The by-product of the uranium enrichment process, the depleted uranium, has been applied as armour-piercing ammunition in several international military conflicts. Depleted uranium is used because of its high density, hardness, and pyrophoric properties. The testing and use of such ammunitions have led to the release of depleted uranium into the environment at several locations worldwide. So, the issue of the possible presence of depleted uranium in the environment has recently attracted considerable public interest. The use of depleted uranium in non-fission nuclear weapons results in the addition of toxic 238U to the natural uranium in the environment, producing environmental damage even if this isotope is not radioactive.

In this work, optical fiber sensors specific for uranium detection in water are presented to demonstrate the capability of the sensing approach for the determination of uranyl in water solution in the ppb range. In particular, the optical fiber sensor has been obtained by combining the surface at which the plasmonic resonance (SPR) takes place with a specific receptor layer for uranium. The resonant surface employed in the sensor here proposed is a multilayer one, with a characteristic D-shaped profile obtained simply by erasing a multimode POF.

The proposed sensing method is attractive because, in principle, it can be applied directly in the field, giving an analytical response in a fast and not too expensive way.

Moreover, it is a marker-free sensing device, and, as such, it can be applied to different metal ions, even not electroactive as in the case of electrochemical transduction, provided that a proper receptor is fixed at the SPR interface.