Nitrogen-vacancy centers (NVs) are an atomic defect in diamond which possess remarkable fluorescence and spin properties which can be used for multiple metrological applications, particularly when the NV is hosted in nanodiamond, which can be easily integrated with a variety of nanoscale systems. A new class of nanodiamond hybrid nanostructures was developed using bottom-up synthesis methods. In this work, coupling between NV centers and plasmonic, excitonic and magnetic nanoparticles in these nanodiamond hybrid nanostructures is investigated using fluorescence lifetime measurements, spin relaxometry measurements and modeled using finite element method (FEM) and Monte Carlo simulations. This work not only characterizes the properties of these nanodiamond-hybrid nanostructures but also facilitates design guidelines for future hybrid structures with enhanced metrological and imaging capabilities.
Nitrogen-vacancy centers (NVs) are an atomic defect in diamond which possess remarkable fluorescence and spin properties which can be used for multiple metrological applications, particularly when the NV is hosted in nanodiamond, which can be easily integrated with a variety of nanoscale systems. A new class of nanodiamond hybrid nanostructures was developed using bottom-up synthesis methods. In this work, coupling between NV centers and plasmonic, excitonic and magnetic nanoparticles in these nanodiamond hybrid nanostructures is investigated using fluorescence lifetime measurements, spin relaxometry measurements and modeled using finite element method (FEM) and Monte Carlo simulations. This work not only characterizes the properties of these nanodiamond-hybrid nanostructures but also facilitates design guidelines for future hybrid structures with enhanced metrological and imaging capabilities.
The NV defect center in diamond forms a pseudo-atomic quantum system with discreet optically excitable transitions between ground and excited states in the gap between valence and conduction bands, making the NV center a deep-level defect center in diamond. For the negatively charged NV center (NV-), both the ground and excited states are spin triplets (S=1) and coupling between optical and spin states provides unique opportunities for optical detection of magnetic resonance (ODMR) and quantum metrology under ambient conditions. As an atomically sized point defect that is stable in single nanodiamonds as small as a few nanometers, the NV center enables spin based imaging of temperature, electric fields, magnetic fields and mechanical strain with nanoscale spatial resolution. Made of carbon, nanodiamonds are also ideal nanoparticles for use in biological systems, exhibiting extremely low cytotoxicity, no photo bleaching and exceptional contrast in transmission electron and light microscopy. With the ability to act as both a passive, non perturbing sensor (e.g. a diamagnetic material used for sensing magnetic fields) and a connection point for two way, direct coupling of far field optics to NV− spins and indirectly to the highly localized neighborhood of atoms, electronic states and phonon modes in the local vicinity, NV diamond provides a route to nanoscale field sensing and spin based optical microscopy. These sensors are also stable in nanodiamonds. For nanoparticles, the reduction in particle diameter dramatically enhances the proportion of the material that is surface exposed, enhancing any surface related properties. Nitrogen Vacancy centers in nanodiamonds provide another example of material properties that vary with particle size. In chapter 5, evidence that modulation of nanodiamonds fluorescent emissions by electrical perturbations in their surrouding environment allows transduction of local electrodynamics into a far field optical signal capable of mapping action potentials in cardiomyocytes in presented. The unifying theme for all of the work presented in this dissertation is to enable the use of magnetic resonance signals and interactions for imaging and sensing in previously inaccessible regimes. The specific focus is on methods and techniques to enable nanoscale physical sensing and functional imaging in live tissues, with the ultimate aim to lay the predicate for the combination of both without compromise.
Diamond is unique. Whether mechanical, thermal, electrical or optical, its properties are within the most extreme compared to those of any other material. This, together with the fact that in the last fifty years the synthesis of artificial diamond has become a reality, makes it very attractive for engineering and technological purposes. The range of diamond-based applications is very diverse and, among the others, includes its use in mechanical machining, high-power high-frequency electronics and high transmissivity optics. -- Diamond is also host to a wide variety of crystallographic defects. Appropriately controlled, they can be used to tune the characteristics of the material, but even more interestingly they often possess attractive optical properties on their own. In particular, nitrogen-vacancy (NV) centres in diamond have been the subject of extensive study in the last few years. They possess unique room-temperature optical and spin properties which make them promising systems for solid-state qubits in quantum information technologies and for emerging applications in biotechnology, nanomedicine and high resolution magnetometry, such as drug delivery, fluorescent biomarking and spin imaging. -- This thesis is focused on NV centres in diamond. I first present an extensive review on diamond as a material, describing in detail its physical properties, the methods that have been developed to synthesise it and some of its possible applications. I then move the attention specifically to NV centres in nanodiamonds (NDs), i.e. diamond crystals in the nanometre size range (0-100 nm). They are a potential candidate for emerging technologies including high-resolution magnetometry and biomedical imaging. For these applications, specific material requirements, such as the small size of the diamond nanocrystals and the optical stability of the hosted NV centres, are crucial. The NV stability with respect to the nanodiamond size and surface is the central theme of this thesis. I analyse the optical behaviour of NV centres in nanodiamond while varying a number of key parameters such as size, surface termination and diamond origin. Based on the measurements, I conclude whether the nanodiamond size and the NV surface proximity are factors that must be taken into consideration in order to control the material and realise nanotechnologies based on NV centres in nanodiamonds.
