Reduced graphene oxide synthesis using glucose, fructose and galactose: a Taguchi–TOPSIS evaluation of structure–property relationships

Reduced graphene oxide (rGO) was synthesized by hydrothermally reducing graphene oxide (GO) with D-glucose, D-fructose, or D-galactose. A Taguchi L9 design examined temperature (80, 150, and 250 °C), sugar type, alkaline reagent (NaOH, KOH, or NH4OH), and pH (3, 7, or 9). Products were characterized by ATR-FTIR, Raman spectroscopy, XRD, SEM–EDS, BET surface-area analysis, zeta potential, and hydrodynamic particle-size measurements, with XPS providing complementary surface-chemical evidence. Six responses—ID/IG, C/O ratio, specific surface area, absolute zeta potential, hydrodynamic particle size, and apparent crystallite size—showed different preferred factor levels. Their signal-to-noise ratios were integrated through equally weighted TOPSIS analysis. Among nine tested conditions, rGO9 (250 °C, D-galactose, KOH, pH 3) yielded the highest TOPSIS closeness coefficient. Compared with GO, its C/O ratio increased from 1.97 to 4.66 and particle size decreased from 271.0 to 203.8 nm, whereas specific surface area and absolute zeta potential decreased. These findings demonstrate that combining renewable carbohydrate-based reducing agents with Taguchi–TOPSIS optimization provides a systematic framework for selecting rGO synthesis conditions according to the physicochemical properties required for potential applications, supporting the development of more sustainable graphene-derived materials.