Wolfgang Fritzsche

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Near-infrared laser pulses of a compact 80-MHz femtosecond laser source at 800 nm, a mean power of 15-100 mW, 170-fs pulse width, and millisecond beam dwell times at the target have been used for multiphoton-mediated nanoprocessing of human chromosomes. By focusing of the laser beam with high-numerical-aperture objectives of a scanning microscope to(More)
Raman spectroscopy is a valuable tool in various research fields. The technique yields structural information from all kind of samples often without the need for extensive sample preparation. Since the Raman signals are inherently weak and therefore do not allow one to investigate substances in low concentrations, one possible approach is surface-enhanced(More)
A new scheme for the detection of molecular interactions based on optical readout of nanoparticle labels has been developed. Capture DNA probes were arrayed on a glass chip and incubated with nanoparticle-labeled target DNA probes, containing a complementary sequence. Binding events were monitored by optical means, using reflected and transmitted light for(More)
An optical technique for the parallel manipulation of nanoscale structures with molecular resolution is presented. Bioconjugated metal nanoparticles are thereby positioned at the location of interest, such as, e.g., certain DNA sequences along metaphase chromosomes, prior to pulsed laser light irradiation of the whole sample. The nanoparticles are designed(More)
The last decade has witnessed the development of a variety of metal nanoparticle-based techniques for DNA detection. High sensitivity and specificity, miniaturization, and cost-efficient detection are problems addressed by the use of nanoparticle labels in heterogeneous DNA detection schemes. The small label size, established bioconjugation chemistry, and(More)
Monolayers of single-stranded DNA on gold substrates were studied by scanning force microscopy. Complementary DNA probes labeled by gold nanoparticles were applied for contrast enhancement. Substrate regions modified with DNA could be visualized in a highly specific manner. The influence of the solution concentration on the surface density of adsorbed(More)
Dawn of nanotechnology: the immersion ultramicroscope was patented a century ago. When an analyte was examined with an antique instrument and with state-of-the-art technology, the historic assumptions were confirmed: the size and shape of the nanoparticles are in the same range as that described 100 years ago. The spectra of the Tyndall cones caused by the(More)
Rapid and effective methods of pathogen identifications are of major interest in clinical microbiological analysis to administer timely tailored antibiotic therapy. Raman spectroscopy as a label-free, culture-independent optical method is suitable to identify even single bacteria. However, the low bacteria concentration in body fluids makes it difficult to(More)
The optical and electrical characterization of nanostructures is crucial for all applications in nanophotonics. Particularly important is the knowledge of the optical near-field distribution for the design of future photonic devices. A common method to determine optical near-fields is scanning near-field optical microscopy (SNOM) which is slow and might(More)
In the last 20 years the practice of DNA sequence detection has gained more and more importance in a variety of fields like-genetics, food safety, pathology, and criminology. This has been driven by the growing knowledge about the human and other organism's genome. The development of sophisticated technologies for the analysis of DNA makes the analysis of(More)