The nitrogen-vacancy (NV) center is a point defect in diamond and has been championed as a promising solid-state "artificial atom." NV center properties such as its bright luminescence, room-temperature optical readout of spin states, and long spin decoherence lifetime make it an excellent system for applications in quantum information processing, high sensitivity magnetometry, and biotagging. In all applications, near-surface NVs are desirable. However, it has been found that the favorable properties of the NV center are significantly diminished as the NV center nears the surface. \nThis dissertation presents efforts in understanding the effect of the surface on the luminescence of NV centers less than a wavelength of light from the surface. We use plasma assisted etching to, independently, change the surface termination and bring the NV closer to the surface. We find that treating the surface with CF4 plasma results in a deposited polymerous fluorocarbon which helps stabilize nearby NVs. We propose using a downstream etcher to bring NVs closer to the surface, while minimizing damage and maintaining NV luminescence. Finally, we enhance emission of these near-surface NVs by coupling them into a hybrid diamond plasmonic cavity. The fabricated devices result in a measured Q of 170, higher than other previously fabricated diamond plasmonic devices.
Color centers in diamond, and in particular the nitrogen-vacancy center (NV center), have proven promising for the emerging field of quantum technologies. In this thesis, new concepts for the manipulation of the NV center dynamics will be addressed, along with the proposal of novel fields of application. It comprises: (i) A study of the NV coupling to intrinsic acoustical phonons in nanocrystals, and concepts to exploit that mechanism for conditional quantum operations. (ii) The proposal for the bottom-up creation of NV arrangements on the nanoscale by the ordered arrangement of nanodiamonds directed by biological scaffold structures. A framework is developed for coherently addressing and manipulating NV centers in such structures along with studies of noise and imperfections. (iii) The interferometry with nanodiamonds in search of signatures of quantum gravity. (iv) The creation of an illustrative (filter-based) framework for the analysis and design of hybrid NV-nuclear spin couplings.
Fluorescent milled nanodiamonds are one of the most promising physical bases for quantum devices. The nitrogen vacancy (NV) center in diamond acts a room temperature, optically addressable quantum system which significantly decreases the infrastructure costs of developing quantum devices. Since nanodiamonds are nontoxic and colloidally stable, the nanoparticles are particularly attractive to the fields of sensing and nanomedicine where environmental changes must be detected with nanoscale resolution. Particle to particle irregularity, however, alters the spin and optical properties of each nanodiamond and complicates their integration into more complex systems. In this dissertation, we address the inhomogeneity of nanodiamonds and provide multiple paths towards fully utilizing these quantum emitters. First, we develop a technique for the self-assembly of nanodiamonds into arrays. We then utilize these arrays to perform a statistical study of the nanodiamonds and characterize the impact of the material’s surface and crystalline structure on the NV center’s optical and spin properties. Next, we establish a surface modification method that both improves the general properties of the nanodiamonds and enables chemical conjugation reactions. Together, these results deliver a newfound level of control and uniformity over an otherwise uncontrollable and polydisperse material.
Defect centers in diamond are regarded as a promising candidate for future solid state quantum technology. In particular the nitrogen vacancy (NV) center attracts researchers attention, as it promises to emit indistinguishable single photons and provides a triplet ground state with ultra long spin coherence times. In particular NV centers in nano diamonds are attractive, since they can be integrated into quantum photonic hybrid devices with nano manipulation techniques. We report on first demonstrations of the integration of NV-centers into photonic hybrid devices, and point out future applications. Beside the striking demonstrations of the integrability, nanodiamonds have several drawbacks. In particular the spectral diffusion of the zero-phonon line is addressed.