Distribution by Scientific Domains

Terms modified by PL

  • pl algorithm
  • pl analysis
  • pl efficiency
  • pl emission
  • pl intensity
  • pl level
  • pl measurement
  • pl model
  • pl models
  • pl peak
  • pl property
  • pl quantum yield
  • pl regression
  • pl spectroscopy
  • pl spectrum

  • Selected Abstracts

    Preparation, structure and photoluminescence properties of SiO2,coated ZnS nanowires

    Changhyun Jin
    Abstract It is essential to passivate one-dimensional (1D) nanostructures with insulating materials to avoid crosstalking as well as to protect them from contamination and oxidation. The structure and influence of thermal annealing on the photoluminescence properties of ZnS-core/SiO2 -shell nanowires synthesized by the thermal evaporation of ZnS powders followed by the sputter deposition of SiO2 were investigated. Transmission electron microscopy and X-ray diffraction analyses revealed that the cores and shells of the core-shell nanowires were single crystal zinc blende-type ZnO and amorphous SiO2, respectively. Photoluminescence (PL) measurement showed that the core-shell nanowires had a green emission band centered at around 525 nm with a shoulder at around 385 nm. The PL emission of the core-shell nanowires was enhanced in intensity by annealing in an oxidative atmosphere and further enhanced by subsequently annealing in a reducing atmosphere. Also the origin of the enhancement of the green emission by annealing is discussed based on the energy-dispersive X-ray spectroscopy analysis results. ( 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

    Low temperature hydrothermal growth and optical properties of ZnO nanorods

    J. H. Yang
    Abstract Well-faceted hexagonal ZnO nanorods have been synthesized by a simple hydrothermal method at relative low temperature (90C) without any catalysts or templates. Zinc oxide (ZnO) nanorods were grown in an aqueous solution that contained Zinc chloride (ZnCl2, Aldrich, purity 98%) and ammonia (25%). Most of the ZnO nanorods show the perfect hexagonal cross section and well-faceted top and side surfaces. The diameter of ZnO nanorods decreased with the reaction time prolonging. The samples have been characterized by X-ray powder diffraction (XRD) and scanning electron microscopy (SEM) measurement. XRD pattern confirmed that the as-prepared ZnO was the single-phase wurtzite structure formation. SEM results showed that the samples were rod textures. The surface-related optical properties have been investigated by photoluminescence (PL) spectrum and Raman spectrum. Photoluminescence measurements showed each spectrum consists of a weak band ultraviolet (UV) band and a relatively broad visible light emission peak for the samples grown at different time. It has been found that the green emission in Raman measurement may be related to surface states. ( 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

    Characterization of reactive DC magnetron sputtered TiAlN thin films

    B. Subramanian
    Abstract Thin films of about 1,m Titanium Aluminum Nitride (TiAlN) were deposited onto mild steel substrates by reactive direct current (DC) magnetron sputtering using a target consisting of equal segments of titanium and aluminum. X-ray diffraction (XRD) analysis showed that the TiAlN phase had preferred orientations along 111 and 200 with the face-centered cubic structure. Scanning Electron Microscope (SEM) and Atomic Force Microscope (AFM) analyses indicated that the films were uniform and compact. Photoluminescence (PL) spectra reveal that TiAlN thin films are of good optical quality. Laser Raman studies revealed the presence of characteristic peaks of TiAlN at 312.5, 675, and 1187.5 cm,1. ( 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

    Effects of a yoga breath intervention alone and in combination with an exposure therapy for post-traumatic stress disorder and depression in survivors of the 2004 South-East Asia tsunami

    T. Descilo
    Descilo T, Vedamurtachar A, Gerbarg PL, Nagaraja D, Gangadhar BN, Damodaran B, Adelson B, Braslow LH, Marcus S, Brown RP. Effects of a yoga breath intervention alone and in combination with an exposure therapy for PTSD and depression in survivors of the 2004 South-East Asia tsunami. Objective:, This study evaluated the effect of a yoga breath program alone and followed by a trauma reduction exposure technique on post-traumatic stress disorder and depression in survivors of the 2004 Asian tsunami. Method:, In this non-randomized study, 183 tsunami survivors who scored 50 or above on the Post-traumatic Checklist-17 (PCL-17) were assigned by camps to one of three groups: yoga breath intervention, yoga breath intervention followed by 3,8 h of trauma reduction exposure technique or 6-week wait list. Measures for post-traumatic stress disorder (PCL-17) and depression (BDI-21) were performed at baseline and at 6, 12 and 24 weeks. Data were analyzed using anova and mixed effects regression. Results:, The effect of treatment vs. control was significant at 6 weeks (F2,178 = 279.616, P < 0.001): mean PCL-17 declined by 42.5 10.0 SD with yoga breath, 39.2 17.2 with Yoga breath + exposure and 4.6 13.2 in the control. Conclusion:, Yoga breath-based interventions may help relieve psychological distress following mass disasters. [source]

    A Nomogram for Measurement of Mitral Valve Area by Proximal Isovelocity Surface Area Method

