for highly sensitive determination of rhodamine 6G

The use of an optical probe for fluorescence detection combined with direct immersion single-drop microextraction has been demonstrated as an innovative approach. The optical probe served both as a drop holder for extractant and as a measuring device which made it possible to eliminate the use of cuvettes. A laser and a light emitting diode (LED) were tested as possible light sources. Both of them showed comparable results. However, given the much smaller half-band width of the laser radiation, its use has proven to be preferable since background correction can be eliminated. Direct immersion single-drop microextraction of an ionic association complex of rhodamine 6G with picric acid with subsequent fluorescent detection (λex was 532 nm and 525 nm for laser and LED, respectively; λem was 560 nm for both laser and LED) was used a model system to evaluate the new approach. The extractant phase was a 55 μL amyl acetate microdrop fixed in the optical part of the probe. LOD, LOQ and linear calibration range were found as 0.14, 0.48 and 0.5–10 nmol L−1, and 0.15, 0.50 and 0.5–5 nmol L−1 for laser and LED light sources, respectively. The accuracy of the method was assessed by analyzing real water samples.

Effect of LED Light Frequency on an Object in Terms of Visual Comfort

Light emitting diodes (LEDs) play an essential role in lighting, and green earth activities because of their high efficiency, longevity, and reduction of carbon dioxide emissions during illumination. However, the brightness level of LED light sources must be adjusted appropriately for the backlight source or illumination; therefore, pulse amplitude modulation (PWM) is a commonly used method of LED control. This article experimentally investigated human interaction with the visual comfort effect of the light obtained using different PWM frequencies on an object in a sensor-based intelligent lighting system. Critical light frequencies are vital for the eye to distinguish light stimuli according to time. Histograms of the object were created according to the light frequency, and the results are discussed. The eye’s response to light frequencies changing over time is important for visual comfort, and examining light frequencies in the range of 25–250 Hz was sufficient to conclude the study. It has been experimentally shown that light frequencies around 160 Hz, and above this value provide visual comfort.

Amorphous molybdenum sulfide/polymeric carbon nitride composite with multiple interfaces for boosting photoelectrochemical water splitting performance

Rational interface design is an important way to improve the photoelectrochemical activity of catalysts in the sustainable energy and the environment. Herein, we simultaneously realize the construction of polymeric carbon nitride (PCN)-based homojunction (HPCN) and amorphous molybdenum sulfide (a-MoSx) /PCN heterojunction (a-MoSx/HPCN) in the composite catalyst system by one-pot calcination. The presence of a-MoSx was confirmed by X-ray photoelectron spectroscopy (XPS) and element mapping. X-ray diffraction (XRD) and transmission electron microscopy (TEM) revealed the amorphous characteristics of molybdenum sulfide. The photoluminescence (PL) spectroscopy indicated that the photo-generated carrier recombination of composite is effectively inhibited after constructing the homojunction and loading molybdenum sulfide. The confined effect of the PCN matrix induced the formation of ultrafine size a-MoSx, and its co-catalyst function is prominent. The optimized composite catalyst showed obvious boosting activity in photoelectrochemical water slitting. Photocathode current of −161 μA cm−2 (0 V vs. RHE) and photoanode current of 10 μA cm−2 (1.23 V vs. RHE) are almost 12 and 5 times than single PCN homojunction under the irradiation of 25 W light-emitting diode light source. This boosted activity can be attributed to the multiple interface effect of the n-n junction of PCN/PCN and the p-n junction of a-MoSx/PCN as well as the co-catalysis of amorphous molybdenum sulfide. The synergies between various merits effectively improved the absorption of visible light, the separation of photogenerated electrons and holes, and the addition of more reactive sites. This paper provides a new idea for interface engineering of PCN-based composite photoelectrode.

Effect of Different Monochromatic LEDs on the Environmental Adaptability of Spathiphyllum floribundum and Chrysanthemum morifolium.

