Time, space and spectrally resolved photochemistry from ensembles to single molecules

Coupling of photophysical and photochemical techniques to microscopy eventually assisted by manipulating techniques, such as laser trapping, has facilitated obtaining information on heterogeneous organic and bio-organic systems by mapping their optical and excited state properties. Scanning confocal microscopy, eventually of laser trapped ensembles, coupled to fluorescence decay analysis and imaging, scanning plate confocal and scanning near field optical microscopy provide combined spectral and spatial resolution down to a few tenths of nanometers. An even better resolution can be achieved using scanning tunneling microscopy. In this contribution a number of organic and macromolecular systems are discussed first in solution and in a next step assembled either in a trap or at a surface. The techniques are illustrated and their limits assessed using latex particles labeled with fluorophores. Time resolved spectroscopy in solution allows the evaluation of migration of the excited state and the collapse of the arms in a dendritic structure. These and other macromolecular structures can be trapped and the obtained assembly visualized and analyzed. Deposition by self-assembly provides the possibility using scanning near field optical microscopy to investigate the excited state properties of ordered arrays. By dilution in a polymer film of dendritic structures single particle, single chromophore and single molecule spectroscopy becomes accessible. Scanning tunneling microscopy is successfully applied to illustrate the visualization and manipulation of structures with subnanometer resolution and the study of their properties including stimulus by light induced transformations.