By developing a wide-field scheme for spectral measurement and implementing photoswitching, we synchronously obtained the fluorescence spectra and positions of ∼10(6) single molecules in labeled cells in minutes, which consequently enabled spectrally resolved, 'true-color' super-resolution microscopy. The method, called spectrally resolved stochastic optical reconstruction microscopy (SR-STORM), achieved cross-talk-free three-dimensional (3D) imaging for four dyes 10 nm apart in emission spectrum. Excellent resolution was obtained for every channel, and 3D localizations of all molecules were automatically aligned within one imaging path.

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We present here the first room-temperature 2D electronic spectroscopy study of energy transfer in the plant light-harvesting complex II, LHCII. Two-dimensional electronic spectroscopy has been used to study energy transfer dynamics in LHCII trimers from the chlorophyll b Qy band to the chlorophyll a Qy band. Observing cross-peak regions corresponding to couplings between different excitonic states reveals partially resolved fine structure at the exciton level that cannot be isolated by pump-probe or linear spectroscopy measurements alone. Global analysis of the data has been performed to identify the pathways and time constants of energy transfer. The measured waiting time (Tw) dependent 2D spectra are found to be composed of 2D decay-associated spectra with three timescales (0.3 ps, 2.3 ps and >20 ps). Direct and multistep cascading pathways from the high-energy chlorophyll b states to the lowest-energy chlorophyll a states have been resolved occurring on time scales of hundreds of femtoseconds to picoseconds.

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In this work, CeO 2 nanoparticle decorated graphite felts (CeO 2 /GFs) were prepared by a facile precipitation method. The corresponding CeO 2 /GF composites containing different contents of CeO 2 , i.e. 0.1, 0.2, 0.3, 0.5 wt% were synthesized individually as electrodes for vanadium redox flow battery (VRFB) application. Scanning electron microscopy and X-ray diffraction analysis indicated the homogeneous dispersion of CeO 2 nanoparticles on GF. The cyclic voltammetry results revealed that the CeO 2 /GFs exhibited higher activity and better reversibility towards the VO 2+ /VO 2 + redox reaction compared with the pristine GF.Among all the electrodes, 0.2 wt% CeO 2 /GF demonstrated the best electrochemical properties, thus nominating CeO 2 content of 0.2 wt% as an optimum content. The VRFB single cell tests indicated that 0.2 wt% CeO 2 /GF showed the highest energy efficiency of 64.7% at the current density of 200 mA cm À2 , which was significantly higher than that of the pristine GF (53.9%). Furthermore, the cycle life test of a VRFB single cell demonstrated the outstanding stability of the CeO 2 /GFs electrode.

Ultrafast two-dimensional electronic spectroscopy has been used to study the spectral diffusion of the Qy transition of chlorophyll a in methanol. The two time frequency-fluctuation correlation function (FFCF) of the transition has been measured using the center line slope method, together with optimized fitting of the linear spectrum. The FFCF was measured to decay over four time scales. The three fastest time constants of which were measured to be ∼65 fs, ∼0.5 ps, and ∼7 ps. These are assigned as the inertial component of solvation and spectrally diffusive solvation processes respectively. The fourth time constant (>1 ns) may be attributed to the chromophore structural inhomogeneity.

By recording both the images and emission spectra of thousands of single fluorescent molecules stochastically generated from the ring-opening reaction of a spiropyran, we provide mechanistic insights into its multipath reaction pathways. Through statistics of the measured single-molecule spectra, we identify two spectrally distinct isomers, presumably TTC and TTT cis-trans isomers, for the open-ring merocyanine product, and discover a strong solvent polarity-dependence for the relative population of the two isomers. From single-molecule spectral time traces, we further examine isomerization between the two product merocyanine isomers, as well as their ring-closure reaction back to the spiropyran form.

We present the theoretical details and experimental demonstration of fifth-order three-dimensional (3D) electronic spectroscopy using a pump-probe beam geometry. This is achieved using a pulse shaper and appropriate phase cycling schemes. We show how 8-step and 27-step phase cycling schemes can measure purely absorptive 3D spectra as well as 3D spectra for the individual fifth-order processes that contribute to the purely absorptive spectrum. 3D spectra as a function of two separate controllable waiting time periods can be obtained. The peak shapes and positions of the peaks in the experimental measurement correspond well to theory.