Category Archives: RMIT

A new heuristic search strategy to accelerate imaging

7 November 2017:

CNBP researchers Dr Daniel Drumm (lead author pictured) and Prof Andrew Greentree, both at RMIT University, have analysed microscopy in the contexts of Rényi-Ulam games and half-lies, developing a new family of heuristics. Their research is reported in the journal ‘Scientific Reports.’

Journal: Scientific Reports.

Publication titleMicroscopy as a statistical, Rényi-Ulam, half-lie game: a new heuristic search strategy to accelerate imaging.

Authors: Daniel W. Drumm & Andrew D. Greentree.

Abstract: Finding a fluorescent target in a biological environment is a common and pressing microscopy problem. This task is formally analogous to the canonical search problem. In ideal (noise-free, truthful) search problems, the well-known binary search is optimal. The case of half-lies, where one of two responses to a search query may be deceptive, introduces a richer, Rényi-Ulam problem and is particularly relevant to practical microscopy. We analyse microscopy in the contexts of Rényi-Ulam games and half-lies, developing a new family of heuristics. We show the cost of insisting on verification by positive result in search algorithms; for the zero-half-lie case bisectioning with verification incurs a 50% penalty in the average number of queries required. The optimal partitioning of search spaces directly following verification in the presence of random half-lies is determined. Trisectioning with verification is shown to be the most efficient heuristic of the family in a majority of cases.

Surface chemistry and nanodiamond fluorescence

31 October 2017:

Surface chemistry is vital for nanodiamond fluorescence, reports a new paper published by CNBP researchers (lead author Dr Philipp Reineck pictured). The paper was published in the journal ‘ACS Nano’ and is available online.

Journal: ACS Nano.

Publication title: Effect of Surface Chemistry on the Fluorescence of Detonation Nanodiamonds.

Authors: Philipp Reineck, Desmond W. M. Lau, Emma R. Wilson, Kate Fox, Matthew R. Field, Cholaphan Deeleepojananan, Vadym N. Mochalin, and Brant C. Gibson.

Abstract: Detonation nanodiamonds (DNDs) have unique physical and chemical properties that make them invaluable in many applications. However, DNDs are generally assumed to show weak fluorescence, if any, unless chemically modified with organic molecules. We demonstrate that detonation nanodiamonds exhibit significant and excitation-wavelength-dependent fluorescence from the visible to the near-infrared spectral region above 800 nm, even without the engraftment of organic molecules to their surfaces. We show that this fluorescence depends on the surface functionality of the DND particles. The investigated functionalized DNDs, produced from the same purified DND as well as the as-received polyfunctional starting material, are hydrogen, hydroxyl, carboxyl, ethylenediamine, and octadecylamine-terminated. All DNDs are investigated in solution and on a silicon wafer substrate and compared to fluorescent high-pressure high-temperature nanodiamonds. The brightest fluorescence is observed from octadecylamine-functionalized particles and is more than 100 times brighter than the least fluorescent particles, carboxylated DNDs. The majority of photons emitted by all particle types likely originates from non-diamond carbon. However, we locally find bright and photostable fluorescence from nitrogen-vacancy centers in diamond in hydrogenated, hydroxylated, and carboxylated detonation nanodiamonds. Our results contribute to understanding the effects of surface chemistry on the fluorescence of DNDs and enable the exploration of the fluorescent properties of DNDs for applications in theranostics as nontoxic fluorescent labels, sensors, nanoscale tracers, and many others where chemically stable and brightly fluorescent nanoparticles with tailorable surface chemistry are needed.

CI joins ARC College of Experts

27 October 2017:

Professor Andrew Greentree, CNBP Chief Investigator from RMIT University has been announced as a member of the prestigious ARC College of Experts.

Members of the College of Experts assess and rank ARC grant applications submitted under the National Competitive Grants Program, make funding recommendations to the ARC and provide strategic advice to the ARC on emerging disciplines and cross-disciplinary developments.

Membership of the College is limited to experts of international standing drawn from the Australian research community.

Further information on this key ARC committee and its contribution to national innovation is available online.

 

Ecolinc STEM program

16 October 2017:

Centre Associate Investigator, Dr Kate Fox from RMIT University has participated in the Ecolinc STEM for Women program in Melbourne, Oct 16th, 2017.

Ninety students (Years 9 and 10) attended the event where they  got to learn of the experiences from a range of women who work in a variety of STEM related areas. They also heard from education providers about potential career pathways in STEM and listened to the career journeys of successful women in science.

The students were from Upper Yarra, St Albans, Dandenong, Southern Cross Grammar, Bacchus Marsh, Overnewton College, Highview College, Bellarine and Whittlesea.

 

Nano ‘terminator style’ antennae

12 October 2017:

The liquid metal, shape-shifting T-1000 Terminator cyborg, featuring in a 1991 science-fiction film Terminator 2, was made possible due to breakthroughs in computer-generated imagery.

Some 25 years later, using breakthroughs in physics and chemistry CNBP scientists Dr Ivan Maksymov and Prof Andy Greentree at RMIT University have shown reconfigurable liquid-metal optical nanoantennae.

“An optical nanoantenna operates similarly to a conventional radio-frequency antenna, but its size is millions of times smaller” explains Dr Ivan Maksymov, “so it can receive and emit light similar to how a mobile phone antenna receives and emits radio waves.”

