A molecular dynamics study of the Gibbs free energy of solvation of fullerene particles in octanol and water (original) (raw)
Related papers
Journal of Chemical Sciences, 2017
The thermodynamics of association of fullerene [C 60 ] and water-soluble fullerene derivatives, i.e., fullerols [C 60 (OH) n , where, n = 2, 4, 8, 12] in aqueous solutions have been studied using molecular dynamics simulations. The potentials of mean force (PMFs) bring out the tendency of aggregation of these nanostructures in water. The extent of hydroxylation seems to have a minor effect on the depth of the contact minima (the first minimum in the PMFs). The positions of the subsequent minima and maxima in the PMFs change with the size of the solute molecules. Higher stability of the contact state of highly hydroxylated fullerols is due to the van der Waals interactions whereas intermolecular solute-solvent hydrogen bonding nearly flattens the PMFs beyond the 2nd minima for higher fullerols. The solvent contributions to the PMFs for all the solute particles studied here are positive. Entropic and enthalpic contributions to the association of solute molecules are calculated in the isothermal-isobaric (NPT) ensemble. We find that the contact pair formation is governed by entropy with the enthalpic contributions being highly unfavorable, whereas the solvent assisted and solvent separated configurations show entropy-enthalpy compensation.
Solvation properties of C60 fullerene in water-DMSO mixtures
2013
solvent mixtures present important properties that allow their use in wide field of applications. For instance, aqueous solutions of dimethyl sulfoxide have been use in biological systems due to the properties that can reach varying on the concentration of the compounds. Solvation properties in these mixtures have been explored but have never been reported investigations of solvation properties of large non polar solutes in that system. In this work, molecular dynamics simulations were employed to investigate the solvation properties of C60 fullerene immersed in water-DMSO binary mixtures. The role of DMSO as a cosolvent was studied modeling fullerene solutions varying the DMSO molar fraction from 0 to 1.0. Partial structural results showed a dense concentration of DMSO molecules around C60 at low DMSO content solutions. In high DMSO concentrations (∼ 0.70) the average number of hydrogen bonds between DMSO and water molecules and the lifetime of these interactions were smaller and higher than poor DMSO solutions, respectively. Additionally, free energy calculations were performed and an increasing hydrophobic behavior of C60 was observed in DMSO rich solutions.
Cluster solvation models of carbon nanostructures: extension to fullerenes, tubes, and buds
Journal of molecular modeling, 2014
Carbon nanobud (CNB), a hybrid material consisting of single-wall C-nanotubes (CNTs) (SWNTs) with covalently attached fullerenes, in cluster form is discussed in organic solvents. Theories are developed based on bundlet and droplet models describing size-distribution functions. Phenomena present a unified explanation in bundlet model in which free energy of CNBs involved in cluster is combined from two parts: a volume one proportional to the number of molecules n in aggregate and a surface one, to n(1/2). Bundlet model enables describing distribution function of CNB clusters by size. From purely geometrical considerations bundlet (SWNT/CNB) and droplet (fullerene) models predict dissimilar behaviors. Interaction-energy parameters of CNBs are taken from C60. A C60/SWNT in-between behavior is expected; however, properties of CNBs result closer to SWNTs. Smaller CNB clusters result less stable but greater ones are more stable than SWNT bundles. The solubility decays with temperature re...
The Journal of Chemical Physics, 2015
Fullerene C60 sub-colloidal particle with diameter ∼1 nm represents a boundary case between small and large hydrophobic solutes on the length scale of hydrophobic hydration. In the present paper, a molecular dynamics simulation is performed to investigate this complex phenomenon for bare C60 fullerene and its amphiphilic/charged derivatives, so called shape amphiphiles. Since most of the unique properties of water originate from the pattern of hydrogen bond network and its dynamics, spatial, and orientational aspects of water in solvation shells around the solute surface having hydrophilic and hydrophobic regions are analyzed. Dynamical properties such as translational-rotational mobility, reorientational correlation and occupation time correlation functions of water molecules, and diffusion coefficients are also calculated. Slower dynamics of solvent molecules—water retardation—in the vicinity of the solutes is observed. Both the topological properties of hydrogen bond pattern and ...
Journal of Nanoparticle Research
Fullerenes are sparingly soluble in many solvents. The dependence of fullerene’s solubility on molecular structure of the solvent must be understood in order to manage efficiently this class of compounds. To find such dependency ab initio quantum-chemical calculations in combination with quantitative structure–property relationship (QSPR) tool were used to model the solubility of fullerene C60 in 122 organic solvents. A genetic algorithm and multiple regression analysis (GA-MLRA) were applied to generate correlation models. The best performance is accomplished by the four-variable MLRA model with prediction coefficient r test2 = 0.903. This study reveals a correlation of highest occupied molecular orbital energy (HOMO), certain heteroatom fragments, and geometrical parameters with solubility. Several other important parameters of solvents that affect the C60 solubility have been also evaluated by the QSPR analysis. The employed GA-MLRA approach enhanced by application of quantum-chemical calculations yields reliable results, allowing one to build simple, interpretable models that can be used for predictions of C60 solubility in various organic solvents.
