Absolute Fluorescence Quantum Efficiency Research Articles

Synthesis of Regioregular and Random Boron-Fused Azomethine Conjugated Polymers for Film Morphology Control.

Regioregular and random conjugated polymers based on a boron-fused azomethine unit were synthesized by Sonogashira-Hagihara cross coupling reaction. Although these polymers exhibited similar optical properties in the solution states, a distinct difference was observed in the aggregation forming ability in the film states; scanning electron microscope (SEM) observation indicated the existence of fiber-like aggregates in the spin-coated film of the regioregular polymer, while regiorandom polymer showed no aggregate in the film state. Accordingly, the UV-vis absorption spectrum of the regioregular polymer showed an increased shoulder peak due to the aggregate formation, whereas the random one showed no change. Furthermore, an absolute fluorescence quantum efficiency of the regioregular polymer was enhanced in response to the aggregate disassembly via thermal annealing treatment. In this study, we demonstrate that controlling regioregularity of the conjugated polymers can induce the different morphological structures and thermal-responsive behaviors. These findings could be beneficial for the design strategy and potential applications of thin-film optoelectronic devices with stimuli-responsive properties.

Dipolar 1,3,6,8-tetrasubstituted pyrene-based emitters containing hole- and electron-transporting moieties: Syntheses, structures, optical properties, electrochemistry and electroluminescence

A series of dipolar 1,3,6,8-tetrasubstituted pyrene-based compounds (PyTPA, PyCaZ and Py3CaZ) with a D-π-A configuration were designed and synthesized. The characteristic of these report compounds is that the pyrene core possesses two electron-transporting benzimidazole moieties at 1,8-positions and two hole-transporting arylamine segments at 3,6-sites. These compounds were structurally characterized and their photoelectric properties were investigated by spectroscopy, electrochemical and theoretical studies. The intermolecular π-π interactions successfully suppressed in these polysubstituted pyrenes, which leads to relatively high absolute fluorescence quantum efficiencies in film state (73.89–85.74 %). These three compounds exhibit high thermal stability with their decomposition temperature up to 520 °C. Two types of solution-processing devices were fabricated using compounds PyTPA and Py3CaZ as representatives to investigate their electron-transporting, hole-transporting and light-emitting properties. The single layer device based on PyTPA exhibits a current efficiency of 8.02 cd/A and a maximum brightness of 24439 cd/m2 at 7.8 V.

Based on rigid xanthone group and hydrogen bonding to construct polyimide films with low coefficient of thermal expansion, high temperature resistance, and fluorescent property

In recent years, an increasing amount of attention has been paid to polyimide (PI) substrate materials with high glass transition temperature (Tg) and low coefficient of thermal expansion (CTE) due to the rapid development of the flexible OLED field. To improve Tg and CTE, rigid conjugated structure and hydrogen bonds are designed. Two diamines containing amide and rigid xanthone groups were synthesized (p-DAXBA and m-DAXBA). Two series of PI films, PIa and PIb, were prepared by polymerization of DAXBA with different dianhydrides, i.e., pyromellitic dianhydride (PMDA), 3,3′,4,4′-biphenyl tetracarboxylic diandhydride (BPDA), 4,4′-(hexafluoroisopropylidene)diphthalic anhydride (6FDA), and 4,4′-oxydiphthalic anhydride (ODPA). PIa films prepared by p-DAXBA have more hydrogen bonding, closer molecular chain packing, and stronger molecular charge transfer (CT) effect, as well as better heat resistance, dimensional stability, and mechanical properties than PIb films prepared by m-DAXBA. However, their absolute fluorescence quantum efficiency and transparency are weaker than those of PIb films. A PIa-1 film prepared by p-DAXBA/PMDA has a Tg of 400 °C, tensile strength of 192 MPa, modulus of 6.14 GPa, and CTE as low as 2.3 ppm·K−1. Both PIa-4 and PIb-4 films prepared by ODPA show fluorescent property with maximum emission wavelengths at 509 and 508 nm, and their absolute fluorescence quantum efficiencies are 1.5% and 2.9%, respectively. The as-prepared PI films exhibit potential application in the flexible OLED field.