“The shape and length of the metal components that form a radio-frequency antenna determine its major properties such as operating frequency and radiation pattern,” explains Prof Andy Greentree, “so a liquid metal that can change its shape by applying voltage allows for changing antenna properties, which otherwise is difficult to achieve with fixed metal parts.”

“However, reconfigurability of optical nanoantennae is even more difficult to achieve than in radio-frequency antennae, because of their small size and lack of technologies enabling us to apply voltage to nanoscale sized objects. Therefore, we proposed a new solution – reconfiguration of liquid-metal nanoparticles using ultrasound.”

Continued Dr Maksymov, “A liquid-metal nanoparticle can change its shape due to capillary oscillations, which can be seen by everybody when observing water drops falling from a leaking kitchen tap. Drops change their shape when they detach from the tap and fall into the sink. In our work, we use ultrasound to change the shape of liquid-metal nanodroplets, which changes the nanoantenna’s operating frequency.”

“But fundamental physics remains the same as in the case of water drops.”

The paper ‘Dynamically reconfigurable plasmon resonances enabled by capillary oscillations of liquid-metal nanodroplets’ is accessible online.

CNBP at AstroLight Festival

23 September 2017:

CNBP scientists joined forces with astronauts, astronomers, scientists, stargazers and artists to present a night starring astronomy and light at the annual AstroLight Festival, held at Scienceworks in Melbourne, Saturday 23 September, 2017.

The public event, which attracted more than 1,500 attendees, saw eleven CNBP team members involved – giving talks, undertaking light-focused science demonstrations and hosting an interactive stall.

Specific talks included:

  • Science Fiction Science Fact – Laser Combat in Movies  from A/Prof Brant Gibson, CNBP node leader at RMIT
  • The Spark of Life – Dr Hannah Brown, CNBP Fellow from the University of Adelaide
  • Fluorescent Proteins – From Nature to the Lab from CNBP PhD student  Emma Wilson

Event feedback from A/Prof Gibson was extremely positive. “There was plenty of interest in our light-based CNBP science and some great questions from the public both young and old. The team really pulled together to make our participation such a success – both on the night and in the lead up activity, and with the development of the displays and demonstrations.”

Below – The CNBP team ready to do outreach!

Exploring small-sized nanoflakes

29 August 2017:

Size-dependent structural and electronic properties of MoSmonolayer nanoflakes, of sizes up to 2nm, have been investigated by CNBP researchers using density-functional theory (DFT). The paper, published in Scientific Reports is accessible online.

Journal: Scientific Reports.

Publication title: A study of size-dependent properties of MoSmonolayer nanoflakes using density-functional theory.

Authors: M. Javaid (pictured), Daniel W. Drumm, Salvy P. Russo & Andrew D. Greentree.

Abstract: Novel physical phenomena emerge in ultra-small sized nanomaterials. We study the limiting small-size-dependent properties of MoS2 monolayer rhombic nanoflakes using density-functional theory on structures of size up to Mo35S70 (1.74 nm). We investigate the structural and electronic properties as functions of the lateral size of the nanoflakes, finding zigzag is the most stable edge configuration, and that increasing size is accompanied by greater stability. We also investigate passivation of the structures to explore realistic settings, finding increased HOMO-LUMO gaps and energetic stability. Understanding the size-dependent properties will inform efforts to engineer electronic structures at the nano-scale.

Nano-diamond arrays on glass

23 August 2017:

Researchers from CNBP’s RMIT University node (lead author Ashleigh Heffernan), have published a paper demonstrating a directed self-assembly method to position nanodiamonds on glass. The method, allowing for the statistical quantification of fluorescent nanoparticles provides a step towards fabrication of hybrid photonic devices for applications from quantum cryptography to sensing.

The paper is accessible online.

Journal: Scientific Reports.

Publication title: Nanodiamond arrays on glass for quantification and fluorescence characterisation.

Authors: Ashleigh H. Heffernan, Andrew D. Greentree & Brant C. Gibson.

Abstract: Quantifying the variation in emission properties of fluorescent nanodiamonds is important for developing their wide-ranging applicability. Directed self-assembly techniques show promise for positioning nanodiamonds precisely enabling such quantification. Here we show an approach for depositing nanodiamonds in pre-determined arrays which are used to gather statistical information about fluorescent lifetimes. The arrays were created via a layer of photoresist patterned with grids of apertures using electron beam lithography and then drop-cast with nanodiamonds. Electron microscopy revealed a 90% average deposition yield across 3,376 populated array sites, with an average of 20 nanodiamonds per site. Confocal microscopy, optimised for nitrogen vacancy fluorescence collection, revealed a broad distribution of fluorescent lifetimes in agreement with literature. This method for statistically quantifying fluorescent nanoparticles provides a step towards fabrication of hybrid photonic devices for applications from quantum cryptography to sensing.

Low-power nonlinear photonic effects

15 August 2017:

Dr Ivan Maksymov from CNBP’s RMIT University node, visited the Department of Physics and Astronomy at Macquarie University Aug 15, 2017 and gave a well attended seminar.

The talk centred on the theory  of low-power nonlinear photonic effects and was formally titled, “Nonlinear optics with low-power light: Transduction of acoustic nonlinearities into the optical domain.”