Search Results (23)

To investigate whether blue-dominant spectra from end-of-day (EOD) lighting can regulate crop morphological and flowering responses, chrysanthemum (Chrysanthemum × morifolium; obligate short day), geranium (Pelargonium × hortorum; day neutral), calibrachoa (Calibrachoa × hybrida; facultative long day), and gerbera (Gerbera jamesonii; facultative short day) plants were grown under different light-emitting diode (LED) spectrum treatments from January to April 2020, in Guelph, Canada. The spectrum treatments were (1) no EOD lighting, (2) narrowband blue from LEDs (B), (3) a combination of narrowband blue, red, and far-red LEDs with a photon flux ratio of 47:3:1 (blue:red:far-red; BRFR). The B and BRFR treatments ran daily from 0.5 h to 4.5 h after dusk. Compared to the control without EOD lighting, chrysanthemum flower initiation was completely inhibited under BRFR. Flowering time was slightly delayed, but flower bud number increased under B. Side branch number, leaf area, and main stem length and diameter increased under B and BRFR. In the geranium B and BRFR did not affect flowering, but increased side branch number and length and diameter of the main stem. Both spectrum treatments promoted earlier flowering in the calibrachoa, but BRFR produced more flower buds. The calibrachoa aerial dry biomass and main stem length increased under B and BRFR. The gerbera leaf chlorophyll index and leaf thickness increased under BRFR. Both spectrum treatments increased the gerbera flower bud size, despite having little effect on flowering time. In all species, at least one of the LED treatments increased canopy size. Therefore, low levels of B or BRFR can be potentially used for EOD lighting to regulate the flowering and morphology of potted ornamentals. Full article

Integrated light-emitting diodes (LEDs) with waveguides play an important role in applications such as augmented reality (AR) displays, particularly regarding coupling efficiency optimization. Quantum dot light-emitting diodes (QLEDs), an emerging high-performance optoelectronic device, demonstrate substantial potential for next-generation display technologies. This study investigates the influence of microcavity modulation on the output of QLEDs coupled with a silicon nitride (SiNx) waveguide by simulating a white light QLED (W-QLED) with a broad spectrum and mixed RGB QDs (RGB-QLED) with a comparatively narrower spectrum. The microcavity converts both W-QLED and RGB-QLED emissions from broadband white-light emissions into narrowband single-wavelength outputs. Specifically, both of them have demonstrated wavelength tuning and full-width at half-maximum (FWHM) narrowing across the visible spectrum from 400 nm to 750 nm due to the microcavity modulation. The resulting RGB-QLED achieves a FWHM of 11.24 nm and reaches 110.76% of the National Television System Committee 1953 (NTSC 1953) standard color gamut, which is a 20.95% improvement over W-QLED. Meanwhile, due to the Purcell effect of the microcavity, the output efficiency of the QLED coupled with a SiNx waveguide is also significantly improved by optimizing the thickness of the Ag anode and introducing a tilted reflective mirror into the SiNx waveguide. Moreover, the optimal output efficiency of RGB-QLED with the tilted Ag mirror is 10.13%, representing a tenfold increase compared to the sample without the tilted Ag mirror. This design demonstrates an efficient and compact approach for the near-eye full-color display technology. Full article

Lighting from light-emitting diodes (LEDs) is one of the largest capital and operational expenses for indoor farms. While broad-waveband white LEDs are relatively inexpensive, their efficacy is lower than most narrow-band LEDs. This study aimed to determine how supplementing warm-white light with additional blue (400–499 nm), green (500–599 nm), red (600–699 nm), or far-red (700–750 nm) light influences lettuce (Lactuca sativa) growth and quality, and whether these effects are consistent across two photon flux densities (PFDs). We grew lettuce ‘Rouxai’ and ‘Rex’ under 90 or 180 µmol∙m⁻²∙s⁻¹ of warm-white light supplemented with 40 or 80 µmol∙m⁻²∙s⁻¹ of blue, green, red, far-red, or warm-white light. Supplemental far-red light increased biomass without reducing secondary metabolites. Supplemental red, far-red, and warm-white light maximized biomass, whereas additional blue light enhanced secondary metabolite concentrations and leaf coloration. Increasing the PFD increased biomass and phenolic content in ‘Rouxai’. Notably, spectral effects were consistent across PFD levels, suggesting that higher PFDs do not diminish spectral responses. These results demonstrate the potential of enriching white light to increase yield or quality in controlled-environment agriculture and provide insights for cost-effective commercial production. Full article

