Chemistry Commons^™

Control Of The Cation Occupancies Of Mnzn Ferrite Synthesized Via Reverse Micelles, M. D. Shultz, M. J. Allsbrook, E. E. Carpenter

Chemistry Publications

Variations in cation occupancy in mixed metal ferrite systems can affect their electronic and magnetic properties. It is known that different synthesis parameters can lead to various cation distributions and the ability to tune these distributions is of great interest. This study uses the extended x-ray-absorption fine structure–IR relationship to investigate the effect of various Fe2+/Fe3+ ratios in initial synthesis conditions on cation distribution for manganesezincferrite (MZFO). Differences in the precipitated material before firing could lead to differences in the final material if fired under similar conditions. This work uses several different ratios of Fe3+/Fe2+, which will affect the initial …

Vapor Phase Nucleation On Neutral And Charged Nanoparticles: Condensation Of Supersaturated Trifluoroethanol On Mg Nanoparticles, Victor Abdelsayed, M. Samy El-Shall

Chemistry Publications

A new technique is described to study the condensation of supersaturated vapors on nanoparticles under well-defined conditions of vapor supersaturation, temperature, and carrier gas pressure. The method is applied to the condensation of supersaturated trifluoroethanol (TFE) vapor on Mg nanoparticles. The nanoparticles can be activated to act as condensation nuclei at supersaturations significantly lower than those required for homogeneous nucleation. The number of activated nanoparticles increases with increasing the vapor supersaturation. The small difference observed in the number of droplets formed on positively and negatively charged nanoparticles is attributed to the difference in the mobilities of these nanoparticles. Therefore, no …

Investigations On The Structure Of Dimethyl Sulfoxide And Acetone In Aqueous Solution, Sylvia E. Mclain, Alan K. Soper, Alenka Luzar

Chemistry Publications

Aqueous solutions of dimethyl sulfoxide (DMSO) and acetone have been investigated using neutron diffraction augmented with isotopic substitution and empirical potential structure refinement computer simulations. Each solute has been measured at two concentrations—1:20 and 1:2 solute:water mole ratios. At both concentrations for each solute, the tetrahedral hydrogen bonding network of water is largely unperturbed, though the total water molecule coordination number is reduced in the higher 1:2 concentrations. With higher concentrations of acetone, water tends to segregate into clusters, while in higher concentrations of DMSO the present study reconfirms that the structure of the liquid is dominated by DMSO-water interactions. …

Synthesis And Characterisation Of Tetra-Tetrazole Macrocycles, Andrew Bond, Adrienne Fleming, Fintan Kelleher, John Mcginley, Vipa Prajapati, Signe Skovsgaard

Articles

The syntheses of tetra-tetrazole macrocycles, containing two bis-tetrazole units linked by a variety of alkyl chain lengths from four to eight carbons, are described. The crystal structures of three of these derivatives are reported, and the molecular conformation in the solid state is compared to that of one previously reported tetra-tetrazole macrocycle and to other bis- and tris(tetrazole)benzene structures. The macrocycle conformation is influenced by the length of the alkyl chain linker, the relative orientation of the tetrazole rings on the benzene ring, and by intermolecular interactions. In the macrocycles based on 1,2-bis(tetrazole)benzene, the adjacent tetrazole rings on the benzene …

Air And Water Free Solid-Phase Synthesis Of Thiol Stabilized Au Nanoparticles With Anchored, Recyclable Dendrimer Templates, John D. Gilbertson, G. Vijayaraghavan, K. J. Stevenson, Bert D. Chandler

Chemistry Faculty Research

Solid-phase synthetic templates for Au nanoparticles were developed using Merrifield resins and polyamidoamine (PAMAM) dendrimers. This synthetic scheme affords the opportunity to prepare metal nanoparticles in the absence of air and water, and it does not necessitate phase transfer agents that can be difficult to remove in subsequent steps. Amine-terminated generation 5 PAMAM (G5NH2) dendrimers were grafted to anhydride functionalized polystyrene resin beads and alkylated with 1,2-epoxydodecane to produce G5C12anch. The anchored dendrimers bound both CoII and AuIII salts from toluene solutions at ratios comparable to those of solution phase alkyl-terminated PAMAM dendrimers. The encapsulated AuIII salts could be reduced …

