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The oxidation of guanine (G) is studied by using transient absorption and time-resolved resonance Raman spectroscopies combined with pulse radiolysis. The transient absorption spectral change demonstrates that the neutral radical of G (G(•)(-H(+))), generated by the deprotonation of G radical cation (G(•+)), is rapidly converted to other G radical species. The formation of this species shows the pH dependence, suggesting that it is the G radical cation (G(•+))' formed from the protonation at the N7 of G(•)(-H(+)). On one hand, most Raman bands of (G(•+))' are up-shifted relative to those of G, indicating the increase in the bonding order of pyrimidine (Pyr) and imidazole rings. The (G(•+))' exhibits the characteristic CO stretching mode at ∼1266 cm(-1) corresponding to a C-O single bond, indicating that the unpaired electron in (G(•+))' is localized on the oxygen of the Pyr ring.

We report in situ observations of molecular interactions and photodynamics for the polarity-sensitive fluorescence dye 4-dimethylamino-4′-nitrostilbene (DNS) when encapsulated inside of metal−organic frameworks (MOFs) by utilizing single-molecule, single-particle fluorescence spectroscopy. While the fluorescence intensity from DNS molecules adsorbed onto the surface of MOF-177 particles exhibited a strong solvent polarity dependence toward external solvent exchanges, the intensity from molecules encapsulated inside of well-defined MOF-177 particles slightly changed when the solvent was switched from toluene to chloroform. Furthermore, the photostability of the DNS molecules was significantly enhanced by incorporation into the MOF host. These observations strongly suggest that guest molecules encapsulated in MOFs should be protected from external solvent and gas molecules. The photoblinking behavior of encapsulated single DNS molecules was also observed and analyzed in terms of the probability density.

Emission from charge recombination between radical cation and anion of various aromatic hydrocarbons (AHs) was observed in the time scales of nanosecond to microsecond during the pulse radiolysis of AH in benzene (Bz). Based on the time-dependent emission study, it is suggested that AH in the excited singlet state ( 1 AH * ) is generated in the nanosecond to microsecond time scale mainly from the charge recombination between AH radical cation (AH + ) and AH radical anion (AH − ). This mechanism is reasonably explained by the relationship between the annihilation enthalpy change (−Δ H °) for the charge recombination and excitation energies of 1 AH * ( E S1 ). It is found that the rate constant of the charge recombination ( k rec ) between AH + and AH − increases with the increase of energy differences between −Δ H ° and E S1 of AH (−Δ H ° − E S1 ), indicating that the intensity of the radiolysis-induced emission from AH ( I ) depends on (−Δ H ° − E S1 ). The effect of (−Δ H ° − E S1 ) on I value was also examined during the pulse radiolysis of mixtures of two AHs in Bz. Consequently, it is suggested that not only the fluorescence quantum yield ( Φ fl ) of 1 AH * but also (−Δ H ° − E S1 ) is important factor for the formation yield of 1 AH * during the pulse radiolysis of AH in Bz.

Iodine-doped TiO2 powders (I-TiO2) prepared via hydrothermal treatment have absorption in the region of ultraviolet (UV) and visible light, and were used as a photocatalyst with irradiation of UV or visible light. The I-TiO2 powders were characterized by XRD, TEM, EDS, XPS, FTIR, and steady-state UV−vis diffuse reflectance spectra (DRS), and their photocatalytic activities were investigated based on the photodegradation of 4-chlorophenol (4-CP) in water. A higher photodegradation efficiency of 4-CP was observed for I-TiO2 under UV- and visible-light irradiation, when compared to the undoped TiO2. The transient behavior of the photogenerated charge carriers, such as trapped electrons (e−) and holes (h+), and the one-electron oxidation dynamics of substrates during UV or visible laser flash photolysis of undoped TiO2 and I-TiO2 powders were investigated using time-resolved diffuse reflectance (TDR) spectroscopy. The time evolution of transient signals indicated that the long-lived photogenerated h+ were for...

The single-molecule detection of airborne reactive oxygen species (ROS), such as singlet oxygen (1O2) and hydroxyl radical (•OH), diffused from the photoirradiated TiO2 surface, was successfully demonstrated using single-molecule fluorescence spectroscopy. Airborne single 1O2 and •OH molecules were selectively detected by the fluorescent probes, terrylenediimide (TDI) and 3‘-(p-hydroxyphenyl) fluorescein (HPF), respectively. Generation of the airborne 1O2 and •OH from the TiO2 surface has been investigated under various conditions, such as the excitation wavelengths (UV or visible) and the types of TiO2 (pure or nitrogen (N)-doped). Upon UV excitation, 1O2 and •OH were detected from both the pure and N-doped TiO2 samples, while 1O2 was exclusively detected only from the N-doped TiO2 upon visible excitation. Furthermore, the spatial and temporal distribution of the airborne •OH molecules diffused from the photoirradiated TiO2 surface was investigated by the real-time single-molecule imaging technique. The ...

