LED Illumination Research Articles

Light-stimulated insulin secretion from pancreatic islet-like organoids derived from human pluripotent stem cells

Optogenetic techniques permit non-invasive, spatiotemporal, and reversible modulation of cellular activities. Here, we report a novel optogenetic regulatory system for insulin secretion in human pluripotent stem cell (hPSC)-derived pancreatic islet-like organoids using monSTIM1 (monster-opto-Stromal interaction molecule 1), an ultra-light-sensitive OptoSTIM1 variant. The monSTIM1 transgene was incorporated at the AAVS1 locus in human embryonic stem cells (hESCs) by CRISPR-Cas9-mediated genome editing. Not only were we able to elicit light-induced intracellular Ca2+ concentration ([Ca2+]i) transients from the resulting homozygous monSTIM1+/+-hESCs, but we also successfully differentiated them into pancreatic islet-like organoids (PIOs). Upon light stimulation, the β-cells in these monSTIM1+/+-PIOs displayed reversible and reproducible [Ca2+]i transient dynamics. Furthermore, in response to photoexcitation, they secreted human insulin. Light-responsive insulin secretion was similarly observed in monSTIM1+/+-PIOs produced from neonatal diabetes (ND) patient-derived induced pluripotent stem cells (iPSCs). Under LED illumination, monSTIM1+/+-PIO-transplanted diabetic mice produced human c-peptide. Collectively, we developed a cellular model for the optogenetic control of insulin secretion using hPSCs, with the potential to be applied to the amelioration of hyperglycemic disorders.

Optical bandgap variation and photo-Fenton property evolution in Fe-doped Bi2YO4Cl

The current study addresses the existing research gap on the effects of transition metal doping in layered Bi2YO4Cl and searches for a new visible light photocatalyst in the bismuth-based oxychloride system. The extent of Fe substitution in place of Y in Bi2YO4Cl and its consequences on the structure, optical, and catalytic properties have been examined by synthesizing the samples using a solution combustion method. Nearly 20 mol% of Fe could be introduced in a monophasic layer structural arrangement. The Fe-containing samples have also been characterized by electron microscopic and vibrational spectroscopic techniques. The optical absorbance shifted to the visible region with the Fe inclusion, and the bandgap decreased from 2.40 eV (pristine) to 1.77 eV (20 mol % Fe-substituted). XPS analysis of the Fe-containing sample indicated that Fe existed majorly in the III oxidation state with traces of the II oxidation state. The photo-Fenton function of Bi2Y1-xFexO4Cl (x = 0.10 and 0.20) for the oxidative degradation of RhB and MB dye molecules under LED illumination has been demonstrated. From scavenger experiments, OH• radicals and holes have been identified as the reactive oxidation species (ROS) involved in these reactions. The catalyst showed recyclability and structural integrity.

LED Technology Applied to Plant Development for Promoting the Accumulation of Bioactive Compounds: A Review

Light is an important environmental factor for plants. The quality of light and the wavelength stimulate enzyme activation, regulate enzyme synthesis pathways and promote bioactive compound accumulation. In this respect, the utilization of LED light under controlled conditions in agriculture and horticulture could be the most suitable choice for increasing the nutritional values of various crops. In recent decades, LED lighting has been increasingly used in horticulture and agriculture for commercial-scale breeding of many species of economic interest. Most studies on the influence of LED lighting on the accumulation of bioactive compounds in any type of plants (horticultural, agricultural species or sprouts) and also biomass production, were carried out in growth chambers under controlled conditions, without natural light. Illumination with LED could be a solution for obtaining an important crop with maximum efficiency, with a high nutritional value and minimum effort. To demonstrate the importance of LED lighting in agriculture and horticulture, we carried out a review based on a large number of results cited in the literature. The results were collected from 95 articles and were obtained using the keyword LED combined with plant growth; flavonoids; phenols; carotenoids; terpenes; glucosinolates; food preservation. We found the subject regarding the LED effect on plant growth and development in 11 of the articles analyzed. The treatment of LED on phenol content was registered in 19 articles, while information regarding flavonoid concentrations was revealed by 11 articles. Two articles we reviewed debate the accumulation of glucosinolates and four articles analyzed the synthesis of terpenes under LED illumination and 14 papers analyzed the variation in content of carotenoids. The effect of LED on food preservation was reported in 18 of the works analyzed. Some of the 95 papers contained references which included more keywords.

Sensor simulation using a spectrum tunable LED system.

