No abstract

The water‐induced crystallization of alkylbenzenesulfonate‐coated amorphous calcium carbonate (ACC) nanoparticles in water‐in‐isooctane sodium bis(2‐ethylhexyl)sulfosuccinate (NaAOT) microemulsions at a [H2O]/[NaAOT] molar ratio (w) of 10:1 produces a range of organized hybrid surfactant–vaterite nanostructures depending on the water droplet/ACC nanoparticle number ratio, n = [H2O]/[CaCO3]. The crystalline nanostructures develop within primary aggregates of the surfactant‐stabilized ACC nanoparticles by in situ mesoscale transformation, which is mediated by the extent of coupling at the surfactant–inorganic interface. Strong coupling in the presence of low amounts of water (n = 34) gives monodisperse spheroidal aggregates of densely packed 5 nm diameter surfactant‐coated vaterite nanoparticles, whereas weak interactions at n = 3400 produce discrete vaterite nanoparticles, 130 nm in size. Significantly, intermediate levels of coupling produce anisotropic nanostructures such as spindle‐shaped aggregates of 18 nm sized surfactant‐coated vaterite nanoparticles (n = 170) and high‐aspect‐ratio bundles of co‐aligned 10 nm wide twisted vaterite nanofilaments (n = 340). Adding excess aqueous CO32– to the microemulsion droplets inhibits the growth of the nanofilaments, whereas excess Ca2+ has no effect. The results show that the transformation pathways are determined by the extent of water penetration into the ACC cores and electrostatic interactions at the mineral–surfactant interface, and indicate that complex hybrid nanostructures can be assembled in situ when these processes are coupled synergistically at the mesoscopic level. Such observations could be of generic importance in nanochemistry and biomineralization.

No abstract

The European Telecommunications Standards Institute (ETSI) is currently defining a European standard for HIgh PERformance Radio LANs (HIPERLAN). To operate as wired LAN replacements, these systems will need to offer data rates as high as 20 Mb/s. To counteract the time dispersive nature of the indoor radio channel, adaptive equalisation is proposed at the receiver.

Short, single‐particle‐wide chains and complex networks of interconnected chains are easily self‐assembled from 13 nm Au nanoparticles by inducing a surface electrostatic dipolar moment in a controlled manner. Mann and co‐workers further demonstrate both experimentally and theoretically on p. 2553 that efficient surface plasmon coupling takes place in these extensive networks, thus opening a new bottom–up approach to subwavelength optical‐waveguiding devices. The left panel in the image shows isolated 13 nm Au nanoparticles; the back panel, short linear chains; the bottom panel, complex branched network of chains; and the right panel, a graphical rendering of optical spectroscopic properties during the self‐assembly process.