Geopolymers are emerging as sustainable alternatives to Ordinary Portland Cement (OPC), offering high strength, lightweight properties, and a lower environmental impact, making them promising materials for green concrete technologies. In this study, we synthesized graphene-based geopolymer nanocomposites using various functional graphene derivatives, such as graphene oxide (GO), sulfonated graphene oxide (G-SO3H) thiographene (G-SH), and phosphate graphene (G-PO3H), along with alumina- and silica-rich waste materials, such as fly ash and dolomite, to enhance mechanical properties, including setting time, flowability, compressive strength, and water absorption. The functional groups on graphene derivatives improve the particle dispersion and matrix density, enhancing compressive strength, while Raman spectroscopy reveals spectral shifts at interfaces of phosphate graphene with dolomite and fly ash, indicating interactions. The resultant FDGP exhibits a significantly higher compressive strength of 45.60 MPa at 7 days and 50.20 MPa at 28 days compared to GO, G-SH, and G-SO3H. The high concentration of phosphate functional groups promotes strong interactions with the geopolymer matrix, improving its workability. Furthermore, density functional theory (DFT) calculations elucidate the role of functional groups in graphene-based geopolymer concrete, enhancing molecular interactions and promoting robust interfacial adhesion with the geopolymer matrix for a superior performance. We studied the time-dependent interactions of functionalized graphene oxide phosphate using DFT and other characterization methods, revealing strong hydrogen bonding that enhances dispersion and reinforcement within the geopolymer matrix.

• Keywords
• compressive strength, density functional theory (DFT), fly ash (FA), functional graphene derivatives, geopolymers, interfacial chemistry, water absorption,
• Publication type
• Journal Article MeSH

To enhance the sustainability of nuclear energy and protect the environment, the efficient extraction of uranium from various water sources has emerged as an essential strategy for addressing the long-term challenges of nuclear waste management. In this study, we designed phosphoryl-functionalized graphene (PG) for efficient uranyl adsorption and synthesized the material from fluorinated graphene using phosphoryl ethanolamine under solvothermal conditions. The resultant PG features a unique 2D structure equipped with solvent-exposed phosphoryl groups, making it highly suitable for uranium adsorption in aqueous solutions. Notably, PG demonstrated a high sorption efficiency (∼77%) with rapid extraction capability (∼5 min) for U(VI) from aqueous media at pH 7, achieving an adsorption capacity of 316 mg U g-1. It also demonstrates good recyclability and stability even after 3 cycles and exhibits a significant seawater adsorption capacity of 117.8 mg U g-1. Both X-ray photoelectron spectroscopy analysis and molecular dynamics simulations revealed a preferential binding of uranyl ions to the phosphoryl groups of PG. This work paves the way for designing and developing functional graphene derivatives for efficient uranium extraction from various water resources, with promising potential for the recovery of other radioactive elements.

• Keywords
• graphene derivatives, molecular dynamics simulations, phosphoryl-functionalized graphene, two-dimensional (2D) materials, uranium adsorption,
• Publication type
• Journal Article MeSH

Noble gases, notably xenon, play a pivotal role in diverse high-tech applications. However, manufacturing xenon is an inherently challenging task, due to its unique properties and trace abundance in the Earth's atmosphere. Consequently, there is a pressing need for the development of efficient methods for the separation of noble gases. Using mild fluorographene chemistry, nitrogen-doped graphene (GNs) materials are synthesized with abundant aromatic regions and extensive nitrogen doping within the vacancies and holes of the aromatic lattice. Due to the organized interlayer "nanochannels", nitrogen functional groups, and defects within the two-dimensional (2D) structures, GNs exhibits effective selectivity for Xe over Kr at low pressure. This enhanced selectivity is attributed to the stronger binding affinity of Xe to GN compared to Kr. The adsorption is governed by London dispersion forces, as revealed by theoretical calculations using symmetry-adapted perturbation theory (SAPT). Investigation of other GNs differing in nitrogen content, surface area, and pore sizes underscores the significance of nitrogen functional groups, defects, and interlayer nanochannels over the surface area in achieving superior selectivity. This work offers a new perspective on the design and fabrication of functionalized graphene derivatives, exhibiting superior noble gas storage and separation activity exploitable in gas production technologies.

• Keywords
• 2D materials, defect engineering, noble gas separation, selectivity, symmetry‐adapted perturbation theory (SAPT), xenon,
• Publication type
• Journal Article MeSH

Covalent hybrids of graphene and metal-organic frameworks (MOFs) hold immense potential in various technologies, particularly catalysis and energy applications, due to the advantageous combination of conductivity and porosity. The formation of an amide bond between carboxylate-functionalized graphene acid (GA) and amine-functionalized UiO-66-NH2 MOF (Zr6O4(OH)4(NH2-bdc)6, with NH2-bdc2- = 2-amino-1,4-benzenedicarboxylate and UiO = Universitetet i Oslo) is a highly efficient strategy for creating such covalent hybrids. Previous experimental studies have demonstrated exceptional properties of these conductive networks, including significant surface area and functionalized hierarchical pores, showing promise as a chemiresistive CO2 sensor and electrode materials for asymmetric supercapacitors. However, the molecular-level origin of the covalent linkages between pristine MOF and GA layers remains unclear. In this study, density functional theory (DFT) calculations were conducted to elucidate the mechanism of amide bond formation between GA and UiO-66-NH2. The theoretical calculations emphasize the crucial role of zirconium within UiO-66, which acts as a catalyst in the reaction cycle. Both commonly observed hexa-coordinated and less common hepta-coordinated zirconium complexes are considered as intermediates. By gaining detailed insights into the binding interactions between graphene derivatives and MOFs, strategies for tailored syntheses of such nanocomposite materials can be developed.

• Publication type
• Journal Article MeSH