Scientists have put the x-ray spotlight on composite materials in respirators used by the military, police, and first responders. The results provide reassuring news about the effectiveness of current filters and provide fundamental information that could lead to more advanced gas masks as well as protective gear for civilian applications.
To trap toxins, gas mask filters use activated carbon, augmented with metal oxides to help break the toxins down. The researchers targeted two metal oxides—molybdenum oxide and copper oxide—that are key working components. The goal was to better understand the molecular interactions that occur as various gases are adsorbed by the filter materials, and the environmental conditions—air pollution, diesel fuel exhaust, water—that could alter performance and shelf life.
At ALS Beamline 11.0.2, the researchers used ambient-pressure x-ray photoelectron spectroscopy (AP-XPS) to precisely determine the chemical composition of the top few atomic layers of the oxides in great detail. Small organophosphorus toxin molecules were simulated by dimethyl methylphosphonate (DMMP), an established proxy for sarin with similar functional groups but significantly lower toxicity.
The researchers tested the effects of water, octane, and nitrogen oxides, and none of these exposures decreased the ability of the metal oxides to bind to and break down the DMMP. They did find subtle differences that are interesting from a fundamental point of view but that do not affect the bulk performance. The project is now entering its next phase, in which different composite materials will be tested to determine whether they might perform better than existing filters.
Work performed at ALS Beamline 11.0.2.
L. Trotochaud, R. Tsyshevsky, S. Holdren, K. Fears, A.R. Head , Y. Yu, O. Karslıoğlu, S. Pletincx, B. Eichhorn, J. Owrutsky, J. Long, M. Zachariah, M.M. Kuklja, and H. Bluhm, “Spectroscopic and Computational Investigation of Room-Temperature Decomposition of a Chemical Warfare Agent Simulant on Polycrystalline Cupric Oxide,” Chem. Mater. 29, 7483 (2017), doi: 10.1021/acs.chemmater.7b02489.
Excerpted from the Berkeley Lab news release, “Studying Gas Mask Filters So People Can Breathe Easier.”