PhD defense Robin Geitenbeek

Over the past decades, scientific progress has resulted in the ability to produce, process and manipulate materials on smaller length scales, all the way to the nanometer (10^-9 m) regime. To manipulate processes on smaller length scales, it is also important to monitor relevant parameters (e.g. pressure or temperature) on this nanometer length scale. It is obvious that classical thermometers no longer function on these small length scales and new methods for thermometry need to be developed.

In this PhD project, luminescence thermometry (using light to monitor temperature) has been investigated and luminescent (nano)particles are characterized and tested for applicability in a variety of systems. Initially, different sets of luminescent nanoparticles have been developed and the temperature-dependent behavior of the luminescence has been characterized extensively.

The luminescent nanoparticles have been used to perform temperature measurements in a catalytic reactor. Although the spatial resolution was still limited (ca. 1 mm) the experiments showed that luminescence thermometry can be used to properly determine the temperature inside a catalytic reactor. The spatial resolution was afterward increased by combining the spectroscopy measurements with microscopy, allowing for temperature measurements in different microreactors with a spatial resolution of several micrometers (10^-6 m).

This PhD project has yielded thermally and chemically stable materials for luminescence thermometry. By monitoring the luminescence output temperature could be determined with a relative low spatial resolution which was greatly enhanced by combination with (confocal) microscopy. Using these systems temperature mapping was performed in microreactors used in operando STXM measurements and microfluidics.

After showcasing the materials for applications, the potential of the temperature probes was further enhanced by incorporation in multifunctional materials. By combing the synthesized nanoparticles with gold nanoparticles, luminescence thermometry is combined with locally enhanced Raman spectroscopy, which allowed for monitoring of both surface species and surface temperature of single catalyst particles.  

Congratulations on this achievement!

Source: website Utrecht University