Exploiting substrate stress to modify nanoscale SAM patterns.

We describe a simple method based on postadsorption substrate stress induction to modify and control nanoscale phase-separated patterns formed in self-assembled monolayers. We show using mesoscale computer simulations and experiments that this method helps quickly progress a kinetically arrested patchy pattern into the equilibrium striped pattern, which is otherwise difficult to access. This work also establishes the role of curvature in the formation of aligned stripes several molecules wide on spherical nanoparticles and nanocylinders.

Divalent metal nanoparticles.

Nanoparticles can be used as the building blocks for materials such as supracrystals or ionic liquids. However, they lack the ability to bond along specific directions as atoms and molecules do. We report a simple method to place target molecules specifically at two diametrically opposed positions in the molecular coating of metal nanoparticles. The approach is based on the functionalization of the polar singularities that must form when a curved surface is coated with ordered monolayers, such as a phase-separated mixture of ligands. The molecules placed at these polar defects have been used as chemical handles to form nanoparticle chains that in turn can generate self-standing films.

Entropy-mediated patterning of surfactant-coated nanoparticles and surfaces.

We perform atomistic and mesoscale simulations to explain the origin of experimentally observed stripelike patterns formed by immiscible ligands coadsorbed on the surfaces of gold and silver nanoparticles. We show that when the conformational entropy gained via this morphology is sufficient, microphase-separated stripelike patterns form. When the entropic gain is not sufficient, we instead predict bulk phase-separated Janus particles. We also show corroborating experimental results that confirm our simulational predictions that stripes form on flat surfaces as well as on curved nanoparticle surfaces.

From homoligand- to mixed-ligand- monolayer-protected metal nanoparticles: a scanning tunneling microscopy investigation.

The ligand shell that coats, protects, and imparts a large number of properties to gold nanoparticles is a 2-D self-assembled monolayer wrapped around a 3-D metallic core. Here we present a study of the molecular packing of ligand shells on gold nanoparticles based on the analysis of scanning tunneling microscopy (STM) images. We discuss methods for optimal nanoparticle sample preparation in relation to STM imaging conditions. We show that the packing of a self-assembled monolayer composed solely of octanethiols on gold nanoparticles depends on the particle's diameter with an average headgroup spacing of 5.4 A, which is different from that of similar monolayers formed on flat Au(111) surfaces (5.0 A). In the case of nanoparticles coated with mixtures of ligands-known to phase separate into randomly shaped and ordered domains on flat surfaces-we find that phase separation leads to the formation of concentric, ribbonlike domains of alternating composition. The spacing of these domains depends on the ligand shell composition. We find that, for a given composition, the spacing increases with diameter in a manner characterized by discontinuous transitions at "critical" particle sizes. We discuss possible interpretations for the observed trends in our data.

Paediatric trauma at an adult trauma centre.

BACKGROUND: Trauma in children remains the commonest cause of mortality. The majority of injured children who reach hospital survive, indicating that additional more sensitive outcome measures should be utilized to evaluate paediatric trauma care, including morbidity and missed injury rates. Limited contemporary data have been presented reviewing the care of injured children at an adult trauma centre (ATC). METHODS: A review was undertaken of injured children who warranted activation of the trauma team, treated within the emergency department of an ATC (Royal North Shore Hospital) situated in the Lower North Shore area of Sydney. Data were collected prospectively and patients followed through to death or discharge from the ATC or another institution to which they had been transferred. RESULTS: A total of 93 children were admitted to the ATC between January 1999 and April 2002. Mean age was 9 years 3 months (range 5 weeks-15 years 9 months) and 70% were male. The median injury severity score was 15 (range 1-75) and there were three deaths. Forty-two children were transferred to a paediatric trauma centre (PTC), including three children who had been transferred to the ATC from another hospital. There was one missed injury and one iatrogenic urethral injury. CONCLUSIONS: The majority of children with trauma were treated safely and appropriately at the ATC. The missed injury rate was < 1% and there were no adverse long-term sequelae of initial treatment. Three secondary transfers could have been avoided by more appropriate coordination of the initial referral to a PTC.

Spontaneous assembly of subnanometre-ordered domains in the ligand shell of monolayer-protected nanoparticles.

The properties of materials can be created and improved either by confining their dimensions in the nanoscale or by controlling their nanostructure. We have combined these two concepts, and here we describe a new class of nanostructured nanosized materials that show ordered phase-separated domains at an unprecedented molecular length scale. Scanning tunnelling and transmission electron microscope images of monolayer-protected metal nanoparticles, with ligand shells composed of a mixture of molecules, show that the ligands phase-separate into ordered domains as small as 5 A. Importantly, the domain shape and dimensions can be controlled by varying the ligand composition or the metallic core size. We demonstrate that the formation of ordered domains depends on the curvature of the underlying substrate, and that novel properties result from this nanostructuring. For example, because the size of the domains is much smaller than the typical dimensions of a protein, these materials are extremely effective in avoiding non-specific adsorption of a variety of proteins.