This study developed a method to simulate the sensor responses and verify the effectiveness on spectral reconstruction by a spectrum tunable LED system. Studies have shown that the spectral reconstruction accuracy could be improved by including multiple channels in a digital camera. However, the real sensors with designed spectral sensitivities were hard to manufacture and validate. Therefore, the presence of a quick and reliable validation mechanism was preferred when performing evaluation. In this study, two novel approaches, i.e., channel-first and illumination-first simulations, were proposed to replicate the designed sensors with the use of a monochrome camera and a spectrum-tunable LED illumination system. In the channel-first method, the spectral sensitivities of three extra sensor channels were optimized theoretically for an RGB camera and then simulated by matching the corresponding illuminants in the LED system. The illumination-first method optimized the spectral power distribution (SPD) of the lights using the LED system, and the extra channels could be determined accordingly. The results of practical experiments showed that the proposed methods were effective to simulate the responses of the extra sensor channels.

Influence of Lightpipes on Readers for Microtubes Fluorescence Detection

Lightpipes are light guides based on total internal reflection used for LED illumination systems with many applications. This work investigates using lightpipes in a fluorescent reader for microtubes. It is part of a project to develop an RT-RPA multiplex test and fluorescence reader for SARS-COV 2 and H1N1. We investigated the lightpipes interaction with an excitation filter. The results do not show a benefit in using them on the emission side due to the capture of LED scattered light.

Comprehensive Modelling for Analyzing the Power Conversion Efficiency of Polycrystalline Silicon Photovoltaic Device under Indoor Operating Conditions

Recently, most of the studies were mainly focused on the variation between outdoor solar spectral irradiance and standard AM1.5G spectrum, as well as their effects towards the performances of different PV technologies. Interestingly, limited studies have been conducted to study the effect of artificial lighting on the power conversion efficiency of the photovoltaic (PV) device. The spectral irradiance produced by indoor lighting differs significantly as compared to the that of standard AM1.5G spectrum, which inevitably leads to different performances of the PV under standard test conditions and under artificial lighting exposure. In this study, the performance modelling has been carried out based on the comprehensive method proposed by Chong et al. to predict the PCE of organic solar cell devices. From the measurement results, the spectrum of LED illumination has been compared with that of AM1.5G, in which the LED shows a relatively narrow band with significant peaks at 450 and 560 nm. Furthermore, the theoretical model has been successfully validated by comparing the simulated PCE and the measured PCE at reasonably deviations in the range of 3.0 – 23.3%.

Light and Climate: Regulatory Requirements and Practice of Cultural Valuables Preservation

The article presents the set of data related to development of museum illumination control standards. The main goal of the review is to demonstrate the balance between illumination adjustment as a means to improve preservation of museum exhibits and adjustment as a means to improve presentation of exhibits to visitors. Such review became necessary due to intensification of activities for development of museum illumination regulations since 2018. As part of these activities, the specialists of two leading organisations – light engineers of the Russian Lighting Research Institute named after S.I. Vavilov (VNISI) and the museum and restoration community of the State Research Institute for Restoration – fulfilled a contract for analysis of museum practice in the sphere of museum illumination. The results of the studies under the contract were reviewed and approved during an extended meeting of the museum illumination commission of the Scientific and Technical Council of the Lighting Industry in the Russian Federation (STC “Svetotekhnika”) with participation of representatives of the museum community. The results of this work were also discussed at a meeting of the scientific council of GosNIIR. In 2020, specialists of VNISI developed four regulations of LED illumination for museums after fulfilling the contract. The article presents a brief description of the potential of these documents for improvement of development of LED museum illumination. It demonstrates limited applicability of the developed standards to actual needs of museums and the mistakes made by the developers, which pose risks for preservation of museum exhibits if these standards are used in practice. The author proposes the ways of further development and improvement of the regulatory framework of museum illumination. These ways and the programme of regulation development were discussed and approved at the meeting of the scientific council of GosNIIR.

Concentration Dependence of Optical Transmission and Extinction of Different Diatom Cultures

Diatoms are unicellular microalgae enclosed in a hierarchically structured silica cell wall that play a significant role in maintaining the health of the planet’s ecosystem. As one of the main photosynthesizers, they are responsible for 20–25% of the world’s oxygen release and carbon fixation. In order to develop technologies for the efficient extraction of carbon dioxide, for example, using bioreactors that provide optimal conditions for the growth of diatoms, it is also necessary to effectively track the diatom lifecycle, as well as control parameters that affect their growth. Here we offer a simple device consisting of LED illumination with a central wavelength of 505 nm that allows to monitor changes in diatom concentrations. We examined marine centric and freshwater pennate diatom strains with different morphologies, sizes, and volumes and obtained a linear dependence of the measured transmission on the concentration. The results were compared with the spectrophotometric approach, which showed a higher inaccuracy with respect to the linear fit. We believe that such an optical setup can be used to solve the problems of continuous flow monitoring of algae both in bioreactors as well as in their natural environment.

