July 2013

Coatings of nanotube forests developed by NASA are the blackest materials ever measured, which has great importance for many scientific processes. The NASA team has worked for several years to make their formulation black over a wide spectral range and to improve the robustness and the number of materials to which the nanotubes can be applied. With assistance from MCN NASA is further developing carbon nanotube technology for use on parts with complex shapes.

Principal Investigator John Hagopian and co-investigator Vivek Dwivedi of the NASA Goddard Space Flight Center are using Atomic Layer Deposition (ALD) to deposit layered thin-films suitable for carbon nanotube growth on intricate parts.

To gain the highest sensitivity and consistent measurements, carbon nanotubes must be evenly deposited across the surface of the detection component. This requires a highly uniform foundation layer, commonly a film of nanoparticles or iron oxide, to support growth of the carbon nanotubes. This is difficult to achieve using deposition techniques such as sputtering or evaporation because corners and crevasses are left uncoated and there is a large variation in the thickness of the coating. ALD is one technique that can coat all surfaces of an intricate object in a highly controlled and uniform layer.

The NASA researchers worked with MCN’s operating expert in ALD, Dr. Lachlan Hyde to perform a number of iterations for ALD growth of iron thin films. Dr. Hyde used MCN’s spectroscopic variable angle ellipsometer for characterisation, allowing the film thickness and uniformity to be optimised on test wafers.

MCN provided the NASA team with development samples and a detailed report on the process, including development recipes and analysis of ALD film growth. Hagopian and Dwivedi have since conducted trial production of carbon nanotubes on these wafers at NASA.

“We have successfully performed growth on two development samples with an ALD iron catalyst from MCN and the nanotubes have properties very similar to those grown using electron beam deposited catalysts,” Hagopian said.

“Both their ALD process development and characterisation capabilities are world-class. We intend to continue our collaboration and look for additional opportunities to leverage their capabilities to increase our speed of technology development.”

July 2013

Black silicon provides a unique platform for a non-reflecting, all-direction-absorbing surface, which can be used for sensing and fingerprinting of molecular and microbial contamination. This is done by sensing the light scattered in air, water, food, body fluids by various compounds.

Detection of dyes from a family of carcenogenic compounds was made using black silicon. Nano-textured surfaces of black silicon are suitable as practical, cheap, single-use substrates for efficient measurements in water, food or medical fields. Their sensitivity of detection is superior to the commercial Klarite substrates currently used in industry.

A team of MCN engineers and Swinburne PhD students led by Professor Saulius Juodkazis perfected efficient, large-area fabrication of black silicon using plasma processing, after which they carried our different characterisation tests. These showed that black silicon substrates can be used as substrates for laser fabrication, sensors for light scattering and detection of tiny numbers of molecules. Black silicon is highly absorbant of light rays, with only 1% of light reflected from its surface, as opposed to the usual 35% of reflected light on other materials.

The most interesting outcome of this project is the demonstration that black silicon can be used as a sensing substrate. This was not initially obvious as the low reflectivity makes it a challenge to detect light scattered from black silicon. The group showed that this is not an issue for reaching high sensitivity performance. This is significant as a few millimetres of commercially available Klarite sensors cost more than a few inches of black silicon.

Single use sensors are must in the medical, food, water and air control industries. Black silicon can become a platform to develop such sensors using new, label-free and established surface functionalisation technologies.

The group plans to fabricate die-chips of black silicon for sensing and make them ready to use after coating with gold film. Black silicon substrates are promising for bio-physics research with the possibility for strongly influencing cell membrane functions with nano-needles of black silicon.

July 2013

Development of a new, ultra-thin 2D optical material enables the rapid, sensitive and inexpensive detection of toxic chemicals in air, water and soil.

Surface Enhanced Raman Scattering (SERS) is an extremely powerful technique with the potential to identify fingerprint vibrations of trace chemical species. However, the high cost, portability and reproducibility are factors which prevent SERS from widespread use - commercially available Klarite^® SERS substrates cost around $40 dollars. In addition, SERS-active structures are supported on rigid glass surfaces, which limits where can Klarite^® SERS substrate be used. This makes it difficult for trace chemical identification on a topographically complex surfaces such as door handles.

To combat these problems, Associate Professor Wenlong Cheng has used nanofabrication facilities at MCN to successfully fabricate ultra-thin, plasmonic nanosheets for rapid, inexpensive and sensitive detection of toxic species in air, water and solids.

