Shape-persistent octanuclear zinc salen clusters: synthesis, characterization, and catalysis

We describe a selective and template-controlled synthesis of a series of Zn(8) metal complexes based on a bis-nucleating salen ligand scaffold. Our results, a combination of X-ray analysis and solution studies, show that discrete, shape-persistent metal clusters can be prepared in high yield. Their activity in organic carbonate catalysis is a function of the metal-connecting fragment present in the exterior of the cluster complex. The high stability of the clusters has been confirmed by (1)H, (13)C (DEPTQ) and DOSY NMR, gel permeation chromatography, high-performance liquid chromatography, and mass spectrometry.     

Multiplexed arrays of chemosensors by parallel dip-pen nanolithography

Miniaturized combined arrays of three different pH indicators allowing for sensitive, robust and broad-range acidity detection are prepared by parallel dip-pen nanolithography, which proves the potential of this technique to fabricate multiplexed platforms at the micro- and nanoscale that can act as sensors.     

Environmentally-safe bimetallic Ag@Co magnetic nanocomposites with antimicrobial activity

In this communication we describe the synthesis, characterization and evaluation of the bactericide activity of a superparamagnetic bimetallic Ag/Co polymeric nanocomposite material for the treatment of bacteria contaminated aqueous solutions.     

Carleson Measures,Riemann–Stieltjes and Multiplication Operators on a General Family of Function Spaces

Let μ be a nonnegative Borel measure on the unit disk of the complex plane. We characterize those measures μ such that the general family of spaces of analytic functions, F(p, q, s), which contain many classical function spaces, including the Bloch space, BMOA and the Q _s spaces, are embedded boundedly or compactly into the tent-type spaces ${T^{\infty}_{p, s}(\mu)}$ . The results are applied to characterize boundedness and compactness of Riemann–Stieltjes operators and multiplication operators on F(p, q, s).     

Optical forces induced by metal nanoparticle clusters

The strong field localization generated between closely placed metal particles excited by electromagnetic radiation induces intense forces on small polarizable objects. In this study we investigate the optical forces that can be generated in the vicinity of metal nanoparticle clusters using fully electrodynamic numerical simulations. The influence of the cluster configuration as well as of the excitation parameters is analyzed.     

Elucidating the 2D Magnetic Topology of the ‘Metal–Radical’ TTTA⋅Cu(hfac)2 System

The TTTA ? Cu(hfac)₂ polymer ( 1 ; in which TTTA=1,3,5‐trithia‐2,4,6‐triazapentalenyl, and hfac=(1,1,1,5,5,5)‐hexafluoroacetylacetonate) is one of the most prominent examples of the rational use of the ‘metal–radical’ synthetic approach to achieve ferromagnetic interactions. Experimentally, the magnetic topology of 1 could not be fully deciphered. Herein, the first‐principles bottom‐up procedure was applied to elucidate the nature and strength of the magnetic J_AB exchange interactions present in 1 . The computed J_AB values give rise to a 2D magnetic topology of ferromagnetic dimers (+11.9 cm^?1) coupled through weaker antiferromagnetic interactions (?3.0 and ?3.2 cm^?1) in two different spatial directions. The hitherto unknown origin of the antiferromagnetic interdimer interactions is thus unveiled. By using the 2D magnetic topology, the agreement between calculated and experimental χT(T) data is extraordinary. In the metal–radical TTTA ? Cu(hfac)₂ compound, the computational model transcends the local dimer cluster model owing to strong interactions between metal centers and organic radicals, thereby creating a de facto biradical. In addition, it is shown that the magnetic topology cannot be inferred from the polymeric [TTTA ??? Cu(hfac)₂]_n crystal motif, that is, from its chemical coordination pattern. Instead, one should think in terms of magnetic building blocks, namely, the de facto biradicals.     

A Self‐Improved Water‐Oxidation Catalyst: Is One Site Really Enough?

The homogeneous catalysis of water oxidation by transition‐metal complexes has experienced spectacular development over the last five years. Practical energy‐conversion schemes, however, require robust catalysts with large turnover frequencies. Herein we introduce a new oxidatively rugged and powerful dinuclear water‐oxidation catalyst that is generated by self‐assembly from a mononuclear catalyst during the catalytic process. Our kinetic and DFT computational analysis shows that two interconnected catalytic cycles coexist while the mononuclear system is slowly and irreversibly converted into the more stable dinuclear system: an extremely robust water‐oxidation catalyst that does not decompose over extended periods of time.     

Magnetic actuator for the control and mixing of magnetic bead-based reactions on-chip

While magnetic bead (MB)-based bioassays have been implemented in integrated devices, their handling on-chip is normally either not optimal—i.e. only trapping is achieved, with aggregation of the beads—or requires complex actuator systems. Herein, we describe a simple and low-cost magnetic actuator to trap and move MBs within a microfluidic chamber in order to enhance the mixing of a MB-based reaction. The magnetic actuator consists of a CD-shaped plastic unit with an arrangement of embedded magnets which, when rotating, generate the mixing. The magnetic actuator has been used to enhance the amplification reaction of an enzyme-linked fluorescence immunoassay to detect Escherichia coli O157:H7 whole cells, an enterohemorrhagic strain, which have caused several outbreaks in food and water samples. A 2.7-fold sensitivity enhancement was attained with a detection limit of 603?colony-forming units (CFU) /mL, when employing the magnetic actuator. Graphical Abstract

?     

Stable carbon and nitrogen isotopes and quality traits of fossil cereal grains provide clues on sustainability at the beginnings of Mediterranean agriculture

We present a novel approach to study the sustainability of ancient Mediterranean agriculture that combines the measurement of carbon isotope discrimination (Delta(13)C) and nitrogen isotope composition (delta(15)N) along with the assessment of quality traits in fossil cereal grains. Charred grains of naked wheat and barley were recovered in Los Castillejos, an archaeological site in SE Spain, with a continuous occupation of ca. 1500 years starting soon after the origin of agriculture (ca. 4000 BCE) in the region. Crop water status and yield were estimated from Delta(13)C and soil fertility and management practices were assessed from the delta(15)N and N content of grains. The original grain weight was inferred from grain dimensions and grain N content was assessed after correcting N concentration for the effect of carbonisation. Estimated water conditions (i.e. rainfall) during crop growth remained constant for the entire period. However, the grain size and grain yield decreased progressively during the first millennium after the onset of agriculture, regardless of the species, with only a slight recovery afterwards. Minimum delta(15)N values and grain N content were also recorded in the later periods of site occupation. Our results indicate a progressive loss of soil fertility, even when the amount of precipitation remained steady, thereby indicating the unsustainable nature of early agriculture at this site in the Western Mediterranean Basin. In addition, several findings suggest that barley and wheat were cultivated separately, the former being restricted to marginal areas, coinciding with an increased focus on wheat cultivation.