| XRD and Raman at 1200 °C | Adamantane produced cubic-diamond (111), (220), and (311) reflections, a first-order Raman line near 1331 cm⁻¹, a second-order feature near 2445 cm⁻¹, and C–H stretching bands; nitrogen-substituted precursors produced graphite-dominated products with graphite (002) diffraction and Raman D and G bands, while 2-AmAd also showed a weak diamond (111) reflection |
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| XRD at 1370 and 1500 °C | At 1370 °C, graphite reflections disappeared for 2-AzaAd, 2-AmAd, 1-CNAd, and 1-N₃Ad, while 1-AmAd remained predominantly graphitic; at 1500 °C, every substituted precursor produced a diamond-dominated product |
| ATR-FTIR | Products from substituted precursors retained hydrogen-rich surface terminations and showed nitrogen-related features assigned to P1 and A centres |
Xin Yang, Christopher P. Ender, Qi Lu, András Kovács, Angelica P. Orlova, Wilson Crichton, Raúl Gonzalez Cornejo, Rémi Blinder, Christian Laube, Wolfgang Knolle, Fedor Jelezko, Yingke Wu, Tanja Weil. “Why diamondoid nanodiamond precursors lose their defect blueprint under HPHT conditions: a graphitic conversion pathway.” ChemRxiv (). https://doi.org/10.26434/chemrxiv.15007827/v1
Values presented only in X-ray-diffraction, Raman, ATR-FTIR, transmission-electron-microscopy, gas-chromatography–mass-spectrometry, photoluminescence, electron-paramagnetic-resonance or optically-detected-magnetic-resonance plots or images were not transcribed. The main paper refers to supporting information, but no separate supporting information file was available on the ChemRxiv article page
| TEM and X-band EPR, adamantane | First diamond-dominated product at 1200 °C; approximately 10 nm at 1200 °C, 2–5 nm at 1370 °C, and 98 ± 42 nm at 1500 °C; P1 centres not detected |
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| TEM and X-band EPR, 2-AzaAd | First diamond-dominated product at 1370 °C; 101 ± 58 nm at 1370 °C and 269 ± 152 nm at 1500 °C; maximum P1 concentration 411.5 ppm |
| TEM and X-band EPR, 1-AmAd | First diamond-dominated product at 1500 °C; 297 ± 140 nm at 1500 °C; maximum P1 concentration 215.3 ppm |
| TEM and X-band EPR, 2-AmAd | First diamond-dominated product at 1370 °C; 341 ± 118 nm at 1370 °C and 388 ± 266 nm at 1500 °C; maximum P1 concentration 265.1 ppm |
| TEM and X-band EPR, 1-CNAd | First diamond-dominated product at 1370 °C; 130 ± 43 nm at 1370 °C and 473 ± 234 nm at 1500 °C; maximum P1 concentration 453.6 ppm |
| TEM and X-band EPR, 1-N₃Ad | First diamond-dominated product at 1370 °C; 34 ± 11 nm at 1370 °C and 36 ± 13 nm at 1500 °C; maximum P1 concentration 351.4 ppm |
| Raman and GC-MS | Precursor preservation followed 1-N₃Ad < 1-CNAd, 2-AzaAd < 2-AmAd < 1-AmAd < adamantane; adamantane showed essentially no detectable decomposition; 1-AmAd and 2-AmAd retained pronounced sp³ C–H bands from 2900 to 3000 cm⁻¹, residual precursor, deaminated adamantane, and slightly higher-mass oligomers; 2-AzaAd and 1-CNAd showed prominent Raman D and G bands; 1-N₃Ad showed no residual precursor, while adamantane and 1-AmAd were detected among its products |
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| Time-resolved ex situ XRD at 1370 °C | After 1 min, graphite was observed without detectable diamond reflections; after 5 min, a weak diamond (111) reflection appeared with graphite; after 15 min, graphite reflections disappeared and diamond became the dominant phase; longer heating sharpened the diamond (111) peak |
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| In situ synchrotron XRD | The crystalline precursor signal collapsed near 940 °C while a broad feature appeared at a d-spacing of approximately 2.9 Å; the feature persisted without diamond reflections to approximately 1300 °C and shifted to approximately 3.4 Å after quenching and decompression; the recovered product showed Raman D and G bands |
| Photoluminescence | Broad emission features included weak signals near the expected NV⁰ and NV⁻ zero-phonon-line positions in some samples |
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| X-band EPR at 1370 °C | P1 concentrations were 398.4 ppm for 2-AzaAd, 256.9 ppm for 1-N₃Ad, 53.4 ppm for 1-CNAd, and 48.3 ppm for 2-AmAd; no clear NV⁻ signal was observed in any as-synthesized ensemble |
| ODMR, 2-AmAd-1500 | Scarce NV-related emission and broad ODMR features were detected in isolated nanodiamonds; vacuum annealing at 800 °C did not produce a pronounced NV signal |
| EPR and ODMR after electron irradiation at 720 °C, 2-AmAd-1500 | Half-field EPR showed an NV⁻ signal with an estimated concentration of 0.8 ± 0.15 ppm; spin relaxation time T1 was 2.85 ms and Hahn-echo coherence time T2 was 0.74 µs |