Drastic influence of minor Fe or Co additions on the glass forming ability, martensitic transformations and mechanical properties of shape memory Zr-Cu-Al bulk metallic glass composites.

The microstructure and mechanical properties of Zr48Cu48 - x Al4M x (M ≡ Fe or Co, x = 0, 0.5, 1 at.%) metallic glass (MG) composites are highly dependent on the amount of Fe or Co added as microalloying elements in the parent Zr48Cu48Al4 material. Addition of Fe and Co promotes the transformation from austenite to martensite during the course of nanoindentation or compression experiments, resulting in an enhancement of plasticity. However, the presence of Fe or Co also reduces the glass forming ability, ultimately causing a worsening of the mechanical properties. Owing to the interplay between these two effects, the compressive plasticity for alloys with x = 0.5 (5.5% in Zr48Cu47.5Al4Co0.5 and 6.2% in Zr48Cu47.5Al4Fe0.5) is considerably larger than for Zr48Cu48Al4 or the alloys with x = 1. Slight variations in the Young's modulus (around 5-10%) and significant changes in the yield stress (up to 25%) are also observed depending on the composition. The different microstructural factors that have an influence on the mechanical behavior of these composites are investigated in detail: (i) co-existence of amorphous and crystalline phases in the as-cast state, (ii) nature of the crystalline phases (austenite versus martensite content), and (iii) propensity for the austenite to undergo a mechanically-driven martensitic transformation during plastic deformation. Evidence for intragranular nanotwins likely generated in the course of the austenite-martensite transformation is provided by transmission electron microscopy. Our results reveal that fine-tuning of the composition of the Zr-Cu-Al-(Fe,Co) system is crucial in order to optimize the mechanical performance of these bulk MG composites, to make them suitable materials for structural applications.

Hydrophobic gold nanoparticle self-assembly with phosphatidylcholine lipid: membrane-loaded and janus vesicles.

Hybrids of hydrophobic sub-2-nm-diameter dodecanethiol-coated Au nanoparticles and phosphatidylcholine (PC) lipid vesicles made by extrusion were examined by cryogenic transmission electron microscopy (cryoTEM). The nanoparticles loaded the vesicles as a dense monolayer in the hydrophobic core of the lipid bilayer, without disrupting their structure. Nanoparticle-vesicle hybrids could also be made by a dialysis process, mixing preformed vesicles with detergent-stabilized nanoparticles, but this approach led to vesicles only partially loaded with nanoparticles that segregated into hemispherical domains, forming a Janus vesicle-nanoparticle hybrid structure.

QDs versus Alexa: reality of promising tools for immunocytochemistry.

BACKGROUND: The unique photonic properties of the recently developed fluorescent semiconductor nanocrystals (QDs) have made them a potential tool in biological research. However, QDs are not yet a part of routine laboratory techniques. Double and triple immunocytochemistries were performed in HeLa cell cultures with commercial CdSe QDs conjugated to antibodies. The optical characteristics, due to which QDs can be used as immunolabels, were evaluated in terms of emission spectra, photostability and specificity. RESULTS: QDs were used as secondary and tertiary antibodies to detect beta-tubulin (microtubule network), GM130 (Golgi complex) and EEA1 (endosomal system). The data obtained were compared to homologous Alexa Fluor 594 organic dyes. It was found that QDs are excellent fluorochromes with higher intensity, narrower bandwidth values and higher photostability than Alexa dyes in an immunocytochemical process. In terms of specificity, QDs showed high specificity against GM130 and EEA1 primary antibodies, but poor specificity against beta-tubulin. Alexa dyes showed good specificity for all the targets tested. CONCLUSION: This study demonstrates the great potential of QDs, as they are shown to have superior properties to Alexa dyes. Although their specificity still needs to be improved in some cases, QDs conjugated to antibodies can be used instead of organic molecules in routine immunocytochemistry.

Facile in situ synthesis of BiOCl nanoplates stacked to highly porous TiO2: a synergistic combination for environmental remediation.