Light-emitting diodes (LEDs) can be programmed to provide specialized light sources and spectra for plant growth. UV-A (397.6 nm), blue (460.6 nm), green (520.7 nm), and red (661.9 nm) LED light sources were used to study the effects of different monochromatic lights on the growth, antioxidant system, and photosynthetic characteristics of Spathiphyllum floribundum 'Tian Jiao' (a shade-loving species) and Chrysanthemum morifolium 'Huang Xiu Qiu' (a sun-loving species). This research revealed that green and blue light could enhance the morphological indicators, Chl a/b, photosynthetic electron transfer chain performance, and photosystem activity of S. floribundum, blue and red light could enhance the solution protein, Chl a, and photosynthetic electron transfer chain performance of C. morifolium, red and UV-A light viewed the highest SOD and CAT activities of S. floribundum (275.56 U·min·g-1; 148.33 U·min·g-1) and C. morifolium (587.03 U·min·g-1; 98.33 U·min·g-1), respectively. Blue and green light were more suitable for the growth and development of the shade-loving plant S. floribundum, while red and blue light were more suitable for the sun-loving plant C. morifolium. UV-A light could be used for their stress research. The research revealed the different adaptation mechanism of different plants to light environmental conditions.

Response of Flavor Substances in Tomato Fruit to Light Spectrum and Daily Light Integral.

Light-emitting diodes (LEDs) have been widely used as light sources for plant production in plant factories with artificial lighting (PFALs), and light spectrum and light amount have great impacts on plant growth and development. With the expansion of the product list of PFALs, tomato production in PFALs has received attention, but studies on fruit quality influenced by artificial light are lacking. In this study, precisely modulated LED light sources based on white light combined with additional red, blue, and green lights were used to investigate the effects of light spectrum and daily light integral (DLI) on the main quality indicators and flavor substances of "Micro-Tom" tomato fruits. The highest sugar-acid ratio was obtained under the white light with addition of red light with high DLI and blue light with low DLI. The contents of β-carotene, lycopene, and lutein were significantly increased by higher DLI conditions except for under the blue light treatment, and the cross-interactions between the light spectrum and DLI were observed. The accumulation of the main flavor substances in tomato fruits was decreased by addition of green light with a high DLI and red light with a low DLI; notably, the percentage of 2-isobutylthiazole, which is associated with fresh tomato aroma, was decreased by green light. This study provides insights for improving tomato fruit quality and flavor by regulating light conditions in PFALs.

Ion-Dipole Interaction Enabling Highly Efficient CsPbI3 Perovskite Indoor Photovoltaics.

Metal halide perovskites are ideal candidates for indoor photovoltaics (IPVs) because of their easy-to-adjust bandgaps, which can be designed to cover the spectrum of any artificial light source. However, the serious non-radiative carrier recombination under low light illumination restrains the application of perovskite-based IPVs (PIPVs). Herein, polar molecules of amino naphthalene sulfonates are employed to functionalize the TiO2 substrate, anchoring the CsPbI3 perovskite crystal grains with a strong ion-dipole interaction between the molecule-level polar interlayer and the ionic perovskite film. The resulting high-quality CsPbI3 films with the merit of defect-immunity and large shunt resistance under low light conditions enable the corresponding PIPVs with an indoor power conversion efficiency of up to 41.2% (Pin : 334.11µWcm-2 , Pout : 137.66µWcm-2 ) under illumination from a commonly used indoor light-emitting diode light source (2956 K, 1062 lux). Furthermore, the device also achieves efficiencies of 29.45% (Pout : 9.80µWcm-2 ) and 32.54% (Pout : 54.34µWcm-2 ) at 106 (Pin : 33.84µWcm-2 ) and 522 lux (Pin : 168.21µWcm-2 ), respectively.

Research Control Devices for LED Light Sources under Their Operating Conditions at Elevated Temperatures

The electrical and light characteristics of light-emitting diodes (LEDs), upon which modern lighting devices are constructed, are significantly influenced by ambient temperature. As the temperature rises, the luminous flux of LEDs diminishes, and the lifespan of LED devices also decreases. The control devices (drivers) used in LED lighting systems, built based on current stabilization schemes, do not effectively stabilize the luminous flux when the ambient temperature fluctuates between +15 to +60 °C. The luminous flux declines as the temperature increases, even if the current supplied to the LEDs remains constant. This paper presents a comparative analysis of LED lighting devices equipped with drivers featuring current stabilization and those with drivers employing voltage stabilization for operation in higher temperature conditions.

