Lyudmila M. Bronstein

From cyclodextrin assemblies to porous materials by silica templating.

[15] This is a high-concentration synthesis in which the solidified inorganic compound is a copy of the original phase structure, that is its structure is predetermined by the selection of the template phase. They used lyotropic liquid-crystalline phases, derived from surfactants or–later–block copolymers, [15±17]

Interaction of metal compounds with double-hydrophilic block copolymers in aqueous medium and metal colloid formation.

Abstract The interaction of a ‘double-hydrophilic’ polyethyleneoxide-polyethyleneimine block copolymer (PEO-b-PEI) with AuCl3, PdCl2, Na2PdCl4, H2PtCl6·6H2O, Na2PtCl6·6H2O, and K2PtCl4 in aqueous medium was studied. Micellar structure formation was observed for all metal compounds except Na2PdCl4 where additional protonation of the polymer was required to induce micelle formation. The characteristics of the micelles formed depended strongly on the metal type, the molar ratio polymermetal compound, and the type of reducing agent. Micellization in the presence of AuCl3·H2O is accompanied with reduction of the salt and the formation of gold colloid without reducing agent induced by oxidation of the PEI block. The interaction with PtCl62− ions results in narrowly distributed micelles wi size depending on the metal compound loading. In the case of loading with H2PtCl6, it was found that the size and shape of the colloids can be controlled by changing the molar ratio PEI:metal salt. The lower is the metal loading, the smaller are the particles. In addition, differently shaped Pt colloids were observed. This phenomenon can be controlled by the relative ratio of reactants.

Nanoparticles Made in Mesoporous Solids

This review with 98 references describes the synthesis of mesoporous materials containing nanoparticles, characterization of these materials and their material properties: catalytic, optical, and magnetic. All synthetic methods are grouped into seven categories depending on the way of metal compound incorporation and metal particle formation. Advantages and disadvantages of each method for each particular application are discussed. A short description of methods used for characterization of mesoporous materials with nanoparticles is presented including examples of their applications. Catalytic, optical, and magnetic properties of mesoporous solids containing nanoparticles are discussed.

Functionalization of monodisperse iron oxide NPs and their properties as magnetically recoverable catalysts.

Here we report the functionalization of monodisperse iron oxide nanoparticles (NPs) with commercially available functional acids containing multiple double bonds such as linolenic (LLA) and linoleic (LEA) acids or pyridine moieties such as 6-methylpyridine-2-carboxylic acid, isonicotinic acid, 3-hydroxypicolinic acid, and 6-(1-piperidinyl)pyridine-3-carboxlic acid (PPCA). Both double bonds and pyridine groups can be reacted with noble metal compounds to form catalytically active species in the exterior of magnetic NPs, thus making them promising magnetically recoverable catalysts. We determined that both LLA and LEA stabilize magnetic iron oxide NPs, allowing the formation of π-complexes with bis(acetonitrile)dichloropalladium(II) in the NP shells. In both cases, this leads to the formation of NP aggregates because of interparticle complexation. In the case of pyridine-containing ligands, only PPCA with two N-containing rings is able to provide NP stabilization and functionalization whereas other pyridine-containing acids did now allow sufficient steric stabilization. The interaction of PPCA-based particles with Pd acetate also leads to aggregation because of interparticle interactions, but the aggregates that are formed are much smaller. Nevertheless, the catalytic properties in the selective hydrogenation of dimethylethynylcarbinol (DMEC) to dimethylvinylcarbinol were the best for the catalyst based on LLA, demonstrating that the NP aggregates in all cases are penetrable for DMEC. Easy magnetic separation of this catalyst from the reaction solution makes it promising as a magnetically recoverable catalyst.