The sweet basil Ocimum basilicum L. is the subject of numerous studies and is cultivated as a food and ornamental plant. Moreover, O. basilicum could be useful in the prevention of stroke ischemia, and its anticancer properties were recently shown. Caffeic acid derivatives, such as rosmarinic acid (RA), chicoric acid, salvianolic acids, and anthocyanins, provide the medicinal properties of basil. Therefore, investigations of the optimal growth conditions that can provide cost-effective cultivation of highly productive basil plants are relevant and important. The aim of the present work was to study the effects of a combination of soil composition and light conditions on the morphological and biochemical characteristics of O. basilicum. In totally artificial (indoor) environments, light-emitting diodes (LEDs) may provide a broad range of narrowband wavelengths with different intensities. This technology can lower operating costs. In addition to the spectral composition, light intensity (PPFD, µmol m⁻²s⁻¹) is an important parameter for the optimal growth of plants. In the experiment, we used different spectra of LED lamps with intensities of 300 µmol m⁻²s⁻¹: warm white, monochromatic (green and red), and a combination of blue and red. Plants were grown under various lighting conditions in soil supplemented with fertilizer, Z-ion, and Crystallon. The results showed that supplementation of soil with Crystallon had a greater effect on the growth of both above- and below-ground parts of O. basilicum plants. Interestingly, growing O. basilicum plants under R and RB light led to a 2-fold increase in the biosynthesis of both the key caffeic acid derivative RA and anthocyanin. However, given that under RB light, there is no positive effect of Crystallon on growth, the productivity of RA and anthocyanin reached a maximum when O. basilicum plants were grown under R light and Crystallon. Under these conditions, the productivity of anthocyanins and caffeic acid derivatives in O. basilicum was more than eight times greater than that in untreated O. basilicum plants. Full article

In this study, a series of Sr₆LuAl(BO₃)₆:Sm³⁺ red phosphors were successfully prepared with a high-temperature solid-phase technology. The Rietveld refinement analysis of the X-ray diffraction (XRD) diffraction patterns indicated that the as-prepared phosphors belong to the $R\overline{3}$ space group of the hexagonal crystal system. Under 404 nm near-ultraviolet excitation, the Sr₆LuAl(BO₃)₆:Sm³⁺ phosphor exhibits narrowband emission within the range of 550 to 750 nm. The primary emission peak is observed at a wavelength of 599 nm, corresponding to ⁶H_5/2 → ⁴F_7/2. The optimum doping concentration of the Sr₆LuAl(BO₃)₆:xSm³⁺ phosphor is 10 mol%. Nearest-neighbor ion interaction is the mechanism of concentration quenching. The synthesized phosphors demonstrate exceptional thermal stability, with a high quenching temperature (T_0.5 > 480 K). Furthermore, the assembled white light-emitting diode (w-LED) device exhibits a low color temperature (5464 K), an excellent color rendering index (R_a = 95.6), and CIE coordinates (0.333, 0.336) close to those of standard white light. Collectively, these results suggest the enormous potential of Sr₆LuAl(BO₃)₆:Sm³⁺ phosphors for applications in w-LEDs. Full article

To address the issue of the lack of red light in traditional Ce³⁺: YAG-encapsulated blue LED white light systems, we utilized spark plasma sintering (SPS) to prepare spinel-based Cr³⁺-doped red phosphor ceramics. Through phase and spectral analysis, the SPS-sintered ZnAl₂O₄: 0.5%Cr³⁺ phosphor ceramic exhibits good density, and Cr³⁺ is incorporated into [AlO₆] octahedra as a red emitting center. We analyzed the reasons behind the narrow-band emission and millisecond-level lifetime of ZAO: 0.5%Cr³⁺, attributing it to the four-quadrupole interaction mechanism as determined through concentration quenching modeling. Additionally, we evaluated the thermal conductivity and thermal quenching performance of the ceramic. The weak electron-phonon coupling (EPC) effects and emission from antisite defects at 699 nm provide positive assistance in thermal quenching. At a high temperature of 150 °C, the thermal conductivity reaches up to 14 W·m⁻¹·K⁻¹, and the 687 nm PL intensity is maintained at around 70% of room temperature. Furthermore, the internal quantum efficiency (IQE) of ZAO: 0.5%Cr³⁺ phosphor ceramic can reach 78%. When encapsulated with Ce³⁺: YAG for a 450 nm blue LED, it compensates for the lack of red light, adjusts the color temperature, and improves the color rendering index (R9). This provides valuable insights for the study of white light emitting diodes (WLEDs). Full article