    ECHOCARDIOGRAPHY, Issue 8 2007
    Mehmet Uzun M.D.
    Introduction: Although its accuracy has been documented in many studies, the proximal isovelocity surface area (PISA) method is not used widely for mitral valve area (MVA) measurement. In this study, we prepared a new nomogram and tested its use in MVA assessment. Material and Methods: The study included 23 patients (age: 27 5 years) with mitral stenosis, of whom 7 were in atrial fibrillation. The MVA was measured by four methods: planimetry (PL) (reference method), pressure-half time (PHT), conventional PISA (CP), and nomogram (Nomo) methods. The nomogram included two unknowns: (1) r; the radius of the first PISA section; (2) a; the length of the border opposite to the PISA angle in the triangle with both adjacent borders of 1 cm. The nomogram was also tested for its popularity potential by eight echocardiographers, none of whom were included in the author list. Results: Mean MVAPL was 1.85 0.53 cm2 (range: 0.72,2.99), mean MVAPHT was 1.72 0.56 cm2 (range: 0.91,3.30), mean MVACP was 1.69 0.45 cm2 (range: 0.97,2.54), and MVANomo was 1.70 0.44 cm2 (0.96,2.49). The nomogram correlated with planimetry (r = 0.87; P < 0.001), pressure half-time (r = 0.71; P < 0.001) and conventional PISA (r = 0.99; P = 0.000) methods. The nomogram method also correlated with planimetry in patients with atrial fibrillation (r = 0.81; P = 0.026). The echocardiographers found that the nomogram is superior to the planimetry and conventional PISA methods but inferior to the pressure half-time method in terms of simplicity. Conclusion: The new nomogram is potentially helpful in measurement of MVA. It may be used as an additional method in assessing severity of mitral stenosis. [source]


    ECHOCARDIOGRAPHY, Issue 2 2004
    Background: Identification of the responder candidates for multisite pacing is still difficult and severe heart failure, dilated left ventricle with reduced ejection fraction, prolonged QRS with left bundle branch block (LBBB) are still considered the principal indicators of ventricular desynchronization. The aim of the study was to assess if echographic ventricular desynchronization parameters measured in patients with dilated cardiomyopathy and severe heart failure are correlated with the duration of the QRS on surface electrocardiogram. Methods: This study included 51 patients aged 58.8 7.4 years with idiopathic DCM. The following parameters were measured: QRS duration; effective contraction time (ECT) measured as the interval between QRS onset and closure of aortic valve, interventricular delay (IVD) measured as the time between onset of aortic and pulmonary flow, left ventricular mechanical delay (LVD) as the time from maximal interventricular septum contraction and posterior wall contraction, posterior (P), lateral (L), and posterolateral (PL) wall delays, as the time from QRS onset to maximal wall contraction. Regional post-systolic contraction was defined in a given wall as the difference (contraction delay , ECT)> 50 ms. Results: 29 patients presented complete LBBB, 22 patients had QRS duration < 120 ms. 39 patients had a post-systolic contraction of the PL wall (32 patients of the L wall and 26 patients of the P wall). 16 patients with QRS duration <120 had a post-systolic contraction of the PL wall (as for the LBBB the rest of 39 patients). In 40 patients the sequence of regional ventricular contraction was: P-L-PL wall (16 patients with QRS < 120). LVD was > 100 ms in 36 patients (26 patients with LBBB and 10 with QRS < 120). 27 patients with LBBB and 6 with QRS < 120 ms presented IVD > 30 ms. There was no correlation between the QRS duration and the parameters listed above. Conclusions: In a population of patients with severe heart failure and dilated cardiomyopathy there is no correlation between the duration of the QRS and echocardiographic parameters of ventricular desynchronization. These results show that mechanical ventricular desynchronization can be observed in patients with a QRS duration < 120 ms. Further studies are needed to evaluate if this population could beneficiate of multisite pacing therapy. [source]

    Eslicarbazepine Acetate: A Double-blind, Add-on, Placebo-controlled Exploratory Trial in Adult Patients with Partial-onset Seizures

    EPILEPSIA, Issue 3 2007
    Christian Elger
    Summary:,Objective: To explore the efficacy and safety of eslicarbazepine acetate (BIA 2-093), a new antiepileptic drug, as adjunctive therapy in adult patients with partial epilepsy. Methods: A multicenter, double-blind, randomized, placebo-controlled study was conducted in 143 refractory patients aged 18,65 years with ,4 partial-onset seizures/month. The study consisted of a 12-week treatment period followed by a 1-week tapering off. Patients were randomly assigned to one of three groups: treatment with eslicarbazepine acetate once daily (QD, n = 50), twice daily (BID, n = 46), or placebo (PL, n = 47). The daily dose was titrated from 400 mg to 800 mg and to 1,200 mg at 4-week intervals. The proportion of responders (patients with a ,50% seizure reduction) was the primary end point. Results: The percentage of responders versus baseline showed a statistically significant difference between QD and PL groups (54% vs. 28%; 90% CI =,,, ,14; p = 0.008). The difference between the BID (41%) and PL did not reach statistical significance (90% CI =,,, ,1; p = 0.12). A significantly higher proportion of responders in weeks 5,8 was found in the QD group than in the BID group (58% vs. 33%, respectively, p = 0.022). At the end of the 12-week treatment, the number of seizure-free patients in the QD and BID groups was 24%, which was significantly different from the PL group. The incidence of adverse events was similar between the treatment groups and no drug-related serious adverse events occurred. Conclusion: Eslicarbazepine acetate was efficacious and well tolerated as an adjunctive therapy of refractory epileptic patients. [source]

    Silica Supported Submicron SiO2@Y2SiO5:Eu3+ and SiO2@Y2SiO5:Ce3+/Tb3+ Spherical Particles with a Core,Shell Structure: Sol,Gel Synthesis and Characterization

