scholarly journals Irradiance from Distinct Wavelength Light-emitting Diodes Affect Secondary Metabolites in Kale

HortScience ◽  
2008 ◽  
Vol 43 (7) ◽  
pp. 2243-2244 ◽  
Author(s):  
Mark G. Lefsrud ◽  
Dean A. Kopsell ◽  
Carl E. Sams
Keyword(s):  
Secondary Metabolites ◽  
Light Emitting Diodes ◽  
Dry Mass ◽  
Plant Production ◽  
Great Promise ◽  
Vegetable Crops ◽  
Light Emitting ◽  
Maximum Accumulation ◽  
Wavelength Control ◽  
Mass Basis

The use of light-emitting diodes (LEDs) for plant production is a new field of research that has great promise to optimize wavelength-specific lighting systems for precise management of plant physiological responses and important secondary metabolite production. In our experiment, hydroponically cultured kale plants (Brassica oleracea L. var. acephala D.C.) were grown under specific LED wavelength treatments of 730, 640, 525, 440, and 400 nm to determine changes in the accumulation of chlorophylls, carotenoids, and glucosinolates. Maximum accumulation, on a fresh mass basis, of chlorophyll a and b and lutein occurred at the wavelength of 640 nm, whereas β-carotene accumulation peaked under the 440-nm treatment. However, when lutein was measured on a dry mass basis, maximum accumulation was shifted to 440 nm. Sinigrin was the only glucosinolate to respond to wavelength treatments. Wavelength control using LED technology can affect the production of secondary metabolites such as carotenoids and glucosinolates with irradiance levels also a factor in kale. Management of irradiance and wavelength may hold promise to maximize nutritional potential of vegetable crops grown in controlled environments.

scholarly journals Biomass Production and Pigment Accumulation in Kale Grown Under Increasing Photoperiods

HortScience ◽  
2006 ◽  
Vol 41 (3) ◽  
pp. 603-606 ◽  
Author(s):  
Mark G. Lefsrud ◽  
Dean A. Kopsell ◽  
Robert M. Augé ◽  
A.J. Both
Keyword(s):  
Biomass Production ◽  
Dry Mass ◽  
Fresh Mass ◽  
Vegetable Crops ◽  
Maximum Accumulation ◽  
Excellent Source ◽  
Pigment Accumulation ◽  
Mass Basis ◽  
Maximum Biomass Production ◽  
Β Carotene

Consumption of fruit and vegetable crops rich in lutein and β-carotene carotenoids is associated with reduced risk of cancers and aging eye diseases. Kale (Brassica oleracea L. var. acephala D.C.) ranks highest for lutein concentrations and is an excellent source of dietary carotenoids. Kale plants were grown under varied photoperiods to determine changes in the accumulation of fresh and dry biomass, chlorophyll a and b, and lutein and β-carotene carotenoids. The plants were cultured in a controlled environment using nutrient solutions under photoperiod treatments of 6, 12, 16, or 24 hours (continuous). Fresh and dry mass production increased linearly as photoperiod increased, reaching a maximum under the 24-hour photoperiod. Maximum accumulation of lutein, β-carotene, and chlorophyll b occurred under the 24-h photoperiod at 13.5, 10.4, and 58.6 mg/100 g fresh mass, respectively. However, maximum chlorophyll a (235.1 mg/100 g fresh mass) occurred under the 12-hour photoperiod. When β-carotene and lutein were measured on a dry mass basis, the maximum accumulation was shifted to the 16-hour photoperiod. An increase in photoperiod resulted in increased pigment accumulation, but maximum concentrations of pigments were not correlated with maximum biomass production.

scholarly journals Solvent regulation synthesis of single-component white emission carbon quantum dots for white light-emitting diodes

2021 ◽  
Vol 10 (1) ◽  
pp. 465-477
Author(s):  
Longshi Rao ◽  
Qing Zhang ◽  
Mingfu Wen ◽  
Zhongfa Mao ◽  
Huaxian Wei ◽  
...  
Keyword(s):  
Quantum Dots ◽  
White Light ◽  
Light Emitting Diodes ◽  
Carbon Quantum Dots ◽  
Single Component ◽  
Great Promise ◽  
Solvent Engineering ◽  
Light Emitting ◽  
White Emission ◽  
White Light Emitting Diodes

