The decontamination of chemical weapons is a subject of intense political and scientific scrutiny. Copper oxide (CuO) nanoparticles (NP) have proven efficiency in the safe decomposition of mustard gas. The water species confined to the surface of the CuO particles, which stabilise CuO at the nanoscale, play a crucial role in the hydrolysis of mustard gas. Consequently there is a critical need to understand the interactions of this deadly chemical with the hydration layers both chemi- and physisorbed to the CuO NP surface. We propose to investigate by high-resolution INS the interactions of two mustard gas mimetics, namely 1,5-dichloropentane and diethyl sulphide, and the mustard gas decomposition product, 2,2'-thiodiethanol, with the surface of hydrated CuO NPs. This study will aid in the development of efficient catalysts for the safe destruction of chemical weapons.