Low-intensity Light-emitting Diode Research Articles

Photocatalysis aided antibacterial properties of a green graphitic carbon-Cu2O-Ag2O composite: Towards an active non-persistent disinfectant

A novel green graphitic carbon (GGC)-supported Cu2O-Ag2O composite has been successfully synthesized via a facile co-precipitation technique. Its photocatalysis-aided antibacterial activity was evaluated under low-intensity light-emitting diode irradiation. The GGC not only served as an adsorbent matrix but also helped in restricting the rapid recombination of the electron-hole pairs, resulting in 100 % inactivation of 2.3 × 103 CFU mL−1Escherichia coli (E. coli) by the GGC-Cu2O-Ag2O composite within 15 min. In comparison to the composite, pristine GGC and Cu2O-Ag2O resulted in 13.8 and 61.5 % inactivation efficiency, respectively. Under optimal photo-chemical conditions (i.e., light wavelength: 440 to 625 nm; light intensity: 950 W m−2; pH: 6.4; catalyst dosage: 1 g L−1), 6 × 107 CFU mL−1 of E. coli and Enterococcus faecalis were completely inactivated within 45 min and 60 min of irradiation, respectively. The addition of scavengers decreased E. coli inactivation efficiency from 100 % to 61 % implying that holes are the main reactive oxygen species (ROS). The scanning electron micrographs depict prominent ROS-induced morphological changes in the bacterial cells. Further, there was no regrowth of bacteria via photoreactivation and the dark repair process. Moreover, the composite exhibited excellent stability as well as adequate inactivation activity even after three consecutive reuse cycles. The remnants of the composite after exhaustion are likely to be naturally sequestrated without any transport potential and persistence.

Increasing catches of adult moth pests (Lepidoptera: Tortricidae) in pome fruit with low‐intensity LED lights added to sex pheromone/kairomone lure‐baited traps

AbstractStudies of moth pests (Lepidoptera: Tortricidae) of pome fruit in Washington State, USA, evaluated the addition of low‐intensity light‐emitting diode (LED) lights to traps baited with sex pheromone or kairomone lures. Species included codling moth (CM), Cydia pomonella (L.), oriental fruit moth (OFM), Grapholita molesta (Busck), oblique banded leafroller (OBLR), Choristoneura rosaceana (Harris), and eye‐spotted budmoth (ESBM), Spilonota ocellana (Denis and Schiffenmüller). Lures included (E,E)‐8,10‐dodecadien‐1‐ol (codlemone) plus (E,Z)‐2,4‐ethyl decadienoate (pear ester) and acetic acid (AA) (Combo) and a blend of pear ester, (E)‐4,8‐dimethyl‐1,3,7‐nonatriene, pyranoid linalool oxide, and AA (4K) for CM; a three‐component OFM sex pheromone ((E)‐8‐dodecen‐1‐yl‐acetate, (Z)‐8‐dodecen‐1‐yl acetate, and (Z)‐8‐dodecen‐1‐ol) plus codlemone and terpinyl acetate plus AA for OFM; and 2‐phenylethanol and AA for OBLR and ESBM. Traps baited with only LEDs were not attractive for any of these tortricids. The addition of a LED to lure‐baited traps increased male and female catches 2‐12‐fold across the four pest species. The proportional increase in CM catches with the LEDs was similar with both the Combo and 4K lures. Traps baited with the 4K lure caught significantly more CM with a UV LED than with either blue or green LEDs. The proportion of females caught in traps that were mated did not change with the use of the lights across species. Significantly more CM of both sexes were caught in the adhesive on the side of the liner nearest the LED. The addition of LEDs sometimes increased the by‐catch of minute insects, but liners' saturation was never a factor impacting targeted moth catch. Adding the LED light significantly increased the catch of ESBM in CM‐baited traps and CM in OFM‐baited traps, respectively. The development of inexpensive, dual‐modality traps that add a light stimulus to a kairomonal‐based lure may improve direct control of these key orchard pests via female removal.

Thickness-Dependent Light Transmittance and Temperature Rise in Dual-Cure Bioactive and Light-Cure Bulk-Fill Composite Resins.

