Core-shell diamond-graphene needles with silicon-vacancy color centers

Color centers in diamond nanostructures open new horizons in biomedicine, offering a biocompatible material platform for sensing temperature, pH, and magnetic field. Covering of the color centers enriched diamonds with graphene shell can essentially extend their application potential. Specifically, under irradiation with ultrashort laser pulses, the highly absorptive graphene shell can be used for excitation of a shock acoustic wave which can be used for cancer cell destruction or drug photoactivation through the Joule heating. In this study, we present a novel method for creating diamond-graphite core-shell structures. Through precise control of the growth of the graphitic layer on Single Crystal Diamond Needles (SCDNs) via vacuum annealing at 900°C for 30 minutes, we preserved 57% of the light emission from silicon-vacancy (SiV^-) centers while maintaining their spectral peaks. Contrary to our expectations of reduced SiV^- luminescence due to the presence of the graphitic shell, we observed that the initial high brightness of SiV^- in the diamond needles persisted. This enabled us to detect SiV^- luminescence spectrally, even within the core-shell structures. Our results underscore the tunability of these structures’ properties through temperature and duration control, suggesting promising prospects for their application in advanced biomedical tools with sensing capabilities.