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Articles 271 - 300 of 340

Full-Text Articles in Chemistry

Large-Scale Synthesis Of High Moment Feco Nanoparticles Using Modified Polyol Synthesis, Mehdi Zamanpour, Yajie Chen, Bolin Hu, Kyler Carroll, Zachary J. Huba, E. E. Carpenter, Laura H. Lewis, Vincent G. Harris Jan 2012

Large-Scale Synthesis Of High Moment Feco Nanoparticles Using Modified Polyol Synthesis, Mehdi Zamanpour, Yajie Chen, Bolin Hu, Kyler Carroll, Zachary J. Huba, E. E. Carpenter, Laura H. Lewis, Vincent G. Harris

Chemistry Publications

Binary alloys of Fe and Co have among the highest magnetizations of any transition metal alloy systems, but their affinity to form oxides act to reduce the magnetization of nanoparticles as their size is reduced below ∼30 nm. Here, we demonstrate the synthesis of single phase, size-controlled FeCo nanoparticles having magnetization greater than 200 emu/g via a non-aqueous method in which ethylene glycol served as solvent and reducing agent as well as surfactant. Experiments indicated pure-phase FeCo nanoparticles, having saturationmagnetization up to 221 emu/g for sizes of 20–30 nm, in single batch processes resulting in > 2 g/batch. Post-synthesis oxidation of …

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Size And Phase Control Of Cobalt-Carbide Nanoparticles Using Oh- And Cl- Anions In A Polyol Process, Zachary J. Huba, Everett E. Carpenter Jan 2012

Size And Phase Control Of Cobalt-Carbide Nanoparticles Using Oh- And Cl- Anions In A Polyol Process, Zachary J. Huba, Everett E. Carpenter

Chemistry Publications

Exchange coupled cobalt–carbide nanocomposites and single-phase Co2C nanoparticles were synthesized using the polyol process. Hydroxide and chloride anions were used to controlcarbide phase and particle shape. Synthesized Co x C nanocomposites exhibited average diameters around 300 nm. Co x C nanocomposites synthesized at 0.25 M [OH−] and [Cl−] formed clusters of capped nanorods, whereas synthesis at 0.37 M [OH−] and [Cl−] produced clusters of long blade-like particles. For single-phase Co2C, an [OH−] and [Cl−] of 0.71 M was used and produced clusters of ellipsoidal …

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The Formal [4+3] Cycloaddition Between Donor-Acceptor Cyclobutanes And Nitrones., Andrew C Stevens, Cory Palmer, Brian L Pagenkopf Feb 2011

The Formal [4+3] Cycloaddition Between Donor-Acceptor Cyclobutanes And Nitrones., Andrew C Stevens, Cory Palmer, Brian L Pagenkopf

Chemistry Publications

The formal [4+3] cycloaddition of 2-alkoxy-1,1-dicarboxylate activated donor-acceptor cyclobutanes with nitrones is disclosed. The reaction forms structurally unique oxazepines in moderate to high yield with a wide scope of nitrones. In most cases either a diastereomeric mixture or a single diastereomer may be formed, depending on the reaction conditions.

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Gram Scale Synthesis Of The C(18)-C(34) Fragment Of Amphidinolide C., Nicholas A Morra, Brian L Pagenkopf Feb 2011

Gram Scale Synthesis Of The C(18)-C(34) Fragment Of Amphidinolide C., Nicholas A Morra, Brian L Pagenkopf

Chemistry Publications

The synthesis of the C(18)-C(34) fragment of amphidinolide C has been achieved via two routes, culminating in both the shortest (11 steps) and highest yielding (26% overall yield) approaches to this segment. The highly convergent approach will facilitate the synthesis of analogues, including the C(18)-C(29) fragment of amphidinolide F. Synthetic highlights include the selective methylation of a diyne, and the highly efficient use of a second generation cobalt catalyst in the Mukaiyama oxidative cyclization to form the trans-THF ring.