The fluorescence spectrum with a peak around 620 nm and lifetime of 41 ± 2 ps for 1,3,5-trimethoxybenzene radical cation (TMB + ) in the excited state (TMB +∗ ) were directly measured with ns–ps two-color two-laser flash photolysis at room temperature. The fluorescence of TMB +∗ is assigned to the D 2 → D 0 transition, showing that TMB + is one example of radical cations which violate Kasha’s rule. The fluorescence quantum yield of TMB +∗ was determined to be 5.4 × 10 −3 , and the radiative and nonradiative decay rate constants were 1.3 × 10 8 and 2.4 × 10 10 s −1 , respectively.

Radical cations of trans-stilbene and substituted trans-stilbenes (stilbenes and the radical cations denote Sand S(*+), respectively) were generated from the resonant two-photon ionization (TPI) in acetonitrile with irradiation of one-laser (266- or 355-nm laser) and with simultaneous irradiation of two-color two-lasers (266- and 532-nm or 355- and 532-nm lasers) with the pulse width of 5 ns each. The formation yields of S(*+), the TPI efficiency, depended on the properties of S in the lowest and higher singlet excited state (S(S(1)) and S(S(n))), generated from one-photon excitation with 266- or 355-nm laser and from two-photon excitation with simultaneous irradiation of 266- and 532-nm or 355- and 532-nm lasers, respectively. The TPI efficiency using two-color two-lasers increased compared with that using one-laser. It is confirmed that the TPI proceeds through two-step two-photon excitation with the S(0) --> S(1) --> S(n)() transition. In addition to the electronic character of S(S(0)) which depends on the substituent of S, oxidation potential, and molar absorption coefficient of the S(0) --> S(1) absorption as well-known important factors for the TPI efficiency, it is shown that properties of S(S(1)) and S(S(n)) such as lifetimes, electronic characters of S(S(1)) and S(S(n)), molar absorption coefficient of the S(1) --> S(n) absorption, and ionization rate from S(S(n)) are also important.

Transient phenomena of polyphenyls (PP), such as biphenyl (BP), p-terphenyl (TP), and 1,3,5-triphenylbenzene (TPB) in the higher triplet excited states (T n , n ≥ 2), were investigated with the nanosecond-nanosecond (ns-ns) two-color two-laser excitation method. PP(T n ) was generated by the excitation of PP in the lowest triplet excited state (PP(T 1 )) at the wavelength tuned to the absorption of PP(T,). Bleaching of the transient absorption of BP(T,) and TP(T,) was observed during the second laser irradiation in the presence of chloroalkanes (RC1) such as carbon tetrachloride (CCl 4 ), dichloromethane (CH 2 Cl 2 ), or 1,2-dichloroethane (DCE). In the case of TPB, clear bleaching of TPB(T 1 ) was observed in the presence of CCl 4 , while no bleaching was observed in the presence of CH 2 Cl 2 and DCE. No formation of PP + was detected during the quenching of PP(T n ) by RCl. Therefore, the bleaching of PP(T 1 ) is attributed to triplet energy transfer quenching of PP(T n ) by RCl followed by the C-Cl bond cleavage. The lifetimes (τ T n ) of PP(T n ) were estimated from the dependence of the quenching efficiency on the RCl concentration. It was found that the τ T n value decreased with the increasing number of benzene rings, BP(T n ) (950 ps) > TP(T n ) (620 ps) > TPB(T n ) (360 ps). The quenching mechanism of PP(T n ) by RCl was discussed.

