Chemistry and Physics Published Research
Dr. Agyeman’s research covers the investigation of the properties and applications of clays with the use of modern analytical and physical techniques such as electrochemistry, spectroscopy, and microscopy. Specific projects include:
Investigation of clay properties.
Investigation of redox processes/mechanisms in clays.
Structural alteration of clays by incorporation of organic and inorganic molecules/ions.
Discovery and synthesis of new catalysts with emphasis on the use of clays as catalyst supports.
Development and characterization of electrochemical sensors based on clay composite modified electrodes.
Particles of clays are clusters or aggregates of platelets or layers. Each platelet is made up of “sheets.” Clay sheets found within soils are made up of crystals containing tetrahedral silicates (Si-O) and/or octahedral aluminates (Al-O, Al-OH). A clay platelet comprises of tetrahedral and octahedral sheets bonded together by the sharing of lateral oxygen atoms. Clays with one silicate sheet and one aluminate sheet are termed 1:1 clays (A, e.g. Kaolinite). Clays with one aluminate sheet sandwiched by two silicate sheets are termed 2:1 layer clays (B, e.g., Montmorillonite).
Clays are naturally abundant, nontoxic, able to form membrane-like films, and more stable than commonly used synthetic membranes (polymeric films). Clay film on an electrode surface provides important functions such as charge-exclusion, immobilization of species, preconcentration, catalysis of electrochemical reactions and electron transfer enhancement. These are important properties of polymeric films used for the development of electrochemical sensors. However, clay alone cannot solve the sensitivity and selectivity problem of electrochemical sensors, which makes it necessary to form clay composites, i.e., the incorporation of biomolecules and ionic species into clay interlayers. The Wyoming montmorillonite clay, which belongs to the group of smectites, is mainly used. This type of 2:1 layer clay displays unique properties such as small crystal size, large surface area, and membrane-like properties. It also exhibits hydration and intercalation characteristics of the negatively charged interlamellar surfaces (surfaces between layers), which is necessary for the immobilization of biomolecules and cationic species. These projects will advance scientific and environmental efforts including health care, forensic science, agriculture, and even environmental clean-up.
Agyeman, A. Adsorption Studies and Selective Determination of Epinephrine at Glycerol-Clay Modified Glassy Carbon Electrode. International Journal of Electrochemical Science 2017, 12(10), pp 9601-9618. http://www.electrochemsci.org/papers/vol12/121009601.pdf
Agyeman, A., Pugh, M., Hackney, V. Glycerol-Octanohydroxamate-Clay Composite Film for Selective Voltammetric Analysis of Charged Species. International Journal of Science, Commerce, and Humanities 2017, 5(2), pp 13-24. http://www.ijsch.com/journaluk/
Fitch, A., Agyeman, A., Wagdy, A., Terranova, Z. Electroactive Planar Waveguide Studies of Tris(2, 2`-bipyridyl)ruthenium(II) Intercalated in a Thin Clay Film. I. Transport and Electrochemical Phenomena. Langmuir 2011, 27(1), pp 452-460. http://pubs.acs.org/Langmuir
Dr. Dyer’s research interests are towards investigating electroactive materials for a variety of applications ranging from electrochromic and light-emitting displays, charge storage devices, and sensors. The materials of interest include those that elicit a response to redox switching with the responses including color changes, light emission, and charge generation. Her research is focused on active material characterization and the design and study of novel device architectures involving these active materials. The active materials include conjugated organic small molecules, transition metal complexes, metal oxides, and conjugated polymers. Several analytical techniques are utilized in studying the electroactive materials and include electrochemistry, conductivity, UV/Vis spectroscopy, colorimetry, and film morphology. Her recent focus has been towards utilizing materials that are aqueous processable and utilize materials of low environmental impact.
The two current research projects are:
Understanding the electrochemistry and optical properties of conjugated polymers that
contain ionic functional groups. Many conjugated polymers have organic functional
groups, which allow them to be soluble (and processable) from common organic solvents.
While this is beneficial for organic synthesis and characterization of the polymer
properties, for processing and applications, aqueous processability would be desired.
In a collaboration with the Reynolds group at Georgia Tech, Dr. Dyer is investigating
the electrochemical (redox properties, charge generation and transfer) and optical
(color, optical absorption, refractive index) properties of these polymers as a function
of the ionic groups, their location relative to the polymer backbone, and comparison
to those polymers that do not have ionic functional groups.
Utilization of aqueous compatible electroactive materials in flexible devices containing nontoxic electrolytes. A large number of electroactive devices (electrochromics and electrochemical supercapacitors) utilize organic solvents and electrolytes, which may be unattractive in many applications. We are investigating the use of aqueous flexible solid electrolytes that can be either transparent or opaque and have high ionic conductivities. We are looking at optimization of the device structure and electrolyte components, and understanding device properties (e.g., efficiency at varying temperatures, stability under mechanical stresses, etc.). The active materials utilized in these devices can include the above mentioned ionic conjugated polymers, viologens, metal oxides, and transition metal complexes.
