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Homoepitaxial single crystal diamond layers with bright photoluminescence (PL) of silicon-vacancy (SiV) color centers at 738 nm wavelength have been grown on (100) diamond substrates by a microwave plasma CVD using a controlled Si doping via adding silane to CH 4 -H 2 reaction gas mixture in the course of the deposition process. In the range of the silane concentrations SiH 4 /CH 4 explored, from 0 to 2.4%, the SiV PL intensity shows a nonmonotonic behavior with silane addition, with a maximum at 0.6%SiH 4 /CH 4 , and a rapid PL quenching at higher Si doping. The maximum SiV concentration of %450 ppb in the samples has been determined from optical absorption spectra. It is found that the SiV PL intensity can strongly, an order of magnitude, increase within non-epitaxial inclusions in single crystal diamond film.

A multifunctional core-shell nanocomposite platform consisting of a photoluminescent nanodiamond (ND) core with uniform porous silica coatings is presented. This design intended for drug delivery applications allows simultaneous stable fluorescent imaging with high loading capacity of bioactive molecules. Despite irregularly shaped starting cores, well-dispersed and uniformly shaped nanocomposite particles can be produced. Moreover, after optimization of the silica source-to-diamond ratio, the thickness of the porous layer can be tuned by adjusting the ethanol amount, allowing rational nanoparticle size control. The ND key property, photoluminescence, is not quenched regardless of coating with thick silica layers. The high loading capacity for incorporation of active agents, provided by the introduced porous layer, is demonstrated by adsorption of a hydrophobic model drug to the composite particles. The loading degree, as compared to a pure ND, increased by two orders of magnitude from 1 wt% for the ND to >100 wt% for the composite particles. Combining these two material classes, which both have well-documented excellent performance especially in biomedical applications, for the NDs with emphasis, but not exclusively, on imaging and mesoporous silica (MSN) on drug delivery, the advantages of both are shown here to be synergistically integrated into one multifunctional nanocomposite platform.

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Silicon-vacancy (SiV–) color center in diamond is of high interest for applications in nanophotonics and quantum information technologies, as a single photon emitter with excellent spectral properties. To obtain spectrally identical SiV– emitters, we doped homoepitaxial diamond films in situ with 28Si, 29Si, and 30Si isotopes using isotopically enriched (>99.9%) silane SiH4 gas added in H2–CH4 mixtures in the course of the microwave plasma-assisted chemical vapor deposition process. Zero-phonon line components as narrow as ∼4.8 GHz were measured in both absorption and luminescence spectra for the monoisotopic SiV– ensembles with a concentration of a few parts per billion. We determined with high accuracy the Si isotopic energy shift of SiV– zero-phonon line. The SiV– emission intensity is shown to be easily controlled by the doped epifilm thickness. Also, we identified and characterized the localized single photon SiV– sources. The developed doping process opens a way to produce the SiV– emitter ensembles with energy confined in an extremely narrow range.