Water-dispersible sugar-coated iron oxide nanoparticles. An evaluation of their relaxometric and magnetic hyperthermia properties

Synthesis of functionalized magnetic nanoparticles (NPs) for biomedical applications represents a current challenge. In this paper we present the synthesis and characterization of water-dispersible sugar-coated iron oxide NPs specifically designed as magnetic fluid hyperthermia heat mediators and negative contrast agents for magnetic resonance imaging. In particular, the influence of the inorganic core size was investigated. To this end, iron oxide NPs with average size in the range of 4-35 nm were prepared by thermal decomposition of molecular precursors and then coated with organic ligands bearing a phosphonate group on one side and rhamnose, mannose, or ribose moieties on the other side. In this way a strong anchorage of the organic ligand on the inorganic surface was simply realized by ligand exchange, due to covalent bonding between the Fe(3+) atom and the phosphonate group. These synthesized nanoobjects can be fully dispersed in water forming colloids that are stable over very long periods. Mannose, ribose, and rhamnose were chosen to test the versatility of the method and also because these carbohydrates, in particular rhamnose, which is a substrate of skin lectin, confer targeting properties to the nanosystems. The magnetic, hyperthermal, and relaxometric properties of all the synthesized samples were investigated. Iron oxide NPs of ca. 16-18 nm were found to represent an efficient bifunctional targeting system for theranostic applications, as they have very good transverse relaxivity (three times larger than the best currently available commercial products) and large heat release upon application of radio frequency (RF) electromagnetic radiation with amplitude and frequency close to the human tolerance limit. The results have been rationalized on the basis of the magnetic properties of the investigated samples.     

The atomic structural dynamics of γ-Al2O3 supported Ir-Pt nanocluster catalysts prepared from a bimetallic molecular precursor: a study using aberration-corrected electron microscopy and X-ray absorption spectroscopy

This study describes a prototypical, bimetallic heterogeneous catalyst: compositionally well-defined Ir-Pt nanoclusters with sizes in the range of 1-2 nm supported on γ-Al(2)O(3). Deposition of the molecular bimetallic cluster [Ir(3)Pt(3)(μ-CO)(3)(CO)(3)(η-C(5)Me(5))(3)] on γ-Al(2)O(3), and its subsequent reduction with hydrogen, provides highly dispersed supported bimetallic Ir-Pt nanoparticles. Using spherical aberration-corrected scanning transmission electron microscopy (C(s)-STEM) and theoretical modeling of synchrotron-based X-ray absorption spectroscopy (XAS) measurements, our studies provide unambiguous structural assignments for this model catalytic system. The atomic resolution C(s)-STEM images reveal strong and specific lattice-directed strains in the clusters that follow local bonding configurations of the γ-Al(2)O(3) support. Combined nanobeam diffraction (NBD) and high-resolution transmission electron microscopy (HRTEM) data suggest the polycrystalline γ-Al(2)O(3) support material predominantly exposes (001) and (011) surface planes (ones commensurate with the zone axis orientations frequently exhibited by the bimetallic clusters). The data reveal that the supported bimetallic clusters exhibit complex patterns of structural dynamics, ones evidencing perturbations of an underlying oblate/hemispherical cuboctahedral cluster-core geometry with cores that are enriched in Ir (a result consistent with models based on surface energetics, which favor an ambient cluster termination by Pt) due to the dynamical responses of the M-M bonding to the specifics of the adsorbate and metal-support interactions. Taken together, the data demonstrate that strong temperature-dependent charge-transfer effects occur that are likely mediated variably by the cluster-support, cluster-adsorbate, and intermetallic bonding interactions.     

Odour-causing organic compounds in wastewater treatment plants: evaluation of headspace solid-phase microextraction as a concentration technique

Odorous emissions from wastewater collection systems and treatment facilities affecting quality of life have given local populations reasons to complain for decades. In order to characterise the composition of such malodorous emissions, a method based on headspace solid-phase microextraction (HS-SPME) and gas chromatography coupled to mass spectrometry (GC-MS) has been developed to determine a list of compounds belonging to different chemical families, which have been previously described as potentially responsible for odour complaints, in wastewater matrices. Some parameters affecting the chromatographic behaviour of the target compounds were studied (e.g. splitless time). Experimental conditions affecting the extraction process (temperature, time and salt content) were evaluated by applying a factorial design at two levels. Using a DVB/CAR/PDMS fibre and the optimised HS-SPME conditions, calibration curves were constructed with detection limits in the range of 0.003-0.6 μg L(-1). Recovery values higher than 70% and relative standard deviation values between 5 and 16% (n=5) were obtained for all compounds and found to be satisfactory. In wastewater samples, a decrease in the concentration of the analysed compounds through the different treatments was observed. Most of the target analytes were found in influent samples while only octanal and carvone were detected in samples from the plant effluent.     

