Nav: Home

A new way to atomically thin materials

April 04, 2018

Metallic conductivity and hydrophilicity of MXenes have established them as electrodes in rechargeable batteries and supercapacitors, as well as other applications, including photothermal cancer therapy, electromagnetic shielding, water purification and gas sensing. In the journal Angewandte Chemie, researchers have now introduced a new production method. Instead of using conventional, yet more expensive, titanium aluminum carbide, they selectively etch silicon out of titanium silicon carbide, a cheaper and more common precursor, to synthesize titanium carbide.

Two-dimensional materials, consisting of extremely thin layers that are a few atoms thick, have unique properties that are completely different than the normal three-dimensional versions. A prominent example of this is graphene, which is made of single layers of carbon atoms. In 2011, a new class of two-dimensional materials was synthesized at Drexel University in Philadelphia (Pennsylvania, USA). Known as MXenes, the materials are made of transition metal carbides and nitrides, where the M stands for a transition metal, such as titanium, vanadium, or molybdenum, X can be carbon and/or nitrogen, and many compositions are available (about 30 have already been experimentally demonstrated and dozens more are expected). One such MXene is titanium carbide, Ti(3)C(2).

Obtaining the desired MXene usually involves a roundabout process: Layered carbides and nitrides, known as MAX phases, are selectively etched with hydrofluoric acid to remove the layers of the "A" element, which is a group 13 or 14 element such as aluminum, silicon, or germanium. In this way, titanium carbide can be obtained by etching the aluminum out of titanium aluminum carbide (Ti(3)AlC(2)). However, this starting material is expensive, and the production is complex. In contrast, the silicon analog, titanium silicon carbide (Ti(3)SiC(2)), is commercially available and less expensive. Ti(3)SiC(2 )was the first MAX phase Drexel researchers tried to selectively etch in 2011, but synthesis failed using hydrofluoric acid alone because the silicon atoms are strongly bound to the adjacent transition metal atoms.

A team led by Yury Gogotsi at Drexel University has now developed a successful variation of this process. By adding an oxidizing agent, the researchers could weaken the silicon bonds and oxidize silicon. Using mixtures of hydrofluoric acid and an oxidizing agent like nitric acid, hydrogen peroxide, or potassium permanganate, the team produced titanium carbide MXene by selectively removing silicon out of Ti(3)SiC(2).

The etching process leaves behind stacks of titanium carbide, which can be delaminated to make flakes, which are approximately 1 nanometer in thickness. The researchers used this method to make flexible, electrically conducting titanium carbide films on a relatively large scale.

This new method could make the production of MXenes easier, and open pathways to the production of new MXenes and related two-dimensional materials from silicon-containing precursors, expanding the family of 2D nanosheets available to scientists and engineers.
About the Author

Dr. Yury Gogotsi is Charles T. and Ruth M. Bach Distinguished University Professor and Director of the A. J. Drexel Nanomaterials Institute at Drexel University. His group works on synthesis, chemical modification, and applications of nanomaterials. He is a recipient of many international awards for his work on carbon materials and electrochemical capacitors.


Related Silicon Articles:

Flexible thinking on silicon solar cells
Combining silicon with a highly elastic polymer backing produces solar cells that have record-breaking stretchability and high efficiency.
No storm in a teacup -- it's a cyclone on a silicon chip
University of Queensland researchers have combined quantum liquids and silicon-chip technology to study turbulence for the first time, opening the door to new navigation technologies and improved understanding of the turbulent dynamics of cyclones and other extreme weather.
Researchers discover new way to split and sum photons with silicon
A team of researchers at The University of Texas at Austin and the University of California, Riverside have found a way to produce a long-hypothesized phenomenon -- the transfer of energy between silicon and organic, carbon-based molecules -- in a breakthrough that has implications for information storage in quantum computing, solar energy conversion and medical imaging.
Black silicon can help detect explosives
Scientists from Far Eastern Federal University (FEFU), Far Eastern Branch of the Russian Academy of Sciences, Swinburne University of Technology, and Melbourne Center for Nanofabrication developed an ultrasensitive detector based on black silicon.
2D antimony holds promise for post-silicon electronics
Researchers in the Cockrell School of Engineering are searching for alternative materials to silicon with semiconducting properties that could form the basis for an alternative chip.
Silicon technology boost with graphene and 2D materials
In a review published in Nature, ICFO researchers and collaborators report on the current state, challenges, opportunities of graphene and 2D material integration in Silicon technology.
Light and sound in silicon chips: The slower the better
Acoustics is a missing dimension in silicon chips because acoustics can complete specific tasks that are difficult to do with electronics and optics alone.
Silicon as a semiconductor: Silicon carbide would be much more efficient
In power electronics, semiconductors are based on the element silicon -- but the energy efficiency of silicon carbide would be much higher.
New insight into glaciers regulating global silicon cycling
A new review of silicon cycling in glacial environments, led by scientists from the University of Bristol, highlights the potential importance of glaciers in exporting silicon to downstream ecosystems.
Understanding the (ultra-small) structure of silicon nanocrystals
New research provides insight into the structure of silicon nanocrystals, a substance that promises to provide efficient lithium ion batteries that power your phone to medical imaging on the nanoscale.
More Silicon News and Silicon Current Events

Trending Science News

Current Coronavirus (COVID-19) News

Top Science Podcasts

We have hand picked the top science podcasts of 2020.
Now Playing: TED Radio Hour

Climate Mindset
In the past few months, human beings have come together to fight a global threat. This hour, TED speakers explore how our response can be the catalyst to fight another global crisis: climate change. Guests include political strategist Tom Rivett-Carnac, diplomat Christiana Figueres, climate justice activist Xiye Bastida, and writer, illustrator, and artist Oliver Jeffers.
Now Playing: Science for the People

#562 Superbug to Bedside
By now we're all good and scared about antibiotic resistance, one of the many things coming to get us all. But there's good news, sort of. News antibiotics are coming out! How do they get tested? What does that kind of a trial look like and how does it happen? Host Bethany Brookeshire talks with Matt McCarthy, author of "Superbugs: The Race to Stop an Epidemic", about the ins and outs of testing a new antibiotic in the hospital.
Now Playing: Radiolab

Speedy Beet
There are few musical moments more well-worn than the first four notes of Beethoven's Fifth Symphony. But in this short, we find out that Beethoven might have made a last-ditch effort to keep his music from ever feeling familiar, to keep pushing his listeners to a kind of psychological limit. Big thanks to our Brooklyn Philharmonic musicians: Deborah Buck and Suzy Perelman on violin, Arash Amini on cello, and Ah Ling Neu on viola. And check out The First Four Notes, Matthew Guerrieri's book on Beethoven's Fifth. Support Radiolab today at