ARCHIVED - Construction Codes for Molecular Assembly
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November 04, 2004— Ottawa, Ontario
NRC Annual Report 2003-2004
One important area of nanoscale research involves joining organic molecules with silicon, a well-known substance that plays a central role in all modern electronic devices. Organic chemists can tailor-make molecules with numerous useful properties, such as conductivity and the ability to transmit light. Such molecules can then be used to create more powerful and flexible versions of traditional circuitry found on silicon chips, such as wires and transistors.
|Researcher at the NRC National Institute for Nanotechnology|
But, many challenges must be overcome before such devices can be built and sold in the marketplace. A number of key questions remain to be answered: What modifications are needed to join different kinds of molecules with different properties to the same piece of silicon? How can we control the location where a chemical reaction will take place? How can we control the extent of this reaction? Researchers at NINT in Edmonton, Alberta, have been trying to establish these kinds of "construction codes", codes that are critical to the future builders of molecular-scale devices.
Nanotech Across NRC
Many NRC institutes pursue research at the nanoscale level, involving research into applications for medical devices, electronics, fuel cells and construction materials. Current projects include the development of new nanocomposite coatings to create new and improved hip prostheses (NRC Integrated Manufacturing Technologies Institute). Elsewhere, researchers at NRC-IMI continued work in the area of nanocomposites and opened specialized facilties for nanoimprint lithography. And, researchers at NRC-ICPET patented a new environmentally friendly and low-cost method to generate Platinum/Ruthenium alloy nanoparticles used as a fuel-cell catalyst.
In the past year, NINT researchers demonstrated a reversible process for controlling chemical reactions on the surface of silicon. The group worked with a chemical effect known as passivation, which produces a layer of oxidation and effectively limits any further chemical reactions on the target surface. By way of example, when painting a room, putting a piece of tape down to protect wall trim would be, in effect, "passivating" this surface — it is protected against paint. When the tape is removed, a different paint with a different colour can be applied to the trim. The "tape", in the case of chemical reactions with silicon, was supplied through the use of TEMPO, a stable radical, which was used to passivate chemically-reactive areas on a hydrogen-terminated silicon surface, known as dangling bonds. Using a scanning tunnel microscope, researchers also demonstrated the ability to remove this passivation effect. With this approach, it's possible to control, at will, the areas that are chemically reactive, turning on or off this potential as needed.
The result is that users can determine the exact location where molecules will be joined to the surface and can use different molecules with different functions on the same surface — a promising advance in defining the "construction codes" for molecular-scale electronic devices, which could have applications in numerous fields from electronics to biotechnology.
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National Research Council of Canada
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