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Light-emitting diode

Lesley W Chan, Daniel E Morse, Michael J Gordon
Near- and sub-wavelength photonic structures are used by numerous organisms (e.g., insects, cephalopods, fish, birds) to create vivid and often dynamically-tunable colors, as well as create, manipulate, or capture light for vision, communication, crypsis, photosynthesis, and defense. This review introduces the physics of moth eye (ME)-like, biomimetic nanostructures and discusses their application to reduce optical losses and improve efficiency of various optoelectronic devices, including photodetectors, photovoltaics, imagers, and light emitting diodes...
March 16, 2018: Bioinspiration & Biomimetics
Paulo V Mezzaroba, Dalton M Pessôa Filho, Alessandro M Zagatto, Fabiana Andrade Machado
This study aimed to investigate the effect of prior LED sessions on the responses of cardiorespiratory parameters during the running incremental step test. Twenty-six healthy, physically active, young men, aged between 20 and 30 years, took part in this study. Participants performed two incremental load tests after placebo (PLA) and light-emitting diode application (LED), and had their gas exchange, heart rate (HR), blood lactate, and rating of perceived exertion (RPE) monitored during all tests. The PLA and LED conditions were compared using the dependent Student t test with significance set at 5%...
March 15, 2018: Lasers in Medical Science
Xiaoyong Huang, Shaoying Wang, Bin Li, Qi Sun, Heng Guo
In this work, we reported on high-brightness Eu3+ -activated Ca3 Lu(AlO)3 (BO3 )4 (CLAB) red-emitting phosphors. Under 397 nm excitation, the CLAB:Eu3+ phosphors showed intense red emissions at around 621 nm with CIE coordinates of (0.657, 0.343). The optimal doping concentration of Eu3+ ions was found to be 30 mol. %, and the CLAB:0.3Eu3+ sample possessed high-color purity of 93% and ultra-high internal quantum efficiency as great as 98.5%. Importantly, the CLAB:0.3Eu3+ also had good thermal stability. Finally, a white-light-emitting diode (WLED) lamp with good color-rendering index was fabricated by using a 365 nm ultraviolet chip and the phosphor blends of CLAB:0...
March 15, 2018: Optics Letters
Rugang Geng, Ram C Subedi, Hoang M Luong, Minh T Pham, Weichuan Huang, Xiaoguang Li, Kunlun Hong, Ming Shao, Kai Xiao, Lawrence A Hornak, Tho D Nguyen
Hyperfine interaction (HFI), originating from the coupling between spins of charge carriers and nuclei, has been demonstrated to strongly influence the spin dynamics of localized charges in organic semiconductors. Nevertheless, the role of charge localization on the HFI strength in organic thin films has not yet been experimentally investigated. In this study, the statistical relation hypothesis that the effective HFI of holes in regioregular poly(3-hexylthiophene) (P3HT) is proportional to 1/N^{0.5} has been examined, where N is the number of the random nuclear spins within the envelope of the hole wave function...
February 23, 2018: Physical Review Letters
Juan Zhao, Zhihe Chi, Zhan Yang, Xiaojie Chen, Michael S Arnold, Yi Zhang, Jiarui Xu, Zhenguo Chi, Matthew P Aldred
Truly stretchable electronics, wherein all components themselves permit elastic deformation as the whole devices are stretched, exhibit unique advantages over other strategies, such as simple fabrication process, high integrity of entire components and intimate integration with curvilinear surfaces. In contrast to the stretchable devices using stretchable interconnectors to integrate with rigid active devices, truly stretchable devices are realized with or without intentionally employing structural engineering (e...
March 15, 2018: Nanoscale
Ji Yong Choi, Cheol Young Choi
This study was conducted to identify the possible effect of recombinant vertebrate ancient long (VAL) opsin as a non-visual "photoreceptor" in the deep brain of goldfish, Carassius auratus. In addition, we investigated the effects of green-wavelength light on the predictable reproductive function of VAL-opsin as a green-sensitive pigment in the deep brain. To determine this, we quantified changes in gonadotropin hormone (GTH) [GTHα, follicle stimulating hormone (FSH) and luteinizing hormone (LH)] and estrogen receptor (ER; ERα and ERβ) mRNA expression levels associated with goldfish reproduction as well as changes in plasma FSH, LH, and 17β-estradiol (E2 ) activities after injection of recombinant VAL-opsin protein in two concentrations (0...
March 14, 2018: Fish Physiology and Biochemistry
Alina Keller, Piotr Bialecki, Torsten Johannes Wilhelm, Marcus Klaus Vetter
Significant numbers of liver biopsies fail to yield representative tissue samples. This study was conducted to evaluate the ability of LED-based diffuse reflectance spectroscopy to discriminate tumors from liver parenchyma. Ex vivo spectra were acquired from malignant lesions and liver parenchyma of 32 patients who underwent liver resection using a white light source and several LEDs. Integrated spectra of two combined LEDs with emission peaks at 470 nm and 515 nm were classified with 98.4% sensitivity and 99...
