A Comparative Study of PMETAC-Modified Mesoporous Silica and Titania Thin Films for Molecular Transport Manipulation

The manipulation and understanding of molecular transport across functionalized nanopores will take us closer to mimicking biological membranes and thus to design high-performance permselective separation systems. In this work, Surface-initiated atom transfer radical polymerization (SI-ATRP) of (2-methacryloyloxy)-ethyltrimethylammonium chloride (METAC) was performed on both mesoporous silica and mesoporous titania thin films. Pores were proven to be filled using ellipsometry and diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). Furthermore, the employed method leads to a polymer overlayer, whose thickness could be discriminated using a double-layer ellipsometry model. Cyclic voltammetry experiments reveal that the transport of electrochemically active probes is affected by the PMETAC presence, both due to the polymer overlayer and the confined charge of the pore-tethered PMETAC. A more detailed study demonstrates that ion permeability depends on the combined role of the inorganic scaffolds’ (titania and silica) surface chemistry and the steric and charge exclusion properties of the polyelectrolyte. Interestingly, highly charged negative walls with positively charged polymers may resemble zwitterionic polymer behavior in confined environments

Mesoporous Microspheres of Nickel-based Layered Hydroxides by Aerosol-Assisted Self-Assembly using Crystalline Nano-Building Blocks.

Structural control in micro- and nanometer scale is necessary to design highly functional materials. Crystalline mesoporous microspheres are expected to improve electrochemical, catalytic, and adsorption performances. In this study, we focused on the preparation of templated mesoporous microspheres of nickel-based layered hydroxides by using pre-crystallized nano-building blocks (NBBs). Layered nickel hydroxide nanoparticles were prepared through an epoxide-mediated alkalinization process and used as NBBs to construct microspheres. The spherical particles in micrometer scale were synthesized by an aerosol-assisted assembly of the NBBs dispersed in a solvent, in the presence of supramolecular templates. It was found that controlling the crystallization as well as the surface philicity permits to yield the NBB with an adequately small size and interparticle interactions that generate self-assembled mesoporous microspheres akin to those obtained in NBB-based mesoporous thin films. The preparation technique demonstrated here is highly versatile; templated mesoporous microspheres with various chemical compositions of nickel-based layered double hydroxides were successfully obtained.The present work was partially supported by JSPS KAKENHI, JSPS bilateral program, LNLS proposal SAXS1 18927, ANPCyT (PICT 2012-2087 and 2015-3526), UBACyT (20020130100610BA), Hitachi Metals Materials Science Foundation, The Sumitomo Foundation, and Izumi Science and Technology Foundation

Microparticles with hetero-nanointerfaces: controlled assembly of cobalt hydroxide and nickel hydroxide nanoclusters towards improved electrochemical functions

The ultimate control of the interfaces of nanocomposite materials is essential to tailor and improve their physical/chemical properties in applications such as catalysis, or energy storage or production. Fabrication and co-assembly of a variety of nanostructured colloids is a promising way to design the interface of materials in nano-scale toward high functionality. In this study, we demonstrate a synthesis of colloids of nanocluster-sized (~ 2 nm) cobalt and nickel hydroxides and their assembly into microparticles that present hetero-nanointerfaces. Electrochemical properties were investigated to elucidate the effect of the hetero-nanointerface. Microparticles with hetero nanostructures composed of cobalt and nickel hydroxide nanoclusters revealed improved mass specific capacity (91.4 mAh/g) compared with respective microparticles with homo-nanointerface (cobalt hydroxide; 15.8 mAh/g: nickel hydroxide; 64.4 mAh/g). Further investigation suggests that the introduced hetero-nanointerface leads to lower charge transfer resistance and to improved electrochemical properties. The synthetic concept demonstrated here is expected to create unique hetero-nanointerfaces for various materials with wide-range of chemical composition towards improved and novel functionalities.The present work is partially supported by JSPS KAKENHI, LNLS proposal SAXS1 18927, ANPCyT (PICT 2087), UBACyT (20020130100610BA), Izumi Science and Technology Foundation (H29-J-130) and the Foundation for the Promotion of Ion Engineering

