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The Gorris group develops sensitive bioanalytical techniques with the ultimate goal to detect single molecules of an analyte in a much more robust and reproducible way than it is currently possible. It is almost impossible to find a single fluorescent molecule among billions of autofluorescent and light scattering molecules in the same detection volume by standard wide-field fluorescence microscopy. Even worse, real biological samples such as blood are notorious for strong (optical) interference. We have explored two ways out of this classic “needle in a haystack” problem: We use the high catalytic power of enzymes for fluorescence signal amplification – a scheme adopted from the well-known enzyme-linked immunosorbent assay (ELISA). Thousands of fluorescent product molecules enclosed in a femtoliter-sized chamber highlight the presence of a single enzyme molecule. The alternative way leads us to the “optical window”, a spectral region between ~650 and 1000 nm, where optical background interference from biological matrices is largely absent. The unique photophysical properties of photon-upconversion nanoparticles (UCNPs) provide access to the optical window because they can be excited under near-infrared (NIR, 980 nm) light and emit light of shorter wavelengths (anti-Stokes emission).


Finding a single molecule of an analyte in a complex biological matrix.

  1. Analyzing single enzyme molecules in femtoliter arrays.
  2. Photon-upconversion nanoparticles (UCNPs) enable analytical chemistry without optical backgrond interference.
Please do not hesitate to contact us for more information on these projects. We have regular openings for graduate and undergraduate research in our group.
  2. Institute of Analytical Chemistry

PD Dr. Hans-Heiner Gorris

Institute of Analytical Chemistry,
Chemo- and Biosensors



Phone 0941/943-4015

Telefax 0941/943-4064