This study aimed to assess the light transmittance (T) and temperature increase through different increments of dual-cure bioactive bulk-fill restorative material (ACTIVA), light-cure bulk-fill, and conventional composite resin materials. Cylindrical specimens with a diameter of 8 mm and heights of 1, 2, 3, and 4 mm of ACTIVA, Tetric-N-Ceram bulk-fill (TBF), Filtek One bulk-fill (FBF), and Filtek Z250 (FZ) (n = 6 per group, 96 in total) were light-cured with a visible blue low-intensity light-emitting diode (LED) (650-800 mW/cm2 irradiance). T, and the temperature increase, were measured using an optical power meter and a digital thermometer during curing. The T mean values ranged between 0.012 and 0.239 (76.02 to 98.81% light attenuation), while the temperature rise mean values ranged between 9.02 and 20.80 °C. The parameters, including material type (partial eta squared (ηp2) = 0.284, p < 0.0001), thickness (ηp2 = 0.284, p < 0.0001), and their interaction (ηp2 = 0.185, p = 0.047), significantly affected the T values, whereas only the material type (ηp2 = 0.352, p = 0.047) affected the temperature rise values. The T and temperature rise mean values were highest in ACTIVA increments of 1-mm increments, in particular, showing the highest T mean values, followed by similar increments of TBF. A significantly higher T was found in 1-mm increments compared to thicker increments for all materials (p < 0.0001), and a significant positive correlation existed between T and temperature rise values (r = 0.348, p = 0.001). These findings show that the bioactive material ACTIVA and TBF allow for better T than the other materials, with ACTIVA recording a higher temperature rise. However, the large light attenuation observed for all materials, irrespective of thickness, suggests that curing in more than one location with a low-intensity LED is necessary to optimize the curing process. Furthermore, incremental filling of bulk-fill materials using a low intensity LED could be beneficial.

Strategic Approach for Frustrating Charge Recombination of Perovskite Solar Cells in Low-Intensity Indoor Light: Insertion of Polar Small Molecules at the Interface of the Electron Transport Layer

In this study, we propose a strategic interface engineering method for optimizing the power density and power conversion efficiency (PCE) of perovskite solar cells (PVSCs) under low-intensity indoor light conditions. The insertion of a polar bathocuproine (BCP) layer at the electron transport interface significantly improved the photovoltaic properties, in particular, the fill factor and open circuit voltage, in a low-intensity light environment. Based on the systemic characterizations of surface trap states and carrier dynamics using Kelvin probe force microscopy, we revealed that BCP facilitated efficient charge carrier separation and electron extraction under low-intensity light illumination due to surface passivation and dipole-induced suppressed charge recombination. The beneficial role of BCP enabled excellent indoor PCEs of 27.04 and 35.45% under low-intensity light-emitting diode and halogen lights, respectively. Modification of the electron transport layer interface using polar molecules is a simple but highly effective method for optimizing the indoor performance of PVSCs.

Thermal coupled photocatalysis over Pt/g-C3N4 for selectively reducing CO2 to CH4via cooperation of the electronic metal–support interaction effect and the oxidation state of Pt

Pt nanoparticle-loaded g-C3N4 (Pt/CN) that consisted of integrating Pt0 and Pt2+ species was prepared for selectively reducing CO2 to CH4 with H2O by thermal coupled photocatalysis. A strong electronic metal-support interaction was constructed between Pt nanoparticles and the g-C3N4 substrate, which limited the activity for CO evolution and improved the charge transfer from g-C3N4 to Pt for selective CH4 production. The formed Pt2+ species in the Pt nanoparticles completely suppress the side reaction of H2 production from reducing H2O. Moreover, a moderate heat input in the photocatalytic reaction facilitated the transfer of the photogenerated electrons from Pt nanoparticles to CO2, which further increased the photocatalytic activity for CH4 evolution. As a result, a significant enhancement of CO2 methanation performance (∼100 % selectivity, 14.8 μmol g−1 h−1) was realized on a 2 % Pt-loaded g-C3N4 photocatalyst under low intensity light-emitting diode (420 nm, on the order of solar intensity) irradiation at 125 °C.

