Investigation of porous nanoparticle structures under illumination for the application as gas sensors

• Applicants: Dr. Nicolae Barsan; Professor Dr.-Ing. Lutz Mädler
• Subject Area: Mechanical Process Engineering ; Physical Chemistry of Solids and Surfaces, Material Characterisation
• Term: from 2019 to 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 419896563

• Final Report Year: 2023

Final Report Abstract

Our long-term vision "Photologic" is the realization of a simple and compact sensor system, which is operated at room temperature and allows the unambiguous detection of different gases in a gas mixture. The concept is based on a stacked multilayer nanoparticle structure under illumination, where individual layers are selectively activated with suitable wavelengths. While the processes in commercial resistive gas sensors operating at temperatures above 200 °C are well studied and optimized, the effects of illumination on porous nanoparticle layers are largely unknown and need to be fundamentally investigated for gas sensing and other (photo)catalytic processes in porous particle structures. In contrast to a heated sensor, where the temperature in the sensor layer is largely homogeneous, the light intensity within an illuminated layer decreases according to the Lambert-Beer law. Thus, the sensor properties depend on the actual position within the layer. The goal of our proposal is to fundamentally understand how this inhomogeneous illumination propagates within the porous particle layer and how this affects the mechanisms of gas detection compared to the known effects in heated sensors. Furthermore, different surface chemistry is expected since activation is not thermal but via light. The most important steps, which complement each other and support each other in the optimization, are the fabrication of suitable sensor layers and the investigation of their properties as gas sensors. Besides morphological characterization and resistivity measurements in a controlled gas atmosphere, advanced methods such as UV-vis spectroscopy, diffuse reflectance infrared spectroscopy (DRIFTS), conductivity measurements and principal component analysis (PCA) are used for this purpose. The acquired knowledge enables a proof-of-concept of our photologic device.

Publications

• Control of Porous Layer Thickness in Thermophoretic Deposition of Nanoparticles. Materials, 14(9), 2395.
  Schalk, Malte; Pokhrel, Suman; Schowalter, Marco; Rosenauer, Andreas & Mädler, Lutz
  
• Investigation on the influence of light on metal oxide gas sensors, Bachelor Thesis 2022, University of Tübingen.
  jan Hanenberg
  
• Proof of Concept for Operando Infrared Spectroscopy Investigation of Light-Excited Metal Oxide-Based Gas Sensors. The Journal of Physical Chemistry Letters, 13(16), 3631-3635.
  Wang, Xiao-Xue; Junker, Benjamin; Ewald, Carolin; Weimar, Udo; Guo, Xin & Barsan, Nicolae
  
• Resistance Measurements and photocatalytic Behaviour of WO3 under UV/Vis irradiation, Master Thesis 2022, University of Tübingen.
  Markus Fröhlich
  
• Multivariate Analysis of Light-Activated SMOX Gas Sensors. ACS Sensors, 9(3), 1584-1591.
  Junker, Benjamin; Kobald, Arne; Ewald, Carolin; Janoschek, Peter; Schalk, Malte; Weimar, Udo; Mädler, Lutz & Bârsan, Nicolae