Effects of solvent on fabrication of polymeric light emitting devices

Xiao, Steven; Qiu, Chun; Jin, Eugene; Chen, Yi; Louis, P.; Qiu, S. N.; Zhu, Weiliang; Nguyên, My T.; Shih, I.

doi:10.1016/j.matlet.2004.11.011

Cited by 12 publications

(5 citation statements)

References 5 publications

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“…Aggregation emission is well-known for other conjugated polymers such as MEH-PPV, 36 and it is also reported in polyfluorene. 37 It is solvent- 38 and process-dependent, and it may be a general phenomenon in conjugated polymers.…”

Section: Resultsmentioning

confidence: 99%

Green Emission from End-Group-Enhanced Aggregation in Polydioctylfluorene

et al. 2005

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Green emission in polyfluorenes (PFs) has been attributed to aggregation or excimer emission, but recently it was reassigned as an on-chain fluorenone defect. We show here that, in dialkyl-substituted PFs that is hydrogen-free at the 9'-position of the fluorene, blue emission with very weak green emission is observed from end-capped polydioctylfluorene (PFO) for both photoluminescence and electroluminescence spectra, while the low-energy green emission at 507 nm is very pronounced only in uncapped PFO (PFOun). The facts that there is no detectable infrared absorption at around 1721 cm(-1) due to >C=O stretching vibration in PFOun and no charge-trapping occurring in the light-emitting device from PFOun are in contrast with those found in the literature-reported copolymers with fluorenone units, which have detectable infrared absorption at 1721 cm(-1) and charge-trapping in devices. We found that this green emission at around 507 nm originates from the end-group-enhanced aggregation by use of UV-vis absorption, photoexcitation spectra, and steady-state photoluminescent and electroluminescent spectra. The end-group-enhanced aggregation is much weaker in other PFs with less-ordered structures.

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Section: Resultsmentioning

confidence: 99%

Green Emission from End-Group-Enhanced Aggregation in Polydioctylfluorene

et al. 2005

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“…The side-chain engineering of the conjugated polymers including the side-chain length, the branching point position, and bulkiness − can strongly impact chain conformation transformation, molecular backbone coplanarity, the quality of molecular packing, and hole mobility as well as interchain interactions and π-planar distance, which can contribute to the excimer formation in the excited state . PF β-conformation formation is strongly dependent on the structure of side chain. , Monkman had found that only PFs with a linear side chain could form β conformation. , Besides, the change of side-chain length will directly take effect on the solution dynamics process.…”

Section: Introductionmentioning

confidence: 99%

Polyfluorene (PF) Single-Chain Conformation, β Conformation, and Its Stability and Chain Aggregation by Side-Chain Length Change in the Solution Dynamic Process

Liu

Zhang

et al. 2018

J. Phys. Chem. C

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The effects of alkyl side-chain length with different carbon atom number, called poly(9,9di-hexlyfluorene) (PF6), poly(9,9-diheptylfluorene) (PF7), poly(9,9-dioctylfluorene) (PF8), poly(9,9-dinonylfluorene) (PF9), and poly(9,9-didecylfluorene) (PF10), on the polyfluorene (PF) single-chain conformation, β conformation, and its stability and chain aggregation in the solution dynamic process were systematically investigated by dynamic/static light scattering, UV–vis absorption spectra, photoluminescence spectra, and scanning electron microscopy. β conformation was the low-energy chain conformation, and its characteristic peak was at 437, 427, and 428 nm in the UV–vis spectrum of PF8, PF9, and PF10, respectively. It was interestingly found that the shape parameters (R g/R h) (i.e., ratio of radius of gyration (R g) and hydrodynamic radius (R h)) of PF single chains in toluene solution showed an odd–even property with the increase in side-chain length, which revealed that PF chains with even carbon atoms were more rigid than those with odd carbon atoms. The highest contents of β conformation were all ∼42% in PF8, PF9, and PF10 toluene/ethanol mixed solutions, but PF8 most easily formed the β conformation, PF9 followed, and PF10 was last. It was first found that the β-conformation formation and content were strongly connected to the chain packing density but not to aggregation size. High chain packing density was more advantageous to β-conformation formation; it had been well proved by static fractal dimension (d f), reflecting the compactness of chain aggregation (i.e., chain packing density) and the chain self-similarity, and calculated by exponential law from SLS. Besides, it was also found that the β-conformation content could be stabilized at the maximum value range (42%) in the high ethanol content (80%) and independent of the side-chain length even after placing for 21 days, whereas in lower ethanol content (30 and 40%), the β-conformation content could also be stabilized in two different time stages. The conclusions are significant to understand deeply the solution dynamics process of film formation based on condensed matter physics of the conjugated polymer to control its condensed matter structure to achieve photoelectric devices with high carrier mobility, stability, and efficiency.

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“…The generation of hydroxyl radical was measured by the method of Gutteridge, (1992) [19]. Calf thymus DNA (100 µg) was used as a substrate and malondialdehyde generated from deoxyribose radicals was assayed by recording the absorbance at 532 nm.…”

Section: Measurement Of Hydroxyl Radicalmentioning

confidence: 99%

Amelioration of 5-FU induced toxicity by using RF under white light: An in vitro study

2015

Integr Pharm Toxicol Gentoxicol

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5-Fluorouracil (5-FU) is a potent photosensitizer used in colon and rectal cancer. A major drawback associated with 5-FU chemotherapy is its toxicity towards normal tissues by generation of reactive oxygen species (ROS). Riboflavin (RF) is a well known photosensitizer and has no adverse effect. Previously, we have reported the ameliorative effect of photoilluminated RF in case of cisplatin induced toxicity both in vitro and in vivo. Accordingly, we have extended our work and have tried to demonstrate with the help of carbonyl assay that the rise in the carbonyl groups reached a certain level at particular concentration of 5-FU and after which no increase in oxidative damage of protein was observed. However, on addition of RF in the reaction the photo excitation of 5-FU was inhibited at lower concentration. Moreover, plasmid nicking also elucidate that the nicking activity is minimally affected by the incorporation of 5-FU at higher concentration in the reaction and on addition of RF at lower concentration of 5-FU the nicking of plasmid was masked. Furthermore, on incubation of lymphocytes with lower concentration of 5-FU in presence of RF as compared to 5-FU alone led to a significant decrease in tail length of DNA when measured by comet assay. Thus, study show that 5-FU behaves in a biphasic manner, at lower concentrations of the drug in which RF inhibits the photoactivation leading to quenching in the ROS generation while at higher concentration the drug dimerization is thought to be the plausible reason for the observed results. In conclusion, our results suggest that 5-FU induced toxicity may be blunted by using RF under white light.

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Effects of solvent on fabrication of polymeric light emitting devices

Cited by 12 publications

References 5 publications

Green Emission from End-Group-Enhanced Aggregation in Polydioctylfluorene

Green Emission from End-Group-Enhanced Aggregation in Polydioctylfluorene

Polyfluorene (PF) Single-Chain Conformation, β Conformation, and Its Stability and Chain Aggregation by Side-Chain Length Change in the Solution Dynamic Process

Amelioration of 5-FU induced toxicity by using RF under white light: An in vitro study

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