Electrochemical impedance spectroscopy on layers of polystyrene nanoparticles

Electrochemical impedance spectroscopy (EIS) is a suitable method for characterizing events at the electrode / solution interface. Using EIS, the authors studied solid-based nanoporous matrices, which are formed by densely arranged layers of polystyrene nanoparticles. Due to the hexagonal arrangement of such layers, nanopores of a specific size are present in the matrices. Such nanopores can be modified by receptors and subsequently blocked by ligands, resulting in a significant increase in charge transfer resistance. In this way, antibodies bound to the immobilized specific antigen can be directly detected, and this concept can be used for point-of-care diagnosis of diseases from the patient's blood or blood serum. In the characterization of nanoparticle layers and their modifications, the authors have revealed many effects that have a dominant effect on the electrochemical response. In addition to steric hindrance by immobilized components, the electrochemical impedance using the redox label was greatly affected by how the surface was charged at a given pH. A very interesting phenomenon was the impedance response containing two charge transfer resistance domains due to the non-uniform arrangement of the electric bilayer in multilayer matrices. All measurements were also strongly dependent on the ionic strength of the environment - impedance results at high ionic strength of the environment were affected mainly by steric hindrance of immobilized components, while at low ionic strength by the charge of these components. (authors)