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Abstract Novel BaGe 4 O 9 :Eu3+ red-emitting phosphors were synthesized by a high-temperature solid-state reaction. The crystal structures, morphological properties, elements analysis, optical properties and fluorescence decay time were investigated systematically. In contrast, the optimal Eu3+-doping concentration is 30 mol% when monitored at 591 nm with a 394 nm excitation. The energy transfer of Eu3+ ions in BaGe 4 O 9 host lattice is dominated by the exchange interaction with the critical distance (R c) of 5.28 Å. As expected, the red-emitting phosphor BaGe 3.7 O 9 :0.3Eu3+ exhibited a better quantum yield (QY) of 57.9% and an excellent lifetime of 2.25 ms. Consequently, the red-emitting phosphors BaGe 3.7 O 9 :0.3Eu3+ revealed a promising performance in warm WLED device with the CIE coordinates of (0.4365, 0.4130), the color temperature (T c) of 3079 K and the color rendering index (R a) of 85.8 under a driven current of 20 mA. These results indicate that the BaGe 4 O 9 :Eu3+ phosphors are prospective candidates as red-light component for warm white light-emitting diodes (WLEDs) devices. Graphical abstract Novel BaGe 4 O 9 :Eu3+ red-emitting phosphors for warm light-emitting diodes were synthesized by a high-temperature solid-state reaction. Image 1 Highlights • Novel BaGe 4 O 9 :Eu3+ red-emitting phosphors were synthesized by a high-temperature solid-state reaction. • The BaGe 4 O 9 :Eu3+ phosphors are prospective candidates as red-light component for warm white light-emitting diodes devices. [ABSTRACT FROM AUTHOR]

Three novel bipolar deep-blue emitters, 1-(4-( tert -butyl)phenyl)-2-(4-(9,9-diphenylacridin-10(9 H )-yl)phenyl)-1 H -phenanthro[9,10- d ]imidazole ( DPACTPI ), 1-(4-( tert -butyl)phenyl)-2-(4′-(9,9-diphenylacridin-10(9 H )-yl)-[1,1′-biphenyl]-4-yl)-1 H -phenanthro[9,10- d ]imidazole ( DPACPhTPI ) and 2-(4-(9,9-diphenylacridin-10(9 H )-yl)phenyl)-1-(4-(trifluoromethyl)phenyl)-1 H -phenanthro[9,10- d ]imidazole ( DPACFPPI ), employing the donor 9,9-diphenyl-9,10-dihydroacridine (DPAC) and the acceptor, phenanthroimidazole, were designed and synthesized. The highly twisted conformations between DAPC and phenanthroimidazole in the molecules efficiently interrupt molecular π-conjugation and inhibit π-π intermolecular interactions, resulting in good thermal stability and efficient deep-blue emission. The three phenanthroimidazole derivatives in non-doped OLEDs exhibited deep-blue emission. In particular, DPACPhTPI -based nondoped device showed an excellent performance with maximum external quantum efficiency (EQE) of 3.50%, maximum current efficiency (CE) of 1.38 cd/A, maximum power efficiency (PE) of 1.40 lm/W and CIE coordinate of (0.156, 0.047), which is among the best results for OLEDs with a similar color. The high radiative exciton utilization could be resulted from hybridized local and charge transfer (HLCT). [ABSTRACT FROM AUTHOR]

The development of efficient and robust, deep-blue, thermally activated delayed fluorescence (TADF) emitters, especially those matching the European Broadcasting Union (EBU) standard with Commission International de L'Eclairage (CIE) coordinates of (0.15, 0.06), is one of the challenging issues in organic light-emitting devices (OLEDs). Through sophisticated molecular engineering, two novel pyrimidine derivatives with D-π-A configuration, 5-(4-(2,6-diphenylpyrimidin-4-yl)phenyl)-5 H -benzofuro[3,2- c ]carbazole ( p BFCz-26DPPM ) and 5-(4-(2,6-diphenylpyrimidin-4-yl)phenyl)-5 H -benzo [4,5]thieno[3,2- c ]carbazole ( p BTCz-26DPPM ) have been designed and synthesized. There are only negligible differences in the molecular configuration and thermal, electrochemical and photophysical properties for the two compounds. However, TADF properties can be tuned by changing the heteroatom in the donor moiety. Compound p BFCz-26DPPM offers a shorter delayed fluorescence lifetime ( τ d ) than that of p BTCz-26DPPM . The optimized device serving p BFCz-26DPPM as dopant presents deep-blue Commission Internationale de l’Eclairage (CIE) coordinates of (0.154, 0.054) and maximum external quantum efficiencies (EQE max ) of 6.20%. Remarkably, no-doped device based on p BFCz--26DPPM delivers CIE coordinates of (0.153, 0.067) and EQEs as high as 5.80%. These device performances are amongst some of those of the best performing deep blue TADF OLEDs with similar color gamut. [ABSTRACT FROM AUTHOR]