Synthesis, Characterization, And Spectroscopy Of Model Molybdopterin Complexes, Sharon J. Nieter Burgmayer, Mary Kim, Rebecca Petit, Amy Rothkopf, Shadia Belhamdounia, Ying Hou, Arpad Somogyi, Diana Habel-Rodriguez, Antonio Williams, Martin L. Kirk

Chemistry Faculty Research and Scholarship

The preparation and characterization of new model complexes for the molybdenum cofactor are reported. The new models are distinctive for the inclusion of pterin-substituted dithiolene chelates and have the formulation Tp*MoX(pterin-R-dithiolene) (Tp* = tris(3,5,-dimethylpyrazolyl)borate), X= O, S, R= aryl or –C(OH)(CH₃)₂). Syntheses of Mo(4+) and (5+) complexes of two pterin-dithiolene derivatives as both oxo and sulfido compounds, and improved syntheses for pterinyl alkynes and [Et₄N][Tp*Mo^IV(S)S₄] reagents are described. Characterization methods include electrospray ionization mass spectrometry, electrochemistry, infrared spectroscopy, electron paramagnetic resonance and magnetic circular dichroism. Cyclic voltammetry reveals that the …

A Novel Class Of Metal-Directed Supramolecular Dna-Delivery Systems, Juan Noveron

Selected Works Temporary Series

No abstract provided.

Single-Crystal To Single-Crystal Phase Transitions Of Bis(N-Phenylisonicotinamide)Silver(I) Nitrate Reveal Cooperativity Properties In Porous Molecular Materials, Juan Noveron

Selected Works Temporary Series

No abstract provided.

Enhancing Fertiliser Use Efficiency For Transplanted Vegetables, Dennis Phillips, Aileen Reid, Gavin D'Adhemar

Horticulture research reports

Horticulture Australia (HAL) Project No. VG04018.

Project VG 04018 ‘Enhancing fertiliser use efficiency for transplanted vegetables’ showed that spraying highly concentrated solutions containing nitrogen over newly transplanted vegetable seedlings for between 14 and 21 days after planting can increase marketable yields by as much as 300% compared to other methods of fertiliser application. Crops that this method has been successfully tested on in this study by the W.A. Department of Agriculture and Food include iceberg and Cos lettuce, broccoli, cauliflower, Chinese cabbage (wombok), celery and cabbage.

The research was conducted on virgin sandy soils of the Swan Coastal Plain near …

Hydrophobic, Organically-Modified Silica Gels Enhance The Structure Of Encapsulated Apomyoglobin, Daryl K. Eggers, V. A. Rocha

Faculty Publications, Chemistry

Insertion of hydrophobic groups in a silica matrix, by addition of propyl- or trifluoropropyltrimethoxysilane, leads to a surprising increase in the helical content of apomyoglobin following encapsulation by the sol–gel technique

Characterization Of Power Induced Heating And Damage In Fiber Optic Probes For Near-Field Scanning Optical Microscopy, Nicholas E. Dickenson, E. S. Erickson, O. L. Mooren, R. C. Dunn

Chemistry and Biochemistry Faculty Publications

Tip-induced sample heating in near-field scanning optical microscopy (NSOM) is studied for fiber optic probes fabricated using the chemical etching technique. To characterize sample heating from etched NSOM probes, the spectra of a thermochromic polymer sample are measured as a function of probe output power, as was previously reported for pulled NSOM probes. The results reveal that sample heating increases rapidly to ~55–60°C as output powers reach ~50 nW. At higher output powers, the sample heating remains approximately constant up to the maximum power studied of ~450 nW. The sample heating profiles measured for etched NSOM probes are consistent with …

2-Aminopyrimidine-3,3,3-Triphenyl- Propanoic Acid (1/1), Mateusz F. Serafin, Kraig A. Wheeler

Faculty Research and Creative Activity

The title bimolecular compound, C4H5N3·C21H18O2, constructed from 2-aminopyrimidine and 3,3,3-triphenylpropanoic acid, forms a tetramolecular hydrogen-bonded motif via O—H...N, N—H...O and N—H...N contacts. This aggregate organizes to give crystal-packing motifs with hydrophilic and hydrophobic regions.

