|
SUMMARIES OF FY 1996
RESEARCH IN THE CHEMICAL
SCIENCES |
Separations and Analysis:
Offsite Projects
University of Alabama
Tuscaloosa, AL 35487-0336
Department of Chemistry
Clean Solvent Extraction Using Polyethylene Glycol-Based Aqueous Biphasic Systems
Aqueous biphasic systems (ABS) consist of two immiscible phases formed when certain water
soluble polymers are combined with one another or with certain inorganic salts in specific
concentrations. As two-phase systems they are suitable for carrying out liquid/liquid separations
of various solutes such as biomolecules, metal ions, and particulates. In ABS the major
component in each of the two phases is water, and thus a liquid/liquid extraction technology can
be envisioned which completely eliminates the use of volatile organic compounds (VOCs).
Elimination of VOC's has the potential to revolutionize many industrial processes by drastically
reducing potential downstream pollution while increasing safety. In addition, certain separations
where traditional oil/water techniques are not applicable or perform poorly, may be successfully
carried out utilizing ABS. The long range goal of this project is to obviate the need for VOC's in
many separation and waste remediation technologies by the development of ABS into useful
systems for the selective batch or chromatographic removal and recovery of solutes and
particulates. This goal includes: a) development of a fundamental understanding of the factors
governing solute partitioning in ABS, b) understanding phase behavior in ABS in order to attain
the ability to fine-tune the PEG-rich phase and thus solute partitioning, b) expanding the uses of
ABS by targeting applications suited to this technology, c) gaining an understanding of the
relationships between liquid/liquid ABS separations and solid-supported chromatographic ABS
separations, and d) full adaptation of ABS into both liquid/liquid and solid-supported aqueous
biphasic extraction technologies.
University of Arizona
Tucson, AZ 85721
Department of Chemistry
Raman Spectroscopy of Reversed-Phase Liquid Chromatographic Alkylsilane Stationary
Phases on Thin Silica Films
Reversed-phase liquid chromatography (RPLC) is the most popular mode of liquid
chromatography used today. The stationary phase used for RPLC typically consists of silica gel
onto which an alkylsilane layer has been covalently bound. Despite intense effort, a fundamental
understanding of the molecular basis of the separation process has not been achieved. We are
using Raman spectroscopy to characterize RPLC alkylsilane stationary phases at the molecular
level with the intent of providing greater insight into the molecular basis of retention. Several
types of stationary phase supports are currently being explored. The first type is a novel layered
structure culminating with an outer thin silica film formed by spin coating a sol-gel solution. The
sol-gel approach to the synthesis of these silica films is beneficial in that control over the
microstructure of the silica layer can be achieved. This strategy will hopefully result in silica gel
systems that are chromatographically relevant. A second type of stationary phase under
investigation is a similar sol-gel thin silica film structure, but one that contains the RPLC
stationary phase as an organic modifier. Finally, true modified-silica RPLC column packing
materials commercially available for chromatography are being investigated. Studies are underway
to further develop and refine the Raman spectroscopic characterization of these materials for
chromatographically-relevant surface coverages of alkylsilanes, and to investigate the influence
and interactions of mobile phase solvents and solutes on the structure, orientation, and order of
alkylsilane bonded phases. This work should enable the first systematic Raman spectroscopic
characterization of covalently-bonded alkylsilane stationary phase behavior at silica surfaces in
environments relevant to true RPLC systems to be performed thus furthering our understanding
of the molecular basis of retention in RPLC systems.
Auburn University
Auburn, AL 36849
Department of Chemical Engineering
Interfacial Chemistry in Solvent Extraction Systems
The microscopic interfaces, i.e., association microstructures, in acidic organophosphorus
extraction systems associated with Na+, Co2+,
Ni2+, Zn2+, and UO22+ are being
systematically investigated using various physicochemical, spectroscopic and scattering techniques
in order to resolve the physicochemical nature and structure of reversed micelles of
metal-extractant complexes, the thermodynamics of the formation and growth of reversed
micelles, the effect of organic phase additives on the structure of reversed micelles, and the
relationship between reversed micellar structure and selectivity. A new structural model-the
"open water-channel" model-for reversed micelles and a quantitative model that
relates the extractability and selectivity to the size of reversed micelles in solvent extraction
systems have been proposed and are being experimentally verified. Advanced laser techniques
(SLLS, LIF, FRAP) are being utilized to characterize the properties, structure, and dynamics of
extractant-laden liquid-liquid interfaces. A molecular modelling effort has been initiated to
examine metal-extractant species using geometry optimization and molecular dynamics
simulations. This innovative research program continues to make significant contributions directly
relevant to the science and technology of liquid-liquid extraction.
Brigham Young University
Provo, UT 84602
Department of Chemistry
Novel Macrocyclic Carriers for Proton-Coupled Liquid Membrane Transport
| Investigator(s) |
Lamb, J.D.; Bradshaw, J.S.; Shirts, R.B.; Izatt, R.M.
|
$102,000 |
| Phone | 801-378-3145 |
| E-mail |
john_lamb@byu.edu |
The metal cation selectivity of macrocyclic ligands such as crown ethers and cryptands is applied
to making cation separations in hydrophobic liquid membranes and other systems. Potential
macrocyclic ligand carriers are designed and synthesized, then screened for cation binding
characteristics using potentiometric titration, solvent extraction, calorimetry, NMR, and X-ray
crystal structure determinations. Macrocycles which demonstrate potential for separations are
then incorporated into liquid membrane systems. Focus is placed on the synthesis and
characterization of new proton ionizable macrocycles that permit coupling of cation transport to
the reverse flux of protons. Macrocycles containing acidic moieties within the macrocyclic ring
structure are particularly emphasized. State-of-the-art molecular mechanics modeling techniques
are used in the design phase of the project. Current focus is being given to a new type of polymer
inclusion membrane for stable, long-term separations. Investigation is also under way on a novel
method for mixing aqueous and nonaqueous phases in solvent extraction. This method exploits
the unusual behaviour of some hydrophobic solvents which coalesce with the water phase upon
heating, then separate on cooling. Selective extractions of metal cations using macrocyclic
extractants can be carried out rapidly by this method.
Brown University
Providence, RI 02912
Department of Chemistry
Thermal Generation of the Photoacoustic Effect
In our investigation of the photoacoustic effect in carbon suspensions, we have found that gas is
produced and that since its molar volume is so large compared with that of water, a large acoustic
wave is radiated. We plan to investigate the properties gas generation, with and to identify the the
gases and other chemical species that are produced. We believe that there is evidence for an
unusual environment for chemical synthesis since the temperatures and possibly the pressures are
high in the vicinity of the carbon particles. We plan to investigate some of the questions raised by
gas generation. We are investigating the composition of the gases.Our procedure is to use gas
chromatography to determine the composition of the gases. We believe that the fraction of energy
that goes to chemical reaction can be determined from an analysis of the reaction products and a
knowledge of the enthalpies of reaction for each of the products. In addition, we are using
transmission electron microscopy to characterize the precipitate that is found in the suspension
after irradiation. We are continuing experiments with reverse micelles in order to obtain statistics
on the accuracy of the method we have been developing. According to the theory we have
worked out, the photoacoustic experiment is capable of determining the thermal diffusivity, the
thermal conductivity, and the diameter of micelles. The data analysis for the experiments has been
difficult since the dependence of the signal on these quantities does not appear to be unique. We
also are investigating the nonlinear response of the transient grating signal that we have found
when a high power Nd:YAG laser irradiates water. The nonlinearity appears to be a result of the
response of the grating itself; that is, the generation of higher harmonics in the signal comes from
the large excursion in the index of refraction of the absorbing fluid induced by the laser.
University of California, Santa Barbara
Santa Barbara, CA 93106-5130
Materials Research Laboratory
Halocarbon Separations with Zeolitic Materials
Two environmental pressures are driving the need to develop a better understanding of separation
processes involving halocarbons. First, ozone-depleting chlorofluorocarbons (CFCs), which have
been widely used for many decades in a diverse range of technologies, are being replaced under
the Montreal Protocol by alternative halocarbons such as hydrofluorocarbons (HFCs) and
hydrochlorofluorocarbons (HCFCs). Second, there is an urgent need to remove halocarbon
solvent residues (and other organics) from a large number of contaminated sites in the U.S.A. and
elsewhere. Typically, the solvents are present in ground-water. Several pressing technical issues
arise from these important trends; the focus of this project is in halocarbon separations. The
demand for enhanced separation procedures is necessitated by the fact that halocarbon solvent
residues are frequently encountered in complex mixtures. For example, many industries combine
their solvent residues prior to returning them for reprocessing or disposal. On the other hand,
many disposal routes, which include catalytic conversions to HCFCs, are highly specific for
particular halocarbons, so that a preliminary separation of the CFCs, or a separation of the
products, is required. Aluminosilicate zeolites and related molecular sieves, which are used
extensively in hydrocarbon separation processes, offer a range of potential advantages over other
media for such separations. The work will examine the behavior of a number of common
halocarbons in a wide range of siliceous and aluminosilicate zeolite materials. Our research will
span studies of adsorption selectivity, the structure and dynamics of carefully selected host-guest
complexes, and computer modeling of these systems.
