Nanoporous Lanthanum Oxycarbonate Powders for Enhanced CO₂ Detection - From Nanopowders Elaboration to Microsensor Development

Indoor air quality is a major public health concern. The World Health Organization estimates the number of deaths caused by air pollution at around 4 million per year. In addition, the recent health crisis has highlighted the need for regular air renewal to reduce the spread of viruses. The measurement of carbon dioxide (CO₂) levels in indoor spaces is therefore an interesting indicator of how often the air needs to be renewed.<br/><br/>Among CO₂ sensors, chemoresistors have many advantages such as their good sensitivity and stability [1]. In this type of sensors, the detection phenomenon is based on the change in the electrical resistance as a function of the gas adsorption rate. In the quest to reduce cost and power consumption of these sensors, there is a need in reducing the size of these devices without losing in efficiency. To achieve this objective, new materials are being proposed including the development of inorganic nanoporous powders: since the detection is based on an adsorption phenomenon, increasing the surface area accessible to the gas should allow to improve the detection.<br/><br/>In this presentation, we will focus on lanthanum oxycarbonate (La₂O₂CO₃) for CO₂ detection. This compound has been recently proposed as sensitive layer for resistive microsensors [2]. Here, we propose a new elaboration method based on high-energy ball-milling [3]. We will present this method along with a detailed characterization of the obtained nanopowders in terms of morphology, porosity, structure and reactivity. It will be shown that mesoporous La₂O₂CO₃ nanopowders with tunable pore sizes and crystallographic structures can be synthesized.<br/><br/>The second part will be devoted to microsensor fabrication and performances. Optimisation of the nanopowder deposition method on microsensor interdigitated electrodes will be detailed. The performances of the microsensors in the presence of different concentrations of carbon dioxide (from 400 ppm to 5 000 ppm diluted) will be presented. The influence of the La₂O₂CO₃ porosity and crystallographic structure on microsensor performances will be discussed.<br/><br/><br/><br/>[1] K. Aguir, S. Bernardini, B. Lawson, T. Fiorido, Trends in metal oxide thin films: Synthesis and applications of tin oxide, in: Tin Oxide Materials, Elsevier, 2020: pp. 219–246. .<br/>[2] F. Le Pennec, L. Le Roy, C. Perrin-Pellegrino, M. Bendahan, S. Bernardini, IEEE Sensors, Sydney, Australia, 2021: pp. 1–4.<br/>[3] P.-H. Esposito, C. Leroux, V. Heresanu, T. Neisius, V. Madigou, R. Denoyel, M.-V. Coulet, Materialia. 14 (2020) 100880.<br/><br/><br/>This work received support from the French government under the France 2030 investment plan, as part of the Initiative d'Excellence d'Aix-Marseille Université - A*MIDEX." (AMX-20-IET-015)