Fabrication of functional and biocompatible nanomaterials for imaging, sensing an therapeutic applications in life sciences. Specifically, we functionalize carbon nanotubes non-covalently with nucelotide sequences for photodynamic tumor therapy, laser induced hyperthermia and imaging applications.

The exploration of optical properties and dynamics of the constituents of soft matter, a broad class of weakly interacting micron- and nano-sized particles is of great relevance, not only for fundamental nano- and materials-science but also for biological- and life-sciences and for technology. The spectroscopic characterization of individual inorganic nano-crystals, nano-wires, nano-tubes, organic molecules, proteins, DNA as well as small organisms like viruses or bacteria in liquids, however, is frequently impaired by their high mobility due to Brownian or self-propelled motion. We develop a novel and versatile tool for tracking and spectroscopy of single nano- and micron-sized particles in liquid environment.

We study energy and charge transfer processes in nanoscale systems as well as at solid surfaces of bulk systems. Of particular interest are the mechanisms and timescales for redistribution of energy from optically excited states by coupling to electronic, vibrational and translational degrees of freedom. Such processes are crucial for a variety of potential applications of optical materials in optoelectronic- and photovoltaic-devices, or as fluorescent markers.

Energy and charge transfer processes in nanoscaled systems are unique owing to the spatial confinement of electronic states and the influence that interfaces and surfaces play for the electronic and optical properties of small systems. We use a variety of techniques for CW and time-domain spectroscopic investigation of nanoscale systems such as carbon nanotubes, and recently also of semiconductor quantum dots and polymer nanoparticles.

The properties of materials at the nanoscale are strongly affected and sometimes even controlled by their surfaces. We are interested in the role that these interfaces play in determining the optical properties and dynamics of electronically excited states in nanoscale systems and at surfaces of bulk materials. Among others we explore the influence of surfactants and adsorbates for the optical properties of semiconducting carbon nanotubes. DNA oligomers wrapped around semiconducting carbon nanotubes, for example, have been found to be particularly useful for making these hydrophobic molecules water soluble. Can such surfactants or other non-covalent functionalization be used to enhance photoluminescence quantum yields?

The large surface-to-volume ratio of nanomaterials makes them ideal candidates for sensing applications. We explore the opportunities for application of carbon nanotubes and other materials as gas or bio-molecular sensors.

We combine the strengths of femtosecond time-resolved pump-probe spectroscopy with broad and convenient tunability of modern femtosecond laser systems to perform multidimensional spectroscopic characterization of spectral transients as a function of pump and probe wavelengths. This allows to cast new light onto the mechanisms underlying radiative and non-radiative decay of optically excited states.

We study the kinetics of gas-surface interactions, of simple photochemical reactions at surfaces and of nanotube coagulation in colloidal suspensions to achieve a better understanding of how surfaces and interfaces control the properties of these materials.