High Fluorescence Quantum Efficiency Research Articles

Spectroscopic properties and laser performance of Tm:YAG ceramics

Tm:YAG laser ceramics were fabricated by solid-state reaction and simple vacuum sintering, and their spectroscopic characteristics were investigated in detail. High fluorescence quantum efficiency, long fluorescence lifetime and low up-conversion losses were demonstrated, which indicated that such ceramics could be used as laser gain media. Laser operation at 2μm via 3F4→3H6 transition was realized. The maximum output power of 593mW at 2007nm was acquired with an optical conversion efficiency of 15.6%.

Triphenylamine-based conjugated polymer/I− complex as turn-on optical probe for mercury(II) ion

A kind of triphenylamine-based conjugated polymer with simple structure, poly(9,9-dioctyl)-2,7-fluorene-co-N-4-phenylethenyl-4,4′-triphenylamine (PFT-PE), was successfully synthesized via Suzuki coupling reaction. Chemical structure of PFT-PE was verified by NMR and FT-IR analyses. PFT-PE possesses high fluorescence quantum efficiency in THF solution (~0.90), and its fluorescence was efficiently quenched by the introduction of I−, accompanied by the change of its apparent color from colorless to light yellow. Specificity for the detection of I− of PFT-PE was verified by anti-interference experiments toward other common anionic ions, and the detection limit reaches ~2.9×10−7M (according to 3σ rule). Interestingly, thanks to the high association constant and matching ratio between I− and Hg2+, fluorescence of PFT-PE/I− complex recovered quickly with the presence of Hg2+. Most of background cationic ions brought slight interference to the detection of Hg2+ except for Ag+ and Cu2+, and their interference can be excluded readily by additional UV–vis analysis. Detection limit of ~2.4×10−7M for Hg2+ can be obtained by PFT-PE/I−, suggests that PFT-PE can act as dual-channel, high selective, immediacy and sensitive optical probe for I− and Hg2+.

Fluorescence Enhancement of Europium(III) Perchlorate by 2,2′-Dipyridyl on Bis(benzylsulfinyl)methane Complex

A novel ligand with double sulfinyl groups, bis(benzylsulfinyl)methane L, was synthesized by a new method. Its novel ternary complex, has been synthesized [using L as the first ligand, and dipyridyl L' as the second ligand]. In order to study the effect of the second ligand on the fluorescence properties of rare-earth sulfoxide complex, a novel binary europium complex has been synthesized. Photoluminescent measurement showed that the first ligand L could efficiently transfer the energy to Eu (III) ions in the complex. Furthermore, the detailed luminescence analyses on the rare earth complexes indicated that the ternary Eu (III) complex manifested stronger fluorescence intensities, longer lifetimes, and higher fluorescence quantum efficiencies than the binary Eu (III) materials. The fluorescence emission intensities and fluorescence lifetimes of the ternary complex enhanced more obviously than the binary complex.

Pyrene-functionalized carbazole derivatives as non-doped blue emitters for highly efficient blue organic light-emitting diodes

A series of pyrene-functionalized carbazole derivatives, namely N-dodecyl-3,6-di(pyren-1-yl)carbazole (CP2), N-dodecyl-1,3,6-tri(pyren-1-yl)carbazole (CP3) and N-dodecyl-1,3,6,8-tetra(pyren-1-yl)carbazole (CP4), are synthesized and characterized as simple non-doped solution processed blue emitters for OLEDs. By multiple substitution of pyrene on the carbazole ring, we are able to retain the high blue emissive ability of pyrene in the solid as well as improve the amorphous stability and solubility of the material. These materials show high solution fluorescence quantum efficiencies (up to 94%) and can form morphologically stable amorphous thin films with Tg as high as 170 °C. Solution processed double-layer OLEDs using these materials as non-doped blue emitters exhibit good device performance with luminance efficiencies up to 2.53 cd A−1. Their multi-layer devices exhibit outstanding performances. The CP2-based device shows a low turn-on voltage (down to 2.6 V) with an excellent blue emission color (λem = 436 nm) and CIE coordinates of (0.16, 0.14), while the CP3 and CP4-based blue devices also display low turn-on voltages (down to 2.7 V) with high luminance (up to 24479 cd m−2) and luminance efficiencies (up to 6.92 cd A−1).

