RMIT – Study unlocks full potential of graphene ‘supermaterial’


Drs. Esrafilzadeh and Jalili working on 3D-printed graphene mesh in the lab.
Credit: RMIT University

New research reveals why the “supermaterial” graphene has not transformed electronics as promised, and shows how to double its performance and finally harness its extraordinary potential.

Graphene is the strongest material ever tested. It’s also flexible, transparent and conducts heat and electricity 10 times better than copper.

After graphene research won the Nobel Prize for Physics in 2010 it was hailed as a transformative material for flexible electronics, more powerful computer chips and solar panels, water filters and bio-sensors. But performance has been mixed and industry adoption slow.

Now a study published in Nature Communications identifies silicon contamination as the root cause of disappointing results and details how to produce higher performing, pure graphene.

The RMIT University team led by Dr Dorna Esrafilzadeh and Dr Rouhollah Ali Jalili inspected commercially-available graphene samples, atom by atom, with a state-of-art scanning transition electron microscope.

“We found high levels of silicon contamination in commercially available graphene, with massive impacts on the material’s performance,” Esrafilzadeh said.

Testing showed that silicon present in natural graphite, the raw material used to make graphene, was not being fully removed when processed.

“We believe this contamination is at the heart of many seemingly inconsistent reports on the properties of graphene and perhaps many other atomically thin two-dimensional (2D) materials ,” Esrafilzadeh said.

Graphene has not become the next big thing because of silicon impurities holding it back, RMIT researchers have said.

Graphene was billed as being transformative, but has so far failed to make a significant commercial impact, as have some similar 2D nanomaterials. Now we know why it has not been performing as promised, and what needs to be done to harness its full potential.”

The testing not only identified these impurities but also demonstrated the major influence they have on performance, with contaminated material performing up to 50% worse when tested as electrodes.

“This level of inconsistency may have stymied the emergence of major industry applications for graphene-based systems.

But it’s also preventing the development of regulatory frameworks governing the implementation of such layered nanomaterials, which are destined to become the backbone of next-generation devices,” she said.

The two-dimensional property of graphene sheeting, which is only one atom thick, makes it ideal for electricity storage and new sensor technologies that rely on high surface area.

This study reveals how that 2D property is also graphene’s Achilles’ heel, by making it so vulnerable to surface contamination, and underscores how important high purity graphite is for the production of more pure graphene.

Using pure graphene, researchers demonstrated how the material performed extraordinarily well when used to build a supercapacitator, a kind of super battery.

When tested, the device’s capacity to hold electrical charge was massive. In fact, it was the biggest capacity so far recorded for graphene and within sight of the material’s predicted theoretical capacity.

In collaboration with RMIT’s Centre for Advanced Materials and Industrial Chemistry, the team then used pure graphene to build a versatile humidity sensor with the highest sensitivity and the lowest limit of detection ever reported.

These findings constitute a vital milestone for the complete understanding of atomically thin two-dimensional materials and their successful integration within high performance commercial devices.

“We hope this research will help to unlock the exciting potential of these materials.”

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Materials provided by RMIT University. Note: Content may be edited for style and length.


Journal Reference:

  1. Rouhollah Jalili, Dorna Esrafilzadeh, Seyed Hamed Aboutalebi, Ylias M. Sabri, Ahmad E. Kandjani, Suresh K. Bhargava, Enrico Della Gaspera, Thomas R. Gengenbach, Ashley Walker, Yunfeng Chao, Caiyun Wang, Hossein Alimadadi, David R. G. Mitchell, David L. Officer, Douglas R. MacFarlane, Gordon G. Wallace. Silicon as a ubiquitous contaminant in graphene derivatives with significant impact on device performance. Nature Communications, 2018; 9 (1) DOI: 10.1038/s41467-018-07396-3

Rapid Nano-filter for clean water: Australian researchers design a rapid nano-filter that cleans dirty water 100X faster than current technology


quickandnots
The new technology can filter drinking water 100 times faster than current tech. Credit: Free stock photo 

Australian researchers have designed a rapid nano-filter that can clean dirty water over 100 times faster than current technology.

Simple to make and simple to scale up, the technology harnesses naturally occurring nano-structures that grow on .

The RMIT University and University of New South Wales (UNSW) researchers behind the innovation have shown it can filter both heavy metals and oils from water at extraordinary speed.

RMIT researcher Dr. Ali Zavabeti said water contamination remains a significant challenge globally—1 in 9 people have no clean water close to home.

“Heavy  contamination causes serious health problems and children are particularly vulnerable,” Zavabeti said.

“Our new nano-filter is sustainable, environmentally-friendly, scalable and low cost.

