Nanomosis

Nanostructured Nanoparticles: a new dimension in self-assembly

Francesco Stellacci, Finmeccanica Career Development Professor of Materials Science, Department of Materials Science and Engineering, MIT, USA, will present the following seminar from the Pacific Rim Conference in Nanoscience (7-11 September 2004). The seminar will be available for viewing and discussion through the Nanotech Hub at http://nanotech.colayer.net/ .

Nanostructured Nanoparticles: a new dimension in self-assembly

Francesco Stellacci, MIT

Ligand coated metal nanoparticles are promising nanosize materials for novel electronic and optical devices. Their main strength is in the fact that they combine the advantages of small metals, such as single electron transistor (SET) behavior, together with most of the advantages of the organic ligands that are used to coat them, such as solubility in organic solvents and processability for example via self-assembly methods. Moreover, even complex nanoparticles coated with multiple types of ligands can be synthesized in just one step.

Here we present a new family of mixed ligand nanoparticles that shows sub-nanometer patterns (e.g. ridges) on their ligand shell. This unique sub-nano-structuring of their ligand shell provides new properties to the particles. In particular, we focus on silver and gold particles that have ridges composed of hydrophilic valleys and hydrophobic peaks. For the first time we show the ability to control the supramolecular ordering of the ligands on the nanoparticle surfaces. Indeed, by systematically varying the mixture of ligands introduced during nanoparticle synthesis, one can control the resulting surface properties of the nanoparticles. Scanning tunneling microscopy images show ridges 3 Å deep and 6 Å wide on the ligand shell of nanoparticles. Control of both these parameters is provided by the choice of the ligands and of their molar ratio respectively. We also demonstrate that the nanoparticle ligands interact so as to align the stripes of neighboring nanoparticles over large length scales. The synthetic mechanism that leads to the formation of this supramolecular ordering will be discussed. These particles show unique and unexpected wettability, solubility, self-assembly and surface chemistry properties, in fact they show a remarkable resistance to protein nonspecific adsorption.

Barry Hardy
Douglas Connect
www.douglasconnect.com
Nanotechnology Hub: http://nanotech.colayer.net/

Poly-electrolytes at the liquid solid interface: Biochips

B. Montgomery Pettitt, Cullen Distinguished Professor of Chemistry at the University of Houston and Director of the Institute for Molecular Design and the Keck Center for Computational Biology will present the following seminar from the Pacific Rim Conference in Nanoscience (7-11 September 2004). The seminar will be available for viewing and discussion through the Nanotech Hub at http://nanotech.colayer.net/

Poly-electrolytes at the liquid solid interface: Biochips

Biochips are becoming important tools in biochemistry and genetics laboratories. The interface between high-tech media like silicon or silicon dioxide and biotech media like protein or nucleic acids forms a new hybrid technology area with immense possibilities for the future in the areas of combinatorial analysis and synthesis. Interfaces between disparate phases of matter offer large electrostatic field and density gradients changing the local free energy surface and therefore form a challenging set of problems in current chemical physics. The current state of theory and computer simulations of polyelectrolytes (DNA) near surfaces will be presented and compared with recent experiments. Recent results will be discussed in terms of their implications for the design of the next generation of chips.

Barry Hardy
Douglas Connect
www.douglasconnect.com
Nanotech Hub: http://nanotech.colayer.net/