Synthesis, characterization, and electroluminescence properties of poly(fluorenevinylene benzobisthiazoles)

AbstractA series of vinylene‐linked copolymers based on electron‐deficient benzobisthiazole and electron‐rich fluorene moieties were synthesized via Horner–Wadsworth–Emmons polymerization. Three different polymers P1, P2, and P3, were prepared bearing octyl, 3,7‐dimethyloctyl, and 2‐(2‐ethoxy)ethoxyethyl side chains, respectively. The polymers all possessed moderate molecular weights, good solubility in aprotic organic solvents, and high fluorescence quantum efficiencies in dilute solutions. P2, which bore branched 3,7‐dimethyloctyl side chains, exhibited better solubility than the other polymers, but also exhibited the lowest thermal decomposition temperature of all polymers. Overall, the impact of the side chains on the polymers optical properties in solution was negligible as all three polymers gave similar absorption and emission spectra in both solution and film. Guest‐host light‐emitting diodes using dilute blends of the polymers in a poly(N‐vinylcarbazole) host gave blue‐green emission with P2 exhibiting the highest luminous efficiency, 0.61 Cd/A at ∼500 nm. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013

Fluorescent Temperature Sensing Using Triarylboron Compounds and Microcapsules for Detection of a Wide Temperature Range on the Micro‐ and Macroscale

AbstractFluorescent temperature sensing has received increasing interest in a wide range of fields, including fluid dynamics, micromechanics, and molecular cell biology. Here, a novel series of triarylboron compounds with significant thermosensitive hue transformation and high fluorescent quantum efficiency in wide temperature range is described. It is then demonstrated that fluorescent core/shell microcapsules based on one of the compounds exhibit outstanding temperature response. The microcapsules, dispersed in different liquid or solid media, can serve as highly robust, reliable, and sensitive fluorescent temperature sensors. The sensors are the first example containing a single organic luminophor with a self‐reference feature that can detect on the micro‐ and macroscale from −30 to 140 °C. This finding may open a new avenue to the development of novel fluorescent temperature sensors.

A study of photoluminescence properties and performance improvement of Cd-doped ZnO quantum dots prepared by the sol–gel method

In the present work, ZnO quantum dots (QDs) have been prepared by the sol–gel method, and the performance of the QDs has been improved. The effect of Cd concentration on the structural and luminescent properties of the QDs, as well as the effect of the mass ratio of trioctylphosphine oxide (TOPO)/octadecylamine (ODA), has been investigated. The ZnO and Cd-doped ZnO QDs have hexagonal wurtzite structures and are 3 to 6 nm in diameter. When the Cd content was increased, the QD particle size was reduced; this effect was confirmed in the corresponding ultraviolet–visible spectra. The fluorescence intensity was simultaneously enhanced significantly. Both the UV and fluorescence spectra were blue-shifted. The luminous intensity was further enhanced when the QDs were modified with TOPO/ODA. Fourier transform infrared and X-ray diffraction techniques proved that the polymer successfully coated the surfaces of the QDs. A TOPO/ODA mass ratio of 1:2 was determined to result in the best optical performance among the different ratios examined. The results showed that the described synthetic method is appropriate for the preparation of doped QDs with high-fluorescence quantum efficiency.

Synthesis, characterization and optical properties of aryl and diaryl substituted phenanthroimidazoles

Abstract This article presents a facile synthesis of novel class of blue-green fluorescent phenanthroimidazoles and report on their optical, electrochemical, and thermal properties. Detailed photophysical and quantum chemical studies with a series of hydroxy-, methoxy-, nitro-, amino- and tosylaminophenyl substituted derivatives of 2-phenyl-1 H -phenanthro[9,10- d ]imidazole and 1,2-diphenyl-1 H -phenanthro[9,10- d ]imidazole have been performed to elucidate the origin of the surprisingly divergent emission shifts. Out of these, three dyes (HPhI, HPPhI, and TsPPhI) undergo excited state intramolecular proton transfer (ESIPT) reaction leading a large Stokes’ shifted fluorescence emission from the phototautomer. The results of quantum chemical investigations not only confirmed the intramolecular charge transfer characteristics of the ESIPT tautomers but also provided a rational for the observed high fluorescence quantum efficiency in the solid state. The high photoluminescence quantum yield ( Φ PL ∼ 39–68%) in the solid state is ascribed to twisted chromophores due to phenyl substituents at 1,2-position of the phenanthroimidazole ring which restricted intramolecular motion, leading to an optically allowed lowest optical transition without self quenching.

