The detection of chemical compounds present at ultra-trace levels is a major concern for our societies and applies to a very wide range of applications: protection of citizens against terrorist threats, safety of workers exposed to dangerous substances, monitoring of the environment quality … Among the different existing chemosensory devices those based on the fluorescence are the most sensitive. To further amplify this inherently sensitive method, increasing emphasis in analytical science has been directed towards the development of new materials such as: conjugated polymers. However substantial improvements in the sensitivity of chemical sensors are still necessary to reach the performances required for ultra-trace detections. In this context, the project ambitions are to propose a global approach including innovative technological solutions to improve chemosensors sensitivity and response time. The aim is to demonstrate that the performances of those sensors can be drastically improved (orders of magnitude increase) by controlling the fluorescent materials emission using engineered substrates. Recently, it was reported that the sensitivity of semiconducting luminescent polymers used for TNT detection could be increase by a factor of 30 working near the stimulated emission threshold. In this project, we propose to use optically active nanostructured (ZnO) substrates to further improve the detection threshold of fluorescent polymers based sensors. Fluorescent properties of the sensitive polymer will be combined with the self organisation, refractive and luminescent properties of ZnO nanostructures leading to hybrid device with optimized active surface, luminescent efficiency and lasing threshold.