The role of palladium surface oxides and adsorbed oxygen in the analytical performance of Pd-NPs-based nanobiosensors is ascertained.

Key parameters affecting hydrazine electrooxidation: electroactive surface area (1)? or surface chemistry (2)?

A novel one-pot chemical synthesis of functional copper iodide-polypyrrole composites, CuI-PPy, has been proposed. The fabrication process allows the formation of nanodimensional metal salt/polymer hybrid structures in a fully controlled time- and concentration-dependent manner. The impact of certain experimental conditions, viz., duration of synthesis, sequence of component addition and concentrations of the intact reagents on the structure, dimensionality and yield of the end-product was evaluated in detail. More specifically, the amount of marshite CuI within the hybrid composite can be ranged from 60 to 90 wt.%, depending on synthetic conditions (type and concentration of components, process duration). In addition, the conditions allowing the synthesis of nano-sized CuI distributed inside the polypyrrole matrix were found. A high morphological stability and reproducibility of the synthesized nanodimensional metal-polymer hybrid materials were approved. Finally, the electrochemical activity of the formed composites was verified by cyclic voltammetry studies. The stability of CuI-PPy composite deposited on the electrodes was strongly affected by the applied anodic limit. The proposed one-pot synthesis of the hybrid nanodimensional copper iodide-polypyrrole composites is highly innovative, meets the requirements of Green Chemistry and is potentially useful for future biosensor development. In addition, this study is expected to generally contribute to the knowledge on the hybrid nano-based composites with tailored properties.

Amperometric nanobiosensors are crucial time and cost effective analytical tools for the detection of a wide range of bioanalytes, viz. glucose present in complex environments at very low concentrations. Although the excellent analytical performance of nanobiosensors is undoubted, their exact molecular structure often remains unclear. Here, by combining advanced nanoanalytical approaches with theoretical modeling, we conducted a comprehensive study towards the investigation of the molecular structure of a hybrid GOx/Nafion/Pd-NPs layer deposited by electroplating from the multicomponent electrolyte solution on the surface of screen printed electrodes modified with graphene oxide. Specifically, we revealed that Pd²⁺ cations were adsorbed on GOx amino acid residues, forming the GOx·nPd²⁺ enzymatic complex. The highest adsorption energy of Pd²⁺ cations on GOx was found during their interaction with the side chains of basic amino acids and methionine. In addition, we showed and fully validated the end-structure of the one-step designed GOx/Nafion/Pd-NPs nanobiosensor as a structural model mainly composed of GOx and water molecules incorporated into the metal–polymer scaffold. Our approach will thus serve as a guideline for the study of molecular interactions occurring in complex systems and will contribute to the design of the next generation of hybrid nanobiosensors. The proposed mechanism, driving the self-assembly of the hybrid layer, will allow us to construct modular enzymatic nanoanalytical devices with tailored sequences in the future.