Combined optical and electronic paper-nose for detection of volatile gases.

In this work, a paper-based optoelectronic sensor (paper-nose) is presented for sensing volatile gases in air. The proposed optoelectronic sensor is a combination of both colorimetric (optical) and chemiresistive (electronic) sensor arrays in order to improve the selectivity of the paper-nose in the complex air background. The optical sensors are based on chemoresponsive dyes, namely Reichardt's dye (2,6-diphenyl-4-(2,4,6-triphenyl-1-pyridinio)phenolate), bromocresol purple, methyl red, bromothymol blue, brilliant yellow and manganese tetraphenylporphyrin (Mn-TPP). The chemiresistive sensors are based on nanomaterials, such as carbon nanotubes (CNT), PEDOT:PSS, graphite, and an ionic liquid, 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (EMI TFSI). Sensor is fabricated through direct handwriting of sensing materials using a pen on paper without the need of expensive cleanroom facilities. The optoelectronic sensor is tested in ambient air with different volatile gases such as methanol, ammonia, toluene, acetone and ethanol and their mixtures of varying concentrations. The detected electrical and optical responses together form a unique signature for each volatile gas and its mixture. Support-vector machine (SVM) is applied for target classification and detection. From the SVM result, it is found that better discriminative power is achieved by combining optical and electrical responses.