Monodisperse Five-Nanometer-Sized Detonation Nanodiamonds Enriched in Nitrogen-Vacancy Centers
At a Glance
Section titled āAt a Glanceā| Metadata | Details |
|---|---|
| Publication Date | 2019-05-29 |
| Journal | ACS Nano |
| Authors | Daiki Terada, Takuya F. Segawa, Alexander I. Shames, Shinobu Onoda, Takeshi Ohshima |
| Institutions | Shinshu University, ETH Zurich |
| Citations | 57 |
Abstract
Section titled āAbstractāNanodiamonds containing negatively charged nitrogen-vacancy (NV<sup>-</sup>) centers are versatile nanosensors thanks to their optical and spin properties. While currently most fluorescent nanodiamonds in use have at least a size of a few tens of nanometers, the challenge lies in engineering the smallest nanodiamonds containing a single NV<sup>-</sup> defect. Such a tiny nanocrystal with a single NV<sup>-</sup> center is an āoptical spin labelā for biomolecules, which can be detected in a fluorescence microscope. In this paper, we address two key issues toward this goal using detonation nanodiamonds (DNDs) of 4-5 nm in size. The DND samples are treated first with electron irradiation to create more vacancies. With the aid of electron paramagnetic resonance (EPR) spectroscopy, we confirm a steady increase of negatively charged NV<sup>-</sup> centers with higher fluence. This leads to a 4 times higher concentration in NV<sup>-</sup> defects after irradiation with 2 MeV electrons at a fluence of 5 Ć 10<sup>18</sup> e<sup>-</sup>/cm<sup>2</sup>. Interestingly, we observe that the annealing of DND does not increase the number of NV<sup>-</sup> centers, which is in contrast to bulk diamond and larger nanodiamonds. Since DNDs are strongly aggregated after the irradiation process, we apply a boiling acid treatment as a second step to fabricate monodisperse DNDs enriched in NV<sup>-</sup> centers. These are two important steps toward āoptical spin labelsā having a single-digit nanometer range size that could be used for bioimaging and nanosensing.