De-doping buried interface in p-i-n perovskite solar cells by utilizing compositional heterogeneity in depth

Compositional heterogeneity in halide perovskite materials often leads to undesired physiochemical properties of the materials that hampers device efficiency and stability. In a perovskite film prepared via conventional 2-step method, we find excess PbI2 are prone to locate at surface and buried interfaces, resulting in negative-type self-doping. To tailor this band alignment unfavored for p-i-n devices, we pre-deposited pyrrolidinium hydroiodide to react with residual PbI2 at buried interface. It not only de-dopes the perovskite to obtain the desired band alignment, but also passivates negative-type defects, which improves the device efficiency and stability. Consequently, the target planar p-i-n PSCs achieve an efficiency of 24.5 % (certified 23.2 %) and a remarkable photostability with 13 % efficiency decline for 2800 h under 1-Sun white LED illumination. It is so far among the highest-efficiency p-i-n PSCs via 2-step fabrication. Therefore, we suggest an interface de-doping strategy to fabricate highly efficient and stable PSCs.

The Light-Controlled Release of 2-fluoro-l-fucose, an Inhibitor of the Root Cell Elongation, from a nitrobenzyl-caged Derivative.

Glycan metabolic engineering is a powerful tool for studying the glycosylation in living plant cells. The use of modified monosaccharides such as deoxy or fluorine-containing glycosides has been reported as a powerful pharmacological approach for studying the carbohydrate metabolism. 1,3,4-tri-O-acetyl-2-fluoro-l-fucose (2F-Fuc) is a potent inhibitor of the plant cell elongation. After feeding plant seedlings with 2F-Fuc, this monosaccharide derivative is deacetylated and converted by the endogenous metabolic machinery into the corresponding nucleotide-sugar, which then efficiently inhibits Golgi-localized fucosyltransferases. Among plant cell wall polymers, defects in the fucosylation of the pectic rhamnogalacturonan-II cause a decrease in RG-II dimerization, which in turn induce the arrest of the cell elongation. In order to perform the inhibition of the cell elongation process in a spatio-temporal manner, we synthesized a caged 3,4-di-O-acetyl-1-hydroxy-2-fluoro-l-fucose (1-OH-2F-Fuc) derivative carrying a photolabile ortho-nitrobenzyl alcohol function at the anomeric position: 3,4-di-O-acetyl-1-ortho-nitrobenzyl-2-fluoro-l-fucose (2F-Fuc-NB). The photorelease of the trapped 1-OH-2F-Fuc was performed under a 365 nm LED illumination. We demonstrated that the in planta elimination by photoexcitation of the photolabile group releases free 2F-Fuc in plant cells, which in turn inhibits in a dose-dependent manner and, reversibly, the root cell elongation.

Lensless holographic microscope with a time and memory-saving algorithm for large-volume imaging of organoids.

Organoids, the 3D culture systems derived from stem cells, are promising models for human organs. However, organoid study requires large-volume imaging with single cell resolution, which is beyond the spatial bandwidth limit of conventional optical microscopy. Herein, we propose a lensless holographic microscope empowered with a time and memory-saving algorithm. It solves the trade-off between the imaging field of view, resolution, and processing speed, and provides a practical tool for the study of organoids. We first build a compact microscopy system using a multi-angle LED illumination scheme and an on-chip structure. Then we develop a fast angular spectrum formula for fast reconstruction of oblique-illuminated coaxial holography under the under-sampling condition. Additionally, we derive a multi-angle illuminated filtered backpropagation algorithm to achieve high-precision and slice-wise recovery of 3D structures of objects. The reconstruction process demands only 1/50 of the memory required by a traditional optical diffraction tomography algorithm. Experimental results indicate that the proposed method can achieve 6.28 mm × 4.71 mm × 0.37 mm volume imaging within 104 s. Through the standardized polystyrene beads test, we demonstrate that the proposed microscope has micrometer-scale resolution in both lateral and axial directions. In addition, the 3D imaging results of salivary gland organoids show great application prospects of the proposed method in the field of living biological sampling imaging.

