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Papers by Matthew Linford
Analytical chemistry, Jan 23, 2015
We describe a new process for preparing porous solid phase microextraction (SPME) coatings by the... more We describe a new process for preparing porous solid phase microextraction (SPME) coatings by the sputtering of silicon onto silica fibers. The microstructure of these coatings is a function of the substrate geometry and mean free path of the silicon atoms, and the coating thickness is controlled by the sputtering time. Sputtered silicon structures on silica fibers were treated with piranha solution (a mixture of conc. H2SO4 and 30% H2O2) to increase the concentration of silanol groups on their surfaces, and the nanostructures were silanized with octadecyldimethylmethoxysilane in the gas phase. The attachment of this hydrophobic ligand was confirmed by X-ray photoelectron spectroscopy (XPS) and contact angle goniometry on model, planar silicon substrates. Sputtered silicon coatings adhered strongly to their surfaces, as they were able to pass the Scotch tape adhesion test. The extraction time and temperature for headspace extraction of mixtures of alkanes and alcohols on the sputter...
Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2003
We report the stability of alkyl monolayers on scribed silicon to air, water, boiling 0.1 M H 2 S... more We report the stability of alkyl monolayers on scribed silicon to air, water, boiling 0.1 M H 2 SO 4 , and X-rays. Monolayers (ML) were prepared by scribing silicon surfaces in the presence of 1-pentene, 1-octene, 1-decene, 1-hexadecene, 1chlorooctane, 1-bromopentane, 1,4-dibromobutane, methyl iodide, 1-iodopentane, 1-iododecane, 1-butanol, and 1-octanol with a computer-controlled, diamond-tipped instrument. In all cases some initial oxidation of the silicon substrate was observed by X-ray photoelectron spectroscopy (XPS), which increased with time, first rapidly, and then more slowly. Oxidation appears to proceed more quickly for silicon scribed under 1-haloalkanes than 1-alkenes, and more quickly for silicon scribed under 1-haloalkanes that were stored in air than in water. In the case of silicon scribed under an iodoalkane, the resulting iodine to silicon XPS ratio decreased with time, but even after extended exposures to air or water some iodine remained on the surfaces. Steric hindrance and/or hydrophobic effects appear to influence the degree of surface oxidation and halogen loss. The C 1s/Si 2p XPS ratios of surfaces prepared from 1-alkenes and 1-haloalkanes remain nearly constant after all exposures to air, water, hot acid and X-rays. Water capacities of hydrophobic corrals were measured in a semi-automated fashion with a Gilson 215 Liquid Handler and showed trends similar to the XPS results. Hydrophobic corrals generally retained significant fractions of their capacities to hold water with time. Sample-to-sample variation in corral capacity was attributed to variation in the scribing procedure, including possible changes in tip shape. To within experimental error no change in the amount of C, O, or Br at the surfaces was observed by XPS after nearly 4 h of illumination with monochromatic Al K␣ X-rays.
Abstract The authors report a simple method for the photoinduced chlorosulfonation of methyl-term... more Abstract The authors report a simple method for the photoinduced chlorosulfonation of methyl-terminated monolayers. These functionalized monolayer surfaces are stable to dioxane, aq. sulfuric acid and aq. ammonia at temps. near 100. degree..
Elevated temperature separations are an important current topic in liquid chromatography because ... more Elevated temperature separations are an important current topic in liquid chromatography because they offer significant benefits over those performed at ambient temperature. Here we discuss twelve such benefits, and then describe some practical considerations for implementation of elevated temperature LC.
Analytical chemistry, Jan 23, 2015
We describe a new process for preparing porous solid phase microextraction (SPME) coatings by the... more We describe a new process for preparing porous solid phase microextraction (SPME) coatings by the sputtering of silicon onto silica fibers. The microstructure of these coatings is a function of the substrate geometry and mean free path of the silicon atoms, and the coating thickness is controlled by the sputtering time. Sputtered silicon structures on silica fibers were treated with piranha solution (a mixture of conc. H2SO4 and 30% H2O2) to increase the concentration of silanol groups on their surfaces, and the nanostructures were silanized with octadecyldimethylmethoxysilane in the gas phase. The attachment of this hydrophobic ligand was confirmed by X-ray photoelectron spectroscopy (XPS) and contact angle goniometry on model, planar silicon substrates. Sputtered silicon coatings adhered strongly to their surfaces, as they were able to pass the Scotch tape adhesion test. The extraction time and temperature for headspace extraction of mixtures of alkanes and alcohols on the sputter...
Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2003
We report the stability of alkyl monolayers on scribed silicon to air, water, boiling 0.1 M H 2 S... more We report the stability of alkyl monolayers on scribed silicon to air, water, boiling 0.1 M H 2 SO 4 , and X-rays. Monolayers (ML) were prepared by scribing silicon surfaces in the presence of 1-pentene, 1-octene, 1-decene, 1-hexadecene, 1chlorooctane, 1-bromopentane, 1,4-dibromobutane, methyl iodide, 1-iodopentane, 1-iododecane, 1-butanol, and 1-octanol with a computer-controlled, diamond-tipped instrument. In all cases some initial oxidation of the silicon substrate was observed by X-ray photoelectron spectroscopy (XPS), which increased with time, first rapidly, and then more slowly. Oxidation appears to proceed more quickly for silicon scribed under 1-haloalkanes than 1-alkenes, and more quickly for silicon scribed under 1-haloalkanes that were stored in air than in water. In the case of silicon scribed under an iodoalkane, the resulting iodine to silicon XPS ratio decreased with time, but even after extended exposures to air or water some iodine remained on the surfaces. Steric hindrance and/or hydrophobic effects appear to influence the degree of surface oxidation and halogen loss. The C 1s/Si 2p XPS ratios of surfaces prepared from 1-alkenes and 1-haloalkanes remain nearly constant after all exposures to air, water, hot acid and X-rays. Water capacities of hydrophobic corrals were measured in a semi-automated fashion with a Gilson 215 Liquid Handler and showed trends similar to the XPS results. Hydrophobic corrals generally retained significant fractions of their capacities to hold water with time. Sample-to-sample variation in corral capacity was attributed to variation in the scribing procedure, including possible changes in tip shape. To within experimental error no change in the amount of C, O, or Br at the surfaces was observed by XPS after nearly 4 h of illumination with monochromatic Al K␣ X-rays.
Abstract The authors report a simple method for the photoinduced chlorosulfonation of methyl-term... more Abstract The authors report a simple method for the photoinduced chlorosulfonation of methyl-terminated monolayers. These functionalized monolayer surfaces are stable to dioxane, aq. sulfuric acid and aq. ammonia at temps. near 100. degree..
Elevated temperature separations are an important current topic in liquid chromatography because ... more Elevated temperature separations are an important current topic in liquid chromatography because they offer significant benefits over those performed at ambient temperature. Here we discuss twelve such benefits, and then describe some practical considerations for implementation of elevated temperature LC.