US Patent 7913541 - Aminocarbon nanotubes for CO2 detection

http://www.freepatentsonline.com/7913541.html

Carbon dioxide detection is important to monitoring air quality and in agricultural applications but CO2 molecules have low reactivity making them difficult to sense. This patent is from Honeywell International and teaches an improved CO2 sensor using functionalized carbon nanotubes in an acoustic wave device. Claim 1 reads: 

1. A carbon dioxide sensor comprising:

an acoustic wave device including a sensing layer deposited onto a surface of a piezoelectric quartz,

said sensing layer comprised of a matrix nanocomposite containing aminocarbon nanotubes having amino groups that reversibly react with carbon dioxide to form carbamates,

wherein said matrix nanocomposite comprises a polymer and at least one of single walled or multi-walled nanotubes present in said matrix nanocomposite between 5 and 15 percent.