Electrodeposition of zinc hydroxysulfate nanosheets and reduction to zinc metal microdendrites on polypyrrole films.

Nanothin sheets made of zinc sulfate hydroxide hydrate, ZnSO4[Zn(OH)2]3 x 5H2O, are easily and quickly prepared using an innovative electrochemical route onto polypyrrole-polystyrene sulfonate (PPy-PSS) films. The sheets are characterized using a range of experimental techniques. The deposits are formed on the film surface with instantaneous nucleation to grow into a network of entangled nanosheets. The effect of the experimental conditions on the deposition is reported. Interestingly, the formation of the nanosheets is observed on PPy-PSS films only, and not on films doped with other sulfate/sulfonate dopants. The zinc nanosheets can be easily electrochemically reduced to metallic zinc microdentrites.

Perpendicular growth of catalyst-free germanium nanowire arrays.

High yields of single-crystalline Ge nanowires (NWs) were synthesised in the vapour phase of a high boiling point organic solvent without the need for metal catalyst particles. High density, perpendicular arrays of Ge NWs were subsequently grown from ITO coated substrates. The approach represents a convenient route toward orientated arrays of catalyst-free Ge NWs.

Directing semiconductor nanorod assembly into 1D or 2D supercrystals by altering the surface charge.

Coulomb repulsion due to the surface charge on semi-conductor nanorods works against the dipole-dipole attraction that tends to direct the nanorods to self-assemble; the nature of this self-assembly for CdSe nanorods can be thus altered by pyridine washing, which charges the rods surface--thereby allowing the Coulomb repulsion to tailor the alignment.

A multi-rate kinetic model for spontaneous oriented attachment of CdS nanorods.

A multi rate kinetic model to explain the spontaneous oriented attachment of CdS nanorods in the presence of an amine is presented. The model demonstrates the reasons that elongation is restricted to a maximum of quadruple, the starting rod length for rods of a certain aspect ratio (8 × 30 nm) with no elongation occurring for rods of a shorter aspect ratio. The rate constants for all possible attachment events are determined showing that elongation by attachment occurs sequentially by single rod addition alone. Both the reaction rate and the activation energy for subsequent attachment are found to increase as the rod lengthens. The increase in reaction rate correlates with increased dipole moment of longer rods which orients the rods end to end to maximize collision events. The two components of this reaction are alignment and fusion, with the former restricting attachment of low aspect ratio rods and the latter restricting attachment to higher aspect ratio rods. The model therefore predicts an aspect ratio "window" in which oriented attachment of nanorods is energetically possible.

Block copolymer mediated stabilization of sub-5 nm superparamagnetic nickel nanoparticles in an aqueous medium.

This paper presents a facile method for decreasing the size of water dispersible Ni nanoparticles from 30 to 3 nm by the incorporation of a passivating surfactant combination of pluronic triblock copolymer and oleic acid into a wet chemical reduction synthesis. A detailed study revealed that the size of the Ni nanoparticles is not only critically governed by the concentration of the triblock copolymers but also dependent on the hydrophobic nature of the micelle core formed. The synthesized Ni nanoparticles were thoroughly characterized by means of transmission electron microscopy, x-ray diffraction, x-ray photoelectron spectroscopy and temperature and field dependent magnetic measurements, along with a comprehensive Fourier transform infrared spectroscopy analysis, in order to predict a possible mechanism of formation.

Spontaneous room temperature elongation of CdS and Ag2S nanorods via oriented attachment.

Spontaneous elongation from nanorod to nanowire in the presence of an amine is reported for nanocrystals of cadmium sulfide and silver sulfide (cation exchanged from CdS). Elongation occurs instantaneously where the final aspect ratio is a controllable multiple of the original nanorod length. Transmission electron microscopy (TEM) analysis reveals the influential factors on the attachment process are the concentration of amine, duration and temperature of the reaction. The elongated nanorods are further characterized by X-ray diffraction (XRD), photoluminescence (PL), ultraviolet-visible spectroscopy (UV-vis) and X-ray photoelectron spectroscopy (XPS). A mechanism of oriented attachment is evidenced by the doubling in length of asymmetrically gold tipped CdS nanorods with the corresponding absence of elongation in symmetrically tipped nanorods.