    Cuikun Lin
    Abstract X1 -Y2SiO5:Eu3+ and X1 -Y2SiO5:Ce3+ and/or Tb3+ phosphor layers have been coated on nonaggregated, monodisperse, submicron spherical SiO2 particles by a sol,gel process, followed by surface reaction at high temperature (1000 C), to give core/shell structured SiO2@Y2SiO5:Eu3+ and SiO2@Y2SiO5:Ce3+/Tb3+ particles. X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), TEM, photoluminescence (PL), low voltage cathodoluminescence (CL), and time-resolved PL spectra and lifetimes are used to characterize these materials. The XRD results indicate that X1 -Y2SiO5 layers have been successfully coated on the surface of SiO2 particles, as further verified by the FESEM and TEM images. The PL and CL studies suggest that SiO2@Y2SiO5:Eu3+, SiO2@Y2SiO5:Tb3+ (or Ce3+/Tb3+), and SiO2@Y2SiO5:Ce3+ core/shell particles exhibit red (Eu3+, 613 nm: 5D0,7F2), green (Tb3+, 542 nm: 5D4,7F5), or blue (Ce3+, 450 nm: 5d-4f) luminescence, respectively. PL excitation, emission, and time-resolved spectra demonstrate that there is an energy transfer from Ce3+ to Tb3+ in the SiO2@Y2SiO5:Ce3+,Tb3+ core/shell particles. ( Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006) [source]

    A Complex-Based Soft Template Route to PbSe Nanowires

    Yuanfang Liu
    Abstract PbSe nanowires with an average size of 8 350 nm were synthesized by the reaction of Pb(NO3)2 and Se powder at 60 C under ambient pressure. A mixture of arachidic acid (AA, n -C19H39COOH) and octadecylamine (ODA), which could form a complex with Pb2+, was employed as a soft template to control the morphology of the resultant PbSe nanowires. The products were characterized by X-ray powder diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and transmission electron microscopy. The photoluminescence (PL) spectrum of the PbSe nanowires is presented. ( Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003) [source]

    Regiospecific distribution of fatty acids in triacylglycerols and phospholipids from broad beans (Vicia faba)

    Hiromi Yoshida
    Abstract Regiospecific distributions of fatty acids of triacylglycerols (TAG) and phospholipids (PL) separated from broad beans (Vicia faba) of four cultivars (Minpo, Sanuki, Nintoku and Sanren) were investigated. The major lipid components were PL (47.5,50.5,wt-%) and TAG (47.7,50.1,wt-%), while steryl esters, hydrocarbons, free fatty acids, diacylglycerols and monoacylglycerols were present in minor proportions (1.6,2.4,wt-%). The PL components isolated from the four cultivars were phosphatidylcholine (56.4,58.4,wt-%), phosphatidylethanolamine (20.3,21.7,wt-%) and phosphatidylinositol (16.6,18.6,wt-%). Phosphatidylinositol was unique in that it had the highest saturated fatty acid content among these PL. The principal characteristics of the fatty acid distribution in the TAG and PL were evident in the beans: Unsaturated fatty acids were predominantly concentrated in the sn -2 position while saturated fatty acids primarily occupied the sn -1 or sn -3 position in these lipids. The lipid components and fatty acid distributions were almost the same in the four cultivars and were not influenced by genetic variability and planting location. These results could be useful information to both consumers and producers for the manufacture of traditional broad bean foods in Japan. [source]

    Supplemental dietary flaxseed oil affects both neutral and phospholipid fatty acids in cultured tilapia

    Nilson E. de Souza
    Abstract This work aimed to evaluate the neutral lipid (NL) and phospholipid (PL) classes in tilapia (Oreochromis niloticus) muscle tissue. Tilapias were raised in captivity for a period of 5,months with increasing levels (0, 1.25, 2.50, 3.75, and 5.00%) of flaxseed oil [source of ,-linolenic acid (LNA), 18:3n -3] in substitution for sunflower oil (control). The NL/PL ratio was 1.9, and 45,fatty acids were determined for both classes of lipid. The class totals of n -3 acids always increased in all treatments, while the totals for n -6 acids always decreased (p,<0.05). For a given level of flaxseed oil, the LNA contents were consistently higher, including EPA (20:5n -3) and DHA (22:6n -3). Arachidonic acid (20:4n -6) remained high in the PL but was reduced as levels of dietary flaxseed oil were increased. The n -6/n -3 ratios decreased significantly with the rise in flaxseed oil content in all treatments, and highly unsaturated fatty acid contents increased with the levels of flaxseed oil. Overall, the influence of flaxseed oil on the fatty acid composition in the contributing NL and PL classes was to increase n -3 PUFA, thus raising the nutritional value of this freshwater fish meat and, consequently, contributing to the health of consumers. [source]

    Positional distribution of fatty acids in triacylglycerols and phospholipids from adzuki beans (Vigna angularis)

