SBIR-STTR Award

This SBIR Phase I project aims to develop an affordable handheld tester to meet the need for real-time, onsite detection of sulfur dioxide (SO2) in the air. The handheld tester integrates a novel micro-sized sensor chip with a portable digital meter for direct readout of testing results. The sensor chip is built upon a sensing platform with graphene-tin oxide nanoparticle hybrids as the sensing material, which has been proven to have outstanding sensing properties. SO2 is a toxic gas and a primary air pollutant, which can cause various adverse effects on human health and the environment.Monitoring of ambient SO2 is of great interest for public and occupational health, environmental protection, and industrial emission control. UV fluorescence analyzers can detect SO2 at sub-ppb levels and are routinely used in national regulatory monitoring networks. But they are expensive and are laboratory-based. Portable and low-cost SO2 sensing devices are desired for supplemental ambient monitoring needs, such as short-term measurements at multiple locations to understand the spatial variations of SO2 concentrations, or temporary monitoring in response to a resident/worker concern. Electrochemical SO2 detectors are portable and less expensive, but their detection range is insufficient to meet the EPA standards for monitoring ambient SO2. NanoAffix Science LLC (NAFX) proposes to address the above unmet need and the niche market product gap (estimated market size: $30M) by empowering potential customers (e.g., environmental protection agencies, public health departments, and occupational health and safety specialists) with a low-cost, easy-to-use, and accurate handheld tester for rapid detection of SO2 in the air, right from wherever they need. The specific research aims of this Phase I project are to: (1) Improve the sensor sensitivity to achieve the target of 1 ppb detection limit; (2) Improve the sensor selectivity toward SO2 and minimize responses to interfering gases; (3) Characterize the SO2 sensor under practical conditions and improve its long-term stability; and (4) Develop an efficient sensor calibration procedure and integrate it into the handheld meter. The potential outcome of the proposed Phase I project is a prototype handheld SO2 tester, which meets the requirements for the portable monitoring of SO2 in the air. The NAFX tester will feature a sensitivity down to 1 ppb, excellent selectivity toward SO2, response and recovery times on the order of seconds, and a low cost (projected price: $60/unit).

This SBIR Phase II project aims to further advance the progress made during phase I toward the development of a portable handheld detector for real-time onsite detection of sulfur dioxide (SO2). SO2 is an air pollutant, which can adversely affect respiratory and cardiovascular health in humans. Onsite monitoring of SO2 would enable real-time detection of chronic and acute exposure to this toxic gas and lead to the mitigation of health problems. Currently, large stationary expensive UV-fluorescence analyzer equipment can be used to monitor SO2 levels in the ppb range, but this makes it difficult to monitor levels of SO2 at many different locations. Therefore, there is a need for a portable and inexpensive SO2 detector to expand the areas where monitoring is possible. This would assist in limiting exposure to this toxic gas. Electrochemical SO2 detectors meet some of these requirements but have poor sensitivity and insufficient detection concentration ranges to meet EPA standards for monitoring SO2.NanoAffix has expertise related to developing graphene-based sensors for monitoring water and air quality. The sensors for SO2 detection utilize graphene coated with mixed metal oxide nanoparticles which are being optimized for sensitivity and selectivity toward measuring SO2 onsite. This innovation combines the excellent electronic properties of graphene with the selectivity of novel mixed oxide nanoparticles for SO2 detection. These sensors function as chemiresistors and are capable of portable and inexpensive detection of SO2 in the necessary single digit ppb concentration range under ambient conditions. In phase I, NanoAffix demonstrated sensitivity down to 2 ppb SO2 under ambient temperature and pressure with these graphene-based sensors. NanoAffix successfully created a calibration curve in the range of 2 ppb to 40 ppb SO2 for detecting unknown concentrations of SO2. The gas sensor market size is estimated to be $4.7 billion by 2025 according to ‘Global Gas Sensors, Detectors, and Analyzers Market Report 2019-2025’ by Frost and Sullivan. At the conclusion of this phase II project, NanoAffix intends to have a commercially viable portable tester with a proprietary calibration algorithm and innovative sensors coated with novel and proprietary mixed metal oxide nanoparticle probes for detecting SO2.