Abstract
Harvesting long-lived free triplets in high yields by utilizing organic singlet fission materials can be the cornerstone for increasing photovoltaic efficiencies potentially. However, except ...for polyacenes, which are the most studied systems in the singlet fission field, spin-entangled correlated triplet pairs and free triplets born through singlet fission are relatively poorly characterized. By utilizing transient absorption and photoluminescence spectroscopy in supramolecular aggregate thin films consisting of Hamilton-receptor-substituted diketopyrrolopyrrole derivatives, we show that photoexcitation gives rise to the formation of spin-0 correlated triplet pair
1
(TT) from the lower Frenkel exciton state. The existence of
1
(TT) is proved through faint Herzberg-Teller emission that is enabled by vibronic coupling and correlated with an artifact-free triplet-state photoinduced absorption in the near-infrared. Surprisingly, transient electron paramagnetic resonance reveals that long-lived triplets are produced through classical intersystem crossing instead of
1
(TT) dissociation, with the two pathways in competition. Moreover, comparison of the triplet-formation dynamics in J-like and H-like thin films with the same energetics reveals that spin-orbit coupling mediated intersystem crossing persists in both. However,
1
(TT) only forms in the J-like film, pinpointing the huge impact of intermolecular coupling geometry on singlet fission dynamics.
Single-walled carbon nanotubes have unique electronic properties and the potential to advance the microelectronics industry. For these applications, semiconducting CNTs with high purity (>99.99%) and ...specific diameters or band gaps are required. High-molecular-weight conjugated polymers, especially polyfluorenes and their derivatives, have shown an exceptional ability to selectively wrap semiconducting over metallic CNTs while enriching a reduced number of diameters, whereas lower-molecular-weight analogues (<10,000 g/mol) form much less stable dispersions. Here, we report coil-conjugated-coil triblock copolymers (PS28-b-PFO16-b-PS28 and PS69-b-PFO16-b-PS69) that combine low-molecular-weight fluorene oligomers with polystyrene coils. Neither the short, conjugated oligomers nor the polystyrene coils alone have the ability to act as stable wrappers, but when combined, stable CNT dispersions are obtained with yields comparable to or exceeding those of high-molecular-weight PFO, with a semiconducting selectivity shifted to larger diameters. These results open the door to low-molecular-weight wrappers for CNT sorting and to solution-processing with wrappers with modified conformations that have the potential to alter the interactions of CNTs with their environment.
Diketopyrrolopyrrole (DPP)-based molecular semiconductors exhibit intriguing optical and charge transport properties. Herein, we rationally design a series of electronically identical but ...structurally distinct Hamilton receptor (HR)-based supramolecular assembly of DPP. The HR endows supramolecular assemblies via hydrogen bonding with enhanced structural ordering and excitonic couplings. The mechanism of supramolecular self-assembly was probed by diffusion ordered spectroscopy (DOSY) nuclear magnetic resonance (NMR) and solid-state IR spectroscopy studies. We investigated the morphology of self-assembly, photophysical and electrochemical properties and compared them with the identical DPP molecular structures without HRs. The microstructure of self-assembly was probed with atomic force microscopy in thin films. Subsequently, the influence of solid-state packing was studied by single-crystal X-ray diffraction. The single-crystal structure of HR-TDPP-C20 reveals slipped stack arrangements between the two neighboring chromophores with π–π stacking distance and slip angle of 3.55 Å and 35.4°, respectively. Notably, the slight torsional angle of 1° between thiophene and lactam rings and small π–π stacking distance suggest a significant intermolecular coupling between thiophene (D) and lactam (A) rings. This intramolecular coupling between two π–π chromophore stacks manifests in their optical properties. In this manuscript, we report rational design and synthesis of supramolecular self-assembly of DPP with a collection of compelling structural and optical properties.
The oscillation of chemical bonds in molecular semiconductors plays a key role in fragmenting the electric conducting pathways due to the large fraction of free volumes, acting as “trap sites” for ...charge carriers. Incorporating directional noncovalent chemical bonds between the monomeric unit in organic semiconductors is an excellent approach to reducing thermally induced structural fluctuations, resulting in a decrease in a trap densities. In this work, we utilize noncovalent interactions in diketopyrrolopyrrole (DPP)-based supramolecular assembled systems to enhance or tune the photoconductivity and charge transport properties. Infinitesimal molecular design by substituting different side chains and introducing intramolecular dihedral angles leads to a notable difference in solid-state packing, transient photoconductivity, and thin film morphology. Grazing incidence wide-angle X-ray scattering, and thin film X-ray diffraction measurements reveal that the packing order is enhanced for hexyl substituted DPP derivatives, resulting in high intrinsic charge carrier mobility of ∑μ = 1.7 cm2 V–1 s–1. At the microscopic level, electron microscopy reveals that the unique self-assembly remarkably improves the structural order via directional hydrogen bonding. These findings exemplify that the supramolecular self-assembly strategy via hydrogen bonding networks is an efficacious way to reduce the molecular vibration and structural defects in molecular semiconductors and ameliorate the performance in optoelectronic devices.
