Encapsulated fullerene

It was clearly shown by EPR measurements that irradiation of aqueous suspensions of Ti02 and surfacted or encapsulated fullerene derivatives leads to the formation of fullerene radical anions by electron transfer from excited Ti02. The reduction of the embedded derivative compared to the surfacted one is more efficient [183], However, in comparison to organic solvents, the reduction yield of the fullerenes radical anions in aqeous media is lower. This may be explained by the influence of the aquatic environment and the stability of the radical anions formed [183,184], Nevertheless, electron transfer still occurs from the donor to the fullerenes triplet-excited state [182,185,186],... 

The incorporation of guest molecules can be achieved during their growth or is executed at defect sites and holes via wet chemistry, by surface diffusion and gas-phase transport. Encapsulated fullerenes tend to form chains that are coupled by van der Waals forces. Upon annealing, the encapsulated fullerenes coalesce in the interior of the SWCNTs, resulting in pill-shaped, concentric, endohedral capsules a few nanometers in length [265], The progress of such reactions inside the tubes could be monitored in real time by use of HR-TEM [266],... 

Fig. 8.6. HREM image of SWNTs obtained by arcing graphite electrodes filled with Ni and Y2O3 under a He atmosphere (660 Torr). Inset The HREM image of encapsulated fullerenes inside the SWNTs scale bar is 5 nm. Reproduced from ref [45], with...

Cso peapods, C50 encapsulated inside a CNT, were first produced and observed during CNT synthesis by pulsed laser vaporization [150]. Nowadays the synthesis of encapsulated fullerenes [151], endohedral fullerenes [71,151-156] and volatile organometallic complexes of fullerenes [157] within the CNTs is mainly achieved by vapor phase filling technique, consisting in heating at the... 

Rare Earth Encapsulated Fullerenes. Alkali metal encapsulated fullerenes have attracted interest since some of them such as K3C60 exhibit superconductivity at relatively high temperatures. Interesting applications have been found for rare earth metal encapsulated ftiUerene. For example, Gd Cg2 was reported to show enhanced properties as a contrast agent for MRIs. The Gd + ions act as a relaxation mechanism for the proton in water molecules in bodies and strengthen the contrast of MRI images. 

The authors also found that their rod-coil systems proved to be feasible to encapsulate fullerens into the cavities. Compared to usual solvents for 50 and C70, such as dichloromethane or toluene, the solubility was enhanced by up to 1000 times when the molecules were encapsulated into rod-coil micelles. The solubilization of up to 10 billion fullerenes into one micelle increased the aggregation number to 10 and the obtained diameters up to 30 fim [136]. Such micro containers could also be used for an encapsulation process of other substances and so one can think of applications, such as drug delivery, emulsions, etc. 

Helium ( He) (/= 1/2). The endohedral NMR chemical shifts of various known H2-H2O- and NH3-encapsulated fullerene compounds were calculated at the GIAO-B3LYP/3-21G and GIAO-HF/3-21G levels of theory with AMI- and PM3-optimised structures. The shift tendency of endohedral NMR chemical shifts were discussed and compared with that of endohedral He NMR chemical shifts.The equilibrium geometries and relative stabilities of the 19 possible isomers of C84O were studied... 

Okada, S. (2007). Radial-breathing mode frequencies for nanotubes encapsulating fullerenes. Chemical Physics Letters, 438, 59-62. 

Smith, B. W., Monthioux, M., Luzzi, D. E. (1999). Carbon nanotube encapsulated fullerenes A unique class of hybrid materials. Chemical Physics Letters, 315, 31-36. 

Wang, G.-W, Zhang, X.-H., Zhan, H., Guo, Q.-X., Wu, Y.-D. (2003). Accurate calculation, prediction, and assignment of He NMR chemical shifts of Helium-3-encapsulated fullerenes and fullerene derivatives. Journal of Organic Chemistry, 68, 6732-6738. 

The different reactivities depending on the solvents can be attributed to the solvation of the reaction intermediate In toluene, adduct formation is considered to proceed in the triplet exciplex on the other hand, in benzonitrile, the solvated radical ion pair can react with solvent molecules. In the case of the reaction with the La Cg2> Akasaka et al. observed adduct formation in both the photo- and thermal-reaction conditions [63]. Higher reactivity of La C82 can be attributed to the high electron acceptor ability of La C82. It has been reported in the electrochemical studies on metal encapsulated fullerenes that the reduction potential of La Cg2 shifts to the anodic direction by 0.7 V in comparison with Qo-... 

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