The nondoped thermally activated delayed fluorescence (TADF) devices are increasingly attracting attention due to the superior performances and simple fabrication process. By incorporating two acceptors with phenothiazine, two materials 2-(10 H -phenothiazine-10-yl)-10-phenyl-10 H -phenothiazine-5,5-dioxide (PTZ-2PTO) and 3-(10 H -phenothiazin-10-yl)-10-phenylacridin-9(10 H)-one (PTZ-AD) are designed and investigated. Both the two materials possess dual conformations, whereas the quasi-axial conformer is the main configuration of PTZ-2PTO and quasi-equatorial conformer of PTZ-AD is more stable. The quasi-axial conformers show classical fluorescence emission, and the quasi-equatorial conformers exhibit TADF characteristic. Fascinatingly more, efficient energy transfer can be achieved between quasi-axial conformers and quasi-equatorial conformers, exhibiting similar mechanism to the traditional host-guest system. Based on this characteristic, yellow nondoped TADF-OLED device of PTZ-AD has realized the efficiency of up to 17.08%, 50.48 cd A−1 and 60.04 lm W−1. Meanwhile, the PTZ-AD based nondoped device exhibits low turn-on voltage and low efficiency roll-off, which is among the best performance for yellow nondoped TADF devices. In addition, PTZ-AD based doped device realizes high efficiency of 20.23%, 61.04 cd A−1 and 68.45 lm W−1. This dual conformations forming host-guest system provides a new strategy for obtaining highly efficient nondoped OLEDs devices. Image 1 • The PTZ-2PTO and PTZ-AD with dual conformations are designed and synthesized. • Energy transfer is realized between quasi-axial and quasi-equatorial conformers. • The yellow nondoped TADF-OLED device realized the maximum EQE up to 17.08%. [ABSTRACT FROM AUTHOR]

Malachite green (MG) is an industrial dye, but has been once abused in aquaculture for disease treatment. Because MG and its metabolite, leucomalachite green (LMG), present great harm to human health, it is essential to rapidly and accurately detect MG and LMG residues in aquatic products. However, the simultaneous screening of MG and LMG is still a challenge to date. In this work, a dual-template molecularly imprinted polymer (MIP) coated CdTe QDs was developed and applied as a nano-probe to simultaneously detect MG and LMG in fish samples via normal and synchronous fluorescence quenching. The molar ratios of templates (MG and LMG) to monomer (APTES) and cross-linker (TEOS), and the amount of CdTe QDs in the probe preparation were optimized. A normal fluorescence emission at 600 nm could be linearly quenched by MG, while the synchronous fluorescence emission at the wavelength interval of 340 nm could be quenched by both LMG and MG. The detection limits of MG and LMG were 17 nmol L −1 and 28 nmol L −1 (3 σ , n = 9), respectively. Based on the equations of Stern-Volmer, MG and LMG could be simultaneously detected without any conversion treatment. The recoveries of MG and LMG in fish samples ranged from 92% to 107% and from 91% to 108%, respectively. The results demonstrated that the as-prepared dual-template CdTe@MIP could be used as a fluorescent probe to rapidly and simultaneously detect MG and LMG in fish samples. [ABSTRACT FROM AUTHOR]

