This work involves development of aerogel to be used as a passive absorption media — effectively a concentrator of trace organics — that can be detected by optical techniques. Such a trace organic detection scheme is very different from all other current techniques, and has the potential to significantly enhance the sensitivity of detection of volatile species. The aerogel concentrator provides an integrated measurement over long periods of time (months, years), as opposed to mass spectroscopy, which tests at a given moment.
The number of hydroxyl groups on the intrinsic aerogel surface limits the total amount of chemical species that can be chemisorbed. This is the maximum capacity of the aerogel concentrator. Knowing that property, one can tune the density and/or intrinsic surface area to match the needs of a planetary mission.
The chemical reaction of chlorosilanes with hydroxyl groups was used as a marker. A method was devised to saturate the samples with chlorosilanes, which were detected by a simple weight measurement on a sensitive microbalance. The type of cholorosilanes was then varied with different mass of the radicals, and it was demonstrated that hydroxyl bond concentration remained constant for an aerogel sample with a given density.
The creative element of this research is the use of a simple instrument (microbalance) for an effective and accurate evaluation of the bond density in a material with exceptionally large surface area. The concentration of volatiles in such a scheme does not require electrical power, there are no complex mechanisms, and most importantly, aerogel is already used as a thermal insulator. A dual use may enable significant mission enhancement.
This work is a critical step toward developing aerogel concentrator media for detectors for trace volatiles that can be used in various planetary missions. The adsorption capacity of the enormous aerogel surface can facilitate better sensitivity than the current state of the art.