analyzed or used immediately aer their synthesis.
To increase the distance between graphene layers and to promote layer sepa-ration, the IC was subjected to high-speed thermal expansion by means of microwave irradiation. Rapid heating of the GIC results in an abrupt conversion of the intercalated species into the gas phase, thus, causing expansion of the graphite planes along the c-axis.21,22 The resulting expanded graphite (EG) has a porous worm-like structure, as shown in Fig. 1c, with a signicantly increased specic volume (more than 300 times larger compared to the initial IC). In the next step, EG with concentrations of up to 1.4 mg ml1 was dispersed in a mixture of i-propanol and n-butanol to obtain a colloidally stable dispersion (Fig. 1d). For ink formulation we opted for the highest graphene content vs. a reasonable colloidal stability. We found experimentally that at a graphene concentration of 1.4 mg ml1 against 5 mg ml1 of surfactant, the ink is colloidally stable for more than 9 months, whilst also providing a maximum graphene to surfactant ratio.