Chemistry

"You'll never guess where I've been," said Patricia Shapley as she intercepted me adjacent to Noyes Laboratory on the University of Illinois campus in November, 2007. "OK, I'll bite: tell me." "I just got back from teaching environmental chemistry in Hanoi." On the word, "Hanoi," I, like any of my US contemporaries, flinched. Visions of B-52s, burning villages, and war protests flooded my head. "And you wouldn't happen to know anyone who'd want to go over there and teach analytical chemistry, would you?" she continued. In no time, I had signed up for the most fascinating experience of my career. Vietnam may have been Terre incognito previously, but it has become Terre amicus. In a land that still has one party government, I have navigated differences in culture, values, finances, expectations, and chemical problems, to the benefit of two universities, faculty on both sides of the Pacific, and (one hopes) two societies. My fellow faculty members (James Lisy, Martin Gruebele, and Anne Baranger in addition to Pat Shapley) and I have been welcomed by students, faculty, and staff, and we, in turn have hosted faculty and students in Urbana. Had anyone, at the start of my scientific career, suggested I would look forward to repeated teaching trips in Hanoi, I would have thought them daft; however, they would have been right. In recent years, Vietnam has become an economic dynamo. Labor costs are miniscule compared with First-World countries. A building boom has thus far not affected chemistry facilities at Hanoi University of Science (HUS).

A custom echelle/CCD spectrometer system has been employed for equi-librium and nonequilibrium excitation measurements in the high-voltage spark discharge. By exploitation of the large spectral information band-width of the echelle/CCD system, multiple ionization stages of argon ...

An instrument for emission, fluorescence, and scattering diagnostics of a 22 kW gas/air thermal reactor is described. Z-pair parabolic mirrors provide diffraction-limited imaging in field center, with worst-case blur over a 12.8 mm field of view having a radius of 0.044 mm rms. Either full-field filtered or transverse line dispersed viewing can occur simultaneously. Dispersion is achieved using a 2-m spectrograph f-matched to the feed optics. Examples of data show non-axisymmetric flow in a nominally laminar flow system, drop shapes in situ, and Mie scattering from soot.

Microfabrication procedure. Microfabrication processes were carried out at the Beckman Institute cleanroom at the University of Illinois. Blank 3-inch silicon (<100>, N type) wafers, typically 285 µm thick (WRS Materials, San Jose, CA) were cleaned with water and solvents and baked on a hotplate at 200 °C for 5-10 min to drive off surface-bound water. HD-4100 polyimide resist (HD MicroSystems, Parlin, NJ) was spin-coated onto the wafer at 5000 rpm using a Cee 200X spin coater (Brewer Science, Rolla, MO) to a film thickness of 4 µm (when cured). The resist edge-bead was removed with a spatula and post-baked according to the recommended procedure. The passivation mask was used to expose the polyimide on the Kasper 2001 aligner/exposure tool (Kasper Instruments, Mountain View, CA). This was followed by a postexposure bake and developed using the recommended developer PA-401D and rinsed in PA-400R solutions (HD MicroSystems, Parlin, NJ). The post-development bake was done at 150 °C for 100 s, followed by 200 °C for 100 s. The final cure was carried out on a hotplate (HP 61, Torrey Pines Scientific, Carlsbad, CA) with a nitrogen purge using an inverted glass funnel to keep oxygen levels below 800 ppm as required for the final cure. The recommended temperature

If one wishes to determine the elemental composition of a solid sample, a measurement can be made in situ or the solid can he converted to a more convenient form in which its composition can be revealed. X-ray fluorescence is the most common of the in situ methods. Because this method suffers from poor detection limits for lowatomic-number elements and usually requires samples to be extensively prepared so that effects attributable to crystal structure are reproducible, it will not be considered further here.

