RT-MAP will develop novel hollow iron oxide particles and assess their reactivity, stability and mobility under flow through porous media. Such hollow magnetic particles (h-MPs) have aroused great interest for their potential to encapsulate and control reagent release for environmental remediation and/or heterogeneous catalysis. Most available reactivity assessment studies rely on the interpretation of breakthrough curves measurement at the outlet batch tests or column experiments and do not allow a direct visualization of pore scale transport and reaction phenomena. RT-MAP will develop novel microfluidic cells, providing a new window on coupled flow and reaction processes at the microscale, a key to modeling and predicting macroscale reaction rates. The combination of complementary expertise of the fellow (material synthesis and characterization), and the supervisor and co-supervisors (molecular geochemistry, reactive transport in porous media, microfluidics) will offer a unique opportunity to address these emerging scientific questions. We will thus fabricate microfluidic cells providing spatially resolved concentration fields under flow through reactive porous media. Cutting-edge spectroscopic techniques will be used to investigate molecular interactions between reactive particles and two types of fluorescent compounds. The first is a fluorescent probe (fluorescein) used to functionalize particles and make them traceable by imaging in microfluidics. The second is an environmentally relevant antibiotic (ofloxacine) to study the reactive properties of h-MPs with emerging contaminants. Advanced microfluidic devices and fluorescence imaging will provide the first spatial resolved images of h-MP concentration at microscale under different flow rates and solution chemistry. RT-MAP will thus lead to key innovations at the interface of environmental chemistry, geosciences and microfluidics, placing the fellow on a strong footing to find an independent research position.