Probing Chemical Functional Groups in Graphene Materials Using Thermogravimetric Analysis Pei Lay Yap, Fanxiang Lei, Gimhani Danushika, Farzaneh Farivar, Andrew J. Pollard, Dusan Losic Analytical Chemistry, 2026 Reliable characterization and quality control of manufactured graphene-related 2D materials are essential for defining structure-property relationships and enabling their broader industrial adoption. However, the robust identification and quantification of chemical functional groups in functionalized graphene remain significant analytical challenges. Conventional spectroscopic techniques, including Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and energy-dispersive X-ray spectroscopy (EDX), primarily provide qualitative or elemental information and generally lack the sensitivity and quantitative capability required for metrologically robust assessment of functionalization. Here, we systematically evaluate thermogravimetric analysis (TGA) as a complementary analytical method for probing chemical functional groups in functionalized graphene materials. A series of graphene samples functionalized with oxygen-, sulfur-, and nitrogen-containing groups was investigated, revealing distinct and reproducible mass-loss profiles associated with the thermal decomposition and oxidation of specific functional moieties bound to the graphene framework. Correlation of these thermal signatures with comprehensive structural and chemical characterization enables the assignment, differentiation, and quantification of functional groups with improved reliability. This TGA-based approach offers a cost-effective, scalable, and high-throughput pathway toward quantitative functional group analysis, supporting improved comparability, quality control, and standardization of graphene materials. The methodology provides new insights into graphene functionalization and supports its deployment in biomedical, energy storage, catalysis, sensors, coatings, and nanocomposite applications.
Influence of grain types and graphene nanopowder characteristics on insecticidal efficacy against common grain insects Evagelia Lampiri, Pei Lay Yap, Christos G. Athanassiou, Dusan Losic Discover Nano, 2025 The increasing resistance of insects to chemical-based pesticides is a critical challenge in crop production, demanding the urgent development of sustainable and effective pest control alternatives. In response, this study presents the insecticidal potential of graphene materials in the form of nanopowders as new chemical and resistance free grain protectants. The influence of the grain types such as rice, maize, and wheat and graphene nanopowder characteristics on insectidicial efficacy against common grain insects was evaluated against three most destructive grain insects including: the rice weevil, Sitophilus oryzae (L.) (Coleoptera; Curculionidae), the maize weevil, Sitophilus zeamais Motschulsky (Coleoptera; Curculionidae), and the red flour beetle, Tribolium castaneum Herbst (Coleoptera; Tenebrionidae). Three industrially produced graphene nanopowders with distinct physicochemical properties (particle size, surface chemistry, hydrophobicity) were used at two dosage rates (500 and 1000 ppm). Mortality of insects was assessed after 7, 14, and 21 days of exposure, and progeny production was evaluated after 65 days. The results indicated that S. oryzae exhibited the highest susceptibility among the tested species, with rice grains experiencing the most significant insect mortality across all graphene concentrations (500 and 1000 ppm). Significant reductions in progeny with minor produced insects were observed, especially in maize, highlighting the long-term protective effects of graphene nanopowders. The insectidicial mode of action is attributed to a physical mechanism involving the adhesion of graphene particles to insect bodies, obstructing respiration and disrupting the cuticle. These findings suggest that graphene nanopowders, due to their unique structural, chemical and interfacial properties, have a strong potential to be used as new grain protectants, providing unique physical mode of action.
