Figure 2.

Ellman’s assay for the presence of free sulphhydryl (thiol) groups applied to edge-modified GNPs produced by ultrasonic exfoliation: a negative control containing 30 µl of graphene sulphonate and 10 µl Ellman’s reagent solution; b negative control containing 30 µl thiographene and 0 µl Ellman’s reagent solution; c 30 µl thiographene and 5 µl Ellman’s reagent solution; d 30 µl thiographene and 10 µl Ellman’s reagent solution; e positive control containing 30 µl 260 mM cysteine and 10 µl Ellman’s reagent solution. [Ellman’s reagent] = 10 mM; [graphene suspensions] = 0.5 g l⁻¹