Research Topics

In the interest of providing an option of diverse research opportunities, we offer experiences with faculty members in several specialties including organic, inorganic, biochemistry, organometallic syntheses with compound characterization, environmental analytical chemistry, nuclear chemistry, materials science, and physical chemistry.  There has been a separately funded materials science REU site at JMU which is housed in the same building as the chemistry site.  As has been the case in the past three years, there will be considerable interaction and overlap between these two sites.  General aspects of projects that are representative of the diverse nature of our student research opportunities are described below.  Additional projects may be found in the materials science and regional NMR websites: http://www.jmu.edu/chemistry/svrnmr/ and http://csm.jmu.edu/matsreu/.

 

 

Brian Augustine, "In-situ Biodegradation in PHAs Thin Films" and "Surface Engineering of Biomaterials"

Polyhydroxyalkanoates (PHAs) are a biologically produced class of polymers used by bacteria as an energy storage media when carbon levels are high and other necessary nutrients such as nitrogen, phosphate, and sulfur are low. PHA is efficiently produced as an intracellular inclusion body (called a "granule") occupying up to 90% of the dry cell weight of the bacteria. When there is a deficiency of carbon, the bacteria are able to produce a depolymerase enzyme to break down the PHA and use the energy stored in the inclusion body.  The bacteria capable of this energy transformation exists naturally in nearly all water, soil and sewer environments, and thus PHA-based polymers are all naturally biodegradable. We are using atomic force microscopy (AFM) to monitor the biodegradation of PHA thin films in both in-situ and ex-situ experiments (Figure 1).

 

Several unresolved issues in understanding PHA biodegradation could be addressed through AFM studies.  The first is a better understanding of whether the depolymerization preferentially occurs in amorphous or crystalline regions in these thin films.  We have used the high-resolution phase imaging capability of AFM to characterize the P(3HB-3HV) thin films. A lamellar structure is observed using phase contrast AFM within the PHA spherulites that is not seen in ordinary topographic AFM (data not shown).  The size of the lamellae are on the order of 12 nm.  We believe that the contrast observed is due to differences in the mechanical response of the crystalline and amorphous regions of the thin film.

A second area of inquiry is in the surface engineering of biomaterials using soft-lithographic patterning techniques.  We can control the location of PHA deposition using self-assembled monolayer (SAM) technology and microcontact printing (m-CP) reported by Xia and Whitesides.  Alkanethiol self-assembly to gold surfaces has been widely reported in the last decade.  Coupled with polydimethyl siloxane (PDMS) stamp fabrication, a novel means of fabrication using molecular SAM resists has been developed.  We have reproduced Xia's results by using m-CP and SAMs as molecular resists to etch Au and Ag films.  An example of this work is shown in Figure 2.  In addition to selective etching, one can control the adhesion properties and hydrophobicity of a surface by changing the terminating functional group of the adsorbed alkanethiol. It is well known that PHAs are highly hydrophobic materials, and we believe that by controlling the surface chemistry through SAMs and m-CP, we will have a method of patterning thin films of PHA for an internal height degradation standard. This method has been used to pattern polyurethane by selective dewetting. To date, there are few means of microfabrication of biological surfaces as conventional pattern transfer technologies developed for the semiconductor industry such as photolithography and etching are often destructive to organic and biological materials. The development of these soft lithography techniques is very important to future improvements in biological materials and interfaces. These techniques can be extended to many other biological surfaces and represent and exciting path to the microfabrication of biologically active surfaces.

