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.