Dipolar 1,3,6,8-tetrasubstituted pyrene-based blue emitters containing electro-transporting benzimidazole moieties: Syntheses, structures, optical properties, electrochemistry and electroluminescence

A series of dipolar 1,3,6,8-tetrasubstituted pyrene-based compounds (py1, py2, mpy1 and mpy2) were designed and synthesized with two 4-tert-butylphenyl segments at 1,8-positions and two electron-transporting benzimidazole moieties at 3,6-sites of the pyrene core. These compounds were structurally characterized and their photoelectric properties were investigated by spectroscopy, electrochemical and theoretical studies. Moreover, the structure of compound py1 was determined by single-crystal X-ray diffraction analysis, indicating that the compound has a non-coplanar structure and there is no π-π stacking between the molecules. The benzimidazole moieties attached on the pyrene ring via para- and meta-linking modes and by changing the molecular linkage from para-to meta-mode can effectively tune the emission to pure blue region. The four compounds exhibit high absolute fluorescence quantum yields in dichloromethane (99.89–100%) and in film states (54.56–86.78%). In addition, the meta-linked compounds mpy1 and mpy2 exhibit higher absolute fluorescence quantum efficiencies in solution and film states than the para-linked compounds py1 and py2, which demonstrates that the meta-linked architecture can more effectively twist the molecule and suppress the intermolecular interactions. All these compounds exhibit high thermal stability and can form morphologically stable amorphous thin films with glass transition temperature in the range of 182–215 °C. Two types of non-doped blue OLED devices were fabricated using compounds py2 and mpy2 as representatives to investigate their light-emitting and electron-transporting properties and the devices exhibit promising device performance. The devices using meta-linked compound mpy2 as emitting and electron-transporting layers shows pure blue color purity (0.16, 0.10) with high current and power efficiencies (2.70 cd A−1, 1.97 l m W−1).

Thermally Activated Delayed Fluorescence Organic Dots (TADF Odots) for Time‐Resolved and Confocal Fluorescence Imaging in Living Cells and In Vivo

The fluorophores with long‐lived fluorescent emission are highly desirable for time‐resolved fluorescence imaging (TRFI) in monitoring target fluorescence. By embedding the aggregates of a thermally activated delayed fluorescence (TADF) dye, 2,3,5,6‐tetracarbazole‐4‐cyano‐pyridine (CPy), in distearoyl‐sn‐glycero‐3‐phosphoethanolamine‐poly(ethylene glycol) (DSPE‐PEG2000) matrix, CPy‐based organic dots (CPy‐Odots) with a long fluorescence lifetime of 9.3 μs (in water at ambient condition) and high brightness (with an absolute fluorescence quantum efficiency of 38.3%) are fabricated. CPy‐Odots are employed in time‐resolved and confocal fluorescence imaging in living Hela cells and in vivo. The green emission from the CPy‐Odots is readily differentiated from the cellular autofluorescence background because of their stronger emission intensities and longer lifetimes. Unlike other widely studied DSPE‐PEG2000 encapsulated Odots which are always distributed in cytoplasm, CPy‐Odots are located mainly in plasma membrane. In addition, the application of CPy‐Odots as a bright microangiography agent for TRFI in zebrafish is also demonstrated. Much broader application of CPy‐Odots is also prospected after further surface functionalization. Given its simplicity, high fluorescence intensity, and wide availability of TADF materials, the method can be extended to develop more excellent TADF Odots for accomplishing the challenges in future bioimaging applications.

A series of short axially symmetrically 1,3,6,8-tetrasubstituted pyrene-based green and blue emitters with 4-tert-butylphenyl and arylamine attachments

A series of short axially symmetrically 1,3,6,8-tetrasubstituted pyrene-based derivatives (4a–4c) with two 4-tert-butylphenyl segments at 1,8-positions and two hole-transporting arylamine attachments at 3,6-sites of pyrene core were designed and synthesized based on stepwise synthetic strategy. These compounds were structurally characterized and their photoelectric properties were investigated by spectroscopy, electrochemical and theoretical studies. The results show that the incorporation of different arylamine units into pyrene core can tune the electronic structures of the compounds, and polysubstituted configuration of pyrene can effectively suppress the intermolecular π–π interactions and consequently leads to relatively high absolute fluorescence quantum efficiencies. These compounds exhibit high thermal stability and can form morphologically stable amorphous thin films with glass transition temperature in the range of 156–189 °C. Solution-processed non-doped green and blue organic light-emitting diodes with maximum luminance efficiencies 4.14 cd A−1 and 2.41 cd A−1 were achieved for 4b and 4c, respectively.

