Kubik Group

Research - Gold Nanoparticles

In a DFG-funded research project, we are developing optical assays for the detection of inorganic anions in aqueous solutions. These assays are based on gold nanoparticles with surface-bound receptors, whose interaction with anions leads to complexes in which the anion connects two receptor units. Anion recognition accordingly causes nanoparticle crosslinking. If the thus formed aggregates remain in solution, the crosslinking causes a color change of the nanoparticle solution from red to violet or blue. If insoluble aggregates are formed, the solution loses its color because the nanoparticles precipitate.


In this context, we showed that gold nanoparticles with a diameter of about 10 nm containing our anion-binding cyclopeptide precipitate from the aqueous solution in the presence of sulfate anions.1 None of eight other tested anions produced an analogous effect. Furthermore, the sulfate detection is not compromised by the simultaneous presence of an excess of other anions. The detection limit is close to the concentration above which mineral water is classified as sulfate-rich.


Gold nanoparticles with surface-bound zinc(II)-dipicolylamine complexes allow the detection of diphosphate and triphosphate anions. In this case, the solubility of the nanoparticles requires the assay to be performed in a methanol/water mixture.2 Other anions again do not interfere. Only phosphate and arsenate anions cause the nanoparticles to precipitate if they are present at high concentrations. In contrast to the cyclopeptide-containing nanoparticles, a lower concentration exists in this case at which the nanoparticles precipitate, and an upper concentration at which they redissolve. With a detection limit of 10 μmol/L, these nanoparticles could be used to detect diphosphate concentrations that are usually present in urine or saliva.


The detection limits of these nanoparticles depend on the ratio of the two surface-bound ligands, of which one mediates nanoparticle solubility and the other carries the receptor units. By changing this ratio, the properties of the nanoparticles and, in turn, their behavior can be controlled.


  1. J. Bartl, L. Reinke, M. Koch, S. Kubik Chem. Commun. 2020, 56, 10457-10460.
  2. L. Reinke, J. Bartl, M. Koch, S. Kubik Beilstein J. Org. Chem. 2020, 16, 2687-2700.

Last change: 21-04-14. Email