TABLE 1.

List of methods for controlling the size of nGO sheets.

	General Method	Specific strategy	Feature size	References
Direct Controllable Synthesis	Different Precursors	Graphite Nanofibers: very small graphite plates (diameter about 130 nm and length up 5 μm) stacked in particular conformation	100-50 nm	Luo et al., 2010
		Arc-discarge Material: carbon material highly flexible and defective obtained by electrical breakdown	20-40 nm	Rosillo-Lopez and Salzmann, 2016
		Aphanatic Graphite: kind of graphite with disorder structure obtained by thermal decomposition of deep metamorphic	4.5 nm	Shen et al., 2020
	Reaction Parameters	Time and Oxidant Amounts: increase in the amount of oxidizing agent and timescale of oxidation in the same batch	50-20 nm	Zhang L. et al., 2009, Zhang et al., 2013
		More Oxidation Cycles: for each cycle the obtained product was isolated, purified and re-oxidized	10-5 nm	Fan et al., 2015
	Physical Promoters	Ultra Sonication: application of sound energy in a water bath or through probes to break GO sheets in low temperature conditions	100-500 nm	Farazas et al., 2018; Méndez-Romero et al., 2020
		Ball Milling: graphite with or without solvents or oxidants was mechano-chemical oxidized in a rotating cylindrical jar filled with loose grinding balls.	depending on conditions from μm to 30-50 nm	Posudievsky et al., 2012; Mahmoud et al., 2018; Luo D. et al., 2019
Post-synthesis Separation	Centrifugation	Differential Centrifugation Method: GO sheets to be separated was divided in several fractions according to their size by varying the centrifugal force applied	250-900 nm	Chen et al., 2013b; Huang and Yuan, 2016
		Density Gradient Centrifugation: GO to be separated was placed on the surface of a vertical column of liquid with increased density from top to bottom and centrifuged. The particles migrated through the solvent gradient and settled where their buoyancy density equaled that of the gradient	40-500 nm	Sun et al., 2010; Li et al., 2013; Bidram et al., 2016
	Flocculation by Solvent	Protonation in Organic Solvents: large GO sheets precipitated selectively in organic solvents by protonation of carboxyl groups on the edges	500-100 μm	Zhang et al., 2015
		pH Assisted Precipitation: nGO sheets were recovered from the strongly acidic precipitate obtained from the work-up of the classic oxidation reaction by increasing pH value to 1.7 with 1M NaOH	90 nm	Hu et al., 2015