Fig. 1. (A) TEM image of a 1 mg mL⁻¹ dCD dispersion in water. The TEM image reveals quasi-spherical dots with a calculated particle size of 7.3 ± 1.2 nm – inset: particle size distribution shows that the particle size spans 5–9 nm; (B) AFM image of dCDs on a mica substrate. The height profile is 1.4 nm as shown in the inset; (C) room temperature absorbance and fluorescence spectra of a 50 μg mL⁻¹ dCD dispersion. The UV-Vis absorption spectrum of dCDs (black curve) reveals three absorption bands centered at 295–350 nm, 370–450 nm and 590–690 nm. Following excitation at 405 nm, two fluorescence bands are observed at 370–500 nm and 640–730 nm (blue curve) while excitation at 640 nm reveals red fluorescence from 645–730 nm (red curve); (C, inset) dCD dispersion under white light (left) and UV light (λ_ex = 365 nm; right). The violet color is from the contribution of both blue and red fluorescence.