Density functional theory (DFT) calculations were applied to analyze the effect of various solvents (water, dimethyl sulfoxide (DMSO), acetonitrile, ethanol, pyridine, chloroform and carbon tetrachloride (CCl 4 )) on the intramolecular hydrogen-bond and anti-oxidative properties and of apigenin molecule. The different polarities of the seven solvents adequately cover the range of possible environments and enable informative comparisons from the results of DFT calculations. The solvent effects were introduced by using Tomasi's polarized continuum model (PCM). With the increasing dielectric constant of the environment, the geometry of apigenin monomer is more planar and apigenin molecule is more stable. Medium strength intramolecular hydrogen-bond was found between H5 and O4 in the apigenin molecule. With the increasing dielectric constant of the environment, the strength of the intramolecular hydrogen-bond was enhanced. Besides, the O5–H5⋯O4 intramolecular hydrogen-bond in apigenin molecule is the closed-shell interaction and considered to possess a dominant character of the covalent interactions in different environments. Solvents induce significant changes in enthalpies of charged species of apigenin. Thus, the preferred thermodynamically mechanism of the anti-oxidative progress for apigenin can be altered by the solvents. For the anti-oxidative progress, hydrogen atom transfer (HAT) is the thermodynamically dominant mechanism in vacuum, CCl 4 and chloroform phases, while sequential proton loss electron transfer (SPLET) is more favored in pyridine, ethanol, acetonitrile, DMSO and water phases. [ABSTRACT FROM AUTHOR]

The development of selective and sensitive probes for sensing G-quadruplexes either in vitro or in cellulo has been the focus of investigation for a long time. Of those investigated, 3,6-bis(1-methyl-4-vinylpyridinium) carbazole diiodide (BMVC) is a promising fluorescent probe utilized in many studies investigating G-quadruplex structures. However, its shortcomings, including similar fluorescence responses for G-quadruplex and duplex DNA and green but not red fluorescent emission, might restrict the further application of BMVC. In this study, in order to improve the selectivity and optical properties of BMVC, we engineered a new probe ( TO-CZ ) by incorporating thiazole orange (TO) into the structure of BMVC. We next found that TO-CZ can act as a colorimetric and red-emitting fluorescent dual probe selective for G-quadruplexes without affecting the G-quadruplex topology. Further experiments showed that a 2:1 binding model involving the external binding of TO-CZ to both ends of the G-quadruplex is the most possible binding mode. Furthermore, we applied TO-CZ in sensing G-quadruplexes both in vitro and in cellulo , and found that TO-CZ can selectively and sensitively visualize G-quadruplexes. Notably, TO-CZ might be used to map DNA and RNA G-quadruplexes in cellulo , showing its great potential in investigating intracellular G-quadruplex structures. [ABSTRACT FROM AUTHOR]

A series of novel bipolar host materials, 9-(4-(5 H -pyrrolo [2,3- b :4,5- b ′]dipyridin-5-yl)phenyl)-9′-phenyl-9 H ,9′ H -3,3′-bicarbazole ( NCzpPh2Cz ), 9-(6-(5 H -pyrrolo[2,3- b :4,5- b ′]dipyridin-5-yl)pyridin-3-yl)-9′-phenyl-9 H ,9′ H -3,3′-bicarbazole ( NCzpPy2Cz ) and 9-(6-(5 H -pyrrolo[2,3- b :4,5- b ′]dipyridin-5-yl)pyridin -2-yl)-9′-phenyl-9 H ,9′ H -3,3′-bicarbazole ( NCzmPy2Cz ), employing the donor of 9-phenyl-9 H ,9′ H -3,3′-bicarbazole and the acceptor of 1,5-diazacarbazole, have been designed and synthesized. By adjusting the linkers and linkage topologies, the thermal, photophysical, and electrochemical properties can be fine-tuned. All the three hosts showed excellent thermal stability with high T d (>420 °C) and high T g (>148 °C). Among the three host materials, NCzmPy2Cz using a meta- substituted pyridine as the linker outperformed the other two hosts in blue devices. The device based on NCzmPy2Cz exhibited high efficiencies with a η EQE , max of 20.0 %, η C,max of 42.8 cd/A and η P,max of 39.1 lm/W. More importantly, the efficiency roll-off of NCzmPy2Cz -based device was only 2 % even up to brightness of 1000 cd/m 2 . These results demonstrate that engineering the linker between the donor and acceptor could provide an efficient solution to design bipolar host materials for high efficiency, low roll-off blue PhOLEDs. [ABSTRACT FROM AUTHOR]