Brazilian Journal of Physics, 2008
This work aim is to determine how a C 60 fullerene, encapsulated into a (10,10) carbon nanotube, can be ballistically expelled from it by using a colliding capsule. Initially, the C 60 fullerene is positioned at rest inside the nanotube. The capsule, also starting from rest but outside of the nanotube, is put in a position such that it can be trapped towards the interior of the nanotube by attraction forces between their atoms. The energy gain associated to the capsule penetration is kinetic energy, giving rise to a high velocity for it. When the capsule reaches the C 60 fullerene, it transfers energy to it in an amount that enables the fullerene to escape from the nanotube. The mechanical behavior was simulated by classical molecular dynamics. The intermolecular interactions are described by a van der Waals potential while the intramolecular interactions are described by an empirical Tersoff-Brenner potential for the carbon system.
Hydrophobic hydration of C60 and carbon nanotubes in water
Carbon, 2004
We perform molecular dynamics (MD) simulations to study the hydrophobic-hydrophilic behavior of pairs of C 60 fullerene molecules and single wall carbon nanotubes in water. The interaction potentials involve a fully atomistic description of the fullerenes or carbon nanotubes and the water is modeled using the flexible SPC model. Both unconstrained and constrained MD simulations are carried out. We find that these systems display drying, as evidenced by expulsion of the interstitial water, when the C 60 and carbon nanotubes are separated by less than 12, and 9-10 A, respectively. From the constrained simulations, the computed mean force between two carbon nanotubes in water exhibits a maximum at a tube spacing of 5.0 A which corresponds to approximately one unstable layer of interstitial water molecules. The main contribution to the force stems from the van der Waals attraction between the carbon surfaces. The minimum in the potential of mean force has a value of)17 kJ mol À1 A À1 at a tube spacing of 3.5 A.
Molecular Dynamics Simulation of Fullerene C 60 in Ethanol Solution
The Journal of Physical Chemistry C, 2009
An ethanol solution containing one or two fullerene C 60 molecules was studied via molecular dynamics simulation. We found that the ethanol molecules form several solvation shells around the central fullerene molecule. Radial distribution functions (RDFs) and hydrogen-bond analyses were employed to detect the structure of the ethanol molecules in the solvation shells. The ethanol molecules in the first solvation shell tend to have their nonpolar alkyl groups exposed to the C 60 surface while the polar hydroxyl groups point outward to maintain a hydrogen-bond network with a clathrate-like structure. Such orientation of the ethanol molecules in the first solvation shell modulates the orientation of the ethanol molecules in the second solvation shell to have the hydroxyl groups pointing inward. The potential of mean force (PMF) between two C 60 molecules in ethanol solution showed that C 60 molecules tend to aggregate in the ethanol solution. There is no ethanol molecule in the intersolute area if the distance between the centers of mass of two C 60 molecules is shorter than 10.2 Å. The ethanol molecules near the intersolute area tend to have their methyl groups penetrating into the intersolute region if the distance between two C 60 molecules is short, although the hydroxyl groups have smaller volume. We analyzed the dynamic properties of the ethanol molecules in different solvation shells and found that the relaxation is much slower than that of water solution of C 60 molecules. In addition, the relaxation of the first solvation shell is slower than that in other solvation shells. The lifetime of the hydrogen-bond in the first solvation shell is also longer than that in other solvation shells while the reorientation of the hydrogen-bonded ethanol pair contributes little to break the hydrogen-bonds.
The Journal of Chemical Physics, 2017
Molecular dynamics simulations of fullerene and fullerols [C 60 (OH) n , where n = 2-30] in aqueous solutions have been performed for the purpose of obtaining a detailed understanding of the structural and dynamic properties of these nanoparticles in water. The structures, dynamics and hydration free energies of the solute molecules in water have been analysed. Radial distribution functions, spatial density distribution functions and hydrogen bond analyses are employed to characterize the solvation shells of water around the central solute molecules. We have found that water molecules form two solvation shells around the central solute molecule. Hydrogen bonding in the bulk solvent is unaffected by increasing n. The large decrease in solvation enthalpies of these solute molecules for n > 14 enhances solubilisation. The diffusion constants of solute molecules decrease with increasing n. The solvation free energy of C 60 in water is positive (52.8 kJ/mol), whereas its value for C 60 (OH) 30 is highly negative (427.1 kJ/mol). The effects of surface hydroxylation become more dominant once the fullerols become soluble.