This project has direct technological benefits to society by enabling the accelerated development of selective, low-power portable gas sensors. This work is purposely structured to disrupt the cycle of trial-and-error materials discovery in gas sensors by developing a fundamental understanding of the sensing mechanisms to enable bottom-up design and engineering of nanomaterials toward specific applications. The knowledge gained from this research provides crucial contributions to the field seeking to: (1) enhance rapid detection of leaks of toxic or flammable gases that could otherwise cause massive environmental damage; (2) enable real-time automated monitoring of food freshness to reduce food waste and aid sustainability, and (3) facilitate deployment of portable sensors capable of rapid screening for biomarkers in exhaled breath that correlate with a range of health conditions and cancers, aiding early detection efforts in populations lacking easy access to advanced health care technology. The two graduate students funded by this project are being developed into future leaders in a U.S. sensor community that is increasingly yielding leadership to international efforts in Japan, South Korea, China, and several groups in Europe. Specifically, they will become experts in nanomaterial electrical measurements and state-of-the-art electronic properties characterization via electron microscopy.
TECHNICAL DETAILS: A recent surge in nanomaterials research has developed many novel methods for synthesizing semiconducting oxides into nanostructures, especially with combinations of materials into a single structure, termed a nano-heterostructure. However, the focus on new synthesis methods has led to a largely trial-and-error approach toward materials discovery for gas sensor applications with little fundamental understanding of the underlying mechanisms. The primary focus of this research is to develop and publish a comprehensive and unifying model for interactions of gases with nano-heterostructures that will provide a framework which enables the rest of the field to more effectively design new structures and ultimately accelerate their implementation into devices. This project seeks fundamental knowledge from proven sensor materials engineered into nano-heterostructures by (1) using state-of-the-art high-resolution electron microscopy techniques to evaluate the electronic structure and properties of these materials on an individual nanoparticle basis; (2) utilizing electrical measurements on single nanowires and clusters of nanowires to separate contributions of interfaces from the bulk and mapping the effects of each oxide constituent as a function of environmental conditions; and (3) building a model of the electronic interactions at the gas-oxide and oxide-oxide interfaces truly representative of nanomaterials and not based on bulk ideal properties. Additionally, an open-access on-line database is being constructed of resistive-type gas sensor published results to aid researchers in the field in identifying trends in materials properties and disseminating important results, as well as helping industries to identify the most promising technologies for a specific application.
