Hexagonal boron nitride (h-BN) is an attractive van der Waals material for studying fluorescent defects due to its large bandgap. In this work, we demonstrate enhanced pink color due to neutron irradiation and perform electron paramagnetic resonance (EPR) measurements. The new point defects are tentatively assigned to doubly-occupied nitrogen vacancies with (S = 1) and a zero-field splitting (D = 1.2 GHz). These defects are associated with a broad visible optical absorption band and near infrared photoluminescence band centered at ~ 490 nm and 820 nm, respectively. The EPR signal intensities are strongly affected by thermal treatments in temperature range between 600 to 800ºC, where also the irradiation-induced pink color is lost. Our results are important for understanding of point defects in h-BN and their deployment for quantum and integrated photonic applications.

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Currently, nanostructured compounds have been standing out for their optical, mechanical, and chemical features and for the possibilities of manipulation and regulation of complex biological processes. One of these compounds is boron nitride nanotubes (BNNTs), which are a nanostructured material analog to carbon nanotubes, but formed of nitrogen and boron atoms. BNNTs present high thermal stability along with high chemical inertia. Among biological applications, its biocompatibility, cellular uptake, and functionalization potential can be highlighted, in addition to its eased utilization due to its nanometric size and tumor cell internalization. When it comes to new forms of therapy, we can draw attention to boron neutron capture therapy (BNCT), an experimental radiotherapy characterized by a boron-10 isotope carrier inside the target and a thermal neutron beam focused on it. The activation of the boron-10 atom by a neutron generates a lithium atom, a gamma ray, and an alpha particle, which can be used to destroy tumor tissues. The aim of this work was to use BNNTs as a boron-10 carrier for BNCT and to demonstrate its potential. The nanomaterial was characterized through XRD, FTIR, and SEM. The WST-8 assay was performed to confirm the cell viability of BNNTs. The cells treated with BNNTs were irradiated with the neutron beam of a Triga reactor, and the apoptosis caused by the activation of the BNNTs was measured with a calcein AM/propidium iodide test. The results demonstrate that this nanomaterial is a promising candidate for cancer therapy through BNCT.

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