Kevin Caran "Amphiphilic Catenanes"

The synthesis, characterization, and colloidal study of amphiphilic molecules containing mechanical catenane bonds will be explored in this research. Mechanically-linked molecules have only rarely entered the arena of colloid chemistry. The catenane portion of the proposed compounds (which serves as the amphiphile's polar head group) consists of a crown ether macrocycle intertwined with a tetracationic cyclophane macrocycle. Incorporation of this uncommon, highly charged mechanical linkage into amphiphiles may have a profound effect on their aggregation due to unique dynamic processes associated with catenanes.  This research lies at the intersection of colloid chemistry and catenane chemistry, and attempts to answer the following question: How would incorporation of a "mechanical" catenane bond into the head group of an amphiphile affect its colloidal aggregation? The catenation of the polar head group will introduce novel dynamic processes at the interfacial region of aggregates formed by such molecules. These processes, namely rocking, rattling and rotation of the macrocycles within each other, should give rise to unique and interesting colloidal properties.

 

B.A. DeGraff, "Luminescent Sensors"

Research activities have focused on two areas.  First is the synthesis, characterization, and application of luminescent transition metal complexes.  Currently our main emphasis is on materials that can be used in various applications as sensors such as oxygen, pH, CO₂, and certain metal ions (Na⁺, K⁺, Mg²⁺, and Ca²⁺) of either physiological or environmental importance.  In the process of constructing sensors using our luminescent molecules, we have required polymer supports into which the sensor materials are incorporated.  In this process, we have encountered a number of effects which have a significant impact on sensor performance and which we must understand at a fundamental level if we are to rationally design improved systems.  However, the very effects that daunt our efforts in sensor development offer significant opportunities for exploration of the microstructure of the polymer support.   The luminescent materials we have developed are excellent probes for variation in polymer structure and behavior on the microscopic level.  The second effort is directed towards developing modest cost laboratory experiments for the undergraduate curriculum with an emphasis on either materials or applications of laser technology.

 

Thomas C. DeVore, "Catalytic Oxidation of VOC by Metal Oxides and Supported Metal Oxides"

Catalytic oxidation is a promising method for removing volatile organic compounds (VOC) from the environment. Since the reactions between the catalyst surface and the VOC has been suggested as a possible step in the reaction mechanism, we are investigating the reactions of chlorocarbons and small alcohols with supported and unsupported metal oxides.  Supported metal oxide catalysts have been prepared using several methods. The supported catalysts used in this investigation will be prepared using the solution method.  A precursor is dissolved in an appropriate solvent and the resulting solution is mixed with the support.  This mixture can then be heated in air to form the supported metal oxide.  One goal of this project will be to investigate the kinetics of the chemical reactions that occur when the 2,4-pentanedionato complexes of vanadyl, chromium, manganese, iron, cobalt, nickel, copper and zinc thermally decompose while supported on alumina, silica, titania, magnesium oxide, and calcium oxide.  These metals were chosen because their oxides have been used to catalyze several reactions and these investigations. The supports chosen are commonly used and have acid-base properties ranging from acidic to basic.  This investigation should provide a more complete picture about the effects of substrate acidity on the decomposition mechanism for the 2,4-pentanedionato complexes.  Understanding the chemical reactions that produce the catalyst could lead to the formation of better catalysts and/or establish more efficient routes for preparing supported catalysts that have the desired properties.  Thermal Gravimetric Analysis-Mass Spectroscopy and Evolved Gas analysis- FTIR will be used to monitor the mass change and the gases evolved as the supported acetylacetonate complex decomposes.  FTIR, powder X-ray diffraction, and scanning electron microscopy will be used to examine the solids that are produced.  The kinetics of these decomposition processes can be generated from this data using the procedures given by Brown.²  

Once prepared, the catalyst will be characterized using Temperature Programmed Desorption and Flow Kinetics.  Both experiments can also be done using the TGA-MS and the EGA-FTIR. TPD is an established technique for characterizing catalyst sites.   For example, 2-propanol can be used to establish if the compound has acidic or basic catalytic sites since acidic sites produce propene while basic sites generate propanone (acetone).  Flow kinetics will be used to more fully characterize reaction pathways for the more promising reactions.  The kinetics for the supported reactions are compared to those measured for the unsupported oxides to provide insight into the effect the support had on the process.