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Synthesis Of High Magnetization Feco Alloys Prepared By A Modified Polyol Process, Zachary J. Huba, Kyler J. Carroll, Everett E. Carpenter Jan 2011

Synthesis Of High Magnetization Feco Alloys Prepared By A Modified Polyol Process, Zachary J. Huba, Kyler J. Carroll, Everett E. Carpenter

Chemistry Publications

High magnetization, soft ferromagnetic FeCo alloy nanoparticles were synthesized at various Fe to Co ratios using a modified polyol process. Transmission electron microscopy images revealed that Fe-rich particles had a cubic shape with a mean particle size of 100 nm, while Co-rich particles had a spherical shape. A maximum saturation magnetization of 212 emu/g was recorded for both Fe60Co40 and Fe75Co25 particles. X-ray diffraction scans at room temperatureof synthesized particles were characteristic of body-centered-cubic single-phase FeCo. Variabletemperature x-ray diffraction scans under N2 gas revealed an order–disorder transition at 600 °C and a transition …

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Spin Transition In Gd3n@C-80, Detected By Low-Temperature On-Chip Squid Technique, L. Chen, E. E. Carpenter, C. S. Hellberg, H. C. Dorn, M. Schultz, W/ Wernsdorfer, I. Chiorescu Jan 2011

Spin Transition In Gd3n@C-80, Detected By Low-Temperature On-Chip Squid Technique, L. Chen, E. E. Carpenter, C. S. Hellberg, H. C. Dorn, M. Schultz, W/ Wernsdorfer, I. Chiorescu

Chemistry Publications

We present a magnetic study of the Gd3N@C80 molecule, consisting of a Gd-trimer via a nitrogen atom, encapsulated in a C80 cage. This molecular system can be an efficient contrast agent for magnetic resonance imaging (MRI) applications. We used a low-temperature technique able to detect small magnetic signals by placing the sample in the vicinity of an on-chip SQUID. The technique implemented at the National High Magnetic Field Laboratory has the particularity of being able to operate in high magnetic fields of up to 7 T. The Gd3N@C80shows a paramagnetic behavior and …

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Characterization Of Oxidation Resistant Fe@M (M=Cr, Ni) Core@Shell Nanoparticles Prepared By A Modified Reverse Micelle Reaction, Sweta H. Naik, Kyler J. Carroll, Everett E. Carpenter Jan 2011

Characterization Of Oxidation Resistant Fe@M (M=Cr, Ni) Core@Shell Nanoparticles Prepared By A Modified Reverse Micelle Reaction, Sweta H. Naik, Kyler J. Carroll, Everett E. Carpenter

Chemistry Publications

Iron-based nanoparticles are the forerunners in the field of nanotechnology due to their high magnetizationsaturation and biocompability which affords them use in a variety of applications. However, iron-based nanoparticles, due to a high surface-to-volume ratio, suffer from oxidation and limit its practicality by lowering the magnetic moment significantly. To avoid this oxidation, the surfaces of the particles have to be passivated. One such way to accomplish this passivation is to synthesize core@shell nanoparticles that have a surface treatment of chromium or nickel. These core@shell nanoparticles have been synthesized using a reverse micelle technique. The Cr and Ni passivated ironnanoparticles were …

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Structure And Hydration Of The C4h4 •+ Ion Formed By Electron Impact Ionization Of Acetylene Clusters, Paul O. Momoh, Ahmed Hamid, Samuel A. Abrash, M. Samy El-Shall Jan 2011

Structure And Hydration Of The C4h4 •+ Ion Formed By Electron Impact Ionization Of Acetylene Clusters, Paul O. Momoh, Ahmed Hamid, Samuel A. Abrash, M. Samy El-Shall

Chemistry Publications

Here we report ion mobility experiments and theoretical studies aimed at elucidating the identity of the acetylene dimer cation and its hydrated structures. The mobility measurement indicates the presence of more than one isomer for the C4H4 •+ ion in the cluster beam. The measured average collision cross section of the C4H4 •+ isomers in helium (38.9 ± 1 Å2) is consistent with the calculated cross sections of the four most stable covalent structures calculated for the C4H4 •+ ion [methylenecyclopropene (39.9 Å2), 1,2,3-butatriene (41.1 Å2), cyclobutadiene (38.6 Å2), and vinyl acetylene …

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Bf3·Oet2 Catalyzed Reaction Of Donor-Acceptor Cyclobutanes With Terminal Alkynes: Single Step Access To 2,3-Dihydrooxepines, Ben P Machin, Brian L Pagenkopf Jan 2011

Bf3·Oet2 Catalyzed Reaction Of Donor-Acceptor Cyclobutanes With Terminal Alkynes: Single Step Access To 2,3-Dihydrooxepines, Ben P Machin, Brian L Pagenkopf

Chemistry Publications

In the presence of BF3˙OEt2 cyclobutane-1,1-diesters undergo a reaction with terminal alkynes to quickly access dihydro­oxepines.