Properties of the higher excited triplet states (T n ) of oligo(p-phenylenevinylene)s (OPVn, n denotes the number of phenyl rings, n = 3, 4) were investigated with use of the ns-ps and ns-ns two-color two-laser flash photolysis techniques. The lowest triplet excited states of OPVn were generated through the triplet energy transfer (ENT) process by the first 355-nm laser irradiation to the triplet sensitizer. With the delay time of 4 μs after the first laser irradiation, OPVn(T 1 ) was selectively excited with the second 532-nm laser. Bleaching of the absorption of OPVn(T 1 ) was observed during the second ps laser irradiation, indicating the generation of OPVn(T n ). The bleaching completely recovered at a few tens of picoseconds after the second picosecond laser irradiation, because of the internal conversion from OPVn(T n ) to OPVn(T 1 ). The lifetimes of T n were estimated to be 35 and 30 ps for OPV3 and OPV4, respectively. In the presence of the triplet energy acceptor (Q), the quenching and recovery of the T 1 -absorption bands of OPVn were observed because of ENT from OPVn(T n ) to Q and Q(T 1 ) to OPVn, respectively. On the basis of the ENT from OPVn(T n ) to a series of Q, the T 2 -T 1 energy gaps of OPV3 and OPV4 were estimated to be 1.3 and 1.1 eV, respectively.

Charge transfer in DNA is of current interest because of the involvement of charge transfer in oxidative DNA damage and electronic molecular devices. We have investigated the charge separation process via the consecutive adenine (A)-hopping mechanism using laser flash photolysis of DNA conjugated with naphthaldiimide (NDI) as an electron acceptor and phenothiazine (PTZ) as a donor. Upon the 355-nm laser flash excitation of NDI, the charge separation and recombination process between NDI and PTZ was observed. The yields of the charge separation via the consecutive A-hopping were slightly dependent upon the number of A bases between the two chromophores, while the charge recombination rate was strongly dependent upon the distance. The charge-separated state persisted over 300 micros when NDI was separated from PTZ by eight A bases. Furthermore, the rate constant of the A-hopping process was determined to be 2 x 10(10) s(-1) from an analysis of the yield of the charge separation depending on the number of A-hopping steps.

One-electron oxidation of 4-methyl- p -tolylsulfide (MTS) and 4-methylthiophenylmethanol (MTPM) adsorbed on the surface of TiO 2 powder slurried in acetonitrile has been investigated by the time-resolved diffuse reflectance spectroscopy. Relatively high concentration of the adsorbed MTPM determined by UV absorption spectral measurements clearly indicates that the –OH group of MTPM plays an important role in adsorbing on the surface of TiO 2 particles. The initial concentration of the radical cations of substrates generated from one-electron oxidation with valence band holes or trapped hydroxyl radical significantly depended on the substrate concentration adsorbed on the TiO 2 surface.

Perylene microcrystals with different sizes were prepared by the reprecipitation and subsequent microwave irradiation method. Their excitonic absorption peaks were blue-shifted with decreasing crystal size in the size range of sub-micrometer. Perylene microcrystal films were also fabricated by means of the electrostatic adsorption method to investigate the dependence of the excitonic absorption spectra on temperature. As a result, the temperature-dependence of half-width of the excitonic absorption spectra was well explained by Toyozawa’s theoretical prediction, which was based upon an interaction between exciton and lattice vibration. In addition, it was revealed that the peak position of emission spectra from the self-trapped exciton (STE) state was relatively blue-shifted in comparison with the bulk crystal, and that the lifetime of STE emission became shorter in perylene microcrystal in any temperature.

Photoinduced electron-transfer processes between C 60 or C 70 and zinc octaethylporphyrin ( ZnOEP ) have been studied in polar solvents with the nanosecond laser flash photolysis method, observing the transient absorption spectra in the visible and near-IR regions. By the predominant excitation of ZnOEP with 532 nm laser light the transient absorption bands of 3 ZnOEP * decayed, accompanied by the appearance of the transient absorption bands of [Formula: see text] and [Formula: see text]. By the predominant excitation of C 60 and C 70 with 610 nm laser light the decays of [Formula: see text] and [Formula: see text] were observed, accompanied by the appearance of [Formula: see text] and [Formula: see text]. The electron transfer rate constants (k et ) and the quantum yields (Φ et ) of [Formula: see text] and [Formula: see text] formation via 3 ZnOEP * and [Formula: see text] or [Formula: see text] have been evaluated. These values increase with the solvent polarity; in polar benzonitrile these values are higher than for other porphyrins such as zinc tetraphenylporphyrin. The back electron transfer rate constants were evaluated from the decays of [Formula: see text] and [Formula: see text], which also show a solvent polarity dependence.

