Aggregation of Fullerene, C₆₀, in Benzonitrile

Abstract

C 60 solutions in benzonitrile have been found to show concentration dependent optical absorption behaviour. At lower concentrations (<100 µM) the UV-vis absorption characteristics of C 60 in benzonitrile are exactly similar to those in benzene and decalin. At higher concentrations (>100 µM), however, the C 60 solutions in benzonitrile show very broad absorption tail, extending beyond 900 nm. At higher concentrations the solutions are also visually opaque. From picosecond laser flash photolysis experiments it is seen that the triplet quantum yield of C 60 in benzonitrile at higher concentrations (∼400 µM) is much less than unity and increases with the dilution while in decalin and benzene it is always close to unity and independent of the C 60 concentration. Dynamic light scattering experiments indicate the presence of particles of mean size of about 250 nm in C 60 solutions in benzonitrile with concentration >100 µM, while in <100 µM solutions no such particles have been observed. Such particles are also not observed for C 60 solutions in benzene and decalin, even up to ∼500 µM. Scanning electron microscopy also shows particles of size ∼250 nm. It is inferred that C 60 forms aggregates in benzonitrile at concentrations >100 µM and that the aggregated and the monomeric form of C 60 are in equilibrium.

Solvent-induced optical properties of C60

“…5A, with the increasing volume ratio of acetonitrile, a yellow-green band at 570 nm comes into sight and rises gradually at expense of the strong purple-blue band at 440 nm; this corresponds well to that a broad absorption band turns out in 440-480 nm range with a decrease and final extinguishment of the narrow absorption peak at 407 nm (see the right inset in Fig. 5A), which has been also observed by other works [25][26][27][28][29][30]; simultaneously, compared with the C 60 /toluene dispersion (displayed in Fig. 2B), well-dispersed C 60 nanoparticles can be found assembling with each other into clusters during our mixing toluene with acetonitrile (see the TEM image in Fig.…”

Solvent‐Polarity‐Tunable Dimeric Association of a Fullerene (C60)–N,N‐Dimethylaminoazobenzene Dyad: Modulated Electronic Coupling of the Azo Chromophore with a Substituted 3D Fullerene

“…The 3D spatial orientation along with the bulk of the electronic cloud placed above the alternate double and single bonds, and an electron-deficient core have been the main reasons for fullerene aggregation in single and binary solvents. [123][124][125] This characteristic electron density distribution has prevailed even for functionalized fullerene derivatives towards aggregate formation and structures of varying size and dimensions, thereby emphasizing the electronic and van der Waals interactions between the neighboring molecules.…”

Lattice model of living polymerization. II. Interplay between polymerization and phase stability

“…It is encouraging that the phase separation phenomenology of real associating polymer systems ͑living linear polymers, thermally reversible gels, micelle solutions͒ exhibits such common features, suggesting that the Florytype lattice model correctly captures the zeroth order physics of these associating polymer systems. We may then anticipate that many generic phase separation properties of living polymer solutions, illustrated in the present paper, also have relevance for other types of associating systems-associating colloid particles in solution, [50][51][52][53] biologically relevant structures formed through aggregation, protein aggregation, etc., although specific details may differ. Apparently associating polymers and systems aggregating at equilibrium, in general, share many thermodynamic features in common and exhibit similar patterns of phase stability.…”