Accurate measurement of enzyme kinetics is an essential part of understanding the mechanisms of biochemical reactions. The typical means of studying such systems use stirred cuvettes, stopped-flow apparatus, microfluidic systems, or other small sample containers. These methods may prove to be problematic if reactants or products adsorb to or react with the container's surface. As an alternative approach, we have developed an acousticallylevitated drop reactor eventually intended to study enzymecatalyzed reaction kinetics related to free radical and oxidative stress chemistry. Microliter-scale droplet generation, reactant introduction, maintenance, and fluid removal are all important aspects in conducting reactions in a levitated drop. A three capillary bundle system has been developed to address these needs. We report kinetic measurements for both luminol chemiluminescence and the reaction of pyruvate with nicotinamide adenine dinucleotide, catalyzed by lactate dehydrogenase, to demonstrate the feasibility of using a levitated drop in conjunction with the developed capillary sample handling system as a microreactor.

The astonishing propagation of sophisticated electronics across the globe has attracted the attention of many for developing disease diagnoses, water purity measurements, and security applications using cellular telephones and the complementary metal oxide semiconductor (CMOS) cameras with which many are equipped. This Focal Point article builds on the theme of using technology already in the hands of students/consumers to teach spectrophotometry and, by extension, to suggest how one might inexpensively develop an instrumental analysis curriculum at extraordinarily low cost. A grating spectrophotometer using a white light-emitting diode (LED) light source, plastic sample cuvette, holographic transmission grating, and any camera that produces JPG files as output is described. Optical characteristics are explained and a sample working curve provided. The raw data for that curve are available as Supplementary Material on-line. The behavior of the “Cell Phone Spectrometer” is inadequate...

The utility of the high-voltage spark discharge as an analytical emission source is considered. Temporal and spatial windowing was used to reiterate well-documented characteristics of heterogeneities of the spark plasma in both time and space. Cathodes of pure magnesium and aluminum 2024 alloy were used as samples. It was shown that by using a unidirectional current waveform, and by selecting a spatial position off of the interelectrode axis, at times late in the plasma lifetime, one can obtain relatively clean emission spectra (high signal-to-background ratio). This is in contrast to recent literature reports which suggest that the high-voltage spark exclusively produces spectra which are complex and which demonstrate poor background characteristics. The dynamic range of the spark is also demonstrated to be somewhat larger than the cited work suggests. The implications of various methods of presenting experimental results for such data are discussed.

Changes in the spectrum of copper alloys excited with a unidirectional spark discharge in argon are noted when hydrogen is added to the system. Systematic enhancement in erosion of copper, but not of copper in brass or in Muntz metal, is observed. Argon spectra are also perturbed, with some cascades originating near the Ar I ionization limit enhanced while other, nearly isoenergetic, cascades terminating in the Ar I metastable levels are suppressed. Ar II emission is also enhanced in the presence of H2. Both electrode surface chemistry and plasma chemistry are affected by the hydrogen addition.

Potentiostatic current oscillations occur in electro-oxidation of aluminum alloy 2024 by ammonium peroxydisulfate in phosphoric acid, for which we find nearly periodic behavior at 60°C and cyclic bursting at 68°C. We also show that potentiostatic current oscillations occur in electro-oxidation of the same alloy by sodium dichromate in sulfuric acid. The results are discussed in terms of the separate roles of the oxidant and acid in oxidation of the alloy and dissolution of the film, respectively, and the apparent requirement that oscillatory electro-oxidation of aluminum requires a balance between oxidant strength and acid strength.

Oxidation of Horseradish Peroxidase (HRP) to Compound I (CpI) induces release of the protein from adsorbing silica surfaces. Adsorption and desorption can be modulated by changes in concentration of hydrogen peroxide in solution in contact with the adsorber. Coupling of the HRP adsorption-desorption cycles to the chemistry of the peroxidase in bulk solution by oscillations in concentration of hydrogen peroxide is postulated as a plausible explanation for a qualitative change in the dynamics of the peroxidase oscillator at low concentrations of the enzyme. We hypothesize that the relative change in the HRP concentration in solution will be most pronounced at low concentrations of the enzyme and high reactor surface-to-volume ratio.

In experiments on the kinetics of the peroxidase-oxidase oscillatory reaction in pH 5.l acetate buffer, biofilms form in less than 48 h on the quartz reactor surface. The nominally homogeneous peroxidase system shows dynamical changes in response to this biofilm growth, partially explaining subtle differences among dynamics observed over time and between laboratories. Kinetics data and model computations are correlated with micrographs of biofilm formation. It is evident that bare quartz also interacts with reaction species, so that the surface area-to-volume ratio is an important parameter on which observed dynamics depend.