“We’ve shown it works to remove lead and oil from water but we also know it has potential to target other common contaminants.

“Previous research has already shown the materials we used are effective in absorbing contaminants like mercury, sulfates and phosphates.

“With further development and commercial support, this new nano-filter could be a cheap and ultra-fast solution to the problem of .”

Quick and not-so-dirty: A rapid nano-filter for clean water
A liquid metal droplet with flakes of aluminium oxide compounds grown on its surface. Each 0.03mm flake is made up of about 20,000 nano-sheets stacked together. Credit: RMIT University

The liquid metal chemistry process developed by the researchers has potential applications across a range of industries including electronics, membranes, optics and catalysis.

“The technique is potentially of significant industrial value, since it can be readily upscaled, the liquid metal can be reused, and the process requires only short reaction times and low temperatures,” Zavabeti said.

Project leader Professor Kourosh Kalantar-zadeh, Honorary Professor at RMIT, Australian Research Council Laureate Fellow and Professor of Chemical Engineering at UNSW, said the liquid metal chemistry used in the process enabled differently shaped nano-structures to be grown, either as the atomically thin sheets used for the nano-filter or as nano-fibrous structures.

“Growing these materials conventionally is power intensive, requires high temperatures, extensive processing times and uses toxic metals. Liquid metal chemistry avoids all these issues so it’s an outstanding alternative.”

How it works

The groundbreaking technology is sustainable, environmentally-friendly, scalable and low-cost.

The researchers created an alloy by combining gallium-based liquid metals with aluminium.

When this alloy is exposed to water, nano-thin sheets of  compounds grow naturally on the surface.

These atomically thin layers—100,000 times thinner than a human hair—restack in a wrinkled fashion, making them highly porous.

Quick and not-so-dirty: A rapid nano-filter for clean water
Microscope image of nano-sheets, magnified over 11,900 times. Credit: RMIT University

This enables water to pass through rapidly while the aluminium oxide compounds absorbs the contaminants.

Experiments showed the nano-filter made of stacked atomically thin sheets was efficient at removing lead from water that had been contaminated at over 13 times safe drinking levels, and was highly effective in separating oil from water.

The process generates no waste and requires just aluminium and , with the liquid metals reused for each new batch of nano-structures.

The method developed by the researchers can be used to grow nano-structured materials as ultra-thin sheets and also as nano-fibres.

These different shapes have different characteristics—the ultra-thin sheets used in the nano-filter experiments have high mechanical stiffness, while the nano-fibres are highly translucent.

The ability to grow materials with different characteristics offers opportunities to tailor the shapes to enhance their different properties for applications in electronics, membranes, optics and catalysis.

The research is funded by the Australian Research Council Centre for Future Low-Energy Electronics Technologies (FLEET).

The findings are published in the journal Advanced Functional Materials.

 Explore further: Liquid metal discovery ushers in new wave of chemistry and electronics

More information: Advanced Functional Materials (2018). DOI: 10.1002/adfm.201804057

 

Solar paint offers endless energy from water vapor: Breakthrough by RMIT Researchers


Credit: CC0 Public Domain


Researchers have developed a solar paint that can absorb water vapour and split it to generate hydrogen – the cleanest source of energy.

The paint contains a newly developed compound that acts like silica gel, which is used in sachets to absorb moisture and keep food, medicines and electronics fresh and dry.

But unlike silica gel, the new material, synthetic molybdenum-sulphide, also acts as a semi-conductor and catalyses the splitting of water atoms into hydrogen and oxygen.

Lead researcher Dr Torben Daeneke, from RMIT University in Melbourne, Australia, said: “We found that mixing the compound with titanium oxide particles leads to a sunlight-absorbing paint that produces hydrogen fuel from solar energy and moist air.

“Titanium oxide is the white pigment that is already commonly used in wall paint, meaning that the simple addition of the new material can convert a brick wall into energy harvesting and fuel production real estate.

“Our new development has a big range of advantages,” he said. “There’s no need for clean or filtered water to feed the system. Any place that has water vapour in the air, even remote areas far from water, can produce fuel.”

 

His colleague, Distinguished Professor Kourosh Kalantar-zadeh, said hydrogen was the cleanest source of energy and could be used in fuel cells as well as conventional combustion engines as an alternative to fossil fuels.

“This system can also be used in very dry but hot climates near oceans. The sea water is evaporated by the hot sunlight and the vapour can then be absorbed to produce fuel.

“This is an extraordinary concept – making fuel from the sun and water vapour in the air.”