The Dissociation Energy Of The New Diatomic Molecules Sipb And Gepb, A Ciccioli, G Gigli, Giovanni Meloni, E Testani, National Library Of Medicine

Chemistry Faculty Publications

The diatomic molecules SiPb and GePb were for the first time identified by producing high temperature vapors of the constituent pure elements in a "double-oven-like" molecular-effusion assembly. The partial pressures of the atomic, heteronuclear, and homonuclear gaseous species observed in the vapor, namely, Si, Ge, Pb, SiPb, GePb, Pb2, Gen, and Sin (n=2-3), were mass-spectrometrically measured in the overall temperature ranges 1753-1961 K (Ge-Pb) and 1992-2314 K (Si-Pb). The dissociation energies of the new species were determined by second- and third-law analyses of both the direct dissociation reactions and isomolecular exchange reactions involving homonuclear molecules. The selected values of the …

Eddy Correlation Measurements Of The Air/Sea Flux Of Dimethylsulfide Over The North Pacific Ocean, Christa A. Marandino, Warren J. De Bruyn, Scott D. Miller, Eric S. Saltzman

Biology, Chemistry, and Environmental Sciences Faculty Articles and Research

Shipboard measurements of air/sea fluxes and sea surface concentrations of dimethylsulfide (DMS) were made over the tropical and midlatitude North Pacific Ocean. Atmospheric pressure chemical ionization mass spectrometry was used to measure DMS levels in ambient air and in air equilibrated with surface seawater drawn from a depth of 5 m. Air/sea fluxes were obtained using eddy covariance. Corrections and uncertainties involved in the calculation of fluxes from shipboard data are discussed. The surface ocean DMS concentrations measured during this study ranged from 1 to 10 nM, and atmospheric mixing ratios ranged from 20 to 1000 ppt. Air/sea fluxes ranged …

Size Dependent Magnetic Properties And Cation Inversion In Chemically Synthesized Mnfe2o4 Nanoparticles, C. N. Chinnasamy, Aria Yang, S. D. Yoon, Kailin Hsu, M. D. Shultz, E. E. Carpenter, S. Mukerjee, C. Vittoria, V. G. Harris

Chemistry Publications

MnFe2O4nanoparticles with diameters ranging from about 4to50nm were synthesized using a modified coprecipitation method. X-ray diffractograms revealed a pure phase spinel ferrite structure for all samples. Transmission electron microscopy showed that the particles consist of a mixture of both spherical (smaller) and cubic (larger) particles dictated by the reaction kinetics. The Néel temperatures (TN) of MnFe2O4 for various particle sizes were determined by using high temperature magnetometry. The ∼4nm MnFe2O4 particles showed a TN of about 320°C whereas the ∼50nm particles had a TN of about 400°C. The high Néel temperature, compared with the bulk MnFe2O4 TN of 300°C, is …

Effect Of Field Direction On Electrowetting In A Nanopore, D. Bratko, Christopher D. Daub, Kevin Leung, Alenka Luzar

Chemistry Publications

We manifest a significant influence of field direction and polarity on surface wetting, when the latter is tuned by application of an external electric field. Thermodynamics of field-induced filling of hydrocarbon-like nanopores with water is studied by open ensemble molecular simulation. Increased field strength consistently results in water-filling and electrostriction in hydrophobic nanopores. A threshold field commensurate with surface charge density of about one elementary charge per 10 nm2 suffices to render prototypical paraffin surfaces hydrophilic. When a field is applied in the direction perpendicular to the confining walls, the competition between orientational polarization and angle preferences of interfacial water …

Electrowetting At The Nanoscale, C. D. Daub, D. Bratko, K. Leung, A. Luzar

Chemistry Publications

Using molecular simulations of nano-sized aqueous droplets on a model graphite surface we demonstrate remarkable sensitivity of water contact angles to the applied electric field polarity and direction relative to the liquid/solid interface. The effect is explained by analyzing the influence of the field on interfacial hydrogen bonding in the nanodrop, which in turn affects the interfacial tensions. The observed anisotropy in droplet wetting is a new nanoscale phenomenon that has so far been elusive as, in current experimental setups, surface molecules represent a very low fraction of the total number affected by the field. Our findings may have important …

Photochemical Production Of Micromolarsuperoxidestandards In Aqueous Solutiont, T. C. Ong, D. W. King

Undergraduate Research Symposium (UGRS)

Superoxide(O2-) is a reactive free radical that rapidly undergoes disproportionation to hydrogen peroxide and oxygen. This property makes preparation of superoxide standard for instrument calibration difficult. McDowell et al. (1983) showed photolysis of ketone and alcohol as a convenient method to generate superoxide through triplet and radical intermediates reacting with molecular oxygen. This study expands on this past work and investigates detailed mechanism of the reaction.

