11 June 2020 – originally published by the Science Convergence Science Network
By Catriona Nguyen-Robertson
“Diamonds are forever”. This is not only true for the gemstones themselves, but also for the colouration and fluorescence that many diamonds display. Dr Philipp Reineck uses this rare property to engineering tiny diamond particles with unlimited fluorescence.
Deemed one of nature’s most precious gemstones, diamonds are exquisite. Philipp is not interested in the glamour of the diamond crystal, but rather the atomic defects within that form so-called colour centres, which also give gemstones their unique colours. He uses these to engineer nanodiamonds as bright and biocompatible fluorescent nanoparticles.
The unifying theme throughout Philipp’s research career has been unlocking the potential of small things with big impact in areas from biology to solar energy. Philipp works at the intersection of many fields, as an Associate Investigator of the Australian Research Council (ARC) Centre of Excellence for Nanoscale BioPhotonics and Vice-Chancellor’s Research Fellow at RMIT University. Understanding biology at the fundamental molecular level remains challenging, which is why Philipp believes that physicists, chemists and biologists have to work together to find answers.
Philipp’s interest in interdisciplinary research began as an undergraduate student of physics at the University of Munich. He completed a Diploma Thesis (similar to Masters’ thesis) investigating the diffusion of DNA in a temperature gradient. Even though this effect – also known as thermodiffusion – had been known for over hundred years, it has remained relatively unknown. Yet, it is vital for many processes in nature and biology and may have been an essential ingredient for the origin of life on our planet. This kickstarted Philipp’s passion for intersecting physics with biology – biophysics.
Looking to study overseas, Philipp moved to Australia to complete a PhD at Monash University. He explored the properties of metallic particles for use in solar cells. He was interested in making nanoparticles self-assemble and controlling the movement of charge and energy between them by shining light on them. While he did not plan to stay in Australia for good, he never left. He held a postdoctoral research position at Swinburne before moving to RMIT University and has now been in Australia for more than ten years.
Philipp’s current research focus is on harnessing the fluorescent properties of diamond nanoparticles and has recently been awarded an early-career research fellowship by the ARC. In collaboration with Professors Brant Gibson and Andrew Greentree at RMIT University, the Reineck research group works towards understanding and engineering nanodiamonds to develop bright and biocompatible fluorescent nanoparticles for use in biomedical research.
Diamonds have a rigid and orderly atomic structure. Tight covalent bonds between carbon atoms give diamonds their tremendous hardness. However, defects in the lattice structure of diamonds can give rise to interesting properties and fluorescent colour centres.
Philipp studies diamond nanoparticles that contain a nitrogen vacancy defect: a carbon atom is substituted with a nitrogen atom and an adjacent vacant space. This imperfection causes the fluorescence emitted by these particles. The fluorescence is also sensitive to magnetic fields, making diamond a promising magnetometer. Philipp is aiming to also use this fluorescence to detect voltages.
Neurons have a great amount of electrical activity as they send messages electrochemically: chemical signals trigger electrical ones as electrically charged ions move in and out of the cell. In neurons, electrical activity is always accompanied by an influx of calcium (Ca2+) ions, and therefore calcium imaging is used to indirectly monitor the electrical activity in neurons in cell culture or living animals. Nanodiamonds can directly measure the voltage itself and thereby potentially enable much faster real-time measurements.
Fluorescent organic dyes are commonplace in light-based imaging techniques used extensively in biology, but Philipp’s research presents an exciting opportunity to improve these techniques. Unlike organic dyes traditionally used to stain & image cells, diamond nanoparticles are photo-stable – they are not degraded by light over time due to their different origin of fluorescence. While nanodiamonds will not replace organic dyes, they provide an alternative that provide for high temporal resolution over long periods of time. Additionally, diamond nanoparticles are larger in size than organic dyes and can self-assemble into complex structures. They therefore enter into different parts of a cell: small dyes readily pass through cell membranes while nanodiamonds cannot and are instead often engulfed (endocytosed) and kept compartmentalised (in the endocytic pathway).
When he is not thinking about the colour of diamonds, Philipp leads a colourful life. Living in Melbourne’s Bayside, he often goes for a run near the beach and windsurfing. He’s also a dedicated Tennis player, red-wine enthusiast and passionate about music.
Philipp is a highly collaborative scientist and works closely with researchers from across Australia for opportunities to expand and integrate the impact of his work. Not only do the defect centres of diamonds create vibrant colours, they are also fluorescent and have unique optical properties that he tailors for many applications from quantum computing to imaging and biological sensing. His passion for his field is inspiring and his work truly embodies the concept of convergent science.