Innovative NOx Sensor for Tailpipe Emissions

Diagnostic characterization of tailpipe emission of nitrogen oxides (NOx) is becoming increasingly important as environmental concern and government regulations are requiring the use of complex NOx monitoring and destruction schemes, especially in diesel fueled engines. As these systems become more efficient, tailpipe emissions can retreat to the parts per million (ppm) level, which requires an equally precise NOx sensor to provide feedback for the active destruction system in the presence of the many components of post catalyzer exhaust gas. Equally important to maintaining the NOx destruction efficiency is the ability to provide diagnostic information on an ever shorter timescale to tighten the engine control loop about its most efficient operating point. Finally, reliability, cost and manufacturability are crucial to helping these systems achieve widespread implementation and acceptance. Needed are new robust transducer structures that have high sensitivity, quick responses and precision to go along with cost effective manufacturability and robustness in the face of the extreme environmental conditions present in the exhaust of internal combustion engines. During the past eighteen months, Nanohmics has been developing a gas multiplex detection system that involves deposition and patterning of an array of metal oxide semiconductor nanotraces prepared using the method of NanoImprint Lithography (NIL). For this Phase I program, Nanohmics proposes to develop a high-temperature and environmentally stable sensor array device based on this core detection technology. The NOx Sensor arrayTM device will include a high-temperature ceramic base (e.g. Al2O3, BN) with nanodimension semiconductor transducer structures comprising an array of metal oxide nanotraces that are selectively derivatized with metal/ metal oxide nanoparticle sensitization layers. Numerous instruments have been developed to automate the process of gas analysis. Nanohmics plans to capitalize on semiconductor oxide detection technologies by greatly expanding the ability to perform complex gas analysis by developing a highly sensitive and scalable approach to fabricating the core nanophase semiconducting oxide active layers to monitor NOx and other species present in the tailpipe environment. The method will further include the development of a method that provides a means to batch impart unique specificity to different gas classes within the high temperature environment during a single processing step. In addition to high temperature combustion diagnostics, the ability to perform rapid, highly sensitive and selective detection of a complex chemical profiles is important for applications ranging from acute situational health and safety assessment, industrial process control to suspect/target identification.