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NASA Ames has developed very small-sized oxygen sensors made of a graphene and titanium dioxide (TiO₂) hybrid material. With ultraviolet (UV) illumination, these sensors are capable of detecting oxygen (O₂) gas at room temperature and at ambient pressure. The sensors are able to detect oxygen at concentrations ranging from about 0.2% to about 10% by volume under 365nm UV light, and at concentrations ranging from 0.4% to 20% by volume under short wave 254nm UV light. These sensors have fast response and recovery times and can also be used to detect ozone. This unique room temperature O₂ sensor provides significant advantages in O₂ sensing applications, especially those applications where high operating temperature requirements cannot be met, or would result in inefficient manufacturing processes. Since graphene is not intrinsically responsive to O₂, and TiO₂ is not responsive to oxygen at room temperature, the materials are first synthesized as a hybrid material. The synthesized graphene- TiO₂ hybrid material is then ultrasonicated and then drop-casted onto a series of Interdigitated Electrodes (IDE) to form the sensors. Ultrasonication ensures effective charge transfer at the graphene- TiO₂ interphase. The graphene and the titanium dioxide may be present in the composite material in different ratios to ensure optimal oxygen detection. It is the combination of graphene with TiO2 that yields a semiconducting material capable of O₂ sensing at room-temperature operation.

The technology is a solid state, Carbon Dioxide (CO2) sensor configured for sensitive detection of CO2 having a concentration within the range of about 100 Parts per Million (ppm) and 10,000 ppm in both dry conditions and high humidity conditions (e.g., > 80% relative humidity). The solid state CO2 sensor achieves detection of high concentrations of CO2 without saturation and in both dynamic flow mode and static diffusion mode conditions. The composite sensing material comprises Oxidized Multi-Walled Carbon Nanotubes (O-MWCNT) and a metal oxide, for example O-MWCNT and iron oxide (Fe2O3) nanoparticles. The composite sensing material has an inherent resistance and corresponding conductivity that is chemically modulated as the level of CO2 increases. The CO2 gas molecules absorbed into the carbon nanotube composites cause charge-transfer and changes in the conductive pathway such that the conductivity of the composite sensing material is changed. This change in conductivity provides a sensor response for the CO2 detection. The solid state CO2 sensor is well suited for automated manufacturing using robotics and software controlled operations. The solid state CO2 sensor does not utilize consumable components or materials and does not require calibration as often as conventional CO2 sensors. Since the technology can be easily integrated into existing programmable electronic systems or hardware systems, the calibration of the CO2 sensor can be automated.