Electrochemical nanoarchitectonics through polyaminobenzylamine-dodecyl phosphate complexes: redox activity and mesoscopic organization in self-assembled nanofilms.

Molecular design and preparation of redox active films displaying mesoscopic levels of organization represents one of the most actively pursued research areas in nanochemistry. These mesostructured materials are not only of great interest at the fundamental level because of their unique properties but they can also be employed for a wide range of applications such as electrocatalysts, electronic devices, and electrochemical energy conversion and storage. Herein, we introduce a simple and straightforward strategy to chemically modify electrode surfaces with self-assembled electroactive polyelectrolyte-surfactant complexes. These assemblies are composed of amino-appended polyaniline and monododecyl phosphate. The complexes were deposited by spin-coating and the films were characterized by spectroscopic and X-ray-based techniques: XRR, GISAXS, WAXS, and XPS. The films presented a well-defined lamellar structure, directed by the strong interaction between the phosphate groups and the positively charged amine groups in the polyelectrolyte. These films also displayed intrinsic electroactivity in both acidic and neutral solutions, showing that the polymer remains electroactive and ionic transport is still possible through the stratified and hydrophobic coatings. The stability and enhanced electroactivity in neutral solutions make these assembled films promising building blocks for the construction of nanostructured electrochemical platforms.

Highly-organized stacked multilayers via layer-by-layer assembly of lipid-like surfactants and polyelectrolytes. Stratified supramolecular structures for (bio)electrochemical nanoarchitectonics.

Supramolecular self-assembly is of paramount importance for the development of novel functional materials with molecular-level feature control. In particular, the interest in creating well-defined stratified multilayers through simple methods using readily available building blocks is motivated by a multitude of research activities in the field of "nanoarchitectonics" as well as evolving technological applications. Herein, we report on the facile preparation and application of highly organized stacked multilayers via layer-by-layer assembly of lipid-like surfactants and polyelectrolytes. Polyelectrolyte multilayers with high degree of stratification of the internal structure were constructed through consecutive assembly of polyallylamine and dodecyl phosphate, a lipid-like surfactant that act as a structure-directing agent. We show that multilayers form well-defined lamellar hydrophilic/hydrophobic domains oriented parallel to the substrate. More important, X-ray reflectivity characterization conclusively revealed the presence of Bragg peaks up to fourth order, evidencing the highly stratified structure of the multilayer. Additionally, hydrophobic lamellar domains were used as hosts for ferrocene in order to create an electrochemically active film displaying spatially-addressed redox units. Stacked multilayers were then assembled integrating redox-tagged polyallylamine and glucose oxidase into the stratified hydrophilic domains. Bioelectrocatalysis and "redox wiring" in the presence of glucose was demonstrated to occur inside the stratified multilayer.

Polyelectrolyte Capping As Straightforward Approach toward Manipulation of Diffusive Transport in MOF Films.

We present experimental results demonstrating the suitability of polyelectrolyte capping as a simple and straightforward procedure to modify hydrophilic/hydrophobic character of porous films, thus allowing additional control on transport properties. In particular, we synthesized ZIF-8 metal organic framework (MOF) films, an archetypal hydrophobic zeolitic imidazolate framework, constituted by Zn2+ ions tetrahedrally coordinated with bidentate 2-methylimidazolate organic linker, and poly(4-styrenesulfonic acid) as capping agent (PSS). MOF films were synthesized via sequential one pot (SOP) steps over conductive substrates conveniently modified with primer agents known to enhance heterogeneous nucleation, followed by dip-coating with PSS aqueous solutions. Crystallinity, morphology, and chemical composition of ZIF-8 films were confirmed with traditional methods. Continuous electron density depth profile obtained with synchrotron light X-ray reflectivity (XRR) technique, suggest that PSS capped-films do not adopt segregated configurations in which PSS remains surface-confined. This affects functional properties conferred by PSS capping, which were assessed using cyclic voltammetry with both positively and negatively charged redox probe molecules. Furthermore, taking advantage of the control attained, we successfully carried in situ synthesis of film-hosted d-block metal nanoparticles (Au and Pt-NPT@5x-ZIF-8+PSS) via direct aqueous chemical reduction of precursors (diffusion-reaction approach).