Synthesis and high efficiency green light-emitting diode of a soluble polymer

A soluble polymer emitting green color with high efficiency was synthesized. Bright green electroluminescence devices, both single layer and multilayer, were fabricated. The luminous efficiency was improved dramatically. Carrier injection from the electrodes to the emissive layer and concomitant green electroluminescence from the emissive layer were observed. A luminance of 920 cd/m(2) and luminous efficiency of 5.35 1m/W were achieved at a drive voltage of 15 V for the multilayer device. (C) 1997 Elsevier Science S.A.

A collinear light-emitting diode-induced fluorescence detector for capillary electrophoresis

A novel fluorescence detector based on collinear scheme using a brightness light-emitting diode emitting at 470 nm as excitation source is described. The detector is assembled by all-solid-state optical-electronic components and Coupled with capillary electrophoresis using on-column detection mode. Fluorescein isothiocyanate (FITC) and FITC-labeled amino acids and small molecule peptide as test analyte were used to evaluate the detector. The concentration limit of detection for FITC-labeled phenylalanine was 10 nM at a signal-to-noise ratio (S/N) of 3. The system exhibited good linear responses in the range of 1 x 10(-7) to 2 x 10(-5) M (R-2 = 0.999). (c) 2004 Elsevier B.V. All rights reserved.

Simultaneous light emitting diode-induced fluorescence and contactless conductivity detection for capillary electrophoresis

A combined detection system of simultaneous contactless conductometric and fluorescent detection for capillary electrophoresis (CE) has been designed and evaluated. The two processes share a common detection cell. A blue light-emitting diode (LED) was used as the excitation source and an optical fiber was used to collect the emitting fluorescence for fluorescent detection (FD). Inorganic ions, fluorescein isothiocyanate (FITC)-labeled amino acids and small molecule peptides were separated and detected by the combined detector, and the detection limits (LODs) of sub-μ M level were achieved.

Low-level laser therapy and light-emitting diode effects in the secretion of neuropeptides SP and CGRP in rat skin

The phototherapy effects in the skin are related to biomodulation, usually to accelerate wound healing. However, there is no direct proof of the interrelation between the effects of low-level laser therapy (LLLT) and light-emitting diode (LED) in neuropeptide secretion, these substances being prematurely involved in the neurogenic inflammation phase of wound healing. This study therefore focused on investigating LLLT and LED in Calcitonin gene-related peptide (CGRP) and substance P (SP) secretion in healthy rat skin. Forty rats were randomly distributed into five groups with eight rats each: Control Group, Blue LED Group (470 nm, 350 mW power), Red LED Group (660 nm, 350 mW power), Red Laser Group (660 nm, 100 mW power), and Infrared Laser Group (808 nm, 100 mW power) (DMCA (R) Equipamentos Ltda., So Carlos, So Paulo, Brazil). the skin of the animals in the experimental groups was irradiated using the punctual contact technique, with a total energy of 40 J, single dose, standardized at one point in the dorsal region. After 14 min of irradiation, the skin samples were collected for CGRP and SP quantification using western blot analysis. SP was released in Infrared Laser Group (p = 0.01); there was no difference in the CGRP secretion among groups. Infrared (808 nm) LLLT enhances neuropeptide SP secretion in healthy rat skin.

Synthesis and Photoluminescence Properties of Novel Red Phosphors for White Light Emitting Diode Applications

