• density gradient centrifugation;
  • gold;
  • nanoparticles;
  • purification;
  • Raman spectroscopy
Thumbnail image of graphical abstract

The cover picture summarizes the results of the separation of gold colloids by continuous density gradient centrifugation. The central aim of this study was to obtain highly purified metal colloids, in particular, the dimers in the central image and trimers. The UV–vis extinction spectra of dimers (cyan) and trimers (magenta) of ≈30 nm gold nanospheres are shown. A standard table-top centrifuge (background) and glycerol/water mixtures as separation media were employed. Larger amounts of such highly purified metal colloids are required for real-world applications, for example, for use as labels or nanotags in assays and microscopy based on surface-enhanced Raman scattering (SERS). For more information, please read the Communication “Fast and Cost-Effective Purification of Gold Nanoparticles in the 20–250 nm Size Range by Continuous Density Gradient Centrifugation” by S. Schlucker and co-workers, beginning on page 2443.