    Hiromi Yoshida
    Abstract The fatty acid distributions of triacylglycerols (TAG) and major phospholipids (PL) obtained from adzuki beans (Vigna angularis) were investigated. The total lipids extracted from the beans were separated by thin-layer chromatography (TLC) into eight fractions. The major lipid components were PL (63.5,wt-%), TAG (21.2,wt-%), steryl esters (7.5,wt-%) and hydrocarbons (5.1,wt-%), while free fatty acids, diacylglycerols (1,3-DAG and 1,2-DAG) and monoacylglycerols were also present in minor proportions (0.2,1.1,wt-%). The major PL components isolated from the beans were phosphatidylcholine (45.3,wt-%), phosphatidylethanolamine (25.8,wt-%) and phosphatidylinositol (21.5,wt-%). Phosphatidylinositol was unique in that it had the highest saturated fatty acid content among the three PL. With a few exceptions, however, the principal characteristics of the fatty acid distribution in the TAG and three PL were evident in the beans: Unsaturated fatty acids were predominantly concentrated in the sn -2 position while saturated fatty acids primary occupied the sn -1 or sn -3 position in the oils of the adzuki beans. In general, these results could be useful to both consumers and producers for the manufacture of traditional adzuki foods in Japan. [source]

    Context-dependent prefrontal cortex regulation of cocaine self-administration and reinstatement behaviors in rats

    Nina C. Di Pietro
    Abstract Evidence of stimulus attribute-specificity within the prefrontal cortex (PFC) suggests that different prefrontal subregions may contribute to cocaine addiction in functionally distinct ways. Thus, the present study examined the effects of lidocaine-induced inactivation of two distinct PFC subregions, the prelimbic (PL) or dorsal agranular insular (AId) cortices, on drug-seeking and drug-taking behaviors under cocaine maintenance and reinstatement testing conditions in rats trained to self-administer 1 mg/kg cocaine under a second-order schedule of drug delivery. Throughout maintenance and reinstatement phases, rats were exposed to conditioned light cues and contextual odor or sound cues. Results showed that PL inactivation during maintenance test sessions significantly reduced drug-seeking and drug-taking behaviors, and disrupted patterns of responding in rats exposed to light,sound, but not light,odor, cues. Moreover, lidocaine-induced inactivation of the PL significantly attenuated drug-seeking behavior during cue-induced and cocaine prime-induced reinstatement in rats exposed to light,sound cues only. In contrast, AId inactivation significantly attenuated cue-induced reinstatement of drug-seeking behavior in rats exposed to light,odor cues only. Drug-seeking and drug-taking behaviors in these rats were not disrupted during maintenance and cocaine prime-induced reinstatement testing regardless of the type of contextual cues used. Together, these data suggest that PL and AId subregions play separate yet overlapping roles in regulating cocaine addiction in rats in ways that are dependent on the presence or absence of cocaine and on the types of contextual cues present in the cocaine self-administration environment. [source]

    Altered fatty acid pattern of phospholipids and triglycerides in the submandibular gland of ,3-depleted rats

    Christine Delporte
    Alteration of the phospholipid (PL) and triglyceride (TG) fatty acid pattern was recently documented in several organs of rats depleted in long-chain polyunsaturated ,3 fatty acid (,3 rats). This study extends such a knowledge to the submandibular gland. The total PL and TG content of the salivary gland was not different in control and ,3 rats. The sole ,3 fatty acids found in ,3 rats (C22:5,3 and C22:6,3) were present at levels 3,12 times lower than in control rats. The C22:5,3/C22:6,3 ratio was increased threefold in ,3 rats. The PL and TG C16:0/C16:1,7 and C18:0/C18:1,9 ratios were decreased in ,3 rats. The conversion of C18:2,6 to C20:4,6 and C22:4,6 appeared facilitated in the ,3 rats. Some of these rats were injected intravenously, 60,120 min before killing, with either a medium-chain triglyceride:fish oil emulsion or a control medium-chain triglyceride:olive oil emulsion. The former emulsion increased the PL C22:5,3 and C22:6,3 content and prevented the age-related decrease in C16:0/C16:1,7 and C18:0/C18:1,9 ratios otherwise also recorded in PL. In conclusion, these findings document an increased activity of ,9-desaturase, a more efficient conversion of C18:2,6 to its metabolites, and an impaired generation of C22:6,3 from C22:5,3 in ,3 rats. [source]

    An allosteric DNAzyme with dual RNA-cleaving and DNA-cleaving activities

    FEBS JOURNAL, Issue 11 2010
    Dazhi Jiang
    A series of RNA-cleaving or DNA-cleaving DNAzymes have been obtained by in vitro selection. However, engineering an allosteric DNAzyme with dual RNA-cleaving and DNA-cleaving activities is very challenging. We used an in vitro -selected pistol-like (PL) DNAzyme as a DNA scaffold for designing a DNAzyme with dual catalytic activities. We prepared the 46-nucleotide DNAzyme with DNA-cleaving activity (PL DNAzyme), and then grafted the deoxyribonucleotide residues from an 8,17 variant DNAzyme into the region of stem,loop I and the catalytic core of the PL DNAzyme scaffold. This deoxyribonucleotide residue grafting resulted in a DNAzyme with dual RNA-cleaving and DNA-cleaving activities (DRc DNAzyme). Drc DNAzyme has properties different from those of the original PL DNAzyme, including DNA cleavage sites and the required metal ion concentration. Interestingly, the RNA substrate and RNase A can act as effectors to mediate the DNA cleavage. Our results show that RNA-cleaving and DNA-cleaving activities simultaneously coexist in DRc DNAzyme, and the DNA cleavage activity can be reversibly regulated by a conformational transition. [source]

    Pure and Saturated Red Electroluminescent Polyfluorenes with Dopant/Host System and PLED Efficiency/Color Purity Trade-Offs