High-performance arsenic removal from natural waters using a coiled flow inverter Rabia Sabir, Pei Lay Yap, Ammara Waheed, K.D.P. Nigam, Dusan Losic Environmental Technology and Innovation, 2025 Arsenic remains a contaminant of emerging interest in water pollution due to its significant threat to public health, removal of which is still challenging problem. To develop miniaturized, low-cost, sustainable and high-performing water purification systems for continuous removal of arsenic, this study leverages the advantages of enhanced radial mixing of coiled flow inverter (CFI) reactor. A comprehensive evaluation of CFI adsorptive removal of As(V) from natural waters using MgO nanoparticles was conducted to determine the impact of key parameters such as flowrates (10 mL/min, 135 mL/min), initial pollutant concentration (1-200 ppm As(V)), adsorbent dosage (0.2-2 mg/mL), pH (2-10) and competing ions (phosphate, sulphate, chloride and carbonate). Findings showed experimental adsorption capacity of 184 mg/g and 98% adsorption efficiency for As(V) were achieved within 38 seconds at a flow rate of 135 mL/min, initial As(V) concentration of 10 mg/L and adsorbent dosage of 1.5 mg/mL. To demonstrate its practical application, studies performed on selectivity in the presence of co-ions (phosphate, sulphate, chloride and carbonate), water matrix using real water (Torrens River water) showing good selectivity (72-78%) and recycling (99% after 5 cycles) potential. Benchmarking experiments in batch and CFI reactor verified that outstanding removal efficiency (98%) can be attained in 38 seconds at 135 mL/min flow rate in a CFI reactor compared to 24 hrs in a batch reactor, demonstrating the efficacy of the miniaturized compact device based on CFI as a new-generation practical water purification technology. • Coiled flow inverter as a compact microreactor for advanced adsorption • Improved mixing with lower cost, time and footprint via coiled flow inverter • Ultrafast arsenic removal (98%) in 38 seconds via CFI, outperforming batch process • High arsenic removal (> 98%) at 0.5 and 1 ppm As (V) using river water sample Remarkable regeneration efficiency via coiled flow inverter (> 90%) after 5 cycles
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.
Unveiling cutting-edge advances in high surface area porous materials for the efficient removal of toxic metal ions from water Padmaja V. Mane, Richelle M. Rego, Pei Lay Yap, Dusan Losic, Mahaveer D. Kurkuri Progress in Materials Science, 2024 This review offers a comprehensive evaluation of an emerging category of adsorbing materials known as high surface area materials (HSAMs) in the realm of water remediation. The objective is to shed light on recent advancements in HSAMs featuring multiple dimensionalities, addressing their efficacy in adsorbing toxic metal ions from wastewater. The spectrum of HSAMs examined in this review encompasses metal–organic frameworks (MOFs), covalent organic frameworks (COFs), carbon-based porous materials, mesoporous silica, polymer-based porous materials, layered double hydroxides, and aerogels. This review delves into the state-of-the-art design and synthetic approaches for these materials, elucidating their inherent properties. It particularly emphasizes how the combination of high surface area and pore structure contributes to their effectiveness in adsorbing toxic metal ions. These materials possess remarkable attributes, including molecular functionalization versatility, high porosity, expansive surface area, distinctive physicochemical characteristics, and well-defined crystal structures, rendering them exceptional adsorbents. While each of these materials boasts unique advantages stemming from their remarkable properties, their synthesis often entails intricate and costly procedures, presenting a substantial obstacle to their commercialization and widespread adoption. Finally, the review underscores the existing challenges that must be addressed to expedite their translation for water remediation applications of these promising materials.
Graphene powders as new contact nanopesticides: Revealing key parameters on their insecticidal activity for stored product insects Evagelia Lampiri, Pei Lay Yap, Panagiotis Berillis, Christos G. Athanassiou, Dusan Losic Chemosphere, 2024 The overuse and reliance on pesticides has caused insects to develop resistance with global concerns. To address this problem extensive research is directed to find new and sustainable alternatives using chemical-free and resistance-free solutions for pest control. This paper presents a comprehensive investigation of the insecticidal properties of several types of industrially produced graphene powder materials such as graphene and graphene oxide (GO) with micro- and nano size and different structural and chemical properties as new contact nanopesticides against three major stored grain insects: the rice weevil Sitophilus oryzae (L.), the lesser grain borer, Rhyzopertha dominica (F.)˙ and the larger grain borer, Prostephanus truncatus Horn. Bioassays were performed using different concentrations, i.e., 0, 100, 500 and 1000 ppm of graphene powders on the mortality of selected adult insects recorded after 3, 7, 14, and 21 days of exposure and progeny production after 65 days. Results showed that graphene oxide (GO) has no insecticidal efficacy while graphene powders with nano-size particles showed significantly enhanced insecticidal performance compared to micron-size graphene powders. The observed insecticidal effects are explained by the higher probability that nano-sized graphene particles adhere on the insect body compared to large particles. The mortality is proposed as the result of physical mode of action of attached graphene nanoparticles causing stronger interruption of the protective cuticle layer, gas respiratory functions and faster mortality. The findings of this study revealed that it is important to select graphene materials with optimal structural and interfacial properties to achieve the highest insecticidal performance in potential development of a new generation of sustainable insecticides.
