Sensitization of lanthanide-based phosphors by transition metals for high-brightness tunable thermometers (SensiTherm)

• Applicant: Professor Dr.-Ing. Frank Beyrau, since 3/2022
• Subject Area: Technical Thermodynamics ; Synthesis and Properties of Functional Materials
• Term: from 2019 to 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 426574030

The main objective of this project is to enhance the photoluminescence properties of lanthanide-based optical thermometers via sensitization by transition metal ions. Taking advantage of the significantly higher absorption cross section of transition metal ions, the emission intensity of the lanthanide ions can be significantly enhanced, which will increase the signal levels offered by the thermometers. In addition, because the energy transfer from sensitizer to activator is strongly temperature-dependent, the sensitization of lanthanide emissions through transition metal ions will open a new path to enhance the temperature sensitivity of co-doped luminescent thermometers. To achieve this goal a detailed understanding of the sensitization process of lanthanides by transition metal ions in microcrystalline particles will be developed. The influence of material parameters such as local crystal field, phonon energy, dopant concentration, and energy level difference between excited states of activator and sensitizer on the temperature-dependent sensitization process enables the control and intentional design of luminescent thermometers with high emission intensity and high sensitivity to temperature changes. To investigate the energy transfer, microcrystalline samples will be synthesized in Wroclaw, and the spectroscopic properties will be investigated in Magdeburg using dispersed particle methods and quantum yield measurements to unambiguously quantify the absorption, energy transfer and emission processes. Host, sensitizer and activator dependent parameters will be investigated by systematically probing a range of combinations. The absorption cross section, the energy transfer rate, as well as radiative and non-radiative de-excitation rates will be measured, which will also serve as a comparison for theoretical models developed in Wroclaw. Those rates will also be measured over a range of dopant concentrations (sensitizer and activator), excitation power densities and temperatures to investigate the effect of each parameter on the sensitization process. The proposed project brings together the expertise of Wroclaw in the synthesis, structural characterisation and theory of transition metal and lanthanide doped compounds, with that of Magdeburg in advanced spectroscopic techniques based on probing the luminescence of dispersed particles in temperature-controlled fluid flow systems. Implementation of this project will provide an extensive characterization of energy transfer processes between transition metals and lanthanides, for both fundamental understanding as well as to provide luminescence thermometers with enhanced characteristics (more suitable excitation window, higher emission intensity, higher temperature sensitivity) which will greatly contribute to the progress of many fields of science for which temperature is a property of foremost importance.

• DFG Programme: Research Grants
• International Connection: Poland
• Partner Organisation: Narodowe Centrum Nauki (NCN)
• Cooperation Partner: Privatdozent Lukasz Marciniak, Ph.D.
• Ehemaliger Antragsteller: Professor Dr. Benoît Fond, until 3/2022