Single-nanometer sized low-valence metal hydroxide crystals: synthesis via epoxide-mediated alkalinization and assembly towards functional mesoporous materials

The present work is partially supported by JSPS KAKENHI, LNLS proposal SAXS1 18927, ANPCyT (PICT 2087), UBACyT (20020130100610BA), and the Foundation for the Promotion of Ion Engineering

Highly Ordered Mesoporous Hydroxide Thin Films through Self-Assembly of Size-Tailored Nano-Building Blocks: A Theoretical- Experimental Approach

Mesoporous crystalline (hydr)oxides of low-valence metal ions (M(II) and M(III)) are highly demanded in the context of various applications. In this study, we demonstrate key factors to the successful formation of ordered mesoporous films through the Assembly of Nano-Building Block (ANBB) approach using a colloidal solution of crystalline M(OH)2 (M = Mn, Fe, Co, Ni, and Cu). The colloidal system of α-Ni(OH)2 is presented in-depth as a typical example. Crystal growth and aggregation kinetics of the NBB were tuned by synthetic parameters. Nanometer-sized NBBs of tailored size between oligomer scale to over 20 nm were obtained. The films prepared from α-Ni(OH)2 NBBs with a diameter of ≤ 7.5 nm showed ordered mesostructures through evaporation-induced self-assembly in the presence of supramolecular templates. Coarse-grained simulation suggests that there is a threshold diameter of NBB toward the formation of wellordered mesostructures. It was found that, as well as limiting the diameter of NBB, inhibition of an aggregation of NBBs by using coordinative additives or diluting the NBB colloidal solution were essential to control the assembly of NBBs and templates into the ordered mesostructures. The results obtained here open up the synthesis of ordered mesoporous materials with a crystalline wall of variety of chemical compositions containing low-valence metal elements.The present work was partially supported by JSPS KAKENHI, JSPS bilateral program, ABTLuS (LNLS proposal SAXS1 18927), ANPCyT (PICT 2014-3687 and 2015-3526), UBACyT (20020130100610BA), The Sumitomo Foundation, Izumi Science and Technology Foundation and Deutsche Forschungsgemeinschaft-CONICET under grant Mu1674/15-1

Impact of PEGylation on the degradation and pore organization in Mesoporous Silica Nanoparticles: a study of the inner mesoporous structure in physiologically relevant ionic conditions

The degradation of mesoporous silica nanoparticles (MSNs) in the biological milieu due to silica hydrolysis plays a fundamental role for the delivery of encapsulated drugs and therapeutics. However, little is known on the evolution of the pore arrangement in the MSNs in biologically relevant conditions. Small Angle X-ray scattering (SAXS) studies were performed on unmodified and PEGylated MSNs with a MCM-48 pore structure and average sizes of 140 nm, exposed to simulated body fluid solution (SBF) at pH 7.4 for different time intervals from 30 min to 24 h. Experiments were performed with silica concentrations below, at and over 0.14 mg/mL, the saturation concentration of silica in water at physiological temperature. At silica concentrations of 1 mg/mL (oversaturation), unmodified MSNs show variation in interpore distances over 6 h exposure to SBF, remaining constant thereafter. A decrease in radius of gyration is observed over the same time. Mesoporosity and radius of gyration of unmodified MSNs remain then unchanged up to 24 h. PEGylated MSNs at 1 mg/mL concentration show a broader diffraction peak but no change in the position of the peak is observed following 24 h exposure to SBF. PEGylated MSNs at 0.01 mg/mL show no diffraction peaks already after 30 min exposure to SBF, while at 0.14 mg/mL a small diffraction peak is present after 30 min exposure but disappears after 1 h.Fil: Ramirez, Maria de Los Angeles. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de San Martin. Instituto de Nanosistemas; Argentina. Basque Research and Technology Alliance. CIC biomaGUNE; EspañaFil: Bindini, Elisa. Basque Research and Technology Alliance. CIC biomaGUNE; EspañaFil: Moretti, Paolo. Università Politecnica Delle Marche; ItaliaFil: Soler Illia, Galo Juan de Avila Arturo. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de San Martin. Instituto de Nanosistemas; ArgentinaFil: Amenitsch, Heinz. Graz University Of Technology.; AustriaFil: Andreozzi, Patrizia. Università degli Studi di Firenze; Italia. Basque Research and Technology Alliance. CIC biomaGUNE; EspañaFil: Ortore, Maria Grazia. Università Politecnica Delle Marche; ItaliaFil: Moya, Sergio E.. Basque Research and Technology Alliance. CIC biomaGUNE; Españ

