Nitrogen dioxide (NO2) is a major component of the outdoor air pollution. Microsensors are interesting devices to check and to monitor this toxic oxidizing gas. Recent advances in flexible electronics, a complementary technology to the conventional rigid silicon technology, have motivated research efforts. Flexible substrates enable new applications such as wearable sensors, electronics on skin/organs as well as a possible reducing cost during the fabrication process. However, flexible substrates required low working temperature to avoid thermal degradation. This work aims to prove the possibility to use zinc oxide nanocrystals (ZnO NCs) post-annealed at low temperature as a sensitive material to detect NO 2 at low working temperature. Thus, our study has been performed on rigid substrates to check first the sensitive layer behaviour depending on the temperature. Then, to be able to reduce the working temperature, a continuous UltraViolet illumination has been used. We propose a NO 2 detection at room temperature by ZnO NCs deposited on rigid substrates by spin coating from colloidal solutions as sensitive layers for air quality monitoring.