Abstract White light-emitting diodes (WLEDs) hold great promise in lighting, display, and visible light communication devices, and single-component white emission carbon quantum dots (SCWE-CQDs) as the key component of WLEDs have many outstanding advantages. However, rapid and efficient synthesis of SCWE-CQDs with high photoluminescence quantum yield (PLQY) and stability remains challenging. Here, we report a novel solvent engineering strategy to obtain highly photoluminescent SCWE-CQDs by controlling the dilution ratios between N,N-dimethylformamide (DMF) and pristine red carbon quantum dots (RCQDs) solution. By optimizing synthesis conditions, the relative PLQY of the SCWE-CQDs solution reached 53%. Morphological, structural, and optical property characterizations indicate that the combined action of the hydrogen bond (HB) effect and the size effect leads to the blue shift of RCQDs, but the HB effect is more dominant than the particle size in causing large spectral shifts. In addition, the WLEDs with high color rendering index of 89 and remarkable reliability were obtained based on the highly photoluminescent SCWE-CQDs. This facile solvent engineering approach for synthesizing tunable emission CQDs will promote the progress of carbon-based luminescent materials for applications in optoelectronic devices.

Electrically and Optically Detected Electron Paramagnetic Resonance in Blue Organic Light Emitting Diodes

2021 ◽  
Author(s):  
◽  
Rebecca Jane Sutton
Keyword(s):  
Electron Paramagnetic Resonance ◽  
Light Emitting Diodes ◽  
Organic Light Emitting Diodes ◽  
Great Promise ◽  
Paramagnetic Resonance ◽  
Light Emitting ◽  
Emissive Layer ◽  
Organic Light ◽  
Optically Detected ◽  
Electron Paramagnetic

<p>Organic light emitting diodes (OLEDs) are an emerging technology based on electrically conducting polymer films, with great promise for large area lighting and flexible ultra-thin displays. However, despite the rapid technological development, there is still a poor understanding of the degradation and spindependent recombination processes that take place inside an OLED. In this thesis, Electron Paramagnetic Resonance (EPR) was used to investigate these processes in blue-emitting OLEDs.  A successful procedure was developed and refined for fabricating OLEDs with the structure ITO/PEDOT:PSS/emissive layer/Al/Ag, with and without the PEDOT:PSS hole-transporting layer. The organic emissive layer was either F8BT, PFO, or PVK:OXD-7:FIrpic (PB). These OLEDs were fabricated in air and with a geometry optimised for EPR experiments. Critical features for satisfactory devices were found to be a sufficiently thick organic layer and minimal exposure to the air.  A compact apparatus was developed for simultaneous light output, current, and voltage measurements on the OLEDs while in an inert glove box environment. Electroluminescence and current-voltage parameters measured for these devices showed predominantly trap-controlled space-charge-limited conduction.   OLEDs with PFO as the emissive layer and with a PEDOT:PSS layer were investigated with conventional, electrically-detected (ED) and optically-detected (OD) EPR techniques. EDEPR and ODEPR signals were observed at ~9.2 GHz and in the low (<50 mT) and high (~330 mT) magnetic field regimes and were found to change markedly with time during operation as the device degraded. The low field signals initially showed a composite broad quenching and superimposed narrow enhancing response centred around zero field strength. These signals were attributed to magneto-resistance (MR) and magneto-electroluminescence (MEL). Following operational ageing, a third, narrow quenching line was observed in the MR and the ratio of the initial two MR responses changed substantially. These effects are tentatively attributed to a hyperfine interaction.  For both EDEPR and ODEPR, quenching high field resonances with a g-value (gyromagnetic ratio) of 2.003±0.001 were observed. The current-quenching resonance gradually diminished during operation and after 4–5 hours was replaced by a current-enhancing resonance. The appearance of this latter resonance could be explained by chemical changes in the OLED due to the diffusion of oxygen through the device from the oxygen-plasma-treated ITO. A working model is proposed which can explain this observed change as spindependent trapping and recombination at free radicals, although the model requires further experimentation to test its validity.</p>

scholarly journals Supplemental Lighting Orientation and Red-to-blue Ratio of Light-emitting Diodes for Greenhouse Tomato Production

