Novel Graphene Film Offers New Concept for Solar Energy and Solar Seawater Desalination


Ultrathin-graphene-film-for-solar-energy-image-img_assist-400x254

Researchers at Swinburne, the University of Sydney and Australian National University have collaborated to develop a solar absorbing, ultra-thin graphene-based film with unique properties that has great potential for use in solar thermal energy harvesting.

The 90 nanometre material is said to be a 1000 times finer than a human hair and is able to rapidly heat up to 160°C under natural sunlight in an open environment.

The team stated that this new graphene-based material may also open new avenues in:

  • thermophotovoltaics (the direct conversion of heat to electricity)
  • solar seawater desalination
  • infrared light source and heater
  • optical components: modulators and interconnects for communication devices
  • photodetectors
  • colorful display
  • It could possibly lead to the development of ‘invisible cloaking technology’ through developing large-scale thin films enclosing the objects to be ‘hidden’.

The researchers have developed a 2.5cm x 5cm working prototype to demonstrate the photo-thermal performance of the graphene-based metamaterial absorber. They have also proposed a scalable manufacturing strategy to fabricate the proposed graphene-based absorber at low cost.

“This is among many graphene innovations in our group,” says Professor Baohua Jia, Research Leader, Nanophotonic Solar Technology, in Swinburne’s Center for Micro-Photonics.

“In this work, the reduced graphene oxide layer and grating structures were coated with a solution and fabricated by a laser nanofabrication method, respectively, which are both scalable and low cost.”

‌‌“Our cost-effective and scalable graphene absorber is promising for integrated, large-scale applications that require polarisation-independent, angle insensitive and broad bandwidth absorption, such as energy-harvesting, thermal emitters, optical interconnects, photodetectors and optical modulators,” says first author of this research paper, Dr Han Lin, Senior Research Fellow in Swinburne’s Center for Micro-Photonics.

“Fabrication on a flexible substrate and the robustness stemming from graphene make it suitable for industrial use,” Dr Keng-Te Lin, another author, added.

“The physical effect causing this outstanding absorption in such a thin layer is quite general and thereby opens up a lot of exciting applications,” says Dr Bjorn Sturmberg, who completed his PhD in physics at the University of Sydney in 2016 and now holds a position at the Australian National University.

“The result shows what can be achieved through collaboration between different universities, in this case with the University of Sydney and Swinburne, each bringing in their own expertise to discover new science and applications for our science,” says Professor Martijn de Sterke, Director of the Institute of Photonics and Optical Science.

“Through our collaboration we came up with a very innovative and successful result. We have essentially developed a new class of optical material, the properties of which can be tuned for multiple uses.”

Source:  Swinburne
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“Nano-Wrinkles” (nano-structured surface coatings) would save Shipping and Aquaculture $$$$ Billions


nanowrinklesThe Nepenthes pitcher plant (left) and its nano-wrinkled ‘mouth’ (centre) inspired the engineered nanomaterial (right). Credit: Sydney Nano

A team of chemistry researchers from the University of Sydney Nano Institute has developed nanostructured surface coatings that have anti-fouling properties without using any toxic components.

Biofouling – the build-up of damaging biological material – is a huge economic issue, costing the aquaculture and shipping industries billions of dollars a year in maintenance and extra fuel usage. It is estimated that the increased drag on  due to biofouling costs the shipping industry in Australia $320 million a year a b.

Since the banning of the toxic anti-fouling agent tributyltin, the need for new non-toxic methods to stop marine biofouling has been pressing.

Leader of the research team, Associate Professor Chiara Neto, said: “We are keen to understand how these surfaces work and also push the boundaries of their application, especially for energy efficiency. Slippery coatings are expected to be drag-reducing, which means that objects, such as ships, could move through water with much less energy required.”

The new materials were tested tied to shark netting in Sydney’s Watson Bay, showing that the nanomaterials were efficient at resisting biofouling in a marine environment.

The research has been published in ACS Applied Materials & Interfaces.

Nanowrinkles could save billions in shipping and aquaculture
PhD candidate Sam Peppou Chapman in Watsons Bay, Sydney, next to the test samples of the nanomaterials attached to a shark net. Credit: University of Sydney Nano Institute

The new coating uses ‘nanowrinkles’ inspired by the carnivorous Nepenthes pitcher plant. The plant traps a layer of water on the tiny structures around the rim of its opening. This creates a slippery layer causing insects to aquaplane on the , before they slip into the pitcher where they are digested.

