For perfect nano-crystals, just add water

Jul 10, 2013
For perfect nano-crystals just add water
Cerium (IV) dimers and trimers form in aqueous solution nanometer-sized cerium dioxide crystals (CeO2). The size of the nanocrystals is in the order of two to three nanometers. Credit: Dr Atsushi Ikeda-Ohno

A simplified technique to fabricate nano-crystals of cerium dioxide (CeO2), which have wide-ranging technological and industrial applications, has been "unexpectedly" demonstrated by a UNSW chemist.

The UNSW-led study reveals that nano-crystals form naturally when a precursor material – Cerium (IV) – is dissolved and hydrolysed in water. It is the first time this formation process has been observed.

The findings, reported in Chemistry – A European Journal, could simplify the existing production process, which requires heating and the addition of chemicals to better control the crystals' shape and size.

"The most important finding is that cerium (IV) has an intrinsic nature to form uniformly sized nano-crystals of cerium dioxide of approximately two to three nanometres in an aqueous solution via ," says lead author Dr Atsushi Ikeda-Ohno from the UNSW School of Civil and Environmental Engineering.

"The outcomes of this study provide a basic concept to simplify and alleviate the production process and means we only need to adjust the pH of the … without heating or adding chemicals," he says. "This could save money on and help reduce the environmental impact of the whole production process."

Cerium dioxide nano-crystals are formed from the Cerium. They are used as catalysts to treat hazardous gases – converting into less ; as electrodes in fuel cells; and in and cosmetics due to their capacity to absorb high levels of UV radiation.

There is growing interest in the fabrication of these materials, given their wide-ranging applications, but there is relatively little known about the mechanisms that govern their formation. These mechanisms are directly linked to the ability to control their shape and size – features that govern a crystal's functionality.

One of the largest barriers to studying these formation mechanisms has been a lack of analytical tools to do so in-situ, says Ikeda-Ohno.

His study was initially focused on observing the effect of hydrolysis on Cerium (IV) and developing an improved analytical strategy, using a combination of spectroscopic tools, to observe and better understand the formation process. But then something unexpected happened.

"When I first investigated apparently-transparent solutions of Cerium (IV) at different pH by using an X-ray technique I realised that the solutions were not composed of simple dissolved species…but contained very tiny colloidal particles which are not visually recognisable," he said.

After applying additional spectroscopic and microscopic techniques to characterise these mysterious particles, he determined that they were in fact cerium dioxide nano-crystals.

"As a consequence, we have succeeded in observing the whole evolution process from the precursor species into Cerium dioxide nano-crystals," the report states.

"In this study I have demonstrated that a combination of advanced analytical techniques, particularly synchrotron-based X-ray techniques… provide a very powerful tool to probe the evolution of metal nano-crystals in-situ," says Ikeda-Ohno.

"A full understanding of the 'evolution' process from the precursor species into the resultant nano-crystals possibly enables us to tailor these materials to practical needs."

The next step toward realising the hydrolysis-based fabrication technique is to identify the critical pH condition at which the nano-crystals begin to form. Ikeda-Ohno says the approach he's developed could be used to that end, and could also be applied to other metal nano-crystals.

Explore further: Efficient production process for coveted nanocrystals

More information: onlinelibrary.wiley.com/doi/10.1002/chem.201204101/abstract

Related Stories

Efficient production process for coveted nanocrystals

Jun 25, 2013

A formation mechanism of nanocrystalline cerium dioxide (CeO2), a versatile nanomaterial, has been unveiled by scientists from the Helmholtz-Zentrum Dresden-Rossendorf (HZDR) and the University of New South ...

Uranium crystals could reveal future of nuclear fuel

Jun 25, 2013

Mention the word "crystals" and few people think of nuclear fuel. Unless you are Eric Burgett. The Idaho State University professor is on a quest to create pure, single crystals of uranium and uranium oxide ...

Cerium's unusual behaviour

Jan 27, 2011

(PhysOrg.com) -- Livermore researchers have found that a crystal of cerium -- the chemical element that can be used for catalysts and fuel additives -- behaves in very unique ways when subjected to high pressures.

Rare earth metal enhances phosphate glass

Dec 15, 2009

(PhysOrg.com) -- Adding cerium oxide to phosphate glass rather than the commonly used silicate glass may make glasses that block ultraviolet light and have increased radiation damage resistance while remaining colorless, ...

Weird science: Crystals melt when they're cooled

May 23, 2013

(Phys.org) —Growing thin films out of nanoparticles in ordered, crystalline sheets, to make anything from microelectronic components to solar cells, would be a boon for materials researchers, but the physics ...

First opal-like crystals discovered in meteorite

Aug 03, 2011

Scientists have found opal-like crystals in the Tagish Lake meteorite, which fell to Earth in Canada in 2000. This is the first extraterrestrial discovery of these unusual crystals, which may have formed in the primordial ...

Recommended for you

Making graphene in your kitchen

14 hours ago

Graphene has been touted as a wonder material—the world's thinnest substance, but super-strong. Now scientists say it is so easy to make you could produce some in your kitchen.

Thinnest feasible nano-membrane produced

Apr 17, 2014

A new nano-membrane made out of the 'super material' graphene is extremely light and breathable. Not only can this open the door to a new generation of functional waterproof clothing, but also to ultra-rapid filtration. The ...

Wiring up carbon-based electronics

Apr 17, 2014

Carbon-based nanostructures such as nanotubes, graphene sheets, and nanoribbons are unique building blocks showing versatile nanomechanical and nanoelectronic properties. These materials which are ordered ...

Making 'bucky-balls' in spin-out's sights

Apr 16, 2014

(Phys.org) —A new Oxford spin-out firm is targeting the difficult challenge of manufacturing fullerenes, known as 'bucky-balls' because of their spherical shape, a type of carbon nanomaterial which, like ...

User comments : 0

More news stories

Making graphene in your kitchen

Graphene has been touted as a wonder material—the world's thinnest substance, but super-strong. Now scientists say it is so easy to make you could produce some in your kitchen.

Finnish inventor rethinks design of the axe

(Phys.org) —Finnish inventor Heikki Kärnä is the man behind the Vipukirves Leveraxe, which is a precision tool for splitting firewood. He designed the tool to make the job easier and more efficient, with ...