Pacific Northwest National Laboratory

About: Pacific Northwest National Laboratory is a facility organization based out in Richland, Washington, United States. It is known for research contribution in the topics: Catalysis & Aerosol. The organization has 11581 authors who have published 27934 publications receiving 1120489 citations. The organization is also known as: PNL & PNNL.

Relationships between soil microbial biomass determined by chloroform fumigation-extraction, substrate-induced respiration, and phospholipid fatty acid analysis.

Abstract: The soil microbial biomass (SMB) is responsible for many of the cycles and transformations of nutrients in soils. Three methods of measuring and describing this pool in soil are: (1) chloroform fumigation–extraction (CFE), (2) substrate-induced respiration, and (3) total extractable phospholipid fatty acids (PLFA). This study was conducted to seek a relationship between microbial PLFA and measures of SMB. Microbial PLFA was best predicted by CFE (R2=0.77); 1 nmol of PLFA corresponded to a flush of 2.4 μg C released by fumigation. This conversion factor will be useful in discussions of microbial populations and diversity and allow comparisons to literature in which only CFE is used to describe the size of the microbial biomass.

Chemically etched open tubular and monolithic emitters for nanoelectrospray ionization mass spectrometry.

Abstract: We have developed a new procedure for fabricating fused-silica emitters for electrospray ionization-mass spectrometry (ESI-MS) in which the end of a bare fused-silica capillary is immersed into aqueous hydrofluoric acid, and water is pumped through the capillary to prevent etching of the interior Surface tension causes the etchant to climb the capillary exterior, and the etch rate in the resulting meniscus decreases as a function of distance from the bulk solution Etching continues until the silica touching the hydrofluoric acid reservoir is completely removed, essentially stopping the etch process The resulting emitters have no internal taper, making them much less prone to clogging compared to, eg, pulled emitters The high aspect ratios and extremely thin walls at the orifice facilitate very low flow rate operation; stable ESI-MS signals were obtained for model analytes from 5-μm-diameter emitters at a flow rate of 5 nL/min with a high degree of interemitter reproducibility In extensive evaluatio

Synthesis of phase-pure and monodisperse iron oxide nanoparticles by thermal decomposition

Abstract: Superparamagnetic iron oxide nanoparticles (SPIONs) are used for a wide range of biomedical applications requiring precise control over their physical and magnetic properties, which are dependent on their size and crystallographic phase. Here we present a comprehensive template for the design and synthesis of iron oxide nanoparticles with control over size, size distribution, phase, and resulting magnetic properties. We investigate critical parameters for synthesis of monodisperse SPIONs by organic thermal decomposition. Three different, commonly used, iron containing precursors (iron oleate, iron pentacarbonyl, and iron oxyhydroxide) are evaluated under a variety of synthetic conditions. We compare the suitability of these three kinetically controlled synthesis protocols, which have in common the use of iron oleate as a starting precursor or reaction intermediate, for producing nanoparticles with specific size and magnetic properties. Monodisperse particles were produced over a tunable range of sizes from approximately 2–30 nm. Reaction parameters such as precursor concentration, addition of surfactant, temperature, ramp rate, and time were adjusted to kinetically control size and size-distribution, phase, and magnetic properties. In particular, large quantities of excess surfactant (up to 25 : 1 molar ratio) alter reaction kinetics and result in larger particles with uniform size; however, there is often a trade-off between large particles and a narrow size distribution. Iron oxide phase, in addition to nanoparticle size and shape, is critical for establishing magnetic properties such as differential susceptibility (dm/dH) and anisotropy. As an example, we show the importance of obtaining the required size and iron oxide phase for application to Magnetic Particle Imaging (MPI), and describe how phase purity can be controlled. These results provide much of the information necessary to determine which iron oxide synthesis protocol is best suited to a particular application.

Design and synthesis of selective mesoporous anion traps

Abstract: Arsenic contamination of groundwater has recently commanded widespread public attention. Under many conditions, arsenic, and certain other environmentally relevant toxic metals such as chromium, exist in nature as oxyanions. Selective binding of anions is one of the most challenging problems in chemistry, biology, and materials and environmental science. In this paper we report the synthesis and use of metal-chelated ligands immobilized on mesoporous silica as novel anion binding materials. Nearly complete removal of arsenate and chromate has been achieved in the presence of competing anions for solutions containing more than 100 mg/L (ppm) toxic metal anions under a variety of conditions. Anion loading of more than 120 mg (anion)/g of adsorption materials is observed. A binding mechanism is also proposed on the basis of computer modeling. First, Cu(II) ions are bonded to ethylenediamine (EDA) ligands to form octahedral complexes on the surface of the mesoporous silica. This gives rise to positively charg...

Sulfur‐Functionalized Mesoporous Carbon

Abstract: A simple synthesis route to mesoporous carbons that contain heteroaromatic functionality is described. The sulfur-functionalized mesoporous carbon (S-FMC) materials that have been prepared show excellent thermal stability, as well as excellent hydrothermal stability, and stability over a wide range of pH values. These materials also show excellent mercury sorption performance over a broad range of pH, much broader than is possible with thiol-based functionality or most silica-based sorbents. The superior performance of these mesoporous heterocarbons as heavy-metal sorbent material is demonstrated. These materials are shown to be stable at elevated temperatures and extreme pHs, making them ideally suited as a new class of absorbent material.