HortScience ◽  
2014 ◽  
Vol 49 (4) ◽  
pp. 448-452 ◽  
Author(s):  
Paul Deram ◽  
Mark G. Lefsrud ◽  
Valérie Orsat
Keyword(s):  
High Efficiency ◽  
Light Emitting Diodes ◽  
Tomato Fruit ◽  
Fruit Production ◽  
Plant Production ◽  
Tomato Production ◽  
Light Emitting ◽  
Led Light ◽  
Red Led ◽  
Supplemental Lighting

Current greenhouse supplemental lighting technology uses broad-spectrum high-pressure sodium lamps (HPS) that, despite being an excellent luminous source, are not the most efficient light source for plant production. Specific light frequencies in the 400- to 700-nm range have been shown to affect photosynthesis more directly than other wavelengths (especially in the red and blue ranges). Light-emitting diodes (LEDs) could diminish lighting costs as a result of their high efficiency, lower operating temperatures, and wavelength specificity. LEDs can be selected to target the wavelengths used by plants, enabling growers to customize the light produced, to enable maximum plant production and limit wavelengths that do not significantly impact plant growth. In our experiment, hydroponically grown tomato plants (Solanum lycopersicum L.) were grown using a full factorial design with three light intensities (high: 135 μmol·m−2·s−1, medium: 115 μmol·m−2·s−1, and low: 100 μmol·m−2·s−1) at three red (661 nm) to blue (449 nm) ratio levels (5:1, 10:1, and 19:1). Secondary treatments for comparison were 100% HPS, 100% red LED light supplied from above the plant, 100% red LED light supplied below the plant, a 50%:50% LED:HPS mixture, and a control (no supplemental lighting). Both runs of the experiment lasted 120 days during the Summer–Fall 2011 and the Winter–Spring 2011–12. The highest biomass production (excluding fruit) occurred with the 19:1 ratio (red to blue) with increasing intensity resulting in more growth, whereas a higher fruit production was obtained using the 5:1 ratio. The highest marketable fruit production (fruit over 90 g) was obtained with the 50%:50% LED:HPS followed by 5:1 high and 19:1 high. Consistently the 5:1 high performed well in every category. LEDs have been shown to be superior in fruit production over HPS alone, and LEDs can improve tomato fruit production when mixed with HPS. LEDs provide a promising mechanism to enhance greenhouse artificial lighting systems.

scholarly journals Influence of A Site Cation on Nonlinear Band Gap Dependence of 2D Ruddlesden-Popper A2Pb1−xSnxI4 Perovskites

2021 ◽  
Author(s):  
Cameron Christopher Lloyd Underwood ◽  
David Carey ◽  
S. Ravi P. Silva
Keyword(s):  
Band Gap ◽  
Light Emitting Diodes ◽  
Great Promise ◽  
Light Emitting ◽  
Mono Layer ◽  
A Site

Ruddlesden-Popper phase (RPP) perovskites of the form A1n−1A22BnX3n+1 show great promise in stable photovoltaic (PV) devices or as light emitting diodes (LEDs). In particular, n= 1, mono-layer RPPs of the...

scholarly journals Encapsulation of Dyes in Luminescent Metal-Organic Frameworks for White Light Emitting Diodes

Nanomaterials ◽  
2021 ◽  
Vol 11 (10) ◽  
pp. 2761
Author(s):  
Zhihong Sun ◽  
Aaqib Khurshid ◽  
Muhammad Sohail ◽  
Weidong Qiu ◽  
Derong Cao ◽  
...  
Keyword(s):  
White Light ◽  
High Efficiency ◽  
Light Emitting Diodes ◽  
Fluorescent Dyes ◽  
Metal Organic Frameworks ◽  
Great Promise ◽  
Light Emitting ◽  
Wide Range ◽  
Metal Organic ◽  
White Light Emitting Diodes

The development of white light emitting diodes (WLEDs) holds great promise for replacing traditional lighting devices due to high efficiency, low energy consumption and long lifetime. Metal–organic frameworks (MOFs) with a wide range of luminescent behaviors are ideal candidates to produce white light emission in the phosphor-converted WLEDs. Encapsulation of emissive organic dyes is a simple way to obtain luminescent MOFs. In this review, we summarize the recent progress on the design and constructions of dye encapsulated luminescent MOFs phosphors. Different strategies are highlighted where white light emitting phosphors were obtained by combining fluorescent dyes with metal ions and linkers.

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