摘要:

AbstractAn overview is given for the experimental and theoretical development on fluorescence intermittency (blinking) in semiconductor crystalline nanoparticles. We consider a model with photoinduced spectral diffusion and diffusion‐controlled electron transfer processes as the underlying mechanism for intermittency in quantum dots. Depending on the frequency response of a dielectric medium, anomalous/normal diffusion in energy space leads to power‐law intermittency for single quantum dots and quasi‐stretched exponential decay in ensemble‐averaged fluorescence intensity. Intricate relationship between single particle and ensemble behavior is discussed. Some kinetic and energetic parameters are linked to the temporal behavior of blinking statistics and ensemble fluorescenc

ISSN:0009-4536    

DOI:10.1002/jccs.200600001

出版商:WILEY‐VCH Verlag    

年代:2006

数据来源: WILEY

摘要:

AbstractTwo dimensional (2D) heterodyne‐detected electronic photon echo spectroscopy is introduced and described. We give an intuitive description of the origin and information content of 2D electronic spectra, focusing on molecular complexes. We identify two important quantities—the transition dipole term, and the transition frequency cross correlation function that controls the appearance of 2D electronic spectra.We also show how the transition frequency cross correlation function controls the rate of exciton relaxation. These concepts are illustrated with experimental data on the seven bacteriochlorophyll FMO complex of a green sulfur bacterium, showing how the pathways and mechanisms of energy flow can be elucidated by combining 2D spectra with theoretical model

ISSN:0009-4536    

DOI:10.1002/jccs.200600002

出版商:WILEY‐VCH Verlag    

年代:2006

数据来源: WILEY

摘要:

AbstractCollision relaxation cross sections of asingle, highly vibrationally excited level in the ground electronic state of SO2at 44877.52 cm−1above the zero‐point by the collision partner CO has been measured in a supersonic expansion using the kinetic quantum beat spectroscopic technique. The depopulation cross section at 14.5 K for this SO2*‐CO system has been determined to be 75 Å2, while the dephasing cross section is 22 Å2. Comparison with previously measured cross sections for the SO2*‐SO2, SO2*‐inert gases systems at room temperature using a similar spectroscopic approach reveals both the long range interaction and repulsive force contributions to the relaxation cross sections of highly vibrationally excite

ISSN:0009-4536    

DOI:10.1002/jccs.200600003

出版商:WILEY‐VCH Verlag    

年代:2006

数据来源: WILEY

摘要:

AbstractPhotoisomerization and photodissociation of toluene, xylene, 4‐methyl‐pyridine, and aniline under collision‐free conditions are reviewed. For many years, it was thought that all the isomerization of aromatic molecules could be described in terms of ring permutation. One important characteristic of ring permutation is that the atoms belonging to the alkyl or amino groups attached to the aromatic ring are not involved in the exchange with the atoms within the aromatic ring. Only the relative positions of these alkyl or amino groups are changed. However, the observation of new dissociation products from toluene, xylene, 4‐methyl‐pyridine, and aniline suggests that a small fraction of these molecules undergo another kind of isomerization prior to dissociation. This isomerization involves the exchange between six‐membered ring and seven‐membered ring structures. It provides a new pathway for aromatic molecules to undergo totally different structural change. The significance of this isomerization is that the carbon atoms (or nitrogen atom) and hydrogen atoms belonging to the alkyl group (or amino group) attached to the aromatic ring are involved in an exchange with those atoms in the aromatic ring during the isomerization. The structural change and competition between isomerization and bond dissociation

ISSN:0009-4536    

DOI:10.1002/jccs.200600004

出版商:WILEY‐VCH Verlag    

年代:2006

数据来源: WILEY

摘要:

AbstractIn this account, we summarize the correlation of fluorescence anisotropy decay times with molecular size and shape of porphyrin aggregates.

