The nanoscale is so tiny it’s almost beyond comprehension. Too small for detection by the human eye, and not even discernible by most laboratory microscopes, it refers to measurements in the range of 1–100 billionths of a metre. The nanoscale is the level at which atoms and molecules come together to form structured materials.
The Nanochemistry Research Institute — NRI — conducts fundamental and applied research to understand, model and tailor materials at the nanoscale. It brings together scientists – with expertise in chemistry, engineering, computer simulations, materials and polymers – and external collaborators to generate practical applications in health, energy, environmental management, industry and exploration. These include new tests for cancer, and safer approaches to oil and gas transportation. Research ranges from government-funded exploratory science to confidential industry projects.
The NRI hosts research groups with specialist expertise in the chemical formation of minerals and other materials. “To understand minerals, it’s often important to know what is going on at the level of atoms,” explains Julian Gale, John Curtin Distinguished Professor in Computational Chemistry and former Acting Director of the NRI. “To do this, we use virtual observation – watching how atoms interact at the nanoscale – and modelling, where we simulate the behaviour of atoms on a computer.”
The mineral calcium carbonate is produced through biomineralisation by some marine invertebrates. “If we understand the chemistry that leads to the formation of carbonates in the environment, then we can look at how factors such as ocean temperature and pH can lead to the loss of minerals that are a vital component of coral reefs,” says Gale.
This approach could be used to build an understanding of how minerals are produced biologically, potentially leading to medical and technological benefits, including applications in bone growth and healing, or even kidney stone prevention and treatment.
Gale anticipates that a better understanding of mineral geochemistry may also shed light on how and where metals are distributed. “If you understand the chemistry of gold in solution and how deposits form, you might have a better idea where to look for the next gold mine,” he explains.
There are also environmental implications. “Formation of carbonate minerals, especially magnesium carbonate and its hydrates, has been proposed as a means of trapping atmospheric carbon in a stable solid state through a process known as geosequestration. We work with colleagues in the USA to understand how such carbonates form,” says Gale.
Minerals science is also relevant in industrial settings. Calcium carbonate scaling reduces flow rates in pipes and other structures in contact with water. “As an example, the membranes used for reverse osmosis in water desalination – a water purification technology that uses a semipermeable membrane to remove salt and other minerals from saline water – can trigger the formation of calcium carbonate,” explains Gale. “This results in partial blockage of water flow through the membrane, and reduced efficiency of the desalination process.”
A long-term aim of research in this area is to design water membranes that prevent these blockages. There are also potential applications in the oil industry, where barium sulphate (barite) build-up reduces the flow in pipes, and traps dangerous radioactive elements such as radium.
Another problem for exploration companies is the formation of hydrates of methane and other low molecular weight hydrocarbon molecules. These can block pipelines and processing equipment during oil and gas transportation and operations, which results in serious safety and flow assurance issues. Materials chemist Associate Professor Xia Lou leads a large research group in the Department of Chemical Engineering that is developing low-dose gas hydrates inhibitors to prevent hydrate formation. “We also develop nanomaterials for the removal of organic contaminants in water, and nanosensors to detect or extract heavy metals,” she says.
“To understand minerals, it’s often important to know what is going on at the level of the atom.”
The capacity to control how molecules come together and then disassociate offers tantalising opportunities for product development, particularly in food science, drug delivery and cosmetics. In the Department of Chemistry, Professor Mark Ogden conducts nanoscale research looking at hydrogels, or networks of polymeric materials suspended in water.
“We study the 3D structure of hydrogels using the Institute’s scanning probe microscope,” says Ogden. “The technique involves running a sharp tip over the surface of the material. It provides an image of the topography of the surface, but we can also measure how hard, soft or sticky the surface is.” Ogden is developing methods for watching hydrogels grow and fall apart through heating and cooling. “We have the capability to do that sort of imaging now, and this in situ approach is quite rare around the world,” he says.
Ogden also conducts chemical research with a group of metals known as lanthanoids, which are rare-earth elements. His recent work, in collaboration with the Australian Nuclear Science and Technology Organisation (ANSTO), discovered unique elongated nanoscale structures.
“We’ve identified lanthanoid clusters that can emit UV light and have magnetic properties,” explains Ogden. “Some of these can form single molecule magnets. A key outcome will be to link cluster size and shape to these functional properties.” This may facilitate guided production of magnetic and light-emitting materials for use in sensing and imaging technologies.
“If you understand the chemistry of gold … then you might have a better idea of where to start looking for the next gold mine.”
The NRI is working across several areas of chemistry and engineering to develop nanoscale tools for detecting and treating health conditions. Professor Damien Arrigan applies a nanoscale electrochemical approach to detecting biological molecules, also known as biosensing. He and his Department of Chemistry colleagues work at the precise junction between layered oil and water.
“We make oil/water interfaces using membranes with nanopores, some as small as 15 nanometres,” he says. “This scale delivers the degree of sensitivity we’re after.” The scientists measure the passage of electrical currents across the tiny interfaces and detect protein, which absorbs at the boundary between the two liquids. “As long as we know a protein’s isoelectric point – that is, the pH at which it carries no electrical charge – we can measure its concentration,” he explains.
The technique enables the scientists to detect proteins at nanomolar (10−6 mol/m3) concentrations, but they hope to shift the sensitivity to the picomolar (10−9 mol/m3) range – a level of detection a thousand times more sensitive and not possible with many existing protein assessments. Further refinement may also incorporate markers to select for proteins of interest. “What we’d like to do one day is measure specific proteins in biological fluids like saliva, tears or serum,” says Arrigan.
