In the Nanocrystal Photonics Lab we work with colloidal semiconductor nanocrystals. Materials of choice are typical semiconductors (CdSe, PbS,…), 2D materials (MoS2), or graphene nanoflakes.

The particles are small enough that we can control their opto-electronic properties by varying size, shape and composition. This is made possible due to the quantum confinement effect. Our work reaches from the synthesis of novel nanocrystals with strong fluorescence and/or nonlinear optical properties, to controlled assembly into nanocomposites and thin films, and application of the nanomaterials in photonic devices targeting light emission and energy harvesting.

A strong emphasis is put on triggering the desired optical response by designing nanocrystals via their crystal structure, 3D shape, and using core/shell heteronanocrystals. We study the optical properties (absorption, luminescence) of the nanocrystals and their respective composites with ultrafast optical spectroscopy, a technique that gives information on the material’s behavior on a picosecond to microsecond timescale. We can place the materials at temperatures that range from room temperature down to 4K (-269°C) to use the temperature as a valuable parameter in our experiments. Applications of our work can be found in linear and nonlinear fluorescent dyes, color-converting phosphors, gain material for lasers, single photon emitters, nonlinear optical switches or optical sensors.

Laboratories

The Chemistry Lab is equipped with a chemical hood containing Schlenk lines for nanocrystal synthesis. A nitrogen glovebox, and absorption and fluorescence spectrophotometers are also available in the lab. The Spectroscopy Lab consists of a customized spectrofluorometer allowing steady-state and time-resolved fluorescence spectroscopy in a nano- to microsecond time range, at both visible and near-infrared wavelengths. Faster fluorescence dynamics are measured with a streak camera, with a temporal resolution of 10 picoseconds. Samples can be excited using a femtosecond or nanosecond pulsed laser, and a closed-cycle cryostat permits measurements from room temperature down to 4K.

Collaborations