Solvent Polarity Considerations Are Unable to Describe Fullerene Solvation Behavior

Different agglomeration properties of PC61BM and PC71BM in photovoltaic inks – a spin-echo SANS study

Fullerene derivatives are used in a wide range of applications including as electron acceptors in solution-processable organic photovoltaics.

C60 additive-assisted crystallization in CH3NH3Pb0.75Sn0.25I3 perovskite solar cells with high stability and efficiency

The development of hybrid tin (Sn)-lead (Pb) perovskite solar cells likely tackles the toxic problem with the power conversion efficiency (PCE) exceeding 17%. However, the stability problems, e.g. hysteresis effect, degeneration and oxidation, appear to be the bottleneck that limit its further development. Here, we innovatively introduced C₆₀ at the grain boundaries throughout the CH₃NH₃Pb_0.75Sn_0.25I₃ (MAPb_0.75Sn_0.25I₃) thin film, playing a role not only in in situ passivating the interfaces and reducing the pinholes of perovskite thin films, but also in preventing the penetration of moisture and oxygen from ambient atmosphere. Electrochemical impedance spectroscopy (EIS) illustrated that the recombination lifetime of both the bulk and surface of MAPb_0.75Sn_0.25I₃ thin films was increased by additive incorporation of C₆₀. Dark I-V results for the electron/hole-only devices showed that the charge trap-state density decreased with C₆₀ additive incorporated into the hybrid Sn-Pb perovskite thin films. Importantly, the hybrid Sn-Pb perovskite solar cells modified with C₆₀ additive were demonstrated to have superior stability and efficiency when exposed to the ambient environment without encapsulation.

Thermodynamics of hydration of fullerols [C60(OH)n] and hydrogen bond dynamics in their hydration shells

Molecular dynamics simulations of fullerene and fullerols [C₆₀(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 C₆₀ in water is positive (52.8 kJ/mol), whereas its value for C₆₀(OH)₃₀ is highly negative (-427.1 kJ/mol). The effects of surface hydroxylation become more dominant once the fullerols become soluble.

Fullerenes in Aromatic Solvents: Correlation between Solvation-Shell Structure, Solvate Formation, and Solubility

In this work, an all-atom molecular dynamics simulation technique was employed to gain insight into the dynamic structure of the solvation shell formed around C60 and phenyl-C61-butyric acid methyl ester (PCBM) in nine aromatic solvents. A new method was developed to visualize and quantify the distribution of solvent molecule orientations in the solvation shell. A strong positive correlation was found between the regularity of solvent molecule orientations in the solvation shell and the experimentally obtained solubility limits for both C60 and PCBM. This correlation was extended to predict a solubility of 36 g/L for PCBM in 1,2,4-trimethylbenze. The relationship between solvation-shell structure and solubility provided detailed insight into solvate formation of C60 and solvation in relation to solvent molecular structure and properties. The determined dependence of the solvation-shell structure on the geometric shape of the solvent might allow for enhanced control of fullerene solution-phase behavior during processing by chemically tailoring the solvent molecular structure, potentially diminishing the need for costly and environmentally harmful halogenated solvents and/or additives.

Polypeptide A9K at nanoscale carbon: a simulation study

The amphiphilic nature of surfactant-like peptides is responsible for their propensity to aggregate at the nanoscale.

Strong electronic polarization of the C60 fullerene by imidazolium-based ionic liquids: accurate insights from Born–Oppenheimer molecular dynamic simulations

Fullerenes are known to be polarizable due to their strained carbon–carbon bonds and high surface curvature.

Assessing the hydration free energy of a homologous series of polyols with classical and quantum mechanical solvation models

Molecular dynamics (MD) simulations associated with the thermodynamic integration (TI) scheme and the polarizable continuum model (PCM) in combination with the SMD solvation model were used to study the hydration free energy of the homologous series of polyols, C(n)H(n+2)(OH)n (1 ≤ n ≤ 7). Both solvation models predict a nonlinear behavior for the hydration free energy with the increase of the number of hydroxyl groups. This study also indicates that there is a sizable solute polarization in aqueous solution and that the inclusion of the polarization effect is important for a reliable description of the free energy differences considered here.

Dynamic solvation shell and solubility of C60 in organic solvents

The notion of (static) solvation shells has recently proved fruitful in revealing key molecular factors that dictate the solubility and aggregation properties of fullerene species in polar or ionic solvent media. Using molecular dynamics schemes with carefully evaluated force fields, we have scrutinized both the static and the dynamic features of the solvation shells of single C60 particle for three nonpolar organic solvents (i.e., chloroform, toluene, and chlorobenzene) and a range of system temperatures (i.e., T = 250-330 K). The central findings have been that, while the static structures of the solvation shell remain, in general, insensitive to the effects of changing solvent type or system temperature, the dynamic behavior of solvent molecules within the shell exhibits prominent dependence on both factors. Detailed analyses led us to propose the notion of dynamically stable solvation shell, effectiveness of which can be characterized by a new physical parameter defined as the ratio of two fundamental time constants representing, respectively, the solvent relaxation (or residence) time within the first solvation shell and the characteristic time required for the fullerene particle to diffuse a distance comparable to the shell thickness. We show that, for the five (two from the literature) different solvent media and the range of system temperatures examined herein, this parameter bears a value around unity and, in particular, correlates intimately with known trends of solubility for C60 solutions. We also provide evidence revealing that, in addition to fullerene-solvent interactions, solvent-solvent interactions play an important role, too, in shaping the dynamic solvation shell, as implied by recent experimental trends.

Imidazolium Ionic Liquid Helps to Disperse Fullerenes in Water

Light fullerenes attract significant interest in pharmacy and medicine as drug vectors and antioxidants and to block AIDS virus enzyme. The progress of these applications is hindered by poor solubility of fullerenes in aqueous media. We propose a highly efficient hydrophilic system to disperse the C60 fullerene based on the accurate atomistic-resolution computer simulations. The introduced system is based on 1-butyl-3-methylimidazolium tetrafluoroborate, [C4C1IM][BF4]-water mixtures. The first component is used to form a corona around C60 while exhibiting a significant miscibility with water. Structural and dynamical peculiarities of the C60-[C4C1IM][BF4]-water mixtures are discussed.

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].