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Ytterbium Triflate Catalyzed Synthesis Of Alkoxy-Substituted Donor-Acceptor Cyclobutanes And Their Formal [4 + 2] Cycloaddition With Imines: Stereoselective Synthesis Of Piperidines., Mahmoud M Abd Rabo Moustafa, Brian L Pagenkopf Oct 2010

Ytterbium Triflate Catalyzed Synthesis Of Alkoxy-Substituted Donor-Acceptor Cyclobutanes And Their Formal [4 + 2] Cycloaddition With Imines: Stereoselective Synthesis Of Piperidines., Mahmoud M Abd Rabo Moustafa, Brian L Pagenkopf

Chemistry Publications

A new synthesis of 2-alkoxy-1,1-cyclobutane diesters and their first use in dipolar cycloadditions is reported. Both the formation of the donor-acceptor cyclobutanes and their subsequent annulation with in situ formed imines are catalyzed by Yb(OTf)(3). Cyclobutanes with carbon donor groups give piperidines with high trans stereoselectivity.

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Formal [4 + 2] Cycloaddition Of Alkoxy-Substituted Donor-Acceptor Cyclobutanes And Aldehydes Catalyzed By Yb(Otf)3., Mahmoud M Abd Rabo Moustafa, Andrew C Stevens, Ben P Machin, Brian L Pagenkopf Oct 2010

Formal [4 + 2] Cycloaddition Of Alkoxy-Substituted Donor-Acceptor Cyclobutanes And Aldehydes Catalyzed By Yb(Otf)3., Mahmoud M Abd Rabo Moustafa, Andrew C Stevens, Ben P Machin, Brian L Pagenkopf

Chemistry Publications

The cycloaddition between 2-alkoxy-1,1-cyclobutane diesters and aromatic, heteroaromatic, or aliphatic aldehydes under Yb(OTf)(3) catalysis generates tetrahydropyrans in high yields with exclusive cis-stereochemistry.

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Diels-Alder Chemistry Of Siloles And Their Transformation Into Cyclohex-2-Ene-1,4-Cis-Diols., Andrew C Stevens, Brian L Pagenkopf Jul 2010

Diels-Alder Chemistry Of Siloles And Their Transformation Into Cyclohex-2-Ene-1,4-Cis-Diols., Andrew C Stevens, Brian L Pagenkopf

Chemistry Publications

The synthesis of siloles with substitution patterns that are continuative toward natural product synthesis are described. Their reactivity in Diels-Alder chemistry was explored through thermal, Lewis acid, and high-pressure reactions. Furthermore, bicyclic adducts were oxidatively cleaved to reveal a highly functionalized cyclohexene core.

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Chemical Reasoning Based On An Invariance Property: Bond And Lone Pair Pictures In Quantum Structural Formulas, Joseph D. Alia Jul 2010

Chemical Reasoning Based On An Invariance Property: Bond And Lone Pair Pictures In Quantum Structural Formulas, Joseph D. Alia

Chemistry Publications

Chemists use one set of orbitals when comparing to a structural formula, hybridized AOs or NBOs for example, and another for reasoning in terms of frontier orbitals, MOs usually. Chemical arguments can frequently be made in terms of energy and/or electron density without the consideration of orbitals at all. All orbital representations, orthogonal or not, within a given function space are related by linear transformation. Chemical arguments based on orbitals are really energy or electron density arguments; orbitals are linked to these observables through the use of operators. The Valency Interaction Formula, VIF, offers a system of chemical reasoning based …