 

More information: Torben Daeneke et al, Surface Water Dependent Properties of Sulfur-Rich Molybdenum Sulfides: 
Electrolyteless Gas Phase Water Splitting, ACS Nano (2017). DOI: 10.1021/acsnano.7b01632
Provided by: RMIT University

Fern-Inspired Energy Storage Could Further Solar Power


fernThe breakthrough electrode prototype (right) can be combined with a solar cell (left) for on-chip energy harvesting and storage. Credit: RMIT University

A new type of electrode may help researchers finally solve one of the challenges preventing solar power from becoming a total energy solution.

RMIT University researchers believe a new graphene-based prototype— which is inspired by the structure of fern leaves— could boost the capacity of existing integrable storage by 3,000 percent and open a new path to the development of flexible thin film all-in-one solar capture and storage.

This advancement may lead to self-powering smart phones, laptops, cars and buildings.

The electrode is designed to work with supercapacitors, which can charge and discharge power significantly faster than conventional batteries. Supercapacitors have been combined with solar in the past, but their wider use as a storage solution is restricted because of their limited capacity.

The fractal design reflected the self-repeating shape of the veins of the western swordfern—Polystichum munitum—native to western North America.

RMIT’s Professor Min Gu explained how the prototype is based on the fern leaves.

RMIT images“The leaves of the western swordfern are densely crammed with veins, making them extremely efficient for storing energy and transporting water around the plant,” Gu, the leader of the Laboratory of Artificial Intelligence Nanophotonics and associate deputy vice-chancellor for Research Innovation and Entrepreneurship at RMIT, said in a statement.

Gu explained that the electrode is based on self-replicating fractal shapes and the researchers used the naturally-efficient design to improve solar energy storage at a nano level.

“The immediate application is combining this electrode with supercapacitors, as our experiments have shown our prototype can radically increase their storage capacity—30 times more than current capacity limits,” Gu said. “Capacity-boosted supercapacitors would offer both long-term reliability and quick-burst energy release for when someone wants to use solar energy on a cloudy day for example—making them ideal alternatives for solar power storage.”

Solar energy storage is an emerging technology that can promote the solar energy as the primary source of electricity. Recent developments of laser scribed graphene electrodes exhibiting a high electrical conductivity have enabled a green technology platform for supercapacitor-based energy storage, resulting in cost-effective, environment-friendly features and consequent readiness for on-chip integration.

According to the study, the new conceptual design removes the limit of the conventional planar supercapacitors by significantly increasing the ratio of active surface area to volume of the new electrodes and reducing the electrolyte ionic path.

The researchers combined the fractal-enabled laser-reduced graphene electrodes with supercapacitors to hold the stored charge for longer with minimal leakage.

Ph.D. researcher Litty Thekkekara explained that there are many applications for the prototype.

 “Flexible thin film solar could be used almost anywhere you can imagine, from building windows to car panels, smart phones to smart watches. We would no longer need batteries to charge our phones or charging stations for our hybrid cars. With this flexible electrode prototype we’ve solved the storage part of the challenge, as well as shown how they can work with solar cells without affecting performance,” she said.

“Now the focus needs to be on flexible solar energy, so we can work towards achieving our vision of fully solar-reliant, self-powering electronics.”

The study was published in Scientific Reports.

Nano-material to revolutionize computing


QDOTS imagesCAKXSY1K 8Nano-material to revolutionize computing

 

 

Jan 7, 2013, 05.37 PM IST: SYDNEY: A two-dimensional  nano-material could usher in nano-transistors and help revolutionise electronics, including ultra fast  computing, says an Australian research.

The new material – made up of layers of crystal known as molybdenum oxides – has unique properties that encourage the free flow of electrons at ultra-high speeds.

Researchers from Commonwealth Scientific and Industrial Research Organisation (CSIRO) explain how they adapted a revolutionary material known as graphene to create a new conductive nano-material, the journal Advanced Materials reports.

Graphene created by scientists in Britain won its inventors a  Nobel Prize in 2010. While the new material supports high speed electrons, its physical properties stump high-speed electronics, according to a  CSIRO statement.

Serge Zhuiykov from the CSIRO said the new nano-material was made up of layered sheets – similar to graphite layers that make up a pencil’s core.

“Within these layers, electrons are able to zip through at high speeds with minimal scattering,” Zhuiykov said.

“The importance of our breakthrough is how quickly and fluently electrons – which conduct electricity – are able to flow through the new material,” he added. Royal Melbourne Institute of Technology (RMIT) doctoral researcher Sivacarendran Balendhran led the study.

Kourosh Kalantar-zadeh, professor at the RMIT, said the researchers were able to remove “road blocks” that could obstruct the electrons, an essential step for the development of high-speed electronics.

“While more work needs to be done before we can develop actual gadgets using this new  2D nano-material, this breakthrough lays the foundation for a new electronics revolution and we look forward to exploring its potential,” he adds.