Synthesis, spectral and electrochemical properties of novel 1,5-diphenyl-3-spirobifluorenyl pyrazoline derivatives

A series of novel 1,5-diphenyl-3-spirobifluorenyl pyrazoline derivatives have been synthesized and characterized by 1H NMR, X-ray crystallography, UV–vis and fluorescence spectroscopy and mass spectrometry. Their maximum UV–vis absorption wavelengths were between 386 and 395nm, and the fluorescence emission wavelengths were between 459 and 469nm, which belongs to the typical blue light emission. All compounds exhibited excellent absolute fluorescence quantum efficiency (AFQE) (>90%) in solution. Moreover, at solid phase, compound 4f also displayed good AFQE (54%). The energy gaps of these derivatives were between 2.8 and 3.0eV, typical for the blue light emission. Molecular orbital calculations revealed that the HOMO and LUMO energy levels were close to 1,3-diphenyl-5-(9-phenanthryl)-4,5-dihydro-1H-pyrazole (DPPhP). The high fluorescence quantum efficiency, appropriate energy gaps and HOMO and LUMO energy levels prove that 1,5-diphenyl- 3-spirobifluorenyl pyrazoline derivatives have the potential to be used as blue light emitting materials.

Quantum efficiency of silica-coated rare-earth doped yttrium silicate

The photoluminescent properties of rare earth-activated white-emitting Y2SiO5:Ce,Tb nanocrystalline phosphor prepared by two different methods, pressure-assisted combustion synthesis and sol–gel, were studied. The synthesized phosphor samples were post-annealed at 1373K and 1623K in order to obtain the X1-Y2SiO5 and X2-Y2SiO5 phases, respectively, which were confirmed by X-ray diffraction measurements. Photoluminescence analysis showed the contribution of two blue-emission bands within the 380–450nm region originating from 5d–4f transitions in Ce3+ ions and a well-defined green emission of Tb3+ ions located at 545nm corresponding to 5D4→7F5 electronic transitions. Thereafter, Y2SiO5:Ce,Tb powders were coated with colloidal silica in order to investigate the effect of silica coatings on their luminescent properties. Absolute fluorescence quantum efficiency measurements were carefully performed, which revealed an increase of 12% of efficiency in coated compared with bare-Y2SiO5:Ce,Tb phosphor.

Fiber-Optic Detection of Explosives Using Readily Available Fluorescent Polymers

A series of simple fluorescent polymers were readily synthesized by palladium-catalyzed Suzuki coupling reactions of dibromoterephthalates containing the small methyl and large cholesteryl esters with bisboronic esters derived from alkylated fluorene and N-hexyldiphenylamine. The polymers had an inherent viscosity ranging from 0.25 to 0.74 dL/g and were characterized by spectroscopic methods. The glass transition temperatures for these polymers ranged from 90 to 104 °C, and the decomposition temperatures were in a range of 291−435 °C in nitrogen. All the polymers emit around 450−530 nm with the absolute fluorescence quantum efficiencies up to 61%. The polymers were tested for detection of the vapor of explosive analyte (2,4-dinitrotoluene) as a thin film coated on glass substrate and on optic-fiber tips. Explosive detection using the polymer-coated optic-fiber probe has been demonstrated to be fast and sensitive, with the fluorescence quenching efficiency reaching 48% within 25 s or 61% within the first m...

Thermal quenching of the fluorescence quantum efficiency in colquiriite crystals measured by thermal lens spectrometry

The dual-beam mode-mismatched thermal lens technique was used to study the temperature dependence of the absolute fluorescence quantum efficiency (η) of a thermal-quenching fluorescence (TQF) process in Cr3+-doped colquiriite crystals (LiSAF and LiSGaF), from 300 to 450 K. The research was developed at a low excitation-power level in order to eliminate the energy-transfer upconversion effect. The results showed that TQF is the main loss mechanism involved. The thermal diffusivity, the thermal conductivity, and the specific heat of the samples were also measured in the same temperature range.