Several series of Eu3+ based red emitting phosphor materials were synthesized using solid state reaction route and their properties were characterized. The present studies primarily investigated the photoluminescence properties of Eu3+ in a family of closely related host structure with a general formula Ln3MO7. The results presented in the previous chapters throws light to a basic understanding of the structure, phase formation and the photoluminescence properties of these compounds and their co-relations. The variation in the Eu3+ luminescence properties with different M cations was studied in Gd3-xMO7 (M = Nb, Sb, Ta) system.More ordering in the host lattice and more uniform distribution of Eu3+ ions resulting in the increased emission properties were observed in tantalate system.Influence of various lanthanide ion (Lu, Y, Gd, La) substitutions on the Eu3+ photoluminescence properties in Ln3MO7 host structures was also studied. The difference in emission profiles with different Ln ions demonstrated the influence of long range ordering, coordination of cations and ligand polarizability in the emission probabilities, intensity and quantum efficiency of these phosphor materials. Better luminescence of almost equally competing intensities from all the 4f transitions of Eu3+ was noticed for La3TaO7 system. Photoluminescence properties were further improved in La3TaO7 : Eu3+ phosphors by the incorporation of Ba2+ ions in La3+ site. New red phosphor materials Gd2-xGaTaO7 : xEu3+ exhibiting intense red emissions under UV excitation were prepared. Optimum doping level of Eu3+ in these different host lattices were experimentally determined. Some of the prepared samples exhibited higher emission intensities than the standard Y2O3 : Eu3+ red phosphors. In the present studies, Eu3+ acts as a structural probe determining the coordination and symmetry of the atoms in the host lattice. Results from the photoluminescence studies combined with the powder XRD and Raman spectroscopy investigations helped in the determination of the correct crystal structures and phase formation of the prepared compounds. Thus the controversy regarding the space groups of these compounds could be solved to a great extent. The variation in the space groups with different cation substitutions were discussed. There was only limited understanding regarding the various influential parameters of the photoluminescence properties of phosphor materials. From the given studies, the dependence of photoluminescence properties on the crystal structure and ordering of the host lattice, site symmetries, polarizability of the ions, distortions around the activator ion, uniformity in the activator distribution, concentration of the activator ion etc. were explained. Although the presented work does not directly evidence any application, the materials developed in the studies can be used for lighting applications together with other components for LED lighting. All the prepared samples were well excitable under near UV radiation. La3TaO7 : 0.15Eu3+ phosphor with high efficiency and intense orange red emissions can be used as a potential red component for the realization of white light with better color rendering properties. Gd2GaTaO7 : Eu3+, Bi2+ red phosphors give good color purity matching to NTSC standards of red. Some of these compounds exhibited higher emission intensities than the standard Y2O3 : Eu3+ red phosphors. However thermal stability and electrical output using these compounds should be studied further before applications. Based on the studies in the closely related Ln3MO7 structures, some ideas on selecting better host lattice for improved luminescence properties could be drawn. Analyzing the CTB position and the number of emission splits, a general understanding on the doping sites can be obtained. These results could be helpful for phosphor designs in other host systems also, for enhanced emission intensity and efficiency.

Effect of Cluster Multi-Diode Light Emitting Diode Therapy (LEDT) on Exercise-Induced Skeletal Muscle Fatigue and Skeletal Muscle Recovery in Humans

Background and Objectives: There are some indications that low-level laser therapy (LLLT) may delay the development of skeletal muscle fatigue during high-intensity exercise. There have also been claims that LED cluster probes may be effective for this application however there are differences between LED and laser sources like spot size, spectral width, power output, etc. In this study we wanted to test if light emitting diode therapy (LEDT) can alter muscle performance, fatigue development and biochemical markers for skeletal muscle recovery in an experimental model of biceps humeri muscle contractions. Study Design/Materials and Methods: Ten male professional volleyball players (23.6 [SD +/- 5.6] years old) entered a randomized double-blinded placebo-controlled crossover trial. Active cluster LEDT (69 LEDs with wavelengths 660/850 nm, 10/30 mW, 30 seconds total irradiation time, 41.7J of total energy irradiated) or an identical placebo LEDT was delivered under double-blinded conditions to the middle of biceps humeri muscle immediately before exercise. All subjects performed voluntary biceps humeri contractions with a workload of 75% of their maximal voluntary contraction force (MVC) until exhaustion. Results: Active LEDT increased the number of biceps humeri contractions by 12.9% (38.60 [SD +/- 9.03] vs. 34.20 [SD +/- 8.68], P = 0.021) and extended the elapsed time to perform contractions by 11.6% (P = 0.036) versus placebo. In addition, post-exercise levels of biochemical markers decreased significantly with active LEDT: Blood Lactate (P = 0.042), Creatine Kinase (P = 0.035), and C-Reative Protein levels (P = 0.030), when compared to placebo LEDT. Conclusion: We conclude that this particular procedure and dose of LEDT immediately before exhaustive biceps humeri contractions, causes a slight delay in the development of skeletal muscle fatigue, decreases post-exercise blood lactate levels and inhibits the release of Creatine Kinase and C-Reative Protein. Lasers Surg. Med. 41:572-577, 2009. (C) 2009 Wiley-Liss, Inc.