March 1, 2018: Biomedical Optics Express
Shuhei Okuyama, Tadanobu Nagaya, Kazuhide Sato, Fusa Ogata, Yasuhiro Maruoka, Peter L Choyke, Hisataka Kobayashi
Near-infrared photoimmunotherapy (NIR-PIT), a promising cancer therapy utilizing an antibody-photoabsorber conjugate (APC) and NIR light, which induces rapid necrotic cell death only in APC-bound cells. Effective NIR-PIT in mouse models has been achieved using superficial light illumination (SLI) with light emitting diodes (LEDs) or lasers, but in the clinical setting, fiber optic diffusers have been employed to deliver light to deeper tumors. However, the performance of NIR light in tissue delivered by fiber optic diffusers is poorly understood...
February 16, 2018: Oncotarget
Yinqi Luo, Tiancheng Yu, Li Nian, Linlin Liu, Fei Huang, Zengqi Xie, Yuguang Ma
Cathode interlayer is of crucial importance for efficient electron injection in inverted polymer light-emitting diodes (PLEDs) to realize high electroluminescence efficiency. Here, a novel photoconductive cathode interlayer based on organic dye doped ZnO (ZnO:PBI-H) is applied as cathode buffer layer in PLEDs, and dramatically enhanced device performance is obtained. The photo doping of ZnO may greatly promote the electron injection ability under the device working conditions, which increases the electron-hole recombination efficiency when using P-PPV as the light emitting material...
March 14, 2018: ACS Applied Materials & Interfaces
Darika Saitawee, Aroon Teerakapong, Noppawan Phumala Morales, Paiboon Jitprasertwong, Doosadee Hormdee
BACKGROUND AND OBJECTIVE: Curcumin, one of an established curcuminoid substances extracted from Curcuma longa, has been used as a photosensitizer (PS) in photodynamic therapy (PDT). Curcuminoid substances has been reported to have benefits in treating dental chronic infection and inflammation diseases, such as chronic periodontitis. The purpose of this study was to find the optimum concentration of Curcuma longa (CL) extract, containing all curcuminoid substances, and the power density of blue light (BL) in photodynamic therapy against periodontally pathogenic bacteria, A...
March 10, 2018: Photodiagnosis and Photodynamic Therapy
Sajal Shrivastava, Won-Il Lee, Nae-Eung Lee
A critical unmet need in the diagnosis of bacterial infections, which remain a major cause of human morbidity and mortality, is the detection of scarce bacterial pathogens in a variety of samples in a rapid and quantitative manner. Herein, we demonstrate smartphone-based detection of Staphylococcus aureus in a culture-free, rapid, quantitative manner from minimally processed liquid samples using aptamer-functionalized fluorescent magnetic nanoparticles. The tagged S. aureus cells were magnetically captured in a detection cassette, and then fluorescence was imaged using a smartphone camera with a light-emitting diode as the excitation source...
March 6, 2018: Biosensors & Bioelectronics
Hoon Lee, Inkyu Lee, Sang Hyun Lee
This paper presents a deep-learning (DL) based approach to the design of multi-colored visible light communication (VLC) systems where RGB light-emitting diode (LED) lamps accomplish multi-dimensional color modulation under color and illuminance requirements. It is aimed to identify a pair of multi-color modulation transmitter and receiver leading to efficient symbol recovery performance. To this end, an autoencoder (AE), an unsupervised deep learning technique, is adopted to train the end-to-end symbol recovery process that includes the VLC transceiver pair and a channel layer characterizing the optical channel along with additional LED intensity control features...
March 5, 2018: Optics Express
Abdullah I Alhassan, Nathan G Young, Robert M Farrell, Christopher Pynn, Feng Wu, Ahmed Y Alyamani, Shuji Nakamura, Steven P DenBaars, James S Speck
The effect of employing an AlGaN cap layer in the active region of green c-plane light-emitting diodes (LEDs) was studied. Each quantum well (QW) and barrier in the active region consisted of an InGaN QW and a thin Al0.30 Ga0.70 N cap layer grown at a relatively low temperature and a GaN barrier grown at a higher temperature. A series of experiments and simulations were carried out to explore the effects of varying the Al0.30 Ga0.70 N cap layer thickness and GaN barrier growth temperature on LED efficiency and electrical performance...
March 5, 2018: Optics Express
Jinglin Zhan, Zhizhong Chen, Qianqian Jiao, Yulong Feng, Chengcheng Li, Yifan Chen, Yiyong Chen, Fei Jiao, Xiangning Kang, Shunfeng Li, Qi Wang, Tongjun Yu, Guoyi Zhang, Bo Shen
GaN/InGaN multi-quantum-wells (MQWs) micron light emitting diodes (µLEDs) with the size ranging from 10 to 300 µm are fabricated. Effects of strain relaxation on the performance of µLEDs have been investigated both experimentally and numerically. Kelvin probe force microscopy (KPFM) and micro-photoluminescence (µPL) are used to characterize the strained area on micron pillars. Strain relaxation and reducing polarization field in MQWs almost affects the whole mesa for 10 µm LEDs and about 4% area around the lateral for 300 µm LEDs...
