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The vascular bioactivity/safety of nanomaterials is typically evaluated by animal testing, which is of low throughput and does not account for biological differences between animals and humans such as ageing, metabolism and disease profiles. The development of personalized human in vitro platforms to evaluate the interaction of nanomaterials with the vascular system would be important for both therapeutic and regenerative medicine. A library of 30 nanoparticle (NP) formulations, in use in imaging, antimicrobial and pharmaceutical applications, was evaluated in a reporter zebrafish model of vasculogenesis and then tested in personalized humanized models composed of human-induced pluripotent stem cell (hiPSC)-derived endothelial cells (ECs) with "young" and "aged" phenotypes in 3 vascular network formats: 2D (in polystyrene dish), 3D (in Matrigel) and in a blood vessel on a chip. As a proof of concept, vascular toxicity was used as the main readout. The results show that the toxicity profile of NPs to hiPSC-ECs was dependent on the "age" of the endothelial cells and vascular network format. hiPSC-ECs were less susceptible to the cytotoxicity effect of NPs when cultured in flow than in static conditions, the protective effect being mediated, at least in part, by glycocalyx. Overall, the results presented here highlight the relevance of in vitro hiPSC-derived vascular systems to screen vascular nanomaterial interactions.

The fabrication of ultrathin single-crystal Au nanowires with high aspect ratio and that are stable in air is challenging. Recently, a simple wet-chemical approach using oleylamine has been reported for the synthesis of Au nanowires with micrometer length and 2 nm in diameter. Despite efforts to understand the mechanism of the reaction, an ultimate question about the role of oxygen (O(2)) during the synthesis remained unclear. Here we report that the synthesis of ultrathin Au nanowires employing oleylamine is strongly affected by the amount of O(2) absorbed in the reaction solution. Saturating the solution with O(2) leads to both a high-yield production of nanowires and an increase in their length. Nanowires with diameters of about 2 nm and lengths of 8 μm, which corresponds to an aspect ratio of approximately 4000, were produced. The role of oxygen is attributed to the enhanced oxidation of twin defects on Au nanoparticles formed in the first stage of the reaction. Understanding the role of oxidative etching is crucial to significantly increasing the yield and the length of ultrathin Au nanowires., (Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Gold nanoparticles are widely used in biomedical imaging and diagnostic tests. Based on their established use in the laboratory and the chemical stability of Au(0), gold nanoparticles were expected to be safe. The recent literature, however, contains conflicting data regarding the cytotoxicity of gold nanoparticles. Against this background a systematic study of water-soluble gold nanoparticles stabilized by triphenylphosphine derivatives ranging in size from 0.8 to 15 nm is made. The cytotoxicity of these particles in four cell lines representing major functional cell types with barrier and phagocyte function are tested. Connective tissue fibroblasts, epithelial cells, macrophages, and melanoma cells prove most sensitive to gold particles 1.4 nm in size, which results in IC(50) values ranging from 30 to 56 microM depending on the particular 1.4-nm Au compound-cell line combination. In contrast, gold particles 15 nm in size and Tauredon (gold thiomalate) are nontoxic at up to 60-fold and 100-fold higher concentrations, respectively. The cellular response is size dependent, in that 1.4-nm particles cause predominantly rapid cell death by necrosis within 12 h while closely related particles 1.2 nm in diameter effect predominantly programmed cell death by apoptosis.

Advancing the synthesis of HfO2 nanocrystals, a refined anhydrous protocol that enables kinetic trapping of the metastable tetragonal phase and modulates twinning defects in anisotropically grown monoclinic nanoprisms is presented. This evolved sol–gel approach examines the role of the capping agent tri‐n‐octylphosphine oxide (TOPO) and introduces a novel heating strategy with sequential growth stages. Replacement of TOPO with triphenylphosphine oxide (TPPO) leads to the formation of prismatic hafnia nanocrystals exhibiting pristine {011}‐facets of the monoclinic phase. Furthermore, a hot‐injection inspired heating approach yields sub‐4 nm isotropic HfO2 nanocrystals in the tetragonal phase, bypassing the need for aliovalent cation species. In contrast, a heat‐up approach culminates in the generation of well‐characterized HfO2 nanorods. With sophisticated transmission electron microscopy analysis and the Wulff construction method, insights into the structural nucleation of nanoparticle growth are provided. This synthesis offers exceptional control and facilitates the formation of self‐assemblies akin to liquid crystals, opening the door for new applications with nanocolloidal HfO2. [ABSTRACT FROM AUTHOR]

