Gelis is an professor in the Department of Chemistry and Biochemistry and is the Director of the Radiochemistry Program at UNLV. As the program director, he manages the daily operations of the Radiochemistry Laboratory Complex (RLC). Gelis has a strong background and extensive experience in radiochemical separation techniques (solvent extraction, ion exchange) and actinide (Np, Pu, Am) solution chemistry. His expertise also includes radiochemical analytical methods (gamma-counting, LSC, alpha spectroscopy); electrochemistry, various spectroscopic techniques, kinetics and microfluidics.

His research interests lie in the area of actinide separations and speciation in aqueous and organic media; medical (e.g. Mo-99) isotope production and separation; and microfluidics relevant to the radio-analytical applications. Gelis has been the main contributor of the ALSEP process R&D. He has published more than 55 articles in peer reviewed journals in the field of radiochemistry.

Gelis is also an active Ph.D. advisor and is currently mentoring one post-doctoral researcher and seven graduate students.