ISSN:0009-4536    

DOI:10.1002/jccs.200600005

出版商:WILEY‐VCH Verlag    

年代:2006

数据来源: WILEY

摘要:

AbstractA linear quadrupole mass spectrometer operating in the third stability region [(a, q) ≈ (3, 3)] has been developed and utilized to obtain the mass spectra of multiply charged protein ions generated by electro‐spray ionization. The spectra were acquired by scanning the frequency of the quadrupole with a home‐built wide‐band power amplifier from 400 to 100 kHz at constant voltage amplitudes in the range of 100 V. A mass resolution approachingR1/2= 200 was achieved for doubly charged gramicidinSions atm/z570.5. Further improvement of the resolution is anticipated when a higher‐voltage power amplifier is

ISSN:0009-4536    

DOI:10.1002/jccs.200600006

出版商:WILEY‐VCH Verlag    

年代:2006

数据来源: WILEY

摘要:

AbstractIn view of the fact that many transition metal complexes display intense and long‐lived metal‐to‐ligand charge‐transfer emission with a large Stokes' shift, we have incorporated biotin into a series of luminescent rhenium(I), iridium(III) and ruthenium(II) polypyridine complexes to form new probes for the protein avidin. All these luminescent transition metal polypyridine biotin complexes displayed enhanced emission intensities and extended lifetimes upon binding to avidin. These changes are closely related to the hydrophobic biotin‐binding pockets of avidin and the increased rigidity of the local environment of the probes after they bind to the protein. We have exploited the characteristics of these luminescent transition metal biotin complexes in the development of vario

ISSN:0009-4536    

DOI:10.1002/jccs.200600007

出版商:WILEY‐VCH Verlag    

年代:2006

数据来源: WILEY

摘要:

AbstractPhototropin (phot) is a blue‐light receptor in plants. The protein molecule has two FMN (Flavin MonoNucleotide) binding domains named LOV (Light‐, Oxygen‐, and Voltage‐sensing), which is a subset of the PAS (Per‐Arnt‐Sim) superfamily. Illumination of the phot‐LOV domains produces a covalent C(4a) flavin‐cysteinyl adduct (S390 intermediate)viaa triplet‐excited state, which reverts to the original state in the dark. Chemical structure of the S‐H group of the reactive cysteine is important for the adduct formation, and several models have been proposed for efficient reaction. By means of Fourier‐transform infrared (FTIR) spectroscopy of the LOV2 domain ofAdiantumphytochrome3 (phy3‐LOV2), a fusion protein of phot containing the phytochrome chromophoric domain, we have studied protonation state of the reactive cysteine (Cys966). Although it was proposed that the cysteine is deprotonated in LOV domains, we observed an S‐H stretch at ˜2570 cm−1. Since phy3‐LOV2 possesses only one cysteine at position 966, this observation clearly indicates that Cys966 is protonated. While transfer reaction of proton, hydrogen, or electron has been proposed from the cysteine in the triplet‐excited state, we also detected the S‐H stretch at 2537 cm−1in the triplet‐excited state of phy3‐LOV2. This excludes the possibility of proton and hydrogen transfer reactions. These frequencies imply that the S‐H group is free from hydrogen bond in the unphotolyzed state, while it forms a strong hydrogen bond in the triplet‐excited state. We infer the hydrogen‐bonding acceptor to be the N(5) atom of FMN, and such strong interaction presumably driv

ISSN:0009-4536    

DOI:10.1002/jccs.200600008

出版商:WILEY‐VCH Verlag    

年代:2006

数据来源: WILEY

摘要:

AbstractPhotocycloaddition of furan to naphthalene derivatives having electron‐withdrawing groups at 2‐ or 2,3‐position via exciplex afforded caged‐products in high yields. The structure‐reactivity relationship can be reasonably explained by dipole‐dipole interaction between two chromophori

ISSN:0009-4536    

DOI:10.1002/jccs.200600009

出版商:WILEY‐VCH Verlag    

年代:2006

数据来源: WILEY

摘要:

AbstractReversible addition‐fragmentation chain transfer (RAFT) polymerization has been used to synthesize a star‐shaped light‐harvesting polymer comprising six diblock copolymer arms of styryl coumarin (St‐Coumarin) and methyl acrylate (MA) surrounding a ruthenium (II) trisbipyridyl energy trap core. The efficiency of excitation energy transfer from the styryl coumarin units to the Ru(II) core is increased to 90% compared to 60% for the analogous star polymer without MA blocks. The enhanced excitation energy transfer efficiency arises from the role of the MA blocks in diminishing the competitive quenching of photoexcited St‐coumarin chromophores by dithiobenzoyl polymer end groups present from the RAFT polymerization

ISSN:0009-4536    

DOI:10.1002/jccs.200600010

出版商:WILEY‐VCH Verlag    

年代:2006

数据来源: WILEY