Chemically synthesized gold nanoparticles (AuNPs) have attracted much interest for application in various technologically relevant fields including nanoelectronics. In this particular research area, the most promising approach to take full advantage of the tunability in size, shape, and ligand composition of nanoparticles is the integration of a well‐defined number of AuNPs into a nanoscale device. This short review highlights recent progress in the introduction of AuNP into nanoelectronic circuitry by means of selected examples, that demonstrate a "proof‐of‐concept". Synthetic concepts to obtain isotropic and Janus‐like particles as well as lithographic techniques that allow for the fabrication of nanoelectrode structures, which enable the electrical addressing of individual nanoparticles, are presented. A particular focus of this work is the question of how distinct molecular properties can be addressed in a technologically applicable device geometry by controlling the molecular functionalities in the proximity of semiconductor technology. [ABSTRACT FROM AUTHOR]

We present a detailed structural discussion of [Au8(PPh3)8](NO3)2, crystallized as a CH2Cl2 solvate. Its structure is compared with closely related triphenylphosphine-stabilized gold clusters. Characterization by optical extinction spectroscopy, luminescence spectroscopy, voltammetry and DFT calculations was performed to determine the electronic HOMO-LUMO gap. Comparison of its characteristic energies with those of structurally related clusters revealed that the evolution of the HOMO-LUMO gap does not follow a simple scaling law but depends on specific structural features. [ABSTRACT FROM AUTHOR]

It is of urgent need to identify the exact physico-chemical characteristics which allow maximum uptake and accumulation in secondary target organs of nanoparticulate drug delivery systems after oral ingestion. We administered radiolabelled gold nanoparticles in different sizes (1.4-200 nm) with negative surface charge and 2.8 nm nanoparticles with opposite surface charges by intra-oesophageal instillation into healthy adult female rats. The quantitative amount of the particles in organs, tissues and excrements was measured after 24 h by gamma-spectroscopy. The highest accumulation in secondary organs was mostly found for 1.4 nm particles; the negatively charged particles were accumulated mostly more than positively charged particles. Importantly, 18 nm particles show a higher accumulation in brain and heart compared to other sized particles. No general rule accumulation can be made so far. Therefore, specialized drug delivery systems via the oral route have to be individually designed, depending on the respective target organ. [ABSTRACT FROM AUTHOR]

The present study relates to the applicability of silicon nanoparticles as basic component in printing inks for the fabrication of printable electronic devices. It is systematically investigated, how the surface functionalization of silicon nanoparticles with 1-alkenes affects the electrical properties of thin films made of them. Therefore, films of as-prepared silicon nanoparticles with a size of 42 nm as well as freshly etched ones, both terminated with hydrogen, are compared with films of silicon nanoparticles functionalized with n-octene, n-dodecene, allylmercaptan, and allylamine, respectively. It is found, that the activation energy of the electron transport through the films is in the range of 0.5 eV and scales with the polarity of the functionalization. [ABSTRACT FROM AUTHOR]

Abstract: Volume-doped CoTiO3 was synthesized via the polyol method. As volume dopants Gd, Ho, K, La, Li, Na, Pb, Sb, and Sm with a concentration of 2at.% were applied. By X-ray diffraction (XRD) materials structure was confirmed, while the materials morphology was imaged using scanning electron microscopy (SEM). Thick films of the nanocrystalline material were applied with a laboratory robotic system to a 8×8 multielectrode substrate. We show that the p-type semiconducting material doped with various metals is applicable for the fast detection of ethanol and propylene. The volume dopants affect the sensing and response behavior of the base material. [Copyright &y& Elsevier]

Abstract: p-Type semiconducting nanocrystalline CoTiO3:La (2at.%) was synthesized via polyol method. X-ray diffraction (XRD) was used to confirm the materials structure. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used to image the materials morphology. Thick films of the nanocrystalline material were applied with a laboratory roboting system to an 8×8 multielectrode substrate, developed for high-throughput impedance spectroscopy (HTIS). With this method it was shown that the base material doped with various metals (Au, Ce, Ir, Pd, Pt, Rh, Ru) in different concentrations (0.2–0.6at.%) is applicable for the fast detection of ethanol, propylene and NO2, depending on the surface doping and the operation temperature. [Copyright &y& Elsevier]