Synthesis of Pd-, Pt-, and Rh-containing polymers derived from polystyrene-polybutadiene block copolymers; micellization of diblock copolymers due to complexation

Novel Pt-containing polymers derived from Zeise salt and polystyrene-polybutadiene diblock (PS-PB) and triblock (SBS) copolymers have been synthesized. The comparison of complex formation peculiarities of Pd-, Rh-, and Pt-containing polymers derived from SBS with 72 wt.-% of PB and PS-PB with 15 wt.-% of PB displayed that a short PB block in PS-PB allows to maintain solubility of organometallic polymers even if intermolecular complexation is probable. Such a solubility was found to be provided by micellization in Pd-, Pt-, and Rh-containing polymers derived from PS-PB. Moreover, crosslinks formed due to complexation were shown to contribute to micellization: iron carbonyl complexes immobilized on PS-PB, where solely intramolecular complexes can be formed, do not provide micellization.

Magnetic Virus-like Nanoparticles in N. benthamiana Plants: A New Paradigm for Environmental and Agronomic Biotechnological Research

This article demonstrates the encapsulation of cubic iron oxide nanoparticles (NPs) by Brome mosaic virus capsid shells and the formation, for the first time, of virus-based nanoparticles (VNPs) with cubic cores. Cubic iron oxide NPs functionalized with phospholipids containing poly(ethylene glycol) tails and terminal carboxyl groups exhibited exceptional relaxivity in magnetic resonance imaging experiments, which opens the way for in vivo MRI studies of systemic virus movement in plants. Preliminary data on cell-to-cell and long-distance transit behavior of cubic iron oxide NPs and VNPs in Nicotiana benthamiana leaves indicate that VNPs have specific transit properties, i.e., penetration into tissue and long-distance transfer through the vasculature in N. benthamiana plants, even at low temperature (6 °C), while NPs devoid of virus protein coats exhibit limited transport by comparison. These particles potentially open new opportunities for high-contrast functional imaging in plants and for the delivery of therapeutic antimicrobial cores into plants.

Water-soluble surface-anchored gold and palladium nanoparticles stabilized by exchange of low molecular weight ligands with biamphiphilic triblock copolymers.

A study is presented of the stabilization of gold and palladium nanoparticles (NPs) via a place-exchange reaction. Au and Pd NPs of approximately 3.5 nm were prepared by a conventional method using tetraoctylammonium bromide (TOAB) as the stabilizing agent. The resulting nanoparticles, referred to as Au-TOAB or Pd-TOAB, were later used as templates for the replacement of TOAB ligand with poly(ethylene oxide)- b-polystyrene- b-poly(4-vinylpyridine) (PEO- b-PS- b-P4VP) triblock copolymer. This biamphiphilic triblock copolymer was synthesized by atom transfer radical polymerization (ATRP) with control over the molecular weight and polydispersity. The place-exchange reaction was mediated through strong coordination forces between the 4-vinylpyridine copolymer and the metal species located on the surface of the nanoparticles. In addition, the displacement of the outgoing low molecular weight TOAB ligands by high molecular weight polymers is an entropy-assisted process and is believed to contribute to stabilization. The prepared complex, polymer-NP, exhibits greatly improved stability over the metal-NP complex in common organic solvents for the triblock copolymer. Self-assembly in water after ligand exchange resulted in micellar structures of about approximately 20 nm (electron microscopy) with the metal NP found located on the surface of the micelles. The stability of the nanoparticles in water was shown to depend greatly on the grafting density of the copolymer, with high stability (more than 6 months) at high grafting density and low stability, accompanied with irreversible agglomeration, at relatively low grafting densities. The surprising location of the metal NP (for both Au and Pd) on the surface of the micelles in water is explained by the fact that, upon self-assembly in THF/water system, the most hydrophobic chains (i.e., PS) undergo self-assembly first at low water content forming the core, followed by the P4VP (whether or not associated with the metal) forming a shell, and finally the PEO forming the corona. In lower metal content assemblies, the P4VP chains located in the shell undergo swelling in an acidic medium causing a substantial increase in micellar corona size, as confirmed by dynamic light scattering measurements. The present study offers a simple approach for the stabilization of various metal nanoparticles of catalytic interest, using a unique polymeric support that can be dispersed in organic solvents as well as aqueous solutions.

