Emission and nonradiative decay of nanodiamond NV centers in a low refractive index environment.

The nitrogen vacancy (NV) center is the most widely studied single optical defect in diamond with great potential for applications in quantum technologies. Development of practical single-photon devices requires an understanding of the emission under a range of conditions and environments. In this work, we study the properties of a single NV center in nanodiamonds embedded in an air-like silica aerogel environment which provides a new domain for probing the emission behavior of NV centers in nanoscale environments.

A modular design of low-background bioassays based on a high-affinity molecular pair barstar:barnase.

High-affinity molecular pairs provide a convenient and flexible modular base for the design of molecular probes and protein/antigen assays. Specificity and sensitivity performance indicators of a bioassay critically depend on the dissociation constant (K(D)) of the molecular pair, with avidin:biotin being the state-of-the-art molecular pair (K(D) ∼ 1 fM) used almost universally for applications in the fields of nanotechnology and proteomics. In this paper, we present an alternative high-affinity protein pair, barstar:barnase (K(D) ∼ 10 fM), which addresses several shortfalls of the avidin:biotin system, including non-negligible background due to the non-specific binding.

Effect of the nanodiamond host on a nitrogen-vacancy color-centre emission state.

Control over the quantum states of individual luminescent nitrogen-vacancy (NV) centres in nanodiamonds (NDs) is demonstrated by careful design of the crystal host: its size, surface functional groups, and interfacing substrate. By progressive etching of the ND host, the NV centres are induced to switch from latent, through continuous, to intermittent or "blinking" emission states. The blinking mechanism of the NV centre in NDs is elucidated and a qualitative model proposed to explain this phenomenon in terms of the centre electron(s) tunnelling to acceptor site(s).

Luminescent nanodiamonds for biomedical applications.

In recent years, nanodiamonds have emerged from primarily an industrial and mechanical applications base, to potentially underpinning sophisticated new technologies in biomedical and quantum science. Nanodiamonds are relatively inexpensive, biocompatible, easy to surface functionalise and optically stable. This combination of physical properties are ideally suited to biological applications, including intracellular labelling and tracking, extracellular drug delivery and adsorptive detection of bioactive molecules.

Observation and control of blinking nitrogen-vacancy centres in discrete nanodiamonds.

Nitrogen-vacancy colour centres in diamond can undergo strong, spin-sensitive optical transitions under ambient conditions, which makes them attractive for applications in quantum optics, nanoscale magnetometry and biolabelling. Although nitrogen-vacancy centres have been observed in aggregated detonation nanodiamonds and milled nanodiamonds, they have not been observed in very small isolated nanodiamonds. Here, we report the first direct observation of nitrogen-vacancy centres in discrete 5-nm nanodiamonds at room temperature, including evidence for intermittency in the luminescence (blinking) from the nanodiamonds.