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J. Eur. Opt. Society-Rapid Publ. 21, 7( 2025)
Figure 5. Processes performed on 125 nm and 180 nm in order to optimize their optical properties.
[ 71 ], this level of thermal oxidation has proven effective in removing surface quenching phases associated with disordered sp 2 / sp 3 carbon and enhancing photoluminescence, while avoiding size reduction and affecting the diamond phases at the basis of the optical properties.
Larger NDs( MSY 0-0.35) with a median size of 180 nm are also analysed in this work. In this case samples are processed with 2 h at 800 ° C thermal annealing in N 2 flow, followed by 12 h at 500 ° C thermal air oxidation.
Future perspectives
In perspective, luminescent nanodiamonds( LND) are emerging as a powerful tool for advanced optical resolution standards, offering unique capabilities that hold promise for the future of nanoscale imaging and metrology. These nanoparticles, typically less than 100 nm in diameter, can be doped with colour centres( such as nitrogen-vacancy centres) that emit bright and stable fluorescence under various conditions. This luminescence, combined with the exceptional photostability and biocompatibility of nanodiamonds, makes LNDs ideal candidates for high-resolution optical standards. In the future, LNDs are expected to play a critical role in SRM techniques, such as STED microscopy and single-molecule localization microscopy( SMLM). Their luminescence properties enable accurate calibration of imaging systems, allowing for better resolution beyond the diffraction limit of light. Furthermore, LNDs can serve as a reference for quantifying spatial resolution, validating imaging algorithms, and correcting optical aberrations in these advanced microscopes. As ion‐beam-based fabrication techniques advance, it is becoming increasingly possible to produce luminescent nanodiamonds with tailored optical properties and precisely engineered shapes and sizes. This customization could lead to the creation of a new class of optical standards with unparalleled specificity and adaptability for various imaging modalities.
4.2 Wide-field Imaging with Super-resolution Enabled by Raman Scattering( WISERS)
The above scheme has been implemented to acquire labelfree imaging using Raman signals [ 73, 74 ].
The spatial frequency with wave-vector k s was projected on the sample plane at three phase angles and three orientations. The super-resolution image was reconstructed using the fairSIM plug-in in ImageJ [ 75 ]. An implanted diamond sample( c. f. Sect. 4.1) was used that include NV vacancies in the nanoscale domains of sp 3 hybridised diamond clusters surrounded by sp 2 hybridised graphitic layer [ 76 ]. The signal from the sample appeared as a convoluted peak around 1410 cm �1 which is likely to be a combination of the 1332 cm �1 diamond, the PL signal and the D-peak from graphitic carbon.
The results are shown in Figure 6. Hyperspectral image was acquired using Fourier-transform interference method using birefringent crystals. A representative spectrum acquired using the interferometer is compared with that obtained using a monochromator( Fig. 6a). A wide-field image acquired using wide-field illumination and collection using a narrow band filter is shown in Figure 6b, that shows a distribution of the emitting centres although these could not be resolved clearly. The same area was subsequently imaged using a narrow band filter and structured illumination with line spacing of 1200 nm projected on the sample plane( Fig. 6c). Nine images were acquired with three phase angles and three orientations of the lines, and the superresolution image was reconstructed. Clearly, there is a significant improvement in clarity of the image. The improvement is due to the expansion of the total k-vector( k 0 + k s) that allowed to capture the high frequency features of the sample. The clarity of the image improved further by acquiring the imaging using hyperspectral imaging. This improvement is highlighted in Figures 6b1 – 6d1 which are the zoomed-in regions of the marked areas in the corresponding Figures 3b – 3d. The intensity profiles