The satellite imagery of nighttime lights (NTLs) has been studied to understand human activities, economic development, and more recently, the ecological impact of brighter night skies. The Visible Infrared Imaging Radiometer Suite (VIIRS) Day–Night Band (DNB) offers perhaps the most advanced nighttime imaging capabilities to date, but its large pixel size and single band capture large-scale changes in NTL while missing granular but important details, such as lighting type and brightness. To better understand individual NTL sources in a region, the spectra of nighttime lights captured by the DLR Earth Sensing Imaging Spectrometer (DESIS) were extracted and compared against near-coincident VIIRS DNB imagery. The analysis shows that DESIS’s finer spatial and spectral resolutions can detect individual NTL locations and types beyond what is possible with the DNB. Extracted night light spectra, validated against ground truth measurements, demonstrate DESIS’s ability to accurately detect and identify narrow-band atomic emission lines that characterize the spectra of high-intensity discharge (HID) light sources and the broader spectral features associated with different light-emitting diode (LED) lights. These results suggest the possible application of using hyperspectral data from moderate-resolution sensors to identify lamp construction details, such as illumination source type and light quality in low-light contexts. NTL data from DESIS and other hyperspectral sensors may improve the scientific understanding of light pollution, lighting quality, and energy efficiency by identifying, evaluating, and mapping individual and small groups of light sources. Full article

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. Full article

The development of light-emitting diodes (LEDs) has led to an increase in the use of lighting regimes within medicine particularly as a treatment for dermatological conditions. New devices have demonstrated significant results for the treatment of medical conditions, including mild-to-moderate acne vulgaris, wound healing, psoriasis, squamous cell carcinoma in situ (Bowen’s disease), basal cell carcinoma, actinic keratosis, and cosmetic applications. The three wavelengths of light that have demonstrated several therapeutic applications are blue (415 nm), red (633 nm), and near-infrared (830 nm). This review shows their potential for treating dermatological conditions. Phototherapy has also been shown to be an effective treatment for allergenic rhinitis in children and adults. In a double-anonymized randomized study it was found that there was 70% improvement of clinical symptoms of allergic rhinitis after intranasal illumination by low-energy narrow-band phototherapy at a wavelength of 660 nm three times a day for 14 consecutive days. Improvement of oedema in many patients with an age range of 7–17 were also observed. These light treatments can now be self-administered by sufferers using devices such as the Allergy Reliever phototherapy device. The device emits visible light (mUV/VIS) and infra-red light (660 nm and 940 nm) wavelengths directly on to the skin in the nasal cavity for a 3 min period. Several phototherapy devices emitting a range of wavelengths have recently become available for use and which give good outcomes for some dermatological conditions. Full article

Currently, increasing attention has been focused on light-emitting diodes (LEDs)-induced photopolymerization. The common LEDs (e.g., LED at 365 nm and LED at 405 nm) possess narrow emission bands. Due to their light absorption properties, most commercial photoinitiators are sensitive to UV light and cannot be optimally activated under visible LED irradiation. Although many photoinitiators have been designed for LED-induced free radical polymerization and cationic polymerization, there is still the issue of the mating between photoinitiators and LEDs. Therefore, the development of novel photoinitiators, which could be applied under LED irradiation, is significant. Many photoinitiating systems have been reported in the past decade. In this review, some recently developed photoinitiators used in LED-induced photopolymerization, mainly in the past 5 years, are summarized and categorized as Type Ⅰ photoinitiators, Type Ⅱ photoinitiators, and dye-based photoinitiating systems. In addition, their light absorption properties and photoinitiation efficiencies are discussed. Full article

(1) Background: The use of light-emitting diode (LED) lighting is increasingly replacing traditional light sources in museums. There is a need to anticipate the damage caused by LED lighting to photographic prints. The aim of this study is to quantitatively predict fading on three inkjet color patches exposed to different white light LED; (2) Method: The novel approach of this work is to measure the wavelength-dependent photochemical efficiency on color patches using a narrow band LED. First, the color patches are exposed to narrow band LED lamps in a proprietary light chamber. Sensitivity curves are obtained by plotting the density changes caused by narrow band exposure as a function of the exposure. In the second step, action spectra are derived from the slopes of the sensitivity curves. The action spectra correspond to the rates of change of a color patch to exposure with different wavelengths of light. In the third step, the narrow band light emissions are fitted to the emission spectra of the white LED of interest. The fitting factors are used to calculate the weighted sum of the density changes; (3) The method predicts the absolute density change of color patches for several white light LED exposures. Full article

