Browsing by Subject "Solution (Chemistry)"

Now showing 1 - 7 of 7
  • No Thumbnail Available
    Item
    Advannces in ion chromatograpy for environmental applications
    (Texas Tech University, 2003-08) Al-Horr, Rida Sadek
    Ion chromatography (IC) is a widely used analytical tool for the determination of many ionic species. Applications of ion chromatography extend over a wide range of chemical analyses. Introduction of eluent suppression in the mid-1970s extended the boundaries of conductometric detection into trace analysis. Current state-of-the-art IC systems require only water to operate, exhibit excellent reliabilities, and provide the ability of sample preconcentration and simultaneous multiple ion measurement, making them attractive for atmospheric analysis. Atmospheric particulate matter (PM) contains many inorganic and organic soluble ions. A number of those are weak acid anions that are largely undetectable in suppressed ion chromatography. An improved method that uses sequential suppressed and unsuppressed IC for the sensitive detection of both common anions and very weak acid anions has been investigated. After suppressed conductometric detection, the effluent is passed into a membrane device where KOH is passively introduced into the eluent stream using Donnan forbidden leakage. High temporal resolution measurement of atmospheric gases and constituents of atmospheric particulate matter (PM) is important to understand the chemistry and sources of atmospheric pollution. New continuous collection devices coupled with IC systems for fully automated measurement of soluble inorganic gases and soluble ionic constituents of atmospheric PM have been developed. Soluble gas collection is accomplished with a parallel plate wet denuder (PPWD). For particle collection, an automated alternating filter-based system was initially developed. This system uses two glass-fiber filters that alternate between sampling, and washing and drying. More recently, a continuous soluble particle collector (PC) of simpler design has been developed; this device does not use steam. Preceded by a denuder and interfaced with an ion chromatograph, this compact collector permits automated collection and continuous extraction of soluble anions and ammonium ion in atmospheric particulate matter. The systems have been deployed in a number of major field studies held in urban and suburban locations in the United States.
  • No Thumbnail Available
    Item
    Experiments in weak acid dissociation and theories of activated rate processes
    (Texas Tech University, 1991-05) Krishnan, Rajalakshmi
    Not available
  • No Thumbnail Available
    Item
    Exploring solvent properties of high pressure carbon dioxide via computer simulation
    (2003) Lee, Kenneth Michael; Sanchez, Isaac C.
  • No Thumbnail Available
    Item
    Fluorescent sensors for the detection of analytes in solution
    (2002) Best, Michael Douglas; Anslyn, Eric V.
    This dissertation describes work aimed at the development of fluorescent sensors for various analytes in solution. In chapter 1, an introduction to molecular recognition and sensing is presented to provide background information pertaining to research discussed in the later chapters. Here, topics such as molecular interactions in solution, single-analyte sensing using preorganized scaffolds, installation of signaling groups for detection of binding, analytical techniques for complexation and sensing using multiple component sensing ensembles are reviewed. Chapter 2 describes a project to develop a molecular sensor with a Noxide-bipyridine complex as a binding site and for signaling the association. The project progressed through the synthesis towards three different sensor designs, until 2.60 was obtained containing a bis-bipyridine-tetra-N-oxide europium complex and two ammonium groups as binding sites. Binding studies were performed using a target guest, 2,3- bisphosphoglycerate (2.1), a glycolytic intermediate involved in oxygen transport regulation. A 1:1 host-guest complex was observed in 50% methanol / acetonitrile solution with a Ka of 6.70 x 105 M-1. Related glycolytic intermediates lacking a second phosphate (2.2, 2.3, 2.63), however, showed 2:1 guest to 2.60 binding. Phenylphosphate bound 1:1 with a Ka of 2.0 x 105 M-1. Finally, all compounds showed 2:1 guest to host binding with model host 2.61, which lacks the ammonium groups. The data shows that of similar glycolytic intermediates, only 2.1 undergoes 1:1 binding with 2.60 and indicates the importance of the second phosphate on the guest and the host ammoniums in forming this complex. In chapter 3, work towards the development of multiple differential sensors for small metal cations is presented. Approaches included random derivitization of resin beads with fluorophores and azacrown ethers and two attempts at synthesizing resin bound azacrown ethers and cryptands with covalently attached coumarins. Finally, in chapter 4, work concerning the construction of a Brønsted plot using compounds which could potentially form low-barrier hydrogen bonds is presented. Determination of the kinetics and acidity of a series of compounds with varying electronics at hydrogen bonding locations is discussed.