A novel nanocomposite material made of two-dimensional BiOCl nanoplates assembled into highly porous titania has been successfully prepared following a facile sol-gel reaction. Both the TiO2 (anatase) and BiOCl components are crystalline as demonstrated by X-ray diffraction and transmission electron microscopy analyses. TiO2 exhibits a highly porous network and possesses a small crystallite size, whereas BiOCl forms micrometer-sized plates with nanometer thicknesses. Aqueous photocatalytic activity tests with this novel material have been performed on photodegradation of Rhodamine B under ultraviolet-visible light irradiation. Interestingly, the attachment of the BiOCl nanoplates to the TiO2 network significantly enhances the photocatalytic activity of the material compared to that of pure TiO2 due to the formation of BiOCl/TiO2 heterojunctions. Thus, this pertinent synergistic combination of TiO2 and BiOCl proves to be a promising strategy for the large-scale production of a new generation of photocatalysts with excellent properties for the degradation of organic pollutants.

Mesoporous Titania Powders: The Role of Precursors, Ligand Addition and Calcination Rate on Their Morphology, Crystalline Structure and Photocatalytic Activity.

We evaluate the influence of the use of different titania precursors, calcination rate, and ligand addition on the morphology, texture and phase content of synthesized mesoporous titania samples, parameters which, in turn, can play a key role in titania photocatalytic performances. The powders, obtained through the evaporation-induced self-assembly method, are characterized by means of ex situ X-Ray Powder Diffraction (XRPD) measurements, N2 physisorption isotherms and transmission electron microscopy. The precursors are selected basing on two different approaches: the acid-base pair, using TiCl4 and Ti(OBu)4, and a more classic route with Ti(OiPr)4 and HCl. For both precursors, different specimens were prepared by resorting to different calcination rates and with and without the addition of acetylacetone, that creates coordinated species with lower hydrolysis rates, and with different calcination rates. Each sample was employed as photoanode and tested in the water splitting reaction by recording I-V curves and comparing the results with commercial P25 powders. The complex data framework suggests that a narrow pore size distribution, due to the use of acetylacetone, plays a major role in the photoactivity, leading to a current density value higher than that of P25.

Controlled 3D-coating of the pores of highly ordered mesoporous antiferromagnetic Co3O4 replicas with ferrimagnetic Fe(x)Co(3-x)O4 nanolayers.

The controlled filling of the pores of highly ordered mesoporous antiferromagnetic Co3O4 replicas with ferrimagnetic FexCo3-xO4 nanolayers is presented as a proof-of-concept toward the integration of nanosized units in highly ordered, heterostructured 3D architectures. Antiferromagnetic (AFM) Co3O4 mesostructures are obtained as negative replicas of KIT-6 silica templates, which are subsequently coated with ferrimagnetic (FiM) FexCo3-xO4 nanolayers. The tuneable magnetic properties, with a large exchange bias and coercivity, arising from the FiM/AFM interface coupling, confirm the microstructure of this novel two-phase core-shell mesoporous material. The present work demonstrates that ordered functional mesoporous 3D-materials can be successfully infiltrated with other compounds exhibiting additional functionalities yielding highly tuneable, versatile, non-siliceous based nanocomposites.

The use of quantum dots for immunochemistry applications.

Immunocytochemistry and histochemistry are two most valuable immunochemistry techniques routinely used in biological laboratories. These techniques rely on the use of antibodies to label epitopes of interest in cells. At present, there is a wide range of commercially available organic dyes for labeling antibodies. However, limited extinction coefficients of organic dyes often make it difficult to achieve the optimal exposure and therefore fluorescence detection limit. Quantum dots (QDs) are fluorescent semiconductor nanocrystals which are advantageous over the organic fluorescent dyes in many aspects, principally their long-term luminescence stability, high brightness, and multicolor detection. Here, we describe the use of QDs for immunocytochemistry applications. We used three different antibodies-anti-ß-tubulin monoclonal antibody for visualizing the microtubule network, the GM130 antibody for staining the Golgi complex, and the EEA1 antibody for detecting the endosomal system. We use the anti-mouse IgG antibody directly conjugated to QD655 quantum dots or anti-mouse IgG conjugated to biotin for tertiary detection with streptavidin-conjugated QD655.