Fig. 3. Passivation strategies. (a) (Left) AFM image of micromechanically exfoliated BP covered with PDI. Before the coverage with PDI, the BP has been rinsed with DI water. (Middle) AFM height profiles along line 1 after the coverage with PDI and 72 hours later. The nearly same shape of the height profiles illustrates the passivation effect of the PDI, temporarily preventing any oxidation phenomena. The inset shows the molecular structure of the used PDI: N-bis-(tert-butyl-(2,2′-aminobutylazanediyl)-diacetate)-3,4,9,10-perylene diimide. (Right) Mean Raman spectra of the non-covalently functionalized BP flake with PDI showing both the characteristic peaks of the BP as well as the fine structure of PDI peaks. (b) (Left) AFM image of micromechanically exfoliated BP which has been treated several times with DI water before IL was deposited to prevent oxidation. (Middle) AFM image of the corresponding flakes after they had been covered for 10 days by IL. (Right) Comparison of the A1g/A2g-ratio of the BP flakes before and after treatment with IL showing nearly no difference.
