Showing papers by "Sydney Leach published in 1994"

C60 in Model Biological Systems. A Visible-UV Absorption Study of Solvent-Dependent Parameters and Solute Aggregation

Abstract: A study was made of the solubilization of C[sub 60] in various solvents and systems of biological interest, i.e., octanols, micelles, and liposomes, using visible-UV absorption spectroscopy as a diagnostic tool. The state of incorporation of C[sub 60] molecules in micellar and colloidal liposome solutions was monitored using a number of spectroscopic criteria of solute-solvent and solute-solute interactions based on comparison with spectra obtained in alkane and octanol solvents and from thin films of C[sub 60]. Spectral red shifts and intensity modifications of C[sub 60] absorption and C[sub 60] aggregation are discussed in terms of environment-dependent physical parameters. The results indicate that C[sub 60] can be dispersed in micellar solutions of Triton X-100 and Triton X-100 R-S, the fullerene molecules being localized in the inner hydrophobic part of the micelles. C[sub 60] was shown to be incorporated, mainly as aggregates, into phosphatidylcholine liposome colloidal solutions. It is concluded that micellar and liposome solutions can be prepared which could be used to transfer individual C[sub 60] molecules, or groups of molecules, to biological cells. 38 refs., 9 figs., 2 tabs.

Electronic Spectroscopy and Photophysics of Fullerenes

Abstract: Electronic spectra of the fullerenes C60 and C70 are discussed in conjunction with theoretical insights. Experimental studies include singlet-singlet (190–800 nm) and triplet-triplet (300–1600 nm) absorption spectroscopy of fullerene solutions of C60 and C70 as well as gas phase electron energy loss spectroscopy (1–10 eV) of C60. The spectra are analyzed in terms of allowed and forbidden electronic transitions which exhibit Herzberg-Teller vibronic coupling and Jahn-Teller effects. The spectra of higher fullerenes are briefly considered. Quantum yield measurements of the triplet state formation of C60 and C70, and of the C70 photosensitized formation of O2(1Δg) are shown to have photophysical implications. Two applications of the spectroscopy and photophysics of C60 and C70 are presented and discussed. In the first their photochromic properties lead to their potential use in optical limiter devices ; the second application concerns transmembrane electron transport mediated by photoexcited fullerenes.