Synthesis of silver nanoparticles and antimony oxide nanocrystals by pulsed laser ablation in liquid media

Pulsed laser ablation in liquid media (PLALM) is a prominent technique for the controlled fabrication of nanomaterials via rapid reactive quenching of ablated species at the interface between the plasma and liquid. Results on nanoparticles and nanocrystals formed by PLALM of silver (Ag) and antimony (Sb) solid targets in different liquid environments (Sodium Dodecyl Sulfate, distilled water) are presented. These experiments were done by irradiating solid targets of Ag and Sb with a nanosecond pulsed Nd:YAG laser output of wavelength 532 nm. Nanoparticles of silver and nanocrystals of antimony oxide (Sb₂O₃) obtained were characterized using UV-Vis spectrometry, Scanning Electron Microscopy (SEM), transmission electron microscopy (TEM), X-ray Energy Dispersion Analysis (EDAX) and X-ray diffractometry (XRD). The morphology of nanomaterials formed is studied as a function of surfactant environment. The silver nanoparticles obtained were spherical of size in the order of 10–35 nm in solution of SDS having different concentrations. In case of the Sb target, ablation was performed in two different molarities of SDS solution and distilled water. Nanocrystals of Sb₂O₃ in powder form having cubic and orthorhombic phases were formed in SDS solution and as fibers of nanocrystals of cubic Sb₂O₃ in distilled water.     

Confining surface state electrons in less than two dimensions: A spectroscopic study

We observe the partial confinement of the twodimensional electron gas of ans-p-like surface state by the regular step distribution of several vicinal Cu(111) surfaces. The spatial distribution of the surface state is visualized by scanning tunneling microscopy. Local tunneling spectroscopy reveals a shift of the maximum of the density of states of the surface state towards the Fermi level, which correlates with the size of the terraces. The average shift is also measured by angle-resolved photoemission and found to be consistent with a one-dimensional Kronig-Penney model.     

Automated parallel anionic polymerizations: Enhancing the possibilities of a widely used technique in polymer synthesis

Anionic polymerization techniques have been implemented successfully in a commercial automated synthesizer. The main problems for a successful adaptation of the experimental technique in the automated synthesizer are addressed, as well as some simple potential applications, such as the anionic polymerization of styrene, isoprene, and methyl methacrylate. The obtained results were reproducible and in concordance with literature knowledge. The apparent rate constant of the anionic polymerization of styrene in cyclohexane initiated by sec‐butyllithium could be determined at two different concentrations of the monomer and initiator in a temperature range of 10–60 °C. All the synthesis and characterization experiments of the polymers were performed within a short time period. Moreover, the syntheses of poly(styrene‐b‐isoprene) and poly(styrene‐b‐methyl methacrylate) block copolymers were also successfully carried out within the automated synthesizer. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 4151–4160, 2005     

Structural properties of PbTiO3 and PbZrxTi1−xO3: A quantum‐chemical study

We investigate the structural and electronic properties of pure and Zr‐doped PbTiO₃ crystals. The nature of atomic relaxation around the Zr impurity is studied through quantum‐chemical simulations based on the Hartree–Fock theory and a periodic large unit cell model adopted within the so‐called intermediate neglect of differential overlap approximation. The most stable defect configurations are predicted for different impurity concentrations. The results obtained are compared with those from other theoretical studies and a number of experimental measurements carried out on this technologically important perovskite‐type crystal. © 2001 John Wiley & Sons, Inc. Int J Quantum Chem, 2001     

The phase diagram of oxygen ordering in YBa2Cu3O6+δ: The nine point cluster approximation

The thermodynamics of oxygen ordering in the basal plane of YBa₂Cu₃O_6+δ is studied within the nine point approximation of the cluster variation method. The phenomena is modeled by an Ising model with nearest-and next-nearest-neighbor interactions. The composition (δ) versus the temperature (T) phase diagram is calculated and compared with results obtained by using smaller clusters and the Monte Carlo method. The composition dependence of the order parameters for various temperatures is also presented.     

The synthesis of 3-bromo-2,4,5-trifluorobenzoic acid and its conversion to 8-bromoquinolonecarboxylic acids

A series of 8-bromo-4-oxo-3-quinolinecarboxylic acids was prepared via the borate ester, 8 . The key intermediate in the synthesis of the final products 10a-10d was 3-bromo-2,4,5-trifluorobenzoic acid ( 3 ), conveniently prepared in two steps from the known oxazoline, 1 . The preparation of 10a-10d is a significant improvement of the literature procedure currently available for the synthesis of these compounds.