Comparison between cold water immersion therapy (CWIT) and light emitting diode therapy (LEDT) in short-term skeletal muscle recovery after high-intensity exercise in athletes-preliminary results

In the last years, phototherapy has becoming a promising tool to improve skeletal muscle recovery after exercise, however, it was not compared with other modalities commonly used with this aim. In the present study we compared the short-term effects of cold water immersion therapy (CWIT) and light emitting diode therapy (LEDT) with placebo LEDT on biochemical markers related to skeletal muscle recovery after high-intensity exercise. A randomized double-blind placebo-controlled crossover trial was performed with six male young futsal athletes. They were treated with CWIT (5A degrees C of temperature [SD +/- 1A degrees]), active LEDT (69 LEDs with wavelengths 660/850 nm, 10/30 mW of output power, 30 s of irradiation time per point, and 41.7 J of total energy irradiated per point, total of ten points irradiated) or an identical placebo LEDT 5 min after each of three Wingate cycle tests. Pre-exercise, post-exercise, and post-treatment measurements were taken of blood lactate levels, creatine kinase (CK) activity, and C-reactive protein (CRP) levels. There were no significant differences in the work performed during the three Wingate tests (p > 0.05). All biochemical parameters increased from baseline values (p < 0.05) after the three exercise tests, but only active LEDT decreased blood lactate levels (p = 0.0065) and CK activity (p = 0.0044) significantly after treatment. There were no significant differences in CRP values after treatments. We concluded that treating the leg muscles with LEDT 5 min after the Wingate cycle test seemed to inhibit the expected post-exercise increase in blood lactate levels and CK activity. This suggests that LEDT has better potential than 5 min of CWIT for improving short-term post-exercise recovery.

Ion beam assisted deposition of an organic light emitting diode electrode

This work presents the electro-optical characterization of metal-organic interfaces prepared by the Ion Beam Assisted Deposition (IBAD) method. IBAD applied in this work combines simultaneously metallic film deposition and bombardment with an independently controlled ion beam, allowing different penetration of the ions and the evaporated metallic elements into the polymer. The result is a hybrid, non-abrupt interface, where polymer, metal and ion coexists. We used an organic light emitting diode, which has a typical vertical-architecture, for the interface characterization: Glass/Indium Tin Oxide (ITO)/Poly[ethylene-dioxythiophene/poly{styrenesulfonicacid}]) (PEDOT:PSS) /Emitting Polymer/Metal. The emitting polymer layer comprised of the Poly[(9,9-dioctyl-2,7-divinylenefluorenylene)-alt-co-{2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylene}] (PFO) and the metal layer of aluminum prepared with different Ar(+) ion energies varying in the range from 0 to 1000 eV. Photoluminescence, Current-Voltage and Electroluminescence measurements were used to study the emission and electron injection properties. Changes of these properties were related with the damage caused by the energetic ions and the metal penetration into the polymer. Computer simulations of hybrid interface damage and metal penetration were confronted with experimental data. (C) 2010 Elsevier B.V. All rights reserved.

