Printable sensors for Nitrogen dioxide and Ammonia sensing at room temperature

Abstract

© 2019 IEEE. Several studies have found a link between poor air quality and incidences of respiratory and cardiovascular diseases [1]-[6]. A World Health Organisation (WHO) report put the number of deaths caused by household air pollution at 4.3 million in 2012 [7]. Attempts at reducing poor air quality-related mortality have seen specification of safe human exposure limits for daily, and yearly average by government agencies such as Environmental Protection Agency (EPA) and World Health Organisation (WHO). Vehicle exhausts are key sources of Nitrogen dioxide, a key pollutant of ambient air. Other sources of NO2 includes fossil fuels and industrial engines. [8] NO2 is very toxic and causes acid rain. [9] Hence the need for sensitive, but more importantly selective sensors to monitor the levels of NO2 in breathable air. It is also desired that these sensors be able to provide fast response at room temperature. Exhaled breath testing has been known to be a quick, safe and non-intrusive approach to early detection of declining health due to the presence of biomarkers corresponding to underlying diseases in them. Volatile Organic Compounds (VOCs) and ammonia are some of these markers.[10] Ammonia is passed out in urine and the concentrations of ammonia in exhaled breath only increases as health declines and reaches 1ppm in the event of kidney failure[11] Chemiresistors are good candidates for these sensitive and selective sensors and research is ongoing to develop new material composites with the desired properties for this purpose. In this work we present chemiresistors based on two new material composites with potential to for applications in ambient air quality monitoring and breath analysis at room temperature. These composites can be printed or drop-casted on interdigitated electrodes on flexible substrates such as Polyimide (PI) and Polyethylene (PET). The NO2 sensor, with Graphene-Carboxymethylcellulose (CMC) sodium salt active material composite shows sensitivity and selectivity to NO2 at room temperature while the NH3 sensor, based on a Polyaniline - Zinc Oxide composite shows sensitivity at room temperature