Indoor co-cultivation systems can answer to the need for sustainable and resilient food production systems. Rearing organisms under light-emitting diodes (LEDs) irradiation provides the possibility to control and shape the emitted light spectra. UV-B-irradiation (280–315 nm) can positively affect the nutritional composition of different plants and other organisms, whereas information on edible insects is scarce. To evaluate the potential effect of the photosynthetically active radiation (PAR) and LED-emitting LEDs on the rearing and nutritional quality of edible insects, house crickets (Acheta domesticus) were reared from the age of 21 days under controlled LED spectra, with an additional UV-B (0.08 W/m²) dose of 1.15 KJm² d⁻¹ (illuminated over a period for 4 h per day) for 34 days. UV-B exposure showed no harm to the weight of the crickets and significantly increased their survival by ca. 10% under narrowband UV-B treatment. The nutritional composition including proteins, fat and chitin contents of the insects was not affected by the UV-B light and reached values of 60.03 ± 10.41, 22.38 ± 2.12 and 9.33 ± 1.21%, respectively, under the LED irradiation. Therefore, house crickets can grow under LED irradiation with a positive effect of narrowband UV-B application on their survival. Full article

Zero-dimensional (0D) hybrid manganese halides have emerged as promising platforms for the white light-emitting diodes (w-LEDs) owing to their excellent optical properties. Necessary for researching on the structure-activity relationship of photoluminescence (PL), the novel manganese bromides (C₁₃H₁₄N)₂MnBr₄ and (C₁₃H₂₆N)₂MnBr₄ are reported by screening two ligands with similar atomic arrangements but various steric configurations. It is found that (C₁₃H₁₄N)₂MnBr₄ with planar configuration tends to promote a stronger electron-phonon coupling, crystal filed effect and concentration-quenching effect than (C₁₃H₂₆N)₂MnBr₄ with chair configuration, resulting in the broadband emission (FWHM = 63 nm) to peak at 539 nm with a large Stokes shift (70 nm) and a relatively low photoluminescence quantum yield (PLQY) (46.23%), which makes for the potential application (LED-1, Ra = 82.1) in solid-state lighting. In contrast, (C₁₃H₂₆N)₂MnBr₄ exhibits a narrowband emission (FWHM = 44 nm) which peaked at 515 nm with a small Stokes shift (47 nm) and a high PLQY of 64.60%, and the as-fabricated white LED-2 reaches a wide colour gamut of 107.8% National Television Standards Committee (NTSC), thus highlighting the immeasurable application prospects in solid-state display. This work clarifies the significance of the spatial configuration of organic cations in hybrids perovskites and enriches the design ideas for function-oriented low-dimensional emitters. Full article

Previous studies have demonstrated that light quality critically affects plant development and growth; however, the response depends upon the plant species. This research aims to examine the effects of different light wavelengths on sunflower (Helianthus annuus) sprouts that were stimulated during the night. Natural light and narrow-band light-emitting diodes (LEDs) were used for an analysis of sunflower sprouts grown under full light and specific light wavelengths. Sunflower seeds were germinated under different light spectra including red, blue, white, and natural light. Luminosity, temperature, and humidity sensors were installed in the plant nursery and remotely monitored and recorded by an Internet of Things (IoT) device. The experiment examined seed germination for seven days. The results showed that the red light had the most influence on sunflower seed germination, while the natural light had the most influence on the increase in the root and hypocotyl lengths. Full article

In many countries of Europe and Eastern Asia, watermelon production is mainly based on the use of grafted seedlings. Upon grafting, seedlings undergo a period of healing where artificial lighting is provided by light-emitting diodes in controlled chambers in order to accelerate and improve the healing process. The objective of our study was to test the effect of light quality on the final product (i.e., seedlings ready for transplanting) in the nursery, as well as to evaluate the possible implications on fruit quality after field cultivation. Narrow-band blue (B) and red (R) wavelengths, 64–36% R-B (36B), 76–24% R-B (24B), 88–12% R-B (12B), and 83–12% R-B plus 5% far-red (12B+FR) wavelengths were tested. 12B+FR enhanced the root dry weight, root architecture, and maximum photosynthetic rate, while RB combinations generally showed better root system development with increased blue portion. R light induced inferior root dry weight and quality indices (root/shoot and shoot–dry–weight/length ratios), lower gas exchange parameters, and chlorophyll content, but high shoot length and leaf area. B light led to inferior root architecture, lower stem diameter, leaf area, and maximum photosynthetic rate. Both R and B wavelengths showed decreased concentration of macronutrients and trace elements. After field cultivation, fruit quality (i.e., morphology and color), and valuable nutritive characteristics (i.e., phenolics, carotenoids, lycopene, antioxidants) maintained high quality irrespective of light treatments. Overall, 12B+FR performed well in almost all qualitative parameters including the morphology, the root development, and photosynthesis, while also maintaining high fruit quality. Full article