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1.
R Soc Open Sci ; 6(6): 190196, 2019 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-31312489

RESUMO

A novel aromatic diamine containing pyridyl side group, 4-pyridine-4,4-bis(3,5-dimethyl-5-aminophenyl)methane (PyDPM), was successfully synthesized via electrophilic substitution reaction. The polyimides (PIs) containing pyridine were obtained via the microwave-assisted one-step polycondensation of the PyDPM with pyromellitic dianhydride (PMDA), 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA), 3,3',4,4'-diphenylether tetracarboxylic dianhydride (ODPA) and 4,4'-(hexafluoroisopropylidene)diphthalic anhydride (6FDA). Contrarily to the reported similar PIs, these PIs exhibit much higher thermal stability or heat resistance, i.e. high glass transition temperatures (T gs) in the range of 358-473°C, and the decomposition temperatures at 5% weight loss over 476°C under nitrogen. They can afford flexible and strong films with tensile strength of 82.1-93.3 MPa, elongation at break of 3.7%-15.2%, and Young's modulus of 3.3-3.8 GPa. Furthermore, The PI films exhibit good optical transparency with the cut-off wavelength at 313-366 nm and transmittance higher than 73% at 450 nm. The excellent thermal and optical transmittance can be attributed to synthesis method and the introduction of pyridine rings and ortho-methyl groups. The inherent viscosities of PIs via one-step method were found to be 0.58-1.12 dl g-1 in DMAc, much higher than those via two-step method. These results indicate these PIs could be potential candidates for optical substrates of organic light emitting diodes (OLEDs).

2.
ACS Appl Mater Interfaces ; 7(48): 26405-13, 2015 Dec 09.
Artigo em Inglês | MEDLINE | ID: mdl-26422296

RESUMO

We present an investigation of deep-blue fluorescent polymer light-emitting diodes (PLEDs) with a novel functional 1,3,5-triazine core material (HQTZ) sandwiched between poly(3,4-ethylene dioxythiophene):poly(styrene sulfonic acid) layer and poly(vinylcarbazole) layer as a hole injection layer (HIL) without interface intermixing. Ultraviolet photoemission spectroscopy and Kelvin probe measurements were carried out to determine the change of anode work function influenced by the HQTZ modifier. The thin HQTZ layer can efficiently maximize the charge injection from anode to blue emitter and simultaneously enhance the hole mobility of HILs. The deep-blue device performance is remarkably improved with the maximum luminous efficiency of 4.50 cd/A enhanced by 80% and the maximum quantum efficiency of 4.93%, which is 1.8-fold higher than that of the conventional device without HQTZ layer, including a lower turn-on voltage of 3.7 V and comparable Commission Internationale de L'Eclairage coordinates of (0.16, 0.09). It is the highest efficiency ever reported to date for solution-processed deep-blue PLEDs based on the device structure of ITO/HILs/poly(9,9-dialkoxyphenyl-2,7-silafluorene)/CsF/AL. The results indicate that HQTZ based on 1,3,5-triazine core can be a promising candidate of interfacial materials for deep-blue fluorescent PLEDs.

3.
ACS Appl Mater Interfaces ; 6(14): 11001-6, 2014 Jul 23.
Artigo em Inglês | MEDLINE | ID: mdl-25003531

RESUMO

Inverted-type polymer light-emitting diodes with Au nanoparticles modified ITO cathode has exhibited improved brightness from 5900 to 15,000 cd m(-2) (1.5-fold enhancement) and enhanced luminous efficiency from 4.4 to 10.5 cd A(-1) (1.4-fold enhancement), when greenish emissive polymer-P-PPV was applied as active layer. Both the experimental and theoretical results show that it is mainly attributed to effective overlapping between local surface plasmon resonance induced by Au nanopartices and excitons quenching region at ZnO/P-PPV interface, which makes originally electrode-quenched excitons emissive and increases excitons efficiency.

4.
Chem Asian J ; 7(9): 2126-32, 2012 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-22689560

RESUMO

A new series of monoammonium-based organic electrolytes with the tetrafluoroborate (BF(4)(-)) counteranion have been synthesized. Replacing the pendant ethyl groups in the fluorenyl unit with 4-ethoxyphenyl groups dramatically improves both solubility and morphological stability. The characterization of the alcohol-processable amorphous ionic compounds as an electron-injection layer in organic light-emitting diodes (OLEDs) reveals that the organic electrolyte that comprises a rigid linear-conjugated unit provides better device performance, with respect to its counterpart containing a branched bulky moiety. The capability of these compounds to facilitate electron injection from air-stable aluminum metal is preliminarily discussed on the basis of the investigations of the electron-only devices and photovoltaic experiments.

