Category Archives: RMIT

Detonation nanodiamonds to aid bioimaging

6 February 2018:

Tiny 5 nm detonation nanodiamonds glow in different colors and their fluorescence is pH dependent, reports a new paper by CNBP scientists published today in the Nature journal Scientific Reports.

Lead author of the paper Dr Philipp Reineck from RMIT University (Former CNBP Research Fellow and current CNBP Associate Investigator) notes that the research is particulalry exciting as the fluorescence lifetime of the detonation nanodiamonds makes fluorescence lifetime imaging (FLIM) for bioimaging applications feasible.

Journal: Scientific Reports.

Publication title: Visible to near-IR fluorescence from single-digit detonation nanodiamonds: excitation wavelength and pH dependence.

Authors: Philipp Reineck, Desmond W. M. Lau, Emma R. Wilson, Nicholas Nunn, Olga A. Shenderova & Brant C. Gibson.

Abstract: Detonation nanodiamonds are of vital significance to many areas of science and technology. However, their fluorescence properties have rarely been explored for applications and remain poorly understood. We demonstrate significant fluorescence from the visible to near-infrared spectral regions from deaggregated, single-digit detonation nanodiamonds dispersed in water produced via post-synthesis oxidation. The excitation wavelength dependence of this fluorescence is analyzed in the spectral region from 400 nm to 700 nm as well as the particles’ absorption characteristics. We report a strong pH dependence of the fluorescence and compare our results to the pH dependent fluorescence of aromatic hydrocarbons. Our results significantly contribute to the current understanding of the fluorescence of carbon-based nanomaterials in general and detonation nanodiamonds in particular.

Copper oxide nanocubes good for bioimaging

Nafisa Zohora4 December 2017:

New CNBP research determines that copper oxide nanocubes are suitable for long-term bioimaging experiments. Lead author on the paper – CNBP PhD student Zafisa Zohora (RMIT University).

Journal: Scientific Reports.

Publication titleFluorescence brightness and photostability of individual copper (I) oxide nanocubes.

Authors: Nafisa Zohora, Ahmad Esmaielzadeh Kandjani, Antony Orth, Hannah M. Brown, Mark R. Hutchinson & Brant C. Gibson.

Abstract:
Conventional organic fluorophores lose their ability to fluoresce after repeated exposure to excitation light due to photobleaching. Therefore, research into emerging bright and photostable nanomaterials has become of great interest for a range of applications such as bio-imaging and tracking. Among these emerging fluorophores, metal oxide-based nanomaterials have attracted significant attention as a potential multifunctional material with photocatalytic and angeogenisis abilities in addition to fluorescnce applications. However, most of these applications are highly dependent on size, morphology, and chemo-physical properties of individual particles. In this manuscript, we present a method to study the intrinsic optical characteristics of individual copper (I) oxide (Cu2O) nanocubes. When excited at 520 nm using only 11 µW excitation power (1.7 W/cm2), individual nanocubes were observed to emit light with peak wavelengths ~760 nm which is conveniently within the near-infrared 1 (NIR1) biological window where tissue autofluorescence is minimal. Bright and photostable fluorescence was observed with intensities up to 487 K counts/s under constant illumination for at least 2 minutes with a brightness approximately four times higher than the autofluorescence from a fixed cumulus-oocyte complex. With near-IR emission, high fluorescence brightness, and outstanding photostability, Cu2O nanocubes are attractive candidates for long-term fluorescent bioimaging applications.

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.