Tetraphenylethenyl-modified perylene bisimide: aggregation-induced red emission, electrochemical properties and ordered microstructures

Perylene bisimides (PBIs) are one class of the most explored organic fluorescent materials due to their high fluorescence quantum efficiency, electron transport behaviour, and ready to form well-tailored supramolecular structures. However, they suffer from heavy aggregation-caused quenching (ACQ) effect which has greatly limited their potential applications. We successfully tackle this problem by chemical modification of the PBI core with two tetraphenylethene (TPE) moieties at the bay positions. This modification resulted in a pronounced fluorescence red-shift (over 120 nm) and rendered the derivatives (1,6-/1,7-DTPEPBI) with evident aggregation-induced emission (AIE) behaviour. Both 1,6-DTPEPBI and 1,7-DTPEPBI emit bright red fluorescence in the solid state. The fluorescence quantum efficiency of the aggregates of 1,7-DTPEPBI (ΦF, solid = 29.7%, formed in a hexane/dichloromethane mixture, fh = 90%) is about 424 times higher than that in dichloromethane solution (ΦF, solut = 0.07%). Electrochemical investigation results indicated that 1,7-DTPEPBI sustained the intrinsic n-type semiconductivity of PBI moiety. In addition, morphological inspection demonstrated that 1,7-DTPEPBI molecules easily form well-organized microstructures despite the linkage of the PBI core with bulky TPE moieties.

Facile synthesis and optoelectronic properties of N,N-difluorenevinylaniline-based molecules

A series of RGB molecules (FXs) with a tuneable light-emitting core and difluorenylamino-based peripheries were synthesized through the Heck coupling reaction in good yields. The intramolecular energy transfers and antenna effects were verified in this series of compounds. Strong photoluminescence (PL) from deep blue (∼415 nm) to saturated red (∼645 nm) was observed. The FXs exhibit good solubility and stability, high fluorescence quantum efficiency (up to 93% in THF and 73% in film), short lifetime (1.3–2.6 ns), and high charge injection and transport properties, revealed by both experimental measurements and theoretical calculations. The preliminary organic light-emitting diode devices exhibit only slightly blue-shifted electroluminescence in comparison with PL without stack characters. This full-colour emitting and solution-processable D–π-X–π-D star-burst molecules are highly attractive for organic optoelectronics.

The equilibria and conversions between three excited states: the LE state and two charge transfer states, in twisted pyrene-substituted tridurylboranes

Excited-state conversions were observed from a series of twisted pyrene-substituted tridurylboranes, corresponding to a locally excited (LE) state, a more planar charge transfer (CT) state with a higher fluorescence quantum efficiency, and a more twisted CT state.

A small change in molecular structure, a big difference in the AIEE mechanism

An anthracene carboxamide derivative of the excited-state intramolecular proton-transfer compound of 2-(2'-hydroxyphenyl)benzothiazole has been newly developed to produce the prominent characteristics of aggregation-induced enhanced emission (AIEE) with a high solid-state fluorescence quantum efficiency of 78.1%. Compared with our previously reported phenyl carboxamide derivatives, a small tailoring of the molecular structure was found to result in a big difference in the dominant factor of the AIEE mechanism. In the phenyl carboxamide derivatives, the dominant factor of the AIEE mechanism is the restriction of the twisted intramolecular charge transfer (TICT) of the enol excited state, regardless of their different aggregation modes. In the anthracene carboxamide derivative, N-(3-(benzo[d]thiazol-2-yl)-4-hydroxyphenyl) anthracene-9-carboxamide, the AIEE characteristics are not dependent on the restriction of TICT, but mainly attributed to the cooperative effects of J-aggregation and the restriction of the cis-trans tautomerization in the keto excited state. A specific N···π interaction was found to be the main driving force for this J-aggregation, as revealed by the single crystal analysis. The AIEE mechanism of this anthracene carboxamide derivative was studied in detail through photophysical investigations and theoretical calculations. On the basis of its AIEE characteristics, a stable non-doped organic light-emitting diode was achieved, with high color purity and a remarkably low efficiency roll-off.

