Evaluating quantum entanglement generation in two-dimensional graphene systems through lithium ion interactions: A DFT-based study.

In this article, we employed concepts from Density Functional Theory to investigate the interaction energy behavior between the fragments of two-dimensional systems composed of graphene-based materials and lithium ions. Specifically, the proposed system consists of two graphene sheets separated by a controlled distance (face-to-face), with a lithium ion positioned at the center of this separation. Additionally, we examined potential electronic transitions within these systems and assessed the feasibility of quantum entanglement generation and manipulation. Our findings revealed that the interaction energies within the analyzed systems exhibited behavior akin to that described by the Lennard-Jones potential, which characterizes systems with favorable energy for their formation. The results further yielded estimates for the constants ϵ and σ , with values of - 66 . 59  kcal/mol and 1.63  Å , respectively. Specific electronic transitions were identified, suggesting the potential for quantum entanglement generation and manipulation among the two-dimensional graphene system mediated by the lithium ion interactions.

Polar Zipper on a Peptide Nanomembrane: A Characterization by Potential of Mean Force.

In this work, nanomembranes formed by the I3XGK (X = Q, S, or N) polar peptides are studied to characterize the average force and energy required to separate two neighboring ß-sheets laterally joined by polar zippers. The results presented are obtained using a methodology (state of the art) involving the pulling umbrella method to generate the samples (umbrella sampling) and the potential of mean force (PMF) to evaluate the energetic variation evolved in the process of separating the polar zipper. It was observed that the maximum force required to separate the regions linked by polar zippers is 1.48 kJ/mol nm for the I3NGK nanomembrane and 1.22 kJ/mol nm [1.30 kJ/mol nm] for the I3QGK [I3SGK] nanomembranes, emphasizing that polar zippers play an important role in the interaction that interconnects ß-sheets in broad and robust two-dimensional structures (tapes and membranes), offering an agile route to the construction of distinct nanomaterials from ß-sheets. Also, negative values were obtained for energy as a function of the reaction coordinate for the regions where the formation of polar zippers occurs, showing that the lateral union of neighboring ß-sheets is energetically favorable, with a value up to -3.0 kJ/mol, in the case of I3NGK nanomembranes.

Updating atomic charge parameters of aliphatic amino acids: a quest to improve the performance of molecular modeling via sequential molecular dynamics and DFT-GIAO-NMR calculations.

In this work, we observe the behavior of the dipole moment, atomic charges, solute-solvent interactions and NMR spectroscopy of aliphatic amino acids in a water solution via the computational simulations of classical molecular dynamics and DFT quantum calculations. Our results indicate that the convergence of the atomic charge of the solute, from an iterative process, together with the dipole moment of the amino acid, alters the lifetime of hydrogen bonds present in the first solvation shell, resulting in the modification of its structure and dynamics. Using GIAO-DFT-NMR calculations, we assessed the impact of these structural solute-solvent modifications on the magnetic shielding constants of the solute carbon atoms. In this sense, we evaluate the importance of an update in parameters that describe atomic charges present in the CHARMM36 force field.

Molecular dynamic simulations, GIAO-NMR and TD-DFT spectroscopy analyze for zwitterionic isoleucine (ILE)N , 1 ≤ N ≤ 6, in water solution.

In this article, we investigate the effects of the isoleucine (ILE)N amino acid chain growth, N = 1.0.6, the ILE conformational effect as well as the solvent presence on the electrical and magnetic spectroscopic properties when these compounds are in aqueous solution. Computational molecular dynamics simulations were performed to include the solvent medium and generate uncorrelated configurations involving solute-solvent structures. The charge point model for solvent was used to obtain the results for quantum mechanical calculation, in special DFT calculations, for (ILE)N structures. Our results for the magnetic shielding constant obtained via GIAO-DFT-NMR calculations show that there is evidence of a magnetic behavior that characterizes the number of peptide bonds and, therefore, how the N isoleucine polypeptide chain is composed. TD-DFT results also show an absorption band shift to larger wavelengths indicating a dependence on N growth.

Investigating the asymmetry in the EDL response of C60/graphene supercapacitors.

Development of efficient electrodes is one of the main ways to increase the performance of an electrochemical energy storage device. It is known that such performance is associated with the electrode specific area, which allows a much larger interfacial interaction with the electrolyte. In this work, molecular dynamics is employed to model C60/graphene composite electrodes that can expand the effective area by approximately 70% relative to a pure graphene electrode. Our simulations indicate that the performance of supercapacitors of C60/graphene electrodes is superior to those made of planar graphene, in some cases up to 150%. The inherent electrolyte asymmetry in the investigated supercapacitors has a negative effect on the total capacitance, indicating that even better results could be obtained after rational design of the fullerene density on the surface of the graphene as well as the choice of the ions in the liquid ionic composition.

Robust Entanglement Generation in Lithium Ions Mediated by Graphene Quantum Dots Interaction.

In this work, we propose and investigate numerically the electronic transitions of a new system useful for quantum information tasks composed by a graphene quantum dot (GQD) interacting with two Li+ ions in opposed facing directions. By changing the distance of the Li+ ions, we find a region in which only electronic transitions of GQD → Li+ are allowed. Notably, into this region emerges the possibility of controlled electronic transitions for both ions in the symmetric case via appropriate external electric fields. Finally, the robust entanglement generation arises since it is possible to inhibit the electronic transition back to GQD by grounding it.

