The interaction of the noble atoms (Ar and Xe) with single-walled carbon nanotube (SWCNT) bundles are investigated using Raman spectroscopy in conjunction with computational modeling known as ReaxFF force field. SWCNT bundles were deposited on transmission electron microscopy (TEM) grids, and different noble gases were adsorbed onto the nanotubes at 20 K. Raman spectra acquired show significant frequency blueshifts of the radial breathing mode (RBM), G-and G 0 (or 2D)-bands due to gas solidification within the external groove sites (free spaces between the tubes in the bundle) and external surfaces of the bundles. This solid shell formed by the adsorbed gases contributes with a hydrostatic pressure to the system. We show from Raman measurements that the frequencies found after gas adsorption exhibit almost the same shifts indicating that the interactions between SWCNTs bundles and the gases (Ar or Xe) are nearly identical.

In this work, the efficiency of partially hydrophobized hyperbranched polyglycerols (HPG11 and HPG12) as cetyltrimethylammonium bromide (CTAB) carriers was evaluated to prevent surfactant losses by adsorption on reservoir rocks surface during enhanced oil recovery (EOR) processes. Interactions between surfactant and polymers were studied by conductivity, zeta potential, and particle size measurements showing that complexes were formed between the components. The ability of PG, HPG11, HPG12 and those complexes to reduce the interfacial tension (IFT) was verified and one of the complexes was able to reduce the IFT to values under 1.0 mN/m, suggesting the occurrence of a synergy between the components. Molecular dynamics simulations indicated the preferential sites of interaction between surfactants and HPGs. HPG11:CTAB and HPG12:CTAB complexes' ability to permeate an unconsolidated porous medium and deliver the surfactant at the water–oil interface, increasing oil production, was evaluated through transport and oil displacement tests, and the results showed that the HPG12:CTAB complex led to almost 90% of oil recovery.

Naphthenic Acids (NA) are important oil extraction subproducts. These chemical species are one of the leading causes of marine pollution and duct corrosion. For this reason, understanding the behavior of NAs in different saline conditions is one of the challenges in the oil industry. In this work, we simulated several naphthenic acid species and their mixtures, employing density functional theory calculations with the MST-IEFPCM continuum solvation model, to obtain the octanol–water partition coefficients, together with microsecond classical molecular dynamics. The latter consisted of pure water, low-salinity, and high-salinity environment simulations, to assess the stability of NAs aggregates and their sizes. The quantum calculations have shown that the longer chain acids are more hydrophobic, and the classical simulations corroborated: that the longer the chain, the higher the order of the aggregate. In addition, we observed that larger aggregates are stable at higher salinities for all the studied NAs. This can be one factor in the observed low-salinity-enhanced oil recovery, which is a complex phenomenon. The simulations also show that stabilizing the aggregates induced by the salinity involves a direct interplay of Na+ cations with the carboxylic groups of the NAs inside the aggregates. In some cases, the ion/NA organization forms a membrane-like circular structural arrangement, especially for longer chain NAs.

The interactions of adsorbates with graphene have received increasing attention due to its importance in the development of applications involving graphene-based coatings. Here, we present a study of the adsorption of noble gases on pristine and nitrogen-doped graphene. Single-layer graphene samples were synthesized by chemical vapor deposition (CVD) and transferred to transmission electron microscopy (TEM) grids. Several noble gases were allowed to adsorb on the suspended graphene substrate at very low temperatures. Raman spectra show distinct frequency blue shifts in both the 2Dand G-bands, which are induced by gas adsorption onto high quality single layer graphene (1LG). These shifts, which we associate with compressive biaxial strain in the graphene layers induced by the noble gases, are negligible for nitrogen-doped graphene. Additionally, a thermal depinning transition, which is related to the desorption of a noble gas layer from the graphene surface at low temperatures (ranging from 20 to 35K), was also observed at different transition temperatures for different noble gases. These transition temperatures were found to be 25K for Argon and 35K for Xenon. Moreover, we were able to obtain values for the compressive biaxial strain in graphene induced by the adsorbed layer of noble gases, using Raman spectroscopy. Ab initio calculations confirmed the correlation between the noble gas-induced strain and the changes in the Raman features observed.