Fullerene-functionalized carbon nanotubes as improved optical limiting devices

We report the synthesis, characterization and optical limiting behavior of a nanohybrid built by grafting C₆₀-fullerenes on carbon nanotubes (CNTs). The nonlinear optical limiting properties of the CNT-C₆₀ complex were investigated at wavelengths where C₆₀ does not absorb. We found that the nanohybrid had superior performances to those of CNTs and fullerenes, either taken individually or as a mixture. This enhanced optical limitation of the nanohybrid suggests not only cooperative but also synergistic effects between the two carbon forms. A mechanism involving higher excitonic states of the CNTs formed by Auger recombination of low energy excitons is proposed.     

Inulin mixed esters crosslinked with 2-ethyl-hexyl-acrylate and their promotion as bio-based materials

New inulin-based materials were obtained by graft-copolymerization of inulin (poly-β(1 → 2)-fructoside) with 2-ethyl-hexyl acrylate. Inulin mixed esters were first synthesized by acylation using methacryloyl and palmitoyl chlorides. Further, these esters were copolymerized with 2-ethyl-hexyl acrylate in order to obtain bio-based crosslinked materials that could be used as commodity plastics and that would have biodegradable properties. The obtained products were characterized using FT-IR and ¹H NMR spectroscopies, thermogravimetry; differential scanning calorimetry, and activation energy for the degradation processes (using Kissinger method) was calculated. These biomaterials were also subjected to density measurement, tensile and torsion tests to evaluate their mechanical properties.     

Kinetics study on cnt‐supported RuKCo FTS catalyst in a fixed bed reactor

The rate of syngas (H₂/CO) consumption over a RuKCo/CNT Fischer–Tropsch synthesis (FTS) catalyst was measured in a fixed bed microreactor at 210–225°C, 2–3.5 MPa, H₂/CO feed molar ratios of 1–2.5, and gas hourly space velocity (GHSV) range of 2700–3600 h^?1. The data have been used to model the kinetics of the FTS reactions within the range of the studied conditions. One empirical power law model and four semi‐empirical kinetic models based on Langmuir–Hinshelwood‐type equation have been evaluated. The best fitting was obtained with the equation: similar to that proposed by Brötz et al. The estimated activation energy (E = 80–85 kJ/mol) is lower than that is reported in the literature. The validity of these results are restricted to fixed beds with the given catalyst in the tested conversion regime.     

In Situ X-ray Diffraction and Young's Modulus Measurement during Heat Treatment of High-Alumina Cement Castables

In situ Young's modulus measurements and synchrotron radiation-energy dispersive diffraction have been used to study changes in high-alumina castables subjected to heat treatment from room temperature to 1600°C. Particular attention was paid to the hydrate conversion process and the effects of high temperature.     

Polyamide 66 microspheres metallised with in situ synthesised gold nanoparticles for a catalytic application

A simple concept is proposed to metallise polyamide 66 (PA66) spherulite structures with in situ synthesised gold nanoparticles (Au NPs) using a wet chemical method. This cost-effective approach, applied to produce a PA66/Au NP hybrid material, offers the advantages of controlling the nanoparticle size, the size distribution and the organic-inorganic interactions. These are the key factors that have to be controlled to construct consistent Au nanostructures which are essential for producing the catalytic activities of interest. The hybrid materials obtained are characterised by means of scanning electron microscopy, transmission electron microscopy, attenuated total reflection-Fourier transform infrared spectrometry and X-ray diffraction spectrometry. The results show that PA66 microspheres obtained via the crystallisation process are coated with Au NPs of 13 nm in size. It was found that controlling the metal coordination is the key parameter to template the Au NPs on the spherulite surfaces. The preparation processes and the key factors leading to the formation of PA66 spherulites coated with Au NPs are discussed. Moreover, the efficiency of the coated spherulites as a potential catalyst is proved by demonstrating the reduction of methylene blue via UV-visible spectrometry.     

Thiol-ene “clickable” carbon-chain polymers based on diallyl cyclopropane-1,1-dicarboxylate

A novel type of clickable polymers with a very high local density of allyl side groups was developed. These polymers were obtained by the anionic ring-opening (co)polymerization of diallyl cyclopropane-1,1-dicarboxylate using as an initiating system a protic precursor whose acid–base reaction with the t-BuP₄ phosphazene base generated the initiator in situ. The obtained polymers display geminated allyl groups on every third carbon alongside the macromolecular backbone. Homopolymers as well as block and statistical copolymers have been synthesized, with controlled molecular weights and narrow molecular weight distributions. The coupling of mercaptans with the allyl CC double bonds has been investigated both thermally and photochemically, with the influence of the type of initiation on the efficiency of the polymer modification being discussed in comparison with other “clickable” systems. Further functionalization by several thiols was performed, leading to a range of functional poly(cyclopropane-1,1-dicarboxylate)s.     