Storing Energy in Biodegradable Electrochemical Supercapacitors.

The development of green and biodegradable electrical components is one of the main fronts of research to overcome the growing ecological problem related to the issue of electronic waste. At the same time, such devices are highly desirable in biomedical applications such as integrated bioelectronics, for which biocompatibility is also required. Supercapacitors for storage of electrochemical energy, designed only with biodegradable organic matter would contemplate both aspects, that is, they would be ecologically harmless after their service lifetime and would be an important component for applications in biomedical engineering. By means of atomistic simulations of molecular dynamics, we propose a supercapacitor whose electrodes are formed exclusively by self-organizing peptides and whose electrolyte is a green amino acid ionic liquid. Our results indicate that this supercapacitor has a high potential for energy storage with superior performance than conventional supercapacitors. In particular its capacity to store energy was estimated to be almost 20 times greater than an analogue one of planar metallic electrodes.

GIAO-DFT-NMR characterization of fullerene-cucurbituril complex: the effects of the C60@CB[9] host-guest mutual interactions.

Magnetic shielding constants for an isolated fullerene C60, cucurbituril CB[9], and the host-guest complex C60@CB[9] were calculated as a function of separation of the monomers. Our results in the gas phase and water indicate a significant variation of the magnetic properties for all atoms of the monomers in the complex and after liberation of fullerene C60 from the interior of the CB[9] cavity. The interaction between the two monomers results in a charge transfer that collaborates with a redistribution of electron density to deshield the monomers. Graphical Abstract NMR spectroscopy alteration on C60@CB[9] host-guest mutual interactionsᅟ.

The Band Gap of Graphene Is Efficiently Tuned by Monovalent Ions.

Small monovalent ions are able to polarize carbonaceous nanostructures significantly. We report a systematic investigation of how monovalent and divalent ions influence valence electronic structure of graphene. Pure density functional theory is employed to compute electronic energy levels. We show that the lowest unoccupied molecular orbital (LUMO) of an alkali ion (Li(+), Na(+)) fits between the highest occupied molecular orbital (HOMO) and LUMO of graphene, in such a way as to tune the bottom of the conduction band (i.e., band gap). In turn, Mg(2+) shares its orbitals with graphene. The corresponding binding energy is ca. 4 times higher than that in the case of alkali ions. The reported insights provide inspiration for engineering electrical properties of the graphene-containing systems.

Can inorganic salts tune electronic properties of graphene quantum dots?

Electronic properties of graphene quantum dots (GQDs) constitute a subject of intense scientific interest. Being smaller than 20 nm, GQDs contain confined excitons in all dimensions simultaneously. GQDs feature a non-zero band gap and luminescence on excitation. Tuning their electronic structure is an attractive goal with technological promise. In this work, we apply density functional theory to study the effect of neutral ionic clusters adsorbed on the GQD surface. We conclude that both the HOMO and the LUMO of GQDs are very sensitive to the presence of ions and to their distance from the GQD surface. However, the alteration of the band gap itself is modest, as opposed to the case of free ions (recent reports). Our work fosters progress in modulating electronic properties of nanoscale carbonaceous materials.

Molecular dynamics study of surfactant-like peptide based nanostructures.

Surfactant-like peptide (SLP) based nanostructures are investigated using all-atomistic molecular dynamics (MD) simulations. We report structure properties of nanostructures belonging to the ANK peptide group. In particular, the mathematical models for the two A3K membranes, A6K nanotube, and A9K nanorod were developed. Our MD simulation results are consistent with the experimental data, indicating that A3K membranes are stable in two different configurations: (1) SLPs are tilted relative to the normal membrane plane; (2) SLPs are interdigitated. The former configuration is energetically more stable. The cylindrical nanostructures feature a certain order of the A6K peptides. In turn, the A9K nanorod does not exhibit any long-range ordering. Both nanotube and nanorod structure contain large amounts of water inside. Consequently, these nanostructures behave similar to hydrogels. This property may be important in the context of biotechnology. Binding energy analysis-in terms of Coulomb and van der Waals contributions-unveils an increase as the peptide size increases. The electrostatic interaction constitutes 70-75% of the noncovalent attraction energy between SLPs. The nanotubular structures are notably stable, confirming that A6K peptides preferentially form nanotubes and A9K peptides preferentially form nanorods.

Predicting the properties of a new class of host-guest complexes: C60 fullerene and CB[9] cucurbituril.

DFT, semi-empirical and classical molecular dynamics methods were used to describe the structure and stability of the inclusion complex formed by the fullerene C60 and the cucurbituril CB[9]. Our results indicate a high structural compatibility between the two monomers, which is evident from the potential energy curve for the inclusion process of the C60 into the CB[9] cavity. The interaction between the two monomers is mainly of the van der Waals type and leads to a highly stable complex. Thermal contributions and environmental interaction are taken into account by the free energy of binding of -224 kJ mol(-1), indicating that even in aqueous medium the complex remains very stable.