High‐Transconductance Organic Thin‐Film Electrochemical Transistors for Driving Low‐Voltage Red‐Green‐Blue Active Matrix Organic Light‐Emitting Devices

Switching and control of efficient red, green, and blue active matrix organic light‐emitting devices (AMOLEDs) by printed organic thin‐film electrochemical transistors (OETs) are demonstrated. These all‐organic pixels are characterized by high luminance at low operating voltages and by extremely small transistor dimensions with respect to the OLED active area. A maximum brightness of ≈900 cd m^?2 is achieved at diode supply voltages near 4 V and pixel selector (gate) voltages below 1 V. The ratio of OLED to OET area is greater than 100:1 and the pixels may be switched at rates up to 100 Hz. Essential to this demonstration are the use of a high capacitance electrolyte as the gate dielectric layer in the OETs, which affords extremely large transistor transconductances, and novel graded emissive layer (G‐EML) OLED architectures that exhibit low turn‐on voltages and high luminescence efficiency. Collectively, these results suggest that printed OETs, combined with efficient, low voltage OLEDs, could be employed in the fabrication of flexible full‐color AMOLED displays.     

Organofunctionalized montmorillonite/epoxy nanocomposites: The effect of interlayer cation distribution on mechanical properties

The present study indicates that a distribution of alkylammonium chain lengths in the interlayer of montmorillonite (MM) results in a greater degree of dispersion into an epoxy matrix (or possibly different polymer matrices) and improved ultimate tensile strengths. This hypothesis is supported by x‐ray diffraction (XRD) data from the modified MM clays, which clearly shows that an increase in d‐spacing does not result in an improvement in tensile strengths. Additional support is obtained from DSC analyses of the first and second heats of the treated clays which indicate that the C6 alkyl amine in a deposited (C18 + C6) alkyl ammonium mixture results in intercalation pathways for the epoxy resin. POLYM. COMPOS., 2011. © 2010 Society of Plastics Engineers     

An improved global model for air-sea exchange of mercury: high concentrations over the North Atlantic

We develop an improved treatment of the surface ocean in the GEOS-Chem global 3-D biogeochemical model for mercury (Hg). We replace the globally uniform subsurface ocean Hg concentrations used in the original model with basin-specific values based on measurements. Updated chemical mechanisms for Hg?/Hg(II) redox reactions in the surface ocean include both photochemical and biological processes, and we improved the parametrization of particle-associated Hg scavenging. Modeled aqueous Hg concentrations are consistent with limited surface water observations. Results more accurately reproduce high-observed MBL concentrations over the North Atlantic (NA) and the associated seasonal trends. High seasonal evasion in the NA is driven by inputs from Hg enriched subsurface waters through entrainment and Ekman pumping. Globally, subsurface waters account for 40% of Hg inputs to the ocean mixed layer, and 60% is from atmospheric deposition. Although globally the ocean is a net sink for 3.8 Mmol Hg y?1, the NA is a net source to the atmosphere, potentially due to enrichment of subsurface waters with legacy Hg from historical anthropogenic sources.     

Determining the fraction of pharmaceutical residues in wastewater originating from a hospital

Pharmaceutical residues in water are frequently analysed and discussed in connection with sewage treatment, ecotoxicity and, natural and drinking water quality. Among different localities hospitals are suspected, or implied, to be a major and highly variable source of pharmaceuticals that substantially contribute to the total wastewater load. In this study, the contribution of pharmaceuticals from a hospital to a sewage treatment plant (STP) serving around 45,000 inhabitants was evaluated. Approximately 200 hospital beds result in a hospital bed density of 4.4 beds per 1000 inhabitants, which is a typical value for developed world countries. Prior to sampling, a sound systems analysis was performed, and a sophisticated continuous flow-proportional sampling regime was applied. Hence, overall experimental uncertainty was reduced to a minimum, and measurements provide clear evidence that, for 28 of 59 investigated substances, over 85% of the pharmaceutical residue loads do not originate from the hospital when applying a conservative error estimation. Only for 2 substances, trimethoprim (18%) and roxithromycin (56%), was the maximum observed contribution of the hospital >15%. On average, the contribution of the hospital for the compounds detected in both, hospital effluent and sewage treatment plant influent was small and fairly constant. Five compounds were only detected in hospital wastewater, and 24 neither in the hospital wastewater nor in the total wastewater at the influent of the STP. For these compounds no experimental contribution could be calculated. For the compounds where audit data for both the national consumption and the specific hospital under investigation were available, a prediction of the fraction of pharmaceuticals originating from the hospital was performed. Three quarters of the compounds, classified with the existing audit data, were in the same “hospital contribution category” as determined by measurements. For most of the other compounds, plausible reasons could be identified to explain the observed deviations.     

