Luminescent nanodiamonds: solution for precise molecular detection

Abstract

Quantum sensing is anticipated to bring a ground-breaking understanding of life cycle processes thanks to high sensitivity, specificity and resolution. One of the possible quantum sensing platforms are nanodiamond particles (NDs) containing nitrogen-vacancy (NV) centres ' defects in the diamond lattice that are extremely sensitive to surrounding magnetic fields. Here we aim to establish a quantum sensing detection method based on NV spin relaxation time (T1) readout from NDs using optically detected magnetic resonance (ODMR). This will enable future detection of reactive oxygen species (ROS) using NDs covered with superoxide-specific spin-traps, where the sensing principle is based on the variation of the T1 upon ROS attachment. For the establishment of pulsed-ODMR measurements, single-crystal diamond and NDs of 5-60 nm in size containing NV centres are used. The measurements are performed with a home-built confocal microscope modified to enable pulsed experiments. NV spin transitions are induced with microwaves (MW) applied to the sample either by wire or by MW antenna. The MW pi-pulse is determined from Rabi measurements. For the relaxometry we use a laser pulse (NV initialization and readout) followed by a microwave pi-pulse (NV spin excitation). The T1 values are obtained from data fitting