Proton and Calcium-Gated Ionic Mesochannels: Phosphate-Bearing Polymer Brushes Hosted in Mesoporous Thin Films As Biomimetic Interfacial Architectures

Rational construction of interfaces based on multicomponent responsive systems in which molecular transport is mediated by structures of nanoscale dimensions has become a very fertile research area in biomimetic supramolecular chemistry. Herein, we describe the creation of hybrid mesostructured interfaces with reversible gate-like transport properties that can be controlled by chemical inputs, such as protons or calcium ions. This was accomplished by taking advantage of the surface-initiated polymerization of 2-(methacryloyloxy)ethyl phosphate (MEP) monomer units into and onto mesoporous silica thin films. In this way, phosphate-bearing polymer brushes were used as “gatekeepers” located not only on the outer surface of mesoporous thin films but also in the inner environment of the porous scaffold. Pore-confined PMEP brushes respond to the external triggering chemical signals not only by altering their physicochemical properties but also by switching the transport properties of the mesoporous film. The ion-gate response/operation was based on the protonation and/or chelation of phosphate monomer units in which the polymer brush works as an off-on switch in response to the presence of protons or Ca2+ ions. The hybrid meso-architectured interface and their functional features were studied by a combination of experimental techniques including ellipso-porosimetry, cyclic voltammetry, X-ray reflectivity, grazing incidence small-angle X-ray scattering, X-ray photoelectron spectroscopy, and in situ atomic force microscopy. In this context, we believe that the integration of stimuli-responsive polymer brushes into nanoscopic supramolecular architectures would provide new routes toward multifunctional biomimetic nanosystems displaying transport properties similar to those encountered in biological ligand-gated ion channels.Instituto de Investigaciones Fisicoquímicas Teóricas y AplicadasConsejo Nacional de Investigaciones Científicas y Técnica

Chemical Stability of Mesoporous Oxide Thin Film Electrodes under Electrochemical Cycling: from Dissolution to Stabilization

Mesoporous oxide thin films (MOTF) present very high surface areas and highly controlled monodisperse pores in the nanometer range. These features spurred their possible applications in separation membranes and permselective electrodes. However, their performance in real applications is limited by their reactivity. Here, we perform a basic study of the stability of MOTF toward dissolution in aqueous media using a variety of characterization techniques. In particular, we focus in their stability behavior under the influence of ionic strength, adsorption of electrochemical probes, and applied electrode potential. Mesoporous silica thin films present a limited chemical stability after electrochemical cycling, particularly under high ionic strength, due to their high specific surface area and the interactions between the electrochemical probes and the surface. In contrast, TiO₂ or Si0.9Zr0.1O₂ matrices present higher stability; thus, they are an adequate alternative to produce accessible, sensitive, and robust permselective electrodes or membranes that perform under a wide variety of conditions.Facultad de Ciencias ExactasInstituto de Investigaciones Fisicoquímicas Teóricas y Aplicada

Introduction to celebrating Latin American talent in chemistry

In celebration of the excellence and breadth of Latin American research achievements across the chemical sciences, we are delighted to present an introduction to the themed collection, Celebrating Latin American talent in chemistry. [Image: see text

Mesoporous hybrid thin films: the physics and chemistry beneath

Mesoporous films containing organic or biological functions within an organised array of cavities are produced by combining sol-gel, self-assembly of supramolecular templates and surface chemistry. This paper reviews the essential physics and chemical concepts behind the synthesis of these complex multifunctional materials