 

Daniel M. Downey, "Environmental Analytical Research Projects"

            Research in this group is currently focusing on three areas of environmentally oriented research.  Inductively coupled plasma/mass spectrometry (ICP/MS) is being studied for use in the analysis of trace elements in fish otoliths. Otoliths (ear bones) grow continuously during the life of a fish and thus may serve as a temporal record of environmental conditions to which the fish may have been exposed.  We are developing analytical methodology for freshwater species that are collected from streams and lakes where toxic metals (Hg, Cr, etc.) have been introduced and solid phase extraction methods for preconcentration. We plan to use laser abalation sample introduction to extend detection limits with equipment to be purchased for the new building.  A second area of research is in the use of super critical fluid extraction for recovery of pesticides and herbicides from soil samples.  Currently we are studying the recovery of triclopyr CO₂ a pyridine herbicide, from samples with supercritical CO₂ and methanol mixture, followed by analysis with GC/ECD.  We are particularly interested in extending this work to the recovery of dimilin, a popular gypsy moth pesticide, and its degradation products.  The third area of research has been application of ion chromatography and other methods for assessment of "acid-rain" impacts.  Field data are collected in these studies and are used to help fisheries managers develop mitigation management strategies.   Students involved in these projects will collect samples in the National Forests or State Game Lands of Virginia, and return them to the laboratory for analysis.  Data thus generated will be used to assess the relative impact of acid deposition on water bodies.  Students will be expected to learn data interpretation as well as the analytical methodology involved.

 

John W. Gilje & Donna S. Amenta, "Synthesis of Crown Ether Containing Metal Complexes"

Donna Amenta, an organic chemist, and John Gilje, an inorganic chemist, have collaborated extensively over the last few years. Their mutual research is designed to integrate organic and inorganic chemistry.   A current problem centers on the synthesis of crown ether-containing transition metal complexes in which catalytic activity and/or product selectivity is "switched" on or off through binding of simple cations by crown ether units.   One project addresses our hypothesis that the migratory insertion reaction depicted in Scheme 1 for a transition metal carbonyl complex can be accelerated by the addition of added cation when R is a crown ether.

There is precedent in the literature to support this hypothesis.   The presence of Lewis acids has been shown to activate the carbon of metal carbonyl complexes toward nucleophilic attack. Included among the reports are increased reactivity induced by cations held in proximity to metal-bonded CO's by crown ether and crown ether-like ligand.   Preliminary studies performed in our laboratory, suggest that the number of intervening methylene groups between the metal site and the benzo-crown ether are critical in providing the correct conformation for interaction between a CO and the cation trapped within the crown.  Molecular modeling indicates that a three-methylene group spacer provides the flexibility required to place the crown ether in a favorable conformation for complexation with a terminal carbonyl group.  We therefore propose to investigate migratory insertion reactions of crown ether substituted metal carbonyl complexes that contain a three-methylene group spacer between the metal and the crown ether (Scheme 1, x = 3). Initially, CpMo(CO)₃[(CH₂)₃crown] will be synthesized using a modification of several literature procedures.  Kinetic studies then will be conducted both in the presence and absence of added cation. A similar study of CpMo(CO)₃{[CH₂]₃[C₆H ₃(OCH₃)₂]}, a model that does not contain a crown ether, shows no increased reactivity with added cation.

 

Katy Layman, "Spectroscopy at solid-liquid interfaces in heterogeneous catalysts"
            Recent research endeavors in heterogeneous catalysis have focused on developing biomimetic systems (e.g. artificial photosynthetic devices based on their biological counterparts), and on implementing heterogeneous catalysis in the fine chemicals and pharmaceutical industries.These processes involve chemical reactions that occur at the solid-liquid interface.Heterogeneous catalysis at solid-liquid interfaces also plays an important role in many biochemical, atmospheric, and geochemical processes. Despite the importance of solid-liquid interfaces in enzyme catalysis and heterogeneous catalysis, few in situ studies have focused on catalytic solid-liquid interfaces.My research endeavors focus on the development of in situ attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy to characterize the surface properties of heterogeneous catalysts while in the presence of liquid phase reactants.

