New generation of gas sensors in civil engineering and architecture

Abstract

Recent developments in nanotechnology led to the paradigm shift in civil engineering. The application of nanotechnology in civil engineering and architecture may enable changes at molecular level to optimize properties and performance of advanced materials in civil infrastructures, such as buildings, bridges, highways at macro-functional level. Recent claims for high-quality sensitive sensors for detection of toxic gases inside buildings are closely connected with quality and safety of life. This dissertation deals with development of highly sensitive and selective gas-sensing device based on carbon nanomaterials (carbon nanotubes and/or nanocrystalline diamond) capable to detect toxic gases inside buildings, offices, schools, undergrounds, etc. Two related subjects are investigated: (i) growth of carbon nanotubes (CNTs) and nanocrystalline diamond (NCD) film by plasma enhanced chemical vapor deposition and ii) their gas sensing potential towards different toxic gases. The CNTs based gas sensor showed almost no response, while the NCD film based gas sensor is modulated by its exposure to different gases. It has been investigated the influence of gases (carbon dioxide, ammonia, humid air and phosgene), the effect of H- and O-termination and/or surface area (as adjusted by the porous layer and/or nanorod morphology) on the surface conductivity of NCD layer. The impedance measurements provided on interdigitated electrodes covered by NCD layer revealed that the sensor sensitivity is strongly dependent on the surface area. The H-terminated porous NCD layer and diamond nanorods has shown an improvement of the sensitivity due to its high surface-to-volume ratio. Also, the gas sensor-based on H-terminated NCD is found to have significant response to oxidizing gas and exhibited a clear selectivity in phosgene detection. Moreover, the model is proposed where the gas sensing mechanism is discussed. In addition, the initial measurement of a prototype of the fully integrated gas sensor-based on H-terminated NCD film is presented. Such types of sensors are pointed out as perspective candidates for civil engineering of 21st century.

Recent developments in nanotechnology led to the paradigm shift in civil engineering. The application of nanotechnology in civil engineering and architecture may enable changes at molecular level to optimize properties and performance of advanced materials in civil infrastructures, such as buildings, bridges, highways at macro-functional level. Recent claims for high-quality sensitive sensors for detection of toxic gases inside buildings are closely connected with quality and safety of life. This dissertation deals with development of highly sensitive and selective gas-sensing device based on carbon nanomaterials (carbon nanotubes and/or nanocrystalline diamond) capable to detect toxic gases inside buildings, offices, schools, undergrounds, etc. Two related subjects are investigated: (i) growth of carbon nanotubes (CNTs) and nanocrystalline diamond (NCD) film by plasma enhanced chemical vapor deposition and ii) their gas sensing potential towards different toxic gases. The CNTs based gas sensor showed almost no response, while the NCD film based gas sensor is modulated by its exposure to different gases. It has been investigated the influence of gases (carbon dioxide, ammonia, humid air and phosgene), the effect of H- and O-termination and/or surface area (as adjusted by the porous layer and/or nanorod morphology) on the surface conductivity of NCD layer. The impedance measurements provided on interdigitated electrodes covered by NCD layer revealed that the sensor sensitivity is strongly dependent on the surface area. The H-terminated porous NCD layer and diamond nanorods has shown an improvement of the sensitivity due to its high surface-to-volume ratio. Also, the gas sensor-based on H-terminated NCD is found to have significant response to oxidizing gas and exhibited a clear selectivity in phosgene detection. Moreover, the model is proposed where the gas sensing mechanism is discussed. In addition, the initial measurement of a prototype of the fully integrated gas sensor-based on H-terminated NCD film is presented. Such types of sensors are pointed out as perspective candidates for civil engineering of 21st century.