Publications by authors named "David S Jensen"

Here, we report the most comprehensive characterization of nanodiamonds (NDs) yet undertaken. Five different samples from three different vendors were analyzed by a suite of analytical techniques, including X-ray photoelectron spectroscopy (XPS), time-of-flight secondary ion mass spectrometry (ToF-SIMS), inductively coupled plasma mass spectrometry (ICP-MS), diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy, X-ray diffraction (XRD), transmission electron microscopy (TEM), electron energy loss spectroscopy (EELS), Brunauer-Emmett-Teller (BET) surface area measurements, and particle size distribution (PSD) measurements. XPS revealed the elemental compositions of the ND surfaces (83-87 at.

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We present a new method for the preparation of superhydrophobic materials by in situ aggregation of silica nanoparticles on a surface during a urea-formaldehyde (UF) polymerization. This is a one-step process in which a two-tier topography is obtained. The polymerization is carried out for 30, 60, 120, 180, and 240 min on silicon shards.

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In this study, reversed phase liquid chromatographic columns packed with superficially porous material made of a carbon core and nanodiamond-polymer shell were evaluated for the analytical characterization of proteins. The emphasis was put on the impact of pore size on the kinetic performance when analyzing large molecules. Three different types of columns possessing an average pore size of 120, 180, and 250Å were thus evaluated.

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Three mixed-mode high-performance liquid chromatography columns packed with superficially porous carbon/nanodiamond/amine-polymer particles were used to separate mixtures of cannabinoids. Columns evaluated included: (i) reversed phase (C18 ), weak anion exchange, 4.6 × 33 mm, 3.

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Here, we report efficiencies up to 112,000 plates per meter (a reduced plate height, h, of 2.22) for RP, carbon/nanodiamond/aminopolymer particles using conventional injection conditions in HPLC. This efficiency greatly exceeds our best previously reported value of 71,000 N/m (h = 3.

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We describe a method for plasma cleaning silicon surfaces in a commercial tool that removes adventitious organic contamination and enhances silane deposition. As shown by wetting, ellipsometry, and XPS, hydrogen, oxygen, and argon plasmas effectively clean Si/SiO2 surfaces. However, only hydrogen plasmas appear to enhance subsequent low-pressure chemical vapor deposition of silanes.

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Some of us recently described the fabrication of thin layer chromatography (TLC) plates from patterned carbon nanotube (CNT) forests via direct infiltration/coating of the CNTs by low pressure chemical vapor deposition (LPCVD) of silicon from SiH₄, followed by high temperature oxidation of the CNTs and Si. Herein we present an improved microfabrication process for the preparation of these TLC plates. First, a few nanometers of carbon and/or a thin film of Al₂O₃ is deposited on the CNTs.

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Article Synopsis
  • Porous graphitic carbon (PGC) particles were treated with di-tert-amylperoxide (DTAP) to improve their performance in high performance liquid chromatography (HPLC), resulting in a 5% decrease in retention factors and a 15% increase in theoretical plates after the first treatment.
  • After a second treatment, retention factors remained stable, but additional increases in plate numbers and a total 30% decrease in peak asymmetries were observed.
  • Characterization methods like scanning electron microscopy and ToF-SIMS revealed some chemical differences between treated and untreated particles, indicating that DTAP fragments were more concentrated on the functionalized PGC, while theoretical
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Article Synopsis
  • A new stationary phase for reversed-phase high performance liquid chromatography (RP HPLC) was developed using a layer-by-layer method to coat carbon core particles with poly(allylamine) and nanodiamond, resulting in mechanically stable core-shell particles.
  • The core-shell particles were thoroughly analyzed using various techniques like scanning electron microscopy and BET method, leading to insights into their physical and chemical properties.
  • Experiments showed the stationary phase can effectively separate a range of analytes under various conditions, demonstrating its stability even at extreme pH levels and high temperatures, which could enhance HPLC performance.
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We describe direct polymer attachment to hydrogen and deuterium-terminated diamond (HTD and DTD) surfaces using a radical initiator (di-tert-amyl peroxide, DTAP), a reactive monomer (styrene) and a crosslinking agent (divinylbenzene, DVB) to create polystyrene encapsulated diamond. Chemisorbed polystyrene is sulfonated with sulfuric acid in acetic acid. Surface changes were followed by X-ray photoelectron spectroscopy (XPS), time-of-flight secondary ion mass spectrometry (ToF-SIMS) and diffuse reflectance Fourier transform infrared spectroscopy (DRIFT).

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We report the formation of core-shell diamond particles for solid-phase extraction (SPE) and high-performance liquid chromatography (HPLC) made by layer-by-layer (LbL) deposition. Their synthesis begins with the amine functionalization of microdiamond by its immersion in an aqueous solution of a primary amine-containing polymer (polyallylamine (PAAm)). The amine-terminated microdiamond is then immersed in an aqueous suspension of nanodiamond, which leads to adsorption of the nanodiamond.

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