Optical air sensors center around the detection of some form of light created by a chemical process, in order to identify or measure amounts of individual molecules.
One of the primary methods of optical air sensing involves taking a sol-gel, which is made by taking a sol, a liquid with stable colloidal particles, and mixing it with a gel, which is a three dimensional continuous network encompassing a liquid.
[2] This method consists of dissolving some solid into a solvent and then maintaining a basic pH as the mixture is refluxed to condense and produce a gel.
[5] The testing procedure is incredibly simple since all you have to do is expose the sol-gel to the air and monitor the color change.
These monoliths operate in a similar method to the thin layer sol-gels in that they trap some analyte and show a color change.
[6] As the vapor flows into the system it is hit with a high intensity light so that different organic dyes located in different small holes, or micropores, emit a certain wavelength and varied intensity of light based on what vapor compound they are in contact with.