The Origin of Green Emission in Polyfluorene‐Based Conjugated Polymers: On‐Chain Defect Fluorescence

Romaner, Lorenz; Pogantsch, Alexander; Freitas, P. Scandiucci de; Scherf, Ullrich; Gaal, Martin; Zojer, Egbert; List, Emil

doi:10.1002/adfm.200304360

Cited by 266 publications

(179 citation statements)

References 27 publications

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“…Indeed, these results show quite different behaviour compared to the effects observed previously on fluorene-based polymers, which are reported to possess red-shifting spectra mainly due to oxidative degradation after such treatment. [29][30][31][32][33][34] Our polymers, except PF, contain extra cross-linking groups, which are able to supplement the emission spectra with some red-shifted component in a positive manner when kept at a controlled level. This additional contribution on the red side of the visible spectrum is proven to be not only because of oxidative keto defect formation, but mainly due to the cross-linkable azide and bromide species on PFA and PFB, respectively.…”

Section: -33mentioning

confidence: 99%

On the origin of high quality white light emission from a hybrid organic/inorganic light emitting diode using azide functionalized polyfluorene

et al. 2008

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High quality white light generation with high colour rendering index (CRI) was achieved by integrating a cross-linkable azide functionalized polyfluorene derivative, namely poly[(9,9-dihexylfluorene)-co-alt-(9,9-bis(6-azidohexyl) fluorene)] (PFA), as a down-converting fluorescent material on the inorganic n-UV InGaN/GaN LED platform. For comparison, two other polyfluorene based polymers, namely poly[(9,9-dihexylfluorene)-co-alt-(9,9-bis(6-bromohexyl) fluorene)] (PFB) and poly[9,9-dihexyl-9H-fluorene] (PF), were tested for white light generation. While PFA and PF both led to white light generation, PFB fell out of the white region on the chromaticity diagram. Compared to PFA, both of the control groups (PF and PFB) exhibited much lower CRI. To gain a better insight into the mechanisms playing a key role for the generation of such high quality white light in PFA, all of these polymers were further subjected to a series of experiments such as controlled exposure to heat at 220 °C for 2 h under Ar and in air. The polymers PFA and PFB, which include cross-linkable groups, produced broad emission spectra in the region of 430-650 nm upon annealing in the absence of oxygen under Ar atmosphere while almost no change was observed in the emission spectrum of PF without any cross-linkable groups. PFA undergoes cross-linking through the decomposition of azide leading to reactive nitrene species, whereas in PFB cross-linking probably occurs via debromination. This result clearly proved that the broadening can not be attributed only to photo or thermal oxidation, but it is also due to cross-linking. PFA was also exposed to n-UV light from the InGaN/GaN LED to investigate its photostability. In these experiments, the spectral changes in absorbance and emission properties and thermal transitions of these polymers were monitored by FT-IR, UV-Vis and fluorescent spectrometry, and differential scanning calorimetry (DSC). These experiments indicated that PFA provides high quality white light opportunely via cross-linking and remains stable once cross-linking is formed in a solid film. © 2008 The Royal Society of Chemistry

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Section: -33mentioning

confidence: 99%

On the origin of high quality white light emission from a hybrid organic/inorganic light emitting diode using azide functionalized polyfluorene

et al. 2008

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“…Fourier transform infrared (FTIR) spectroscopy has revealed that fluorenone defects, formed on degradation of PFs, are related to the intensity of the low-energy emission band (15,19,(31)(32)(33)(34)(35)(36)(37)(38). The idea that fluorenones could be responsible for the green light emission was substantiated by the synthesis of poly-and oligofluorenes containing a precise number of fluorenone moieties that exhibit green emission, even in dilute solution (24,33,(39)(40)(41). It is generally accepted that keto defects are generated in PF-type polymers by the oxidation of monoalkylfluorenes (42) and are extremely difficult to eliminate from the monomer feed and, therefore, are incorporated into the polymer.…”