Associate Professor Cheng’s group has developed simple, yet efficient wet chemical nanofabrication approaches to obtain free-standing, monolayered, highly-ordered plasmonic nanosheets. The sheets could be as thin as 2.5nm but could have macroscopic lateral dimensions, corresponding to an aspect ratio of above 1 million. Such nanosheets are high-performance SERS substrates which achieve at least 10 times more sensitivity than commercial Klarite^® SERS substrate.

The unique technology developed for ultrathin 2D optical has potentially huge impacts in society. This may include smart diagnostics, better displays, and more efficient solar energy systems. The project is currently expanding the potential to translate the technology into real-world products.

You can read more about this project in Free-Standing Plasmonic-Nanorod Superlattice Sheets, published in ACS Nano.

July 2013

Graphene is the new kid on the block for electronics as well as photonics. The atomically thin material is stronger than steel and more conducting than copper, making it an ideal candidate for thin, fast and robust electronics.

The unique properties of graphene allow multiple functions of signal emitting, transmitting, modulating and detection to be realised in one material. Graphene shows superior properties to silicon and III-V semiconductors in terms of its high thermal conductivity, high optical damage threshold, and high third-order optical nonlinearities. These macro-scale properties are important for photonic devices. Furthermore, the fabrication of graphene-based devices is compatible with existing semiconductor processes. The complementary role of graphene to silicon photonics inspires the design of new structures targeted to improve the figures of merit in optical modulation and photodetection, which include optical response, optical bandwidth, and area efficiency.

By taking advantage of graphene’s infinitesimal thinness and ultra-wideband electro-optical response, Dr. Qiaoliang Bao from Monash University is able to fabricate the smallest optical modulation device and the thinnest photodetector. His work will offer one of the most promising approaches to achieve the high-density electronic/photonic integration necessary for the optical interconnects required in high performance computing.

The present state of development in integrated photonics can be compared to the situation before the integrated circuit revolution more than 50 years ago. Breakthroughs similar to what silicon transistors had achieved are expected for integrated photonics. Graphene-based photonics devices will deliver much better performance as well as many new functions to fulfil the stringent demands for broadband data transferring and translating. Conventionally used silicon-based materials are not broadband optical materials, which is where graphene-based devices have so much potential.

The fabrication of graphene-based optical modulator is compatible with existing silicon-based nanofabrication processes, which is one of the core expertise at MCN. The state-of-the-art lithographical tools, variety of thin film deposition systems, advanced characterisation tools and optoelectronic measurement systems available at MCN are highly important for the success of this research.

You can read more about this work in Graphene Photonics, Plasmonics, and Broadband Optoelectronic Devices, published in ACS Nano.

July 2013

Cellular imaging is an essential tool for understanding the biological functions that occur in all living organisms. X-rays provide a path to imaging the internal structure of cells without needing to cross-section them, which can often lead to damage of the cell structure. Two of the major barriers to x-rays being applied to x-ray imaging has been the lack of high spatial resolution and the damage that the x-rays can cause after the long exposures needed to form high-quality absorption images. In this work, Dr. Brian Abbey together with colleagues from La Trobe University, developed a new microscopy technique using x-rays which was used to image the 3D internal structure of a eukaryotic cell at nanometre length scales and with a lower dose of radiation than had previously been possible.

Cells were mounted in the laboratory on a special finder grid which enabled them to easily locate them in the x-ray beam. The x-ray measurements were carried out in Chicago at the Advanced Photon Source, part of the Argonne National Laboratory. The lab-based sample preparation and characterisation of cells is crucial as it focuses on the development of new microscopy tools for both the life sciences and the materials sciences. Access to the state-of-the-art facilities available locally at the Melbourne Centre for Nanotechnology continues to enable the development of key breakthroughs in the rapidly developing field of x-ray imaging and analysis.

The range of applications for high-resolution, low dose, x-ray tomography is vast. Removing the need for damaging sectioning of cells and other biological samples means that the fidelity of their internal structure is maintained, providing researchers with better insight and understanding into their structure and function. This information will in turn be used to develop new medicines for example, and to gain a deeper understanding of living organisms.

Work is in progress to image the malaria parasite using this new x-ray tomography technique. Researchers hope to use this information to eventually optimise new approaches to combating this disease. The facilities at MCN are currently being used to design and fabricate new x-ray optics providing even better images of biological samples. They are also exploring new approaches to mounting and finding the samples exploiting a range of nanofabrication techniques. This work is being carried out in conjunction with experimental developments at the Australian Synchrotron which will result in a new capability for high-resolution x-ray microscopy being available within Australia.