Broadband near infrared luminescent properties of Cr3+ activated SrGa2Si2O8 phosphor

There has been a lot of interest in trivalent chromium ion-doped phosphors for near-infrared (NIR) luminescence in recent years. Here, trivalent chromium-doped NIR emitting SrGa2Si2O8 phosphors were synthesized. The electronic structure was calculated via density functional theory. Although only [SrO7], [SiO4], and [GaO4] polyhedra were found in the host, we still observe broadband luminescence of Cr3+ in the region of 650–950 nm from octahedra site. Due to the doping of Cr3+, a transformation from [GaO4] tetrahedron rearrange into [CrO6] octahedron was produced. The experimental results of X-ray photoelectron spectroscopy and electron paramagnetic resonance spectroscopy demonstrated the presence of Cr3+. A systematic study of the photoluminescence properties of SrGa2Si2O8:Cr3+ was conducted. The luminescent intensity of SrGa2Si2O8:0.005Cr3+ at 420 K can be retained at 83.42% compared to 300 K, indicating its high thermal stability. The electroluminescence of the prepared light emitting diode (LED) based on SrGa2Si2O8:Cr3+ and blue LED chip was measured under various currents. The application as a NIR LED light source was demonstrated in human hands.

Calculation and Selection of Spectral Characteristics of Radiation of LED Luminaires for Operation Rooms

Many researchers considered improvement of colour discrimination an important factor of surgery illumination, but none of them provided data on colour contrast estimation. The article describes the results of an extensive search of spectrum that are the most preferable for application in surgery equipment using selected light emitting diodes (LED) of different types. The search was not also based on the qualitative characteristics recommended by the standard, but also on a previously non-considered parameter: colour contrast between human tissues K estimated in uniform-chromaticity systems. The programme developed in MATLAB environment allows to model the cumulative spectrum of a LED light source, to determine the proportions of LED radiation or crystals in LED providing the maximum value of LED general colour rendering index Ra at the set correlated colour temperature or the maximum value of averaged K in uniform-chromaticity systems both in presence of the limited Ra value of 85 and if there are no limitations. Such options of spectrum search allowed to evaluate the probability of K change and its maximum, as well as to identify three possible operating modes of surgery equipment when using the said LEDs. The first of them is following the existing recommendations for Ra with possible insignificant change of K, the second one is the priority of K assuming violation of the Ra recommendations to increase K, and the third option assumes switching between the modes if necessary. LED spectra are selected for such different modes. Other colour rendering indexes are also estimated, and the authors recommend using the new standard TM‑30–15 for standardisation of the colour rendering quality of light sources used in surgery luminaires. It is based on 99 samples and some of the tests have reflective properties close to those of human tissues.

In Vitro Multiplication and Rooting of Plum Rootstock 'Saint Julien' (Prunus domestica subsp. insititia) under Fluorescent Light and Different LED Spectra.

In recent years, light emitting diodes (LEDs), due to their low energy consumption, low heat emission and specific wavelength irradiation, have become an alternative to fluorescent lamps (FLs) in plant tissue culture. The aim of this study was to investigate the effects of various LED light sources on the in vitro growth and rooting of plum rootstock Saint Julien (Prunus domestica subsp. insititia). The test plantlets were cultivated under a Philips GreenPower LEDs research module illumination system with four spectral regions: white (W), red (R), blue (B) and mixed (W:R:B:far-red = 1:1:1:1). The control plantlets were cultivated under fluorescent lamps (FL) and the photosynthetic photon flux density (PPFD) of all treatments was set at 87 ± 7.5 μmol m-2 s-1. The effect of light source on the selected physiological, biochemical and growth parameters of plantlets was monitored. Additionally, microscopic observations of leaf anatomy, leaf morphometric parameters and stomata characteristics were carried out. The results showed that the multiplication index (MI) varied from 8.3 (B) to 16.3 (R). The MI of plantlets grown under mixed light (WBR) was 9, lower compared to the control (FL) and white light (W), being 12.7 and 10.7, respectively. In addition, a mixed light (WBR) favored plantlets' stem growth and biomass accumulation at the multiplication stage. Considering these three indicators, we could conclude that under the mixed light, the microplants were of better quality and therefore mixed light (WBR) was more suitable during the multiplication phase. A reduction in both net photosynthesis rate and stomatal conductance in the leaves of plants grown under B were observed. The quantum yield (Yield = FV/FM), which represents the potential photochemical activity of PS II, ranged from 0.805 to 0.831 and corresponded to the typical photochemical activity (0.750-0.830) in the leaves of unstressed healthy plants. The red light had a beneficial effect on the rooting of plum plants; the rooting was over 98%, significantly higher than for the control (FL, 68%) and the mixed light (WBR, 19%). In conclusion, the mixed light (WBR) turned out to be the best choice during the multiplication phase and the red LED light was more suitable during the rooting stage.

