Active Surfaces in Sensor Technologies Utilizing Ceramic Nanotube-Conducting Polymer Composites Containing Embedded Gold Nanoparticles

This study describes the approach to develop hybrid nanostructures made of four varieties of ceramic nanotubes and three types of conductive polymers embedded with gold nanoparticles through a novel technique, which can exhibit distinct sensory properties not documented in the existing literature. Atomic force microscopy (AFM) analysis highlighted the characteristics of their surface roughness, identifying which could be the best choice for electrochemical electrodes depending on their surface structure. The incorporation of gold nanoparticles modifies the surface structure and forces the original grains to create voids that allow the gold particles to penetrate deeper and gather in small clusters, which in turn leads to a minor increase in grain size and localized sharpening of the peaks. The analysis mainly identified the peaks that were higher in relation to the valleys to identify a Gaussian distribution. It turned out that the configuration of ZnO nanotubes in the composites leads to the highest Ra values, with Al2O3 nanotubes coming in second place. Regarding the contribution of conducting polymers, PANI:EB presented the highest importance for all composites, while P3HT was relevant in several other cases. The evaluation of the electrode roughness, as described in this paper, is essential for the evaluation of its potential electrochemical activity and acts as a reliable measure that goes beyond the role of the evaluation of the active surface area (EASA). In our opinion, the evaluation of the EASA by traditional approaches described in the literature is not relevant for sensor applications, since the evaluation of the electrode surface structure must be performed before electrochemical tests, because the general electrochemical tests designed for sensor applications do not evaluate the EASA. Consequently, a thorough assessment of the electrode surface structure is advised, choosing the optimal electrodes according to this design, and additional data obtained from cyclic voltammetry will finally ascertain the true EASA and the actual performance of the respective electrode for identifying the target molecules.