Ordering Mixtures of Diamagnetic and Paramagnetic Fullerenols in Aqueous Solutions in Magnetic Fields
Aqueous solutions of mixed fullerenols Gd@C82(OH)X and С82(OH)X (X = 24–30, mass fractions 30 : 70) in a magnetic field have been studied using polarized neutrons to search for molecular assembly and to test possible nuclear-magnetic cross correlations due to the presence of paramagnetic Gd atoms. The solutions were studied at ambient temperature by changing the induction B = 0.001–1.0 T and molecular content (0.04–2 wt %). Analysis of molecular correlations in a poor solution (0.04 wt %) showed coiled chain-like formations (~10^3 molecules, gyration radius of ~10 nm) integrated into massive aggregates (~10^4 molecules, radius ~50 nm). The dimensions of both structures were stable in the field (1.0 T). At a higher content (0.6–2.0 wt %), a field-induced association of the aggregates into massive chains (~10^5 molecules, gyration radius ~70 nm) was detected, but without significant nuclear-magnetic correlations. Along with fundamental interest, the results are important for the use of fullerenols as effective agents for magnetic resonance imaging.