March 5, 2018: Optics Express
Jeong-Tak Oh, Yong-Tae Moon, Dae-Sung Kang, Chan-Keun Park, Jae-Woong Han, Myung-Hoon Jung, Youn-Joon Sung, Hwan-Hee Jeong, June-O Song, Tae-Yeon Seong
We demonstrated the growth of crack-free high-quality GaN-based UV vertical LEDs (VLEDs) (λ = 365 nm) on 6-inch sapphire substrates by using an ex-situ sputtered AlN nucleation layer (NL) and compared their performance with that of UV VLEDs with an in situ low temperature (LT) AlGaN NL. The X-ray diffraction (XRD) results showed that the ex-situ AlN sample contained lower densities of screw-type and edge-type threading dislocations than the in situ AlGaN NL sample. The micro-Raman results revealed that the ex-situ AlN sample was under more compressive stress than the in situ AlGaN sample...
March 5, 2018: Optics Express
Nobuhiro Yamauchi, Yoichiro Taguchi, Hirohito Kato, Makoto Umeda
BACKGROUND: Light-emitting diode (LED) is attracting attention as a new light source for phototherapy. However, its effects on periodontal tissue regeneration remain unknown. The aim of this study was to examine the effects of high-power, red LED irradiation on human periodontal ligament stem cells (PDLSCs), which play an important role in periodontal tissue regeneration. METHODS: PDLSCs were derived from adult human third molars. The light source was red LED (peak wavelength: 650 nm)...
March 12, 2018: Journal of Periodontology
Ouyang Wang, Lei Wang, Zhaohan Li, Qiulei Xu, Qingli Lin, Hongzhe Wang, Zuliang Du, Huaibin Shen, Lin Song Li
We report a facile and robust synthesis of ZnCdS core/shell quantum dots (QDs) with thick Cdx Zn1-x S (x = constant) uniform alloys as an intermediate shell which can provide effective confinement of excitons within the ZnCdS cores and ultrathin ZnS outermost shell to improve the stability by epitaxial growth at a relatively high temperature. The resulting nearly monodisperse ZnCdS/Cdx Zn1-x S/ZnS core/shell QDs have high photoluminescence quantum yield (near to 100%) and high color purity (full width at half maximum (FWHM) < 18 nm)...
March 12, 2018: Nanoscale
Robert Naumann, Martin Goez
We present a novel photoredox catalytic system that delivers synthetically useable concentrations of hydrated electrons when illuminated with a green light-emitting diode (LED). The catalyst is a ruthenium complex protected by an anionic micelle, and the urate dianion serves as sacrificial donor confined to the aqueous bulk. Through its chemical properties, that donor not only suppresses charge recombination that would limit the electron yield but also enables this system to perform cross couplings via hydrated electrons, for which we report the first examples...
March 12, 2018: Chemistry: a European Journal
Karen Strassel, Adrian Kaiser, Sandra Jenatsch, Anna Véron, Surendra Babu Anantharaman, Erwin Hack, Matthias Diethelm, Frank Alain Nüesch, Rian Aderne, Cristiano Legnani, Sergii Yakunin, Marco Cremona, Roland Hany
Efficient light detection in the near-infrared (NIR) wavelength region is central to emerging applications such as medical imaging and machine vision. An organic upconverter (OUC) consists of a NIR sensitive organic photodetector (OPD) and an organic visible light emitting diode (OLED), connected in series. The device converts NIR light directly to visible light, allowing pixelles imaging of a NIR scene in the visible. Here, we present an OUC composed of a NIR selective squaraine-dye based OPD and a fluorescent OLED...
March 12, 2018: ACS Applied Materials & Interfaces
Noriyuki Ogata, Kazuo Ohtsuka, Seiko Sasanuma, Masataka Ogawa, Yasuharu Maeda, Katsuro Ichimasa, Yuichi Mori, Masashi Misawa, Toyoki Kudo, Tomokazu Hisayuki, Takemasa Hayashi, Kunihiko Wakamura, Hideyuki Miyachi, Toshiyuki Baba, Fumio Ishida, Shin-Ei Kudo
Background and study aims:  Capsule endoscopy (CE) has become a routine means of diagnosing obscure gastrointestinal bleeding (OGIB) in the small intestine. Capsules using novel blue-enhanced white light-emitting diodes are expected to acquire clearer contrast images (CIs) of the small bowel vasculature. We conducted a pilot study to examine whether CIs facilitate visualization of small bowel erosions, ulcers, and areas of angioectasia compared with standard white light images (WLIs)...
March 2018: Endoscopy International Open
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