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The localisation of fluorophores is an important aspect of determining the biological function of cellular systems. Quantum correlation microscopy (QCM) is a promising technique for providing diffraction unlimited emitter localisation that can be used with either confocal or widefield modalities. However, so far, QCM has not been applied to three dimensional localisation problems. Here we show that QCM provides diffraction-unlimited three-dimensional localisation for two emitters within a single diffraction-limited spot. By introducing a two-stage maximum likelihood estimator, our modelling shows that the localisation precision scales as $1/\sqrt{t}$ where t is the total detection time. Diffraction unlimited localisation is achieved using both intensity and photon correlation from Hanbury Brown and Twiss measurements at as few as four measurement locations. We also compare the results of (MC) simulations with the Cramér–Rao lower bound.

The nitrogen-vacancy colour centre in diamond is emerging as one of the most important solid-state quantum systems. It has applications to fields including high-precision sensing, quantum computing, single photon communication, metrology, nanoscale magnetic imaging and biosensing. For all of these applications, a high quantum yield of emitted photons is desirable. However, diamond samples engineered to have high densities of nitrogen-vacancy centres show levels of brightness varying significantly within single batches, or even within the same sample. Here we show that nearby nitrogen impurities quench emission of nitrogen-vacancy centres via non-radiative transitions, resulting in a reduced fluorescence quantum yield. We monitored the emission properties of nitrogen-vacancy centre ensembles from synthetic diamond samples with different concentrations of nitrogen impurities. All samples were irradiated with high energy electrons to create high densities of nitrogen-vacancy centres relative to the concentration of nitrogen impurities. While at low nitrogen densities of 1.81 ppm we measured a lifetime of 13.9 ns, we observed a strong reduction in lifetime with increasing nitrogen density. We measure a lifetime as low as 4.4 ns at a nitrogen density of 380 ppm. The change in lifetime matches a reduction in relative fluorescence quantum yield from 77.4% to 32% with an increase in nitrogen density from 88 ppm to 380 ppm, respectively. These results will inform the conditions required to optimise the properties of diamond crystals devices based on the fluorescence of nitrogen-vacancy centres. Furthermore, this work provides insights into the origin of inhomogeneities observed in high-density nitrogen-vacancy ensembles within diamonds and nanodiamonds.

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.

One of the key challenges 2D materials still face is their uniform wafer-scale deposition. Here, the authors present a deposition method for post-transition metal dichalcogenides, based on transformation of an ultra-thin oxide layer on the surface of liquid elemental gallium onto an oxide-coated substrate.

Here Jeskeet al. show both theoretical and experimental evidence for stimulated emission from negatively charged nitrogen vacancy centres using light in the phonon sidebands around 700 nm, demonstrating its suitability as a laser medium.

Hydrogenated detonation nanodiamonds are of great interest for emerging applications in areas from biology and medicine to lubrication. Here, we compare the two main hydrogenation techniques—annealing in hydrogen and plasma-assisted hydrogenation—for the creation of detonation nanodiamonds with a hydrogen terminated surface from the same starting material. Synchrotron-based soft X-ray spectroscopy, infrared absorption spectroscopy, and electron energy loss spectroscopy were employed to quantify diamond and non-diamond carbon contents and determine the surface chemistries of all samples. Dynamic light scattering was used to study the particles’ colloidal properties in water. For the first time, steady-state and time-resolved fluorescence spectroscopy analysis at temperatures from room temperature down to 10 K was performed to investigate the particles’ fluorescence properties. Our results show that both hydrogenation techniques produce hydrogenated detonation nanodiamonds with overall similar physico-chemical and fluorescence properties.

The probing of physiological processes in living organisms is a grand challenge that requires bespoke analytical tools. Optical fiber probes offer a minimally invasive approach to report physiological signals from specific locations inside the body. This perspective article discusses a wide range of such fiber probes developed at the Australian Research Council Centre of Excellence for Nanoscale BioPhotonics. Our fiber platforms use a range of sensing modalities, including embedded nanodiamonds for magnetometry, interferometric fiber cavities for refractive index sensing, and tailored metal coatings for surface plasmon resonance sensing. Other fiber probes exploit molecularly sensitive Raman scattering or fluorescence where optical fibers have been combined with chemical and immunosensors. Fiber imaging probes based on interferometry and computational imaging are also discussed as emerging in vivo diagnostic devices. We provide examples to illustrate how the convergence of multiple scientific disciplines generates opportunities for the fiber probes to address key challenges in real-time in vivo diagnostics. These future fiber probes will enable the asking and answering of scientific questions that were never possible before.

Nature Communications 8: Article number: 14482; published: 17 February 2017; Updated: 22 March 2017 The original version of this Article contained a typographical error in the spelling of the author Omid Kavehei, which was incorrectly given as Omid Kevehei. This has now been corrected in both the PDF and HTML versions of the Article.

