Wet Chemical Synthesis of Highly Aligned ZnO Nanowires with Optical Properties

International audienc

Wet Chemical Synthesis of Highly Aligned ZnO Nanowires with Optical Properties

International audienc

Molecular simulation of zinc oxide nanostructures confined in carbon nanotubes

International audienceThis paper reports on a molecular simulation study of ZnO nanostructures confined within carbon nanotubes. Both the effects of confinement (by varying the pore size) and degree of pore filling (by varying the number of confined ZnO monomers) on the structure of the nanomaterial are addressed. None of the nanostructures exhibits the ideal structure of one of the ZnO bulk crystal phases (rocksalt, blende and wurtzite), but some crystalline features with significant correlations for the first and second nearest neighbours are observed. Close inspection of the location of the peaks in the pair correlation functions, of the angle distributions between Zn–O nearest neighbours and of some corresponding molecular configurations suggest that the confined nanoparticles possess mainly the local ordering of wurtzite. We also found evidence for defects such as Zn atoms that are involved in both a four-atom ring (characteristic of a cubic phase) and a six-atom ring (characteristic of wurtzite). Due to the smaller coordination number of atoms located at the interface between the nanostructure and the nanotube, the number of nearest neighbours of like and unlike atoms is smaller than that of the bulk. It is also found that the morphology of the nanostructures embedded in the carbon nanotubes depends in a subtle way on the different parameters involved in the synthesis (nanotube size, filling density). ZnO arranges itself to form either nanorods (quasi-1D systems) or an isolated nanoparticle (dimensionality 0D). When the filling density is low, further calculations suggest that the isolated particle is more well ordered and is more stable. We also show that the O atoms are polarised along the radial direction Δr>0 (i.e. towards the external free interface). Our results also show that the use of a symmetrical nanopore as a template imposes that the confined particles exhibit surfaces terminated with both Zn and O atoms in the same stoichiometry

A soft chemistry route to prepare hybrid ZnO nanostructured films with a lamellar structure

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Zinc Oxide Nanostructures Confined in Porous Silicas

International audienceWe report on molecular simulations of zinc oxide nanostructures obtained within silica nanopores of diameter D = 1.6 nm and D = 3.2 nm. Both the effects of confinement (by varying the pore size) and degree of pore filling on the structure of the nanomaterial are addressed. Two complementary approaches are adopted: 1) the stability of the three crystalline phases of ZnO (wurtzite, rocksalt, and blende) in the silica nanopores is studied, and 2) ZnO nanostructures are obtained by slowly cooling down a homogeneous liquid phase confined in the silica pores. None of the ideal nanostructures (wurtzite, rocksalt, blende) retains the ideal structure of the initial crystal when confined within the silica pores. Only the structure starting from the ideal wurtzite nanocrystal remains significantly crystalline after relaxation, as revealed by the marked peaks in the pair correlation functions for this system. The morphology and degree of cristallinity of the structures are found to depend on the parameters involved in the synthesis (pore size, filling density). Nanograin boundaries are observed between domains of different crystal structures. Reminiscent features of the bulk behavior, such as faceting of the nanostructures, are also observed when the system size becomes large. We show that the use of nanopores as a template imposes that the confined particles exhibit neutral (basal) surfaces. These predictions provide a guide to experiments on semiconductor nanoparticle

Morphology Control of ZnO Nanomaterials using Double Hydrophilic Block Copolymers

posterInternational audienceHighly crystalline zinc oxide (ZnO) nanomaterials are synthesized using a seeded growth sol-gel method. In order to control the morphology and the organization of the ZnO nanomaterials, a double hydrophilic block copolymer has been introduced during the seeded growth synthesis: the Polyacrylic acid-Polyacrylamide (PAA-PAM). Depending on the amount of PAA-PAM copolymers, different morphologies were obtained, such as ZnO nanostructured spheres or flat hexagonal crystals. Thus, systematic studies have been done to investigate the influence of the copolymer addition on ZnO nanomaterial morphologies and explain the mechanisms of the morphological modifications