  • No Thumbnail Available
    Item
    Metallosupramolecular chemistry in aqueous solutions: applications in ribonuclease mimicry and molecular sensing
    (2006) Folmer-Andersen, Jan-Frantz Christian; Anslyn, Eric V.
    The use of kinetically labile metal ions to template designed interactions between organic ligands in aqueous solutions is described. This strategy is employed to target small biological molecules using coordinatively unsaturated metalloreceptors, which perform specific functions as a result of their association modes. Within this framework, two distinct examples are presented. The first case involves a tridentate Zn(II) complex with guanidinium-containing auxiliary groups that are constrained within the proximity of the metal center. This defines a bifunctional tetracationic cleft, which promotes the hydrolytic cleavage of a dinucleotide with cooperativity between the guanidinium groups and the Zn(II) center. The synergistic use of guanidinium residues and a metal center is also central to the activity of staphylococcal nuclease, which is one of the most active known nuclease enzymes. The second example concerns the incorporation asymmetric metal complexes into multi-component, colorimetric enantiosensors for α-amino acids. After several unsuccessful attempts, chiral vicinal diamine-Cu(II) complexes were identified as suitable receptors, and accurate spectrophotometric enantiomeric excess determinations were made for several hydrophobic α-amino acids. This system was extended for the construction of an enantioselective differential array sensor, which segregates chemo- and enantiomeric variance when sensors of opposite enantiomeric preference are included. The modality of this analysis likely parallels that of the mammalian gustatory response to α-amino acids, as actual amino acid taste receptor proteins respond with opposing enantioselectivities.
  • No Thumbnail Available
    Item
    Processing Oxide Thin Films with Light: a Path to High-Throughput Solution-Processed Oxide Electronics
    (2019-12) Daunis, Trey Benjamin
    High-throughput roll-to-roll manufacturing of solution-deposited metal oxide electronics has the potential to enable the widespread and low-cost availability of thin film electronic devices including solar panels, large-area displays and lighting, and flexible medical devices and sensors. However, several challenges have prevented the realization of this potential: (1) The processing speed of solution-deposited oxides is severely limited by the length of the annealing process, usually greater than 20 minutes, which is typically necessary to convert solution-deposited precursor films into metal oxides, (2) the quality of the resultant metal oxide films is limited by the low upper operating temperatures of low-cost, roll-to-roll compatible, plastic substrates, typically much less than 250 °C, and (3) equilibrium heating of devices to these temperatures often results in mechanical failure of the thin films due to the different thermal responses of the films and substrates. In this dissertation, we address these challenges by using light, rather than heat, as a source of energy for curing solution-deposited metal oxide thin films. We use this method to develop solution-deposited oxide thin film transistors (TFTs) on shape memory polymer (SMP) substrates. We demonstrate the direct patterning of Al₂O₃ and In₂O₃ precursor films on SMP by exposure to UV light through a shadow mask as a method to overcome the mechanical failure of blanket-coverage films during thermal annealing. The patterned precursors are then converted to oxides for the gate dielectric and the channel semiconductor of the TFTs by thermal annealing without causing damage to the films. The unexpectedly high mobility displayed by these TFTs is studied and the absorption of water from the atmosphere by the gate dielectric is identified as the cause. Finally, we demonstrate the high-speed photonic curing of ZrO₂ dielectric films on polyethylene naphthalate substrates. Using intense pulsed light to both heat and cure the oxide film in as little as 100 milliseconds without significantly heating the substrate, we achieve a process for fabricating metal oxide electronic devices that is compatible with roll-to-roll processing speeds exceeding 30 m/min.
  • No Thumbnail Available
    Item
    Solution chemistry of some group Va organometallics
    (Texas Tech University, 1976-05) Kuykendall, Gregory Lewis
    Not available