DFT analysis of the adsorption of bisphenol A (BPA) on pristine and oxidized phosphorene.

CONTEXT: Bisphenol A is an endocrine disruptor that may cause harmful effects on human health. Some residues of this compound have been found in water bodies, alerting for its possible risk as an environmental pollutant. Thus, this work proposes the use of pristine and oxidized phosphorene as removers of bisphenol A, through an adsorption mechanism. Our results indicate that the main interactions exhibited by the complexes are hydrogen bonds, van der Waals, and n-π stacking. All complexes show adsorption energies less than -1.08 eV for the gas phase, and -0.65 eV for the aqueous environment, suggesting that the models may be good capturers of this pollutant. According to the electronic properties, the systems are good donators/acceptors of charge; likewise, they are suitable to sense bisphenol A, because of their changes in |LUMO-HOMO| gap energy. The values obtained suggest that the number of oxygen atoms in the models is important for their adsorption capabilities; hence, the modulation in the oxidation is significant to enhance such properties. METHODOLOGY: Density functional theory calculations were implemented at the PBE-D3/TZVP level of theory in the ORCA 5.0 program, to evaluate the adsorption of bisphenol A on pristine and oxidized phosphorene models and propose the last as removers of this molecule. The visualization of the structures was done in the VMD code.

Insights on α-Glucose Biosensors/Carriers Based on Boron-Nitride Nanomaterials from an Atomistic and Electronic Point of View.

The interaction of α-glucose with a BN-nanosheet, BN-nanotube, and BN-fullerene, was analyzed from an atomistic and electronic point of view, to evaluate such nanostructures as possible carriers and/or biosensors of the α-glucose molecule. Adsorption energies are in the range of physisorption (-0.79 eV to -0.91 eV) for the BN-nanosheet and -nanotube, and chemisorption (-2.24 eV to -2.35 eV), for the BN-fullerene. All systems, exhibit semiconductor-like behavior and great stability according to |LUMO-HOMO| energy gap [GapLH ] and chemical potential values, respectively. For the BN-nanosheet and -nanotube, the stabilization of the complexes is through hydrogen bonds, while for BN-fullerene is through a covalent bond and charge transfer. Furthermore, the BN-fullerene is able to dissociate the α-glucose molecule, which could help to decomposer such a compound, and be used for biological applications. The data taking into consideration solvent effects have no significant impact with respect to gas phase, except in the dipole moment (Md ) where we noticed an increase up to ∼45 %. Our results suggest that BN-nanosheet and -nanotube, may act as biosensors, while BN-fullerene, may serve as a carrier or degrader of the α-glucose molecule.

Functionalized graphene pieces to trap the insecticide imidacloprid: a theoretical analysis.

Eleven adducts for the interaction between imidacloprid (IMI) and some activated carbon (AC) pieces are proposed in this work. Activated carbon pieces were obtained by using a finite zig-zag graphene structure saturated with hydrogen atoms on the edges giving a pristine model with 70 carbon atoms and 22 hydrogen atoms. The zig-zag graphene structure was oxidized with -O, -COOH, -OH, and -O- groups. In this process, two identical groups were inserted over selected sites of the pristine model. All of these structures yielded ten IMI-AC adducts by using the PBE0-D3/6-31G* method, which predicts stable adducts at 0 K, and six of our models give negative free energies changes at room temperature. Thus, we expect that our IMI-AC models can be present when IMI interacts with an AC model. For one of the IMI-AC adducts, we applied solid-state techniques to avoid border effects, and we found that the imidacloprid is deprotonated giving reactive species, suggesting a new path to degrade this insecticide. Additionally, from this analysis, we proposed an additional IMI-AC adduct, which involves high free energy at room temperature. With this study, we show that our AC models can trap imidacloprid, which is quite convenient to remove this insecticide from our environment. Although it is well recognized that functionalized graphene structures are designed to trap some chemical compounds, to the best of our knowledge, this is the first time where IMI-graphene pieces interactions are studied in detail, and hydrogen bonds are analyzed through some scalar fields defined in quantum chemistry like the electron density and the non-covalent interactions index.