    Lei Chen
    Abstract Three kinds of red electroluminescent (EL) polymers based on polyfluorene as blue host and 2,1,3-benzothiadiazole derivatives with different emission wavelengths as red dopant units on the side chain are designed and synthesized. The influence of the photoluminescence (PL) efficiencies and emission wavelengths of red dopants on the EL efficiencies and color purities of the resulting polyfluorene copolymers of dopant/host system is investigated by adjusting the electron donating ability of the donor units in D- , -A-D typed 2,1,3-benzothiadiazole derivatives. The devices of these red-emitting polymers realize remarkable EL efficiency/color purity trade-offs. The single-layer devices with the configuration of ITO/PEDOT:PSS/Polymer/Ca/Al show pure red emission at 624 nm with a luminous efficiency of 3.83 cd A,1 and CIE of (0.63, 0.35) for PFR1, saturated red emission at 636 nm with a luminous efficiency of 2.29 cd A,1 and CIE of (0.64, 0.33) for PFR2, respectively. By introduction of an additional electron injection layer PF-EP(Ethanol soluble phosphonate-functionalized polyfluorene), high performance pure and saturated red emission two-layer devices (ITO/PEDOT:PSS/Polymer/PF-EP/LiF/Al) were achieved with maximum luminous efficiencies of 5.50 cd A,1 and CIE of (0.62, 0.35) for PFR1, 3.10 cd A,1 and CIE of (0.63, 0.33) for PFR2, respectively, which are the best results for pure and saturated fluorescent red EL polymers reported so far. [source]

    Triplet Exciton and Polaron Dynamics in Phosphorescent Dye Blended Polymer Photovoltaic Devices

    Chang-Lyoul Lee
    Abstract The triplet exciton and polaron dynamics in phosphorescent dye (PtOEP) blended polymer (MEH-PPV) photovoltaic devices are investigated by quasi-steady-state photo-induced absorption (PIA) spectroscopy. According to the low-temperature PIA and photoluminescence (PL) results, the increase in strength of the triplet-triplet (T1 - Tn) absorption of MEH-PPV in the blend system originates from the triplet-triplet energy transfer from PtOEP to MEH-PPV. The PtOEP blended MEH-PPV/C60 bilayer photovoltaic device shows a roughly 30%,40% enhancement in photocurrent and power-conversion efficiency compared to the device without PtOEP. However, in contrast to the bilayer device results, the bulk heterojunction photovoltaic devices do not show a noticeable change in photocurrent and power-conversion efficiency in the presence of PtOEP. The PIA intensity, originating from the polaron state, is only slightly higher (within the experimental error), indicating that carrier generation in the bulk heterojunction is not enhanced in the presence of PtOEP. The rate and probability of the exciton dissociation between PtOEP and PCBM is much faster and higher than that of the triplet-triplet energy transfer between PtOEP and MEH-PPV. [source]

    Simultaneous Optimization of Luminance and Color Chromaticity of Phosphors Using a Nondominated Sorting Genetic Algorithm

    Asish Kumar Sharma
    Abstract Acquiring materials that simultaneously meet two or more conflicting requirements is very difficult. For instance, a situation wherein the color chromaticity and photoluminescence (PL) intensity of phosphors conflict with one another is a frequent problem. Therefore, identification of a good phosphor that simultaneously exhibits both desirable PL intensity and color chromaticity is a challenge. A high-throughput synthesis and characterization strategy that was reinforced by a nondominated sorting genetic algorithm (NSGA)-based optimization process was employed to simultaneously optimize both the PL intensity and color chromaticity of a MgO,ZnO,SrO,CaO,BaO,Al2O3,Ga2O3,MnO system. NSGA operations, such as Pareto sorting and niche sharing, and the ensuing high-throughput synthesis and characterization resulted in identification of promising green phosphors, i.e., Mn2+ -doped AB2O4 (A,=,alkali earth, B,=,Al and Ga) spinel solid solutions, for use in either plasma display panels or cold cathode fluorescent lamps. [source]

    Synthesis of Highly Fluorescent and Soluble 1,2,4-Linking Hyperbranched Poly(arylenevinylene) Featuring Intramolecular Energy Funneling

    Zengqi Xie
    Abstract The synthesis and optical properties of a highly soluble (>200,mg,mL,1) and highly fluorescent (,F in film,=,0.64) 1,2,4-linking hyperbranched poly(arylenevinylene) (1,2,4- hb -PAV) prepared via Wittig reaction of A3 (biphenyl-tricarbaldehyde) and B2 (phosphonium salt) monomers is reported. The molecular weight of 1,2,4- hb -PAV can be precisely controlled by the amount of the base (NaOCH3) used in the polymerization. The absorption and photoluminescence (PL) spectra of 1,2,4- hb -PAV shows distinct red-shifts compared to conventional 1,3,5-linking hyperbranched poly(arylenevinylene) (1,3,5- hb -PAV), attributed to the extended ,-conjugation along ortho - (1,2-) and para - (1,4-) links. The inherent energy gradient from the shorter branches to the longer conjugated stem in 1,2,4- hb -PAV enabled a characteristic energy funneling effect, which is absent in conventional hyperbranched polymer of 1,3,5- hb -PAV. [source]

    Preparation-Condition Dependence of Hybrid SiO2 -Coated CdTe Nanocrystals with Intense and Tunable Photoluminescence

