| Popis: |
Carbon dioxide is a colourless and odourless gas and detection of carbon dioxide is critical to maintaining the quality of breathable air in the atmosphere. The current concentration of carbon dioxide in the atmosphere is 400 ppm and this concentration has increased manifold in the past 50 years or so leading to global warming and other climate phenomena. Exposure to 2000 – 5000 ppm of carbon dioxide causes poor concentration, increased heart rate and nausea and when the concentration is > 5000 ppm, oxygen deficiency may occur. This creates an urgent need to develop sensors suitable to carbon dioxide detection. Semiconducting metal oxides such as SnO2 (n-type), CuO (p-type), ZnO (n-type) WO3 (n-type) etc. have long been considered for detecting reducing gases such as carbon monoxide, hydrogen and methane. However, such metal oxides perform poorly when it comes to carbon dioxide detection. Thus, we have proposed the formation of p-n junctions with n-type metal oxide (ZnO) and p-type perovskite (LaFe0.8Co0.2O3) that has been shown previously to aid carbon dioxide sensing. LaFe0.8Co0.2O3 (LFCO) – ZnO composite thin films have been synthesized using wet chemical synthesis in which the mol % of LFCO has been varied. The role of both homo and heterojunctions in carbon dioxide sensing can be elucidated from this configuration. This configuration is cross-sensitive to carbon monoxide and mathematical analyses has been performed to differentiate it from carbon dioxide. LFCO – ZnO thin films with a single p-n junction has also been synthesized and it has been found that this configuration is much more selective to carbon dioxide than the previous one. In addition to this, the role of LFCO – ZnO multi-layered thin films has also been explored with respect to carbon dioxide sensing. |