Dyer, A.L., Österholm, A. M., Shen, D. E., Johnson, K.E., Reynolds, J.R., (2015) "Conjugated Electrochromic Polymers: Structure-Driven Colour and Processing Control", in Electrochromic Materials and Devices, Wiley-VCH, Mortimer, Rosseinsky, and Monk, editors.
Padilla, J., Österholm, A. M., Dyer, A. L., Reynolds, J. R.. (2015) Process controlled performance for soluble electrochromic polymers. Solar Energy Materials and Solar Cells, 140, 54
Jensen, J., Hösel, M., Dyer, A. L., Krebs, F. C. (2015) Development and Manufacture of Polymer‐Based Electrochromic Devices. Advanced Functional Materials, 25, 2073.
Kerszulis, J., Johnson, K., Kuepfert, M., Khoshabo, D., Dyer, A. L., Reynolds, J. R. (2015). Tuning the Painter’s Palette: Subtle Steric Effects on Spectra and Colour in Conjugated Electrochromic Polymers. Journal of Materials Chemistry, C, 3, 3211-3218.
Bulloch, R. H., Kerszulis, J., Dyer, A. L., Reynolds, J. R. (2015). An Electrochromic Painter’s Palette: Color Mixing via Solution Co-Processing. ACS Applied Materials and Interfaces, 7(3), 1406-1412.
Österholm, A. M., Shen, D. E., Kerszulis, J. A., Bulloch, R. H., Kuepfert, M., Dyer, A. L., Reynolds, J. R. (2015) Four Shades of Brown: Tuning of Electrochromic Polymer Blends Toward High-Contrast Eyewear. ACS Applied Materials & Interfaces, 7, 1413.
Kerszulis, J., Amb, C. M., Dyer, A. L., Reynolds, J. R. (2014). Follow the Yellow Brick Road: Structural Optimization of Vibrant Yellow-to-Transmissive Electrochromic Conjugated Polymers. Macromolecules, 47, 5462.
Bulloch, R. H., Kerszulis, J., Dyer, A. L., Reynolds, J. R. (2014). Mapping the broad CMY subtractive primary color gamut using a dual-active electrochromic device. ACS Applied Materials and Interfaces, 14, 6623.
Dyer, A. L., Bulloch, R. H., Zhou, Y., Kippelen, B., Reynolds, J. R. (2014). A vertically integrated solar-powered electrochromic window for energy efficient buildings. Advanced Materials, 26, 4895.
Shen, D. E., Estrada, L. A., Osterholm, A., Salazar, D. H., Dyer, A. L., Reynolds, J. R. (2014). Understanding the effects of electrochemical parameters on the area capacitance of electroactive polymers. Journal of Materials Chemistry A, 2, 7509.
Osterholm, A., Shen, D. E., Dyer, A. L., Reynolds, J. R. (2013). Optimization of PEDOT films in ionic liquid supercapacitors: Demonstration as a power source for polymer electrochromic devices. ACS Applied Materials and Interfaces, 26, 13432.
Jensen, J., Dyer, A. L., Shen, D. E., Krebs, F., Reynolds, J. R. (2013). Direct photopatterning of electrochromic polymers. Advanced Functional Materials, 23, 3728.
Chemical Education: I am currently mentoring internship projects in Organic or Medicinal Chemistry. Examples of student projects include developing and teaching a lab experiment or lab practical, or development of an instructional webpage, course material, or activity.
Microbiology collaborations: Dr. Michelle Furlong and I have guided multiple cross-disciplinary collaborations between the organic chemistry laboratory and the microbiology laboratory. These collaborations are ongoing and include the synthesis and investigation of PABA derivatives and sulfa drug derivatives. Research students involved in these projects will work with either or both laboratories to guide students through the projects.
Organic Synthesis: I have mentored several undergraduate students in projects designed to investigate the synthesis of novel sulfa drugs derived from sulfanilamide. The goal is to find a compound that retains the bacteriostatic properties of other known sulfa drugs while remaining nontoxic to humans. Sulfanilamide can be readily synthesized in a multi-step synthesis from acetanilide; derivatives are formed using various amines in place of ammonia in this synthesis.
Photochemistry: My research interests lie in the general areas of photochemistry and physical organic chemistry. In particular, I study proton-transfer reactions of hydroxyarene compounds in the excited state. Previous research projects included the investigation of the dynamics of photoacids (a series of synthesized derivatives of 2-naphthol or hydroxyquinoline N-oxides) in microheterogeneous conditions using both steady-state and time-resolved fluorescence measurements. The effects of additional cyano, aminomethyl, maleimide, or perfluoroalkanesulfonyl substituents were studied in aqueous and non-aqueous solutions, as well as at polymer-water and protein-water interfaces.
