Hollow carbon nanoparticles are strong, conduct electricity well and have a remarkably large surface area. They show promise in applications such as water filtration, hydrogen storage and battery electrodes - but commercial use would demand reliable, low-cost ways for their production.
Xu Li of Singapore's A*STAR Institute of Materials Research and Engineering and co-workers have developed a simple manufacturing technique that offers precise control over the size and shape of hollow carbon nanospheres1.
A current method for preparing these particles involves coating a hard template, such as silica nanoparticles, with a carbon-based material that can be fused into a shell using extreme heat. This is a laborious process, and etching away the template requires harsh chemicals. Heating hollow polystyrene nanospheres achieves similar results but offers poor control over the size and shape of the resulting carbon nanoparticles.
Li and co-workers combined a block copolymer called F127, consisting of poly(ethylene oxide) and poly(propylene oxide), with donut-shaped a-cyclodextrin molecules in water. After heating the mixture to 200°C, the molecules self-assembled into hollow nanoparticles with a 97.5% yield.
The water-repelling poly (propylene oxide) parts of the polymer stuck together to form hollow spheres, leaving poly (ethylene oxide) molecules dangling from the outside. The a-cyclodextrin rings then threaded onto these strands, packing around the outside of the sphere to form a stable shell. Using a higher proportion of F127 in the mix produced larger nanospheres, ranging from 200 to 400 nanometers in diameter. Heating these particles to 900°C in inert gases burned off the polymer to make hollow carbon nanoparticles.
The smallest nanospheres were 122 nanometers across and had 14 nanometer-thick walls dotted with tiny pores roughly 1 nanometer wide. Each gram of this material had a surface area of 317.5 square meters, which is greater than a tennis court.
The researchers used a slurry of particles to coat a copper foil and tested it as the anode in a lithium-ion battery. They found that the particles had a reversible charging capacity of 462 milliampere hours per gram - higher than graphite, a typical anode material - and could be recharged at least 75 times without significant loss of performance. The pores apparently allow lithium ions to migrate to the inside surfaces of the spheres. "Changing the porosity could improve the transport process for higher performance," suggests Li. The team now plans to incorporate metal and metal oxide materials into the hollow carbon nanospheres to further enhance their properties.
The A*STAR-affiliated researchers contributing to this research are from the Institute of Materials Research and EngineeringAssociated links
Electrical fields drive nano-machines a 100,000 times faster than previous methods
19.01.2018 | Technische Universität München
ISFH-CalTeC is “designated test centre” for the confirmation of solar cell world records
16.01.2018 | Institut für Solarenergieforschung GmbH
On the way to an intelligent laboratory, physicists from Innsbruck and Vienna present an artificial agent that autonomously designs quantum experiments. In initial experiments, the system has independently (re)discovered experimental techniques that are nowadays standard in modern quantum optical laboratories. This shows how machines could play a more creative role in research in the future.
We carry smartphones in our pockets, the streets are dotted with semi-autonomous cars, but in the research laboratory experiments are still being designed by...
What enables electrons to be transferred swiftly, for example during photosynthesis? An interdisciplinary team of researchers has worked out the details of how...
For the first time, scientists have precisely measured the effective electrical charge of a single molecule in solution. This fundamental insight of an SNSF Professor could also pave the way for future medical diagnostics.
Electrical charge is one of the key properties that allows molecules to interact. Life itself depends on this phenomenon: many biological processes involve...
At the JEC World Composite Show in Paris in March 2018, the Fraunhofer Institute for Laser Technology ILT will be focusing on the latest trends and innovations in laser machining of composites. Among other things, researchers at the booth shared with the Aachen Center for Integrative Lightweight Production (AZL) will demonstrate how lasers can be used for joining, structuring, cutting and drilling composite materials.
No other industry has attracted as much public attention to composite materials as the automotive industry, which along with the aerospace industry is a driver...
Scientists at Tokyo Institute of Technology (Tokyo Tech) and Tohoku University have developed high-quality GFO epitaxial films and systematically investigated their ferroelectric and ferromagnetic properties. They also demonstrated the room-temperature magnetocapacitance effects of these GFO thin films.
Multiferroic materials show magnetically driven ferroelectricity. They are attracting increasing attention because of their fascinating properties such as...
08.01.2018 | Event News
11.12.2017 | Event News
08.12.2017 | Event News
19.01.2018 | Materials Sciences
19.01.2018 | Health and Medicine
19.01.2018 | Physics and Astronomy