Carnegie Institute of Washington
Washington, DC 20015-1305
Geophysical Laboratory
High-Pressure Synchrotron Infrared Spectroscopy: An Integrated and Dedicated Facility st the
NSLS
| Investigator(s) |
Hemley, R.J.
|
$67,925 (Operating)
$205,637
(Equipment) |
| Phone | 202-686-2410 ext.2465 |
| E-mail |
hemley@gl.ciw.edu |
A synchrotron facility dedicated to high-pressure infrared spectroscopy and micro-infrared
spectroscopy is proposed. The facility will consist of a versatile and dedicated high-pressure beam
line capable of a broad range of measurements from the far-infrared to the visible spectrum at the
U10 beam line of the National Synchrotron Light Source (NSLS). This new facility will give
significantly higher IR brightness, particularly at long wavelengths, in comparison to the existing,
partially dedicated beam line (U2B). The addition of the dedicated beam line will allow a wide
range of microspectroscopic studies at high (and ambient) pressure. A new FT-IR will be installed
at the beam line along with a recently completed high-pressure (long working distance)
microscope. Existing instrumentation at U2B will be upgraded with a commercial,
high-magnification infrared microscope for micro-infrared measurements of 1-bar and
low-pressure samples. With the existing high-pressure x-ray facility at the NSLS, the new
instrumentation will permit synchrotron IR, synchrotron x-ray, and optical experiments on the
same high-pressure samples. Systematic high-pressure measurements addressing a range of
problems in condensed-matter physics and chemistry, earth and planetary science, and materials
science will be performed. These studies include high-pressure studies of dense hydrogen and
related planetary materials; minerals of the earth's crust, mantle, and core; geochemical reactions;
glasses and melts; surfaces and interfaces; whole-rock samples; and new high-pressure
technological materials.
University of Chicago
Chicago, IL 60637
Department of Biochemistry and Molecular Biology
Development of a Fast X-ray Shutter
Experiments which exploit the time structure of synchrotron radiation from the high brilliance
Advanced Photon Source (APS) storage ring facility offer exciting new research opportunities in
many areas of science. The spectral brilliance expected for a single pulse of x-rays emitted by an
insertion device is sufficient to permit probing time domains in dynamic processes in a range of
systems previously not accessible at second generation synchrotron facilities. Examples include
x-ray scattering and spectroscopic techniques with nanosecond time resolution. However, in order
to reach this time scale, a fast x-ray shutter mechanism capable of separating a single x-ray pulse
from the pulse train originating from the circulating particle bunches in the storage ring is
necessary. This selection is required since no x-ray detector presently available or planned is
capable of readout times comparable to inter-bunch times. We propose to develop such a fast
mechanical shutter system which will be capable of predictably isolating a single pulse of x-rays
when the APS operates under normal storage ring conditions (18 equally spaced bunches
separated by 204 nsec). The shutter will eliminate the need for single bunch operation which limits
the total current in single bunch operation to 5 to 10% of the design current and limits the
efficient use of the facility in single bunch mode. Partial funding of the shutter is provided by an
existing grant from the National Institutes of Health for construction of the BioCARS Sector 14
beamlines at the APS.
Colorado School of Mines
Golden, CO 80401
Department of Chemical Engineering
A Mechanistic Study of Molecular Sieving Inorganic Membranes for Gas Separation
| Investigator(s) |
Way, J.D.
|
$89,000 |
| Phone | 303-273-3519 |
| E-mail |
dway@mines.edu |
The objectives of this research are to investigate selective transport mechanisms in microporous,
silica membranes and to examine the effects of membrane microstructure and surface chemistry on
separation performance. A further objective is to use theoretical chemistry to simulate the
adsorption and transport of penetrants in pores of molecular dimensions. In the past year we have
investigated how both molecular size and adsorption influence the separation of hydrocarbons
such as acetylene, ethene, ethane, and propane. Mixed gas ethene/ethane separation factors (ratio
of permeabilities) measured at 20 bar feed pressure at temperatures up to 500 K were much larger
than the pure gas values and ranged from 0.8 to 6.2. A local maximum was observed at higher
temperatures. We were unable to measure the permeance (pressure normalized flux) of propane.
However, the presence of ethane and propane reduced the permeance of other gases considerably,
with up to a 44% decrease in CO2 permeance from a 2% propane 98%
CO2 feed mixture. The fouling was shown to be reversible by desorption of the
adsorbed hydrocarbons at lower pressures. FTIR studies and quantum simulations are in progress
to determine the chemical nature of the adsorption site on the silica surface.
Colorado State University
Fort Collins, CO 80523
Department of Chemistry
A Multinuclear Magnetic Resonance Study of the Interactions of Pollutants with Major Soil
Components
This project will provide detailed information on the fundamental chemical-physical behavior
(including chemical transformations) of certain organic contaminants with major soil constituents;
specifically clays and humic materials. Chemical interactions and physical behavior will be studied
via state-of-the-art nuclear magnetic resonance (NMR) experiments on solid and aqueous-solution
samples. The specific tasks of this project are (1) to generate, or update and refine, the
chemical-structural and NMR data bases of the specific clays and humics chosen for study; (2)
elucidation of the behaviors of individual pollutants with these specific humics and clays; (3) study
of the fundamental interactions in clay-humic "complexes"; (4) elucidation of
pollutant mobility and diffusion in the specific humic and clay systems; (5) chemical structural
characterization of ternary systems (pollutant-humic-clay); and (6) exploratory studies of
pollutant/whole-soil systems. Results of this kind of study are needed in the long term for
development of reliable and versatile soil-groundwater models of pollution. First-year activity
included choosing, isolating/purifying and characterizing organic soil components (humic acid,
fulvic acid, humin) and clays to be used as long-term stocks for most of the pollutant/soil and
pollutant/soil-component experiments of this three-year project, and probably subsequently. The
13C NMR spectrum of the raw soil, prior to any chemical treatment, was found to
be surprisingly well defined in terms of a variety of peaks from contributing chemical structures
and functionalities (probably because of low soil iron content). The organic samples isolated seem
ideal for exploring the interactions of various pollutant species with a variety of organic-chemical
functionalities. One of the most pervasive types of results that we have obtained in the first-year
effort on this project is the almost universal absence of chemical transformations of any organic
pollutants adsorbed on (in) soil components. While specific pollutant-substrate interactions can be
established for certain organics, these interactions do not appear to lead to chemical
transformations on a time scale of months (exception: acetone on a clay). This tentative result
may have substantial significance for relying on the impact of microrganisms for converting toxic
organics into less harmful species in soils. Very promising preliminary results have been obtained
via 2H wideline patterns of deuterium-labeled acetone, ethylene glycol and
benzene adsorbed on whole soil, humic acid and Ca-montmorillonite. The lineshapes show
evidence of both mobile and immobilized species. The lineshapes are being analyzed in terms of
motional models and in terms of correlations between pollutants adsorbed on whole soils and
pollutants adsorbed on soil components.
University of Delaware
Newark, DE 19716
Department of Chemistry and Biochemistry
Linear and Nonlinear Spectroscopic Probing of Solute Interactions with Chemically Modified
Silica Surface
| Investigator(s) |
Wirth, M.J.
|
$85,000 |
| Phone | 302-831-6771 |
| E-mail |
mwirth@udel.edu |
This research project investigates physically how charged species interact with chromatographic
surfaces. The results will benefit efforts to remove heavy metal ions from water, analyze complex
environmental samples, and characterize biopolymers for evaluating human health effects of
radiation. The work specifically focuses on the implementation and characterization of ultrathin
polymer films on silica. 1) Monolayers of polyethylenimine covalently attached to polysiloxanes
promise to combine a high capacity for metal ions with the high hydrolytic stability required for
large-volume pumping of contaminated water. 2) Ultrathin films of polymethacylate cross-linked
to a self-assembled monolayer promise to eliminate electrostatic interactions between cations and
silica, which enables more sensitive capillary electrophoresis of trace metal ions as well as
biopolymers. The study of cationic interactions with each of these surfaces is being conducted
using fluorescence spectroscopy and chemical force microscopy to study electrostatic
interactions, solid-state NMR, ellipsometry and atomic force microscopy to characterize the
polymer films, and near-field optical microscopy to probe topography and cation adsorptivity
simultaneously.
Duke University
Durham, NC 27708
Department of Chemistry
Fluorescence Lifetime in Chemical Analysis: The Next Generation
The two directions in this research are linked by the common thread of new multiharmonic fourier
transform (MHF) technology for frequency domain fluorescence lifetime measurements. In the
new technique of Total Lifetime Distribution Analysis (TLDA), the commercial MHF instrument
provides rapid acquisition of "total" lifetime information over a broad spectral
window, thereby replacing spectral resolution with lifetime resolution for fluorescence
characterization and fingerprinting applications. Sensitivity benefits from inclusion of the majority
of the total emission signal in the lifetime measurement. Data analysis using the self-modeling
maximum entropy method (MEM) provides a complete lifetime distribution that is free from bias
of an assumed decay model. Much of our attention is focused on detailed exploration of the
strengths and limitations of the MEM approach. Strategies for improving the performance of
MEM, in order to increase the accuracy and resolution of frequency domain lifetime analysis, are
under investigation. The introduction of the MHF as a rapid, on-the-fly detector of fluorescence
lifetime in capillary electrophoresis will increase the accuracy and sensitivity of laser excited
fluorescence detection, providing universal applicability through the use of direct and indirect
detection schemes without compromising the speed or resolution that make CE such a valuable
technique. Current investigations emphasize the initial modification of a commercial CE system
for MHF lifetime detection and optimization of S/N in the lifetime measurement.
