Spectroscopic and Photophysical Properties of a Highly Derivatized C₆₀ Fullerol

Abstract

Hydroxylated C60 molecules, also called fullerols, are a class of water‐soluble fullerenes. Here we report the synthesis in acidic conditions of a highly derivatized fullerol (up to 36 carbons per C60 are oxidized). Spectroscopic investigations (X‐ray photoelectron spectroscopy and infrared absorption) highlight the coexistence of both acidic and basic forms for the hydroxyl addends of derivatized C60. pH titrimetry reveals that, at millimolar concentrations, only ten protons per fullerol molecule are labile. Such a low value, as compared to 36 hydroxyl groups, is explained by the formation of clusters. A UV‐vis absorption study performed over a large range of concentrations also points to the aggregation phenomenon. Moreover, this study shows that the clusters of fullerols appear at relatively low (micromolar) concentrations. An electron spin resonance (ESR) study, based on the attack of singlet oxygen (1Δg) on 2,2,6,6‐tetramethyl‐4‐piperidinol (TMP‐OH), has proved the potential of hydroxylated C60 for performing efficient generation of singlet oxygen in aqueous solution. ESR measurements, which allow detection and quantification of 1Δg, have also revealed the generation of reactive oxygen species (ROS). The yield of generation of 1Δg and ROS is strongly correlated to the concentration of fullerol, thus also pointing to the aggregation of fullerol molecules. Exposing glioblastoma cells to oxidative stress in the presence of hydroxylated C60 and visible light has also been performed. Atomic force microscopy is used to monitor the relevant diminishment of the Young's modulus values for cells exposed to the oxidative stress. These results point to a possible application field of fullerols for performing bio‐oxidations.

Gd-metallofullerenol nanomaterial as non-toxic breast cancer stem cell-specific inhibitor

“…When dissolved in aqueous solution, they form nanoparticles as polyanion nano-aggregates, and the nanoparticle size is reduced in more acidic solution [40][41][42] . It was reported that the smaller sized nanoparticles may allow deeper penetration into tumour tissues 43 .…”

“…The Gd@C 82 (OH) 22 cage surface has both attractive (C-OH) and repulsive (C-O À ) sites. Hence, the acidic protons are involved in attractive hydrogen bonding interactions with other Gd@C 82 (OH) 22 molecules and this constitutes a driving force of nanoparticle formation 40 . Our measurement of its nanoparticle formation at the different pH solutions indicates that at pH 4.3 solution, the average size of Gd@C 82 (OH) 22 nanoparticles is B40 nm, at pH 5.1, B116 nm and at pH 7.4, B175 nm.…”

Pristine (C60) and Hydroxylated [C60(OH)24] Fullerene Phototoxicity towards HaCaT Keratinocytes: Type I vs Type II Mechanisms

“…Both of these fullerenes are readily soluble in water. However, it has been reported that some functionalized fullerenes may form aggregates in polar media at high concentrations (31,(42)(43)(44)(45). To verify the formation of aggregates, UV-visible absorption spectra of different concentrations of (γ-CyD) 2 /C 60 and C 60 (OH) 24 in aqueous solution were recorded.…”

“…C 60 can also be solubilized in water by using γ-cyclodextrin (γ-CyD) as a host to form a complex wherein the C 60 is encapsulated between the cavities of two γ-CyD molecules (28)(29)(30). Aqueous solubility can also be achieved by chemically modifying or functionalizing the C 60 surface with hydrophilic substituents, such as hydroxyl (31), carboxyl (32), quaternary ammonium (33), diamido diacid diphenyl (34), or poly(ethylene glycol) (35) groups.…”

Preparation and characterization of a polycaprolactone/C60 composite and its improved counterpart (PCLNH2/C60OH)

“…6,7 Of particular interest is the use of C 60 in polymer/C 60 composites, 8,9 as reports indicate that matrix properties can be effectively enhanced via its addition. 10,11 However, aggregation and nonuniform dispersion of C 60 filler in common polymer matrix can be an issue, and therefore two primary conditions are required for the application of C 60 composites: the homogeneous dispersion of C 60 in the host matrix and appropriate interfacial interaction. Recently, various methods have been introduced for functionalizing C 60 to improve its compatibility with monomers and polymers.…”