You can read more about this project in Whole-cell phase contrast imaging at the nanoscale using Fresnel Coherent Diffractive Imaging Tomography, published in Scientific Reports.

July 2013

Researchers from the University of Melbourne and CSIRO, including Dr Tim James, Dr. Tim Davis and Associate Professor Ann Robertts, together with MCN Senior Process Engineer, Matteo Altissimo have developed nanometer sized optical anteanna based on every-day radio frequency designs. The novel designs explored are focused enhancing radiation from a single photon emitter, critical components in secure optical telecommunications systems and novel biosensing systems.

The nano-antenna structures, specifically the J-pole optical antennas, were fabricated at the MCN using the Vistec EBPG 5000 electron beam lithography (EBL) system, with very high resolution EBL resist, which enabled the 30nm minimum feature sizes to be achieved.

The ability to fabricate optical nano-structures of such high fidelity enables Australian researchers to create nano-optical devices at world-class standards. This will enable novel technologies such as high efficiency single photon sources to be developed locally which is the aim of this project, but more broadly facilitates the research into leading edge nano optical devices.

The presented J-pole presents the first step in the project to develop a high-efficiency single photon source which is critical to enhancing biological research and the security of telecommunications systems.

The team will next look at integration of the nano-antenna structures with single-photon sources such as NV centres in nano-diamond and inorganic quantum dots, which again requires the high precision and accuracy provided by the EBL tool at the MCN.

July 2013

Nanostructures fabricated with metal nanoparticles hold great potential for applications in biosensing, optical analysis, computing and solar energy conversion. One approach to creating nanoparticle-based nanostructures is to program the spontaneous self-assembly of nanoparticles into the desired architecture.

Advanced self-assembled structures can be achieved with anisotropic nanoparticles like gold nanorods. This challenging self-assembly requires not only the control over the nanoparticles position but also their orientation at the nanoscale. MCN Technology Fellow, Associate Professor Udo Bach and his team have developed a self-assembly strategy to fabricate vertical arrays of gold nanorods on patterned substrates. This illustrates the possibility to program the self-assembly of anisotropic gold nanoparticles into complex structures with a precise orientation and placement on surfaces.

The gold nanorods were synthesised based on a well-known chemical protocol while the patterned substrates fabricated through cleanroom lithographic processes. The surface treatment and geometry of the patterned substrate are designed to guide the self-assembly of gold nanorods into vertical arrays.

The experiment consists of immersing a patterned substrate into a solution of gold nanorods and letting it dry with a controlled concentration and temperature. During the solvent evaporation, the nanoparticles spontaneously self-assemble onto predefined areas into vertical arrays over the entire substrate.

The nanostructures were then characterised by Small Angle X-ray Scattering (SAXS) in collaboration with the Australian Synchrotron. The help of Dr. Stephen Mudie allowed the team to gather important information about the self-assembly method such as the nature and the range of nanoparticle ordering, and the average interparticle distance.

The most exciting breakthrough was the ability to self-assemble these vertical arrays of gold nanorods with an unprecedented control over their placement on a surface. These results show an approach to address the issue of advanced nanostructure integration in functional devices, reducing the gap between nanomaterials and nanotechnology.

The group have demonstrated that the nanostructures can be used as a chemical sensor. It was up to 36 times more sensitive than a commercial substrate. One of the first benefits would be to design and optimise these nanostructures to fabricate ultrasensative sensors for chemical and biological molecules.

Beside the development of ultrasensitive biosensors, vertical arrays of gold nanorods could be used in optics. They can guide the light at the nanoscale in a structure called a waveguide. These gold nanorod arrays have been shown in the literature to be excellent waveguides. The idea would be to make an ideal substrate to self-assemble these gold nanorod arrays and to test their optical properties as waveguides.

You can read more about this project in Self-Assembly of Vertically Aligned Gold Nanorod Arrays on Patterned Substrates, published in Angewandte Chemie.

July 2013

Many molecules in biology are chiral, meaning that they come in left-handed and right-handed forms even though they are chemically identical. Detecting these forms is important since their handedness affects how they interact. Detection is usually done with circularly polarised light, which also comes in left and right-handed forms.

A chiral optical response refers to the property of an optical material to scatter left circularly polarised light differently from right circularly polarised light. Creating a material with a strong chiral optical response is a first step towards improving the ability to detect the chirality of biological molecules.