Synthesis and fluorescence study of 3-aminoalkylamidonapthalimides

Abstract A new series of fluorescent 3-aminoalkylamidonapthalimides were synthesized starting form 1,8-naphthalic anhydride. The structure of these compounds was characterized by 1 H NMR, 13 C NMR, IR and Mass spectral analysis. The solvent effect on 1 H and 13 C NMR of these compounds was studied in CDCl 3 , CDCl 3 :DMSO-d 6 (7:3, v/v) and DMSO-d 6 . NMR chemical shift of the ortho and para protons and meta carbons of naphthalene ring showed maximum variation on moving from CDCl 3 to DMSO-d 6 . In CDCl 3 solvent naphthalene ring may exist in slightly puckered form while in DMSO-d 6 it attains maximum planar configuration. Fluorescent properties of the title compounds and their precursors were investigated in different solvents like chloroform, ethanol, acetonitrile, acetone, DMSO and water. 3-Aminoalkylamidonapthalimides exhibited improved fluorescence than their precursors. Cyclic amino derivatives yielded higher fluorescence quantum efficiency in protic solvents, ethanol and water. Acylic amino derivatives yielded high fluorescence quantum efficiency in chloroform solvent. The maximum fluorescence quantum yield up to 0.14 was found for butyl amine derivative in chloroform solvent. In general proton accepting nucleophilic solvents like acetone and DMSO quenched the fluorescence.

Blue light-emitting and electron-transporting materials based on dialkyl-functionlized anthracene imidazophenanthrolines

Two novel blue light-emitting materials based on bis( tert-butyl)anthracenyl-imidazophenanthrolines ( BAIPs) have been synthesized and extensively characterized. Both materials exhibited a non-aggregate feature with high fluorescent quantum efficiency and excellent thermal stability. They can serve both as emissive and electron-transporting materials used in electroluminescence (EL) device for blue emission with high luminescence and external quantum efficiency. This study demonstrates that they are potentially useful for a wide range of applications in EL technology.

Synthesis and Characterization of Poly(9,9-dialkylfluorenevinylene benzobisoxazoles): New Solution-Processable Electron-Accepting Conjugated Polymers.

We present the synthesis of four new solution-processable, fluorescent poly(arylenevinylene)s containing benzobisoxazole and fluorene moieties. Two different moieties (cis- and trans-benzobisoxazole) and two different alkyl substituents (octyl and 3,7-dimethyloctyl) were used to study the impact of the structure on the electronic, optical, and thermal properties of these polymers. The polymers were characterized using UV−visible and fluorescence spectroscopy, cyclic voltammetry, thermal gravimetric analysis (TGA), and differential scanning calorimetry (DSC). All of the polymers possess moderate molecular weights, good solubility in aprotic organic solvents, high fluorescence quantum efficiencies in dilute solutions, and high electron affinities. Cyclic voltammetry revealed quasi-reversible reduction for these polymers. Solution-processed light-emitting diodes using dilute blends of the polymer in a poly(N-vinyl carbazole) matrix gave blue emission with luminous efficiencies of up to 1 Cd/A at ∼470 nm which is very promising for deep blue-emitting polymer LEDs.

Synthesis, Photophysical and Electrochemical Characterization of the Heteroleptic Iridium Complexes with Modified Ancillary Ligand by Carrier‐transporting Groups

AbstractTwo heteroleptic iridium complexes with a general formulation of (piq)2Ir(G‐pic) were synthesized and characterized by 1H NMR, 13C NMR and element analysis, in which piq is 1‐phenylisoquinoline, G‐pic is picolinic acid derivative containing carrier‐transporting group by a non‐conjugated connection of 1,6‐dioxyhexane. Both (piq)2Ir(G‐pic) complexes exhibited an enhanced UV absorption band at 310–400 nm, an increased HOMO energy level and an identical red emission peaked at 612 nm with higher fluorescence quantum efficiency (øf), compared to (piq)2Ir(pic) in dichloromethane solution. Interestingly, this iridium complex containing both hole‐transporting triphenylamine and electron‐transporting oxadiazole moieties exhibited the best Фf of 0.58 using Ru(bpy)3(PF6)2 as the reference (øf=0.062 in acetonitrile). This work indicates that incorporating carrier‐transporting groups into ancillary ligand by a non‐conjugated connection is available for improving the optophysical properties of their iridium complexes.

Efficient Two‐Photon Excited Amplified Spontaneous Emission from Organic Single Crystals

E, E-1, 4-bis[4'-(N,N-dibutylamino)styryl]-2,5-dimethoxy-benzene (DBASDMB) organic crystals with high crystalline quality, large size and excellent optical properties are prepared. The linear and nonlinear properties in the crystal are comparatively studied. The relaxation dynamics pumped by two-photon are very similar with that pumped by one-photon. The crystal exhibits very strong two-photon excited fluorescence and amplified spontaneous emission. Efficient two-photon absorption, reasonably high fluorescent quantum efficiency, and high crystal quality together with stimulated emission make organic crystals ideal for the application in frequency upconversion and other optoelectronic fields.

