Aggregation of C₇₀ in Solvent Mixtures

Abstract

The unusual solvatochromism of C70 is investigated in a variety of solvent mixtures by optical absorption and fluorescence techniques. Distinct reversible color change from pink to purple is seen in the solvent mixtures studied. Such changes are seen also for C60 solutions in some solvent mixtures. Formation of clusters is found to be responsible for the observed optical changes. Light scattering studies are carried out to confirm the presence of clusters which show that the particle size varies from ∼100 to ∼1000 nm depending on the concentration of the fullerene. It is found that the solubility of the fullerene in the solubilizing solvent and that in the solvent mixtures are the major factors governing the aggregation behavior of the fullerene. Polarity of the solvent plays a minor role in the formation of aggregates.

Towards better understanding of C60organosols

“…One of the specific features of fullerenes is their ability to form aggregates. [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.…”

“…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. 8,10,11,14,[36][37][38][39][40] Some authors believe that in such a case, aggregates appear only as a result of sonication.…”

“…8,38,41 In contrast, in polar or 'poor' organic solvents, the formation of colloidal species is undoubtedly proven. 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.…”

Model for reversible nanoparticle assembly in a polymer matrix

“…For example, fullerene particles have been observed to form different types of clusters, depending on the solvent in which the fullerenes are dispersed. 59,60 The solvent has also been found to play an important role in the supramolecular assembly of conjugated molecules into nanofibers. 61 The interaction of nanoparticles with biological materials is an important situation where this effect arises.…”

Structure-function relationships of fullerene esters in polymer solar cells: unexpected structural effects on lifetime and efficiency

“…1). PCBM, a functionalized C 60 , is used to improve solubility since the unmodified version tends to form clusters and aggregates [17][18][19][20][21].…”