Jimena S. Tuninetti

Polydopamine Meets Solid-State Nanopores: A Bioinspired Integrative Surface Chemistry Approach To Tailor the Functional Properties of Nanofluidic Diodes

The ability to modulate the surface chemical characteristics of solid-state nanopores is of great interest as it provides the means to control the macroscopic response of nanofluidic devices. For instance, controlling surface charge and polarity of the pore walls is one of the most important applications of surface modification that is very relevant to attain accurate control over the transport of ions through the nanofluidic architecture. In this work, we describe a new integrative chemical approach to fabricate nanofluidic diodes based on the self-polymerization of dopamine (PDOPA) on asymmetric track-etched nanopores. Our results demonstrate that PDOPA coating is not only a simple and effective method to modify the inner surface of polymer nanopores fully compatible with the fabrication of nanofluidic devices but also a versatile platform for further integration of more complex molecules through different covalent chemistries and self-assembly processes. We adjusted the chemical modification strategy to obtain various configurations of the pore surface: (i) PDOPA layer was used as primer, precursor, or even responsive functional coating; (ii) PDOPA layer was used as a platform for anchoring chemical functions via the Michael addition reaction; and (iii) PDOPA was used as a reactive layer inducing the metallization of the pore walls through the in situ reduction of metallic precursors present in solution. We believe that the transversal concept of integrative surface chemistry offered by polydopamine in combination with the remarkable physical characteristics of asymmetric nanopores constitutes a new framework to design multifunctional nanofluidic devices employing soft chemistry-based nanofunctionalization techniques.

Early stages of ZIF-8 film growth: the enhancement effect of primers exposing sulfonate groups as surface-confined nucleation agents

We describe the use of sulfonate-terminated self-assembled monolayers as very efficient surface-confined nucleation agents for rapid growth of dense, thick and well-percolated ZIF-8 films.

Fabrication of UV responsive micelles-containing multilayers and their influence on cell adhesion

Multilayers incorporated with stimuli-responsive substances by means of layer-by-layer (LbL) self-assembly are much attractive due to their advantages of stimuli-responsiveness and potential applications in different fields. In this study, pyrenemethyl acrylate (PA) was synthesized, and was copolymerized with acrylic acid (AA) to obtain the amphiphilic and photodegradable P(PA-co-AA) polymers with a PA:AA molar ratio of 1.3:3, and an average molecular weight of 6.9 kDa and polydispersity index of 1.04. They formed micelles spontaneously when dispersed in aqueous solution with a size of 27.5 nm in a dry state and 136.6 nm in a wet state. The micelles were readily decomposed to form aggregates as a result of the cleavage of the pyrenemethyl ester bonds under UV-irradiation. UV-responsive micelles-containing multilayers were prepared by LbL self-assembly of the UV-responsive micelles and polyallylamine hydrochloride (PAH). UV-irradiation of the multilayers resulted in the decomposition of micelles, leading to larger surface roughness, and enhanced swelling ratio and wettability of the multilayers. In vitro culture of A549, HepG2 and endothelial cells showed significantly better adhesion at 4 h on the UV-illuminated multilayers, whereas the cell proliferation was not affected significantly until 5 d.

Redox synthesis and high catalytic efficiency of transition-metal nanoparticle–graphene oxide nanocomposites

Although nanocatalysis is a promising area, increased efficiency and greenness are actively sought. Here we report the principle of the syntheses of graphene oxide (GO)-supported metal nanocatalysts (MNPs) for a variety of transition metals including both noble metals and biometal using either exergonic or endergonic redox reactions between GO and the transition metal salts. These new nanocatalysts are highly efficient in water at ambient temperature for 4-nitrophenol reduction (the test reaction), Sonogashira coupling, azide–alkyne 1,3-cycloaddition (click reaction) and dihydrogen production upon hydrolysis of ammonia–borane and recyclable.

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).

Metal–organic frameworks meet polymer brushes: enhanced crystalline film growth induced by macromolecular primers

We used poly-(3-sulfopropylmethacrylate) brushes as macromolecular 3D primers to promote heterogeneous nucleation and growth of archetypal ZIF-8 MOF thin films. The enhancement can be understood in terms of a high preconcentration of Zn2+ ions in the polymer brush; this leads to a rapid increase of nucleation sites in the primer.