University of Florida
Gainesville, FL 32611
Department of Chemistry
The Glow Discharge as an Atomization and Ionization Source
This research project focuses on fundamental and applied studies of the glow discharge as an
analytical source for trace elemental analysis of solid samples by atomic spectroscopy, with
primary emphasis on atomic emission and mass spectrometry. We are interested in both
conducting and nonconducting sample materials, using dc and rf discharges respectively. A major
change in instrumentation focus now finds our efforts directed to very fast pulsed discharges
coupled to a time-of-flight (TOF) mass analyzer. The TOF is already in operation, although still
undergoing fine tuning and refinement. For conducting materials, a microsecond regime pulsed
glow discharge permits relatively high power, although low average power. The more intense
conditions existing in the pulsed glow discharge plasma provide analytical advantages for both
atomic emission and mass spectrometry. In addition, the pulsed discharge allows for temporal
resolution to reduce or eliminate certain types of spectral background problems. Optimum
utilization of time-resolved methods arises from the combination of a TOF mass analyzer with the
pulsed discharge. A pulsed rf discharge in the millisecond range is also providing encouraging
results for nonconductor materials. We plan to study thin film samples, as well as bulk materials,
to determine the full capability of the pulsed discharge.
University of Florida
Gainesville, FL 32611
Department of Chemistry
Development of Laser-Excited Atomic Fluorescence and Ionization Spectrometric
Methods
The emphasis in this research is upon the development of new, sensitive, selective spectroscopic
methods for trace elemental analysis. Several projects are ongoing that involve ionization,
emission, and fluorescence in flames and glow discharges. Laser enhanced ionization (LEI) in a
microflame is being studied with two means of sample introduction: ultrasonic nebulization, which
will permit a thorough optimization of burner design and flame gas composition, and laser
ablation, which will provide the capability of analyzing single small particles and for elemental
mapping of surface and depth profiles. LEI is also being studied as a high resolution spatial
spectroscopic probe for flame temperatures (via detection of OH fluorescence) and for the in situ
detection of N2 via measurement of Raman scattering. Glow discharge atomic
reservoirs are also being studied using both emission spectrometry with a microcavity hollow
cathode discharge and laser excited atomic fluorescence for a micro-planar discharge. Both of
these glow discharge systems accept small volume discrete samples. The emission system has
multielement capability on subsample volumes, and the fluorescence system has the potential to
approach single atom detection in a real sample.
George Washington University, The
Washington, DC 20052
Department of Chemistry
New High-Temperature Plasmas and Sample Introduction Systems for Analytical Atomic
Emission and Mass Spectrometry
This research follows a multifaceted approach, from theory to practice, to the investigation and
development of novel helium plasmas, sample introduction systems, and diagnostic techniques for
atomic spectrometry and mass spectrometry. Four major sets of research programs are being
conducted that each include a number of discrete but complementary projects. The first program
is concerned with investigation of atmospheric-pressure helium inductively coupled plasmas (He
ICPs) that are suitable for atomization and ionization of elements, especially those possessing high
ionization energies, for the purpose of enhancing the detecting powers for a number of elements.
The second program includes simulation and computer modeling of He ICPs. The aim is to ease
the hunt for new helium plasmas by predicting their structure and fundamental and analytical
properties, without incurring the enormous cost for extensive experimental studies. The third
program involves spectroscopic imaging and diagnostic studies of plasma discharges to instantly
visualize their prevailing structures, to quantify key fundamental properties, and to verify
predictions by mathematical models. The fourth program entails development and characterization
of new, low-cost, low-sample consumption nebulization devices. These efforts collectively offer
promise of solving singularly difficult analytical problems that either exist now or are likely to
arise in the future in the various fields of energy generation, environmental pollution, biomedicine,
and nutrition.
Hampton University
Hampton, VA 23668
Department of Chemistry
Use of Ion Chromatography--dc Plasma Atomic Emission Spectroscopy for the Speciation of
Trace Metals
The research has focused on studies of the solution chemistry and speciation of trace metals using
chromatographic coupled with spectroscopic techniques. A new thrust in this work is directed
towards incorporating solid phase extraction in metal speciation. Application of solid phase
extraction in analytical measurements has several advantages, namely: isolation of the analyte
from complex sample matrix; sample preconcentration which, for dilute samples, leads to
improvement in measurement sensitivity; and the possibility of some separation of the chemical
species present. The study is looking at several types of sorbent; including bonded reversed phase,
bonded normal phase, naturally occurring polymers, and selected minerals. These materials are
being investigated, developed, and characterized for the extraction of neutral, charged, and
hydrated metal species in solution. The extraction mechanisms involved in each case will be
elucidated. Attempts will also be made to modify sorbent functionality by derivatization, thereby
placing on the adsorption site desired functionalities to achieve selectivity in the extraction and
speciation process. Analytical separation of the extracted metal species will be achieved by
coupling the extraction tube with an appropriate analytical column.
University of Illinois at Urbana-Champaign
Urbana, IL 61801
School of Chemical Sciences
Molecular Aspects of Transport in Thin Films of Controlled Architecture
Localized vibrational spectroscopy is being coupled with measurements of plasmon surface
polaritons (PSPs) in Ag- or Au-supported ultrathin (d
35nm) organized molecular assemblies exposed to
organic penetrants, with a special emphasis on understanding the role of film defects on
macroscopic properties. Because defects likely control a wide variety of technically important
properties of the films, understanding their structure, dynamics, and how they mediate transport in
the assembly is critical. Measurements of shifts in PSP resonances are exquisitely sensitive,
ultimately permitting changes in film thickness as small as 
d0.01 nm to be detected. These measurements allow us to build a detailed
picture of the changes in the dielectric function of the molecular assembly as it interacts with the
penetrant. Vibrational spectroscopy is used to probe the changes in molecular motions and
relaxation which occur after penetrant interaction, and the PSP measurements give detailed
information about the spatial distribution of penetrant molecules in the film. Using these coupled
experiments, we are building a detailed picture of the nature of defects in these molecular
assemblies.
Kansas State University
Manhattan, KS 66506
Department of Chemistry
Multidimensional Hadamard Transform Spectrometry: A New Analytical Technique
| Investigator(s) |
Hammaker, R.M.; Fateley, W.G.
|
$19,078 |
| Phone | 913-532-1454 |
Multidimensional spectrometry is defined in terms of three spatial dimensions (xi,
yi, zi) and one spectral dimension (wavelength, 
j or frequency,
vj). The xi and yi or surface coordinates are
accessed via a stationary two-dimensional (2-D) Hadamard encoding mask and the
zi or depth coordinate arises from using a photoacoustic detection system for
depth profiling by optical modulation and phase-sensitive detection. Measurements utilizing
two-dimensional and three-dimensional spectrometry are in print. Results for this program's first
images and spectra from four-dimensional spectrometry are in press. Present efforts are focused
on enhancement of capabilities for performing various multidimensional spectrometries. A
multiwavelength acoustic-optic tunable filter (AOTF) for the spectral dimension is in its final
testing. A new moving 2-D Hadamard encoding mask as a potential replacement for the stationary
2-D Hadamard encoding mask for the two surface dimensions has been obtained and is now being
evaluated. Decoding the multiwavelength AOTF results by Hadamard methods gives a multiplex
advantage in the spectral dimension. Using the multiwavelength AOTF without decoding will
provide a multiplication advantage in images without spectral separation. The moving mask with
completely open windows will allow access to any spectral region where appropriate sources,
spectral separators, and detectors are available.
Lehigh University
Bethlehem, PA 18015
Department of Chemistry
Perforated Monolayers
| Investigator(s) |
Regen, S.L.
|
$86,000 |
| Phone | 610-758-4842 |
| E-mail |
slr0@lehigh.edu |
This program is aimed at preparing new classes of synthetic membranes that can be used to
separate small molecules on the basis of their size, shape, and polarity. The general approach that
is being taken is to fabricate composite membranes from "perforated monolayers"
(i.e., monolayers that are assembled from "porous surfactants") plus highly permeable
substrates such as cast films of poly[1-(trimethylsilyl)-1-propyne] (PTMSP). Research that has
been carried out to date has led to the synthesis and characterization of a homologous series of
calix[n]arene-based surfactants that differ in their internal diameter. Current efforts are now
focusing on (i) the fabrication of composite membranes from such amphiphiles by use of
Langmuir-Blodgett (LB),and self-assembly methods and (ii) the characterization of their barrier
properties toward He and N2.
