**Acknowledgements**

considers 3 g of graphite and 9 g of KMnO4 in 400 ml of solution). Here, the KMnO4/graphite ratio (3:1) was maintained in order to not alter the degree of oxidation. This way, the amount of these materials was progressively increased. It was observed that it was possible to use up to 15 g of graphite (and hence 45 g of KMnO4) in 400 ml of solution without altering the characteristics and quality of the product. **Figure 8** schematically summarizes the differences between the original method (*Improved Hummers method*) and the optimized one (*Optimized*

**Graphite Improved Hummers**

La (nm) 263 26.5 20.4

Lc (nm) 20 4.7 4.9 d002 (nm) 0.334 0.810 0.910 Nc 60 5.8 5.4

C 98.04 48.8 51.4 O 1.96 48.2 45.1 S 0.0 0.7 2.8 Cl 0 0.8 0.6 Mn 0 1.4 0.1

Raman spectroscopy *I*D/*I*<sup>G</sup> 0.067 0.726 0.946

**DRX** La (nm) 41 9.6 10.1

**method**

1.7 22.2 28.1

0.038 0.113 0.129

**La:** crystal dimension described by layer sized; **Lc**: stack height; **Nc:** number of layers in the stacking structure; **C:**

**Table 4.** Characterization results of graphite oxide synthesized using both the *Improved Hummers* and *Optimized*

**Table 4** lists some properties of the graphite oxide samples synthesized by the *Optimized Improved Hummers method* and those prepared from the parent one. *I*D/*I*<sup>G</sup> ratio, related with the structural disorder in the graphite network and inversely proportional to the sp2 cluster average sized [72], considerably increased after graphite oxidation. Crystal dimension (La value) decreased after the incorporation of oxygenated groups, which agree with the increase in the structural disorder. In the same way, the number of graphene layers in the stacking

**Optimized Improved Hummers method**

*Improved Hummers method*).

12614 Recent Advances in Graphene Research

**BET** Surface area

*Improved Hummers methods*.

(m2 /g)

Total pore volume (cm3

carbon, **O:** oxygen, **S:** sulfur, **Cl:** chlorine; **Mn:** manganese.

/g)

**Elemental composition**

**SEM**

The present work was performed within the frame of the NANOLEAP project. This project has received funding from the European Union's Horizon 2020 research and innovation programme under grant agreement No 646397.
