Room temperature oxygen sensors

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. Oxygen (O₂) sensors are used in a wide array of applications, including electronic fuel injection and emissions control in the automotive industry, for monitoring oxygen levels in controlled environments, such as in space craft or space suits, for oxygen monitoring in medical and pharmaceutical applications, and many more. Traditional oxygen sensors, including potentiometric and amperometric sensor designs, have significant drawbacks, as metal oxide gas sensors require high temperature operation of about 300C, and suffer from high power consumption. NASA Ames Research Center has developed novel oxygen sensors made of a hybrid material comprising graphene and titanium dioxide (TiO₂) that is capable of detecting O₂ gas at room temperature and ambient pressure. The sensors have fast response and recovery times and can also be used to detect ozone. The sensors can be integrated into wearable-sized Internet of Things (IoT) devices.