A Low-cost Handheld Sulfur Dioxide Tester with a Hybrid Nanomaterials-Based Sensor Chip

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).