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Synthesis Of 5-Azaindoles Via A Cycloaddition Reaction Between Nitriles And Donor-Acceptor Cyclopropanes., Mahmoud M Abd Rabo Moustafa, Brian L Pagenkopf Jun 2010

Synthesis Of 5-Azaindoles Via A Cycloaddition Reaction Between Nitriles And Donor-Acceptor Cyclopropanes., Mahmoud M Abd Rabo Moustafa, Brian L Pagenkopf

Chemistry Publications

A new method for the synthesis of 5-azaindole derivatives is reported. A [3+2] dipolar cycloaddition between nitriles and a 3,4-cyclopropanopiperidine followed by SeO(2) oxidation affords the target compounds in moderate to excellent yields. The divergent nature and cost effectiveness of this method makes it very suitable for combinatorial applications in the pharmaceutical industry.

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Annealing Temperature And Initial Iron Valence Ratio Effects On The Structural Characteristics Of Nanoscale Nickel Zinc Ferrite, S. Calvin, M. D. Schultz, L. Glowzenski, E. E. Carpenter Jan 2010

Annealing Temperature And Initial Iron Valence Ratio Effects On The Structural Characteristics Of Nanoscale Nickel Zinc Ferrite, S. Calvin, M. D. Schultz, L. Glowzenski, E. E. Carpenter

Chemistry Publications

Nickelzincferrite (NZFO) nanoparticles were synthesized via a reverse micelle method with a nonionic surfactant. Three different initial Fe3+/Fe2+ ratios were employed along with three different firing temperatures (200, 500, 1000 °C) to investigate the effects on the NZFO system. Extended x-rayabsorption fine structure (EXAFS) results reveal zinc loss at high annealing temperatures; at 1000 °C, the loss is nearly total for Fe3+/Fe2+ ratios other than 10:90. Annealing at 500 °C, however, appears necessary for fully incorporating the zinc and nickel into the spinel phase. The best nanoferrite was thus obtained using an initial Fe3+/Fe2+ ratio of 10:90 and a moderate …

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Dual Mode Nanoparticles: Cds Coated Iron Nanoparticles, F. N. Radwan, K. J. Carroll, E. E. Carpenter Jan 2010

Dual Mode Nanoparticles: Cds Coated Iron Nanoparticles, F. N. Radwan, K. J. Carroll, E. E. Carpenter

Chemistry Publications

Reverse micelles can be used in a sequential fashion to make core-shell nanoparticles. Using this technique it is possible to make a magnetic quantum dot, by coating an iron core with a cadmium sulfide shell. Transmission electron microscopy indicated core-shell morphology and narrow size distribution of the obtained particles. Collectively, x-ray powder diffraction and x-ray photoelectron spectroscopy verified the presence of cadmium sulfide on the surface of the nanoparticles. Optical properties of the coated particles were demonstrated using fluorescence spectroscopy. A vibrating sample magnetometer was used to determine magnetic properties. Dual mode cadmium sulfide coatediron core-shell nanoparticles make unique candidates …

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High Magnetization Aqueous Ferrofluid: A Simple One-Pot Synthesis, Kyler J. Carroll, Michael D. Schultz, Panos P. Fatouros, Everett E. Carpenter Jan 2010

High Magnetization Aqueous Ferrofluid: A Simple One-Pot Synthesis, Kyler J. Carroll, Michael D. Schultz, Panos P. Fatouros, Everett E. Carpenter

Chemistry Publications

A one-step polyol method was utilized to prepare a stable aqueous iron/iron oxide ferrofluid. The dried powders were characterized by x-ray diffraction, electron microscopy, x-ray absorption spectroscopy, and vibrating sample magnetometry for the determination of phase, morphology, and magnetic properties. To show its potential for imaging applications, the ferrofluid was also investigated as a magnetic resonance imaging contrast agent.