Together with MCN, Technology Fellow, Professor Tim Davis from CSIRO has created an artificial material with a strong chiral optical response using an array of gold nanorods. The rods resonate when exposed to light, a phenomenon called surface plasmon resonance. The rods, each about 100nm long and 40nm wide, are arrayed in pairs on a glass substrate. The periodicity of the array is 250 nanometres, well below the wavelength of light. With this periodicity, the array appears as a uniform, thin film material, known as a metamaterial. Using a theory of optical resonances in gold nanorods, MCN Process Engineer, Dr. Fatima Eftekhari and Professor Tim Davis predicted an optimum chiral optical response for the metamaterial with the rod pairs oriented at 45 degrees and with the rod resonances slightly different from each other. The metamaterial was fabricated using electron beam lithography on a 30nm thick gold film on glass followed by an etching process. Optical experiments confirm that the optimum angle between the rods is 45 degrees.

The 30nm thick metamaterial shows a difference in scattering of left and right circularly polarised light of 16%, some 3000 times stronger than obtained with equivalent solutions of standard chiral materials.

The pair have shown that new optical materials can be created by designing functionality at the nanoscale. These artificial optical materials can be given properties not found in nature and have the potential for solving problems in biology and biochemistry.

The underpinning technology represents the manipulation of light – matter interactions at the nano scale. This is important for a whole range of technologies that use light, such as telecommunications, visual displays, solar energy systems and even chemical sensors. The project is currently developing optical circuits, in analogy with electrical circuits, but which are powered by light. This has the potential for exceptionally high speed data processing based on all-optical devices.

July 2013

Oil spillage, organic solvents and other industry contaminants are primary pollutants of water sources and roads around the globe. The existing conventional methods used to solve spillages are not very efficient and have their own environmental consequences. Development of new high-efficient absorption materials for the effective removal of oils, organic solvents and dyes from water is of significant, global importance for environmental and water source protection. New nanomaterials and nanotechnology can help solve this problem.

Boron Nitride (BN) nanosheets have a new two-dimensional nanostructure made of a few atomic layers. The porous nanosheets have a very high surface area of 1427 m2/g and high selective absorbent capabilities. In addition, the BN nanosheets can be re-used many times by burning the absorbed oil off. They are light weight and can float on water surface, making it easy for collection from cleaned water.

The ANFF-VIC Deakin University team led by Prof. Ying Chen is a world leader in boron nitride nanotubes and nanosheets with 20 years experience. The group synthesized porous BN nanosheets for the first time in the world and discovered excellent absorption properties on oil, dyes and solvents as common water contaminants. They also found a simple and effective regeneration prcoess of the oil-saturated nanosheets which allows the reuse of the nanosheets many times.

This is a breakthrough work in the discovery of the new nanosheet materials and the exploration of their selective oil and dye absorption properties provide an effective approach for protecting our water resource and environment.

The results published in Nature Communications have attracted strong reactions from industries around the world and they haved asked for nanosheet materials for various application tests and joint venture for future development. The group is scaling up the synthesis equipment for mass production of the materials to meet industry need, while they are also in collaboration with ANFF researchers for oil/dye absorption tests in large scale.

March 2012

One method proposed to fight multi-drug resistant bacteria is that of an intelligent delivery system which targets drugs at specific cells, minimising unwanted side effects from drug treatments. Researchers from Monash University, including MCN Technology Fellows Associate Professor Wenlong Cheng and Dr. Christina Cortez-Jugo are working on a project to develop a rational design of multi-materials composite particles for targeted, light-controllable drug delivery.

The team are looking to simulate an intelligent delivery system, whereby gold nanoparticles are incorporated with poly N-isopropylacrylamide (PNIPAM) to formulate an intelligent delivery vehicle to combat multidrug resistance.

Preliminary work suggests that gold nanoparticles could be successfully incorporated into PNIPAM particles using a rotating mixer without destroying the stimuli-responsive properties of PNIPAM. To observe this, the hydrodynamic diameters and zeta potentials of Au-PNIPAM  nanoparticles were characterised under various temperatures using the Malven Nanosizer ZS at MCN. The results suggest that at a lower critical solution temperature, PNIPAM was not altered with the incorporation of gold nanoparticles which range in size from 3.5nm to 45nm. The size of the nanoparticles was confirmed via the use of the Field Emission Gun Scanning Electron Microscope.

All instruments and equipment used to formulate and characterise the Au-PNIPAM particles were located at MCN. The facilities provided by MCN in the Biochemistry and PC2 Laboratories allowed characterisations to be carried out to a greater depth and verification of the results achieved via imaging of the formulated particles. Further studies using the intelligent delivery vehicle for delivery of vaccine and drugs are forecast using MCN’s microarray system.