The Early Diagenetic Formation of Organic Sulfur in the Sediments of Mangrove Lake, Bermuda

Due to a low mineral content, the sapropelic sediments depositing in Mangrove Lake, Bermuda, provide an excellent opportunity to explore for possible additions of sulfur to organic matter during the early stages of diagenesis. We evaluated early diagenetic organic sulfur transformations by monitoring the concentrations and stable isotopic compositions of a number of inorganic and organic sulfur pools, thereby accounting for all of the sulfur in the sediments. We have identified and quantified the following sulfur pools: porewater sulfate, porewater sulfide, elemental sulfur, pyrite sulfur, hydrolyzable organic sulfur (HYOS), chromium-reducible organic sulfur (CROS), and nonchromium-reducible organic sulfur (Non-CROS). Of the organic sulfur pools, the Non-CROS pool is by far the largest, followed by CROS, and finally HYOS. By 60 cm depth these pools contribute, respectively, to 85, 7.9, and 3.6% of the total solid phase sulfur. The HYOS pool is probably of biological origin and shows no interaction with the sulfur compounds produced during diagenesis. By contrast, CROS is produced, most likely, from the diagenetic addition of polysulfides to functionalized lipids in the upper, H2S-poor, elemental sulfur-rich, region of the sediment. A portion of this sulfur pool is unstable and decomposes on contact with the H2S-rich porewaters. The portion of CROS that remains in the sulfidic waters appears to readily exchange sulfur isotopes with H2S. While some of the Non-CROS pool is of biological origin, some is also formed by the diagenetic addition of sulfur to organic compounds in the upper H2S-poor region of the sediment. By contrast with CROS, Non-CROS is not diagenetically active in the H2S-rich porewaters. Overall, somewhere between 27 and 53 % of the organic sulfur buried in Mangrove Lake sediments is of diagenetic origin, with the remaining organic sulfur derived from biosynthesis. We extrapolate our Mangrove Lake results and calculate that in typical coastal marine sediments between 11 and 29 μmol g−1 of organic sulfur will form during early diagenesis, of which 2–5 μmol g−1 will be chromium reducible.

Distribution of organic and reduced sulfur forms in marsh soils of coastal Louisiana

Soil samples from a Louisiana Barataria Basin brackish marshes were fractionated into acid-volatile sulfides (AVS), HCl-soluble sulfur, elemental sulfur, pyrite sulfur, ester-sulfate sulfur, and carbon-bonded sulfur. Inorganic sulfur composed 13% of total sulfur in brackish marsh soil with HCl-soluble sulfur representing 63–92% of the inorganic sulfur fraction. AVS represented less than 1% of the total sulfur pool. Pyrite sulfur and elemental sulfur together accounted for 8–33% of the inorganic sulfur pool. Organic sulfur, in the forms of ester-sulfate sulfur and carbon-bonded sulfur, was the most dominant pool representing the majority of total sulfur in brackish marsh. Results were compared to values reported for fresh and salt marshes. Reported inorganic sulfur fractions were greater in adjacent marshes, constituting 24% of total sulfur in salt marsh, and 22% in freshwater marshes. Along a salinity gradient, HCl-soluble sulfur represented 78–86% of the inorganic sulfur fraction in fresh, brackish, and salt marsh. Organic sulfur in the forms of ester-sulfate sulfur and carbon-bonded sulfur was the major constituent (76–87%) of total sulfur in all marshes. Reduced sulfur species, except elemental sulfur, increased seaward along the salinity gradient. Accumulation of reduced sulfur forms through sedimentation processes was significant in marsh energy flow in fresh, brackish and salt marshes.

Red and green upconversion luminescence of Gd2O3 : Er3+, Yb3+ nanoparticles

Gd2O3:Er3+, Yb3+ nanoparticles have been synthesized by a homogeneous precipitation method with EDTA 2Na of two different concentrations. Upconversion luminescence spectra of the samples have been studied under 980 nm laser excitation. The results of XRD show that obtained Gd2O3:Er3+, Yb3+ nanoparticles are of a cubic structure. The average crystallite sizes could be calculated as 22 and 29 nm, respectively. The strong green and red upconversion emission were observed, and attributed to the H-2(11/2), S-4(3/2) -> I-4(15/2) and F-4(19/2) -> I-4(15/2) transitions of Er3+ ion, respectively.

Green synthesis of 1-2 nm gold nanoparticles stabilized by amine-terminated ionic liquid and their electrocatalytic activity in oxygen reduction

Stable gold nanoparticles with average size 1.7 nm synthesized by an amine-terminated ionic liquid showed enhanced electrocatalytic activity and high stability.

Realization of blue, green and red emission from top-emitting white organic light-emitting diodes with exterior tunable optical films

We developed an approach to realize blue, green and red emission from top-emitting white organic light-emitting diodes (OLEDs) through depositing exterior tunable optical films on top of the OLEDs. Three primary colors for full color display including blue, green and red emission are achieved by controlling the wavelength-dependent transmittance of the multilayer optical films overlaid on the emissive layer.

One-pot green synthesis of biocompatible arginine-stabilized magnetic nanoparticles

A green one-step approach has been developed for the synthesis of amino-functionalized magnetite nanoparticles. The synthesis was accomplished by simply mixing FeCl2 with arginine under ambient conditions. It was found that the Fe2+/arginine molar ratio, reaction duration and temperature greatly influence the size, morphology and composition of magnetic nanoparticles. The arginine-stabilized magnetic nanoparticles were characterized by transmission electron microscopy, x-ray diffraction, x-ray photoelectron spectroscopy, thermogravimetric analysis, and Fourier transform infrared spectroscopy techniques.

