Magnetic field imaging in biological systems with nanometric resolution

Abstract

Recent developments of engineered nitrogen-vacancy (NV) centres in diamonds offer promising avenues for the creation of sensitive nanoscale probes, pivotal for quantum measurements and diagnostic applications in nanomedicine. The aim of this work is to enable these sensor applications by studying NV photodynamics, investigating the effects of the environment and developing advanced quantum sensor chips. In this thesis, we include both fluorescent nanodiamond particles (NDs) and NV-containing single crystal diamond. Initially, we study the fundamental physics governing signal generation, exploring the photodynamics of a single NV center and analysing its spin-contrast properties. Subsequently, we probe the impact of the crystal environment on the photoelectrical signals and quantum efficiency, determining the possible origins of non-standard phenomena such as positive photocurrent detected magnetic resonance (PDMR). We demonstrate the usage of ground-state level anti-crossing (GSLAC) in photoelectrical spin-state readout. In the second part of the thesis, we focused on the development of a quantum chip for both single-crystal diamond and ND particles. Two types of prototypes were designed and fabricated, with numerical modelling employed to elucidate microwave field distribution and resonance patterns. For single crystal diamond chips, in-depth testing is conducted to mitigate microwave-induced interference, which is critical for detecting low photocurrents from single NV centres. Additionally, we explore the potential for integrating this chip into a microfluidic chamber. The chip for the nanodiamond particles was evaluated for its heating properties, which are crucial for keeping neurons alive, using theoretical calculations and experimental measurements using a nanodiamond probe. Furthermore, we also perform the in vitro sensing of the magnetic field at the attached nanodiamonds to the neuron cells. In summary, our research represents a significant step forward in harnessing the capabilities of engineered NV centers in diamond for quantum sensing applications, offering promising prospects in both fundamental research and practical diagnostics in nanomedicine.