Organic solar cells (OSCs) fabricated from ternary blend thin film absorbers are designed to maximize the range of absorption in the solar spectrum and thus increase the short-circuit current density ...(J SC) of the device. Herein, we report OSCs formed with two different compositions of ternary blend thin films comprising two electron donors and one acceptor, namely, PTB7-Th/PCDTBT/IT4F and PTB7-Th/PBDB-T/IT4F. We evaluate the role of Förster resonance energy transfer (FRET) and blend morphology to achieve composition-dependent device performance. We observed ≥10% increment in J SC for both the ternary blends as compared to that for the PTB7-Th:IT4F binary blend, resulting in an enhanced power conversion efficiency (PCE) up to 10.34% for the PTB7-Th:PBDB-T:IT4F blend. We provide evidence that the two foremost parameters that control the PCE are blend morphology and FRET between donor components. The improved exciton generation rate for PCDTBT-based ternary blends was achieved, suggesting effective contribution of FRET toward enhanced device photocurrent, whereas the PBDB-T-based ternary blend excelled mainly due to suppressed carrier recombination as a result of favorable orientation with PTB7-Th/IT4F.
Abstract
Previously, our laboratory demonstrated that a deregulated E2F5/p38/SMAD3 axis was associated with uncontrolled cellular proliferation in prostate cancer (PCa). Here, we investigate the role ...of E2F5 in PCa in further details. RNAi-mediated E2F5 knockdown and pathway-focused gene expression profiling in PC3 cells identified TFPI2 as a downstream target of E2F5. Manipulation of E2F5 expression was also found to alter MMP-2 and MMP-9 levels as detected by Proteome Profiler array, western blot and reverse transcription coupled quantitative polymerase chain reaction Site-directed mutagenesis, dual-luciferase assays and chromatin immunoprecipitation with anti-E2F5-IgG coupled with qPCR confirmed recruitment of E2F5 on TFPI2, MMP-2 and MMP-9 promoters. RNAi-mediated knockdown of E2F5 expression in PC3 caused a significant alteration of cell migration while that of TFFI2 resulted in a modest change. Abrogation of E2F5 and TFPI2 expression was associated with significant changes in the gelatinolytic activity of active forms of MMP-2 and MMP-9. Moreover, E2F5, MMP-2 and MMP-9 levels were elevated in biopsies of PCa patients relative to that of benign hyperplasia, while TFPI2 expression was reduced. MMP-9 was coimmunoprecipitated with anti-TFPI2-IgG in PCa tissue samples suggesting a direct interaction between the proteins. Finally, artemisinin treatment in PC3 cells repressed E2F5 along with MMP-2/MMP-9 while triggering TFPI2 expression which alleviated PC3 aggressiveness possibly through inhibition of MMP activities. Together, our study reinstates an oncogenic role of E2F5 which operates as a dual-function transcription factor for its targets TFPI2, MMP-2 and MMP-9 and promotes cellular invasiveness. This study also indicates a therapeutic potential of artemisinin, a natural compound which acts by correcting dysfunctional E2F5/TFPI2/MMP axis in PCa.
Besides cell-cycle control, E2F5 modulates cell migration by divergently regulating TFPI2 and MMP-2/-9 expressions in PCa. E2F5 overexpression causes a higher MMP activity by decreasing TFPI2 level. Artemisinin dampens PC3 cell aggressiveness by repressing E2F5 and thus correcting aberrant TFPI2–MMP interaction.
Fowl Pox Viruses (FPV) infect chickens and turkeys giving rise to pock lesions on various body parts like combs, wattles, legs, shanks, eyes, mouth etc. The birds, affected with FPV, also show anemia ...and ruffled appearance which are clinical symptoms of Reticuloendotheliosis. Interestingly, the field strains of FPV are integrated with the provirus of Reticuloendotheliosis Virus (REV). Due to this integration, the infected birds, upon replication of FPV, give rise to free REV virions, causing severe immunosuppression and anemia. Pox scabs, collected from the infected birds, not only show positive PCR results upon performing FPV-specific 4b core protein gene PCR but also show positive results for the PCR of REV-specific env gene and FPV-REV 5'LTR junction. Homogenized suspension of the pock lesions, upon inoculating to the Chorio-allantoic Membrane (CAM) of 10 days old specific pathogen-free embryonated chicken eggs, produces characteristic pock lesions in serial passages. But the lesions also harbor REV mRNA or free virion, which can be identified by performing REV-specific env gene PCR using REV RNA from FPV-infected CAMs. The study suggests successful replication and availability of REV mRNA and free virion alongside the FPV virus, although the CAM is an ill-suited medium for any retroviral (like REV) growth and replication.