Systematic studies of electron-transfer processes in the ground states and excited triplet states of pyrrolidinofullerenes {C60(C3H6N)R [R=H (1), p-C6H4NO2 (2), p-C6H4CHO (3), p-C6H5 (4), p-C6H4OMe (5), p-C6H4NMe2 (6)]} with tetrakis(dimethylamino)ethylene (TDAE) have been carried out by steady-state and transient absorption measurements in the visible–NIR region. Analyses of the equilibria of the electron-transfer processes in the ground states indicate that free ion radicals are produced in polar solvents. Photoinduced electron-transfer processes viaT(C60(C3H6N)R)* were observed by applying a perturbation to the equilibria of the electron-transfer reactions in the ground states by laser flash photolysis. Based on the relationship of the thermodynamic data and kinetic data, the electron-transfer rate constants in the ground states (ketG) can be evaluated. The ketG values are affected by the substituents to a smaller extent compared with the equilibrium constants (K) in polar solvents; α=0.6 in Δ log ketG=α Δ log K. This α value indicates that the activation energies of forward electron transfer in the ground states vary moderately with the thermodynamic stabilities of (C60(C3H6N)R)-. Electron-transfer rate constants viaT(C60(C3H6N)R)*, which are close to the diffusion-controlled limit, do not show a large substituent effect (α′=0), because of their highly exothermic processes. Such a linear free-energy relationship can be extended to other systems such as T(C60(C3H6N)R)*/N,N-dimethylaniline, from which valuable information for electron-transfer processes can be obtained.

Since reduction and oxidation of DNA are essential processes occurring in various biological phenomena, electron and hole transfer in DNA has drawn recent attention because of its importance and potential application in biological science and nano-biotechnology, respectively. In practice, it is known that the reduction of DNA closely relates to the repair of damaged DNA such as a T-T cyclobutane lesion, whereas the oxidation of DNA promotes oxidative damage, apoptosis, and cancer. Thus, it is important to understand the mechanisms and dynamics of DNA-mediated charge-transfer processes. Excess electron transfer (EET) in DNA has been studied by various techniques, such as laser flash photolysis, g-ray radiolysis, or product analysis which were used to analyze the cleavage of 5-bromo-2’-deoxyuridine (BrdU) or the T-T dimer in DNA by photoinduced electron transfer. The laser flash photolysis is conducted principally on shortlength DNA, which is containing four A-T base pairs between two chromophores. Meanwhile, the DNA-mediated hole transfer occurs over a distance greater than 20 nm and the migration of the hole along the DNA involves many steps of short-distance charge-transfer processes between stacked guanine (G) bases because guanine among the four natural DNA bases is most sensitive to oxidation. The hole transfer rate depends on the inserted nucleobase between the G-C base pairs. In addition, the delocalization of the charge over the stacked G bases along the DNA stem has also been reported. Most studies on DNA-mediated charge-transfer processes have been performed on a DNA duplex with Watson–Crick base pairing. However, recently, non-B DNAs including Gquadruplexes have attracted great attention as fascinating materials for nanotechnology because of their unique structures. Especially, G-quadruplexes formed from various G-rich sequences have received great attention in biological research because in vitro they block the binding of telomerase and act as a transcriptional repressor element and enzyme to provide cancerous cells immortality. Furthermore, G-quadruplexes are an emerging topic for developing DNA-based molecular electronic devices because of their ability as electron carrier, their unique hole-trapping property, and their high conductance. With hole transfer in DNA, recently, hole trapping has also been regarded as an important process to determine the overall efficiency of hole migration in DNA. Here, we have investigated the hole transfer and trapping in a riboflavin-labeled G-quadruplex using femtosecond (fs) laser flash photolysis and pulse radiolysis. In contrast to duplex DNAs, in which p-p stacking has been believed to be a medium for hole transfer, G-quadruplexes have G-quartet structures composed of four G-bases located in the same plane and have also the stacked G-bases (Scheme 1). Thus, it

Photoluminescence (PL) spectra of thin films of pyrrole and bithiophene copolymer with an alternating layered structure prepared by the potential‐programmed electropolymerization method were investigated. Band edges of thin films of the copolymers were estimated by optical and electrochemical method, and they were adopted to design a superlattice potential profile of the alternating layered film. PL spectra of the copolymer films shifted to higher energies as thiophene fraction in the film decreased. This shift corresponded to band structure change. PL spectra of the layered films, designed to be type II superlattices structure, shifted to higher energies as periodicity of the layered structure became shorter. This phenomenon is to be interpreted as a quantum size effect. The observed shift was explained by the Kronig–Penney model with 0.6me (electron mass) of effective mass.