Louisiana State University
Baton Rouge, LA 70803
Department of Chemistry
Novel Micellar and Calixarene Derivatives for Selective Luminescence Measurements
Our research for this funding period has focused on continued studies of calixarenes as host
molecules for analytical measurements. We continue to explore these molecules for their
guest:host properties as related to analytical measurements. Our studies have also focused on the
ternary complexes of these calixarenes. One goal of this component of our research is to examine
the similarity of the calixarenes to the cyclodextrins in terms of their binding properties. In
addition to solution studies, we propose to use the calixarenes for selective separations in the area
of capillary electrophoresis. In regard to these latter studies, we have recently synthesized several
novel chiral calixarenes by use of a novel synthetic scheme developed in our laboratory. Some of
these calixarenes have been used as pseudophases in capillary electrophoresis to achieve selective
chiral separations. Even more selective chiral separations are achieved when these chiral
pseudophases are used in combination with achiral micellar media.
Michigan State University
East Lansing, MI 48824
Department of Chemistry
Direct Examination of Separation Processes in Chromatography by Laser-Induced
Fluorescence
Much of the present knowledge of chromatographic separation processes has been obtained from
experimental data and theoretical models that reflect the macroscopic behavior of solute zones.
Because the separation ultimately arises through the migration and interaction of individual
molecules, however, a more detailed understanding is necessary to guide future improvements in
chromatographic performance. This research program is concerned with two technological
advances that enable this challenge to be addressed from a unique and promising new perspective.
First, a novel detection system has been developed in our laboratory that allows the examination
of separation processes in situ as the solute traverses the chromatographic column. This system
employs laser-induced fluorescence detectors to measure the solute zone profile at several distinct
points along an optically transparent column. By effectively isolating the regions of interest, this
system enables an accurate measure of kinetic, thermodynamic, and hydrodynamic processes that
was not previously possible. Second, a three-dimensional stochastic computer simulation has been
developed and validated which provides a more detailed understanding of mass transport
processes in chromatographic separations. In this simulation, the migration of individual
molecules is established through diffusion and convection within a fluid phase that is in contact
with a surface. Molecular interaction and, hence, retention may arise by partitioning into
permeable surfaces or by adsorption at solid surfaces. The molecular distribution and the
corresponding zone profile may be examined and characterized by means of statistical moments at
any specified time or spatial position during the simulation. This simulation provides the
opportunity to perform hypothetical experiments and to make observations that may not be
possible in a real chromatographic system. During the present grant period, these advances in
experiment and theory have been used to characterize the kinetics of solute distribution between
the fluid and surface phases. The experimental studies were performed using octadecylsilica, the
most common stationary phase for liquid chromatography. The rate constants for a homologous
series of model solutes were determined as a function of temperature in the range from 10 to 70
°C, pressure in the range from 400 to 4463 psi, and mobile-phase composition. The
experimental rate constants correlate well with values predicted by the stochastic computer
simulation for a partition mechanism under diffusion-limited conditions. From these results, it is
apparent that kinetic processes are a significant contribution to zone broadening and must be
minimized in order to improve chromatographic performance.
University of Missouri at Rolla
Rolla, MO 65401
Department of Chemistry
A New Class of Macrocyclic Chiral Selectors for Stereochemical Analysis
| Investigator(s) |
Armstrong, D.W.
|
$78,000 |
| Phone | 573-341-4429 |
| E-mail |
mrichard@umr.edu |
Halocarbons are usually separated using gas-liquid chromatography (GLC) using relatively long
columns. Most of the more volatile chlorofluorocarbons can be better resolved by gas-solid
chromatography (GSC), however, some of these compounds react with highly active stationary
phases. Particularly reactive are the replacement chlorofluorocarbons that are not fully
halogenated or fluorine substituted. A new, less-active GSC stationary phase was found to be
sufficiently inert to effectively separate the lower molecular weight chlorofluorocarbons in
addition to the large more polar halocarbons. These GSC columns also were used for analyses of
the halocarbon content of refrigerator insulation. It was found that percent levels of specific
halocarbons remained in the insulation decades after it was manufactured. Consequently, the
destruction and disposal of old refrigerators could release significant quantities of halocarbons to
the atmosphere. Commercial halocarbon preparations were sometimes found to contain significant
quantities of other halocarbon impurities. Among the more prevalent chiral monoterpenoid
compounds in conifers are 
-pinene,
-pinene, and smaller amounts of
camphene and limonene. The most prevalent chiral monoterpenoid compounds in fossilized resin
(referred to as amber in this paper) appear to be borneol, isoborneol, and camphene. Most of
these compounds have easily measured enantiomeric excesses. The borneol and isoborneol in
some amber samples have pronounced enantiomeric excesses despite the fact that they are tens of
millions of years old. The enantiomeric ratios of the monoterpenoids in different ambers vary
tremendously and often are distinct. However, in any single amber sample, the stereochemistry
(absolute configuration) of the excess monoterpenoid enantiomers appears to be identical. The
camphene in amber may be a secondary reaction product formed over time, possibly from the
dehydration of borneol. Although a compound's original stereochemistry can be preserved, it also
may diminish with the number and type of chemical transformations over geological time. The
monoterpene enantiomeric ratios in modern conifer resins vary tremendously. Future
stereochemical studies are outlined that could provide the data necessary for more exact
geochemical interpretations and possibly for obtaining pertinent paleobiological information.
University of North Carolina at Chapel Hill
Chapel Hill, NC 27599
Department of Chemistry
Solid-State Voltammetry and Sensors in Gases and Other Nonionic Media
This project is based on using microelectrode voltammetry for design and application of
quantitative electrochemical transport and kinetics experiments to semi-solid and solid redox
phases. The experiments include transport and electron transfer reactions of electron
donor/acceptor solutes and surfaces in polymeric solvents and liquid crystalline phases. The goals
of this project include (i) developing the necessary miniaturized electrode methodologies, cells,
and requisite theory for quantitative voltammetry in rigid media, (ii) exploring important
characteristics of homogeneous and heterogeneous electron transfer reaction dynamics in rigid
environments, in particular how the dynamics of "outer sphere" redox couples
respond to rigidification of their surroundings, (iii) exploring polymer-phase transport, including
polymer-in-polymer diffusion of redox-labelled poly-ethers, anisotropic transport in liquid
crystalline phases and polymers, and coupling between slow diffusion and homogeneous electron
transfers, and (iv) learning to dynamically manipulate diffusion rates of redox sites within polymer
electrolytes so as to fashion ultrathin, electrically conducting mixed valent layers by freezing the
concentration gradients that are electrolytically generated at electrodes. We have recently
succeeded in fashioning an example of a frozen gradient system from a poly-ether-derivatized
viologen.
Princeton University
Princeton, NJ 08544
Physics Department
Pixel Array Detector for Time-Resolved X-ray Science
Our goal is to develop, test, and install a silicon-based Pixel Array Detector (PAD) for x-ray
applications at synchrotron radiation sources. At present, there are no existing detectors capable
of recording successive x-ray images at the megahertz rates made possible by sources such as the
Advanced Photon Source. The PAD is designed to fill this need and is intended for time-resolved
applications such as Laue crystallography, destructive analysis, materials failure, phase transition
studies, etc. The PAD consists of a two-dimensional array of radiation sensitive pixels fabricated on
a silicon wafer. Each pixel is connected to its own electronics cell, consisting of
signal-conditioning and storage electronics. All pixels operate in parallel to integrate the incident
signal in a way which allows very high count-rates.
Purdue University
W. Lafayette, IN 47907-1283
School of Chemical Engineering
Fundamentals of Electric Field-Enhanced Multiphase Separations
The research is motivated by recent scientific and practical evidence that the use of electric fields
offers a powerful means for enhancing the efficiency of and reducing waste generation in various
unit operations that are used in the separation and purification of chemicals. Unfortunately,
existing theoretical and experimental foundations of the effects of electric fields in multiphase
separations are weak. The electric field-induced enhancement of the performance of separations
processes dealing with fluid mixtures can be attributed to a variety of interactions between applied
fields and the fluids and/or interfaces separating the fluid phases in multiphase systems. A central
issue in electro-separations is the dispersion of one phase into another phase, which simply entails
the creation of drops of the first phase in an otherwise continuous second phase, and is the subject
of this research program. Particular attention will be paid in the present research to the
development of a fundamental understanding of the factors that control the creation of satellite
droplets during drop formation and a distribution of drop sizes during atomization. The latter
phenomena can signal the death of practical processes not only in separations but in applications
ranging from the synthesis of ceramic precursor powders to ink-jet printing. The goals of the
research will be accomplished through an approach that places equal emphasis on theory and
experiment. Theoretical and computational analyses will utilize large-scale computations with
finite element, boundary element, and volume of fluid methods. The experiments will rely on
visualization of sub-millisecond events such as the rupturing of fluid interfaces using ultra
high-speed video photography at rates up to 40,000 frames per second and quantitative
measurement of drop sizes and velocities using Phase Doppler Anemometry/Velocimetry.