Design of organic–inorganic solid polymer electrolytes: synthesis, structure, and properties

This paper reports the synthesis, structure, and properties of novel hybrid solid polymer electrolytes (SPEs) consisting of organically modified aluminosilica (OM-AlSi), formed within a poly(ethylene oxide)-in-salt (Li triflate) phase. To alter the structure and properties of these polymer electrolytes, we used functionalized silanes containing poly(ethylene oxide) (PEO) tails or CN groups. The SPEs described here were studied using differential scanning calorimetry, Raman spectroscopy, X-ray powder diffraction, and AC impedance spectroscopy. The size of the OM-AlSi domains was estimated using transmission electron microscopy and comparing the sizes of AlSi nanoparticles, obtained via calcination of the hybrid SPE. The conductivity enhancement, caused by incorporation of PEO tails or CN groups in the hybrid materials based on 600 Da poly(ethylene glycol), can be ascribed to a decrease of OM-AlSi domain size accompanied by an increase of the OM-AlSi/PEO + LiTf interface. For the CN modifier, increase of this interface increases the amount of CN groups exposed to PEO + LiTf phase, thus increasing the effective dielectric constants of the materials and their conductivity, although this dependence is not linear. In the case of the PEO modifier, different effects are observed for 600 Da PEG and 100 kDa PEO. For 100 kDa PEO, incorporation of the silane with a PEO tail caused a decrease of conductivity. Here, AlSi particle size remains basically unchanged with addition of silane-modifier, and the decrease of conductivity can be attributed to formation of a crystalline phase at the OM-AlSi/PEO + LiTf interface.

Micellization in pH-sensitive amphiphilic block copolymers in aqueous media and the formation of metal nanoparticles.

Dynamic light scattering, potentiometric titration, transmission electron microscopy and atomic force microscopy have been used to investigate the micellar behaviour and metal-nanoparticle formation in poly(ethylene oxide)-block-poly(2-vinylpyridine), PEO-b-P2VP, poly(hexa(ethylene glycol) methacrylate)-block-poly(2-(diethylamino)ethyl methacrylate), PHEGMA-b-PDEAEMA, and PEO-b-PDEAEMA amphiphilic diblock copolymers in water. The hydrophobic block of these copolymers (P2VP or PDEAEMA) is pH-sensitive: at low pH it can be protonated and becomes partially or completely hydrophilic leading to molecular solubility whereas at higher pH micelles are formed. These micelles consist of a P2VP or PDEAEMA core and a PEO or PHEGMA corona, respectively, where the core forming amine units can incorporate metal compounds due to coordination. The metal compounds (e.g., H2PtCl6, K2PtCl6) can either be introduced in a micellar solution, where they are incorporated within the micelle core via coordination with functional groups, or can be added to a unimer solution at low pH, where they lead to a metal-induced micellization. In these micellar nanoreactors, metal nanoparticles nucleate and grow upon reduction with sizes in the range of a few nanometers as observed by TEM. The effect of the metal incorporation method on the characteristics of the micelles and of the synthesized nanoparticles is investigated.

Virus-Based Nanoparticles with Inorganic Cargo: What Does the Future Hold?

An analysis of the accumulated knowledge on virus-based nanoparticles (VNPs) consisting of virus protein capsids and inorganic cargo, such as nanoparticles (NPs), nanowires, and thin layers, is presented. Virus capsids (VCs) can serve either as templates or nanoreactors when inorganic materials are formed outside or inside VCs. The third possibility is when inorganic NPs nucleate the formation of VCs. The structural and mechanistic studies of VNP formation are paving the way to a better understating of virus structure and behavior, and these facilitate promising applications of VNPs in biomedical and materials research.