Section: Resultsmentioning

confidence: 99%

Luminescent properties of a novel fluorene organic material

Lou

Qian

et al. 2008

Luminescence

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The photo-physical properties of 6,6′-(9H-fluoren-9,9-diyl)bis(2,3-bis(9,9-dihexyl-9H-fluoren-2-yl)quinoxaline) (BFLBBFLYQ) and its blend doped with N′-biphenyl-N,N′-bis-(3-methylphenyl)-1,1′-biphenyl-4,4′-diamine (TPD) were investigated. The absorption, photoluminescence (PL) and electroluminescence (EL) properties of pristine BFLBBFLYQ and blend in solution and spin-coated film are outlined, including a discussion of charge-transfer (CT) exciplex emission of BFLBBFLYQ:TPD blend in the solid state. The luminescent properties of BFLBBFLYQ films using different deposition processes were studied. It was found that the low-energy emission bands at 530-570 nm appeared in the PL spectra of BFLBBFLYQ evaporated films in ultra-high vacuum. Also, the low-energy band was the exclusive emission in the EL spectra of BFLBBFLYQ films.

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“…With further development, combined with temporal and spectral characterization, DNA-PLM can feasibly identify highly specific molecular "fingerprints," leading to in situ label-free sequencing of the genome. Additionally, topological and chemical alterations in highly condensed DNA strains can result in various additional photophysical interactions, as has been studied in polymer molecules, including energy transfer (55-57), ground-or excited-state aggregate formation (58,59), and charge transfer (60). These photophysical processes can significantly modify the molecular optical properties, allowing us to further capture functional information about the chromatin nanoarchitecture.…”

Section: Resultsmentioning

confidence: 99%

Superresolution intrinsic fluorescence imaging of chromatin utilizing native, unmodified nucleic acids for contrast

Dong

Almassalha

Stypula-Cyrus

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

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Visualizing the nanoscale intracellular structures formed by nucleic acids, such as chromatin, in nonperturbed, structurally and dynamically complex cellular systems, will help expand our understanding of biological processes and open the next frontier for biological discovery. Traditional superresolution techniques to visualize subdiffractional macromolecular structures formed by nucleic acids require exogenous labels that may perturb cell function and change the very molecular processes they intend to study, especially at the extremely high label densities required for superresolution. However, despite tremendous interest and demonstrated need, label-free optical superresolution imaging of nucleotide topology under native nonperturbing conditions has never been possible. Here we investigate a photoswitching process of native nucleotides and present the demonstration of subdiffraction-resolution imaging of cellular structures using intrinsic contrast from unmodified DNA based on the principle of single-molecule photon localization microscopy (PLM). Using DNA-PLM, we achieved nanoscopic imaging of interphase nuclei and mitotic chromosomes, allowing a quantitative analysis of the DNA occupancy level and a subdiffractional analysis of the chromosomal organization. This study may pave a new way for label-free superresolution nanoscopic imaging of macromolecular structures with nucleotide topologies and could contribute to the development of new DNA-based contrast agents for superresolution imaging.superresolution fluorescence microscopy | label-free imaging | nucleic acids | chromatin topology | chromosome A dvances in genomics and molecular biology over the past decades revolutionized our knowledge of biological systems. Despite our expanded understanding of biological interactions, there continues to be a limited understanding of these complex molecular processes in nonperturbed, structurally and dynamically complex cellular systems (1). As such, it is of critical importance to develop methods that allow direct visualization of nanoscale structures where these processes take place in their native states. Recently, superresolution fluorescence microscopy techniques, including stimulated emission depletion microscopy, structured illumination microscopy, and photon localization microscopy (PLM), such as photoactivated localization microscopy and stochastic optical reconstruction microscopy (STORM), have extended the ultimate resolving power of optical microscopy far beyond the diffraction limit (2-6), facilitating access to the organization of cells at the nanoscale by optical means. Although superresolution imaging of biological structures using labeled proteins has been well documented due to a wide range of methodologies that provide desirable labeling properties (7,8), and despite tremendous interest and demonstrated need, there are few nanoscopic methods to image macromolecular structures formed by nucleic acids due to constraints in labeling (9-14). Likewise, the limited techniques that currently exist cannot ...

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The Origin of Green Emission in Polyfluorene‐Based Conjugated Polymers: On‐Chain Defect Fluorescence

Cited by 266 publications

References 27 publications

On the origin of high quality white light emission from a hybrid organic/inorganic light emitting diode using azide functionalized polyfluorene

On the origin of high quality white light emission from a hybrid organic/inorganic light emitting diode using azide functionalized polyfluorene

Luminescent properties of a novel fluorene organic material

Superresolution intrinsic fluorescence imaging of chromatin utilizing native, unmodified nucleic acids for contrast

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