Hydromination Of Alkynes, Enynes, And Dienes Using Titanium Catalysts, Taryn Palluccio

Undergraduate Review

No abstract provided.

Unleaded Drinking Water: Equilibrium Potential Measurements For Monochloramine Disinfectant, Brandi Clark

Opportunities for Undergraduate Research Experience Program (OURE)

The strength of monochloramine, NH₂CI, as an oxidizing agent can be linked to its effect on Pb levels in drinking water. In this study, the equilibrium potential was measured as a function of pH from pH 8 to 12 and compared to a theoretical plot of formal potentials derived from the Nemst equation. The measured equilibrium potential was consistently about 300 mV more negative than the calculated potential - NH₂CI is a weaker oxidizing agent than predicted. When the measured potentials are plotted on a Pourbaix diagram, it is found that NH₂CI can oxidize …

Photosensitization Of Photoconductive And Photorefractive Composites Through The Inclusion Of Semiconductor Nanocrystals, Tyler Martin Fears

Opportunities for Undergraduate Research Experience Program (OURE)

A novel synthesis of NiS nanocrystals included in photorefractive polymeric composites is described. The nanocrystals were characterized using visible-absorption spectroscopy, energy dispersive X-ray spectroscopy, and transmission electron microscopy. We further demonstrate the ability to enhance aspects of the composites' photorefractive performance by performing ligand exchange on the nanocrystals prior to their incorporation into the polymer composite. It was originally believed that this modification of the nanocrystals' surface characteristics would result in an enhanced charge-transfer process between the nanocrystal and the charge transporting matrix. However, when the photo conductivities were determined and used in calculating the quantum efficiencies associated with the …

Polymer Gels: Mimickin G Biological Environments, Joshua Carey

Opportunities for Undergraduate Research Experience Program (OURE)

A comparison of the hydrolysis of pyruvic acid in polymer gels and in aqueous environment will be studied using NMR techniques. Relaxation time and diffusion rates will be determined and compared to show the mimicking capability of the polymer gels to that of biological environments. This will allow for a means in which chemical reactions can be performed in a medium that more closely resembles the rate that the reaction would occur in biological systems.

Effects Of Monochloramine And Free Chlorine On Copper Dissolution In Drinking Water, Ryan C. Abington

Opportunities for Undergraduate Research Experience Program (OURE)

The effects of the disinfectant's free chlorine and monochloramine have been studied on thin copper films using the electrochemical quartz crystal microbalance, scanning electron microscopy and x-ray diffraction. It has been found that after twenty-four hours of immersion, the hypochlorite and the monochloramine both convert some of the copper into cuprous oxide. However, after immersion in monochloramine, tiny pinholes in the copper develop on the electrode and the gold substrate is visible underneath. This leads to suggest that while free chlorine may oxidize copper, monochloramine will oxidize copper and can cause pitting in the metal.

Single-Crystal To Single-Crystal Phase Transitions Of Bis(N-Phenylisonicotinamide)Silver(I) Nitrate Reveal Cooperativity Properties In Porous Molecular Materials, Juan Noveron

Departmental Papers (Chemistry)

No abstract provided.

Emissions From Forest Fires Near Mexico City, Robert J. Yokelson, S. P. Urbanski, E. L. Atlas, D. W. Toohey, E. C. Alvarado, J. D. Crounse, P. O. Wennberg, M. E. Fisher, C. E. Wold, T. L. Campos, K. Adachi, P. R. Buseck, Wei Min Hao

Chemistry and Biochemistry Faculty Publications

The emissions of NOx (defined as NO (nitric oxide) + NO2 (nitrogen dioxide)) and hydrogen cyanide (HCN), per unit amount of fuel burned, from fires in the pine forests that dominate the mountains surrounding Mexico City (MC) are about 2 times higher than normally observed for forest burning. The ammonia (NH3) emissions are about average for forest burning. The upper limit for the mass ratio of NOx to volatile organic compounds (VOC) for these MC-area mountain fires was similar to 0.38, which is similar to the NOx/VOC ratio in the MC urban area emissions inventory of 0.34, but much larger …