If you are interested in working with Dr. Clower on any of the projects listed above, contact her at (CarolineSheppard@clayton.edu). The course credit given (3223/3224/4222) and the pre-requisite requirements for participation will vary depending on the nature of the project. See Dr. Clower for details.
Burnett, S. C., Singiser, R., and Clower, C. E. “Teaching about ethics and the process of science using retracted publications.” Journal of College Science Teaching, 2014, 43(3), 24-29.
Singiser, R., Clower, C. E., and Burnett, S. C. “Preparing Ethical Chemists through a Sophomore Seminar Course.” Journal of Chemical Education, 2012, 89(9), 1144-1147.
Furlong, M. A., Clower, C. E., and McFarlane, R. E. “Cross-Disciplinary Collaborative Laboratory Activities that Reinforce Chemistry Content Knowledge.” MicrobeLibrary Curriculum Collection, 2008.
Kodani, C., Boudell, J., Braun, J., Clower, C., and Jordan, J. “Group Size Can Affect Field Trip Effectiveness.” Georgia Science Teacher, 2006.
- M. Solntsev, C. Clower, J. Kowalik, L. M. Tolbert, and D. Huppert. “6-Hydroxyquinoline-N-oxides: A New Class of "Super" Photoacids” J. Am. Chem. Soc., 2005, 127, 8534-8544.
- Clower, K. M. Solntsev, J. Kowalik, L. M. Tolbert, and D. Huppert. “Photochemistry of "Super" Photoacids. 3. Excited-State Proton Transfer from Perfluoroalkylsulfonyl-Substituted 2-Naphthols.” J. Phys. Chem. A., 2002, 106(13), 3114-3122.
- Clower. "Proton Transfer Dynamics of Novel Photoexcited Hydroxyarenes." Doctoral Thesis, School of Chemistry and Biochemistry, Georgia Institute of Technology, 2002.
- A. Orwoll, R. M. Bakhshi, K. D. Bakhshi, K. M. Morgan, C. Clower, R. E. Ward. "Dipole Moments, Densities, and Thermal Expansion Coefficients of N-substituted Phthalimides." Abstracts of Papers of the American Chemical Society, March 2000, 219(2), 419.
- Kowalik, D. VanDerveer, C. Clower, and L. M. Tolbert. “Hydrogen Bonding and Cooperativity Effects on the Assembly of Alkyl- and Perfluoroalkyl-sulfonyl Naphthols: F∙∙∙F Non-bonded Interactions.” Chemical Communications, 1999, (19), 2007.
My research on the cytoskeletal protein talin combines multiple areas of the biological sciences to address questions related to cell function and disease. Talin is a very large protein that links the extracellular matrix to the actin cytoskeleton. Talin provides a framework for other proteins to bind and assist in the formation of large, multi-protein complexes called focal adhesions. Dysregulation of focal adhesions can lead to a variety of diseases including cancer metastasis. Research on talin applies many laboratory techniques from multiple disciplines of science, including biochemistry, cell biology, and molecular biology. The motivated student doing research on this project will have the opportunity to do integrative research applying skills they have learned in multiple classes.
Expansion of Chemical Literature
Higher education is in constant flux. Over the last 100 years, there has been great growth in higher education. With that growth, there have been many more research publications produced. This project is examining whether or not that expansion in higher education matches the expansion in literature or if there are other forces at play.
Biochemistry Teaching Labs
My work on biochemistry teaching labs involves applying concepts in biochemistry to unique laboratory experiences for undergraduate students. A few of the labs that are currently in preparation involve amino acid identification, protein purification, protein separation, protein identification, and enzyme kinetics. Nucleic acid identification, purification, amplification, and separation labs are also being developed. Labs involving both lipids and carbohydrate chemistry are being prepared as well. Research in this area will provide the interested student with the opportunity to learn new laboratory skills and to begin developing independent scientific investigation skills.
I am looking for a student with some art skills to help design and produce biochemistry interactive animations. One does not need to have knowledge of biochemistry, but must have basic computer skills. Please see me if you are interested in this project.
Burnett, S. C., Furlong, M. A., Melvin, P., Singiser, R. (2016). Games that Enlist Collective Intelligence to Solve Complex Scientific Problems. Journal of Microbiology and Biology Education, 17(1), 133-136. www.asmscience.org/content/journal/jmbe/10.1128/jmbe.v17i1.983
Callier, V., Singiser, R., Vanderford, N. (2015). The parlous state of academia: When politics, prestige and proxies overtake higher education’s teaching mission. Australian Universities' Review, online. http://issuu.com/nteu/docs/aur_57-01
Callier, V., Singiser, R., Vanderford, N. (2014). Connecting undergraduate science education with the needs of today’s graduates. F1000 Research, online. f1000research.com/articles/3-279/v1
Burnett, S. C., Singiser, R., Clower, C. E. (2014). Teaching about ethics and the process of science using retracted publications. Journal of College Science Teaching, 43(3), 24-29.