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Localized Surface Plasmon Resonance Enhanced Magneto-Optical Activity In Core-Shell Fe-Ag Nanoparticles, L. Wang, K. Yang, C. Clavero, A. J. Nelson, K. J. Carroll, E. E. Carpenter, R. A. Lukaszew Jan 2010

Localized Surface Plasmon Resonance Enhanced Magneto-Optical Activity In Core-Shell Fe-Ag Nanoparticles, L. Wang, K. Yang, C. Clavero, A. J. Nelson, K. J. Carroll, E. E. Carpenter, R. A. Lukaszew

Chemistry Publications

Metallic nanoparticles (NPs) are suitable platforms for miniaturized biosensing based on their optical and magneto-opticalproperties. It is possible to enhance the sensitivity of specific kinds of NPs by exploiting their optical and magneto-opticalproperties under suitable external magnetic field modulation. Here, the magneto-opticalproperties of Fe–Ag core-shell ferromagnet-noble metal NPs have been investigated as a function of the incident light frequency. For Fe–Ag NPs with a concentration ratio around 25:75, an optical absorption band centered at 3 eV due to localized surface plasmon resonance (LSPR) excitation is observed. A strong enhancement of the Faraday rotation is also observed, greatly exceeding the value …

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Spectrally Tunable Magnetic Nanoparticles Designed For Distribution/Recollection Applications, Nicholas B. Mcdowall, James R. Wilkins, Kyler J. Carroll, Jarrod D. Edwards, Jean D. Nelson, Everett E. Carpenter, Garry P. Glaspell Jan 2010

Spectrally Tunable Magnetic Nanoparticles Designed For Distribution/Recollection Applications, Nicholas B. Mcdowall, James R. Wilkins, Kyler J. Carroll, Jarrod D. Edwards, Jean D. Nelson, Everett E. Carpenter, Garry P. Glaspell

Chemistry Publications

The comprehensive goal of this research is the synthesis and characterization of nanomaterials that are spectrally tunable in terms of their electromagnetic signal, are robust, magnetic (allowing their piloted movement), and have the potential to be functionalized for the detection of CBRNE threats. Various chemical methods were utilized for synthesis of magnetic (iron) and luminescent rare earth (RE) components, and their mixtures. Effects of integrating an iron core into RE luminescent lattices (excited by UV, emit in the VIS) were investigated. The determination of the optimum balances between magnetic and luminescent components such that the magnetism was maximized while maintaining …

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Annealing Of Amorphous Fexco100-X Nanoparticles Synthesized By A Modified Aqueous Reduction Using Nabh4, Kyler J. Carroll, Daniel M. Hudgins, L. W. Brown Iii, S. D. Yoon, D. Heiman, V. G. Harris, Everett E. Carpenter Jan 2010

Annealing Of Amorphous Fexco100-X Nanoparticles Synthesized By A Modified Aqueous Reduction Using Nabh4, Kyler J. Carroll, Daniel M. Hudgins, L. W. Brown Iii, S. D. Yoon, D. Heiman, V. G. Harris, Everett E. Carpenter

Chemistry Publications

FexCo100−x nanoparticles were synthesized by aqueous reduction in iron (II) sulfate and cobalt (II) sulfate using sodium borohydride and sodium citrate. The initial concentrations of iron and cobalt were varied while maintaining an overall metal concentration of 4.60 mM. Increasing the cobalt content from 0 to 100 at. % decreased the magnetization saturation from 152 to 48 emu/g, as determined by room temperature vibrating sample magnetometry. Annealing the samples at 450 and 600 °C showed an increase in crystallite size. Powder x-ray diffraction and transmission electron microscopy was performed to determine the phases and morphology of the materials.

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Nonclassical Crystallization Of Amorphous Iron Nanoparticles By Radio Frequency Methods, Kyler J. Carroll, J. A. Pitts, Kai Zhang, A. K. Pradhan, E. E. Carpenter Jan 2010

Nonclassical Crystallization Of Amorphous Iron Nanoparticles By Radio Frequency Methods, Kyler J. Carroll, J. A. Pitts, Kai Zhang, A. K. Pradhan, E. E. Carpenter

Chemistry Publications

Amorphousironnanoparticles were synthesized using an aqueous reduction in iron(II) sulfate with sodium borohydride and sodium citrate. Various radio frequency (rf) exposure times were investigated in order to determine trends in nonclassical crystallization. RF times from 15 to 300 s revealed an increase in crystallite size from 5 to 60 nm, as determined by powde rx-ray diffraction. Also, solvent optimization revealed that ethanol produced the largest trends for increasing crystallite size without total oxidation of the samples. Magnetic characterization by room temperature vibrating sample magnetometry and high resolution transmission microscopy was performed to verify magnetic properties and particle morphology.

