(Color online) Carbon nanomaterials classification: (a) sp 2-hybridized carbon: fullerene, CNT, and graphene; (b) sp 3-hybridized carbon: diamondoids compared with 381-carbon tetrahedral diamond. For clarity, the H-terminations are not shown except for those in adamantane.
(Color online) Experimental setup for the laser ablation of HOPG in scCO2 with and without cyclohexane as a cosolvent, including dissolved adamantane: (a) top view and (b) magnified side view.
Experimental setup for pyrolysis treatment of the samples.
(Color online) Micro-Raman spectra of synthesized products obtained by PLA (a) in scCO2 before pyrolysis and (b) after pyrolysis; (c) in scCO2 with cyclohexane before pyrolysis, and (d) after pyrolysis, (e) in scXe before pyrolysis.13 For illustrating the effect of increasing cage number, the Raman spectra of (f) commercial adamantane and (g)  hexamantane (taken from Ref. 22) are also included as examples.
(Color online) GC-MS mass spectra at t = 7.3 min: (a) the synthesized product obtained in neat scCO2, (b) scCO2 and cyclohexane, and (c) diamantane of the standard sample, with the inset showing the structure of diamantane.
(Color online) Calibration curve fitted to the GC-MS SIM peak area corresponding to m/z 188 in cyclohexane solution with dissolved diamantane. The GC-MS scan rate was 1.79 scans/s.
(Color online) Number of cages in diamondoids obtained by scCO2 with and without cyclohexane plotted as a function of the GC-MS relative retention time, taking the retention time of diamantane as a standard.
GC-MS mass spectra of possible superadamantane (MW 456) obtained by PLA in scCO2. The inset shows the molecular structure.
GC-MS mass spectra of possible diamondoids after pyrolysis: MW 448 (heptamantane, C34H40) obtained by PLA in scCO2 with cyclohexane. The inset shows  heptamantane, which is one of the possible isomers possessing MW of 448.
Experimental conditions for the pulsed laser ablation in scCO2 with and without cyclohexane.
SIM peak area and estimated diamantane concentration of the product obtained by PLA in scCO2.
List of possibly synthesized diamondoids by PLA in scCO2, with their molecular formulae, MWs, GC-MS relative retention times, and dual graph codes.
List of possibly synthesized diamondoids by PLA in scCO2 with cyclohexane as a cosolvent, with their molecular formulae, MWs, GC-MS relative retention times, and dual graph codes.
List of observed higher diamondoids for PLA in scCO2 after pyrolysis.
List of observed higher diamondoids for PLA in scCO2 with cyclohexane after pyrolysis.
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