Sensors for Environmental Compliance of Diesel Engines

Nitrogen oxides generated from the combustion of fossil fuels contribute to ground level ozone formation and acid rain deposition. To minimize emissions the robust sensor technologies required. Solid-state electrochemical NOx and NH3 sensors evaluated in this study showed significant cross-interference issues. In contrast, the semiconductor nanowires of Cu and Pb Pthtalocyanine and CdS thin films functionalized with Fe and Mn Porphyrines (Ph) exhibited negligible cross-interferences. The computational molecular modeling was utilized to analyze equilibrium structures and binding energies of O2, CO, NO, NH3, and these were shown to control the selectivity. The FePh exhibited the highest selectivity for NO (-190 kJ/mol), while MnPh was most selective to NH3 (-46.7 kJ/mol). The binding energies of gas molecules to the hybrid Ph-CdS system were approximately 30 kJ/mol greater than binding to the Ph alone. Therefore, the semiconductor surface buried under the Ph layer enhanced sensitivity, but it did not alter the selectivity.