Capacitive gas dosimeters with gas adsorbing MFI-type zeolites as sensitive layers for the detection of small amounts of carcinogenic trace gases

• Applicant: Dr.-Ing. Daniela Schönauer-Kamin
• Subject Area: Synthesis and Properties of Functional Materials
• Term: since 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 533084795

Impedimetric gas dosimeters can be described as passive samplers with simultaneous readout of the load-dependent electrical impedance. With the time-continuous detection of smallest exposed doses, they are promising for the hazard assessment of harmful substances. The aim of this project is to clarify whether and how the concept of a capacitive gas dosimeter with gas-adsorbing MFI zeolites is suitable for the precise detection of lowest amounts of carcinogenic trace gases, such as those occurring after GC columns. ZSM-5 zeolites show the potential for dosimeter-like capacitive detection of carcinogenic trace gases and using the model substances acrylonitrile, epichlorohydrin and trichloroethene, the sensor characteristics and mechanism are explored experimentally and by simulations. To analyze the origins of the dosimeter-like sensor effect as well as the required material properties, different in-situ and operando characterization methods of the adsorber-analyte interaction as well as the resulting load-dependent electrical properties of the adsorbers are combined. Systematic variations reveal suitable material compositions, operating parameters, and sensor designs for selective dosimeter-type sensors or high-sensitivity universal dosimeters. In addition, potentials but also limitations of the detection principle for exposure monitoring of carcinogenic trace gases in air are to be evaluated. After reproducing initial results of Cu-ZSM-5 for epichlorohydrin detection with now well-defined trace gas dosage, the aim is to identify promising zeolites for capacitive gas dosimetry of at least one model substance by modifying the framework structure as well as the type and concentration of exchanged metal ions. The project focus will then be on elaborating their sensing characteristics as well as the underlying detection mechanism by correlating the exposure-dependent chemical sorption processes with the electrical properties. For the understanding of the sensor characteristics and the determination of suitable operation and regeneration strategies, simulations of the diffusion-limited gas sorption at low gas velocities, the remaining adsorption capacity as well as the influence of the operation parameters on the one hand and combined operando-IS-DRIFTS of the sensitive layers during analyte adsorption and desorption on the other hand contribute to the elucidation of the chemical and electrical processes. From this, operating strategies for selective or non-selective detection are derived, i.e., beneficial gas flow conditions, gas compositions, and operating temperatures for the detection as well as regeneration phases. Finally, a first functional proof for selective trace gas detection as a gas sensor or for non-selective detection of gas chromatographically separated mixtures of the trace gases is provided.

• DFG Programme: Research Grants