Fullerene C₆₀: Surface Energy and Interfacial Interactions in Aqueous Systems

Abstract

The underlying mechanisms of fullerene-fullerene, fullerene-water, and fullerene-soil surface interactions in aqueous systems are not well understood. To advance our understanding of these interfacial interactions, the surface properties of Buckminsterfullerene (C60) and quartz surfaces were investigated. From application of the van Oss-Chaudhury-Good model and the Young-Dupre equation, the Lifshitz-van der Waals, acid-base, and the total surface energies of C60 powder and quartz surfaces were calculated from contact angle measurements using the sessile drop technique. C60 powder measurements indicate low to medium energy surfaces of 41.7 mJ/m2 with a dominant Lifshitz-van der Waals component. In aqueous systems, hydrophobic attraction due to the high cohesion of water is the driving force for C60 aggregation. The high free energy of hydration (DeltaG(pw)(total) = -90.5 mJ/m2) indicates the high affinity of C60 particles for water. Hamaker constants of 4.02 x 10(-21) J (A(pwp)) and 2.59 x 10(-21) J (A(pws)) were derived for C60-C60 and C60-quartz interactions in aqueous systems. The results of this study indicate that surface energy is an important physical parameter that should be considered as a basic characterization property of fullerene nanomaterials.

Towards better understanding of C60organosols

“…The numerous and sometimes conflicting results of experimental 5,14,[16][17][18][19][20][21][22][23][24][25][43][44][45][46][47][48][49] and theoretical [73][74][75][76][77][78][79] investigations demand such a comparison. Indeed, the theoretical calculations often predict strong interaction between C 60 and water (as a recent example, the work by Choi et al 77 may be proposed), which may be considered as a type of expressed hydration, whereas the coagulation data indicate the hydrophobic nature of the fullerene hydrosols.…”

“…On the other hand, there are two diametrically opposite estimates of the Hamaker constant of fullerene-fullerene interaction, A FF , in vacuum: A FF = (6.5, or 7.5, or 8.5) Â 10 À20 J 14,18,19,21 and 50 Â 10 À20 J. 16,17 The first one was obtained from the CCC values of the hydrosol, whereas the second value originates from the data for carbon nanotubes.…”

“…[8][9][10][11][12][13][14] While in low-polar aromatic solvents, fullerenes are well solvated and relatively well dissolved, 14,15 in water they generate hydrosols and suspensions. 5,11,[16][17][18][19][20][21][22][23][24][25][26][27][28][29][30] In highly polar organic solvents, the molecular solubility of fullerenes is negligible, 14,15 but they readily form colloidal solutions. [9][10][11][12][13][14][31][32][33][34][35] The state of fullerenes, either molecular or colloidal, in the so-called 'good' or 'strong' solvents, such as CS 2 , toluene, and benzene, is still a matter of discussion.…”

“…9,[11][12][13][14][31][32][33][34][35] Typical examples are aggregates in N-methylpyrrolidin-2-one-acetonitrile mixed solvent, 3 toluene (benzene) mixtures with acetonitrile, 9,12,36 N-methylpyrrolidin-2-one 11,33 and other polar solvents, 13 DMSO, 31 acetonitrile, acetone, ethanol, methanol, and other polar solvents. 32,35,42 Though the stability and coagulation of aqueous C 60 colloids via electrolytes has been examined in full, 14,[16][17][18][19][20][21][22][23][24][25][26][27][28][29][43][44][45][46][47][48][49] the corresponding research for organosols is absent to the best of the authors knowledge. Despite numerous publications describing the preparation procedure, particle size and other properties, the coagulation by electrolytes and the origin of the charge of colloidal species in organic solvents yet stays almost unexplored.…”

Tunable tribological properties in water-based lubrication of water-soluble fullerene derivatives via varying terminal groups

“…The discovery [1] and large scale preparation [2] of fullerene C 60 are one of the most important achievements in the 20th century. Since then, much attention has been paid to fullerene C 60 for its potential applications in physics, chemistry and material science [3][4][5][6][7][8][9][10]. The lubricating properties of fullerene C 60 [1,11] have been predicted because of its unique spherical shape, high load-bearing capacity, strong intramolecular forces, weak intermolecular forces, low surface energy and so on.…”