My ambition is to measure, understand, and predict the flow of energy, charge, and mass in (nanostructured) materials. Such flows underlie the working mechanism of various types of materials for various types of applications. We develop and use experimental methods based on time-resolved optical microscopy and spectroscopy, in­cluding at the single-molecule level, complemented with in-depth modeling. This will contribute to the development of advanced (nano)materials with rationally designed properties.


A few examples of recent research methods and topics:

(1) Energy-transfer pathways in rare-earth-doped materials. Many rare-earth elements can absorb and emit visible light. As such, they are the active component of many sensors, lasers, displays, and other optical devices. The active material often contains two or more types of rare-earth elements with each a specific role: one element absorbs light, then the energy is transfered to another element via one or more hops, and the other element emits light. We investigate these energy-transfer pathways, experimentally and by constructing mathematical models.


(2) Properties of individual nanocrystals. Nanocrystals are typically made in large batches using chemical synthesis. Each nanocrystal in the batch is slightly different in terms of size, shape, and composition. This leads to variations in properties, which in turn affects the overall performance of the ensemble of nanocrystals. To guide the design and optimization of nanocrystals for various applications, we need to understand these variations directly. We perform experiments on individual nanocrystals, precisely recording for example the timing and wavelength of individual photons emitted. Such experiments are challenging, because the signal from an individual nanocrystal is very weak.


(3) Diffusion of molecules. Heterogeneous catalysts reduce the energy footprint of the production of chemicals and materials by accelerating chemical reactions. The catalysts typically have a complex pore network through which reactants and product molecules travel to and from active sites. The lay-out is analogous to the street map of a city, constituting a combination of wide and narrow streets. Our understanding of the transport pathways of molecules through this pore network is limited. We track the movement individual fluorescent molecules on the microscope in order to understand what limits their transport.