Synthesis and Luminescence Properties of Two Novel Lanthanide (III) Perchlorate Complexes with Bis(benzoylmethyl) Sulfoxide and Benzoic Acid

Two novel ternary rare earth complexes of Tb(III) and Dy(III) perchlorates with bis(benzoylmethyl) sulfoxide (L) and benzoic acid (L') had been synthesized and characterized by elemental analysis, coordination titration analysis, molar conductivity, IR, TG-DSC, (1)HNMR and UV spectra. The results indicated that the composition of these complexes was REL(5)L'(ClO(4))(2) x nH(2)O (RE = Tb(III), Dy(III); L = C(6)H(5)COCH(2)SOCH(2)COC(6)H(5), L' = C(6)H(5)COO; n = 6,8). The fluorescence spectra illustrated that the ternary rare earth complexes presented stronger fluorescence intensities, longer lifetimes and higher fluorescence quantum efficiencies than the binary rare earth complexes REL(5) x (ClO(4))(3) x 2 H(2)O. After the introduction of the second ligand benzoic acid group, the relative fluorescence emission intensities and fluorescence lifetimes of the ternary complexes REL(5)L'(ClO(4))(2) x nH(2)O (RE = Tb(III), Dy(III)) enhanced more obviously than the binary complexes. This indicated that the presence of both organic ligands bis(benzoylmethyl) sulfoxide and the second ligand benzoic acid could sensitize fluorescence intensities of rare earth ions, and the introduction of benzoic acid group was resulted in the enhancement of the fluorescence properties of the ternary rare earth complexes. The phosphorescence spectra were also discussed.

6,7-Difluoro-1,4-dihydro-1-methyl-4-oxo-3-quinolinecarboxylic Acid, a Newly Designed Fluorescence Enhancement-Type Derivatizing Reagent for Amino Compounds

A novel fluorescence enhancement-type derivatizing reagent for amino compounds, 6,7-difluoro-1,4-dihydro-1-methyl-4-oxo-3-quinolinecarboxylic acid (FMQC), was developed. FMQC reacts with aliphatic primary amino compounds to afford strong fluorescent derivatives having high photo-and thermo-stabilities. The FMQC derivatives of amino compounds showed 12-159 times higher fluorescence quantum efficiencies than those of FMQC in aqueous and polar organic media. Additionally, the absorption and fluorescence emission wavelength of the derivatives are red-shifted from those of FMQC. These differences in the fluorescence properties between FMQC and the fluorescent derivative enabled the simple and highly sensitive determination of amino compounds without removing any excess unreacted FMQC by using a simple spectrofluorometer as well as HPLC.

Multifunctional Fluorene‐Based Oligomers with Novel Spiro‐Annulated Triarylamine: Efficient, Stable Deep‐Blue Electroluminescence, Good Hole Injection, and Transporting Materials with Very High Tg

AbstractA series of fluorene‐based oligomers with novel spiro‐annulated triarylamine structures, namely DFSTPA, TFSTPA, and TFSDTC, are synthesized by a Suzuki cross‐coupling reaction. The spiro‐configuration molecular structures lead to very high glass transition temperatures (197–253 °C) and weak intermolecular interactions, and consequently the structures retain good morphological stability and high fluorescence quantum efficiencies(0.69–0.98). This molecular design simultaneously solves the spectral stability problems and hole‐injection and transport issues for fluorene‐based blue‐light‐emitting materials. Simple double‐layer electroluminescence (EL) devices with a configuration of ITO/TFSTPA (device A) or TFSDTC (device B)/ TPBI/LiF/Al, where TFSTPA and TFSDTC serve as hole‐transporting blue‐light‐emitting materials, show a deep‐blue emission with a peak around 432 nm, and CIE coordinates of (0.17, 0.12) for TFSTPA and (0.16, 0.07) for TFSDTC, respectively, which are very close to the National Television System Committee (NTSC) standard for blue (0.15, 0.07). The maximum current efficiency/external quantum efficiencies are 1.63 cd A−1/1.6% for device A and 1.91 cd A−1/2.7% for device B, respectively. In addition, a device with the structure ITO/DFSTPA/Alq3/LiF/Al, where DFSTPA acts as both the hole‐injection and ‐transporting material, is shown to achieve a good performance, with a maximum luminance of 14 047 cd m−2, and a maximum current efficiency of 5.56 cd A−1. These values are significantly higher than those of devices based on commonly usedN,N′‐di(1‐naphthyl)‐N,N′‐diphenyl‐[1,1′‐biphenyl]‐4,4′‐diamine (NPB) as the hole‐transporting layer (11 738 cd m−2 and 3.97 cd A−1) under identical device conditions.