A pinboard by
Lena Trotochaud

Postdoctoral researcher, Lawrence Berkeley National Laboratory


Dimethyl methylphosphonate decomposition on CuOx studied with in situ photoelectron spectroscopy

Gas masks are the first line of defense for emergency responders and military personnel in the event of a toxic gas exposure. The filters used today in gas masks contain activated carbon decorated with metal oxide particles. Since the filters were first developed, newer nerve agents, such as sarin and VX, have been used in chemical warfare. The interaction of filter materials with these newer nerve agents is not well understood. For example, we don't know whether these nerve agents simply get stuck and absorbed by the filter, or if they react and break down to form other compounds. If they do break down, we don't know what new compounds they make, which may also be toxic for humans or could poison the filter and cause it to fail. We also don't know how different environments might change the interaction between the filter and the nerve agent. For example, the chemical reaction may be different in a humid forest environment compared to a dry desert. Also, common pollutants in the air that one might encounter in a densely populated city could affect the chemical reactions taking place inside the filter.

We want to make new filtration materials that can provide better protection for people who might be exposed to these toxic gases. Making new and better materials will be much easier if we can first understand how the current materials work and what their weak points are. To do this, we are studying how two of the metal oxides in the filters, copper(II) oxide and molybdenum(VI) oxide, interact with dimethyl methylphosphonate (DMMP). DMMP is a molecule that has similar reactivity to the nerve gas sarin, but is much less toxic so it is safe for us to work with.

We use high energy X-rays to watch how the DMMP molecules break down on the different metal oxide surfaces. The X-rays knock electrons out of the different atoms at our sample surface, and the energy we measure for each electron is like a fingerprint that tells us what type of atom it came from and what other atoms are nearby. We use this information to piece together the possible chemical reactions that might be happening, and we check which reaction pathways are the most likely using computer simulations. Our instrument also lets us add more than one gas at a time, so we can study how the reaction with DMMP changes if we make the environment more humid (by adding water vapor) or more polluted (by adding NOx and hydrocarbons to simulate fuel exhaust).