Scanning electrochemical microscopy (SECM) hybridized with fast Fourier transform-based electrochemical impedance spectroscopy (FFT-EIS) seems to be a powerful variation of scanning electrochemical impedance microscopy (SEIM), wherein both state-of-the-art techniques are combined (FFT-SEIM) and can be used for the investigation and treatment of tissues at single cell level. However, in most EIS-based experiments, harmful redox mediators are applied, which affect the functioning of living cells and tissues. Therefore, the development of a redox-probe-free FFT-SEIM is still a very important challenge in electrochemistry. For this reason, in this research, we have demonstrated a redox-probe-free evaluation of conducting and non-conducting surfaces by combining scanning electrochemical microscopy with FFT-EIS. It was demonstrated that using the fast Fourier transform-based FFT-EIS technique, EIS spectra could be registered much faster compared to experiments performed using the conventional EIS equipment. An ultramicroelectrode (UME) was used as a scanning electrode to ensure high spatial resolution. We have performed FFT-SEIM measurements in a redox-probe-free mode (without any additional redox probes) and have investigated several surfaces with different conductivities. The FFT-EIS equipment and the built-in software help to avoid the influence of possible formation of hydrogen bubbles on the UME. This research opens up a new avenue for the application of FFT-SEIM in the investigation of samples that are unstable and very sensitive towards redox mediators (e.g., tissues and/or living cells).

In this research, a 9,10-phenanthrenequinone (PQ) was electrochemically polymerized on a graphite rod electrode using potential cycling. The electrode modified by poly-9,10-phenanthrenequinone (poly-PQ) was studied by means of cyclic voltammetry, electrochemical impedance spectroscopy, atomic force microscopy and scanning electron microscopy. The poly-PQ shows variations in growth pattern depending on the number of potential cycles for the initiation of polymerization. Formed poly-PQ layer demonstrates good electric conductivity, great degree of electrochemical capacitance and unique oxidation/reduction properties, which are suitable for broad technological applications, including applicability in biosensors, supercapacitors and in some other electrochemical systems.

Various forms of zinc oxide (ZnO) are frequently used in the design of optical and electrochemical sensors. However, the optical and electrochemical properties of ZnO should be properly adjusted depending on the application area. Therefore, in this work, we have investigated changing/tuning the properties of ZnO by depositing a layer of polydopamine (PDA) on its surface. In order to perform this investigation, the surface of fluorine-doped tin oxide (FTO) was modified with the layer of ZnO nanorods and PDA. ZnO nanorods were synthesized by hydrothermal synthesis technique, and after the synthesis, they were coated with polydopamine exploiting the self-polymerization of dopamine. The nanostructures were investigated by using electrochemical and optical methods. Electrochemical impedance spectroscopy measurements showed that electrochemical properties of FTO-ZnO and FTO-ZnO-PDA nanostructures could be changed by the variation of both—applied electrical potential and/or exposition towards lighting. Interaction between ZnO-PDA and bovine serum albumin (BSA) molecules has been investigated by (photo)electrochemical and photoluminescence methods. A mechanism of possible interaction between BSA and the ZnO-PDA surface has been proposed.