Tag Archives: Andrew Greentree

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.

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.

 

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.

Want a better camera? Just copy bees!

4 July 2017:

Check out the latest buzz about bees and their extra light-sensing eyes! CNBP CI Prof Andy Greentree is coauthor on a new paper in PNAS, which identifies how the eyes and brains of honeybees work together, to process colour information.

“If we can design technology to mimic the way bees do this, we’ll be able to create better cameras and image-processing systems for drones and robots,” say the researchers in an article on the science news channel ‘The Conversation‘.

 

Enhancement of the NV quantum yield

3 July 2017:

Researchers from CNBP’s RMIT University node (lead author CNBP PhD student Marco Capelli pictured), have had a paper published in the journal ‘Nanoscale’.

The researchers report an enhancement of the nitrogen-vacancy (NV) quantum yield by up to 7% in bulk diamond caused by an external magnetic field.

The paper is accessible online.

Journal: Nanoscale.

Publication title: Magnetic field-induced enhancement of the nitrogen-vacancy fluorescence quantum yield .

Authors: M. Capelli, P. Reineck, D. W. M. Lau, A. Orth, J. Jeske, M. W. Doherty, T. Ohshima, A. D. Greentree and B. C. Gibson.

Abstract: The nitrogen-vacancy (NV) centre in diamond is a unique optical defect that is used in many applications today and methods to enhance its fluorescence brightness are highly sought after. We observed experimentally an enhancement of the NV quantum yield by up to 7% in bulk diamond caused by an external magnetic field relative to the field-free case. This observation is rationalised phenomenologically in terms of a magnetic field dependence of the NV excited state triplet-to-singlet transition rate. The theoretical model is in good qualitative agreement with the experimental results at low excitation intensities. Our results significantly contribute to our fundamental understanding of the photophysical properties of the NV defect in diamond.

New paper in ‘Nanoscale’

Low Res Edit 01065 December 2016:

A new publication from CNBP researchers (lead author Philipp Reineck pictured) demonstrates bright and photostable fluorescence from nitrogen-vacancy centers in unprocessed nanodiamond particle aggregates. The work has just been reported in the journal ‘Nanoscale’ and is accessible online.

Journal: Nanoscale.

Title: Bright and photostable nitrogen-vacancy fluorescence from unprocessed detonation nanodiamond.

Authors: P. Reineck, M. Capelli, D. W. M. Lau, J. Jeske, M. R. Field, T. Ohshim, A. D. Greentree and B. C. Gibson.

Abstract: Bright and photostable fluorescence from nitrogen-vacancy (NV) centers is demonstrated in unprocessed detonation nanodiamond particle aggregates. The optical properties of these particles is analyzed using confocal fluorescence microscopy and spectroscopy, time resolved fluorescence decay measurements, and optically detected magnetic resonance experiments. Two particle populations with distinct optical properties are identified and compared to high-pressure high-temperature (HPHT) fluorescent
nanodiamonds. We find that the brightness of one detonation nanodiamond particle population is on the same order as that of highly processed fluorescent 100 nm HPHT nanodiamonds. Our results may open the path to a simple and up-scalable route for
the production of fluorescent NV nanodiamonds for use in bioimaging applications.

Education session at Olympus Australia

Andy-Greentree-at-Olympus26 August 2016:

Olympus LIVE hosted a workshop today, involving a group of Quantum Physics researchers and  students from RMIT University and the ARC Centre of Excellence for Nanoscale BioPhotonics (CNBP).

It was the first microscopy workshop of its kind involving Olympus, the University and Centre, giving students valuable exposure and hands-on experience with resident Olympus microscopy experts.

The initial planning for the event was coordinated by CNBP Chief Investigator Prof Andrew Greentree from RMIT University (pictured top left) and CNBP industry partner Mr Jian Shen from Olympus Australia. The day consisted of a training/education session that was part of the ‘Masters in Nanotechnology and Smart Materials’ course, which is in its first year at RMIT University.

The event was hosted by Olympus at their state of the art new facility at Notting Hill, Melbourne and included a theory session, hands on training on microscopes run by Olympus experts, and a tour of some of the facilities.

It is planned that this will become an annual event as part of the ‘Masters in Nanotechnology and Smart Materials’ course at RMIT.

Said Prof Greentree, “This is just another way that the Olympus/CNBP partnership is providing benefits above and beyond that of direct research.”

 

Inaugural Professorial Lecture by CI Greentree

Andy-Greentree_web19 August 2016:

CNBP Chief Investigator Andrew Greentree presented to a full-house at RMIT University during his Inaugural Professorial Lecture on Friday evening, August 19th, 2016.

Over 150 colleagues, friends, family and members of the public were in attendance to hear about Andy’s innovative research, and to better understand the exciting potential of quantum technology and its many applications.

The inspiring 60 minute talk included live light-based demonstrations and a Q&A session with the audience giving Andy a heartfelt ovation as proceedings concluded. Informal feedback from guests as they departed was that the talk had been inspiring, educational and thoroughly enjoyable in nature!

Below – images from the event.

Andy-Professorial (1)

Andy-Professorial2

CNBP visits Belmont High School

Outreach-1ab13 November 2015:

CNBP researchers Andy Greentree, Denitza Denkova and Lindsay Parker took their science to the students on Friday Nov 13th, visiting Belmont High School for a fun filled day of outreach, incorporating science demonstrations, talks, informal discussion and chat.

First up was a 75 minute stage show in front of approximately 80 students from Years 8 and Year 9. Light as a concept was first explained, its wave and particle nature providing the basis for the session. A leaf-blower, table tennis balls, lasers, strobe lights and running water were also used, demonstrating the nature of light and its reflective, refractive and diffractive properties.

Nanodiamonds, iPhones, invisibility cloaks and glow sticks also made an appearance with the challenges and opportunities of looking deeply into the body and CNBP’s research mission clearly outlined.

This was followed by morning tea with the teaching staff and then a further talk and Q&A session with the school’s Year 12 chemistry class.

Thank you to all the students and teachers involved on the day. Great fun and extremely rewarding!