Optical and Electronic NOx Sensors for Applications in Mechatronics

Current production and emerging NOx sensors based on optical and
nanomaterials technologies are reviewed. In view of their potential applications in
mechatronics, we compared the performance of: i) Quantum cascade lasers (QCL) based
photoacoustic (PA) systems; ii) gold nanoparticles as catalytically active materials in fieldeffect
transistor (FET) sensors, and iii) functionalized III-V semiconductor based devices.
QCL-based PA sensors for NOx show a detection limit in the sub part-per-million range
and are characterized by high selectivity and compact set-up. Electrochemically synthesized gold-nanoparticle FET sensors are able to monitor NOx in a concentration
range from 50 to 200 parts per million and are suitable for miniaturization. Porphyrinfunctionalized
III-V semiconductor materials can be used for the fabrication of a reliable
NOx sensor platform characterized by high conductivity, corrosion resistance, and strong
surface state coupling.