The inner space of carbon nanotubes can act as a template for the synthesis of nanodiamond-like carbon chains, say a team of scientists from Japan, Germany and the US. As they report in Angewandte Chemie, their templated polymerization approach could pave the way for the design of novel one-dimensional nanomaterials.

Nano-sized materials such as nanowires offer unique properties that are completely distinct from those of bulk materials. However, one-dimensional nanostructures can be difficult to synthesize. In an international cooperation, Hisanori Shinohara from Nagoya University in Japan and his colleagues have now developed a method that uses carbon nanotubes as a reaction vessel for the templated polymerization of linear-chain nanomaterials.

The idea is that polymerizing small precursor molecules while they are confined within a carbon nanotube causes them to adopt the one-dimensional structure of the tube. Without this physical restriction, the polymerization process could terminate early or run out of control. As a demonstration of this method, Shinohara and his colleagues used it to synthesize a one-dimensional nanodiamond polymeric structure. "The present template-based approach for the synthesis of linear-chain diamondoid polymers is entirely different from conventional chemical approaches," they claim.

To produce the one-dimensional nanodiamond, the scientists used diamantane, a 10-carbon cage structure, as the precursor molecule. By exposing the diamantine molecule to iron nanoparticles, they were able to convert them into reactive diradicals. In a normal chemical polymerization reaction, these radicals would quickly react with hydrogen, but: "To our great surprise, the radicals are persistent and recombined with each other inside the carbon nanotubes," the scientists reported. "Depending on the inner diameter of the carbon nanotubes, the inserted species can either be transformed into the linear-chain polymers or into amorphous carbon." Inside 1nm-wide carbon nanotubes, the diamantine joined together to form a polymeric chain of nanodiamond, as confirmed by electron microscopy.

To extract the nanodiamond chain from the nanotube, the scientists used a solution-phase sonication/extraction process. The big advantage of this new fabrication process is its simplicity and specificity, and the scientists think it could be applied to the synthesis of many more one-dimensional nanomaterials.

This story is adapted from material from Angewandte Chemie, with editorial changes made by Materials Today. The views expressed in this article do not necessarily represent those of Elsevier. Link to original source.