Graded evolution of anisotropic microstructure during sintering from crystal-oriented powder compact

Anisotropic sintering, including shrinkage and grain growth, was examined for c-axis-oriented (Sr,Ca)₂NaNb₅O₁₅ (SCNN) ceramics, which were prepared by colloidal processing under a magnetic field. In the c-axis-oriented SCNN powder compact, shrinkage and grain growth along the c-axis were higher than those along the a-axis. The anisotropic microstructural development was clearly associated with anisotropic sintering shrinkage. X-ray diffraction, scanning electron microscopy, and energy back scattering diffraction showed that the grain growth of oriented particles by including random grains contribute to the development of the oriented microstructure. Finally, the highly crystal-oriented SCNN ceramics with a densified microstructure were obtained through anisotropic sintering. These results clearly showed the potential to develop a well-defined anisotropic microstructure during sintering by designing and controlling the particle packing structure in a powder compact.     

Bifunctional DNA Duplexes Permit Efficient Incorporation of pH Probes into Liposomes

Enzyme-mediated proton transport across biological membranes is critical for many vital cellular processes. pH-sensitive fluorescent dyes are an indispensable tool for investigating the molecular mechanism of proton-translocating enzymes. Here, we present a novel strategy to entrap pH-sensitive probes in the lumen of liposomes that has several advantages over the use of soluble or lipid-coupled probes. In our approach, the pH sensor is linked to a DNA oligomer with a sequence complementary to a second oligomer modified with a lipophilic moiety that anchors the DNA conjugate to the inner and outer leaflets of the lipid bilayer. The use of DNA as a scaffold allows subsequent selective enzymatic removal of the probe in the outer bilayer leaflet. The method shows a high yield of insertion and is compatible with reconstitution of membrane proteins by different methods. The usefulness of the conjugate for time-resolved proton pumping measurements was demonstrated by using two large membrane protein complexes.     

The Arabidopsis Mitochondrial Glutaredoxin GRXS15 Provides [2Fe-2S] Clusters for ISCA-Mediated [4Fe-4S] Cluster Maturation

Iron-sulfur (Fe-S) proteins are crucial for many cellular functions, particularly those involving electron transfer and metabolic reactions. An essential monothiol glutaredoxin GRXS15 plays a key role in the maturation of plant mitochondrial Fe-S proteins. However, its specific molecular function is not clear, and may be different from that of the better characterized yeast and human orthologs, based on known properties. Hence, we report here a detailed characterization of the interactions between Arabidopsis thaliana GRXS15 and ISCA proteins using both in vivo and in vitro approaches. Yeast two-hybrid and bimolecular fluorescence complementation experiments demonstrated that GRXS15 interacts with each of the three plant mitochondrial ISCA1a/1b/2 proteins. UV-visible absorption/CD and resonance Raman spectroscopy demonstrated that coexpression of ISCA1a and ISCA2 resulted in samples with one [2Fe-2S]²⁺ cluster per ISCA1a/2 heterodimer, but cluster reconstitution using as-purified [2Fe-2S]-ISCA1a/2 resulted in a [4Fe-4S]²⁺ cluster-bound ISCA1a/2 heterodimer. Cluster transfer reactions monitored by UV-visible absorption and CD spectroscopy demonstrated that [2Fe-2S]-GRXS15 mediates [2Fe-2S]²⁺ cluster assembly on mitochondrial ferredoxin and [4Fe-4S]²⁺ cluster assembly on the ISCA1a/2 heterodimer in the presence of excess glutathione. This suggests that ISCA1a/2 is an assembler of [4Fe-4S]²⁺ clusters, via two-electron reductive coupling of two [2Fe-2S]²⁺ clusters. Overall, the results provide new insights into the roles of GRXS15 and ISCA1a/2 in effecting [2Fe-2S]²⁺ to [4Fe-4S]²⁺ cluster conversions for the maturation of client [4Fe-4S] cluster-containing proteins in plants.     

Reactivity between liquid Si or Si alloys and graphite

The fundamental issues of the reaction at liquid Si/graphite interfaces between Si melting point (1412 °C) and 1600 °C are studied on the basis of results obtained with polycrystalline graphite concerning the growth kinetics of the interfacial reaction layer and the microstructure and morphology of this layer. Experiments were also performed using vitreous carbon substrates. Results are also reported for Si–Al alloys at 1000 °C. The elementary process controlling the growth kinetics is determined and a model is proposed to describe the different stages of the interfacial reaction.