Tag Archives: Andrew Greentree

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.

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.

The palette of the mind

12 July 2017:

Around fifty high performing Year 10 to Year 12 students from Australia and New Zealand came to RMIT on the 11th of July to listen to CNBP Chief Investigator Prof Andy Greentree present  a talk titled “Colour: the palette of the mind.”

The talk was a part of the Youth ANZAAS visit to RMIT University. Youth ANZAAS 2017 is organised by the Australian and New Zealand Association for the Advancement of Science and the Royal Society of New Zealand. It is is an annual residential international forum for science students still at school.

An abstract of Prof Greentree’s talk follows:

Colour is a complicated phenomenon! For most of us, most of the information we receive about the world comes from light, and that light is encoded by colour. This talk will explore colour. From the physics of light, to how we detect colour information, to the psychophysics of how our brain understands those signals to make sense of the world.

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 Diamond and Nano Carbons conference

1 June 2017:

CNBP was well represented at the 11th International Conference on New Diamond and Nano Carbons, held in Cairns, Australia, 28th May – June 1, 2017.

CNBP Chief Investigator A/Prof Brant Gibson was Co-chair of the conference (pictured) with CNBP researcher Dr Philipp Reineck a contributing speaker, presenting on ‘Bright and photostable nitrogen‐vacancy fluorescence from unprocessed detonation nanodiamonds’.

Also providing a contributing talk was CNBP’s Dr Lindsay Parker, ‘Applications of fluorescent nanodiamonds in cellular molecular tracing.’

Additionally,  CNBP’s Andrew Greentree, Ivan Maksymov, Daniel Drumm, Ashleigh Heffernan, Marco Capelli, Nicole Cordina and Emma Wilson gave poster presentations and Brooke Bacon and Desmond Lau provided administrative and technical support respectively.

The conference spanned research topics from fundamental physical and chemical concepts to applied technologically driven applications with carbon based materials. This including single crystal diamond, nanodiamonds, carbon nanotubes, graphene and other carbon nanostructures.

Synthesis of optical spectra

3 April 2017:

A new publication from CNBP researchers (lead author Dr Ivan Maksymov pictured)  demonstrates a new scheme for synthesis of optical spectra from nonlinear ultrasound harmonics using a hybrid liquid-state and nanoplasmonic device compatible with fibre-optic technology.

The work has just been reported in the journal ‘Optics Express’ and is accessible online.

Journal: Optics Express.

Title: Synthesis of discrete phase-coherent optical spectra from nonlinear ultrasound.

Authors: Ivan S. Maksymov and Andrew D. Greentree.

Abstract: Nonlinear acoustic interactions in liquids are effectively stronger than nonlinear optical interactions in solids. Thus, harnessing these interactions will offer new possibilities in the design of ultra-compact nonlinear photonic devices. We theoretically demonstrate a new scheme for synthesis of optical spectra from nonlinear ultrasound harmonics using a hybrid liquid-state and nanoplasmonic device compatible with fibre-optic technology. The synthesised spectra consist of a set of equally spaced optical Brillouin light scattering modes having a well-defined phase relationship between each other. We suggest that these spectra may be employed as optical frequency combs whose spectral composition may be tuned by controlling the nonlinear acoustic interactions.

Bubbles can detect sound, with light

13 March 2017:

CNBP scientists Dr Ivan Maksymov and Prof Andy Greentree at RMIT University have shown bubbles can detect sound with light in their latest publication in the area of photo-acoustics.

“Bubbles can be a boon for detecting the kind of ultrasound used in medicine as air is less dense than water” explains Dr Ivan Maksymov, “so ultrasound can squeeze a bubble more than the water surrounding it”.

To detect the change in size, Ivan showed that the bubbles could change the amount of light that passed through a gold membrane with nanosized holes in it. “It’s incredible work, I’m really excited by how Ivan has brought together these different kinds of Physics to create something quite new”, said the study’s co-author Prof Andy Greentree.

To detect the effects of sound on the bubble, on light, Ivan had to develop new computational models. The team say that their work may be useful in the development of an optical hydrophone for detecting ultrasound inside the body. “It will give us a new and potentially more sensitive way to ‘see’ with sound” says Ivan.

The work was published in the journal Physical Review A on 13th March 2017 and was funded by the Australian Research Council Centre of Excellence for Nanoscale BioPhotonics.

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.