Detecting compounds in airborne particles using ion exchange

A sensor to detect solid particles of a target compound, comprising:

• a support substrate;
• an adsorption layer comprising a medium formed of a first porous structured material functionalized with basic functional groups, wherein said target compound is a salt or a free base compound, wherein the salt is converted by the basic functional groups to form a converted free base of the salt, wherein the first porous structured material is a network of first organic nanofibers, wherein the first organic nanofibers are assembled from stacked molecules selected from a group consisting of:
• 3,4,9,10-perylene-tetracarboxylic diimide, 3,4,9,10-perylene-tetracarboxylic dianhydride, perylene 3,4,9,10-tetracarboxyl-3,4-anhydride-9,10-imide, an indolocarbazole derivative, and an oligomer made up of 3 to 9 carbazole derivative monomers, wherein at least a portion of the stacked molecules are further functionalized with the basic functional groups;
• a sensing layer oriented between the support substrate and the adsorption layer, the sensing layer comprising a second porous structured material functionalized to detect the converted free base or the free base compound by a change in conductivity, wherein the first porous structured material comprises a different material than the second porous structured material;
• and
• an electrode pair in contact with the sensing layer and separated by the sensing layer.