The article focuses on the how chemically tailored gold nanoparticles may serve as a model system for the evaluation of size dependency of cellular responses. It adds that dimensionality and aspect ratio also need to considered in measuring toxicity of nanoparticles. It notes that gold nanoparticles inside the cell nucleus may provide interruptions with deoxyribonucleic acid (DNA) transcription and replication. It mentions that nanoparticles can enhance biological signaling by stimulating the clustering of low-affinity ligands on scaffolds.

Resistive switching (RS) for nonvolatile data storage is a highly relevant field of research. Up to now, RS devices are fabricated via semiconductor processing technologies. This poses the question of whether integration of chemically tailored nanoparticles, either consisting of valence change or phase change materials, can be integrated in nanoelectrode configurations in order to explore their functionality for RS applications. This review discusses the RS properties of such nanoparticles by means of selected examples of both nanoparticle assemblies as well as on the individual particle level. Although this field of research is rather unexplored, it becomes evident that chemically tailored nanoparticles bear great potential for RS applications. [ABSTRACT FROM AUTHOR]

Abstract: Spinel iron oxide nanoparticles of sizes from 12 to 60nm have been prepared via a hydrothermal synthesis. Thick films of the Fe3−x O4 nanoparticles deposited on interdigital electrodes were applied as resistive gas sensors. The electrical and gas sensing properties were characterized by impedance spectroscopy using multielectrode substrates. The reducing analytes CH4, NO, H2 and NH3 in N2 as a reference were applied in order to investigate the sensor response, the selectivity and the recovery behavior at temperature between 50°C and 300°C. The materials exhibit good sensor responses towards NH3 with low cross sensitivities towards H2 and NO at 250°C. A linearly increasing sensor response towards NH3 and H2 with decreasing particle size was found. [Copyright &y& Elsevier]

Abstract We describe a facile and simple solid-state thermolysis route for the preparation of Co, Ni, and Fe phosphide nanoparticles embedded in amorphous carbon using an organometallic complex. This was achieved by using a suitable organometallic complex in a single step synthetic route without using any solvent or catalyst. The advantage of using such precursor was to offer a source for metal, phosphorus and carbon without using any additional sources. The morphology of products was characterized by transmission electron microscopy, scanning electron microscopy and nature of carbon was analyzed using the Raman microscope and X-ray diffraction. The electrocatalytic oxygen evolution reaction (OER) activity and stability of the metal phosphide nanostructure was evaluated using the rotating disk electrode technique. The CoP, NiP and FeP exhibit the OER overpotential of 370, 380 and 550 mV at 10 mA cm−2, respectively in 0.1 M KOH electrolyte. Among prepared phosphide catalysts, cobalt phosphide shows a lowest Tafel slope indicate favorable kinetics for the OER activity than nickel and iron phosphide catalysts. Graphical abstract Image 1 [ABSTRACT FROM AUTHOR]

Compartmentalization in soft matter is important for segregating and coordinating chemical reactions, sequestering (re)active components, and integrating multifunctionality. Advances depend crucially on quantitative 3D visualization in situ with high spatiotemporal resolution. Here, we show the direct visualization of different compartments within adaptive microgels using a combination of in situ electron and super-resolved fluorescence microscopy. We unravel new levels of structural details and address the challenge of reconstructing 3D information from 2D projections for nonuniform soft matter as opposed to monodisperse proteins. Moreover, we visualize the thermally induced shrinkage of responsive core-shell microgels live in water. This strategy opens doors for systematic in situ studies of soft matter systems and their application as smart materials. [ABSTRACT FROM AUTHOR]

We present a detailed structural discussion of [Au8(PPh3)8](NO3)2, crystallized as a CH2Cl2 solvate. Its structure is compared with closely related triphenylphosphine-stabilized gold clusters. Characterization by optical extinction spectroscopy, luminescence spectroscopy, voltammetry and DFT calculations was performed to determine the electronic HOMO-LUMO gap. Comparison of its characteristic energies with those of structurally related clusters revealed that the evolution of the HOMO-LUMO gap does not follow a simple scaling law but depends on specific structural features. [ABSTRACT FROM AUTHOR]