The Tropical Forest And Fire Emissions Experiment: Overview And Airborne Fire Emission Factor Measurements, Robert J. Yokelson, T. Karl, Paulo Artaxo, Donald R. Blake, Ted J. Christian, David W. T. Griffith, Alex Guenther, Wei Min Hao

Chemistry and Biochemistry Faculty Publications

The Tropical Forest and Fire Emissions Experiment (TROFFEE) used laboratory measurements followed by airborne and ground based field campaigns during the 2004 Amazon dry season to quantify the emissions from pristine tropical forest and several plantations as well as the emissions, fuel consumption, and fire ecology of tropical deforestation fires. The airborne campaign used an Embraer 110B aircraft outfitted with whole air sampling in canisters, mass-calibrated nephelometry, ozone by UV absorbance, Fourier transform infrared spectroscopy (FTIR), and proton-transfer mass spectrometry (PTR-MS) to measure PM(10), O(3), CO(2), CO, NO, NO(2), HONO, HCN, NH(3), OCS, DMS, CH(4), and up to 48 non-methane …

Molecular Mechanism Of Incorporation Of Factor Va Into Prothrombinase, Melissa Barhoover

ETD Archive

The mainstay of the blood coagulation cascade is the formation of the fibrin clot, catalyzed by the serine protease, thrombin. The prothrombinase complex catalyzes the activation of prothrombin to thrombin and, is composed of the enzyme, factor Xa, and the protein cofactor, factor Va, in the presence of divalent metal ions associated on a membrane surface. The enzyme, factor Xa, alone can activate prothrombin by two sequential proteolytic cleavages at Arg271 and Arg320 resulting in the intermediates, Fragment 1.2 and Prethrombin 2. The overall rate of this reaction is not compatible with survival. On the other hand, the incorporation of …

Characterization Of A Type Ii Metallothionein From Helianthus Annuus Using Recombinant Dna Techniques, Sridhar Bhogavalli

ETD Archive

Metallothioneins (MTs) are ubiquitous low molecular weight, cysteine rich proteins with a pronounced affinity for metal ions with d10 configuration such as Cu, Cd and Zn. These heavy metals form metal-thiolate clusters with cysteine side chains. In contrast to the vertebrate forms, knowledge about the properties of members of the plant metallothionein family is still scarce. We describe here a method of isolation and purification of metallothionein from the plant Helianthus annuus, performed by affinity chromatography using glutathione-agarose column. In this study, alignment of gene sequence of the isolated H. annuus metallothionein cDNA with known MTs showed that it belongs …

Characterization Of Polymorphic And Blended Drugs By Physical-Analytical Properties, Rajgopal Munigeti

ETD Archive

The polymorphs of Tolbutamide and Nifedipine were differentiated by measuring their unique physical properties. Differential Scanning Calorimetry (DSC) and Dielectric Analysis (DEA) verified the variations in these compounds with different crystal structures but the same chemical constituents. The crystalline-amorphous content of the polymorphs were determined based on a new DEA protocol. Solubility (w/w ) and spectroscopic methods clearly distinguished these drugs and compared favorably with the photomicrography of the polymorphs. Powder X-ray Diffraction (PXRD) analysis succintly showed differences in the various types of polymorphs. Scanning Electron Microscopy (SEM) supported the structural distinction and solubility. The FTIR spectra of all the …

Characterizatin Of A Type Ii Metallothionein From Helianthus Annuus Using Recombinant Dna Techniques, Sridhar Bhogavalli

ETD Archive

Metallothioneins (MTs) are ubiquitous low molecular weight, cysteine rich proteins with a pronounced affinity for metal ions with d10 configuration such as Cu, Cd and Zn. These heavy metals form metal-thiolate clusters with cysteine side chains. In contrast to the vertebrate forms, knowledge about the properties of members of the plant metallothionein family is still scarce. We describe here a method of isolation and purification of metallothionein from the plant Helianthus annuus, performed by affinity chromatography using glutathione-agarose column. In this study, alignment of gene sequence of the isolated H. annuus metallothionein cDNA with known MTs showed that it belongs …