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The plasmonic properties of noble metals facilitate their use for in-vivo bio-applications such as targeted drug delivery and cancer cell therapy. Nanosilver is best suited for such applications as it has the lowest plasmonic losses among all such materials in the UV-visible spectrum. Its toxicity, however, can destroy surrounding healthy tissues and thus, hinders its safe use. Here, that toxicity against a model biological system (Escherichia coli) is "cured" or blocked by coating nanosilver hermetically with a about 2 nm thin SiO2 layer in one-step by a scalable flame aerosol method followed by swirl injection of a silica precursor vapor (hexamethyldisiloxane) without reducing the plasmonic performance of the enclosed or encapsulated silver nanoparticles (20 - 40 nm in diameter as determined by X-ray diffraction and microscopy). This creates the opportunity to safely use powerful nanosilver for intracellular bio-applications. The label-free biosensing and surface bio-functionalization of these ready-to-use, non-toxic (benign) Ag nanoparticles is presented by measuring the adsorption of bovine serum albumin (BSA) in a model sensing experiment. Furthermore, the silica coating around nanosilver prevents its agglomeration or flocculation (as determined by thermal annealing, optical absorption spectroscopy and microscopy) and thus, enhances its biosensitivity, including bioimaging as determined by dark field illumination.

The synthesis, structure, and high-resolution transmission electron microscopy studies of the layered quadruple perovskite Tb2Ba2Cu2Ti2O11 are reported. This oxide represents the limit of the series Ln2 Ba2Cu2Ti2O11, Tb being the smallest lanthanide compatible with the stability of the ap x ap x 4ap superstructure observed (ap = cubic perovskite cell length). This structure was confirmed by powder X-ray diffraction profile analyses, electron diffraction, and high-resolution electron microscopy. The Cu-O (basal) bond distance of 1,947(3) Å and the Cu-O-Cu bond angle of 169(1)° are the best suited within this series of oxides to the attainment of superconductivity upon appropriate p-doping., We thank the Spanish DGICYT (PB93-0122), CICYT (MAT93-0240-C04-01) and the MIDAS Program (92-1592) for financial support, and the Generalitat de Catalunya for a predoctoral fellowship awarded to M.R.P. We also ihank the German and Spanish governments (SGCCT, MAE) for a joint project (CSIC-Kemforschungszentrum Karlsruhe).

Lead sulfide (PbS) nanoparticles have been synthesized in aqueous solutions by a reaction between inorganic lead salts and sodium sulfide and stabilized using the cationic polyelectrolytes branched poly(ethylenimine) (PEI), poly(allylamine hydrochloride) (PAH), and poly(diallyldimethylammonium chloride) (PDDA). The structures of the polyamine-stabilized nanoparticle dispersions were examined in detail using UV-vis spectroscopy, small-angle X-ray scattering (SAXS), static and dynamic electrophoretic mobility measurements, and transmission electron microscopy (TEM). Considerable differences were found between the stabilizing efficiencies of these polyelectrolytes, which cannot be attributed to their charge densities or their persistence lengths. Small monodisperse nanoparticles of PbS with a tight stabilizing shell were consistently found only when PEI was used as a stabilizer even at high pH values, although its charge density is then very low. The excellence of PEI as a stabilizer is mainly due to the extensive branching of the chains and the presence of uncharged secondary and tertiary amine groups, which apparently serve as good anchoring points at the nanoparticle surfaces. None of the polyelectrolytes examined here provide long-term protection of the nanoparticles toward oxidation by air, showing that a need for more complex multipurpose stabilizers exists for aqueous PbS dispersions. © 2010 American Chemical Society. 26 22 16909 16920 Cited By :13

The controlled production of ZnO nanoparticles within an amorphous silica matrix is achieved using a new methodology consisting of four stages. First, precursor zinc glycerolate nanoparticles are produced within reversed micelles of glycerol in heptane stabilized by the surfactant Aerosol-OT (bis-ethylhexyl sodium sulfosuccinate, AOT). The surface of these nanoparticles is then modified by exchanging AOT with bis-trimethoxysilyl-ethane (BTME). The surface-modified nanoparticles are copolymerized with tetramethoxysilane (TMOS) to provide a composite silica material, in which the nanoparticles are apparently dissolved, producing a uniform distribution of zinc in the silica matrix. Finally, the conversion of zinc to ZnO is achieved by heating the material at 700 °C, leading to a uniform dispersion of very small (< 10 nm) ZnO particles within the amorphous matrix. The fluorescence spectrum of the ZnO particles within the matrix is blue-shifted, as expected from the strong quantum confinement achieved. The properties of the system at all stages in this synthetic process are monitored using TEM, XRD, fluorescence and FT-IR spectroscopy. Glycerol forms complexes with many metal ions, so the present procedure may be generalized to provide uniform distributions of metal ions and subsequently metal oxide nanoparticles in amorphous silica. © 2006 Elsevier Inc. All rights reserved. 302 1 246 253 Cited By :29

