2D materials offer a unique platform for sensing with extremely high sensitivity, since even minimal chemical interaction causes noticeable changes in the electronic state. An area where extreme sensitivity is particularly interesting is in the detection of toxic pollutants like nitrogen dioxide and toxic volatile organic compounds (VOCs), like formaldehyde and benzene, in living environments due to the toxicity of some of these compounds upon long-term exposure even to trace concentrations. At the moment there are no commercially available low-cost sensors able to detect specific toxic VOCs at the safe exposure levels recommended in the World Health Organization’s guidelines. However, both societal and market needs are in place to motivate sensor technology development that would allow distributed monitoring of these and other toxic pollutants in living environments: WHO recently released a report stating that 570 000 children under the age of 5 die annually from respiratory infections attributable to indoor and outdoor air pollution. Moreover, bccResearch predicts the global market for portable gas detectors to grow and reach $1.4 billion by 2021. Graphene, in capacity of the first discovered 2D material, has been extensively studied for gas sensing applications, showing good functionality as an extremely sensitive sensor transducer. However, graphene has limitations for this application concerning limited operation temperature, high sensitivity to a large range of gases, and fragility upon surface modification that is commonly done to generate sensitivity to a specific target gas. In this study we report on chemical sensing based on 2D materials on a silicon carbide (SiC) platform. Epitaxial growth of graphene on SiC results in high quality and uniform graphene, which can be utilized to fabricate extremely sensitive gas sensors with good reproducibility. The SiC substrate can also be used for templated growth of atomically thin layers of platinum, which has potential benefits in terms of ability to operate at higher temperature and to serve as a more robust template for functionalization compared to graphene, along with added catalytic properties, while maintaining the sensitivity inherent to 2D materials. These 2D materials are further functionalized with metal- and metal-oxide nanoparticles using a scalable ‘soft’ deposition approach in order to modify the surface chemistry to generate sensitivity to specific target molecules without damaging the 2D sensor transducer. With the 2D materials on SiC sensor platform we have demonstrated detection of nitrogen dioxide, formaldehyde, and benzene in the low or even sub parts per billion regime. This, combined with a smart sensor signal evaluation approach allowing fast response times, could allow real-time monitoring of these toxic pollutant at concentrations of relevance to air quality monitoring.
Journal: TechConnect Briefs
Volume: 2, Materials for Energy, Efficiency and Sustainability: TechConnect Briefs 2018
Published: May 13, 2018
Pages: 101 - 104
Industry sectors: Advanced Materials & Manufacturing | Energy & Sustainability
Topic: Materials for Oil & Gas