LAAS/CNRS - LCC/CNRS - Laplace, Toulouse University


E-nose, indoor air quality, multi-gas sensors, nanostructures, metal oxide semiconductors, sensitivity, selectivity, internet of thing (IoT).

Humans spend more than 90% of their time in a closed environment that contains several gaseous pollutants like VOCs (volatile organic compounds). Such gaseous contaminants in the indoor air may cause respiratory problems and chronical diseases. Many others gases such as CO2, CO, and NO2 from urban pollution and poor ventilation systems are also part of indoor air contaminants. Offices, meeting rooms, classrooms and practical workrooms in universities and / or schools may present VOC and /or CO2 levels that exceed the regulatory thresholds. Measuring and monitoring indoor air quality is therefore essential to ensure a better quality life in workspaces. This thesis has been carried out within the framework of the GIS neOCampus (groupement d’intérêt scientifique), led by Université Paul Sabatier UT3 and dedicated to the development of an innovative, connected and sustainable campus for a better quality life. We are interested in the development of miniaturized MOS (metal oxide sensors) gas sensors for the indoor air quality monitoring in offices and classrooms. The objective of this study is to control these pollution levels in order to correct them through measures to ventilate the premises. Making a decision about how to correct air quality is an essential step in the process. As part of this work, we have prepared several prototypes of miniaturized multi-gas sensors (4 sensors) integrated on their electronic card able to detect levels of indoor air pollution. The proximity electronics allows the control and recovery of data from these sensors, and an IOT (internet of things) type communication module based on the WiFi protocol linked to the "Cloud NeoCampus", remotely and wirelessly, generates indoor-air quality signal in real time. This multi-sensor is based on semiconductor sensors based on nanostructured metal oxides (SnO2, WO3, CuO) synthesized at the LCC (laboratoire de chimie de coordination).

Scientific goal

We have developed a new synthetic approach for the nanostructured metal oxides on the sensor platform in order to optimize the performance of the sensitive layer (stability, sensitivity, selectivity). We have studied very efficient associations of n-type and p-type MOS nanostructures based on multilayered implementation on silicon platforms. The gas responses have been measured in laboratories test benches and new measurement protocols (cycled temperature mode versus continuous operation mode) have been defined to selectively detect NO2 or VOCs compounds in air at ppm and sub ppm levels. In addition, PCA (principal components analysis) analyses have been set up to discriminate gas mixtures in test benches.