Green synthesis of nanowire-like Pt nanostructures and their catalytic properties

We reported a simple and effective green chemistry route for facile synthesis of nanowire-like Pt nanostructures atone step. In the reaction, dextran acted as a reductive agent as well as a protective agent for the synthesis of Pt nanostructures. Simple mixing of precursor aqueous solutions of dextran and K2PtCl4 at 80 degrees C could result in spontaneous formation of the Pt nanostructures. Optimization of the experiment condition could yield nanowire-like Pt nanostructures at 23:1 molar ratio of the dextran repeat unit to K2PtCl4.

Green synthesis of highly stable platinum nanoparticles stabilized by amino-terminated ionic liquid and its electrocatalysts for dioxygen reduction and methanol oxidation

Preparation of monodispersed platinum nanoparticles with average size 2.0 nm stabilized by amino-terminated ionic liquid was demonstrated. The resulting platinum nanoparticles (Pt-IL) retained long-term stability without special protection. The Pt-IL nanoparticles exhibited high electrocatalytic activity toward reduction of oxygen and oxidation of methanol. Rotating disk electrode voltammetry and rotating ring-disk electrode voltammetry confirmed that the Pt-IL films could catalyze an almost four-electron reduction of dioxygen to water.

Effect of ancillary ligands on the properties of heteroleptic green iridium dendrimers functionalized with carbazole dendrons

A series of heteroleptic green iridium dendrimers functionalized with carbazole dendrons, such as G2(pic) and G2(acac), have been synthesized, in which picolinic acid and acetylacetone are used as the ancillary ligands, respectively. Compared with the corresponding homoleptic iridium dendrimer G2 (8%), these heteroleptic ones can be prepared under mild conditions with total yields as high as 55-67%. Both the dendrimer G2(pic) and G2(acac) display bright green emissions with photoluminescence quantum yields higher than 0.80 in toluene solution. As a result, a maximum external quantum efficiency of 7.1% (21.0 cd/A) for G2(pic) and 7.7% (25.8 cd/A) for G2(acac) has been realized based on non-doped device configuration. The state-of-art performance indicates that the heteroleptic dendrimers can be promising candidates used for non-doped electrophosphorescent devices, especially when the ease of synthesis in a large scale is considered.

Controllable Red, Green, Blue (RGB) and Bright White Upconversion Luminescence of Lu2O3:Yb3+/Er3+/Tm3+ Nanocrystals through Single Laser Excitation at 980 nm

Lu2O3:Yb3+/Er3+/Tm3+ nanocrystals have been successfully synthesized by a solvothermal process followed by a subsequent heat treatment at 800 degrees C. Powder X-ray diffraction, transmission electron microscopy, upconversion photoluminescence spectra, and kinetic decay were used to characterize the samples. Under single-wavelength diode laser excitation of 980 nm, the bright blue emissions of Lu2O3:Yb3+, Tm3+ nanocrystals near 477 and 490 nm were observed due to the (1)G(4)-> H-3(6) transition of Tm3+. The bright green UC emissions of Lu2O3:Er3+ nanocrystals appeared near 540 and 565 nm were observed and assigned to the H-2(11/2)-> I-4(15/2) and S-4(3/2)-> I-4(15/2) transitions, respectively, of Er3+. The ratio of the intensity of green luminescence to that of red luminescence decreases with an increase of concentration of Yb3+ in Lu2O3:Er3+ nanocrystals.

Simultaneous blue, green, and red emission from diblock copolymer micellar films: a new approach to white-light emission

White-light emission is achieved from a single layer of diblock copolymer micelles containing green- and red-light-emitting dyes in the separate micellar cores and blue-light-emitting polymer around their periphery, in which fluorescence resonance energy transfer between fluorophores is inhibited due to micelle isolation, resulting in simultaneous emission of these three species.

High efficiency fluorescent white organic light-emitting diodes with red, green and blue separately monochromatic emission layers

Highly efficient fluorescent white organic light-emitting diodes (WOLEDs) have been fabricated by using three red, green and blue, separately monochromatic emission layers. The red and blue emissive layers are based on 4-(dicyanomethylene)-2-tert-butyl-6-(1,1,7,7-tetramethyljulolidin-4-yl-vinyl)-4H-pyran (DCJTB) doped N,N'-di(naphthalene-1-yl)-N,N'-diphenyl-benzidine (NPB) and p-bis(p-N,N-diphenyl-amino-styryl) benzene (DSA-ph) doped 2-methyl-9,10-di(2-naphthyl) anthracene (MADN), respectively; and the green emissive layer is based on tris(8-hydroxyquionline)aluminum(Alq(3)) doped with 10-(2-benzothiazolyl)-2,3,6,7-tetrahydro-1,1,7,7-tetramethyl- 1H,5H,1[H-(1)-benzopyropyrano(6,7-8-i,j)quinolizin-1]-one (C545T), which is sandwiched between the red and the blue emissive layers. It can be seen that the devices show stable white emission with Commission International de L'Eclairage coordinates of (0.41, 0.41) and color rendering index (CRI) of 84 in a wide range of bias voltages.

Bridged triphenylamines as novel host materials for highly efficient blue and green phosphorescent OLEDs

Two bridged triphenylamine-triphenylsilane (BTPASi) hybrids have been designed as host materials for phosphorescent OLEDs; devices with the novel host materials achieve maximum external quantum efficiencies as high as 15.4% for blue and 19.7% for green electrophosphorescence.