Effect of White Light-Emitting Diode Illuminants Recommended by the CIE on Colors of Dental Ceramic Materials

The aim of this study was to evaluate color inconstancy of dental ceramics under the white light-emitting diode illuminants recently proposed by the CIE. From spectral reflectance factors of 18 dental ceramics (VST, NSP, and IEC; shades A1, A2, A3, A3.5, B2, and C2), the corresponding colors under illuminant D65 and CIE 1931 Standard Colorimetric Observer were computed for all samples, using the chromatic adaptation transform CIECAT16. CIEDE2000 color differences between dental ceramics illuminated by CIE D65 standard illuminant and different white LED illuminants were calculated. Perceptibility and acceptability thresholds (PT00 and AP00) in dental ceramics were used to analyze color changes. Color gamut size was within the same range for all illuminants and for all ceramics, since MCDM computed values were 4.1–4.4 for VST, 4.0–4.2 for NSP, and 4.3–4.6 for IEC. For all ceramics and shades, the color inconstancies were higher than 50:50% PT00 and, in general, lower than 50:50% AT00. The effect of CIE-proposed LED illuminants on dental ceramic is perceptible and slightly lower than on natural teeth. Dental clinicians should consider these lighting effects on the visual appearance of dental ceramics.

Vacuum co-evaporated wide-bandgap perovskite films for highly-efficient indoor photovoltaic cells and modules

The wide-bandgap perovskite films are conductive to deliver high-efficiency indoor photovoltaic devices, due to its easy spectral matching with artificial light sources. But now, the wide-bandgap perovskite films are usually fabricated by spin coating, which is difficult to achieve large-area mass manufacturing and thus limits its application. In this work, combined with substrate modification and component regulation, high-quality wide-bandgap (1.77 eV) perovskite films were fabricated by vacuum deposition. The optimal device achieved a power conversion efficiency (PCE) of 30.25% under 1000 lx LED illumination, more than 84% of the initial PCE was maintained after 53 days of aging. Furthermore, the module with an aperture area of 67.08 cm2 achieved the PCE of 13.25% and 9.70% under 1000 lx LED illumination and 1-sun AM1.5 G illumination, respectively.

Porphyrin-Moiety-Functionalized Metal–Organic Layers Exhibiting Catalytic Capabilities for Detoxifying Nerve Agent and Blister Agent Simulants

The development of very efficient bifunctional catalysts for the simultaneous detoxification of two kinds of the deadliest chemical warfare agents (CWAs), nerve agent and blister agent, is highly desirable. In this study, two porphyrin-based ligands [tetrakis(4-carboxyphenyl) porphyrin (TCPP) and protoporphyrin IX (PPIX)] are introduced into 2D Zr-1,3,5-tris(4-carboxyphenyl)benzene (BTB) metal-organic layers (MOLs), composed of six-connected Zr6 nodes and the tritopic carboxylate ligand BTB, by a solvent-assisted ligand incorporation method. The loads of TCPP and PPIX are 6.4 and 10.9 wt %, respectively. The detoxification of simulants of the nerve agent and the blister agent was conducted to investigate the catalytic activity of porphyrin-moiety-functionalized MOLs. The reaction half-life of optimal TCPP-functionalized MOL catalyzing the hydrolysis of a nerve agent simulant is only 2.8 min, meanwhile, the half-life of the selective catalytic oxidation of a blister agent simulant is only 1.2 min under LED illumination. More importantly, such a degradation half-life is only about 4 min under natural sunlight (∼60 mW/cm2). To our knowledge, TCPP-functionalized MOL is by far the most efficient catalyst for blister agent simulant degradation under solar light. Therefore, 2D ultrathin MOLs on demand appear to be a promising and efficient material platform for the development of bifunctional catalysts for CWA protection.

3D head-up display with a multiple extended depth of field based on integral imaging and holographic optical elements.

We propose a 3D head-up display with a multiple extended depth of field based on integral imaging and holographic optical elements (HOEs). The system consists of two components, an integral imaging module for generating 3D target objects and a holographic combiner for off-axis diffraction and image magnification. By recording HOEs with different optical powers at different locations on the same recording material, 3D imaging at multiple depth ranges is achieved. The designed and built HUD prototype verifies the feasibility of the method. The center depth planes of the red and green 3D images are at 600 mm and 2200 mm. The theoretical depth magnifications of the red and green channels are 1.5 and 5.5, and the measured depth ranges are approximately 250 mm and 850 mm. In addition, the influencing factors and improvement methods of resolution in LED illumination or laser illumination are analyzed.

Silver nanoparticles with exceptional near-infrared absorbance for photoenhanced antimicrobial applications.