Non-solvolytic synthesis of aqueous soluble TiO2 nanoparticles and real-time dynamic measurements of the nanoparticle formation

Highly aqueously dispersible (soluble) TiO₂ nanoparticles are usually synthesized by a solution-based sol–gel (solvolysis/condensation) process, and no direct precipitation of titania has been reported. This paper proposes a new approach to synthesize stable TiO₂ nanoparticles by a non-solvolytic method - direct liquid phase precipitation at room temperature. Ligand-capped TiO₂ nanoparticles are more readily solubilized compared to uncapped TiO₂ nanoparticles, and these capped materials show distinct optical absorbance/emission behaviors. The influence of ligands, way of reactant feeding, and post-treatment on the shape, size, crystalline structure, and surface chemistry of the TiO₂ nanoparticles has been thoroughly investigated by the combined use of X-ray diffraction, transmission electron microscopy, UV-visible (UV–vis) spectroscopy, and photoluminescence (PL). It is found that all above variables have significant effects on the size, shape, and dispersivity of the final TiO₂ nanoparticles. For the first time, real-time UV–vis spectroscopy and PL are used to dynamically detect the formation and growth of TiO₂ nanoparticles in solution. These real-time measurements show that the precipitation process begins to nucleate after an initial inhibition period of about 1 h, thereafter a particle growth occurs and reaches the maximum point after 2 h. The synthesis reaction is essentially completed after 4 h.     

Variation of Proanthocyanidins in Lotus Species

The proanthocyanidin (PA) chemistry of 12 Lotus species of previously unknown PA content was examined in comparison with agricultural cultivars of L. pedunculatus, L. corniculatus, and L. tenuis and a “creeping” selection of L. corniculatus. Herbage harvested in winter 2000 and again in spring had extractable PA concentrations, estimations of which varied between 0.2 and 10.9% of dry matter. The four novel Lotus spp. with the highest concentrations were selected for further evaluation together with the agricultural accessions. PA concentrations in herbage were estimated for individual plants harvested in spring 2001 and bulk samples harvested in summer 2002–2003. PA oligomer and polymer fractions were separated by Sephadex LH-20 chromatography from aqueous acetone PA extracts of herbage. The chemical characteristics of the fractions were examined by acid catalyzed degradation with benzyl mercaptan, ¹³C nuclear magnetic resonance spectroscopy, electrospray ionization (ESI), and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS). A wide variation was found in the chemical composition, mean degree of polymerization (mDP), and polydispersity of PAs from Lotus spp. Fractions from L. americanus, L. corniculatus “creeping selection,” and L. pedunculatus consisted predominantly of prodelphinidin (PD) units, whereas PA from L. angustissimus and L. corniculatus consisted predominantly of procyanidin (PC) units. An approximately equal composition in terms of PC and PD units was found in L. parviflorus and L. suaveolens. In L. angustissimus, epicatechin is dominant in both extender and terminal units. In all Lotus PA fractions, the 2,3-cis isomers (epicatechin or epigallocatechin) predominated. Only trace amounts of PA were extracted from L. tenuis. The mDP of the PA fractions ranged from 8 to 97, with high mDP found only for L. pedunculatus and L. americanus. In the ESI-MS and MALDI-TOF-MS of the L. angustissimus PA fraction, ions for homo-PC oligomers were dominant, whereas ions for hetero-oligomers predominated in the other Lotus spp. Ions indicative of A-type linkages were observed in the MS of L. americanus. The results are discussed in terms of possible relationships between the concentration and composition of the PAs of Lotus spp. and ecological factors.     

Intra- and interlaboratory reproducibility of ultra performance liquid chromatography-time-of-flight mass spectrometry for urinary metabolic profiling

Liquid chromatography coupled to mass spectrometry (LC-MS) is a major platform in metabolic profiling but has not yet been comprehensively assessed as to its repeatability and reproducibility across multiple spectrometers and laboratories. Here we report results of a large interlaboratory reproducibility study of ultra performance (UP) LC-MS of human urine. A total of 14 stable isotope labeled standard compounds were spiked into a pooled human urine sample, which was subject to a 2- to 16-fold dilution series and run by UPLC coupled to time-of-flight MS at three different laboratories all using the same platform. In each lab, identical samples were run in two phases, separated by at least 1 week, to assess between-day reproducibility. Overall, platform reproducibility was good with median mass accuracies below 12 ppm, median retention time drifts of less than 0.73 s and coefficients of variation of intensity of less than 18% across laboratories and ionization modes. We found that the intensity response was highly linear within each run, with a median R(2) of 0.95 and 0.93 in positive and negative ionization modes. Between-day reproducibility was also high with a mean R(2) of 0.93 for a linear relationship between the intensities of ions recorded in the two phases across the laboratories and modes. Most importantly, between-lab reproducibility was excellent with median R(2) values of 0.96 and 0.98 for positive and negative ionization modes, respectively, across all pairs of laboratories. Interestingly, the three laboratories observed different amounts of adduct formation, but this did not appear to be related to reproducibility observed in each laboratory. These studies show that UPLC-MS is fit for the purpose of targeted urinary metabolite analysis but that care must be taken to optimize laboratory systems for quantitative detection due to variable adduct formation over many compound classes.     