Engineered nanomedicine for neuroregeneration: light emitting diode-mediated superparamagnetic iron oxide-gold core-shell nanoparticles functionalized by nerve growth factor

This paper reports nerve growth factor functionalized superparamagnetic iron oxide–gold core-shell nanoparticles (NGF-SPIO-Au NPs), an engineered nanomedicine for non-invasive neuron regeneration when irradiated by a low-intensity light-emitting diode (LED). NGF-SPIO-Au NPs of 20 μg/ml, were tested on PC-12 neuron-like cells, irradiated by LEDs (525 nm, 1.09, 1.44, and 1.90 mW/cm2). A remarkable Ca2+ influx was detected in differentiated PC-12 cells treated with NPs, irradiated by LED of 1.90 and 1.44 mW/cm2 with great cell viability (>84%) and proliferations. The strong heat generated through their plasmonic surface upon LED irradiation on NGF-SPIO-Au NPs was observed. For cells treated with LED (1.90 mW/cm2) and NGF-SPIO-Au NPs, a dramatic enhancement of neuronal differentiation (83%) and neurite outgrowth (51%) was found, and the upregulation of both the neural differentiation specific marker (β3-tubulin) and the cell adhesive molecule (integrin β1) was observed by the reverse transcription-polymerase chain reaction and western blot analysis.

Promotion of Flowering from Far-red Radiation Depends on the Photosynthetic Daily Light Integral

Under natural short days, growers can use photoperiodic lighting to promote flowering of long-day plants and inhibit flowering of short-day plants. Unlike traditional lamps used for photoperiodic lighting, low-intensity light-emitting diode (LED) lamps allow for a wide array of adjustable spectral distributions relevant to regulation of flowering, including red (R) and white (W) radiation with or without far-red (FR) radiation. Our objective was to quantify how day-extension (DE) photoperiodic lighting from two commercially available low-intensity LED lamps emitting R + W or R + W + FR radiation interacted with daily light integral (DLI) to influence stem elongation and flowering of several ornamental species. Long-day plants [petunia (Petunia ×hybrida Vilm.-Andr. ‘Dreams Midnight’) and snapdragon (Antirrhinum majus L. ‘Oh Snap Pink’)], short-day plants [african marigold (Tagetes erecta L. ‘Moonsong Deep Orange’) and potted sunflower (Helianthus annuus L. ‘Pacino Gold’)], and day-neutral plants [pansy (Viola ×wittrockiana Gams. ‘Matrix Yellow’) and zinnia (Zinnia elegans Jacq. ‘Magellan Cherry’)] were grown at 20/18 °C day/night air temperatures and under low (6–9 mol·m−2·d−1) or high (16–19 mol·m−2·d−1) seasonal photosynthetic DLIs from ambient solar radiation combined with supplemental high-pressure sodium lighting and DE LED lighting. Photoperiods consisted of a truncated 9-hour day (0800–1700 hr) with additional 1-hour (1700–1800 hr, 10 hours total), 4-hour (1700–2100 hr, 13 hours total), or 7-hour (1700–2400 hr, 16 hours total) R + W or R + W + FR LED lighting at 2 μmol·m−2·s−1. Days to visible bud, plant height at first open flower, and time to first open flower (TTF) of each species were influenced by DLI, lamp type, and photoperiod though to different magnitudes. For example, plant height of african marigold and potted sunflower at first open flower was greatest under R + W + FR lamps, high DLIs, and 16-hour photoperiods. Petunia grown under R + W lamps, high DLI, and 10- and 13-hour photoperiods were the most compact. For all species, TTF was generally reduced under high DLIs. For example, regardless of the lamp type, flowering of african marigold occurred fastest under a high DLI and 10-hour photoperiod. Flowering of petunia and snapdragon occurred fastest under a high DLI, R + W + FR lamps, and a 16-hour photoperiod. However, only under high DLIs, R + W or R + W + FR lamps were equally effective at promoting flowering when used to provide DE lighting. Our data suggest that under low DLIs, flowering of long-day plants (petunia and snapdragon) occurs more rapidly under lamps providing R + W + FR, whereas under high DLIs, flowering is promoted similarly under either R + W or R + W + FR lamps.

Geranium and Purple Fountain Grass Leaf Pigmentation Is Influenced by End-of-Production Supplemental Lighting with Red and Blue Light-emitting Diodes

