Theoretical study of glycine amino acid adsorption on graphene oxide

Combined computational and experimental study about the incorporation of phosphorus into the structure of graphene oxide

Phosphorus-containing graphene-based hybrids are materials with outstanding properties for diverse applications. In this work, an easy route to produce phosphorus-graphene oxide hybrid materials is described, involving the use of variable amounts of H₃PO₄ and H₂SO₄ during the reaction of oxidation of a graphitic precursor. The physical and chemical features of the hybrids change significantly with the variation in the acid amounts used in the syntheses. XPS and solid-state ¹³C and ³¹P NMR results show that the hybrids contain large amounts of oxygen functional groups, with the phosphorus incorporation proceeding mostly through the formation of phosphate-like linkages and other functions with C-O-P bonds. The experimental findings are supported by DFT calculations, which allow the assessment of the energetics and the geometry of the interaction between phosphate groups and graphene-based models; these calculations are also used to predict the chemical shifts in the ³¹P and ¹³C NMR spectra of the models, which show good agreement with the experimentally observed solid-state NMR spectra.

Separation of CH4, H2S, N2 and CO2 gases using four types of nanoporous graphene cluster model: a quantum chemical investigation

Nanoporous graphene is being regarded as a promising candidate for reliable gas separation and purification applications. In the present research, the permeation barrier, selectivity and all thermodynamic functions for passing of four different molecules including CH₄, H₂S, N₂ and CO₂ gases on four types of porous graphene which is doped by two, three and six nitrogen atoms using quantum mechanical modelling, based on the density functional theory, B97D, and cc-pVTZ basis set have been evaluated. We find that the permeation barrier of all studied gases especially carbon dioxide decreased by considering the functionalized porous graphene by two, three and six nitrogens-doped, respectively. The results of our study propose using a porous graphene sheet as highly efficient and highly selective membranes for gas separations.

Lerf-Klinowski-type models of graphene oxide and reduced graphene oxide are robust in analyzing non-covalent functionalization with porphyrins

Graphene-based nanohybrids are good candidates for various applications. However, graphene exhibits some unwanted features such as low solubility in an aqueous solution or tendency to aggregate, limiting its potential applications. On the contrary, its derivatives, such as graphene oxide (GO) and reduced graphene oxide (RGO), have excellent properties and can be easily produced in large quantities. GO/RGO nanohybrids with porphyrins were shown to possess great potential in the field of photocatalytic hydrogen production, pollutant photodegradation, optical sensing, or drug delivery. Despite the rapid progress in experimental research on the porphyrin-graphene hybrids some fundamental questions about the structures and the interaction between components in these systems still remain open. In this work, we combine detailed experimental and theoretical studies to investigate the nature of the interaction between the GO/RGO and two metal-free porphyrins 5,10,15,20-tetrakis(4-aminophenyl) porphyrin (TAPP) and 5,10,15,20-tetrakis(4-hydroxyphenyl) porphyrin (TPPH)]. The two porphyrins form stable nanohybrids with GO/RGO support, although both porphyrins exhibited a slightly higher affinity to RGO. We validated finite, Lerf-Klinowski-type (Lerf et al. in J Phys Chem B 102:4477, 1998) structural models of GO ([Formula: see text]) and RGO ([Formula: see text]) and successfully used them in ab initio absorption spectra simulations to track back the origin of experimentally observed spectral features. We also investigated the nature of low-lying excited states with high-level wavefunction-based methods and shown that states' density becomes denser upon nanohybrid formation. The studied nanohybrids are non-emissive, and our study suggests that this is due to excited states that gain significant charge-transfer character. The presented efficient simulation protocol may ease the properties screening of new GO/RGO-nanohybrids.