Abstract
Gases, such as nitrogen dioxide, formaldehyde and benzene, are toxic even at very low concentrations. However, so far there are no low-cost sensors available with sufficiently low detection limits and desired response times, which are able to detect them in the ranges relevant for air quality control. In this work, we address both, detection of small gas amounts and fast response times, using epitaxially grown graphene decorated with iron oxide nanoparticles. This hybrid surface is used as a sensing layer to detect formaldehyde and benzene at concentrations of relevance (low parts per billion). The performance enhancement was additionally validated using density functional theory calculations to see the effect of decoration on binding energies between the gas molecules and the sensor surface. Moreover, the time constants can be drastically reduced using a derivative sensor signal readout, allowing the sensor to work at detection limits and sampling rates desired for air quality monitoring applications.
Highlights
Several toxic air pollutants in more than 80% of the urban areas where air pollution is monitored exceed the World Health Organization’s (WHO) recommended safe exposure levels
Benzene and Formaldehyde sensing properties were investigated using epitaxially grown graphene on silicon carbide decorated with Fe3 O4 NPs
density functional theory (DFT) calculations show that the gas molecules are more likely to bind to the down to a single ppb of toxic volatile organic compounds (VOCs) could be quantitatively measured, which makes it very promising decorated sensor surface
Summary
Several toxic air pollutants in more than 80% of the urban areas where air pollution is monitored exceed the World Health Organization’s (WHO) recommended safe exposure levels. Poor air quality has been associated with several negative health aspects ranging from less severe conditions, such as skin and eye irritation, to more acute respiratory problems, cancer, or death. Air quality (AQ) monitoring and control using extremely sensitive sensors are crucial from the viewpoint of preventing further deaths and diseases correlated with toxic air substances. Commercial sensors/instruments available today are either large, expensive, and complex or small but limited by poor selectivity, sensitivity, and a slow sampling rate [3]. There are no commercially available sensors with sufficiently low detection limits to monitor carcinogenic volatile organic compounds (VOCs), such as formaldehyde (CH2 O) and benzene (C6 H6 ), at levels of relevance to human health. Benzene is a genotoxic aromatic compound, especially associated with leukemia
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