Milling Down to Nanometers: A General Process for the Direct Dry Synthesis of Supported Metal Catalysts

Supported catalysts are among the most important classes of catalysts. They are typically prepared by wet‐chemical methods, such as impregnation or co‐precipitation. Here we disclose that dry ball milling of macroscopic metal powder in the presence of a support oxide leads in many cases to supported catalysts with particles in the nanometer size range. Various supports, including TiO₂, Al₂O₃, Fe₂O₃, and Co₃O₄, and different metals, such as Au, Pt, Ag, Cu, and Ni, were studied, and for each of the supports and the metals, highly dispersed nanoparticles on supports could be prepared. The supported catalysts were tested in CO oxidation, where they showed activities in the same range as conventionally prepared catalysts. The method thus provides a simple and cost‐effective alternative to the conventionally used impregnation methods.     

Raman scattering of MnOx?CeOx composite catalysts: structural aspects and laser‐heating effects

Composite MnO_x CeO_x catalysts (Mn_at: Ce_at = 1) synthesized via the redox and coprecipitation routes were comparatively characterized by micro‐Raman spectroscopy using a laser irradiation power ranging between 0.6 and 4.2 mW. A quasi‐molecular dispersion of the oxide species determines a major and irreversible structural rearrangement of the redox MnO_x CeO_x system because of severe heating effects for laser power in excess of 0.6 mW. The X‐ray diffraction data of samples calcined in the range of 673 1273 K confirm that the micro‐Raman characterization of the composite MnO_x CeO_x systems requires an adequate minimization of the irradiation power to prevent the strong sintering and restructuring phenomena due to laser‐heating effects. Copyright © 2011 John Wiley & Sons, Ltd.     

Structure-based approach for identification of novel phenylboronic acids as serine-β-lactamase inhibitors

β-Lactamases are bacterial enzymes conferring resistance to β-lactam antibiotics in clinically-relevant pathogens, and represent relevant drug targets. Recently, the identification of new boronic acids (i.e. RPX7009) paved the way to the clinical application of these molecules as potential drugs. Here, we screened in silico a library of ~1400 boronic acids as potential AmpC β-lactamase inhibitors. Six of the most promising candidates were evaluated in biochemical assays leading to the identification of potent inhibitors of clinically-relevant β-lactamases like AmpC, KPC-2 and CTX-M-15. One of the selected compounds showed nanomolar K _i value with the clinically-relevant KPC-2 carbapenemase, while another one exhibited broad spectrum inhibition, being also active on Enterobacter AmpC and the OXA-48 class D carbapenemase.     

Silica nanoparticles for fluorescence sensing of Zn(II): exploring the covalent strategy

Silica nanoparticles (about 15 nm diameters), which contain a derivative of 6-methoxy-8-(p-toluensulfonamido)-quinoline (TSQ) as a Zn(II) fluorescent probe covalently linked to the silica network, were prepared and studied as Zn(II) fluorescent chemosensors. The systems selectively detect Zn(II) ions in water rich solutions with a submicromolar sensitivity: 0.13 microM concentrations of Zn(II) can be measured with the only interference of Cu(II) and Cd(II) ions. Compared with free TSQ, the nanoparticles based systems have the advantage that they can be employed in aqueous solutions without aggregation problems while at the same time, they maintain a similar Zn(II) affinity and sensing ability. Addition of a second, substrate insensitive, fluorophore to the particles leads to the realization of a ratiometric sensor.     

Chemical and Mechanical Characterization of Licorice Root and Palm Leaf Waste Incorporated into Poly(urethane-acrylate) (PUA)

A poly(urethane-acrylate) polymer (PUA) was synthesized, and a sufficiently high molecular weight starting from urethane-acrylate oligomer (UAO) was obtained. PUA was then loaded with two types of powdered ligno-cellulosic waste, namely from licorice root and palm leaf, in amounts of 1, 5 and 10%, and the obtained composites were chemically and mechanically characterized. FTIR analysis of final PUA synthesized used for the composite production confirmed the new bonds formed during the polymerization process. The degradation temperatures of the two types of waste used were in line with what observed in most common natural fibers with an onset at 270 °C for licorice waste, and at 290 °C for palm leaf one. The former was more abundant in cellulose (44% vs. 12% lignin), whilst the latter was richer in lignin (30% vs. 26% cellulose). In the composites, only a limited reduction of degradation temperature was observed for palm leaf waste addition and some dispersion issues are observed for licorice root, leading to fluctuating results. Tensile performance of the composites indicates some reduction with respect to the pure polymer in terms of tensile strength, though stabilizing between data with 5 and 10% filler. In contrast, Shore A hardness of both composites slightly increases with higher filler content, while in stiffness-driven applications licorice-based composites showed potential due to an increase up to 50% compared to neat PUA. In general terms, the fracture surfaces tend to become rougher with filler introduction, which indicates the need for optimizing interfacial adhesion.     

Insights into docking and scoring neuronal α4β2 nicotinic receptor agonists using molecular dynamics simulations and QM/MM calculations

A combined quantum mechanical (QM)‐polarized docking and molecular dynamics approach to study the binding mode and to predict the binding affinity of ligands acting at the α4β2‐nAChR is presented. The results obtained in this study indicate that the quantum mechanical/molecular mechanics docking protocol well describes the charge‐driven interactions occurring in the binding of nicotinic agonists, and it is able to represent the polarization effects on the ligand exerted by the surrounding atoms of the receptor at the binding site. This makes it possible to properly score agonists of α4β2‐nAChR and to reproduce the experimental binding affinity data with good accuracy, within a mean error of 2.2 kcal/mol. Moreover, applying the QM‐polarized docking to an ensemble of nAChR conformations obtained from MD simulations enabled us to accurately capture nAChR‐ligand induced‐fit effects. © 2009 Wiley Periodicals, Inc. J Comput Chem, 2009     

Self-assembled fluorescent chemosensors

Self-assembling and self-organizing methodologies are powerful tools for the "bottom-up" approach for the realization of complex structure with functional properties. Recently, this concept has been extended to the design of fluorescent chemosensors providing new exciting potentialities for the development of innovative sensing systems. This Concept Article deals mainly with this new approach and discusses its evolution, applications, and limitations.     

Lanthanide-based NMR: a tool to investigate component distribution in mixed-monolayer-protected nanoparticles

Gd(3+) ions, once bound to the monolayer of organic molecules coating the surface of gold nanoparticles, produce a paramagnetic relaxation enhancement (PRE) that broadens and eventually cancels the signals of the nuclear spins located nearby (within 1.6 nm distance). In the case of nanoparticles coated with mixed monolayers, the signals arising from the different coating molecules experience different PRE, depending on their distance from the binding site. As a consequence, observation of the signal broadening patterns provides direct information on the monolayer organization.