Traditional oxygen sensors, including potentiometric and amperometric sensor designs, have significant drawbacks, as metal oxide gas sensors require high temperature operation of about 300 °C, 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.
With ultraviolet (UV) illumination, these sensors are capable of detecting oxygen (O2) gas at room temperature and at ambient pressure. The sensors can detect oxygen at concentrations ranging from about 0.2 percent to about 10 percent by volume under 365nm UV light, and at concentrations ranging from 0.4 percent to 20 percent 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 sensor chip is mass producible and has the potential to scale to thousands or millions of units relatively easily as well as inexpensively via automated wafer-scale manufacturing processes. Applications include oxygen sensor manufacturers; automotive combustion control and emissions control applications; chemical sensing; environmental monitoring; laboratory safety; space suits and helmets, and more.