Microspectroscopy of Photonic Materials

Condensed phase photonic materials are investigated in our group using a variety of steady state and time-resolved methods, mostly based on electronic absorption and emission spectroscopies. In order to study 3D structures with sub-micrometer resolution, we employ confocal and widefield imaging microscopies. Because our philosophy is that the requirements of the sample and the measurement should determine the experiment to be done, not the capabilities of the equipment, we have installed a flexible laser system, based on a Ti:sapphire laser with an intracavity doubled optical parametric oscillator and a separate frequency double unit. This allows us to perform fluorescence experiments with excitation from the UV to the near-infrared. Apart from the imaging capabilities, the microscope is equipped with detection systems (EMCCD, SPAD) that give access to characteristic fluorescence parameters such as polarization, decay times, and spectra. We applied this set-up among other things to the study of immobilized metal catalysts (Angew. Chem. Int. Ed., 2010, doi: 10.1002/anie.201000907) and to fluorescence lifetime imaging of flow in a microfluidic chip (J. Am. Chem. Soc. 2009, 131, 17070–17071). Another project is aimed at the direct visualization of the transitions that take place when a polymer latex is transformed from a wet film containing separate particles to a smooth and strong coherent film, in which the polymer chains are in firm contact.

Confocal and wide field microscopies are very attractive methods for the study of individual molecules (Single Molecule Spectroscopy, SMS). Our strategy is to use SMS in combination with more conventional techniques to study the dynamics of rotaxane motor molecules, fluorescent probes, and organocatalytic reaction mechanisms.

Contact: Fred Brouwer, e-mail: a.m.brouwer@uva.nl
Molecular Photonics (UvA)

Brouwer 

Switching the emission of single molecules in a polymer film on and off reversibly by passing through the glass transition temperature (Siekierzycka, J. R.; Hippius, C.; Würthner, F.; Williams, R. M.; Brouwer, A. M., J. Am. Chem. Soc. 2010, 132, 1240-1242).