Nanotechnology: Science and Application

Nanotechnology: Science and Application

by Mohamed Abdel-Mottaleb

The International Conference on NanoTechnology: Science and Application (NanoTech Insight’05) was held in the beautiful, historic city of Luxor, Egypt, from 20–25 February 2005. Over 200 participants—representing leading researchers from 40 countries—contributed to a very successful conference.

The scientific content of the meeting was as diverse as it was high in quality, emphasizing the intrinsic multidisciplinary nature of nanotechnology. Split into two sessions, the program featured 22 plenary lectures, 30 keynote lectures, 48 contributed talks, and 100 posters.

Klaus Müllen (Max Plank Institute, Mains, Germany) gave the opening lecture in which he gave an exemplary lesson on “putting the molecules into molecular electronics” by demonstrating the self-assembly of polycyclic aromatic hydrocarbons into columns and ordered monolayers for the formations of supramolecular wires and two-dimensional crystals. Chemically gated rectifiers were structured at surfaces by using such systems. Beng Ong (Xerox Research Labs, Toronto, Canada) provided excellent proof of the feasibility of this approach to electronics through Inkjet processing of oligothiophene derivatives to produce printed field effect transistors with high on/off ratios. Further examples of molecular electronics and self-assembly approaches where demonstrated by Concepció Rovira (Consejo Superior de Investigaciones Cientificas (CSIC), Barcelona, Spain) and Maria Rampi (Ferrara University, Italy, and Harvard University, Massachusetts, USA). Avik Ghosh (Purdue University, Indiana, USA) and Peter Hänggi (Augsberg University, Germany) elegantly showed how the design and interpretation of physical experiments now benefit from precision calculation of the electronic properties of nanostructures.

The 10-nm-size regime is often seen as the realm of these bottom-up molecular approaches; however, top-down CMOS (complementary metal oxide semiconductor) techniques are expected to reach sizes of around this value. Hans Lüth (Research Centre, Jülich, Germany) showed how combinations of the two approaches are certain to be fruitful, and reflected on how new device types will become necessary as the quantum mechanical limit is reached.

Self-assembly is a powerful paradigm in the preparation of chemical systems at the nanoscale from the bottom-up approach. In this context Alan Rowan (Nijmegen, The Netherlands) demonstrated the control of polymers over nanostructures by threading a catalyst ring over a polymer chain. Roberto Lazzaroni (Mons-Hainaut, Belgium) additionally exposed the dramatic effects that block polymer composition can have on the nanostructures and properties. Roeland Nolte (Nijmegen, The Netherlands) showed how block copolymers are even self-assembled into vesicles that can house enzymes and whose surfaces can be polymerized to create conducting spheres.

11 layers of 4.7 nm—atomic force microscopy image	6 layers of 10 m—Step Pyramid in Egypt, Netjenkhet Djoser (2667–2648 BC), The 2nd King of Egypt’s 3rd Dynasty
Multilayer assembly of a thiophene oligomer. From slide presented by Roberto Lazzaroni.

The versatility of the self-assembly approach was clearly shown by the wealth of structures and properties demonstrated by Dirk Kurth (MPI Colloids and Interfaces, Potsdam, Germany), Jaume Veciana (CSIC, Spain), and Raphaël Lévy (Liverpool, UK).

It has been recognized that natural phenomena can act as a guide to unnatural chemical systems. Paul Hansma (University of California, Santa Barbara, USA) showed how the tools of nanoscience are giving new insight into the way in which nature has developed nanostructured materials with crosslinks, which behave as “sacrificial bonds” and fracture before the backbone of the polymers, which break at a force of over 1000 pN. These safeguards are present in systems as diverse as spider silk, abalone shell, and bone; their elegance is that only these reformable bonds are broken (at forces below 500 pN), thus providing a damage protection mechanism.

“Molecular Surgery” on biological structures was shown by Min-qian Li (Chinese Academy of Sciences, Shanghai, China), who demonstrated the formation of artificial DNA structures via “molecular combing,” and then put the molecules under the knife using an atomic force microscope.

Perhaps the most remarkable chemical feat exposed at the conference was the preparation of a series of triruthenium cluster oligomers, which in the case of the tetramer displays a 14-step reversible sequence of redox processes involving the transfer of 15 electrons. Tasuku Ito (Tohoku Univer-sity, Japan) showed how judicious choice of ancillary ligands surrounding the complexes can give this effect as well as gradients of potential in dendrimers based on the same module. The systems are surely interesting for molecular electronics.

Paul Ziemann (Ulm, Germany) brought the conference to a fitting climax, showing how metal-loaded block copolymers can be used for the preparation of ordered arrays of both gold and cobalt nanoparticles after removal of the polymer matrix by optimized hydrogen plasma treatment. One of the results presented revealed the remarkable fact that Au₅₅ clusters are Nobler than bulk gold! The outlook for these processes and materials in the preparation of new devices is very promising.

With the high-caliber lectures and posters presented, the conference succeeded in establishing strong collaborations among advanced research groups in the field and the developing world, widening the benefits of nanoscience beyond developed countries, and promoting female scientists. The participants perceived the conference as a scientific, intellectual, and social success. The organizers of the conference would like to issue a warm thank you to all participants for their scientific contributions and for making the event so memorable.

The next NanoTech Insight conference will take place in Cairo, Egypt, 11–17 March 2007.

Dr. Mohamed Abdel-Mottaleb <mohamed.abdel-motaleb @physik.tu-chemnitz.de> is a research associate at the Technical University of Chemnitz, Germany, and was the chairman of NanoTech Insight'05.

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