Lanthanide-based metal-organic frameworks (Ln-MOFs) are fascinating because of their versatile coordination geometry, unique luminescent and magnetic properties, and possible high framework stability to water. We synthesized nanosized europium-based MOF (Eu-MOF) particles and investigated the photoinduced electron transfer between the excited Eu-MOF nanoparticles and various organic compounds, such as aromatic sulfides and amines. From the time-resolved emission measurements, the bimolecular quenching rate constants of luminescence from the Eu(3+) ions in the MOF framework by electron donors were determined and explained in terms of the Marcus theory of electron-transfer reactions. Furthermore, spatially resolved emission quenching images obtained by confocal fluorescence microscopy revealed that small (large) quencher molecules quickly (slowly) and homogeneously (inhomogeneously) penetrate microsized Eu-MOF crystals. These observations led us confidently to assume the possibility that Eu-MOFs work as a size-selective photocatalyst for the one-electron oxidation of organic compounds.

DNA charge transfer highly depends on the electronic interaction between base pairs and reflects the difference in the base composition and sequence. For the purpose of investigating the charge transfer process of individual DNA molecules and the optical readout of DNA information at the single-molecule level, we performed single-molecule observation of the DNA charge transfer process by using single-molecule fluorescence spectroscopy. The DNA charge transfer process, leading to the oxidation of the fluorescent dye, was explored by monitoring the on–off signal of the dye after the charge injection by the excitation of a photosensitizer. The photobleaching efficiency of the dyes by the DNA charge transfer specifically depended on the base sequence and mismatch base pair, demonstrating the discrimination of the individual DNA information. Based on this approach, the optical readout of a single-base mismatch contained in a target DNA was performed at the single-molecule level.

Bimolecular hole transfer quenching of the 1,3,5-trimethoxybenzene radical cation (TMB*+) in the excited state (TMB*+*) by hole quenchers (Q) such as biphenyl (Bp), naphthalene (Np), anisole (An), and benzene (Bz) with higher oxidation potentials than that of TMB was directly observed during the two-color two-laser flash photolysis at room temperature. From the linear relationships between the inverse of the transient absorption changes of TMB*+ during the second 532-nm laser excitation versus the inverse of the concentration of Q, the rate constant of the hole transfer from TMB*+* to Q was estimated to be (8.5 +/- 0.4) x 10(10), (1.4 +/- 0.7) x 10(11), (1.3 +/- 0.6) x 10(11), and (6.4 +/- 0.3) x 10(10) M(-1)s(-1) for Bp, An, Np, and Bz, respectively, in acetonitrile based on the lifetime of TMB*+*. The estimated rate constants are larger than the diffusion-controlled rate constant in acetonitrile. Short lifetime, high energy, and high oxidation potential of TMB*+* cause the lifetime-dependent quenching process or static quenching process as the major process during the quenching of TMB*+* by Q as indicated by the Ware's theoretical model. The subsequent hole transfer from Q*+ to TMB, giving TMB*+, was found to occur at the diffusion-controlled rate for Bp and An as Q. For Q such as Np and Bz, the dimerization of Q*+ with Q to give dimer radical cation (Q2*+) occurred competitively with the hole transfer from Q*+ to TMB.

The local structure of the TiO2 surface modified with electron-donating bidentate ligands, such as catechols, has been investigated by solid-state NMR spectroscopy. The adsorption and degradation processes of catechols at the TiO2 surface were observed. The photocatalytic degradation mechanism of catechols at the TiO2 surface was interpreted in terms of the interfacial charge recombination reaction with conduction band electrons.

The formation of the pyrene (Py) dimer radical cation (Py 2 * + ) was used to measure the kinetics of the intrastrand end-to-end contact rates of single-stranded DNAs (ssDNAs) in the 10 nanoseconds to the tens of microseconds time range. ssDNAs labeled with Py at both ends with the lengths of 3, 6, and 9 mer were synthesized, and the two-photon ionization method was employed to generate a Py* + , which enables the measurements of the end-to-end contact rates from 10 ns. The formation rate of Py 2 * + depended on the length and the sequence of the ssDNAs, and about 1 order of magnitude faster rates were observed for the T-rich ssDNAs compared to those for the corresponding length of A-rich ssDNAs, showing that ssDNA made from adenines is much more rigid than that composed of thymidines. As for the T-rich ssDNAs, the formation of Py 2 * + attributed to the misfolded structures was also observed, which is consistent with the configurational diffusion model suggested by Ansari and co-workers.