Advancing carbon dioxide capture: Unravelling structure-property-performance dynamics in graphene related two-dimensional materials Pei Lay Yap, Huynh Hong Nguyen, Md Julker Nine, Jun Ma, Manju Gunawardana, Dusan Losic Materials Today Sustainability, 2024 Efficient design of adsorbents for carbon dioxide (CO2) capture is imperative in addressing the challenges caused by climate change. In this study, a comprehensive exploration of solid adsorbents derived from graphene-related two-dimensional materials (GR2Ms) with tunable surface chemistry and structures was undertaken to unravel the intricate structural-property-activity relationships essential for optimizing their CO2 adsorption. Nine key GR2Ms and carbon materials including few-layer graphene (FLG), two types of graphene oxide (GO) and reduced graphene oxide (rGO), expanded graphite (Exp Gft), rGO-Exp Gft, graphite (Gft), were methodically characterized alongside benchmarked materials such as activated carbon (AC) and molecular sieves (MS). Characterization parameters encompassed morphology, particle size, interlayer distance, crystallite size, defect density, specific surface area (SSA), total pore volume, micropore volume, and pore size, are correlated with CO2 adsorption capacity. Results revealed that the dominant properties influencing CO2 adsorption in GR2Ms are hierarchical porous morphology, defect density (up to 2.38 ×1011 cm-2), SSA (up to ∼271 m2/g), total pore volume (up to 0.86 cm3/g), and micropore volume (up to 0.03 cm3/g), establishing positive linear relationships. Conversely, crystallite size (0.38-48 nm) exhibited an inverse (non-linear) relationship with CO2 adsorption capacity under ambient conditions (25 °C and 1 atm). Particle size (8-52 μm), interlayer distance (0.33-0.89 nm), and pore size (4.2-13.3 nm) of GR2Ms showed negligible impact on CO2 adsorption capacity. Remarkably, porous rGO emerged as the top-performing CO2 adsorbent with an enhanced adsorption capacity (5.38 mmol/g), surpassing all the studied GR2Ms and benchmarked adsorbents, including activated carbon (AC, 1.79 mmol/g) and molecular sieve (MS, 1.48 mmol/g) under ambient conditions. This study establishes a comprehensive structure-property-performance relationship, highlighting the significance of a three-dimensional (3D) hierarchical, open, and interconnected pore structure within the graphene network, along with the highest pore volume and minimum crystallite size of rGO. These findings underscore the critical role of structural and porosity attributes of GR2Ms in CO2 adsorption, providing fundamental insights into the interplay between the structure and properties on their CO2 adsorption behavior. This study emphasizes the key pillars for effective adsorbent design and underlines the necessity of optimized control over the structural characteristics and porosity of GR2Ms to enhance their CO2 adsorption capabilities, contributing towards the ambitious net-zero target by 2050.
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.
International Interlaboratory Comparison of Thermogravimetric Analysis of Graphene-Related Two-Dimensional Materials Pei Lay Yap, Farzaneh Farivar, Åsa K. Jämting, Victoria A. Coleman, Sam Gnaniah, Elisabeth Mansfield, Cheng Pu, Sandra Marcela Landi, Marcus Vinícius David, Emmanuel Flahaut, Mohammed Aizane, Michael Barnes, Mary Gallerneault, M. Dominique Locatelli, Sébastien Jacquinot, Carlton Gray Slough, Jörg Menzel, Stefan Schmölzer, Lingling Ren, Andrew J. Pollard, Dusan Losic Analytical Chemistry, 2023
International interlaboratory comparison of Raman spectroscopic analysis of CVD-grown graphene Piers Turner, Keith R Paton, Elizabeth J Legge, Andres de Luna Bugallo, A K S Rocha-Robledo, Ahmed-Azmi Zahab, Alba Centeno, Alessio Sacco, Amaia Pesquera, Amaia Zurutuza, Andrea Mario Rossi, Diana N H Tran, Diego L Silva, Dusan Losic, Farzaneh Farivar, Hugo Kerdoncuff, Hyuksang Kwon, Jerome Pirart, João Luiz E Campos, Kiran M Subhedar, Li-Lin Tay, Lingling Ren, Luiz Gustavo Cançado, Matthieu Paillet, Paul Finnie, Pei Lay Yap, Raul Arenal, Sanjay R Dhakate, Sebastian Wood, Sergio Jiménez-Sandoval, Tim Batten, Vaiva Nagyte, Yaxuan Yao, Angela R Hight Walker, Erlon H Martins Ferreira, Cinzia Casiraghi, Andrew J Pollard 2d Materials, 2022
