{"id":9908,"date":"2016-08-17T06:29:23","date_gmt":"2016-08-17T06:29:23","guid":{"rendered":"http:\/\/www.kurzweilai.net\/?p=286497"},"modified":"2016-08-20T01:36:50","modified_gmt":"2016-08-20T01:36:50","slug":"how-to-separate-out-semiconducting-carbon-nanotubes","status":"publish","type":"post","link":"https:\/\/hoo.central12.com\/fugic\/2016\/08\/17\/how-to-separate-out-semiconducting-carbon-nanotubes\/","title":{"rendered":"How to separate out semiconducting carbon nanotubes"},"content":{"rendered":"
\"\"<\/a>

Artistic rendition of a metallic carbon nanotube being pulled into solution, in analogy to the work described by the Adronov group (credit: Alex Adronov, McMaster University)<\/p><\/div>\n

Researchers at McMaster University<\/a> in Canada have developed a radically improved way to purify single-wall carbon nanotubes (SWNTs) — flexible structures that are one nanometer in diameter and thousands of times longer, \u00adand that may revolutionize computers and electronics, replacing silicon.<\/p>\n

To do that, we need to separate out semiconducting (sc-SWNTs) and metallic (m-SWNTs) nanotubes. That’s a challenging problem, because both are created simultaneously in the process* of producing carbon nanotubes.<\/p>\n

\u201cOnce we have a reliable source of pure nanotubes that are not very expensive, a lot can happen very quickly,\u201d says Alex Adronov<\/a>, a professor of Chemistry at McMaster whose research team has developed a new and potentially cost-efficient way to purify carbon nanotubes.<\/p>\n

Separating out semiconducting carbon nanotubes<\/strong><\/p>\n

Previous researchers have created polymers that could allow semiconducting carbon nanotubes to be dissolved and washed away, leaving metallic nanotubes behind, but there has not been such a process for doing the more-useful opposite: dispersing the metallic nanotubes and leaving behind the valuable semiconducting structures.<\/p>\n

\"\"

Single-wall carbon nanotube (credit: NASA)<\/p><\/div>\n

<\/strong>Now, Adronov\u2019s research group has reversed the electronic characteristics (from electron-rich to electron-poor) of a polymer known to disperse semiconducting nanotubes, while leaving the rest of the polymer\u2019s structure intact. That is, they have reversed the purification process — leaving the semiconducting nanotubes behind while making it possible to disperse the metallic nanotubes.**<\/p>\n

The next step, he explains, is for his team or other researchers to exploit the discovery by finding a way to develop even more efficient polymers and scale up the process for commercial production.<\/p>\n

The unique properties of SWNTs — high ten\u00adsile strength, the high aspect ratio, thermal and electrical conductivity, and extraordinary optical characteristics — could make carbon nanotubes potentially valuable as advanced materials in a variety of applications, including “field-effect transistors, photovoltaics, flexible electronics, sensors, touch screens, high-strength fibers, biotech\u00adnological constructs, and various other devices,” the researchers note in the current cover story of Chemistry \u2013\u00a0A European Journal<\/em>.<\/p>\n

Financial support for this work was provided by the Discovery and Strategic Grant programs of the Natural Science and Engi\u00adneering Research Council (NSERC) of Canada.<\/p>\n

* These processes include high-pressure carbon monoxide disproportionation (HiPCO),carbon vapor deposition (CVD),arc discharge,laser ablation, and plasma torch growth.<\/em><\/p>\n

** “We expect that relatively electron-poor con\u00adjugated polymers should disperse m-SWNTs to a greater extent when compared to structurally similar electron-rich conjugated polymers. Here, we demonstrate this concept through the comparison of a poly(fluorene-co-pyridine) conjugated polymer before and after post-polymerization functionalization. By par\u00adtially methylating the pyridine units, cationic charges are intro\u00adduced onto the conjugated backbone, which convert the polymer from being electron-rich to electron-poor. This enables the comparison of two polymers that are identical in length and polydispersity, and differ primarily in their electronic character\u00adistics. We show that the electron-poor conjugated polymer re\u00adsults in dispersions that are enriched in m-SWNTs, while the electron-rich counterpart solely selects for sc-SWNTs, thus pro\u00adviding evidence that the electronic structure of a conjugated polymer plays an important role in determining its selectivity for different SWNT types.” — Darryl Fong et al.\/<\/em>Chemistry – A European Journal.<\/p>\n

\n

Abstract of\u00a0Influence of Polymer Electronics on Selective Dispersion of Single-Walled Carbon Nanotubes<\/em><\/strong><\/p>\n

In the pursuit of next-generation polymers\u00a0for the selective dispersion and purification of single-walled carbon nanotubes (SWNTs), understanding the key parameters dictating polymer selectivity is imperative. Simple modification of a poly(fluorene-co<\/em>-pyridine) backbone, such that it is transformed from being electron-rich to -poor, has a significant impact on the electronic nature of the SWNTs dispersed. The unmodified copolymer bearing an electron-rich fluorene co-monomer preferentially forms stable colloids with sc-SWNTs, while the methylated copolymer bearing electron-withdrawing cationic charges produces dispersions that are more enriched with\u00a0m<\/em>-SWNTs.<\/p>\n","protected":false},"excerpt":{"rendered":"

Researchers at McMaster University in Canada have developed a radically improved way to purify single-wall carbon nanotubes (SWNTs) — flexible structures that are one nanometer in diameter and thousands of times longer, ­and that may revolutionize computers and electronics, replacing silicon. To do that, we need to separate out semiconducting (sc-SWNTs) and metallic (m-SWNTs) nanotubes. […]<\/p>\n","protected":false},"author":13,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[48,55,43],"tags":[],"class_list":["post-9908","post","type-post","status-publish","format-standard","hentry","category-electronics","category-nanotechmaterials-science","category-news"],"_links":{"self":[{"href":"https:\/\/hoo.central12.com\/fugic\/wp-json\/wp\/v2\/posts\/9908"}],"collection":[{"href":"https:\/\/hoo.central12.com\/fugic\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/hoo.central12.com\/fugic\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/hoo.central12.com\/fugic\/wp-json\/wp\/v2\/users\/13"}],"replies":[{"embeddable":true,"href":"https:\/\/hoo.central12.com\/fugic\/wp-json\/wp\/v2\/comments?post=9908"}],"version-history":[{"count":2,"href":"https:\/\/hoo.central12.com\/fugic\/wp-json\/wp\/v2\/posts\/9908\/revisions"}],"predecessor-version":[{"id":9970,"href":"https:\/\/hoo.central12.com\/fugic\/wp-json\/wp\/v2\/posts\/9908\/revisions\/9970"}],"wp:attachment":[{"href":"https:\/\/hoo.central12.com\/fugic\/wp-json\/wp\/v2\/media?parent=9908"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/hoo.central12.com\/fugic\/wp-json\/wp\/v2\/categories?post=9908"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/hoo.central12.com\/fugic\/wp-json\/wp\/v2\/tags?post=9908"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}