Engineering and Architecture
Rosa Maria Sole Cartañá
Xavier Mateos Ferré
Universitat Rovira i Virgili
Nanoscience, Materials and Chemical Engineering
Environmental sensing in smart cities. An integrated photonic device applied to NO2 gas traces.
Nitrogen oxides, NOx, in particular the concentration of NO2 in the atmosphere is of great concern because its exposure might produce a variety of toxicological responses in humans and animals. Local (cities) areas with industrial poles in the neighbourhood such as Tarragona on the Mediterranean coast of Spain might experience high peak NO2 concentrations (ppm level) depending on temperature, humidity, wind and emissions of NO2 by anthropogenic activities (vehicles, industry or biomass burning).
At present, there are several approaches to measure NO2 with unsophisticated optical systems and little maintenance but giving more information on the vertical distribution of gases than in-situ point source measurements. Satellites cover large areas but have the disadvantage of providing daily measurement not in real-time. Complex algorithms for data processing are also developed and used in such systems.
The idea of the present project is to develop a sensor by using either a broadband visible light source (cheap lamp) or a visible laser operating at a specific wavelength coupled into a low-loss channel waveguide (enhanced light confinement) so that the strong evanescent field (enhanced sensitivity) interacts selectively by the resonant absorption of NO2. It shows resonant absorption in the 300-790 nm range centred at 400 nm. To avoid overlapping with the resonant absorption of other molecules, a polymeric membrane selectively permeable to NO2 is going to be deposited on top of the optical waveguide.
The resulting changes in the transmission of the visible light source at the output of the channel waveguide after the interaction with NO2 are going to be used for sensing.
This novel approach is believed to be a promising tool in NO2 monitoring implemented in distributed sensors to have real-time information of the pollutant. A telecom system gathers and sends all the data to the civilian protection system to start the security protocol in case of emergency.
This work is to be carried out in a multidisciplinary team.
1-Fabrication and characterization of the channel waveguide. For visible channel waveguide lasers, the crystal growth of such materials doped with rare-earth active ions as well as its functionalization will be carried out. This material is Silicon-compatible for coupling on-chip for mass production. The micro-structuring of the channel waveguide will be carried out by diamond dicing.
2-Fabrication, characterization and assembling of the polymeric membrane permeable to NO2.
3- Finite Element simulations of the propagating laser mode to optimize the channel waveguide dimensions, suitable refractive index contrast and evanescent field distribution.
4- Application of the gas sensor to NO2 in the atmosphere of Tarragona. Optimization.
5- Eventually, prototyping of the NO2-sensor for distribution over the city for real-time in-situ measurement. Electronic amplification of the signal will enhance the signal-to-noise ratio.
37.5 hours a week
|This project has received funding from the European Union's Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No. 713679|