Molecularly Imprinted Polymers for VOC sensing: chemoresistive and optical sensors

Nowadays, Volatile Organic Compounds in indoor air are considered as a big pollution issue. VOC's originate from furniture, paintings, varnishes, wood protection, construction materials, etc. In particular, formaldehyde is one of the priority pollutants because of its carcinogenic character and its omnipresence in our close environment. Methods based on air sample collection and lab measurements are the most used methods today but these methods, although accurate and reliable, are expensive, not real time and cause statistics issues. Devices based on chemical sensors are a good solution as these systems can be very sensitive, low cost, real time and easily integrated in common electronics to build portable systems. This paper will present formaldehyde sensors based on molecularly imprinted polymers.
Molecularly imprinted polymers (MIP) are polymers synthesized incorporating the target molecule we want to detect as a template. Functional monomers form a complex around the template and are linked afterwards to form a polymer constituted of a series of 'cages' trapping the template. Afterwards, the template is removed, leaving a cavity imprinted in the polymer matrix that allows the polymer to selectively recognize the target molecule. These elements are cheap, easy to synthesize and can be adapted to any kind of surface. When using conducting polymers for building MIP's, the adsorption of the template can modify their optical or electrical properties. We showed that it was possible to use these materials for building chemoresistive or optical fiber sensors for formaldehyde working at room temperature with a good selectivity and fair sensitivity.