Interference of TiO ₂ in Fricke Dosimetry: Adsorption Mechanisms and Dose Measurement Challenges under Gamma Irradiation

This review examines the interaction between Fricke dosimetry and TiO₂ under gamma irradiation, highlighting the potential interference of TiO₂ in standard dosimetric systems, particularly when this semiconductor is employed as a radiosensitizer (or, more accurately, a radiocatalyzer). The classical Fricke dosimetry, based on the radiolytic oxidation of Fe²⁺ to Fe³⁺, may be influenced by TiO₂ through adsorption, therefore compromising dose accuracy. A recopilation of information on adsorption phenomena from both kinetic and equilibrium perspectives, applying classical and advanced models to characterize the retention of Fe²⁺ and Fe³⁺ on TiO₂ surfaces, was performed. Particular attention is given to multicomponent systems that reflect the competitive nature of adsorption under Fricke conditions (acidic medium). We discuss how these interactions affect dosimetric responses, potentially leading to the underestimation of the radiation absorbed doses. Although the increasing use of TiO₂ in radiocatalysis and advanced oxidation processes, standardized protocols for chemical dosimetry in such conditions are still missing. Research gaps include insufficient adsorption mechanistic studies, limited application of multicomponent models, and scarce integration of adsorption parameters into dosimetric assessments. Finally, methodological approaches to enhance dosimetric reliability in the presence of TiO₂ were proposed, thereby contributing to the development of accurate and reproducible systems for several applications.