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.

Cadmium tin oxide (CTO) films on glass substrates were synthesized and functionalized by octadecyltrichlorosilane (OTS). CTO films were transparent with the bandgap of 2.92 eV. They exhibited n-type conductivity and carrier concentration of (3.31 ± 0.38) · 10¹⁹ cm⁻³. Weak temperature dependence points out to a nearly degenerative state of the carriers in the CTO films. Silanization by OTS yielded hydrophobic surface with the contact angle values reaching 103 ± 12 degrees. Silanization of films was followed by a significant reduction of the interfacial capacitance, which upon completion of the functionalization reached levels below 3 μF cm⁻². The value of the electric capacitance as well as data of ATIR absorption, hints at sparse and disordered coverage of the CTO surface by octadecylalkylsilane molecules. Such organic layer, however, was able to trigger phospholipid (60% dioleoylphosphocholine and 40% cholesterol) vesicle rupture and the formation of a secondary layer of phospholipid, thus rendering hybrid bilayer surface construct. Such hybrid constructs may be useful in applications where electrode coupling to a model biological membranes and membrane bound proteins is required, such as biosensing and photovoltaics.

Immobilization of biomaterials is a very important task in the development of biofuel cells and biosensors. Some semiconducting metal-oxide-based supporting materials can be used in these bioelectronics-based devices. In this article, we are reviewing some functionalization methods that are applied for the immobilization of biomaterials. The most significant attention is paid to the immobilization of biomolecules on the surface of semiconducting metal oxides. The improvement of biomaterials immobilization on metal oxides and analytical performance of biosensors by coatings based on conducting polymers, self-assembled monolayers and lipid membranes is discussed.