Transient Absorption Imaging of P3HT:PCBM Photovoltaic Blend: Evidence For Interfacial Charge Transfer State

Solution-processed bulk heterojunction (BHJ) based on electron-donor (D) polymer and acceptor (A) fullerene is a promising technology for organic photovoltaics. Geminate charge recombination is regarded as one of the main loss mechanisms limiting device performances. This stems from the dynamics of the initial charge transfer state (CTS), which depend on the blend morphology, the molecular conformation, and the energetics of the D:A interface. Here we study the photophysics of a crystalline phase-separated blend of regioregular poly(3-hexylthiophene) (P3HT) with [6,6]-phenyl-C₆₁-butyric acid methyl ester (PCBM) with a coarsened morphology, by mapping the transient absorption signal with submicrometer space and subpicosecond time resolution. At the P3HT:PCBM interface, we detect a long-lived photoinduced dynamic that we assign to a peculiar coherent CTS forming in ∼10 ps, not affected by geminate recombination and characterized by a different polarization with respect to the one in the usual polydispersed blend. Quantum chemical calculations on supramolecular P3HT:PCBM complexes confirm the presence of low-lying and highly polarized CTS, validating the experimental findings

Trapping Dynamics in Photosystem I‑Light Harvesting Complex I of Higher Plants Is Governed by the Competition Between Excited State Diffusion from Low Energy States and Photochemical Charge Separation

The dynamics of excited state equilibration and primary photochemical trapping have been investigated in the photosystem I-light harvesting complex I isolated from spinach, by the complementary time-resolved fluorescence and transient absorption approaches. The combined analysis of the experimental data indicates that the excited state decay is described by lifetimes in the ranges of 12–16 ps, 32–36 ps, and 64–77 ps, for both detection methods, whereas faster components, having lifetimes of 550–780 fs and 4.2–5.2 ps, are resolved only by transient absorption. A unified model capable of describing both the fluorescence and the absorption dynamics has been developed. From this model it appears that the majority of excited state equilibration between the bulk of the antenna pigments and the reaction center occurs in less than 2 ps, that the primary charge separated state is populated in ∼4 ps, and that the charge stabilization by electron transfer is completed in ∼70 ps. Energy equilibration dynamics associated with the long wavelength absorbing/emitting forms harbored by the PSI external antenna are also characterized by a time mean lifetime of ∼75 ps, thus overlapping with radical pair charge stabilization reactions. Even in the presence of a kinetic bottleneck for energy equilibration, the excited state dynamics are shown to be principally trap-limited. However, direct excitation of the low energy chlorophyll forms is predicted to lengthen significantly (∼2-folds) the average trapping time

Coherent Longitudinal Acoustic Phonons in Three-Dimensional Supracrystals of Cobalt Nanocrystals

We use broadband picosecond acoustics to detect longitudinal acoustic phonons with few-gigahertz frequency in three-dimensional supracrystals (with face-centered cubic lattice) of 7 nm cobalt nanocrystal spheres. In full analogy with atomic crystals, where longitudinal acoustic phonons propagate with the speed of sound through coherent movements of atoms of the lattice out of their equilibrium positions, in these supracrystals atoms are replaced by (uncompressible) nanocrystals and atomic bonds by coating agents (carbon chains) that act like mechanical springs holding together the nanocrystals. By repeating the measurements at different laser angles of incidence it was possible to accurately determine both the index of refraction of the supracrystal (<i>n</i> = 1.26 ± 0.03) and the room-temperature longitudinal speed of sound (<i>v</i>_s= 1235 ± 12 m/s), which is quite low due to the heavy weight of the spheres (with respect to atoms in a crystal) and the soft carbon chains (with respect to atomic bonds). Interestingly, the speed of sound inside the supracrystal was found to dramatically increase by decreasing the sample temperature due to a change in the stiffness of the dodecanoic acid chains which coat the Co nanocrystals

Dynamic Microscopy Study of Ultrafast Charge Transfer in a Hybrid P3HT/Hyperbranched CdSe Nanoparticle Blend for Photovoltaics

We present a spectroscopic investigation on a new hyperbranched cadmium selenide nanocrystals (CdSe NC)/poly­(3-hexylthiophene) (P3HT) blend, a potentially good active component in hybrid photovoltaics. Combined ultrafast transient absorption spectroscopy and morphological investigations by means of an ultrafast confocal microscope reveal a strong influence of the complex local structure on the photogenerated carrier dynamics. In particular, we map the electron-transfer process across the hybrid NC/polymer interface, and we reveal that charge separation occurs through a preferential pathway from the CdSe nanobranches to the P3HT chains. Efficient charge generation at the distributed heterojunction is also confirmed by scanning kelvin probe force microscopy measurements

Additional file 2: of Lipid accumulation in human breast cancer cells injured by iron depletors

FACS analysis of cell cycle. (PPTX 200 kb

Additional files 3: of Lipid accumulation in human breast cancer cells injured by iron depletors

Reports of statistical results, specifically up- and down- regulated proteins in DFO- or Dp44mT-treated cells with respect to control. Down-regulated in DFO- treated cells versus untreated. (XLS 618 kb

Additional file 4: of Lipid accumulation in human breast cancer cells injured by iron depletors

Up-regulated in DFO-treated cells versus untreated. (XLS 375 kb

Additional file 7: of Lipid accumulation in human breast cancer cells injured by iron depletors

Ingenuity Pathway analysis revealing the pathways significantly changed after the DFO/Dp44mT treatments. (PPTX 397 kb

Additional file 5: of Lipid accumulation in human breast cancer cells injured by iron depletors

Down-regulated in Dp44mT-treated cells versus untreated. (XLS 721 kb

Additional file 6: of Lipid accumulation in human breast cancer cells injured by iron depletors

Up-regulated in Dp44mT-treated cells versus untreated. Differential expression was considered as significant if (1) a protein was present only in untreated or treated cells or (2) its normalised (according to the LFQ algorithm) intensity resulted in a statistical difference, as calculated by the welch’s t-test (t-test cut-off at p value = 0.0167). These data have been deposited to the ProteomeXchange Consortium ( http://proteomecentral.proteomexchange.org/cgi/GetDataset ) via the PRIDE (Vizcaíno et al., 2016 PubMed ID: 26527722) partner repository with the dataset identifier PXD007595. (XLS 537 kb