Nanostructures utilise materials engineered at the scale of billionths of a metre – 100,000 times smaller than the width of a human hair. Associate Professor Neto’s group at Sydney Nano is developing nanoscale materials for future development in industry.

Biofouling can occur on any surface that is wet for a long period of time, for example aquaculture nets, marine sensors and cameras, and ship hulls. The slippery surface developed by the Neto group stops the initial adhesion of bacteria, inhibiting the formation of a biofilm from which larger marine fouling organisms can grow.

The interdisciplinary University of Sydney team included biofouling expert Professor Truis Smith-Palmer of St Francis Xavier University in Nova Scotia, Canada, who was on sabbatical visit to the Neto group for a year, partially funded by the Faculty of Science scheme for visiting women.

In the lab, the slippery surfaces resisted almost all fouling from a common species of marine bacteria, while control Teflon samples without the lubricating layer were completely fouled. Not satisfied with testing the surfaces under highly controlled lab conditions with only one type of bacteria the team also tested the surfaces in the ocean, with the help of marine biologist Professor Ross Coleman.

Test surfaces were attached to swimming nets at Watsons Bay baths in Sydney Harbour for a period of seven weeks. In the much harsher marine environment, the slippery surfaces were still very efficient at resisting fouling.

The antifouling coatings are mouldable and transparent, making their application ideal for underwater cameras and sensors.

 Explore further: Researchers show laser-induced graphene kills bacteria, resists biofouling

More information: Cameron S. Ware et al, Marine Antifouling Behavior of Lubricant-Infused Nanowrinkled Polymeric Surfaces, ACS Applied Materials & Interfaces (2017). DOI: 10.1021/acsami.7b14736

 

Tiny ‘Lego’ blocks Build Janus nanotubes: For NEW drugs and water purification


Nanotubes images(Nanowerk News) Researchers have created tiny protein  tubes named after the Roman god Janus which may offer a new way to accurately  channel drugs into the body’s cells.
Using a process which they liken to molecular Lego, scientists  from the University of Warwick and the University of Sydney have created what  they have named ‘Janus nanotubes’ – very small tubes with two distinct faces.  The study is published in the journal Nature Communications (“Janus cyclic peptide–polymer nanotubes”).
They are named after the Roman god Janus who is usually depicted  as having two faces, since he looks to the future and the past.
The Janus nanotubes have a tubular structure based on the  stacking of cyclic peptides, which provide a tube with a channel of around 1nm –  the right size to allow small molecules and ions to pass through.
Attached to each of the cyclic peptides are two different types  of polymers, which tend to de-mix and form a shell for the tube with two faces –  hence the name Janus nanotubes.
The faces provide two remarkable properties – in the solid  state, they could be used to make solid state membranes which can act as  molecular ‘sieves’ to separate liquids and gases one molecule at a time. This  property is promising for applications such as water purification, water  desalination and gas storage.
In a solution, they assemble in lipids bilayers, the structure  that forms the membrane of cells, and they organise themselves to form pores  which allow the passage of molecules of precise sizes. In this state they could  be used for the development of new drug systems, by controlling the transport of  small molecules or ions inside cells.
Sebastien Perrier of the University of Warwick said: “There is  an extraordinary amount of activity inside the body to move the right chemicals  in the right amounts both into and out of cells.
“Much of this work is done by channel proteins, for example in  our nervous system where they modulate electrical signals by gating the flow of  ions across the cell membrane.
“As ion channels are a key component of a wide variety of  biological process, for example in cardiac, skeletal and muscle contraction,  T-cell activation and pancreatic beta-cell insulin release, they are a frequent  target in the search for new drugs.
“Our work has created a new type of material – nanotubes – which  can be used to replace these channel processes and can be controlled with a much  higher level of accuracy than natural channel proteins.
“Through a process of molecular engineering – a bit like  molecular Lego – we have assembled the nanotubes from two types of building  blocks – cyclic peptides and polymers.
“Janus nanotubes are a versatile platform for the design of  exciting materials which have a wide range of application, from membranes – for  instance for the purification of water, to therapeutic uses, for the development  of new drug systems.”
Source: University of Warwick
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