Determination of the hydrogen isotopic compositions of organic materials and hydrous minerals using thermal combustion laser spectroscopy

Hydrogen isotopic compositions of hydrous minerals and organic materials were measured by combustion to water, followed by optical isotopic analysis of the water vapor by off-axis integrated cavity output spectroscopy. Hydrogen and oxygen isotopic compositions were calculated by numerical integration of the individual isotopologue concentrations measured by the optical spectrometer. Rapid oxygen isotope exchange occurs within the combustion reactor between water vapor and molecular oxygen so that only hydrogen isotope compositions may be determined. Over a wide range in sample sizes, precisions were ±3-4 per mil. This is comparable but worse than continuous flow-isotope ratio mass spectroscopy (CF-IRMS) methods owing to memory effects inherent in water vapor transfer. Nevertheless, the simplicity and reduced cost of this analysis compared to classical IRMS or CF-IRMS methods make this an attractive option to determine the hydrogen isotopic composition of organic materials where the utmost precision or small sample sizes are not needed.     

Linear ion trap MS(n) of enzymatically synthesized 13C-labeled fructans revealing differentiating fragmentation patterns of β (1-2) and β (1-6) fructans and providing a tool for oligosaccharide identification in complex mixtures

Fructans are polymeric carbohydrates, which play important roles as plant reserve carbohydrates and stress protectants, and are beneficial for human health and animal production. Fructans are formed by the addition of β-d-fructofuranosyl units to sucrose, leading to very complex mixtures of 1-kestose based inulins, 6-kestose linked levans, and 6G-kestose derived neoseries inulins and levans in cool season grasses such as Lolium perenne. The identification of isomeric fructan oligomers in chromatographic analysis of crude plant extracts is often hampered by the lack of authentic standards, and unambiguous peak assignment usually requires time-consuming analyses of purified fructan oligomers. We have developed a LC-MS(n) method for the separation and detection of fructan isomers and present here evidence for specific MS(n) fragmentation patterns associated with β 1-2 (inulins) and β 2-6 (levans) fructans. LC-MS(n) analysis of (13)C labeled fructan oligomers produced by L. perenne fructosyltransferases expressed in yeast has enabled us to account for the observed fragmentation patterns in terms of preferential cleavage of the glycosidic bond between O- and fructose C2 in both inulins and levans and to differentiate reducing-end from nonreducing end cross ring cleavages in levans. We propose that higher order MS fragmentation patterns can be used to distinguish between the two major classes of fructan, i.e., inulins and levans, without the need for authentic standards.     

Systematic Evaluation of Extraction Methods for Multiplatform-Based Metabotyping: Application to the Fasciola hepatica Metabolome

Combining data from multiple analytical platforms is essential for comprehensive study of the molecular phenotype (metabotype) of a given biological sample. The metabolite profiles generated are intrinsically dependent on the analytical platforms, each requiring optimization of instrumental parameters, separation conditions, and sample extraction to deliver maximal biological information. An in-depth evaluation of extraction protocols for characterizing the metabolome of the hepatobiliary fluke Fasciola hepatica , using ultra performance liquid chromatography and capillary electrophoresis coupled with mass spectroscopy is presented. The spectrometric methods were characterized by performance, and metrics of merit were established, including precision, mass accuracy, selectivity, sensitivity, and platform stability. Although a core group of molecules was common to all methods, each platform contributed a unique set, whereby 142 metabolites out of 14,724 features were identified. A mixture design revealed that the chloroform:methanol:water proportion of 15:59:26 was globally the best composition for metabolite extraction across UPLC-MS and CE-MS platforms accommodating different columns and ionization modes. Despite the general assumption of the necessity of platform-adapted protocols for achieving effective metabotype characterization, we show that an appropriately designed single extraction procedure is able to fit the requirements of all technologies. This may constitute a paradigm shift in developing efficient protocols for high-throughput metabolite profiling with more-general analytical applicability.