46 research outputs found
Ultrasmall Nanodiamonds: Perspectives and Questions
Nanodiamonds are at the heart of a plethora of emerging applications in areas ranging from nanocomposites and tribology to nanomedicine and quantum sensing. The development of alternative synthesis methods, a better understanding, and the availability of ultrasmall nanodiamonds of less than 3 nm size with a precisely engineered composition, including the particle surface and atomic defects in the diamond crystal lattice, would mark a leap forward for many existing and future applications. Yet today, we are unable to accurately control nanodiamond composition at the atomic scale, nor can we reliably create and isolate particles in this size range. In this perspective, we discuss recent advances, challenges, and opportunities in the synthesis, characterization, and application of ultrasmall nanodiamonds. We particularly focus on the advantages of bottom-up synthesis of these particles and critically assess the physicochemical properties of ultrasmall nanodiamonds, which significantly differ from those of larger particles and bulk diamond
Detection of paramagnetic spins with an ultrathin van der Waals quantum sensor
Detecting magnetic noise from small quantities of paramagnetic spins is a
powerful capability for chemical, biochemical, and medical analysis. Quantum
sensors based on optically addressable spin defects in bulk semiconductors are
typically employed for such purposes, but the 3D crystal structure of the
sensor inhibits the sensitivity by limiting the proximity of the defects to the
target spins. Here we demonstrate the detection of paramagnetic spins using
spin defects hosted in hexagonal boron nitride (hBN), a van der Waals material
which can be exfoliated into the 2D regime. We first create negatively charged
boron vacancy (V) defects in a powder of ultrathin hBN nanoflakes
(~atomic monolayers thick on average) and measure the longitudinal spin
relaxation time () of this system. We then decorate the dry hBN nanopowder
with paramagnetic Gd ions and observe a clear quenching, under
ambient conditions, consistent with the added magnetic noise. Finally, we
demonstrate the possibility of performing spin measurements including
relaxometry using solution-suspended hBN nanopowder. Our results highlight the
potential and versatility of the hBN quantum sensor for a range of sensing
applications, and pave the way towards the realisation of a truly 2D,
ultrasensitive quantum sensor.Comment: 19 pages, 11 figure
The effect of discrete wavelengths of visible light on the developing murine embryo
Open Access funding enabled and organized by CAUL and its Member Institutions KRD is supported by a Mid-Career Fellowship from the Hospital Research Foundation (C-MCF-58–2019). KD is supported by funding from the UK Engineering and Physical Sciences Research Council (EP/P030017/1) and the Australian Research Council (FL210100099). CC acknowledges the support of a PhD scholarship jointly from the University of Adelaide and University of Nottingham. This study was funded by the Australian Research Council Centre of Excellence for Nanoscale BioPhotonics (CE140100003). PR acknowledges funding through the RMIT Vice-Chancellor’s Research Fellowship and ARC DECRA Fellowship scheme (DE200100279).Purpose A current focus of the IVF field is non-invasive imaging of the embryo to quantify developmental potential. Such approaches use varying wavelengths to gain maximum biological information. The impact of irradiating the developing embryo with discrete wavelengths of light is not fully understood. Here, we assess the impact of a range of wavelengths on the developing embryo. Methods Murine preimplantation embryos were exposed daily to wavelengths within the blue, green, yellow, and red spectral bands and compared to an unexposed control group. Development to blastocyst, DNA damage, and cell number/allocation to blastocyst cell lineages were assessed. For the longer wavelengths (yellow and red), pregnancy/fetal outcomes and the abundance of intracellular lipid were investigated. Results Significantly fewer embryos developed to the blastocyst stage when exposed to the yellow wavelength. Elevated DNA damage was observed within embryos exposed to blue, green, or red wavelengths. There was no effect on blastocyst cell number/lineage allocation for all wavelengths except red, where there was a significant decrease in total cell number. Pregnancy rate was significantly reduced when embryos were irradiated with the red wavelength. Weight at weaning was significantly higher when embryos were exposed to yellow or red wavelengths. Lipid abundance was significantly elevated following exposure to the yellow wavelength. Conclusion Our results demonstrate that the impact of light is wavelength-specific, with longer wavelengths also impacting the embryo. We also show that effects are energy-dependent. This data shows that damage is multifaceted and developmental rate alone may not fully reflect the impact of light exposure.Publisher PDFPeer reviewe
