Divergent Effects of Laser Irradiation on Ensembles of Nitrogen-Vacancy Centers in Bulk and Nanodiamonds: Implications for Biosensing

• DOI: 10.1186/s11671-022-03723-2
• Publication Date: 2022-09-26T05:03:37Z
• Authors: Domingo Olivares-...; Federico Gorrini; Valeria Bitonto; Johannes Ackermann; Rakshyakar Giri; Anke Krueger; Angelo Bifone
• Keywords: Nanochemistry

Ensembles of negatively charged nitrogen-vacancy centers (NV-) in diamond have been proposed for sensing magnetic fields and paramagnetic agents, as a source spin-order the hyperpolarization nuclei resonance applications. To this end, strongly fluorescent nanodiamonds (NDs) represent promising materials, with large surface areas dense ensembles NV-. However, effects tend to favor less useful neutral form, NV0 centers, strategies increase density shallow NV- proposed, including irradiation strong laser power (Gorrini ACS Appl Mater Interfaces. 13:43221-43232, 2021). Here, we study fluorescence properties optically detected (ODMR) function bulk obtained by nanomilling native material. In diamond, find that increasing increases ODMR contrast, consistent power-dependent spin-polarization. Conversely, observe non-monotonic behavior, decrease contrast at higher power. We hypothesize phenomenon may be ascribed more efficient NV-→NV0 photoconversion compared resulting depletion pool. A similar behavior is shown NDs internalized macrophage cells under typical experimental conditions imaging bioassays. Our results suggest not an effective strategy NDs, where interplay between local microenvironment determine optimal conditions.