Amine-based polymer coated fiber optic sensors for ppm level CO2 detection in humid conditions

Sensing of CO2 is crucial in many fields spanning from environmental and air quality monitoring to medical, industrial, and agricultural applications. Low-cost fiber optic CO2 sensors with sensitivity levels approaching ppm levels often utilize a pH sensitive indicator dye immobilized in a solid matrix for indirect measurement of CO2. However, these sensors predominantly operate in the visible wavelength range, and humidity can have detrimental effects. We are reporting a fiber optic sensor coated with an amine based hydrophilic polymer blend PEO:PEI that reversibly binds CO2 at room temperature through a weak acid base reaction, leading to modulation in the transmission spectrum of the sensor. Experimental analysis of the sensor reveals the capability of ppm level CO2 sensing in elevated humidity environments throughout a broad range of wavelengths, extending from VIS-NIR. The sensor response at different levels of humidity as well as its stability and repeatability have also been investigated showing promise for low-level CO2 sensing at ppm-level.