5.
J Hazard Mater ; 163(2-3): 843-7, 2009 Apr 30.
Artigo em Inglês | MEDLINE | ID: mdl-18718711

RESUMO

The role of dissolved oxygen, and of active species generated by photo-induced reactions with oxygen, in the photocatalytic degradation of phenol was investigated using polymer [poly-(fluorene-co-thiophene) with thiophene content of 30%, so-called PFT30] sensitized TiO2 (PFT30/TiO2) under visible light irradiation. The photoluminescent (PL) quantum yield of PFT30/TiO2 was about 30% of that of PFT30/Al(2)O(3), proving that electron transfer took place between the polymer and TiO2. The result that photocatalytic degradation of phenol was almost stopped when the solution was saturated with N(2) proved the importance of O(2). Addition of NaN(3), an effective quencher of singlet oxygen ((1)O(2)), caused about a 40% decrease in the phenol degradation ratio. Addition of alcohols caused about a 60% decrease in the phenol photodegradation ratio, indicating that the hydroxyl radicals (OH), whose presence was confirmed by electron spin resonance (ESR) spectroscopy, was the predominant active species in aqueous solution. In anhydrous solution, singlet oxygen ((1)O(2)) was the predominant species. These results indicate that oxygen plays a very important role in the photocatalytic degradation of phenol.


Assuntos
Fenol/química , Processos Fotoquímicos , Espécies Reativas de Oxigênio/química , Radical Hidroxila , Luz , Fenol/efeitos da radiação , Polímeros , Oxigênio Singlete , Titânio
6.
Chem Commun (Camb) ; (45): 6008-10, 2008 Dec 07.
Artigo em Inglês | MEDLINE | ID: mdl-19030568

RESUMO

Two classes of bulk high-Z polymer composites were prepared, which exhibit scintillation properties for gamma-radiation detection.


Assuntos
Raios gama , Polímeros/química , Contagem de Cintilação , Bismuto/química , Bismuto/efeitos da radiação , Metacrilatos/química , Polímeros/síntese química , Polímeros/efeitos da radiação
7.
J Hazard Mater ; 156(1-3): 80-5, 2008 Aug 15.
Artigo em Inglês | MEDLINE | ID: mdl-18248886

RESUMO

Photocatalytic removal of phenol, rhodamine B, and methyl orange was studied using the photocatalyst ZnO/poly-(fluorene-co-thiophene) (PFT) under visible light. After 2 h irradiation with three 1 W LED (light-emitting diode) lights, about 40% removal of both phenol and methyl orange was achieved; rhodamine B was completely degraded to rhodamine. Diffuse reflectance spectra showed that the absorbance range of PFT/ZnO was expanded from 387 nm (ZnO) to about 500 nm. Photoluminescent spectra and photoluminescent quantum efficiency indicated that electrons were transferred from PFT to the conduction band of ZnO. Electron spin resonance (ESR) signals of spin-trapped paramagnetic species with 5,5-dimethyl-1-pyrroline-N-oxide (DMPO) evidenced that the OH* radicals were indeed formed in the PFT/ZnO system under visible light irradiation. A working mechanism involving excitation of PFT, followed by charge injection into the ZnO conduction band is proposed.


Assuntos
Luz , Polímeros/química , Óxido de Zinco/química , Catálise , Espectroscopia de Ressonância de Spin Eletrônica , Microscopia Eletrônica de Varredura , Fotoquímica
8.
Org Lett ; 9(21): 4371-3, 2007 Oct 11.
Artigo em Inglês | MEDLINE | ID: mdl-17887767

RESUMO

Soluble poly(3,6-fluorene) and its copolymer were synthesized by nickel-catalyzed coupling. Poly(3,6-fluorene) exhibited the optical band gap of 3.6 eV, the emission maximum at 347 nm, and the HOMO level of -6.05 eV. These results confirm that 3,6-linkage is an effective way to get wide band gap conjugated polymers. Furthermore, its copolymer containing triarylamine moieties emits deep-blue light, which means that the adjustable blue light emission can be obtained from their copolymers via energy transfer.

9.
Chem Commun (Camb) ; (39): 4925-6, 2005 Oct 21.
Artigo em Inglês | MEDLINE | ID: mdl-16205801

RESUMO

An ultraviolet-emitting conjugated polymer, poly(9,9'-alkyl-3,6-silafluorene) with a wide band gap of 4.0 eV, has been synthesized and characterized.

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