Light-Emitting Diode Therapy in Chemotherapy-Induced Mucositis

Background and Objective: Mucositis is the most common oral complication of cancer chemotherapy, which causes pain on mastication and swallowing, impairs patients` ability to eat and take oral drugs and may determine interruption of the treatment. The aim of this study was to evaluate the effect of light-emitting diode (LED) therapy on chemotherapy-induced mucositis in hamsters. Study Design/Materials and Methods: Animals of both experimental (Group 1; n = 32) and positive control (Group II; n = 32) groups received intraperitoneal injections of 5-fluorouracil on days 0 and 2. All animals had their right and left cheek pouch irritated by superficial scratching on days 3 and 4. In Group I, LED irradiation (630 nm +/- 10 nm, 160 mW, 12 J/cm(2)) was applied during 37.5 seconds at days 3, 4, 6, 8, 10, 12, and 14. In Group II, mucositis was induced, but LED therapy was not performed. The oral mucosa was photographed from day 4 to 14 at 2-day intervals. Photographs were randomly scored according to the severity of induced mucositis (0 to 5). In the negative control group (Group III; n = 6), no mucositis was induced. Biopsies of the cheek pouches of 8 animals (Group I and Group II) were surgically obtained on days 5, 9, 13 and 15 and processed for histological examination. Results: The statistical analysis showed significant differences between irradiated and non-irradiated groups (P < 0.05). However, muscular degeneration was observed in 18% of the samples of Group I. Conclusion: It may be concluded that the LED therapy protocol established for this in vivo study was effective in reducing the severity of oral mucositis, although the oral lesions were not completely prevented. Lasers Surg. Med. 40:625-633, 2008. (c) 2008Wiley-Liss, Inc.

Light-Emitting Diode Therapy in Chemotherapy-Induced Mucositis

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Anti-Inflammatory Effects of Low-Level Light Emitting Diode Therapy on Achilles Tendinitis in Rats

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Assessment of the effectiveness of light-emitting diode and diode laser hybrid light sources to intensify dental bleaching treatment

Objective. To evaluate the effectiveness of the color change of hybrid light-emitting diode (LED) and low-intensity infrared diode laser devices for activating dental bleaching and to verify the occurrence of a color regression with time. Material and methods. A total of 180 specimens obtained from human premolars were immersed in a coffee solution for 15 days for darkening and then divided into eight experimental groups (n = 20 in each) as follows: G1, bleaching without light; G2, bleaching with halogen light; G3, bleaching with a blue LED (1000 mW/470 nm) and a laser device (120 mW/795 nm) simultaneously; G4, bleaching with an LED emitting blue light (1000 mW/470 nm); G5, bleaching with a blue LED (800 mW/470 nm) and a laser device (500 mW/830 nm) simultaneously; G6, bleaching with a blue LED device (800 mW); G7, bleaching with a green LED (600 mW/530 nm) and a laser device (120 mW/795 nm) simultaneously; and G8, bleaching with a green LED (600 mW). Three measurements were performed (at baseline and 14 days and 12 months after bleaching) using a Vita Easyshade spectrophotometer. The data were submitted to two-way ANOVA and a Tukey test. Results. All groups showed significantly higher Delta E values than Group G1, with the exception of Group G8. Variations in the Delta E values at 14 days were significant when compared with those obtained at baseline and after 12 months. Conclusions. Light activation of the bleaching gel provided faster and more intense bleaching than use of the bleaching gel without light activation. Combinations of low-intensity diode lasers are ineffective as a bleaching gel activator. Color regression was observed after 12 months of storage.

Antimicrobial photodynamic action on dentin using a light-emitting diode light source

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Shear bond strength of orthodontic brackets bonded using halogen light and light-emitting diode at different debond times

The aim of this in vitro study was to compare the photoactivation effects of QTH (Quartz-Tungsten-Halogen) and LED (Light-Emitting Diode) on the SBS (Shear Bond Strength) of orthodontic brackets at different debond times. Seventy-two bovine lower incisors were randomly divided into two groups according to the photoactivation system used (QTH or LED). The enamel surfaces were conditioned with Transbond self-etching primer, and APC (Adhesive Pre-Coated) brackets were used in all specimens. Group I was cured with QTH for 20 s and Group II with LED for 10 s. Both groups were subdivided according to the different experimental times after bonding (immediately, 24 h and 7 days). The specimens were tested for SBS and the enamel surfaces were analyzed according to the Adhesive Remnant Index (ARI). The statistical analysis included the Tukey's test to evaluate the main effects of photoactivation and debond time on SBS. The Chi-square test was used to compare the ARI values found for each group, and no statistically significant difference was observed. The debond time of 7 days for QTH photoactivation showed statistically greater values of SBS when compared to the immediate and 24 h periods. There was no statistically significant difference between the QTH and LED groups immediately and after the 24 h period. In conclusion, bonding orthodontic brackets with LED photoactivation for 10 s is suggested because it requires a reduced clinical chair time.