Site-selective modification of carbon nanotubes

(Nanowerk News) Carbon nanotubes have shown tremendous promise as key elements in ultrasensitive detectors of cancer-related markers and genes, and toward that end, investigators have developed a number of methods for attaching antibodies and other "detection" agents to the surface of carbon nanotubes. Now, researchers at Rensselaer Polytechnic Institute have developed a technique that allows them to attach molecules to just a few specific nanotubes within an array of thousands of nanotubes. This new method could speed the development of nanosensor arrays capable of detecting multiple cancer markers in human tissue or blood samples.
Reporting its work, titled "Site-selective functionalization of carbon nanotubes", in the Jan. 27, 2006 online edition of Advanced Materials, a research team headed by Ganapathiraman Ramanath, Ph.D., used a technique known as focused ion beam irradiation, followed by a mild chemical reaction, to functionalize carbon nanotubes at preselected locations within an array of nanotubes. The same technique can be used to functionalize an individual nanotube at a specific location along its length.
The key to this method is using ions of very high energy to create chemically reactive defects on a carbon nanotube. These defects then act as sites for anchoring detection reagents and other biomolecules using mild chemical reactions of the sort that do not damage biomolecules. By using focused ion beams to create the defects, the researchers were able to create reactive areas as small as 5 nanometers in width on the nanotube surface.
The investigators presented several examples in which they successfully modified nanotubes with useful detection agents. In one case, the researchers were able to attach gold nanoparticles to carbon nanotubes. In another example, the researchers demonstrated that they could attach a sensitive metal-containing enzyme to the nanotubes without damaging the protein in the process.
Source: National Cancer Institiute