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Free fluorescence spectra in solution and surface-enhanced Raman scattering (SERS) and surface enhanced fluorescence (SEF) spectra of chlorin e6 and water-soluble covalent fullerene–chlorin dyads have been studied. It has been demonstrated that chlorin e6 and covalent fullerene–chlorin dyads have similar characteristic SERS spectra. The fullerene–chlorin dyads show a pronounced SEF signal, while native chlorin e6 has no fluorescence on surface, which is consistent with the theory predicting an inverse dependence of the SEF intensity on the free fluorescence quantum yield. The concentration dependence of the SEF intensity is linear for the dyads in the range 0.1–2.0 μmol/L. These effects allow one to determine, with high sensitivity, the content of fullerene–chlorin dyads with a low quantum yield of free fluorescence in solutions, which opens wide opportunities for study of biological properties of fullerene–chlorin dyads and their applications in medicine.

Chlorin e6 derivative and water-soluble dyad resulting from covalent bonding of polyanionic fullerene С60 derivative to chlorin e6 derivative were synthesized and studied for spectral properties and photochemical activity. A considerable change in the absorption spectra and pronounced fluorescence quenching for the chlorin moiety included in the dyad were identified. The singlet excited state of chlorin is quenched via electron transfer from the excited chlorin to the fullerene core. A comparison of the photochemical activities of the test compounds in aqueous solutions showed a tenfold increase in the photochemical activity of the chlorin–fullerene dyad compared with free chlorin per absorbed light quantum.

In magnetic compounds with Jahn–Teller (JT) ions (such as Mn3+ or Cu2+), the ordering of the electron or hole orbitals is associated with cooperative lattice distortions. There the role of JT effect, although widely recognized, is still elusive in the ground state properties. Here we discovered that, in these materials, there exist excitations whose energy spectrum is described in terms of the total angular momentum eigenstates and is quantized as in quantum rotors found in JT centers. We observed features originating from these excitations in the optical spectra of a model compound LaMnO3 using ellipsometry technique. They appear clearly as narrow sidebands accompanying the electron transition between the JT split orbitals at neighboring Mn3+ ions, displaying anomalous temperature behavior around the Neel temperature T N ≈ 140 K. We present these results together with new experimental data on photoluminescence found in LaMnO3, which lend additional support to the ellipsometry implying the electronic-vibrational origin of the quantum rotor orbital excitations. We note that the discovered orbital excitations of quantum rotors may play an important role in many unusual properties observed in these materials upon doping, such as high-temperature superconductivity and colossal magnetoresistance.

The potential of surface enhanced Raman spectroscopy (SERS) for the detection of water-soluble fullerene derivatives and their covalent conjugates with xanthene dyes was investigated in model biological liposome membranes and in the albumin protein structure. It was shown that in liposomes and in albumin, fullerene derivatives and their covalent conjugates with dyes show characteristic SERS spectra, which allows detection of water-soluble fullerene derivatives in phosphatidylcholine liposomes at the lipid/fullerene derivative ratio of 100 as well as fullerene–dye conjugates in liposomes and albumin.

229 As known, fullerenes are photoexcited to a triplet state in 100% quantum yield, which then is deacti vated to generate, depending on the polarity of a medium, either singlet oxygen О2 or superoxide radi cal anions and other active radicals [1]. Numerous studies have addressed the photodynamic effect of fullerene and their derivatives: the generation of active radicals upon photoexcitation is responsible for dam age of DNA, proteins, and membranes, as well as for the suppression of the reproduction of tumor cells, viruses, and bacteria [2]. However, the efficiency of the photodynamic action of fullerenes and the pros pects for their application in medicine are essentially limited by the weak absorption by fullerenes of visible light, especially in the range 650–800 nm, which is most suitable for photodynamic therapy. The photodynamic effect of fullerenes can be con siderably enhanced by creating hybrid nanostructures − О2 . (HNSs) via the formation of a fullerene complex with a dye that efficiently absorbs visible light [3]. In such a complex, the dye can efficiently absorb light and transfer excitation energy or electron to the fullerene. Further excitation transfer or electron transfer from the fullerene to molecular oxygen will generate active oxygen species. The creation of such an HNS based on fullerene and a dye can thereby significantly enhance the efficiency of photodynamic therapy.