Development of microfluidics has focused on carrying out chemical synthesis and analysis in eversmaller volumes of solution. In most cases, flow systems are made of either quartz, glass, or an easily moldable polymer such as polydimethylsiloxane (Whitesides 2006). As the system shrinks, the ratio Report Documentation Page Form Approved OMB No. 0704-0188 Public reporting burden for the collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing this burden, to Washington Headquarters Services, Directorate for Information Operations and Reports, 1215 Jefferson Davis Highway, Suite 1204, Arlington VA 22202-4302. Respondents should be aware that notwithstanding any other provision of law, no person shall be subject to a penalty for failing to comply with a collection of information if it does not display a currently valid OMB control number.

Number of graduate students actively involved in project: 4 Research Objective: The objective of this work is to develop the fundamental knowledge base for the design of a broad class of high-temperature reactive capture processes to treat metals-bearing liquid waste in the DOE inventory. The major thrust is devoted to understanding phenomena that govern process performance and are critical to achieving emission specifications. Research Progress and Implications: In the incineration of liquid hazardous wastes, there exist "rogue" droplets (>100 µm radius) which penetrate past the flame zone and burn as isolated droplets in the postflame gasses. Mulholland et al. [1] demonstrated that these droplets can limit the overall incineration efficiency. Hence detailed knowledge of the droplet lifetimes are essential to keeping the destruction removal efficiency in excess of the 99.99% required for these wastes. The spread in trajectory endpoints of individual evaporating droplet streams of a fuel mixture injected into a hot swirling gas turbulent diffusion flame was investigated numerically. Preliminary results indicate good agreement with the measurements reported by Mulholland et al. Correlations between endpoints and initial droplet size, initial droplet velocity, inter-droplet spacing, and droplet injection angle were investigated. The model utilizes the novel One Dimensional Turbulence (ODT) model developed by Kerstein [2] for the time developing fluid velocity and temperature fields.

Office of lntellectual Properj.law DOE Chicago Operatlons 0 Ice This report was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor any agency tbmof. nor any of their employees, makes any warranty, express or implied, or assumes any kgal liability or mponsiiility for the accuracy, completeness. or usefulness of my information, apparatus, product, or proctss disclosed or rrprrstnts that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or d c c by trade name, trademark. manufacturn. or otherwise docs not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Govcmment or any agency thereof. The views and opinions of authors cxprrsscd herein do not necestarily state or reflect those of the United States Government or any agency thereof.

Many modern spectrometric instruments use diode arrays, charge-coupled arrays, or CMOS cameras for detection and measurement. As portable or point-of-use instruments are desirable, one would expect that instruments using the cameras in cellular telephones and tablet computers would be the basis of numerous instruments. However, no mass market for such devices has yet developed. The difficulties in using megapixel CMOS cameras for scientific measurements are discussed, and promising avenues for instrument development reviewed. Inexpensive alternatives to use of the built-in camera are also mentioned, as the long-term question is whether it is better to overcome the constraints of CMOS cameras or to bypass them.

Designing a spectrometer requires knowledge of the problem to be solved, the molecules whose properties will contribute to a solution of that problem and skill in many subfields of science and engineering. A seemingly simple problem, design of an ultraviolet, visible, and near-infrared spectrometer, is used to show the reasoning behind the trade-offs in instrument design. Rather than reporting a fully optimized instrument, the Yin and Yang of design choices, leading to decisions about financial cost, materials choice, resolution, throughput, aperture, and layout are described. To limit scope, aspects such as grating blaze, electronics design, and light sources are not presented. The review illustrates the mixture of mathematical rigor, rule of thumb, esthetics, and availability of components that contribute to the art of spectrometer design.

We apply a generalized approach for model-based nonfeedback control to chaotic systems where parametric dependence on the control forces is included. The existing formalism is extended for our purpose. For chaotic iterated maps and ordinary difTerential equations, we obtain entrainment to stationary, periodic, and aperiodic goal dynamics. Applicability to general resonance spectroscopy is demonstrated.