    Ping Yang
    Abstract When aqueously prepared CdTe nanocrystals (NCs) are coated with a SiO2 shell containing Cd ions and a sulfur source, they show a drastic increase in photoluminescence (PL) efficiency with a significant red shift and spectral narrowing after reflux. This is ascribed to the creation of a hybrid structure characterized by the formation of CdS-like clusters in the vicinity of the NCs in the SiO2 shell. Since these clusters are close to the NCs, their effective size increases to reduce the quantum size effect. The dependences of the PL properties on the preparation conditions are systematically investigated. The PL efficiency increases from 28% to 80% in the best case with a red shift of 80,nm. The PL behaviors differ from those of normal CdTe NCs and include less temperature quenching and longer PL lifetime. The SiO2 coating enables bioconjugation with IgG without deterioration of PL efficiency, making hybrid NCs amenable for bioapplication. [source]

    High-Resolution Spectroscopic Mapping of the Chemical Contrast from Nanometer Domains in P3HT:PCBM Organic Blend Films for Solar-Cell Applications

    Xiao Wang
    Abstract A high-resolution near-field spectroscopic mapping technique is successfully applied to investigate the influence of thermal annealing on the morphology of a poly(3-hexylthiophene) and [6,6]-penyl-C61 butyric acid methyl ester (P3HT:PCBM) blend film. Based on the simultaneously recorded morphological and spectroscopic information, the interplay among the blend film morphology, the local P3HT:PCBM molecular distribution, and the P3HT photoluminescence (PL) quenching efficiency are systematically discussed. The PL and Raman signals of the electron donor (P3HT) and acceptor (PCBM) are probed at an optical resolution of approximately 10,nm, which allows the chemical nature of the different domains to be identified directly. In addition, the local PL quenching efficiency, which is related to the electron transfer from P3HT to PCBM, is quantitatively revealed. From these experimental results, it is proposed that high-resolution near-field spectroscopic imaging is capable of mapping the local chemical composition and photophysics of the P3HT:PCBM blends on a scale of a few nanometers. [source]

    Photo-induced Charge Transfer and Relaxation of Persistent Charge Carriers in Polymer/Nanocrystal Composites for Applications in Hybrid Solar Cells

    Marc Daniel Heinemann
    Abstract The photo-induced charge transfer and the dynamics of persistent charge carriers in blends of semiconducting polymers and nanocrystals are investigated. Regioregular poly(3-hexylthiophene) (P3HT) is used as the electron donor material, while the acceptor moiety is established by CdSe nanocrystals (nc-CdSe) prepared via colloidal synthesis. As a reference system, organic blends of P3HT and [6,6]-phenyl C61 -butyric acid methyl ester (PCBM) are studied as well. The light-induced charge transfer between P3HT and the acceptor materials is studied by photoluminescence (PL), photo-induced absorption (PIA) and light-induced electron spin resonance spectroscopy (LESR). Compared to neat P3HT samples, both systems show an intensified formation of polarons in the polymer upon photo-excitation, pointing out successful separation of photogenerated charge carriers. Additionally, relaxation of the persistent charge carriers is investigated, and significant differences are found between the hybrid composite and the purely organic system. While relaxation, reflected in the transient signal decay of the polaron signal, is fast in the organic system, the hybrid blends exhibit long-term persistence. The appearance of a second, slow recombination channel indicates the existence of deep trap states in the hybrid system, which leads to the capture of a large fraction of charge carriers. A change of polymer conformation due to the presence of nc-CdSe is revealed by low temperature LESR measurements and microwave saturation techniques. The impact of the different recombination behavior on the photovoltaic efficiency of both systems is discussed. [source]

    Effect of two oral doses of 17,-estradiol associated with dydrogesterone on thrombin generation in healthy menopausal women: a randomized double-blind placebo-controlled study

    Alexandra Rousseau
    Abstract Oral hormone therapy is associated with an increased risk of venous thrombosis. Drug agencies recommend the use of the lowest efficient dose to treat menopausal symptoms for a better risk/ratio profile, although this profile has not been totally investigated yet. The aim of the study was to compare the effect of the standard dose of 17,-estradiol to a lower one on thrombin generation (TG). In a 2-month study, healthy menopausal women were randomized to receive daily 1mg or 2 mg of 17,-estradiol (E1, n = 24 and E2, n = 26; respectively) with 10 mg dydrogesterone or placebo (PL, n = 22). Plasma levels factors VII, X, VIII and II were assessed before and after treatment as well as Tissue factor triggered TG, which allows the investigation of the different phases of coagulation process. The peak of thrombin was higher in hormone therapy groups (E1: 42.39 50.23 nm, E2: 31.08 85.86 nm vs. 10.52 40.63 nm in PL, P = 0.002 and P = 0.01). Time to reach the peak was also shortened (PL: 0.26 0.69 min vs. E1: ,0.26 0.80 min, E2: ,0.55 0.79 min, P <10,3 for both comparisons) and mean rate index of the propagation phase of TG was significantly increased. Among the studied clotting factors, only the levels of FVII were significantly increased after treatment administration. The two doses of 17,-estradiol induced in a similar degree an acceleration of the initiation and propagation phase of tissue factor triggered thrombin generation and a significant increase of FVII coagulant activity. [source]

    Photophysics and Photocurrent Generation in Polythiophene/Polyfluorene Copolymer Blends