 

Scott Lewis, "Synthesis of 1,3-Difluoroaromatic compounds"

            Research in the Lewis lab revolves around the unique method of preparing 1,3-difluoroaromatic compounds.  This is accomplished in one pot starting from substituted cyclobutenes via the addition of difluorocarbene.  To date, the method has proven reliable using aryl and alkyl substituted cyclobutenes with both Ph-Hg-CF₃ and NaCF₂ClCO₂ as carbene sources as:

 

 

Barbara A. Reisner, "The role of synthetic conditions on product formation and dimensionality in metal phosphonates"

The ability to design new materials with specific properties hinges upon the ability to control synthetic parameter space to produce these materials.  While synthesis has always been important to materials chemistry, there has been a renewed interest in understanding how synthesis conditions affect the structure and properties of materials.  Organic-inorganic hybrids, such as metal phosphonates, are one important class of compounds, with potential applications in catalysis, separations, molecular recognition, and optics. Currently we are investigating the role that synthetic variables play in the assembly of phosphonates.  The goals of our current research program are twofold: to synthesize and characterize new transition metal phosphonates with novel architectures and to better understand the chemical phenomena that influence the formation of their structures.  By examining the products of reactions that occur in different regions of parameter space, we can begin to understand how these conditions affect product formation.  Eventually, we hope to gain a thorough understanding of synthetic phase space so that we can use specific conditions to synthesize materials with desired properties.  We are exploring the chemistry of derivatized phosphonates including amines, nitrites, and sulfonates.  Several of these phosphonates are commercially available; other are readily synthesized using well know reactions.  Much of our work to date has focused on the chemistry of aminophosphonic acids.  We have discovered that synthesis conditions greatly affect the dimensionality of the phosphonates derived from n-aminoalkylphosphonic acids; a decrease in the pH of synthetic conditions resulting in a corresponding decrease in dimensionality. We have seen similar effects in other systems and are exploiting reaction conditions to synthesize a variety of new phosphonates derived from phosphonic acids and esters.  Several new layered materials incorporating 4-aminobenzylphosphonic and divalent transition metals have also been synthesized.  Work is underway to characterize these materials.

 

Brenda C. Seal, Department of Communication Sciences and Disorders, "Developing Tools to Assist Interpreters in Communicating Science to the Deaf"

The involvement of undergraduate students who are majoring in communication disorders in interpreting for the deaf is complicated not only by having to learn to sign ordinary words and phrases, but also by their general lack of familiarity with scientific terms.  In fact, it has been noted that this is the main obstacle for deaf and hearing-impaired people to gain access to the sciences.  Few teachers have been trained for signing in science.  Often deaf students in the school systems are steered away from the sciences by counselors and teachers who naturally favor areas in which they themselves are more comfortable. In the JMU REU program, student interpreters will be assigned to each research group with deaf participants.  The deaf students will be mentored by the chemistry faculty member directing each group.  The student interpreters will be mentored by Dr. Seal who will not only train them and assist them on a day-by-day basis, but also use the opportunity to study the special needs for this system of communication.  The mission will be twofold: to make communication between the chemistry faculty and deaf students as simple and convenient as possible and to provide a research/learning experience for the interpreters.  The interpreting group effort will also include one high school teacher who can hear but is responsible for educating the deaf, and one deaf teacher who teaches science at VSDB or another deaf school.  There will also be two high school students: one who can hear and one who is deaf.  The importance of recruiting deaf people into science at an early age has already been noted, The inclusion of a second high school student of similar age will assist in making the deaf student feel more a part of the group, as well as providing that student with the developmental benefits of involvement in college research.  With the use of videotaping, observation, literature use, daily journals and record keeping and other methods of studying the interaction, it is expected that methods and tools will be developed to assist in training interpreters.  The information thus collected will be disseminated through presentations at conferences such as the "Technology and Persons with Disabilities" conference and the "Interpreters for the Deaf International Convention" and by journal and CD publications.