Advancing Methylene Blue Adsorption Approach for More Precise Measurement of Specific Surface Area of Graphene Oxide

Abstract

The industrial production of graphene oxide (GO) using various oxidizing precursors and processing conditions results in substantial variability in their composition of oxygen-containing groups, structures, and specific surface area (SSA), which are critical to its performance in diverse applications. Spectrophotometric methylene blue (MB) adsorption has emerged as a promising alternative to the conventional nitrogen physisorption method. However, this method still lacks a standardized and optimized protocol, limiting its reliability and consistency in SSA determination. To address this gap, this study systematically evaluates the uncertainties in the MB-based SSA characterization by revealing the influence of key experimental parameters and their optimization, including adsorption time, GO and MB concentration, MB/GO ratio, and the methods for determining maximum MB adsorption capacity on GO using both single-point and multi-point Langmuir isotherm approaches. A series of commercial and lab-prepared GOs materials in different forms (powders, aerogels, films, and dispersions) are used as model systems. The study confirms the optimized parameters, including adsorption time (24 h), concentrations of MB (0.005–0.02 mg mL−1), GO (0.5–2.0 mg mL−1), MB/GO weight ratio (0.4–0.44), and single-point MB adsorption. This refined protocol offers a robust, rapid, low-cost, and reliable characterization and quality control of manufactured GO materials.