Abstract: We report, for the first time, symmetric (versus cluster potential of zero charge) charging of narrowly dispersed monolayer-protected Au145 cluster films in a room temperature ionic liquid. Near-reversible voltammetric features are found, indicating up to nine electrochemically accessible charge states with assigned values between −4 and +5. The zero charge state has a stability range of 276mV, very similar as found in solution-phase voltammetry. All other charge states are more narrowly spaced, indicating a sudden increase in cluster capacitance. We ascribe this effect to an abrupt change in local dielectric constant on insertion of one or more counter ions, following departure from zero charge, with a possible contribution of coupled electron–ion transfer. Our findings open perspectives of potential technological importance involving nanocrystal-based device-like behaviour. [Copyright &y& Elsevier]

A coordination polymer [Cp*(O)2Mo-O-Bi(o-tolyl)2]n, II, containing Mo-O-Bi and MoO⋯ Bi moieties was investigated with respect to its behavior in contact with OH- and Cp2MoH2 and as potential single source precursor in the polyol method. It turned out that hydroxide as a base breaks up the polymer to yield Cp*MoO3- and (o-tolyl)2BiOH. The latter polymerizes to give the coordination polymer [(o-tolyl)2BiOH]n, 1. Alternatively, 1 can be prepared by reacting [(o-tolyl)2Bi(hmpa)2]SO3CF3 with NBu4OH/H2O in thf/water. If, however, NBu4OH/MeOH is used in dichloromethane as the solvent, the (o-tolyl)2BiOH formed intermediately undergoes methanolysis, and finally, [(o-tolyl)2BiOMe]n, 3, is isolated. Although 1 and 3 are very similar compounds, their crystal structures differ significantly: while the structure of 1 is dominated by secondary bonding leading to seesaw-type coordination geometries around the Bi centers, the Bi atoms in 3 are coordinated in a distorted tetrahedral fashion, and secondary bonding plays only a minor role. If 1 is dissolved in a nonpolar, nonprotic solvent, condensation reactions occur immediately leading to [(o-tolyl)2BiOBi(o-tolyl)2], 2, which can be obtained on a preparative scale this way. Compound 3 which can be prepared in good yields may prove to be a useful starting material in bismuth chemistry. Here, it was shown to react with molybdocene dihydrides to provide stable Bi-substituted molybdocene monohydrides [RCp2-Mo(H)(Bi(o-tolyl)2)] (R = Me 4, R = H 5); compounds of that type were identified in solution before but had so far eluded isolation. Compound 4, whose crystal structure is discussed, also forms when II is treated with methylated molybdocene dihydride. This obviously leads to the formation of Mo-Bi bonds (→ 4), as well as Mo-OH units, which undergo condensation reactions leading to Mo-O-Mo moieties (i.e., [Cp*2Mo2O5] is formed as a byproduct). The use of II as precursor in the polyol method successfully led to bismuthmolybdate nanoparticles (accompanied by crystallites); however, no single phase is obtained, but biphasic materials consisting of Bi2Mo2O9 and Bi2MoO6, whose ratio can be determined by the choice of the hydrolyzing reagent, are formed instead. One of these materials proved to be capable of sensing EtOH selectively at elevated temperatures. [ABSTRACT FROM AUTHOR]

The DNA-directed self-assembly of surface-bound layers of gold nanoparticles offers a broad range of applications in biomedical analyses as well as in materials science. We here describe a new concept for the assembly of substrate-bound nanoparticle monolayers which employs bifunctional nanoparticles as building blocks, containing two independently addressable DNA oligomer sequences. One of the sequences was utilized for attaching the particle at the solid support, while the other sequence was used to establish cross-links between adjacently immobilized particles. AFM analyses proved the functionality of inter-particle cross-links leading to enhanced surface coverages and the formation of monolayered supramolecular aggregates attached to the substrate. We anticipate that further refinement of this approach will enable applications, for instance, the assembly of ordered layers useful as transducers in biosensing. [Copyright &y& Elsevier]