The crystallization of PbS in aqueous solutions containing the surfactant sodium dodecyl sulfate (SDS) and hydrophilic polymers resulted in a novel type of metastable nanotubes, the walls of which consist of layers of ordered PbS nanoparticles, apparently separated by layers of surfactant molecules. Information on the mechanism of formation of these structures was obtained by focusing on the roles of the polymer, and of the insoluble lead dodecyl sulfate (Pb(DS)2) present in the system. TEM investigations of the early stages of crystallization revealed the coexistence of PbS and Pb(DS)2 precipitates, the latter being surprisingly important for nanotube formation, and allowed to follow the evolution of layered structures from combination of the two types of crystals. Six different hydrophilic polymers have been used, which interact with SDS with varying strengths. Surprisingly, and in contrast to previous hypotheses, layered nanostructures were observed in all polymer solutions, regardless of the strength of polymer-surfactant interactions. This indicates that, although the presence of a polymer is necessary, polymer-SDS interactions are not a driving force for the formation of the layered structures and nanotubes. On the contrary, the interactions between the polymer chains and the growing particles appear to be of the utmost importance. Results presented here can be interpreted in terms of two alternative mechanisms for layered nanostructure and nanotube formation. © 2006 Elsevier Inc. All rights reserved. 302 1 170 177 Cited By :7

Unusual arrangements of nanoparticles were observed during the synthesis and subsequent dissolution of PbS particles under the action of the surfactant sodium dodecyl sulfate (SDS) in solutions containing hydrophilic polymers. At the selected polymer and surfactant concentrations, the surfactant forms the insoluble lead dodecyl sulfate salt (Pb(DS)2), which competes with the formation of the PbS particles. Under the action of the surfactant the PbS particles form bending self-assembled layers a novel type of metastable nanotubes arises then, the walls of which consist of layers of ordered PbS nanoparticles which are, most likely, separated by bilayers of surfactant molecules. 3 4 569 572 Cited By :88

In this work, we examine the rich crystallization behavior that occurs in PbII/S-II/poly(ethylene oxide) (PEO)/sodium dodecyl sulfate (SDS) systems, in which the anionic surfactant interacts strongly with the polymer molecules, forming micellar aggregates attached to the polymer chains above the critical association concentration. Lead sulfide crystallites are formed in the vicinity of polymer-bound micelles by adding lead and sulfide ions to the polymer-surfactant solution. Surfactant-stabilized inorganic particles adsorbed on the polymer chains combine through a polymer-mediated bridging flocculation mechanism to produce characteristic rodlike colloidal aggregates. Under certain conditions, these evolve into a range of metastable structures, composed of lead sulfide, PbS, and lead dodecyl sulfate, Pb(DS)2. XRD analysis of the metastable reaction products allows us to follow the slow kinetics of their formation and reveals a well-defined layered structure, based on lead dodecyl sulfate, the thickness of which is determined by the length of the surfactant chains. Elemental analysis, 13C- and 207Pb-NMR spectroscopy, FTIR spectroscopy, XPS, and HRTEM are used to characterize these superstructures. At other pH values and system compositions, the production of pure PbS or pure Pb(DS)2 is favored, by appropriate tuning of the concentrations of Pb2+ and S2- ions. The resulting unexpectedly rich crystallization behavior illustrates the complexity of colloidal aggregation phenomena in polymer-surfactant solutions and the significance of coupling colloidal aggregation to ionic equilibria. 105 19 4133 4144 Cited By :31

A series of new aluminum tungsten oxides with the general formula Al 4 W 2 n O 6 n +2 ( n =4–7) was found and structurally characterized by electron diffraction, high-resolution transmission electron microscopy (HRTEM) and high angle annular dark field scanning transmission electron microscopy (HAADF-STEM). The structural model for Al 4 W 10 O 32 ( I 4/ mmm (space group no. 139); a ≈0.375, c ≈3.95 nm) consists of slabs of [5×∞×∞] corner-sharing WO 6 octahedra that are connected via edge-sharing to AlO 6 octahedra. Simulated HRTEM images agree well with the experimental ones and thus support the proposed structural model. The connection between adjacent slabs of WO 3 via AlO 6 octahedra represents a novel variant of crystallographic shear operation for Re O 3 -type structures. The crystallites display a wide range of stacking sequences that are frequently intergrown with each other.