Thermal lens measurements of fluorescence quantum efficiency in Nd 3+-doped fluoride glasses

In this work we used a thermal lens (TL) method in the dual beam mod-mismatched configuration, to determine the fluorescence quantum efficiency, η. Three kinds of Nd 3+-doped fluoride glasses were studied: fluorozirconate 53ZrF 4–29BaF 2–4.5LaF 3–3.5AlF 3–10NaF– XNdF 3 (ZBLAN); fluoroaluminate 20YF 3–40AlF 3–20BaF 2–20CaF 2– XNdF 3 (YABC) and fluoroindate 30PbF 2–20GaF 3–15InF 3–15ZnF 2–20CaF 2– XNdF 3 (PGIZCa); with X = 1 or 2 mol%. For all these samples we obtained the quantum efficiency, η, between 0.80–0.94 and 0.67–0.76 for X = 1 and 2 mol%, respectively. The quantitative treatment for the TL effect provided the absolute fluorescence quantum efficiency of a sample. The TL method has been shown to be a convenient technique for quantum efficiency measurements.

Studies on Fluorescence Efficiency and Photodegradation of Rhodamine 6G Doped PMMA Using a Dual Beam Thermal Lens Technique

In this paper we report the use of the dual beam thermal lens technique as a quantitative method to determine absolute fluorescence quantum efficiency and concentration quenching of fluorescence emission from rhodamine 6G doped Poly(methyl methacrylate) (PMMA), prepared with different concentrations of the dye. A comparison of the present data with that reported in the literature indicates that the observed variation of fluorescence quantum yield with respect to the dye concentration follows a similar profile as in the earlier reported observations on rhodamine 6G in solution. The photodegradation of the dye molecules under cw laser excitation is also studied using the present method.

Absolute fluorescence quantum efficiency of titanium-doped sapphire at ambient temperature

The fluorescence quantum efficiency of Ti 3+:Al 2O 3 at room temparature has been determined at specific excitation wavelengths in its blue-green absorption band ( 2T 2⇒ 2E) using a photocalorimetric compensation technique [1]. The technique yields an absolute fluorenscence quantum efficiency of 0.695 ± 0.010.

Absolute fluorescence quantum efficiency of GSGG : Cr 3+ at ambient temperature

The absolute fluorescence quantum efficiencies of three GSGG : Cr 3+ samples have been determined at specific excitation wavelengths for the 4T 1 and 4T 2 absorption bands using a novel photocalorimetric compensation technique [1]. For laser excitation in the 4T 1 and 4T 1 bands, the technique yields the same fluorescence quantum efficiency within experimental error for all three samples, viz. 0.840 ± 0.015. The effect of flourescence reabsorption on the measurements is discussed.

New photocalorimetric compensation technique for determining absolute fluorescence quantum efficiencies of optically active ions in laser materials

A new photocalorimetric compensation technique is described for determining the absolute fluorescence quantum efficiencies and optical heating efficiencies of optically active ions in laser materials. The method requires a continuous laser source but does not require knowledge of either the thermal properties of the sample or the absolute temperature, and absolute calibration of the laser power is not necessary. The technique has been successfully tested by investigation of a ruby sample, where the absolute fluorescence quantum efficiencies of the green and the blue bands were determined to be the same within experimental error, viz. 0.710±0.005.

Determination of absolute fluorescence quantum efficiency of quinine bisulfate in aqueous medium by optoacoustic spectrometry

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTDetermination of absolute fluorescence quantum efficiency of quinine bisulfate in aqueous medium by optoacoustic spectrometryM. J. Adams, J. G. Highfield, and G. F. KirkbrightCite this: Anal. Chem. 1977, 49, 12, 1850–1852Publication Date (Print):October 1, 1977Publication History Published online1 May 2002Published inissue 1 October 1977https://doi.org/10.1021/ac50020a053RIGHTS & PERMISSIONSArticle Views1017Altmetric-Citations146LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (386 KB) Get e-Alerts Get e-Alerts

Opto—acoustic determination of absolute quantum yields in flourescent solutions

An opto—acoustic method for a precise determination of absolute fluorescence quantum efficiencies in solutions is described. Excitation with an intensity modulated beam of an argon ion laser was used.