Advancing Methylene Blue Adsorption Approach for More Precise Measurement of Specific Surface Area of Graphene Oxide Pei Lay Yap, Deyu Wang, Dusan Losic Advanced Materials Interfaces, 2025 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.
Quantifying the Epoxide Group and Epoxide Index in Graphene Oxide by Catalyst-Assisted Acid Titration Gimhani Danushika, Pei Lay Yap, Dusan Losic Analytical Chemistry, 2024 Graphene oxide (GO), having diverse oxygen functional groups, including carboxyl, hydroxyl, carbonyl, and epoxy groups, is a significant graphene-related 2D material (GR2M) essential for various applications. The quantification of these functional groups traditionally utilizes Boehm acid titration, which, however, does not account for epoxy groups crucial for these applications. Presently, there exists no analytical method enabling quantitative assessment of the concentration of epoxy groups in GO available in the market in different forms such as powders, pastes, and dispersions. This paper presents a new approach employing catalyst-assisted acid-water-based titration to quantify epoxy groups in GO materials. The method's efficacy was validated using a well-characterized reference GO sample and tested on commercially produced GO powders, yielding epoxy group concentrations ranging from 1.15 ± 0.047 to 1.37 ± 0.051 mmol/g with high precision and reproducibility. The method introduces two new quality parameters, including the epoxide index (EI) and the equivalent epoxide weight (EEW) not implemented for GO before. Control measurements with a commercial epoxide material of known epoxide content demonstrated excellent agreement by using the proposed approach. Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) were used for comparative characterizations of epoxide groups in GO samples during titrations.
Refining and Validating Thermogravimetric Analysis (TGA) for Robust Characterization and Quality Assurance of Graphene-Related Two-Dimensional Materials (GR2Ms) Dusan Losic, Farzaneh Farivar, Pei Lay Yap C Journal of Carbon Research, 2024 Graphene-related two-dimensional materials available on the global market are manufactured using various production methods, with significant variations in properties and qualities causing serious concerns for the emerging multi-billion graphene industry. To address the limitations of conventional characterization methods probing the properties of individual graphene particles which may overlook the presence of non-graphene carbon impurities at a large (bulk) scale, this paper presents the refining thermogravimetric analysis as a complementary method for the reliable chemical characterization and quality control of graphene powders. A systematic parametric investigation of key experimental conditions such as sample mass and loading, heating rate, and gas environment and flow rate is performed to identify optimized settings for reliable thermal gravimetric measurements. These optimized conditions are evaluated through a series of comparative characterizations using industrially produced graphene, graphene oxide, and reduced graphene oxide powders, including their common carbon impurities. The ability of this method to provide both qualitative and quantitative analyses for characterizing graphene-related materials is confirmed. The optimized method is finally validated through an International Laboratory Comparison study and subsequently incorporated into a new standard. This low-cost, industry-affordable, and complementary characterization method is expected to enhance the quality control of manufactured graphene materials and make a valuable contribution to the growing graphene industry.
