Periodical Variation of Electronic Properties in Polyhydroxylated Metallofullerene Materials

Abstract

Endohedral metallofullerenes (fullerenes with metal atom(s) encapsulated), as a novel form of carbon-related materials, [1] have attracted special attention for their potential applications [2][3][4][5][6][7][8][9][10] in electronic devices, [2,3] biomedical fields such as therapeutic medicine, [4,5] and a new generation of magnetic resonance imaging (MRI) contrast agents, [6][7][8] etc.Recently, the polyhydroxylated Gd@C 82 material was found to possess a very high efficiency of inhibiting cancer growth in vivo, and to have a strong capacity to improve immunity and interfere with tumor invasion in normal muscle cells. Unlike conventional anticancer chemicals that use a high toxicity to kill cells, this material shows non-toxicity in vivo and in vitro and does not kill normal cells directly. [9,10] This finding indicates that this type of material with proper surface modifications may realize the human dream of cancer chemotherapeutics of high efficacy but low toxicity. Although the structural and electronic properties of endohedral metallofullerenes have been well investigated, [1] the chemical functionalization of the metallofullerene and its properties are not yet well studied and understood. [11,12] Recently, a unique electronic structure of Gd@C 82 caused by the encapsulation of the Gd atom was theoretically predicted.[13]How do the electronic properties of the material vary if the C 82 nanostructure is further modified with chemical groups? This is an intriguing topic for exploring the functions of a new nanomaterial because the modulation of the electronic properties of metallic atoms restricted to a nanospace is of significant and wide interest, though it is especially difficult. Recently, it was found that electronic configurations of atoms inside the fullerene cage can be tuned via chemical modifications to the cage surface. [14] But, on the chemical modifications of metallofullerenes it was found theoretically that i) the highest occupied molecular orbital (HOMO) in M@C 82 tends to distribute locally, [13] ii) the addition locations prefer to initiate at the cage surface opposite to the metallic position, [15] and iii) the addition pattern on the hollow fullerene cage tends to array as a cluster which shifts with the increasing number of added groups.[16] These raise many intriguing questions, for example, how do the electronic properties of the modified material vary with the changing number of added groups to the outer surface? To this end, we synthesized and purified the Gd@C 82 and Gd@C 82 (OH) x materials with a changing number of hydroxyls. The electronic properties of the Gd@C 82 (OH) x film were then studied using synchrotron radiation photoemission spectroscopy (SRPES) and X-ray absorption spectroscopy (SRXAS). Surprisingly, when the OH groups reach a certain number in Gd@C 82 (OH) x , the electron emission of the innermost Gd shows a periodical emergence or disappearance, depending on how many hydroxyls are added to the outer surface of the fullerene cages. Such a unique phenomenon is observe...

Metallofullerene nanoparticles circumvent tumor resistance to cisplatin by reactivating endocytosis

“…1C). Protonation or deprotonation of [Gd@C 82 (OH) 22 ] n varies the negative charges of the hydroxyl groups, which further modulates the repulsive static electric forces among the [Gd@C 82 (OH) 22 ] n species (28). These repulsive static-electric forces could affect the size of hydrophobic-forceinduced self-assembly of [Gd@C 82 (OH) 22 ] n nanoparticles.…”

The effect of Gd@C82(OH)22 nanoparticles on the release of Th1/Th2 cytokines and induction of TNF-α mediated cellular immunity

“…Some characterizations of water-soluble Gd@C 82 (OH) 22 nanoparticles were as described previously [8,[12][13][14][15][16]. Gd@C 82 (OH) 22 product was identified by a matrixassisted laser desorption time-of-flight mass spectrometer (MADLI-TOF-MS), and the structure was determined using infrared spectroscopy and nuclear magnetic resonance (NMR).…”

“…Gd@C 82 (OH) 22 nanoparticles were synthesized and characterized as described previously [8,[12][13][14][15][16]. The average number of hydroxyls was 22 as determined by XPS, and a schematic drawing of a Gd@C 82 (OH) 22 molecule was shown in Fig.…”

Antineoplastic activities of Gd@C82(OH)22 nanoparticles: tumor microenvironment regulation

“…It possesses a virus-like nanostructure, consisting of a magnetic metal core of a gadolinium (Gd) atom and a closed outer nanosheath of carbon atoms, which are further modified by about 22 outermost hydroxyl groups ( Figure 1) [9]. Several studies have found that the composition and numbers of the outer groups are largely responsible for the bioactive properties of fullerenol molecules [5,7,[14][15][16][17][18]. The Gd@C 82 (OH) 22 molecule is smaller than 2 nm, but Gd@C 82 (OH) 22 tends to aggregate in aqueous solutions and forms dispersed Gd@C 82 (OH) 22 nanoparticles with an average diameter of about 100 nm, which is a ubiquitous property identified in metallofullerenol studies [7].…”