Under low-light greenhouse conditions, anthocyanin pigmentation in vegetative tissues of red- or purple-leafed floricultural crops is not fully expressed and, consequently, plants are not as visually appealing to consumers. Our objective was to quantify the effect of end-of-production (EOP; before shipping) supplemental lighting (SL) of different light sources, qualities, and intensities on foliage color of geranium (Pelargonium ×hortorum L.H. Bailey ‘Black Velvet’) and purple fountain grass [Pennisetum ×advena Wipff and Veldkamp (formerly known as Pennisetum setaceum Forsk. Chiov. ‘Rubrum’)]. Plants were finished under early (Expt. 1) and late (Expt. 2) seasonal greenhouse ambient solar light and provided with 16 hours of day-extension lighting from low-intensity light-emitting diode (LED) lamps [7:11:33:49 blue:green:red:far-red light ratio (%); control] delivering 4.5 μmol·m−2·s−1, or 16 hours of EOP SL from high-pressure sodium (HPS) lamps delivering 70 μmol·m−2·s−1, or LED arrays (100:0, 87:13, 50:50, or 0:100 red:blue) delivering 100 μmol·m−2·s−1, or 0:100 red:blue LEDs delivering 25 or 50 μmol·m−2·s−1. Geranium and fountain grass chlorophyll content and leaf color were estimated using a SPAD-502 chlorophyll meter and Minolta tristimulus colorimeter, respectively. Relative chlorophyll content (RCC) and foliage L* (lightness), C* (chroma; a measure of saturation), and h° (hue angle; a measure of tone) values were significantly influenced by EOP SL and days of exposure. Generally, RCC of geranium and fountain grass increased from 3 to 14 days of exposure to EOP SL from HPS lamps and LEDs delivering 100 μmol·m−2·s−1. Under low daily light integrals (DLIs) [8.6 mol·m−2·d−1 (geranium) and 9.4 mol·m−2·d−1 (purple fountain grass)] EOP SL providing 100 μmol·m−2·s−1 of 100:0, 87:13, 50:50, or 0:100 red:blue light for ≥14 days resulted in lower L* (darker foliage), C* (saturated), and h° (orange to violet-red hues). Our data indicate that a minimum of 14 days of EOP SL providing 100 μmol·m−2·s−1 of 50:50 or 0:100 red:blue light enhanced foliage color of geranium and fountain grass leaves when plants were grown under a low greenhouse DLI ≤ 9 mol·m−2·d−1.

Effects of low-intensity non-coherent light therapy on the inflammatory process in the calcaneal tendon of ovariectomized rats.

The aim of this experimental study was to investigate the effects of low-intensity light-emitting diode (LED) phototherapy on the inflammatory process in the calcaneal tendon of ovariectomized rats (OVX) through the involvement of the inflammatory mediators interleukin (IL)-6, IL-10, and tumor necrosis factor-alpha (TNF-α). Thirty-five female Wistar rats were divided into 4 groups: 3 groups of OVX rats totaling 30 rats (untreated OVX rats [OVX injury group], treated OVX rats [OVX LED group], and control OVX rats; subgroups existed based on the sampling times, which were 3, 7, and 14days) and 1 group of non-OVX rats (not OVX; n = 5). Tendon injury was induced by trauma using a 208-g mass placed at 20cm from the right tendon of each animal with energy of 0.70J. The animals were treated 12h after tendonitis with LED therapy and every 48h thereafter until euthanasia (at 3, 7, or 14days). The tendons were dissected and stored in liquid nitrogen at -196°C, thawed only at the time of immunoenzymatic testing (ELISA). Groups treated with LED showed a decrease in the number of pro-inflammatory cells, IL-6, and TNF-α (p <0.05), and an increase in IL-10 (p < 0.05) when compared to the not OVX group (p < 0.05). It was concluded that low-intensity LED treatment using the parameters and wavelength of 945nm in the time periods studied reduced the release of IL-6 and TNF-α and increased the release of IL-10, thereby improving the inflammatory response in OVX rats.

End-of-production Supplemental Lighting with Red and Blue Light-emitting Diodes (LEDs) Influences Red Pigmentation of Four Lettuce Varieties

Under low-light greenhouse conditions, such as those found in northern latitudes, foliage of red leaf lettuce (Lactuca sativa L.) varieties is often green and not visually appealing to consumers. Our objective was to quantify the effect of end-of-production (EOP; prior to harvest) supplemental lighting (SL) of different sources and intensities on foliage color of four red leaf lettuce varieties, ‘Cherokee’, ‘Magenta’, ‘Ruby Sky’, and ‘Vulcan’. Plants were finished under greenhouse ambient solar light and provided with 16-hours of day-extension lighting from low intensity light-emitting diode (LED) lamps [7:11:33:49 blue:green:red:far red (control)] delivering 4.5 μmol·m−2·s−1, or 16-hours of EOP SL from high-pressure sodium (HPS) lamps delivering 70 μmol·m−2·s−1, or LED arrays [100:0, 0:100, or 50:50 (%) red:blue] delivering 100 μmol·m−2·s−1, or 0:100 blue LEDs delivering 25 or 50 μmol·m−2·s−1. Relative chlorophyll content (RCC) and foliage L* (lightness), and chromametric a* (change from green to red) and b* (change from yellow to blue) values were significantly influenced by EOP SL and days of exposure. Generally, RCC of all varieties increased from day 3 to 14 when provided with EOP SL from the HPS lamps and LEDs delivering 100 μmol·m−2·s−1. End-of-production SL providing 100 μmol·m−2·s−1 of 100:0, 0:100, or 50:50 red:blue light for ≥5 days resulted in increasing a* (red) and decreasing L* (darker foliage), b* (blue), and h° (hue angle; a measure of tone) for all varieties. Our data suggests that a minimum of 5 days of EOP SL providing 100 μmol·m−2·s−1 of 100:0, 0:100, or 50:50 red:blue light enhanced red pigmentation of ‘Cherokee’, ‘Magenta’, ‘Ruby Sky’, and ‘Vulcan’ leaves when plants are grown under a low greenhouse daily light integrals (DLIs) &lt;10 mol·m−2·d−1.