Purdue University
West Lafayette, IN 47907
Department of Chemistry
Ion Trap Mass Spectrometry: Ion Motion, Reactions, and Applications
Fundamental understanding of ion motion in the quadrupole ion trap is being sought by (i) unique
electrode configurations including moveable endcaps and a split ring and (ii) novel methods of
manipulating ions, including phase-locked resonant excitation, dc pulse activation, parametric
oscillation, and stored waveform methods of ion ejection. Simulations of the motion of ensembles
of ions, which include collision effects and ion-ion interactions, are being refined through
extension of our ITSIM program. Three-dimensional visualization of simulated trajectories are
used to assist in elucidating the behavior of trapped ions and allowing for predictions to be made
for procedures which minimize ion-ion interactions. Experiment and simulation are being applied:
(i) to evaluate capabilities of measuring ion polarizability, (ii) to study electrical cooling using
external quadrupolar DC pulses, (iii) to characterize mass shifts due to coulombic ion-ion
interactions, (iv) to study the differences in ion mobility of ions arising from different collisional
cross sections, (v) to characterize new methods of mass analysis including the use of quadrupolar
dc ejection during activation. Fourier transforms of the induced image currents are being used
to perform broad-band non-destructive ion detection. The thermochemical properties of
tricyclo[3.3.3.0]undec-3(7)-ene, a pyramidalized alkene and typical chemical system of interest,
are being determined by cluster ion dissociation.
Purdue University
West Lafayette, IN 47907
Department of Chemistry
Reactions of Gaseous Metal Ions/Their Clusters in the Gas Phase Using Laser Ionization:
Fourier Transform Mass Spectrometry
The research group continues to use Fourier transform ion cyclotron resonance (FTICR) mass
spectrometry to study the chemistry and photochemistry of metal-containing ions in the gas phase.
Some areas of current interest are summarized here: (1) Infrared multiphoton dissociation studies
on transition metal containing ions of the form
MCnH2n+ (M = Fe, Co, Ni; n = 2-5), as well as
MC4H6+ and
M(C2H4)(C2H2)+ isomers for M = Fe, Co, Ni are underway. Of particular interest are the observation of multiple
products and the application of competitive dissociation for determining relative bond energies.
(2) Detailed studies on Nbn+ (n = 2-15) clusters with
CnH2n (n = 2-4) are underway providing detailed information on
size, structure and reactivity relationships. Complete dehydrogenation of alkenes also connects
with our interest in studying metallo-carbohedrenes (met-cars) and related metal-carbon clusters.
(3) Sequential reactions of metal clusters with CH3I to generate
MnIx+ are being probed as a means of
characterizing the number of non-metal-metal bonded electrons, and the consequence of
electronic structure on subsequent reactivity. (4) With the help of Professor Sabre Kais at Purdue,
we have begun a vigorous ab initio program focusing on metal-containing ions. Currently we are
calculating Fe(CH2S)+ and
Fe(CH2O)+ structures to explain the interesting differences in
their chemistry we observe. We have also begun to study Nbn+ to
try to support the conclusions drawn on electronic structure obtained from the
CH3I reactions.
Rensselaer Polytechnic Institute
Troy, NY 12180
Department of Chemical Engineering
Chemical Interactions between Protein Molecules and Polymer Membrane Materials
| Investigator(s) |
Belfort, G.; Koehler, J.A.; Ulbricht, M.
|
$92,000 |
| Phone | 518-276-6948 |
| E-mail |
belfog@rpi.edu |
These results represent the first measurements of intermolecular forces between adsorbed proteins
and hydrophobic polymeric films. The intermolecular forces, including the adhesion forces
between a model protein, hen egg lysozyme (Lz), and itself and a polymeric film made from
poly(bisphenol-A-arylsulfone) (PSU) and deposited on molecularly smooth mica, were measured
above, at and below the pI (10.8) of Lz. Buffer and Lz solutions similar to those used in the force
measurements were filtered through commercial PSU ultrafiltration (UF) membranes in order to
obtain measures of fouling and cleanability. Lz-Lz and Lz-PSU adhesion forces correlate inversely
with fouling, cleanability and protein transport. This suggests that intermolecular forces between
Lz-PSU, although important initially, play a lesser role once the membrane surface is fully covered
with adsorbed protein, while those between Lz-Lz dominate long term filtration behavior. As with
most studies with proteins and membranes, it is difficult to extrapolate these results to other
proteins and membrane materials. We have also made progress with respect to the development of
flexible and inexpensive techniques for modifying the surfaces of commercial membranes. As a
complementary approach to the photochemical (ultraviolet radiation) method, we have
investigated, as part of this project, the surface modification of polyacrylonitrile (PAN) and PSU
by low temperature plasma. During the period of this grant, four publications have appeared in the
literature and one publication is completed and will be submitted shortly while the last manuscript
is in preparation. They are: a) Pincet, F., Perez, E. and Belfort, G., "Do Denatured Proteins
Behave like Polymers?" Macromolecules 1994, 27(12), 3424-3425, b) Pincet, F., Perez, E. and Belfort,
G., "Molecular Interactions Between Proteins and Synthetic Polymer Films," Langmuir 1995, 11
(4), 1229-1235, c) Ulbricht, M. and Belfort, G., "Low Temperature Surface Modifications
of Polyacrlonitrile Ultrafiltration Membranes - 1. Plasma Treatment Effects," J. Appl. Polymer Sci.
1995, 56, 325-343, d) Ulbricht, M. and Georges, B., "Surface Modification of Ultrafiltration
Membrane by Low Temperature Plasma. II. Graft Polymerization onto Polyacrylonitrile and
Polysulfone," J. Membrane Sci. 1996, 111, 193-215, e) Koehler, J.A., Ulbricht, M. and Belfort, G.,
"Intermolecular Forces Between Proteins and Polymer Films with Relevance to Filtration," in
preparation, and f) Nabe, A., Staude, E. and Belfort, G., "Effects of Surface Modification of
Polysulfone Ultrafiltration Membranes on Fouling by BSA Solutions," in preparation.
Rutgers, The State University of New Jersey
Piscataway, NJ 08855-0849
Department of Physics and Astronomy
High Resolution Upgrade for Core-Level Photoemission Spectroscopy
We are upgrading the present high resolution core-level photoemission beamline U4A at the
National Synchrotron Light Source (NSLS), so that it will have higher resolution (~15-30 meV)
over a broader spectral range (10-200 eV) than is currently available at any other photoemission
beamline at NSLS. This will result in a beamline performance that is state-of-the-art for core-level
photoemission. The present Toroidal Grating Monochromator (TGM) design with point to point
focusing at three separate beamline positions will be replaced by a Spherical Grating
Monochromator (SGM) design with only source to sample point focusing. These will improve
both the resolution and the brightness at the sample so that photoemission microscopy in addition
to high resolution core-level spectroscopy will be possible. Such an upgraded beamline should
prove to be extremely useful in new studies of bimetallic systems and semiconductor interfaces.
This upgrade will complement the other new beamlines at NSLS that are mainly at higher photon
energy (100-1000 eV).
Stanford University
Stanford, CA 94305-2115
Department of Geological and Environmental Sciences
Detectors and Other Instrumentation for Research in Environmental Chemistry and
Heterogeneous Catalysis at the Stanford Synchrotron Radiation Laboratory
| Investigator(s) |
Brown, G.E., Jr.; Hedman, B.; Hodgson, K.O.; Kendelewicz, T.; Leckie, J.O.; Madix, R.J.; Parks,
G.A.; Pianetta, P.; Solomon,
|
$404,000 (Equipment) |
| Phone | 415-723-9168 |
| E-mail |
gordon@Pangea.stanford.edu |
The main objective of this project is to purchase two state-of-the-art X-ray detectors and
associated instrumentation for use in synchrotron-based environmental chemistry and
heterogeneous catalysis research at the Stanford Synchrotron Radiation Laboratory (SSRL).
During the next year, we will test and purchase a 30-element Ge array detector with fast
throughput JFET-based electronics for use in X-ray Absorption Fine Structure (XAFS)
spectroscopy studies of the products of chemical interactions of metal and metal-ion adsorbates at
less than monolayer coverages on oxide surfaces and at oxide-water interfaces in simplified model
systems. Such reactions play a major role in determining the transport properties, toxicity, and
ultimately the bioavailability of environmental contaminants such as toxic heavy metals and
radionuclides; they are also of critical importance in heterogeneous catalysis. However, the
pathways of these types of surface reactions are often poorly understood, particularly under
reactive conditions, which limits efforts to remediate environmental contaminants or attempts to
increase the efficiency of catalytic processes. We will also use XAFS spectroscopy and the new
hard X-ray detector to study the chemical speciation and transformation of heavy-metal
contaminants in more complex natural soils and in hyperaccumulating plants and organisms under
different environmental conditions. The information provided by these studies is critical for
developing robust and cost-effective strategies for chemical separations and remediation
technologies. Two of the main limitations on current XAFS studies of the speciaton of heavy
metal contaminants in environmental samples and of the nature of reactive metal sites on metal
oxide substrates of catalytic importance are lack of sufficient X-ray flux and of sensitive,
high-throughput detectors. The new hard X-ray detector, coupled with the new high-flux
molecular environmental science beam line at SSRL, will increase the sensitivity of our XAFS
studies by at least an order of magnitude. During the second year of this project, we plan to test
and purchase a vacuum-compatible 13-element detector system for use in soft-x-ray/vacuum
ultraviolet surface XAFS, photoemission, and x-ray standing wave studies of metal and metal-ion
adsorbates on clean oxide surfaces. These studies are intended to provide fundamental
information on the effects of adsorbates on the geometric and electronic structures of oxide
surfaces.
