Room temperature oxygen sensors
Inventors
Assignees
National Aeronautics and Space Administration NASA
Publication Number
US-11796457-B1
Publication Date
2023-10-24
Expiration Date
2040-12-30
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Abstract
Highly accurate oxygen sensors made of graphene and titanium dioxide hybrid material are provided. With UV illumination, the disclosed sensors are capable of detecting O2 gas at room temperature and ambient pressure. The sensors are able to detect oxygen at concentrations ranging from about 0.2% to about 10% by volume under 365 nm UV light, and at concentrations ranging from 0.4% to 20% by volume under short wave UV light. The disclosed sensors have fast response and recovery times and can also be used to detect ozone.
Core Innovation
The invention provides highly accurate oxygen sensors made of a graphene and titanium dioxide (TiO2) hybrid material that operates at room temperature and ambient pressure. These sensors utilize UV illumination to detect oxygen gas across varying concentration ranges and also detect ozone. The sensors exhibit fast response and recovery times and can be integrated into artificial intelligence devices, offering a low-energy alternative to traditional oxygen sensors.
The problem addressed is that traditional oxygen sensors require high operating temperatures (around 300° C.) and high power consumption, limiting their use in many applications. Graphene alone is not inherently sensitive to oxygen gas, and titanium dioxide requires high temperatures to function effectively as a gas sensor. Additionally, existing graphene-TiO2 hybrid fabrication methods are expensive and unsuitable for mass production, necessitating a cost-effective, scalable solution that allows room-temperature oxygen sensing.
The invention solves these challenges by synthesizing graphene-TiO2 hybrid materials via a solution-phase process with ultrasonication to ensure strong physisorption and effective charge transfer. The dispersion is drop-casted onto interdigitated electrodes on sensor chips, enabling easy, cost-effective, and scalable production suitable for wafer fabrication. The sensors demonstrate changes in resistance upon exposure to oxygen gas under UV light, providing a reliable, small-footprint oxygen sensor functional at room temperature and ambient pressure.
Claims Coverage
The patent includes one independent claim focused on a method of detecting an analyte in a gaseous sample using a graphene-TiO2 hybrid sensor under UV irradiation. The main inventive features relate to the sensor composition, UV-based detection method, resistance measurement, and analyte concentration determination.
Use of graphene-TiO2 hybrid sensors for gas detection at room temperature
The method involves exposing a gas sensor comprising titanium oxide nanoparticles attached to graphene nanoplatelets to a gaseous sample and UV irradiation at room temperature to detect an analyte based on changes in sensor resistance.
Determination of analyte concentration using logarithmic relationship
The method includes calculating the concentration of the analyte from the measured resistance change using the logarithmic formula S=0.0107 ln C+0.0321, where S is the relative change in resistance and C is the analyte concentration.
Purging sensor with nitrogen to reset baseline resistance
After each UV exposure, the sensor is purged with nitrogen for about 1 to 20 minutes to return its resistance to baseline, ensuring reliable repeated measurements.
Detection under different UV wavelengths and corresponding sensor response
The sensor operates under long wave UV light (365 nm) where resistance increases with oxygen concentration (0.06% to 15% v/v), and under short wave UV light (254 nm) where resistance decreases with oxygen and/or ozone concentration (0.4% to 21.5% v/v). Also includes using LEDs as UV sources.
Integration and applicability of the sensor
The method contemplates integrating the sensor into artificial intelligence devices and using it for various gaseous samples including those from spacecraft, spacesuits, food processing, steel or cement production, ink jet, solution casting, spin-coating, laboratory, electronic fuel injection or emission control, medical, and pharmaceutical applications.
The claims cover a method for gas detection using a graphene-TiO2 sensor that exhibits resistance changes under UV irradiation at room temperature, enabling precise analyte (oxygen and ozone) detection over defined concentration ranges with a nitrogen purging step to maintain sensor baseline. The method emphasizes cost-effective, scalable sensor composition and UV-based detection applicable to diverse industrial and medical applications.
Stated Advantages
Low-cost and easily scalable production method suitable for mass fabrication.
Room temperature and ambient pressure operation reduces power consumption compared to traditional high-temperature sensors.
Small footprint allows integration into wearable-size Internet of Things (IoT) and artificial intelligence devices.
Wide detection range for oxygen concentrations with high precision and low detection limits.
Fast response and recovery times enabling efficient and reliable gas sensing.
Capability to detect both oxygen and ozone by alternating UV light wavelengths.
Documented Applications
Environmental monitoring, including spacecraft and spacesuit air control.
Medical applications for oxygen monitoring.
Food processing industries.
Steel and cement production processes.
Ink-jet printing and solution casting.
Spin-coating operations.
Laboratory safety monitoring.
Electronic fuel injection and emission control systems.
Pharmaceutical applications.
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