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Increased Yields And Simplified Purification With A Second-Generation Cobalt Catalyst For The Oxidative Formation Of Trans-Thf Rings., Cory Palmer, Nicholas A Morra, Andrew C Stevens, Barbora Bajtos, Ben P Machin, Brian L Pagenkopf Nov 2009

Increased Yields And Simplified Purification With A Second-Generation Cobalt Catalyst For The Oxidative Formation Of Trans-Thf Rings., Cory Palmer, Nicholas A Morra, Andrew C Stevens, Barbora Bajtos, Ben P Machin, Brian L Pagenkopf

Chemistry Publications

The synthesis of a second-generation cobalt catalyst for the formation of trans-THF products via the Mukaiyama aerobic oxidative cyclization is reported. Two procedures have been developed with the new water-soluble catalyst that give superior yields and greatly simplify purification compared to the previous catalysts.

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Electrochemical And Photovoltaic Properties Of Electropolymerized Poly(Thienyl-Silole)S, Joshua C. Byers, Paul M. Dicarmine, Mahmoud M. A. R. Moustafa, Xin Wang, Brian Pagenkopf, Oleg A. Semenikhin Nov 2009

Electrochemical And Photovoltaic Properties Of Electropolymerized Poly(Thienyl-Silole)S, Joshua C. Byers, Paul M. Dicarmine, Mahmoud M. A. R. Moustafa, Xin Wang, Brian Pagenkopf, Oleg A. Semenikhin

Chemistry Publications

Electrochemical and photoelectrochemical properties were studied of a series of donor−acceptor materials based on polythiophene modified with silole moieties. The materials were prepared by electrochemical anodic polymerization of 2,5-bis([2,2′-bithiophen]-5-yl)-1,1-dimethyl-3,4-diphenylsilole and 2,5-bis([2,2′-terthiophen]-5-yl)-1,1-dimethyl-3,4-diphenylsilole, as well as copolymerization of these monomers with 2,2′-bithiophene. Photocurrent measurements showed that introduction of silole resulted in a considerable enhancement of the photovoltaic properties of silole-containing materials and especially the fill factor. However, as demonstrated by Mott−Schottky measurements, electropolymerized silole-containing materials showed a substantial degree of disorder and high density of states in the midgap, which negatively affected their photovoltaic properties. Atomic force microscopy (AFM) and phase imaging …

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A General Asymmetric Aldol Reaction Of Silyl Ketene Acetals Derived From Simple Esters To Aryl Alpha-Ketoesters, Brian Pagenkopf, Julie Le Engers Oct 2009

A General Asymmetric Aldol Reaction Of Silyl Ketene Acetals Derived From Simple Esters To Aryl Alpha-Ketoesters, Brian Pagenkopf, Julie Le Engers

Chemistry Publications

No abstract provided.

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Synthesis Of Tetrahydroisoquinocarbazoles Via C-2 Alkylation Of Indoles With 2-Alkoxycyclopropanoate Esters., Barbora Bajtos, Brian L Pagenkopf Jun 2009

Synthesis Of Tetrahydroisoquinocarbazoles Via C-2 Alkylation Of Indoles With 2-Alkoxycyclopropanoate Esters., Barbora Bajtos, Brian L Pagenkopf

Chemistry Publications

A concise method for the synthesis of several tetrahydroisoquinocarbazole derivatives is reported, where the core is prepared in six steps from tryptophol in 51% overall yield. The pentacyclic analogs are constructed via a dipolar C-2 alkylation of a 3-substituted indole with a 2-alkoxycyclopropanoate ester and a SmBr(2)-HMPA mediated ketyl-alkene ring closure.

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Pictorial Quantum Chemistry, Theory And Application Of Valency Interaction Formulas, Vif, Joseph D. Alia Apr 2009

Pictorial Quantum Chemistry, Theory And Application Of Valency Interaction Formulas, Vif, Joseph D. Alia

Chemistry Publications

No abstract provided.