State University of New York at Buffalo
Buffalo, NY 14260
Department of Chemistry
Determination of Solvation Kinetics in Supercritical Fluids
This research program is directed toward several key aspects of supercritical fluid science and
technology. The goals/subprojects are as follows. (1) Understanding the effects of neat and
entrainer-modified supercritical fluids on solute-fluid dynamics. (2) Determining the effect of fluid
density on the disposition of energy between a dissolved solute and the fluid bath. (3) Probing the
effects of continuous phase density on the internal dynamics of reverse micelles formed in
supercritical carbon dioxide. (4) Quantifying the behavior of polymers subjected to supercritical
carbon dioxide in molten form and under infinite dilution conditions. (5) Quantification of
solute-solute synergism and the origin of such. (6) Investigation of local density and composition
surrounding a solute at an interface as such influences extraction and separation processes in
supercritical fluid science and technology. Modern ps (and now fs) in situ optical spectroscopy are
used in this work. To date this work has helped to better define and quantify how solvation occurs
in supercritical fluid systems and how one can tailor a supercritical fluid for a particular
"solvent" need. Overall, this work is providing a better molecular-level view of the
unique chemistry of supercritical fluids and how one can control reactions and solute
conformation by using a supercritical fluid.
State University of New York at Stony Brook
Stony Brook, NY 11794-3800
Physics Department
Enhancement of the Microscopy Facilities at the NSLS X1A
The project (expected to start in August 1996) is designed to open important new capabilities at
the microscopy stations on the NSLS soft X-ray undulator beamline X1A. Both the Scanning
Transmission X-ray Microscope, STXM, and the Scanning Photoemission Microscope, SPEM,
use zone plates to form microprobes for imaging with elemental and chemical specificity. STXM
is designed to study primarily biological and other organic specimens at 50 nm or better
resolution. SPEM is designed to study surfaces at 150 nm or better resolution. Both instruments
can take spectra from small specimen areas - absorption spectra on STXM, photoelectron spectra
on SPEM. STXM will be made vacuum compatible to extend XANES microscopy capabilities to
the nitrogen and oxygen edges, where even small amounts of residual air interfere with imaging
and spectroscopy. At the same time the computer and software system will be brought up-to-date.
The stage will be rebuilt using a new design for accurate linearity and orthogonality of the axes.
SPEM will also have its stage rebuilt to improve reliability and reproducibility. Its computer/data
acquisition/software system will be replaced with one that is compatible with STXM for improved
speed, flexibility, and economy. These upgrades will be performed with minimal down-time by
introducing new hardware and software during NSLS shutdown periods.
Syracuse University
Syracuse, NY 13244
Department of Chemical Engineering and Materials Science
Mechanisms of Gas Permeation through Polymer Membranes
The objective of this study is to investigate the mechanisms of gas transport in polymers by
molecular dynamics simulations. It is desired, in particular, to determine the effects of systematic
changes in polymer structure on the gas transport. Accordingly, diffusion coefficients of He,
O2, N2, CO2, and CH4 in
poly(dimethyl siloxane) (PDMS), poly(propyl methyl siloxane), poly(trifluoropropyl methyl
siloxane), and poly(phenyl methyl siloxane) were calculated for a temperature of 300 K. The
diffusion coefficients decrease with decreasing intrasegmental mobility of the polymer chains (i.e.,
with increasing bulkiness of side chains and increasing glass-transition temperature) as well as
with increasing "kinetic" diameter of the penetrant molecules. The calculated values
of the diffusion coefficients for all gas/polymer systems studied are consistent with experimental
values within the expected error limits. An analysis of the trajectories of the penetrant molecules
in the polymers revealed two types of motions: (1) "oscillating motions" inside
cavities in the polymer matrix, and (2) "jumps" from one polymer cavity to another
one. The lengths of the jumps are of the order of 8-10 Å, whereas the oscillating motions
are of the order of <5 Å. The diffusion of gases in polymers is controlled by the
fractional free-volume in the polymer, the free-volume distribution, and the dynamics of the
free-volume. Preliminary simulations indicate that the most highly gas-permeable polymer, namely
PDMS, has a larger mean free volume and a broader distribution of free-volume voids than the
other poly(organosiloxanes) studied. As a result, PDMS also has the lowest selectivity for
different diffusing gases. The above studies were concerned with the transport of light gases in
silicone polymers, which are in the "rubbery" state at the temperature assumed for the
molecular dynamics simulations (300 K). These studies have been extended to
"glassy" polymers, since such polymers are being widely used as membrane materials
for the separation of gases of industrial interest. Accordingly, values of diffusion and solubility
coefficients for He, O2, N2, and CH4 in glassy
poly(methyl methcrylate), PMMA, have been estimated for the temperature of 308 K (35°C), at
which experimental data for some of these gas/PMMA systems are available for comparison. The
computations were based on a "transition-state" model developed by U. Suter and his
coworkers at the Federal Swiss Institute of Technology, because the methodology used for
silicone polymers is too time-consuming when applied to the estimation of diffusion and solubility
coefficients of gases in glassy polymers. The estimated (computed) values of the diffusion
coefficients for O2, N2, and CH4 in PMMA
agree within a factor of 4 or better with the experimental values (extrapolated to zero gas
concentration in the polymer). The estimated value of the diffusion coefficient for
CO2 in PMMA is much lower than the experimental value; this is probably due to
the fact that the computations used the Lennard-Jones size parameters of the penetrant gas
molecules and did not take into account the shapes of the molecules. The estimated solubility
coefficients for O2, N2, CO2, and
CH4 are within a factor of 5 or better of the experimental values. No
experimental diffusion or solubility coefficients for He in PMMA are available for comparison. All
estimated values of the diffusion and solubility coefficients are averages for 5 different polymer
microstructures. Clearly, the computational techniques available at present for the estimation of
diffusion and solubility coefficients of gases in glassy polymers must be substantially improved.
The computed solubility isotherms (i.e., plots of the gas solubility versus equilibrium pressure) for
O2, N2, CO2, and CH4 in
PMMA exhibit the expected nonlinear "dual-mode sorption" behavior; the solubility
isotherm for He in PMMA is linear (i.e., obeys Henry's Law) due to the very low solubility of this
gas in the polymer. The computed mean-square displacement, <r2>, of the
penetrant gas molecules in the PMMA microstructure exhibits three different dynamics as a
function of time, t: at short times (t <1 ps) the penetrant molecules have only local mobility;
the molecules then exhibit an anomalous diffusion behavior, <r2>
proportional to tn, n <1; after a longer time the penetrant molecules show the
expected Einstein diffusion behavior, <r2> = 6 Dt, n = 1, where D is the
diffusion coefficient. For He, the Einstein behavior is observed at much shorter times
(10-9 s) than for the other gas molecules studied.
University of Tennessee at Knoxville
Knoxville, TN 37996
Department of Chemistry
Polymer-Based Separations: Synthesis and Application of Polymers for Ionic and Molecular
Recognition
Our research is focused on the synthesis of polymer-supported reagents for application to
selective metal ion separations and as highly efficient catalysts for organic reactions. In one
example, earlier research has shown that the covalent immobilization of a diphosphonate ligand
within a polymer support yields a polymeric reagent with very high affinities for radionuclides.
Current research has just been published which details a new synthesis of diphosphonate ligands
immobilized directly on to polystyrene. This synthesis widens the variety of methods that can be
applied to the preparation of a family of polymers bearing diphosphonate ligands, each member of
the family displaying different selectivities towards different metal ions. The source of these
differences is the microenvironmental effect wherein the polarity surrounding a given ligand is
modified through the presence of non-coordinating groups. This effect has also been found to
allow for the synthesis of efficient catalysts for application to the Mitsunobu, aldol and Prins
reactions.
University of Tennessee at Knoxville
Knoxville, TN 37996
Department of Chemistry
Study of the Homogeneity of the Packing Density of Chromatographic Columns and its
Effects on Column Performance
Chromatographic columns are not homogeneous but exhibit important radial fluctuations of their
packing density and of any property (porosity, permeability, efficiency, retention, saturation
capacity) which is related to this density. Several authors have shown that the local velocity is
typically 3-4% higher and the column efficiency 50-100% higher in the central core region than
close to the wall for analytical columns. We have recently obtained similar results for preparative
columns (2" i.d.). The lack of homogeneity of the column packings problem can be related
to the important change in their apparent density which accompanies the consolidation of beds of
particles. This phenomenon is well known in soil mechanics and in the manufacturing of
pharmaceutical tablets. Because of the friction of the bed against the column wall during the bed
consolidation, systematic radial fluctuations of the packing density take place. The aim of our
research is to understand the phenomena which take place during column packing, the mechanism
of bed consolidation and to improve the efficiency of columns.