The lifetimes of benzophenone in the higher triplet excited state (BP(T n )) and several BP derivatives in the T n states were measured directly to be τ T n =37′7 ps and 20-33 ps, respectively, by using the nanosecond-picosecond (ns-ps) two-color/two-laser flash photolysis method. Based on the direct measurements of τ T n of BP(T n ), the triplet energy transfer (TET) from BP(T n ) to quenchers (Q), such as carbon tetrachloride (CCl 4 ), benzene (Bz), and p-dichlorbenzene (DCB), was investigated. The fast TET from BP(T n ) to Q can be attributed to the lifetime-dependent quenching process, according to the Ware theoretical model of the bimolecular energy transfer reaction. The contribution of the lifetime-dependent term on k T E T was 27, 60, and 86% for CCl 4 , Bz, and DCB as the Q of BP(T n ), respectively, indicating that the TET from BP(T n ) to Q is influenced not only by τ T n , but also by the size of Q.

Mechanism of photo-induced electron transfer and the subsequent hole transfer in DNA has been studied extensively, but so far we are not aware of any reliable report of the observation of the long-distance hole-transfer process. In this article, we demonstrate the results of direct observation for the long-distance hole transfer in double-helical DNA over 100 Å with time-resolved transient absorption measurements. DNA conjugated with naphthalimide (NI) and phenothiazine (PTZ) (which worked as electron-acceptor and donor molecules, respectively) at both 5′ ends was synthesized to observe the hole-transfer process. Site-selective charge injection into G by means of the adenine-hopping process was accomplished by excitation of NI with a 355-nm laser flash. Transient absorption around 400 nm, which was assigned to the NI radical anion, was observed immediately after the irradiation of a laser flash, indicating that the charge separation between NI and the nearest G occurred. Then, the transient absorption of the PTZ radical cation (PTZ •+ ) at 520 nm was emerged, which was attributed to the hole transfer through DNA to the PTZ site. By monitoring the time profiles of the transient absorption of PTZ •+ for NI-A 6 -(GA) n -PTZ and NI-A 6 -(GT) n -PTZ ( n = 2, 3, 4, 6, 8, 12) (base sequences correspond to those for DNA modified with NI), the long-distance hole-transfer process from G to PTZ, which occurred in the time scale of microsecond to millisecond, was observed directly. By assuming an average distance of 3.4 Å between base-pairs, total distance reaches 100 Å for n = 12 sequences. Our results clearly show the direct observation of the long-distance hole transfer over 100 Å.

The hole transfer causes the long-lived charge-separated state in DNA during the photosensitized one-electron oxidation of DNA. The combination of the transient absorption measurement and DNA damage quantification by HPLC clearly demonstrated that the yield of the DNA damage correlates well with the lifetime of the charge-separated state.

The DNA base stack provides unique features for the efficient long-range charge transfer. For the purpose of investigating the hole transfer process of individual DNA and the optical readout of DNA information at the single molecule level, we performed single-molecule detection of DNA hole transfer (DNA HT) using single-molecule fluorescence spectroscopy. We have established the single-molecule detection of DNA HT at the single molecule level based on the fluorescence generation by combining the oxidative reaction of the quencher molecule through DNA HT and the cancellation of FRET. This "signal-on" detection system makes it possible to detect DNA HT in individual DNA and the base-pair mismatch in the target DNA with high sensitivity and accuracy.

Properties of the excited states of endohedral metallofullerenes (La@C82 and La2@C80) have been investigated by time-resolved absorption spectroscopy. Transient absorption bands of La@C82 showed two decay-components, which were attributed to excited states of different spin multiplicity. The properties of photoexcited states of La2@C80 are also reported.

The rate constant for electron transfer from C60-anion radical (C60•−) to molecular oxygen was evaluated to be (3.7 ± 0.2) × 102 mol−1 dm3 s−1 in benzonitrile by following the concentration of the C60•− by laser flash photolysis with a detector in the near-IR region for long time scale (> 0.1 s).

Fluorescence lifetimes have been measured for the adducts of ammonium 4-chloro-2,1,3-benzoxadiazole-7-sulfonate, which is known as a fluorescence probe specific to thiol groups Although the adduct with simple molecule such as mercaptoethanol showed a single exponential fluorescence decay, most adducts with amino acid, peptide, coenzyme and protein showed the bi exponential decay. The fluorescence lifetimes and ratio of the short lifetime fraction to long lifetime fraction of the SBD adducts with biomolecules vary with the molecular size, solvent polarity and micro environment around the fluorescence probe.