Chemical Nanospectroscopy

Our research can best be summarized as Chemical Nanospectroscopy. Our main goal is to reveal chemical information with very high spatial resolution at the ultimate limit of single molecules. We develop and apply modern microscopy and laser-spectroscopy techniques for the optical detection, localization and characterization of individual molecules, nanoparticles or defect states with high spatial resolution in the spectral and time domain. A single-molecule spectrum is different from an ensemble spectrum, the lines are narrower and spontaneous line shifts and intensity fluctuations reveal dynamics of a molecule interacting with its local environment. Our workhorses are home-built confocal and near-field optical microscopes equipped with state-of-the art single photon counters, spectrometers and highly sensitive CCD-detectors for recording fluorescence- and Raman spectra. To achieve an optical spatial resolution of 10 nm and beyond, a sharp gold tip is brought close to the sample surface and illuminated with a tightly focused laser beam. The tip works like an optical antenna enhancing the incident optical field in the narrow gap between the tip and the sample by several orders of magnitude and simultaneously increasing the emission of photons from the gap back into the far field. The tip-enhanced luminescence (TESNOM) and Raman signal (TERS) provide true chemical information with very high spatial resolution that is difficult or impossible to reveal with other super-resolution techniques.

Our research combines state of the art topics form physical chemistry (optical single-molecule spectroscopy, quantum dots, nanoparticles, scanning near-field optical microscopy, TERS, organic/inorganic semiconductors, ultra-fast laser spectroscopy), experimental physics (lasers, optical instrumentation, sensors, cryogenics), and molecular biology (Fluorescence Spectroscopy and FLIM in life plant cells).