Fluorescent nanodiamonds (FNDs) are extremely photostable markers and nanoscale sensors, which are increasingly used in biomedical applications. Nanoparticle size is a critical parameter in the majority of these applications. Yet, the effect of particle size on FND’s fluorescence and colloidal properties is not well understood today. Here, we investigate the fluorescence and colloidal stability of commercially available high-pressure high-temperature FNDs containing nitrogen-vacancy (NV) centers in biological media. Unconjugated FNDs in sizes ranging between 10 nm and 140 nm with an oxidized surface are studied using dynamic light scattering and fluorescence spectroscopy. We determine their colloidal stability in water, fetal bovine serum, Dulbecco’s Modified Eagle Medium and complete media. The FNDs’ relative fluorescence brightness, the NV charge-state, and the FND fluorescence against media autofluorescence are analyzed as a function of FND size. Our results will enable researchers in biology and beyond to identify the most promising FND particle size for their application. [ABSTRACT FROM AUTHOR]

Lanthanoid-doped Gallium Nitride (GaN) semiconductors are a promising class of materials with the potential to be used across a range of novel quantum optelectronic all-locations including room temperature single photon sources. However, to date there is relatively little understood about the properties of small lanthanoid ensembles, which is required before this class of materials can reach their full potential. This paper reports room temperature optical properties of submicron extent implanted-Praseodymium (Pr) in GaN. Thermal annealing at 1200 °C is conducted for the Pr implanted GaN using SiN cap technique to activate implanted-Pr as luminescent centers. The photoluminescence shows two main peaks at 650.3 and 652.0 nm originating from the 3P0 → 3F2 transition in 4f-shell of Pr3+. We explore the saturation behavior of the photoluminescence intensity. The implanted-Pr activation ratio in a 100 nm × 100 nm region is estimated to be 1.7% in the case of 532 nm excitation. [ABSTRACT FROM AUTHOR]

Abstract Diamond color centers (optically active defects) can be used for all‐optical thermometry for non‐invasive and localized temperature measurements. The visible to near‐infrared photoluminescence of these defects is greatly attenuated in optical fibres and biological samples and therefore limits their use. A color center in Si‐doped diamond with emission coinciding with the O‐band and a major biological transparency window has recently been reported. It has a zero phonon line (ZPL) at 1221 nm and well‐resolved phonon side‐band features. In this work, a strong temperature dependence above 150 K is observed, allowing for accurate temperature measurements up to approximately 420 K. The temperature can be determined via spectral shifts or thermal broadening of the ZPL and through the intensity ratio between the ZPL and the phonon side‐band to a maximum temperature resolution of 0.57 K/Hz. Thermometry using these micro‐diamonds is demonstrated for both electronic and biological applications highlighting their versatility. The potential for further enhancements in sensitivity is discussed.

Abstract Lanthanoid-doped Gallium Nitride (GaN) integrated into nanophotonic technologies is a promising candidate for room-temperature quantum photon sources for quantum technology applications. We manufactured praseodymium (Pr)-doped GaN nanopillars of varying size, and showed significantly enhanced room-temperature photon extraction efficiency compared to unstructured Pr-doped GaN. Implanted Pr ions in GaN show two main emission peaks at 650.3 nm and 651.8 nm which are attributed to 3 P 0-3 F 2 transition in the 4f-shell. The maximum observed enhancement ratio was 23.5 for 200 nm diameter circular pillars, which can be divided into the emitted photon extraction enhancement by a factor of 4.5 and the photon collection enhancement by a factor of 5.2. The enhancement mechanism is explained by the eigenmode resonance inside the nanopillar. Our study provides a pathway for Lanthanoid-doped GaN nano/micro-scale photon emitters and quantum technology applications.

Self-assembled supramolecular structures such as optical wires, films and 2D slabs offer a new generation of electronic and optical devices. In particular, self-assembled porphyrin devices, including those integrated onto silica and silicon platforms, open new opportunities in photonic applications spanning molecular biosensing, photovoltaics and telecommunications. All reports to date, however, largely highlight the potential but have not established a clear pathway to the actual implementation of more complex device prototypes. In this paper, we propose and demonstrate the use of a focused ion beam (FIB) to process and fabricate devices in porphyrin-based supramolecular structures. These self-assembled structures have an initial root mean squared (rms) values for surface roughness of <0.5 nm as measured by atomic force microscopy. Under appropriate FIB processing and cutting conditions, the rms value for surface roughness falls to <0.4 nm, comparable with some of the best optical flatnesses obtained within, for example, structured optical fibres and integrated optical waveguides. The milling rate of the porphyrin structures was estimated to be [?]70% of that of silica. The versatility of a FIB as a tool for rapid processing and fabricating 1D and 2D photonic waveguide structures within supramolecular self-assembled platforms is demonstrated by fabricating a 2D coupler, setting the groundwork for true optical device engineering and integration using these new organic systems. [ABSTRACT FROM AUTHOR]