Organotellurium-mediated living radical polymerization under photoirradiation by a low-intensity light-emitting diode.

A low-intensity (6 W) light-emitting diode (LED) effectively activated an organotellurium chain transfer agent and the dormant species, promoting well-controlled radical polymerization. The use of the LED provided many advantages over the previously reported high-intensity Hg lamp, including high energy efficiency during the polymerization, and easy availability of the low-cost light source. Structurally well-defined poly(methyl methacrylate), poly(methyl acrylate), and polystyrene, with narrow molecular weight distributions, were synthesized under LED irradiation with or without a neutral density filter.

A comparative evaluation of the shear bond strength of five different orthodontic bonding agents polymerized using halogen and light-emitting diode curing lights: An in vitro investigation

With the introduction of photosensitive (light-activated) restorative materials in orthodontics, various methods have been suggested to enhance the polymerization of the materials used, including use of more powerful light curing devices. Bond strength is an important property and determines the amount of force delivered and the treatment duration. Many light-cured bonding materials have become popular but it is the need of the hour to determine the bonding agent that is the most efficient and has the desired bond strength. To evaluate and compare the shear bond strengths of five different orthodontic light cure bonding materials cured with traditional halogen light and low-intensity light-emitting diode (LED) light curing unit. 100 human maxillary premolar teeth, extracted for orthodontic purpose, were used to prepare the samples. 100 maxillary stainless steel bicuspid brackets of 0.018 slot of Roth prescription, manufactured by D-tech Company, were bonded to the prepared tooth surfaces of the mounted samples using five different orthodontic bracket bonding light-cured materials, namely, Enlight, Fuji Ortho LC (resin-modified glass ionomer cement), Orthobond LC, Relybond, and Transbond XT. The bond strength was tested on an Instron Universal testing machine (model no. 5582). In Group 1 (halogen group), Enlight showed the highest shear bond strength (16.4 MPa) and Fuji Ortho LC showed the least bond strength (6.59 MPa) (P value 0.000). In Group 2 (LED group), Transbond showed the highest mean shear bond strength (14.6 MPa) and Orthobond LC showed the least mean shear bond strength (6.27 MPa) (P value 0.000). There was no statistically significant difference in the shear bond strength values of all samples cured using either halogen (mean 11.49 MPa) or LED (mean 11.20 MPa), as the P value was 0.713. Polymerization with both halogen and LED resulted in shear bond strength values which were above the clinically acceptable range given by Reynolds. The LED light curing units produced comparable shear bond strength to that of halogen curing units.

First operation of a hybrid photon detector prototype with electrostatic cross-focussing and integrated silicon pixel readout

We report on the first operation of a hybrid photon detector prototype with integrated silicon pixel readout for the ring imaging Cherenkov detectors of the LHCb experiment. The photon detector is based on a cross-focussed image intensifier tube geometry where the image is de-magnified by a factor of 4. The anode consists of a silicon pixel array, bump-bonded to a binary readout chip with matching pixel electronics. The prototype has been characterized using a low-intensity light-emitting diode operated in pulsed mode. Its performance in terms of single-photoelectron detection efficiency and imaging properties is presented. A model of photoelectron detection is proposed, and is shown to be in good agreement with the experimental data. It includes an estimate of the charge signal generated in the silicon detector, and the combined effects of the comparator threshold spread of the pixel readout chip, charge sharing at the pixel boundaries and back-scattering of the photoelectrons at the silicon detector surface.