    Christopher R. McNeill
    Abstract Here, studies on the evolution of photophysics and device performance with annealing of blends of poly(3-hexylthiophene) with the two polyfluorene copolymers poly((9,9-dioctylfluorene)-2,7-diyl-alt-[4,7-bis(3-hexylthien-5-yl)-2,1,3-benzothiadiazole]-2,,2,,-diyl) (F8TBT) and poly(9,9-dioctylfluorene-co-benzothiadiazole) (F8BT) are reported. In blends with F8TBT, P3HT is found to reorganize at low annealing temperatures (100,C or below), evidenced by a redshift of both absorption and photoluminescence (PL), and by a decrease in PL lifetime. Annealing to 140,C, however, is found to optimize device performance, accompanied by an increase in PL efficiency and lifetime. Grazing-incidence small-angle X-ray scattering is also performed to study the evolution in film nanomorphology with annealing, with the 140,C-annealed film showing enhanced phase separation. It is concluded that reorganization of P3HT alone is not sufficient to optimize device performance but must also be accompanied by a coarsening of the morphology to promote charge separation. The shape of the photocurrent action spectra of P3HT:F8TBT devices is also studied, aided by optical modeling of the absorption spectrum of the blend in a device structure. Changes in the shape of the photocurrent action spectra with annealing are observed, and these are attributed to changes in the relative contribution of each polymer to photocurrent as morphology and polymer conformation evolve. In particular, in as-spun films from xylene, photocurrent is preferentially generated from ordered P3HT segments attributed to the increased charge separation efficiency in ordered P3HT compared to disordered P3HT. For optimized devices, photocurrent is efficiently generated from both P3HT and F8TBT. In contrast to blends with F8TBT, P3HT is only found to reorganize in blends with F8BT at annealing temperatures of over 200,C. The low efficiency of the P3HT:F8BT system can then be attributed to poor charge generation and separation efficiencies that result from the failure of P3HT to reorganize. [source]

    Low-Threshold Distributed-Feedback Lasers Based on Pyrene-Cored Starburst Molecules with 1,3,6,8-Attached Oligo(9,9-Dialkylfluorene) Arms

    Ruidong Xia
    Abstract Here, a detailed characterization of the optical gain properties of sky-blue-light-emitting pyrene-cored 9,9-dialkylfluorene starbursts is reported; it is shown that these materials possess encouragingly low laser thresholds and relatively high thermal and environmental stability. The materials exhibit high solid-state photoluminescence (PL) quantum efficiencies (>90%) and near-single-exponential PL decay transients with excited state lifetimes of ,1.4,ns. The thin-film slab waveguide amplified spontaneous emission (ASE)-measured net gain reaches 75,78,cm,1. The ASE threshold energy is found to remain unaffected by heating at temperatures up to 130,C, 40 to 50,C above Tg. The ASE remained observable for annealing temperatures up to 170 or 200,C. 1D distributed feedback lasers with 75% fill factor and 320,nm period show optical pumping thresholds down to 38,65,Wcm,2, laser slope efficiencies up to 3.9%, and wavelength tuning ranges of ,40,nm around 471,512,nm. In addition, these lasers have relatively long operational lifetimes, with N1/2,,,1.1,,105,pulses for unencapsulated devices operated at ten times threshold in air. [source]

    Photoluminescence Detection of Biomolecules by Antibody-Functionalized Diatom Biosilica

    Debra K. Gale
    Abstract Diatoms are single-celled algae that make microscale silica shells called "frustules", which possess intricate nanoscale features imbedded within periodic two-dimensional pore arrays. In this study, antibody-functionalized diatom biosilica frustules serve as a microscale biosensor platform for selective and label-free photoluminescence (PL)-based detection of immunocomplex formation. The model antibody rabbit immunoglobulin G (IgG) is covalently attached to the frustule biosilica of the disk-shaped, 10-m diatom Cyclotella sp. by silanol amination and crosslinking steps to a surface site density of 3948,,499 IgG molecules m,2. Functionalization of the diatom biosilica with the nucleophilic IgG antibody amplifies the intrinsic blue PL of diatom biosilica by a factor of six. Furthermore, immunocomplex formation with the complimentary antigen anti-rabbit IgG further increases the peak PL intensity by at least a factor of three, whereas a non-complimentary antigen (goat anti-human IgG) does not. The nucleophilic immunocomplex increases the PL intensity by donating electrons to non-radiative defect sites on the photoluminescent diatom biosilica, thereby decreasing non-radiative electron decay and increasing radiative emission. This unique enhancement in PL emission is correlated to the antigen (goat anti-rabbit IgG) concentration, where immunocomplex binding follows a Langmuir isotherm with binding constant of 2.8,,0.7,,10,7M. [source]

    Luminescent Colloidal Dispersion of Silicon Quantum Dots from Microwave Plasma Synthesis: Exploring the Photoluminescence Behavior Across the Visible Spectrum

    Anoop Gupta
    Abstract Aiming for a more practical route to highly stable visible photoluminescence (PL) from silicon, a novel approach to produce luminescent silicon nanoparticles (Si-NPs) is developed. Single crystalline Si-NPs are synthesized by pyrolysis of silane (SiH4) in a microwave plasma reactor at very high production rates (0.1,10,g,h,1). The emission wavelength of the Si-NPs is controlled by etching them in a mixture of hydrofluoric acid and nitric acid. Emission across the entire visible spectrum is obtained by varying the etching time. It is observed that the air oxidation of the etched Si-NPs profoundly affects their optical properties, and causes their emission to blue-shift and diminish in intensity with time. Modification of the silicon surface by UV-induced hydrosilylation also causes a shift in the spectrum. The nature of the shift (red/blue) is dependent on the emission wavelength of the etched Si-NPs. In addition, the amount of shift depends on the type of organic ligand on the silicon surface and the UV exposure time. The surface modification of Si-NPs with different alkenes results in highly stable PL and allows their dispersion in a variety of organic solvents. This method of producing macroscopic quantities of Si-NPs with very high PL stability opens new avenues to applications of silicon quantum dots in optoelectronic and biological fields, and paves the way towards their commercialization. [source]

