Highly efficient carbon-nanostructures-based gas sensors for biomedical and other applications
Luis Antonio Panes Ruiz
Master Thesis, TU Dresden, August 2015
In recent years, gas sensors have been a hot topic of research due to their wide range of applications going from environmental studies to medical diagnosis. Carbon based nanomaterials have emerged as a promising class of materials allowing to reach high sensitive, simple and low cost sensors due to outstanding nanoscale characteristics. Therefore, more investigation is needed in order to improve existing gas sensing technologies.
Gas sensing devices based on semiconducting carbon nanotubes (SC-CNTs), pristine carbon nanotubes (P-CNTs), boron doped carbon nanotubes (B-CNTs), nitrogen doped carbon nanotubes (N-CNTs) and reduced graphene oxide (rGO) were fabricated, characterized and exposed to different concentrations of ammonia in order to compare their performance. Moreover, the recovery properties after 3 weeks in controlled conditions of temperature and humidity were also investigated.
Electrical and SEM characterization were performed on all devices and it was discovered that the amount and quality of distribution of nanomaterial deposited and the electric and sensing properties of the gas sensors are closely related. In order to compare the sensitivity to ammonia of the different carbon nanomaterial- based sensors, the devices were exposed to 1.5, 2.5, 5, 10 and 20 ppm of ammonia. SC-CNTs based gas sensors achieved the best results to all ammonia concentrations and the lowest recovery after 3 weeks in storage followed by N- CNTs, P-CNTS and finally B-CNTs. In addition, quite similar results in sensing response to all ammonia concentrations were observed for P-CNTs, B-CNTs and N-CNTs suggesting that ammonia molecules interact mainly with carbon atoms of CNTs, rather than with dopant atoms.