Focus areas

• Radiochemistry; actinide chemistry
• Nuclear materials
• Materials characterization

Research interests 

The Forbes Research Group at the University of Iowa sits at the intersection of radiochemistry, materials science, and environmental chemistry. Our mission is to resolve the fundamental chemical challenges of the nuclear fuel cycle, develop new chemical signatures for nuclear forensics, and create next-generation materials for a sustainable future.  We are also interested in supporting novel radiochemistry workforce development strategies to train the next generation of talent in the energy, medicine, and environmental sectors.

Fundamental Actinide Science & Speciation

We investigate the complex chemical behavior of high-valent actinides (An), specifically uranium (U) and neptunium (Np). Our work focuses on understanding actinyl oxo group reactivity in pentavalent and hexavalent systems - a critical factor in predicting how nuclear materials behave in environmental systems and waste repositories. In addition, we are exploring Np(VII) chemistry, which has unique, but poorly understood properties and behavior.

• Key Focus: Using a combination of low-temperature synthesis and advanced spectroscopic techniques (Raman, EPR), we probe non-covalent interactions (NCIs) that stabilize An(V), An(VI), and An(VII) materials.
• Impact: This research provides the speciation, reactivity, and detection data needed to design safer long-term storage solutions and more efficient separation technologies.

Radiation Effects in Actinide & Hybrid Materials

Nuclear materials are constantly bombarded by ionizing radiation, yet the atomistic-level chemistry of these solids is not fully understood. Our group is at the forefront of exploring how ionizing radiation influences the chemical behavior of both inorganic actinide complexes and organic-inorganic hybrid materials.

• Key Focus: We study radiation-induced defects and the formation of radical species (like superoxide) in actinide solids. We also investigate the cascade reactions that result from this highly reactive radical species.
• Impact: By identifying the specific effects of chemical identity, bonding environment, and crystal packing, we are developing rules for materials chemistry reactivity in extreme radiation environments.

Novel methods for critical material separations

Traditional chemical processing of rare earth elements and nuclear materials often relies on large volumes of corrosive solvents, which generate significant quantities of secondary hazardous or radioactive liquid waste.

• Key Focus: We are investigating how mechanical energy can activate and solubilize stable nuclear phases, such as converting U(IV)O₂ to U(VI) triperoxide phases or creating soluble rare earth phases out of insoluble precursors.  We are also interested in developing new molecularly imprinted materials (collaboration with Professor Dave Cwiertny) for critical material recovery.
• Impact: This work has direct implications for the dissolution of spent nuclear fuel and new methods for separations, offering a faster and more energy-efficient pathway for material reprocessing.

Radiochemistry Workforce Development

The University of Iowa has established radiochemistry as a strategic area of departmental strength to address the critical national workforce shortage across the energy, medicine, and environmental sectors. Supported by multiple funding agencies, my research team also supports curriculum development efforts that has evolved from a traditional "pipeline" into a "career highway" model, which offers flexible "on-ramps" for students and working professionals to gain specialized expertise.

Key components of our curriculum development include:

• Foundation Coursework: Our traditional core radiochemistry course (CHEM:4760) is transitioning to an annual offering to meet high demand, having introduced 247 students to radiochemistry concepts and applications over the past decade.

• Radiochemistry Graduate Certificate: Launched in 2024 with the Association of Public Health Laboratories (APHL), this first-of-its-kind program for continuing radiochemistry education features asynchronous online modules and intensive two-week summer laboratory residencies focused on EPA and ASTM methodologies. By 2027, we aim to expand our modular tracks into the medical and energy sectors.

• Advanced Facilities: With support from the Carver Trust Foundation and APHL we have an upgraded our shared radiochemistry laboratories with state-of-the-art instrumentation to support hands-on training and research in environmental monitoring, radiopharmaceutical development, and nuclear energy.

• Virtual reality and AI-assisted training:  We are interested in creating new strategies in radiochemistry education that use novel virtual reality technologies and train workers to integrate AI tools. 

Recent publications

Rajapaksha, H., G. C. Benthin, E. L. Markun, C. J. Flester, S. E. Mason, T. Z. Forbes, “Bonding and reactivity of isostructural uranyl and neptunyl peroxide phases.” (2025) Chemistry Communications (invited article – Special edition on f-block chemistry)  8, 385. https://doi.org/10.1038/s42004-025-01733-6

Celik, E, D. May, K. P. Carter, R. Riessen, S. Wright, J. Nassif, R. S. Cole, and T. Z. Forbes “Novel approaches to meeting the radiochemistry workforce needs:  A case study of the University of Iowa Radiochemistry Graduate Certificate program” (2025) Journal of Radiochemistry and Nuclear Chemistry https://doi.org/10.1007/s10967-025-10400-y

Markun, E. L, A. B. Motes, T. Z. Forbes “Mechanochemical oxidation and dissolution of uranium oxide phases: Implications for nuclear material processing.” (2025) Journal of Nuclear Materials, 617, 156142 https://doi.org/10.1016/j.jnucmat.2025.156142

Kruse, S.J., S. K. Scherrer, G. P. Horne, J. A. LaVerne, T. Z. Forbes “The inorganic chemist’s guide to actinide radiation chemistry: A review.”  (2025) Inorganic Chemistry Frontiers, 12, 6398-6434 https://doi.org/10.1039/D5QI00975H

Rajapaksha, H., Kruse, S. J., J.A. LaVerne, S.E. Mason, T. Z. Forbes “Radiation-effects in uranyl tetrachloro coordination compounds:  Impacts of lattice water.”  (2025) Inorganic Chemistry 64, 9652-9661. https://doi.org/10.1021/acs.inorgchem.5c00693

Benthin, G. C., H. Rajapaksha, E. L. Markun, S.E. Mason and T. Z. Forbes “Probing the Protonation and Stability of Heptavalent Neptunium with Computational Guidance.” (2024) Dalton Transactions, 3, 16170-16185 https://doi.org/10.1039/D4DT01706D

Kruse, S. J., H. Rajapaksha, J. A. LaVerne, S.E. Mason, and T. Z. Forbes “Radiation-Induced Defects in Uranyl Trinitrate Solids”, (2024) Chemistry -A European Journal 30, e202400956. https://doi.org/10.1002/chem.202400956

Scherrer, S., S. M. Greer, H. Rajapaksha, B. W. Stein* and T. Z. Forbes* “Superoxide Radicals in Uranyl Peroxide Solids:  Lasting Signatures Identified by Electron Paramagnetic Resonance Spectroscopy” (2024) Angewandte Chemie 136, e202400379. https://doi.org/10.1002/anie.202400379