Scientists at ETH Zurich and the Lawrence Livermore National Laboratory (LLNL) in California have developed an innovative sensor for surface-enhanced Raman spectroscopy (SERS). Thanks to its unique surface properties at nanoscale, the method can be used to perform analyses that are more reliable, sensitive and cost-effective. In experiments with the new sensor, the researchers were able to detect a certain organic species (1,2bis(4-pyridyl)ethylene, or BPE) in a concentration of a few hundred femtomoles per litre. A 100 femtomolar solution contains around 60 million molecules per litre.
Until now, the detection limit of common SERS systems was in the nanomolar range, i.e. one billionth of a mole. The results of a study conducted by Hyung Gyu Park, Professor of Energy Technology at ETH Zurich, and Tiziana Bond, Capability Leader at LLNL, were published this week as a cover article in the scientific journal Advanced Materials.
Raman spectroscopy takes advantage of the fact that molecules illuminated by fixed-frequency light exhibit 'inelastic' scattering closely related to the vibrational and rotational modes excited in the molecules. Raman scattered light differs from common Rayleigh scattered light in that it has different frequencies than that of the irradiating light and produces a specific frequency pattern for each substance examined, making it possible to use this spectrum information as a fingerprint for detecting and identifying specific substances. To analyse individual molecules, the frequency signals must be amplified, which requires that the molecule in question either be present in a high concentration or located close to a metallic surface that amplifies the signal. Hence the name of the method: surface-enhanced Raman spectroscopy.
Amplified signals for improved reproducibility
"This technology has been around for decades," explains Ali Altun, a doctoral student in the group led by Park at the Instit
|Contact: Hyung Gyu Park|