Navigation Links
'Going negative' pays for nanotubes

A Rice University laboratory's cagey strategy turns negatively charged carbon nanotubes into liquid crystals that could enhance the creation of fibers and films.

The latest step toward making macro materials out of microscopic nanotubes depends on cage-like crown ethers that capture potassium cations. Negatively charged carbon nanotubes associate with potassium cations to maintain their electrical neutrality. In effect, the ethers help strip these cations from the surface of the nanotubes, resulting into a net charge that helps counterbalance the electrical van der Waals attraction that normally turns carbon nanotubes into an unusable clump.

The process by Rice chemist Angel Mart, his students and colleagues was revealed in the American Chemical Society journal ACS Nano.

Carbon nanotubes have long been thought of as a potential basis for ultrastrong, highly conductive fibers a premise borne out in recent work by Rice professor and co-author Matteo Pasquali and preparing them has depended on the use of a "superacid," chlorosulfonic acid, that gives the nanotubes a positive charge and makes them repel each other in a solution.

Mart and first authors Chengmin Jiang and Avishek Saha, both graduate students at Rice, decided to look at producing nanotube solutions from another angle. "We saw in the literature there was a way to do the opposite and give the surface of the nanotubes negative charges," Mart said. It involved infusing single-walled carbon nanotubes with alkali metals, in this case, potassium, and turning them into a kind of salt known as a polyelectrolyte. Mixing them into an organic solvent, dimethyl sulfoxide (DMSO), forced the negatively charged nanotubes to shed some potassium ions and repel each other, but in concentrations too low for extruding into fibers and films.

That took the addition of ether molecules known as 18-crown-6 for their crown-like atomic arrangements. The crowns have a particular appetite for potassium; they strip the remaining ions from the nanotube walls and sequester them. The tubes' repulsive qualities become greater and allow for more nanotubes in a solution before van der Waals forces them to coagulate.

At critical mass, nanotubes suspended in solution run out of room and form a liquid crystal, Mart said. "They align when they get so crowded in the solution that they cannot pack any closer in a randomly aligned state," he said. "Electrostatic repulsions prevent van der Waals interactions from taking over, so nanotubes don't have another choice but to align themselves, forming liquid crystals."

Liquid crystalline nanotubes are essential to the production of strong, conductive fiber, like the fiber achieved with superacid suspensions. But Mart said going negative means nanotubes can be more easily functionalized -- that is, chemically altered for specific uses.

"The negative charges on the surface of the nanotubes allow chemical reactions that you cannot do with superacids," Mart said. "You may, for example, be able to functionalize the surface of the carbon nanotubes at the same time you're making fiber. You might be able to crosslink nanotubes to make a stronger fiber while extruding it.

"We feel we're bringing a new player to the field of carbon nanotechnology, especially for making macroscopic materials," he said.


Contact: David Ruth
Rice University

Related biology technology :

1. Blocked holes can enhance rather than stop light going through
2. Neuralstem President and CEO to Update Ongoing ALS and NSI-189/Major Depressive Disorder Trials at 2012 Biotech Showcase
3. New fuel cell keeps going after the hydrogen runs out
4. Sitting still or going hunting: Which works better?
5. Arnold Schwarzenegger's Climate Change Law Gets Enacted; Going Green News Site Green Bean Cleaning Urges Public to Help It Help Build a Greener Earth
6. Jennifer Aniston's People's Choice Awards Dress Worries Animal Welfare Advocates; Going Green News Site My Cleaning Products Comments It Was a Bad Pick
7. 3SBio Inc. Enters Into Merger Agreement For "Going Private" Transaction
8. Going a step Further: Phase IV and Post-Marketing Observational Studies add Value to new Therapies, life Science Webinar Hosted by Xtalks
9. New metamaterial allows transmission gain while retaining negative refraction property
10. Amsterdam Molecular Therapeutics Announces Negative Equity Position
11. Discovery opens door to low-cost negative refraction, new products and industries
Post Your Comments:
(Date:6/23/2016)... ... June 23, 2016 , ... Supplyframe, the Industry Network ... Supplyframe Design Lab . Located in Pasadena, Calif., the Design Lab’s mission is ... projects are designed, built and brought to market. , The Design Lab is ...
(Date:6/23/2016)...  Blueprint Bio, a company dedicated to identifying, protecting ... has closed its Series A funding round, according to ... "We have received a commitment from Forentis Fund that ... meet our current goals," stated Matthew Nunez . ... complete validation on the current projects in our pipeline, ...
(Date:6/23/2016)... ... June 23, 2016 , ... ... regulatory and technical consulting, provides a free webinar on Performing Quality ... 13, 2016 at 12pm CT at no charge. , Incomplete investigations are still ...
(Date:6/22/2016)... 2016 Cell Applications, Inc. and StemoniX ... produce up to one billion human induced pluripotent ... week. These high-quality, consistent stem cells enable researchers ... spend more time doing meaningful, relevant research. This ... manufacturing process that produces affordable, reliable HiPSC for ...
Breaking Biology Technology:
(Date:6/2/2016)... , June 2, 2016   The Weather Company ... announcing Watson Ads, an industry-first capability in which consumers will ... being able to ask questions via voice or text and ... Marketers have long sought an ... consumer, that can be personal, relevant and valuable; and can ...
(Date:5/16/2016)... --  EyeLock LLC , a market leader of iris-based ... IoT Center of Excellence in Austin, Texas ... embedded iris biometric applications. EyeLock,s iris authentication ... with unmatched biometric accuracy, making it the most proven ... platform uses video technology to deliver a fast and ...
(Date:4/28/2016)... , April 28, 2016 First quarter 2016: ... up 966% compared with the first quarter of 2015 ... SEK 589.1 M (loss: 18.8) and the operating margin was 40% ... 0.32) Cash flow from operations was SEK 249.9 M ... revenue guidance is unchanged, SEK 7,000-8,500 M. The operating ...
Breaking Biology News(10 mins):