Multi-species optically addressable spin defects in a van der Waals material
Optically addressable spin defects hosted in two-dimensional van der Waals
materials represent a new frontier for quantum technologies, promising to lead
to a new class of ultrathin quantum sensors and simulators. Recently, hexagonal
boron nitride (hBN) has been shown to host several types of optically
addressable spin defects, thus offering a unique opportunity to simultaneously
address and utilise various spin species in a single material. Here we
demonstrate an interplay between two separate spin species within a single hBN
crystal, namely boron vacancy defects and visible emitter spins. We
unambiguously prove that the visible emitters are spins and
further demonstrate room temperature coherent control and optical readout of
both spin species. Importantly, by tuning the two spin species into resonance
with each other, we observe cross-relaxation indicating strong inter-species
dipolar coupling. We then demonstrate magnetic imaging using the
defects, both under ambient and cryogenic conditions, and
leverage their lack of intrinsic quantization axis to determine the anisotropic
magnetic susceptibility of a test sample. Our results establish hBN as a
versatile platform for quantum technologies in a van der Waals host at room
temperature
Oxygen-deficient photostable Cu2O for enhanced visible light photocatalytic activity
Oxygen vacancies in inorganic semiconductors play an important role in reducing electron-hole recombination, which may have important implications in photocatalysis. Cuprous oxide (Cu2O), a visible light active p-type semiconductor, is a promising photocatalyst. However, the synthesis of photostable Cu2O enriched with oxygen defects remains a challenge. We report a simple method for the gram-scale synthesis of highly photostable Cu2O nanoparticles by the hydrolysis of a Cu(i)-triethylamine [Cu(i)-TEA] complex at low temperature. The oxygen vacancies in these Cu2O nanoparticles led to a significant increase in the lifetimes of photogenerated charge carriers upon excitation with visible light. This, in combination with a suitable energy band structure, allowed Cu2O nanoparticles to exhibit outstanding photoactivity in visible light through the generation of electron-mediated hydroxyl (OH) radicals. This study highlights the significance of oxygen defects in enhancing the photocatalytic performance of promising semiconductor photocatalysts.V. B. thanks the Australian Research Council (ARC) for a
Future Fellowship (FT140101285) and funding support
through an ARC Discovery (DP170103477). ARC is also
acknowledged for DECRA Fellowships to E. D. G.
(DE170100164) and J. v. E. (DE150100427) and a Future
Fellowship to N. C. (FT1401000834). M. S. acknowledges RMIT
University for an Australian Postgraduate Award (APA). A. E. K.,
E. D. G., P. R. and R. R. acknowledge RMIT University for Vice
Chancellor Fellowships. V. B. recognizes the generous support
of the Ian Potter Foundation toward establishing an Ian Potter
NanoBioSensing Facility at RMIT University. The authors
acknowledge the support from the RMIT Microscopy and
Microanalysis Facility (RMMF) for technical assistance and
providing access to characterization facilities. This work was
also supported by the ARC Centre of Excellence for Nanoscale
BioPhotonics (CE140100003)
Stimulated emission from nitrogen-vacancy centres in diamond
Stimulated emission is the process fundamental to laser operation, thereby producing coherent photon output. Despite negatively charged nitrogen-vacancy (NV-) centres being discussed as a potential laser medium since the 1980s, there have been no definitive observations of stimulated emission from ensembles of NV-to date. Here we show both theoretical and experimental evidence for stimulated emission from NV-using light in the phonon sidebands around 700 nm. Furthermore, we show the transition from stimulated emission to photoionization as the stimulating laser wavelength is reduced from 700 to 620 nm. While lasing at the zero-phonon line is suppressed by ionization, our results open the possibility of diamond lasers based on NV-centres, tuneable over the phonon sideband. This broadens the applications of NV-magnetometers from single centre nanoscale sensors to a new generation of ultra-precise ensemble laser sensors, which exploit the contrast and signal amplification of a lasing system.This work was supported by the Australian Research Council under the
Discovery (ARC DP130104381), LIEF (LE140100131), Centres of Excellence
(CE110001013 and CE140100003) and Future Fellowship (FT110100225) schemes