Management of Indirect Hyperbilirubinemia; Comparison of Complications of Light Emitting Diode (LED) and Fluorescent Phototherapy

Objective: To compare the frequency of complications (hyperthermia, skin eruption, dehydration) of LED phototherapy and fluorescent phototherapy in management of indirect hyperbilirubinemia in neonates Material and methods: This randomized control study was carried out from 1st June 2015 to 31 December 2016 at NNU of The Children`s Hospital Lahore using Non probability consecutive sampling technique after getting informed consent from parents. All basic demographic information of each variable (name, age) was noted and entered on Performa. SPSS-18 was used to interpret the data. Results: In our study the mean age was 1.98±0.83 days. Skin rash complication was observed in 43(13%) cases, dehydration was found in 48(14.5%) cases and hyperthermia was noted in 65(19.70%) patients. Practical Implication: Many setups in Pakistan are still using conventional fluorescent phototherapy machines. LED has lesser side effects as compared to conventional one so by using LED light source we can lessen the adverse effects of phototherapy that will be beneficial to the babies Conclusion: LED light source is effective for phototherapy with significantly lesser complication rate (hyperthermia, skin eruption, and dehydration) compared to fluorescent phototherapy in management of indirect hyperbilirubinemia in neonates. In this study LED phototherapy significantly showed fewer complications as compared to fluorescent phototherapy cases. Keywords: LED, Fluorescent, Hyperthermia, Skin, Rash, Dehydration, Neonates, Hyperbilirubinemia

Differential protein response to different light quality conditions of industrial hemp cultivation based on DIA technology

Light quality plays a significant role in regulating plant growth, development, morphogenesis and physiological metabolism. Industrial hemp is a photophilic plant that is sensitive to light. Light quality directly affects the yield and quality of industrial hemp. In this study, ‘Yunma No.7′ was used as the experimental material, the light quality was regulated by a light-emitting diode (LED) light source, and Blue Light (BL) and Red Light (RL) with the best and worst promotional effects on growth, respectively, were set as the treatment conditions, with White Light (WL) used as a control. The physiological changes of industrial hemp under different light quality conditions were determined, and the protein stress mechanism of industrial hemp under different light quality conditions was analyzed using data-independent acquisition (DIA) proteomics technology. Through a liquid chromatography- electrospray ionization-tandem mass spectrometry (LC-ESI-MS/MS) analysis, 456 and 421 differentially expressed proteins were identified under RL and BL, respectively. Through a Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis, it was found that the differentially expressed proteins under RL and BL were significantly enriched in eight and four pathways, respectively. The growth of industrial hemp under BL(best light quality) was promoted mainly through the following mechanisms: enhancing the DNA repair capacity; synthesizing a large number of carotenoids to improve the photosynthetic rate; increasing the rate of auxin synthesis and starch accumulation; and accelerating lignification and plant nutrient absorption and utilization. The results provide a theoretical basis for light quality control in industrial hemp industrialization.

Broadband Near-Infrared Luminescence in Garnet Y3Ga3MgSiO12: Cr3+ Phosphors.

Broadband near-infrared (NIR) phosphors are the critical component of phosphor converted NIR light-emitting diode (LED) light sources. However, there are still a lack of NIR phosphors with excellent external quantum efficiency (EQE) and thermal stability. Here, we report a highly efficient broadband NIR phosphor Y3Ga3MgSiO12: Cr3+. The optimized phosphor yields an internal quantum efficiency (IQE) and an EQE of 79.9 and 33.7%, respectively. The integrated emission intensity still remains at 84.4% of that at room temperature when heated to 423 K. A broadband NIR LED lamp was made by combining as-prepared phosphor and a blue InGaN LED chip, which shows an output power of 89.8 mW with a photoelectric conversion efficiency of 17.1% driven at 525 mW input power. Our research provides a promising NIR phosphor with high efficiency broadband for the NIR light source.

Wearable devices for photodynamic therapy – A systematic review

Wearable devices for photodynamic therapy – A systematic review