Search

Compared to conventional deposition techniques for the epitaxial growth of metal oxide structures on a bulk metal substrate, wet-chemical synthesis based on a dispersible template offers advantages such as low cost, high throughput, and the capability to prepare metal/metal oxide nanostructures with controllable size and morphology. However, the synthesis of such organized multicomponent architectures is difficult because the size and morphology of the components are dictated by the interplay of interfacial strain and facet-specific reactivity. Here we show that solution-processable two-dimensional Pd nanotetrahedra and nanoplates can be used to direct the epitaxial growth of γ-Fe2O3 nanorods. The interfacial strain at the Pd-γ-Fe2O3 interface is minimized by the formation of an FexPd "buffer phase" facilitating the growth of the nanorods. The γ-Fe2O3 nanorods show a (111) orientation on the Pd(111) surface. Importantly, the Pd@γ-Fe2O3 hybrid nanomaterials exhibit enhanced peroxidase activity compared to that of isolated Fe2O3 nanorods with comparable surface area because of a synergistic effect for the charge separation and electron transport. The metal-templated epitaxial growth of nanostructures via wet-chemical reactions appears to be a promising strategy for the facile and high-yield synthesis of novel functional materials. [ABSTRACT FROM AUTHOR]

Nanostructured tin dioxide was synthesized by makinguse of thecatalytic activity of silicatein-α. TEM, HRTEM, and XRD revealedthe formation of cassiterite SnO2. Surface bound silicateinretains its biocatalytic activity. This was demonstrated by immobilizingsilicatein on glass surfaces using a histidine-tag chelating anchor.The subsequent deposition of SnO2on glass was monitoredby quartz crystal microbalance (QCM) measurements and scanning electronmicroscopy (SEM). This new aspect of silicatein activity toward theformation of metal oxides other than SiO2, TiO2, and BaTiO3opens up new vistas in composite materialsynthesis. [ABSTRACT FROM AUTHOR]

A chemically specific and facile method for the immobilization of metal oxide nanoparticles onto the surface of IF-MoS2nested fullerenes is reported. The modification strategy is based on the chalcophilic affinity of transition metals such as Fe2ﱗ, Fe3, or Zn2 described by the Pearson HSAB concept. The binding capabilities of the 3d metals are dictated by their Pearson hardness. Pearson hard cations such as Fe3(Fe2O3) do not bind to the chalcogenide surfaces; borderline metals such as Fe2(Fe3O4) or Zn2(ZnO) bind reversibly. Pearson-soft metals like Au bind irreversibly. The immobilization of metal oxide nanoparticle colloids was monitored by transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM) combined with energy dispersive X-ray spectroscopy (EDX), and X-ray diffraction (XRD). [ABSTRACT FROM AUTHOR]

A chemically specific and facile method for growth of ZnO nanorods on WS2nanotubes (NT-WS2) is reported. The modification strategy is based on the chalcophilic affinity of Zn, which serves as an anchor to immobilize ZnO colloids onto the WS2nanotubes. The surface bound ZnO colloids have been used as a seed to grow ZnO nanorods on WS2nanotubes. The immobilization of ZnO colloids was monitored by UV−vis spectroscopy and photoluminescence spectroscopy whereas the growth of ZnO nanorods was characterized by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). [ABSTRACT FROM AUTHOR]

Surface functionalization of nanoparticles (NPs) plays a crucial role in particle solubility and reactivity. It is vital for particle nucleation and growth as well as for catalysis. This raises the quest for functionalization efficiency and new approaches to probe the degree of surface coverage. We present an (in situ) proton nuclear magnetic resonance ( 1 H NMR) study on the ligand exchange of oleylamine by 1-octadecanethiol as a function of the particle size and repeated functionalization on Au NPs. Ligand exchange is an equilibrium reaction associated with Nernst distribution, which often leads to incomplete surface functionalization following "standard" literature protocols. Here, we show that the surface coverage with the ligand depends on the (i) repeated exchange reactions with large ligand excess, (ii) size of NPs, that is, the surface curvature and reactivity, and (iii) molecular size of the ligand. As resonance shifts and extensive line broadening during and after the ligand exchange impede the evaluation of 1 H NMR spectra, one- and two-dimensional 19 F NMR techniques (correlation spectroscopy and diffusion ordered spectroscopy) with 1H,1H,2H,2H-perfluorodecanthiol as the fluorinated thiol ligand were employed to study the reactions. The enhanced resolution associated with the spectral range of the 19 F nucleus allowed carrying out a site-specific study of thiol chemisorption. The widths and shifts of the resonance signals of the different fluorinated carbon moieties were correlated with the distance to the thiol anchor group. In addition, the diffusion analysis revealed that moieties closer to the NP surface are characterized by a broader diffusion coefficient distribution as well as slower diffusion.