University of Tennessee at Knoxville
Knoxville, TN 37996
Department of Chemistry
Fundamental and Instrumental Development of Capillary Electrokinetic Separation
Techniques for Energy Applications
This multifarious research program is dedicated to the development of capillary electrokinetic
separation techniques for energy related applications. Research is directed at (i) developing a
fundamental understanding of pertinent separation and band dispersion mechanisms and (ii)
developing and refining instrumentation and instrumental approaches for these techniques. (i) The
fundamental work focuses on studies involving highly ordered assemblies as running buffer
additives. These additives include macrocyclic compounds such as cyclodextrins (CDs) and
calixarenes, micelles, and soluble (entangled) polymers and are employed in electrophoretic (e.g.,
capillary electrophoresis, CE) and/or electrochromatographic (e.g., micellar electrokinetic capillary
chromatography, MECC, and capillary electrochromatography, CEC) modes of separation. In
some cases, reasonable correlations between molecular modeling-based CD-solute interaction
energies and retention behavior have been observed for mixtures of geometrical isomers and
optical isomers. A dual-CD phase (charged and neutral) form of capillary electrochromatography
(cyclodextrin distribution capillary electrochromatography, CDCE) has been demonstrated that
offers advantages over the more established MECC technique. Since the CDs used in the CDCE
technique effect solute retention independently, it is anticipated that molecular modeling
techniques will eventually lead to the computational development of "designer"
CDCE separation systems (simple-to-complex combinations of commercially available CDs) that
meet many separation challenges. A new class of macrocyclic phenolic compounds (calixarenes)
have also shown some promise as reagents for CE separations. The mechanisms by which DNA
restriction fragments migrate and disperse in size-selective CE separations employing entangled
polymers as running buffer additives are also being studied using novel instrumentation (see
below). (ii) Instrumental work includes efforts to extend the utility of laser induced fluorescence
(LIF) and spectrophotometric detection in CE. Examples include the use of on-column
complexation with Arsenazo III (for low ppb screening of uranyl) and with hydroxyquinolines (in
conjunction with the sensing of metals, see below). A novel instrumental configuration that
permits rapid and reproducible translation of the LIF detection zone along a CE capillary resulted
in improvements in both separation and detection performance and facilitated certain fundamental
studies. It should be possible to modify this instrumentation for field use. A prominent new area of
research involves the development of separation-based fiberoptic sensors (SBFOSs). The
introduction of CE methodologies into sensing provides a unique and powerful element of
selectivity for remote analyses. Prototype SBFOSs have been fabricated and demonstrated for
measurements of florescent dyes in a CE mode, metal ions in a CE mode with on-column
chelation, and fluorescent toxins in an electrochromatographic mode. Incremental improvements
in the design and function of the SBFOS are being implemented.
Texas A & M University
College Station, TX 77843
Department of Chemistry
Development of Laser-Ion Beam Photodissociation Methods
This research program focuses on numerous aspects of laser-mass spectrometry and fundamental
gas-phase ion chemistry. Photodissociation methods are being developed to probe dissociation
reactions of highly activated ionic systems. In addition, the potential analytical utility of laser-ion
photodissociation for structural characterization of complex molecules is being evaluated. A
tandem time-of-flight (tof/tof) photodissociation apparatus is now being used for a range of
tandem mass spectrometry experiments. The ions are formed by pulsed UV laser desorption
(matrix-assisted laser desorption ionization [MALDI]), and photodissociation of the
mass-selected ion is performed by using a high-power, pulsed eximer, Nd:YAG or
N2 laser. The primary objective of this research is to improve the sensitivity of
MS-MS experiments by 100 times (10 to 100 femtomole) and the mass resolution of MS-II by 5
to 10 times (1,000 to 10,000). The objective of the tof/tof experiment is to study the dissociation
reactions of very large (>m/z 5000) molecules. In addition, laser-ion beam photodissociation
methods are being used to examine ionic clusters that are important to matrix-assisted-UV-laser
desorption ionization of polar, thermally labile biomolecules. In particular, studies are conducted
on excited state H+-transfer reactions and the way in which such reactions
influence the dissociation chemistry of gas-phase ionic systems. These studies are performed on a
home-built tof apparatus. Clusters of matrix and analyte are formed by a pulsed supersonic nozzle
and the clusters are ionized by either 337 nm or 355 nm photoexcitation. The clusters can be
formed with or without solvent, e.g., CH3OH or NH3. These
studies are aimed at understanding both the mechanism of ion formation and the influence of
solvent on the ionization process.
Texas Tech University
Lubbock, TX 79409
Department of Chemistry and Biochemistry
Metal Ion Complexation by Proton-Ionizable Lariat Ethers and Their Polymers
| Investigator(s) |
Bartsch, R.A.
|
$95,000 |
| Phone | 806-742-3069 |
| E-mail |
frabc@ttu.edu |
Goals of this research project are the synthesis of new metal ion complexing agents and chelating
polymers and their applications in metal ion separation processes. Cyclic polyethers (crown
ethers) which possess pendent, proton-ionizable groups are novel agents for metal ion separations
by solvent extraction and liquid membrane transport processes. Movement of the metal ion from
the aqueous phase into the organic phase does not require concomitant transport of an aqueous
phase anion. This factor greatly increases metal ion extraction and transport efficiency for
proton-ionizable lariat ethers compared with those of crown ethers and non-ionizable lariat ethers
in separations involving metal chlorides, nitrates, and sulfates. New lariat ether carboxylic acids,
phosphonic acid monoethyl esters, phosphinic, sulfonic, and phosphonic acids and N-(R)sulfonyl
carboxamides are being synthesized and tested to probe the influence of structural variation within
the ligand upon the selectivity and efficiency in separations of alkali and alkaline earth metal ions.
Novel chelating polymers are being synthesized by condensation polymerization of
proton-ionizable dibenzocrown ether monomers. In addition to ion-exchange sites, these resins
provide crown ether units for metal ion recognition. Sorption behavior of these resins for a variety
of alkali metal, alkaline earth, and heavy metal cations is being assessed.
Texas Tech University
Lubbock, TX 79409
Department of Chemistry and Biochemistry
Separations on Water-Ice
Water-ice has many unusual properties some of which may be beneficial in separation problems.
This project seeks to explore the merits of water-ice as a separation medium. Lessons learned
from there would be used to investigate other related phases as separation media. Using finely
powdered ice and using partially polar eluents such as ethyl acetate - hexane, we have successfully
separated various test mixtures including plant extracts. However, pressure induced melting of ice
limits the ultimate separation efficiencies that can be attained in such systems.
Electrophoretic separations can also be carried out on planar ice surfaces. In that case extremely high fields can be
applied. Such separations are rapid but the difficulty of reproducing surfaces run-to-run limits
overall reproducibility. Present work centers on open silica networks produced within capillaries
by sol-gel approaches. Such structures are easily and inexpensively produced and appear to
permit very high separation efficiencies, especially when used in conjunction with capillary based
separation systems.
University of Texas at Austin
Austin, TX 78712
Department of Chemical Engineering
Carbon Dioxide Based Solvents for Waste Minimization
| Investigator(s) |
Johnston, K.P.
|
$382,000
(39 months) |
| Phone | 512-471-4617 |
| E-mail |
kpj@che.utexas.edu |
Our goal is to develop environmentally benign carbon dioxide-based solvent formulations to
replace toxic organic solvents for chemical processing. The use of CO2 could lead
to large reductions in organic wastes to soil, water and air. Waste minimization is vital to the
growth of the U.S. chemical industry. We propose to design surfactants to produce
CO2-based solvent formulations in the form of microemulsions, emulsions, and
latexes. CO2-based solvents offer exciting new opportunities in chemical
manufacturing involving heterogeneous reactions (including polymerization), solvent free
coatings, extraction of heavy metals including radioactive compounds from soils and wastewater,
polymer processing, and separations processes including cleaning and purification. Because a
CO2 phase has such different properties than either hydrophilic or lipophilic
phases, it may be considered to be a third type of condensed phase. An organic latex,
polymethylmethacrylate, has been synthesized in CO2 with a fluorocarbon
homopolymer stabilizer, demonstrating the ability to disperse an organic phase. Recently, in an
article in Science, we demonstrated that microemulsion droplets with "bulk-like"
water properties may be formed in CO2 with a relatively nontoxic ammonium
carboxylate perfluoroether surfactant. The ability to design surfactants for the interface between
organics and CO2, or water and CO2, and to understand the
mechanisms of stabilization of microemulsions, emulsions and latexes in CO2 are
the keys to advancement in this field. Water-in-CO2 emulsions would be
particularly desirable as solvents for waste minimization. Because the van der Waals forces are so
much weaker in CO2 than in typical oils, and because supercritical fluids are
highly compressible, totally new concepts will be required. Presently, the principles for designing
surfactants for CO2 are unknown.
University of Texas at Austin
Austin, TX 78712
Department of Chemical Engineering
Synthesis and Analysis of Novel Polymers with Potential for Providing Both High
Permselectivity and Permeability in Gas Separation Applications
Formation and testing of highly aromatic membrane materials with hindered intrasegmental
mobility and interchain packing are being pursued in this project. Such materials are good
candidates to provide entropically and energetically selective diffusion media for separation of
important gas pairs like oxygen and nitrogen. Currently, convenient solution-based processing of
polymers allows producing economical asymmetric membranes with thin (1000Å) selective
layers. Unfortunately, limitations limit the selectivity achievable with conveniently soluble
polymers. Analysis of the deficiencies of such membrane materials suggested an approach to
greatly improve their properties while maintaining compatibility with current commercial
formation equipment. Specifically, an additional reactive step is being investigated to achieve the
necessary rigidity for optimum membrane properties. This project seeks to continue to expand on
past experience in tailoring properties while beginning to explore secondary steps to achieve truly
superior separation properties. Thermal and chemical treatments to achieve this step are being
investigated currently, since they are most easily implemented.