    Light-Emitting Rubrene Nanowire Arrays: A Comparison with Rubrene Single Crystals

    Jin Woo Lee
    Abstract This is a report on a new method of growth of a light-emitting rubrene nanowires array with diameters of 200,,10,nm by using organic vapor transport through Al2O3 nanoporous templates. Nanometer-scale laser confocal microscope (LCM) photoluminescence (PL) spectra and crystalline structures of the rubrene nanowires are compared with those of rubrene single crystals prepared with the same experimental conditions without the template. In the LCM PL spectra it is observed that the PL spectra and intensity varies with the detecting positions because of the crystal growth characteristics of the rubrene molecules. A single rubrene nanowire has a wider LCM PL band width than that of the rubrene single crystal. This may originate from the light emissions of the mixed polarized bands due to additional new crystallinity in the formation of the nanowires. From the current,voltage characteristic curves, the semiconducting nature of both the rubrene nanowires and single crystals is observed. [source]

    Tuning and Enhancing Photoluminescence of Light-Emitting Polymer Nanotubes through Electron-Beam Irradiation

    Young Ki Hong
    A new method for the tuning and enhancing photoluminescence (PL) characteristics of light emitting poly (3-methylthiopnehe) (P3MT) nanotubes through E-beam irradiation under atmospheric environments is reported. An E-beam generated from a linear electron accelerator (1 MeV, 1.6,,1013,8.0,,1016 electrons cm,2) is irradiated onto P3MT nanotubes including an Al2O3 template. From laser confocal microscope (LCM) PL experiments, significant enhancements in the PL intensity,up to about 90 times of an isolated single strand of the E-beam irradiated P3MT nanotubes,are observed. The luminescent color of the P3MT nanotubes changes from green to red color depending on the variation of E-beam dosage. These results might originate from the de-doping effect and the conformational modification through E-beam irradiations. Conformational changes of the E-beam irradiated P3MT nanotubes are confirmed by LCM single Raman and ultraviolet-visible (UV/Vis) absorption spectra. From UV/Vis absorption spectra, it is observed that the ,,,* transition peak and the doping induced bipolaron peaks of the P3MT nanotubes dramatically vary with E-beam irradiating conditions. [source]

    Soil organic carbon contents in long-term experimental grassland plots in the UK (Palace Leas and Park Grass) have not changed consistently in recent decades

    Abstract A recent report of widespread declines in soil organic C (SOC) in the UK over the 10,25 years until the early 2000s has focussed attention on the importance of resampling previously characterized sites to assess long-term trends in SOC contents and the importance of soils as a potentially volatile and globally significant reservoir of terrestrial C. We have used two sets of long-term experimental plots which have been under constant and known management for over a century and for which historical data exist that allow comparison over recent decades to determine what, if any, changes in SOC content have occurred. The plots used are the Palace Leas (PL) Meadow Hay Plots in north-east England (UK) established in 1897, and from the Park Grass (PG) Continuous Hay experiment established in 1856 at Rothamsted in south-east England. Collectively, these plots represent the only grassland sites in the UK under long-term management where changes in SOC over several decades can be assessed, and are probably unique in the world. The plots have received different manure and fertilizer treatment and have been under known management for at least 100 years. In 1982, total SOC contents were determined for the 0,27 cm layer of six of the PL plots using measurements of SOC concentrations, bulk density and soil depth. In 2006, the same six PL plots were resampled and SOC contents determined again. Four of the plots showed no net change in SOC content, but two plots showed net loss of SOC of 15% and 17% (amounting to decreases of 18 and 15 t C ha,1) since 1982. However, these differences in total SOC content were in a similar range to the variations in bulk density (6,31%) with changing soil water content. In 1959, the soil masses and SOC concentrations to 23 cm depth were measured on six PG plots with fertilizer and manure treatments corresponding closely with those measured on PL. In 2002, the SOC concentrations on the same plots were measured again. On three of the PG plots, SOC concentrations had declined by 2,10%, but in the other three it had increased by 4,8% between 1959 and 2002. If it is assumed that the soil bulk density had not changed over this period, the losses of SOC from the top soils ranged range from 10 to 3 t C ha,1, while the gains ranged from 4 to 7 t C ha,1. When the differences with time in SOC contents for the six PL and the six PG plots were examined using paired t -tests, that is, regarding the plots as two sets of six replicate permanent grasslands, there were no significant differences between 1982 and 2006 for the PL plots or between 1959 and 2002 for the PG plots. Thus, these independent observations on similar plots at PL and PG indicate there has been no consistent decrease in SOC stocks in surface soils under old, permanent grassland in England in recent decades, even though meteorological records for both sites indicate significant warming of the soil and air between 1980 and 2000. Because the potential influences of changes in management or land use have been definitively excluded, and measured rather than derived bulk densities have been used to convert from SOC concentrations to SOC amounts, our observations question whether for permanent grassland in England, losses in SOC in recent decades reported elsewhere can be attributed to widespread environmental change. [source]