In this work, we outline a simple method for synthesizing decahedral and triangular silver nanoparticles using light to tune particle shape and spectral characteristics. Notably, we were able to generate triangular silver nanoparticles with exceptional absorbance in the near-infrared (NIR) region, with high spectral overlap with the biological window, making them particularly promising for biological applications. We further demonstrate that under complementary LED illumination, these excitable plasmonic particles display exceptional antibacterial properties, several orders of magnitude more potent than similar particles under dark conditions or under illumination that does not match particle absorbance. This work demonstrates the powerful effects that LED lights can have on the antibacterial activity of AgNPs, providing an inexpensive and easily implemented route to unlocking the full potential of AgNPs in photobiological applications.

Highlights from the Detroit SID Vehicle Display Symposium and Exposition

Highlights from the Detroit SID Vehicle Display Symposium and Exposition

Sr/Ba substitution induced higher thermal stability far red-emitting Ba1-ySryLaLiWO6:Mn4+ phosphors for plant growth applications.

A series of red-emitting BaLaLiWO6:Mn4+ (BLLW:Mn4+) phosphors were successfully synthesized by a high-temperature solid-state reaction method. The crystal structure and luminescence properties of the obtained samples were systematically investigated. The emission spectra exhibited a deep red emission band peaking at 716 nm with a full width at half-maximum (FWHM) of 44 nm under 340 nm excitation. The optimal Mn4+ molar concentration was about 1.2%. In addition, the luminescence mechanism was analyzed using a Tanabe Sugano energy level diagram. With the substitution of Sr for Ba, there was a red shift in the emission spectrum and a blue shift in the excitation spectrum. The emission intensity of BLLW:1.2%Mn4+ at 150 °C was about 22% of the initial value at room temperature. In contrast, the emission intensity of SrLaLiWO6:1.2%Mn4+ still maintained 79% of the initial emission intensity at room temperature at 150 °C. This was due to the fact that with the substitution of Sr for Ba, the W-O bond length gradually decreases, which gradually enhanced the crystal field strength of Mn4+.

Broad-spectrum photocatalytic tetracycline degradation performance of an in-situ plasmonic Bi nanoparticle doped 0D/2D Z scheme heterostructure

Fabrication of broad-spectrum (UV–vis-NIR) active photocatalysts for effectively harnessing the abundant NIR light in the solar spectrum is the biggest challenge. Herein, the facile one-pot solid-state synthesis of an in-situ plasmonic bismuth-doped 0D/2D Z scheme heterostructure (BS) by loading Bi2O3 quantum dots (B) on 2D SnO2 nanosheets (S) is reported. The successful heterostructure fabrication was confirmed using various characterization techniques. The composites demonstrated excellent broad-spectrum photocatalytic degradation efficacy toward TC. When irradiated with an 18 W LED, the 2BS composite exhibited a 35.1 and 2.03-fold increased TC degradation rate co-efficient compared to S and B, respectively. Further, the 2BS composite showed a 5.5 times higher degradation rate constant than B after NIR light irradiation. Moreover, the composite displayed commendable stability after a four-cycle recycling experiment. At last, a plausible charge transfer mechanism under LED and NIR light illumination has been proposed following the results of the radical trapping experiment.

Chitosan enhances antibacterial efficacy of 405 nm light-emitting diode illumination against Escherichia coli O157:H7, Listeria monocytogenes, and Salmonella spp. on fresh-cut melon

This study aimed to evaluate the influence of chitosan on the antibacterial efficacy of 405 nm LED illumination against Escherichia coli O157:H7, Salmonella spp., and Listeria monocytogenes on fresh-cut melons. The antibacterial efficacy of LED illumination (a total dose of 1.3 kJ/cm2) with or without chitosan (0.5 and 1.0 %) against these three pathogens was determined at 4 and 10 °C, respectively. Non-illuminated and chitosan-treated fruits were stored in the dark for 36 h under the same temperature. Color changes, ascorbic acid content, and total flavonoid content of illuminated and non-illuminated fruits were also analyzed. The results showed that the populations of all three pathogens on the non-illuminated and chitosan-treated fruits remained unchanged during storage. Regardless of bacterial species and chitosan concentrations, LED illumination in combination with chitosan greatly reduced the bacterial populations by 1.5 – 3.5 log/cm2, which was greater than LED illumination alone. Among the three pathogens, L. monocytogenes was the most susceptible to chitosan-mediated LED illumination. However, the whiteness index of illuminated fruits significantly increased by 1.3-fold compared to that of non-illuminated fruits, regardless of the presence of chitosan. Unlike color, no significant difference was observed in ascorbic acid and total flavonoid contents between illuminated and non-illuminated fruits. Although the fruit color was changed by LED illumination, these results indicate that adding chitosan could enhance the antibacterial efficacy of 405 nm LED illumination against major foodborne pathogens on fresh-cut melons without changing nutritional quality.