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Total Synthesis Of (±)-Quebrachamine Via [3+2] Cycloaddition And Efficient Chloroacetamide Photocyclization, Brian Pagenkopf, Barbora Bajtos Jan 2009

Total Synthesis Of (±)-Quebrachamine Via [3+2] Cycloaddition And Efficient Chloroacetamide Photocyclization, Brian Pagenkopf, Barbora Bajtos

Chemistry Publications

The total synthesis of (±)-quebrachamine has been completed in 13 linear steps and 17.8 % overall yield. The indole core was constructed via a formal [3+2] dipolar cycloaddition between a functionalized nitrile and donor-acceptor cyclopropane, and the synthetically challenging nine-membered ring was secured by an efficient chloroacetamide photocyclization.

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Poly(Styrene-Co-Vinylbenzylchloride-Co-Divinylbenzene) Coated Iron Oxide: Synthesis And Effects On Size And Morphology, M. D. Shultz, J. R. Marin, S. H. Naik, J. Wilkins, J. M. Laza, J. L. Vilas, M. Rodriguez, N. Perez, E. E. Carpenter Jan 2009

Poly(Styrene-Co-Vinylbenzylchloride-Co-Divinylbenzene) Coated Iron Oxide: Synthesis And Effects On Size And Morphology, M. D. Shultz, J. R. Marin, S. H. Naik, J. Wilkins, J. M. Laza, J. L. Vilas, M. Rodriguez, N. Perez, E. E. Carpenter

Chemistry Publications

Iron oxide nanoparticles were coated with a polymer synthesized from the monomers of styrene, divinylbenzene, and vinylbenzylchloride. The resultant polymer microspheres from synthesis without nanoparticle loading are primarily monodispersed with a diameter of 3.45 μm as measured by scanning electron microscopy. The addition of 1% nanoparticles by mass appears to decrease the size of the microspheres down to 2.04 μm as well as increase the polydispersity. This trend is also seen to continue as you add more nanoparticles to the system going from 3.45 μm with 0% nanoparticles down to below 1 μm for 5% nanoparticles. This indicates that the …

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One Parameter Control Of The Size Of Iron Oxide Nanoparticles Synthesized In Reverse Micelles, M. D. Shultz, W. Braxton, C. Taylor, E. E. Carpenter Jan 2009

One Parameter Control Of The Size Of Iron Oxide Nanoparticles Synthesized In Reverse Micelles, M. D. Shultz, W. Braxton, C. Taylor, E. E. Carpenter

Chemistry Publications

Iron oxide nanoparticles were synthesized via reverse micelle methods. The initial iron concentration was varied, while maintaining all other parameters constant, in order to investigate the effect of the iron concentration on the resultant iron oxide nanoparticle size. Increasing the iron concentration from 0.125M to 0.5M yielded an increase in average nanoparticle diameter from 4.71 to 7.95 nm, as measured by transmission electron microscopy. Three other concentrations between 0.125M and 0.5M showed corresponding size variations, all with statistical significance. Magnetic characterization by vibrating sample magnetometry and powder x-ray diffraction was performed to verify proper phase and material. Further insight into …

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Microscopic Dynamics Of The Orientation Of A Hydrated Nanoparticle In An Electric Field, C. D. Daub, D. Bratko, A. Towshif, A. Luzar Jan 2009

Microscopic Dynamics Of The Orientation Of A Hydrated Nanoparticle In An Electric Field, C. D. Daub, D. Bratko, A. Towshif, A. Luzar

Chemistry Publications

We use atomistic simulations to study the orientational dynamics of a nonpolar nanoparticle suspended in water and subject to an electric field. Due to molecular-level effects we describe, the torque exerted on the nanoparticle exceeds continuum-electrostatics based estimates by about a factor of two. The reorientation time of a 16.2×16.2×3.35 ̊A3 nanoparticle in a field E > 0.015V/ ̊A is an order of magnitude less than the field-free orientational time (∼ 1 ns). Surprisingly, the alignment speed is nearly independent of the nanoparticle size in this regime. These findings are relevant for design of novel nanostructures and sensors and development of …

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