The team’s long-term vision is to develop highly sensitive point-of-need measurements to guide treatments – for example, testing kits for paramedics to detect markers released after a heart attack so that appropriate treatment can be immediately applied.
Also in the Department of Chemistry, Dr Max Massi is developing biosensing tools to look at the health of living tissues. His approach relies on tracking the location and luminescence of constructed molecules in cells. “We synthesise new compounds based on heavy metals that have luminescent properties,” explains Massi. “Then we feed the compounds to cells, and look to see where they accumulate and how they glow.”
The team synthesises libraries of designer chemicals for their trials. “We know what properties we’re after – luminescence, biological compatibility and the ability to go to the part of the cell we want,” says Massi.
For example, compounds can be designed to accumulate in lysosomes – the tiny compartments in a cell that are involved in functions such as waste processing. With appropriate illumination, images of lysosomes can then be reconstructed and viewed in 3D using a technique known as confocal microscopy, enabling scientists to assess lysosome function. Similar approaches are in development for disease states such as obesity and cancer.
Beyond detection, this technique also has potential for therapeutic applications. Massi has performed in vitro studies with healthy and cancerous cells, suggesting that a switch from detection to treatment may be possible by varying the amount of light used to illuminate the cells.
“A bit of light allows you to visualise. A lot of light will allow you to kill the cells,” explains Massi. His approach is on track for product development, with intellectual property protection filed in relation to using phosphorescent compounds to determine the health status of cells.
Improving approaches to cancer treatment is also an ongoing research activity for materials chemist Dr Xia Lou, who designs, constructs and tests nanoparticles for targeted photodynamic therapy, which aims to selectively kill tumours using light-induced reactive oxygen species.
“We construct hybrid nanoparticles with high photodynamic effectiveness and a tumour-targeting agent, and then test them in vitro in our collaborators’ laboratories,” she says. “Our primary interest is in the treatment of skin cancer. The technology has also extended applications in the treatment of other diseases.” Lou has successfully filed patents for cancer diagnosis and treatment that support the potential of this approach.
Spheres and other 3D shapes constructed at the nanoscale offer potential for many applications centred on miniaturised storage and release of molecules and reactivity with target materials. Dr Jian Liu in the Department of Chemical Engineering develops new synthesis strategies for silica or carbon spheres, or ‘yolk-shell’-structured particles. “Our main focus is the design, synthesis and application of colloidal nanoparticles including metal, metal oxides, silica and carbon,” says Liu.
Most of these colloidal particles are nanoporous – that is, they have a lattice-like structure with pores throughout. The applications of such nanoparticles include catalysis, energy storage and conversion, drug delivery and gene therapy.
“The most practical outcome of our research would be the development of new catalysts for the production of synthetic gases, or syngas,” he says. “It may also lead to new electrodes for lithium-ion batteries.” Once developed, nanoscale components for this type of rechargeable battery are expected to bring improved safety and durability, and lower costs.
Atomic Modelling matters in research
Professor Julian Gale leads a world-class research group in computational materials chemistry at the NRI. “We work at the atomic level, looking at fundamental processes by which materials form,” he says. “We can simulate up to a million atoms or more, and then test how the properties and behaviour of the atoms change in response to different experimental conditions.” Such research is made possible through accessing a petascale computer at WA’s Pawsey Centre – built primarily to support Square Kilometre Array pathfinder research.
The capacity to model the nanoscale behaviour of atoms is a powerful tool in nanochemistry research, and can give direction to experimental work. The calcium carbonate mineral vaterite is a case in point. “Our theoretical work on calcium carbonate led to the proposal that the mineral vaterite was actually composed of at least three different forms,” Gale explains. “An international team found experimental evidence which supported this idea.”
NRI Director Professor Andrew Lowe regards this capacity as an asset. “Access to this kind of atomic modelling means that our scientists can work within a hypothetical framework to test whether a new idea is likely to work or not before they commit time and money to it,” he explains.
New direction
Formally established in 2001, the Nanochemistry Research Institute began a new era in 2015 through the appointment of Professor Andrew Lowe as Director. Working under his guidance are academic staff and postdoctoral fellows, as well as PhD, Honours and undergraduate science students.
An expert in polymer chemistry, Lowe’s research background adds a new layer to the existing strong multidisciplinary nature of the Institute. “Polymers have the potential to impact on every aspect of fundamental research,” he says. “This will add a new string to the bow of Curtin University science and engineering, and open new and exciting areas of research and collaboration.”
Polymers are a diverse group of materials composed of multiple repeated structural units connected by chemical bonds. “My background is in water-soluble polymers and smart polymers,” explains Lowe. “These materials change the way they behave in response to their external environment – for example, a change in temperature, salt concentrations, pH or the presence of other molecules including biomolecules. Because the characteristics of the polymeric molecules can be altered in a reversible manner, they offer potential to be used in an array of applications, including drug delivery, catalysis and surface modification.”
Lowe has particular expertise in RAFT dispersion polymerisation, a technique facilitating molecular self-assembly to produce capsule-like polymers in solution. “This approach allows us to make micelles, worms and vesicles directly,” he says, describing the different physical forms the molecules can take. “It’s a novel and specialised technique that creates high concentrations of uniformly-shaped polymeric particles at the nanoscale.” Such polymers are candidates for drug delivery and product encapsulation.
– Sarah Keenihan