University of Utah
Salt Lake City, UT 84112
Department of Chemistry
Spectroscopic Characterization of Intermediates in the Iron Catalyzed Activation of
Alkanes
Infrared and Raman techniques are being used in time-resolved vibrational spectroscopic studies
of the oxidation of organic compounds by hydrogen peroxide in liquid media. A focus of the work
is the identification of hypervalent non-porphyrin iron species thought to be reactive intermediates
in these oxidation reactions. Concurrently, high pressure kinetic techniques are being used to
elucidate the entry of ligands such as dioxygen into the well-packed active site of a nonheme iron
O2 carrier called myohemerythrin. Peroxidase enzymes trapped in inorganic sol-gel films and
monoliths show promise for bioremediation of waste sites. A carbon dioxide adduct of myoglobin
encapsulated in such an inorganic sol-gel has been prepared using supercritical carbon dioxide and
is being investigated by a combination of flash photolysis and mass spectroscopic techniques.
University of Utah
Salt Lake City, UT 84112
Department of Chemistry
Time-Resolved Analytical Methods for Liquid/Solid Interfaces
Many chemical phenomena that occur at boundaries between insulating solids and liquids
(adsorption, partition, monolayer self-assembly, catalysis, and chemical reactions) are critical to
energy-related analytical chemistry. These phenomena are central to developing chromatographic
methods, solid-phase extraction, immobilized analytical reagents, and optical sensors. The goal of
this program is to develop surface-sensitive spectroscopies by which chemical kinetics at
liquid/solid interfaces can be observed on timescales from nanoseconds to seconds.
Temperature-jump relaxation measurements are used to probe adsorption/desorption kinetics at
liquid/solid interfaces; kinetic barriers to adsorption of molecular ions onto alkylated silica
surfaces are being investigated. The lateral surface diffusion of molecules at liquid/solid interfaces
is being studied using fluorescence recovery after patterned photobleaching; these measurements
are providing information about the structure of alklyated-silica surfaces. Surface heterogeneity of
adsorption sites on silica has been examined by time-resolved fluorescence, and its chemical
origins investigated by 29Si nmr spectroscopy. Surface-enhanced Raman
spectroscopy is being used to study adsorption and binding to silica surfaces, deposited as thin
layers over silver- and gold-island films that enhance the Raman scattering of interfacial species.
Molecular dynamics simulations have been carried out to help better understand kinetic barriers to
adsorption. Stopped flow kinetic experiments, using dispersed, colloidal solids, are being
developed to monitor irreversible adsorption kinetics on a millisecond time scale.
University of Utah
Salt Lake City, UT 84112
Department of Metallurgical Engineering
Hydrophobic Character of Nonsulfide Mineral Surfaces as Influenced by Double Bond
Reactions of Adsorbed Unsaturated Collector Species
Froth flotation is one of the most important examples of applied surface chemistry and this
separation technology is used in the food, petroleum, pulp-paper, and mineral industries. Several
novel experimental techniques such as in situ Fourier transform infrared (FTIR) internal reflection
spectroscopy (IRS) with reactive internal reflection elements, multichannel laser Raman
spectroscopy, nonequilibrium laser-Doppler electrophoresis, and atomic force microscopy for
surface force measurements are being developed and/or used to analyze surfactant adsorption
phenomena at mineral/water interfaces and to describe the impact of adsorption phenomena on
the hydrophobic character of the surface. The nonsulfide flotation research includes the soluble
salt, semisoluble salt, and insoluble oxide mineral systems. Atomic force microscopy in concert
with FTIR/IRS techniques is currently being used to investigate the influence of the structure of
interfacial water on the short-range interparticle forces responsible for the adsorption of surfactant
colloids in soluble salt flotation. Significant progress has been made in understanding the nature of
the forces responsible for heterocoagulation of oppositely charged particles at high ionic strengths
by measuring interparticle forces using atomic force microscopy. Also, progress continues to be
made in spectroscopic characterization of interfacial water at both hydrophilic and hydrophobic
surfaces by depth profiling using in situ FTIR/IRS. In the category of semisoluble salt minerals,
carboxylic acid adsorption by fluorite, calcite, and apatite minerals is being examined by
FTIR/IRS using a polygon shaped IRE in order to obtain more reflections on a small crystal.
Interaction forces have been measured by atomic force microscopy between insoluble oxide
mineral systems such as silica/alumina at various pH values in order to understand the
aggregation/dispersion behavior of the above mineral suspensions.The effect of surface hydration
and interfacial water structure as determined from surface spectroscopy, on the interactions at
high ionic strengths, will provide further information on the relationship between collector
adsorption phenomena and hydrophobic state. The results obtained from this research program
will provide the basis for new reagent schedules to improve flotation separation efficiency and to
promote energy conservation.
Virginia Commonwealth University
Richmond, VA 23284
Department of Chemistry
Selective Methods for Quantification of Target Species in Complex Mixtures
The quantification of specific compounds in complex mixtures is a common goal in many
analytical methods. Here, two experimental approaches are coupled with chemometric data
analysis methods to explore the possibility of obtaining reliable, quantitative results subsequent to
chromatographic separations. The first approach is liquid chromatography coupled with
UV-visible diode array and mass spectral detection for the analysis of polyaromatic hydrocarbons,
metabolites, and pesticide residues. Quantification will be achieved by using methods such as
adaptive filtering, direct trilinear decomposition, and neural networks. Standard addition methods
can be used for calibration. In the second experimental approach, thin-layer chromatography will
be used to separate the analytes, and the kinetics of a subsequent derivatization reaction will be
used to resolve and quantify the species of interest on the thin-layer plates. This novel approach
has been applied successfully for the analysis of amino acids, and the trilinear decomposition
method has given satisfactory results for the quantitative resolution of the severely overlapped
amino acids, glutamine and glycine. Chemiluminescent-detection approaches based on these
principles are also being investigated.
Washington State University
Pullman, WA 99164
Department of Physics
UV Laser-Surface Interactions Relevant to Analytic Spectroscopy of Wide Bandgap
Materials
| Investigator(s) |
Dickinson, J.T.
|
$85,000 |
| Phone | 509-335-4914 |
| E-mail |
jtd@wsu.edu |
This research focuses on basic studies of the laser desorption and ablation of materials, in
particular those with bandgaps which exceed the photon energies of the incident light. The
mechanisms of emission and formation of ground state and excited neutral species, ions, and
free electrons are probed using time resolved optical spectroscopy, photoluminescence, charged
particle energy analysis, and angular distribution measurements. The existence and production of
point defects and their role in (a) photodesorption processes, (b) heating and vaporization, and (c)
plasma formation is of particular interest. Current studies involve imaging and quantifying defect
densities, the production of surface defects with particle bombardment and mechanical
stimulation, modeling the role of anion vacancies in photostimulated emission of cations, and
studies of laser interactions with inorganic solids containing covalently bonded anions which
photodecompose. The latter include nitrates, carbonates, and phosphates with a number of cations
such as alkali and alkaline earth metals. We have shown that photodecomposition of the oxyanion
controls and strongly increases the coupling of UV laser light to these materials, thus generating
highly non-linear responses. We also seek detailed understanding of the way electron
bombardment and mechanical stimulation of the surfaces modifies the laser interactions with these
materials, often enhancing emissions of charged particles and neutrals by several orders of
magnitude. A new model for defect dominated laser plume formation from wide bandgap
materials is under development and verification that excludes inverse bremstrahlung as a necessary
mechanism for heating of electrons in the plasma.
University of Wyoming
Laramie, WY 82071
Department of Chemistry
Solid-Matrix Luminescence Analysis
The development of a fundamental understanding of physicochemical interactions and
photophysical aspects for the room-temperature fluorescence and phosphorescence of aromatic
compounds adsorbed on solid matrices is the major goal of this project. Glucose, trehalose,
cyclodextrins, sodium acetate, and filter paper are used as solid matrices. Silicone treated filter
paper is employed to selectively remove polycyclic aromatic compounds from water and then the
isolated compounds are determined by solid-matrix luminescence. Distribution constants are
obtained for the compounds between the silicone treated filter paper and water, and they are used
to investigate the selectivity of the compounds for the filter paper. Solid-matrix luminescence
analytical data are obtained for several lumiphors in carbohydrate glasses. Also, phosphorescence
lifetimes, intensity data, and luminescence quantum yields are acquired as a function of
temperature for phosphors in glucose glasses with and without heavy atoms in the glasses to
calculate photophysical rate constants and elucidate the physicochemical interactions of the
phosphors in the glasses. The solid-matrix phosphorescence of perdeuterated phenanthrene
adsorbed on silicone treated filter paper and a modified sample cell are used to develop a novel
oxygen sensor. The sensor is employed over a wide range of oxygen concentrations, and it is very
sensitive to oxygen in the presence of carbon dioxide. A new form of solid-matrix luminescence
spectrometry is being developed in which the vibronic modes of the excited singlet state and
excited triplet state of lumiphors are detected by a combination of infrared and luminescence
spectrometry.
Last updated by Harry J. Dewey, (hd@lanl.gov) on December 23,
1996.