Thiazole orange is a commonly used cyanine dye for binding to nucleic acids. Recently, it has been used for the detection of G-quadruplexes. However, thiazole orange is non-selective for G-quadruplex and other nucleic acids, thus hampering its further application. Herein, we designed and synthesized new fluorescent probes by incorporating hydrocarbon rings into the chromophore of thiazole orange. This simple modification dramatically improved selective binding to certain G-quadruplexes. The most promising probe, the cyclopentane fused analogue, exhibited significant fluorescence enhancement when treated with G-quadruplexes but retained weak fluorescence in the presence of double-stranded and single-stranded DNA. The cyclopentane fused probe also displayed considerable selectivity for parallel G-quadruplexes. These modifications reduced the quantum yield of thiazole orange. Further study of the mechanism revealed that the introduction of a hydrocarbon ring altered the planarity of the chromophore as well as the binding affinities for G-quadruplexes, and therefore, influenced the ability to detect G-quadruplexes. [ABSTRACT FROM AUTHOR]

Novel highly emissive 2-pyridone-based compounds 3a,b and 4a–d were synthesized by a convenient one-pot method from 4-(dialkylamino)acetophenones ( 1a , b ) and cyanoketene dithioacetal ( 2a ) or sulfonyl ketene dithioacetals ( 2b , c ), and their fluorescence properties were investigated. A simple structure modification of 2-pyridones significantly affected their optical properties including the emission wavelength and fluorescence intensity. All the 6-(4-dialkylamino)phenyl-2-pyridones showed positive solvatofluorochromism and intense blue-green fluorescence in nonpolar solvents such as chloroform ( Ф : 0.80–0.92) and dichloromethane ( Ф : 0.83–0.94). A hypsochromic shift of the fluorescence emission maxima and strong fluorescence in a polar solvent were observed by substituting the dimethylamino group with a diethylamino group. Introduction of a sulfonyl group disturbed the molecular planarity of compounds 4a , 4b , and 4d , resulting in a strong fluorescence in acetone ( Ф : 0.86–0.95) and acetonitrile ( Ф : 0.59–0.88). These results indicate that 2-pyridone-based compounds have great potential as fluorophores for various practical applications. [ABSTRACT FROM AUTHOR]

Abstract: The sensitive and selective detection of nucleic acids is important for basic research and many applied fields. Herein, a series of new BODIPY-benzofuroquinoline conjugates were designed, synthesized and evaluated as DNA intercalating dyes. All compounds were characterized by using 1H, 13C NMR, IR, UV–Vis and fluorescence spectroscopy, and DNA binding properties of these conjugates to calf thymus DNA were studied by using fluorescence titration, UV titration, isothermal titration calorimetry and CD analysis. Significant enhancement of the fluorescent quantum yield was observed for all the conjugates in the presence of calf thymus DNA, and one compound showed excellent sensitivity and selectivity offering its potential application as a DNA specific fluorescent probe. Our results showed that these conjugates could intercalate into calf thymus DNA with high binding affinities. The properties of these dyes as fluorescent probes for living cells imaging were also investigated. [Copyright &y& Elsevier]

Efficient deep-blue thermally activated delayed fluorescence (TADF) emitters are still very scarce. It is available to render the color bluer by reducing the intensity of intramolecular charge transfer (ICT) between acceptor and donor. Here, attaching the acceptor of six-membered heterocyclic diphenylsulfone-derivative (2PTO) with donors (DMAc and DPAc), two compounds, 2-(9,9-dimethyl-acridin-10(9 H)-yl)-10-phenyl-10 H -phenothiazine 5,5-dioxide (DMAC2PTO) and 2-(9,9-diphenylacridin-10(9 H)-yl)-10-phenyl-10 H -phenothiazine 5,5-dioxide (DPAC2PTO) were designed and synthesized. Due to the largely twisted configuration and weak ICT, DMAC2PTO with small singlet-triplet energy gap (Δ E ST) displayed TADF feature and deep-blue emission. Moreover, DPAC2PTO exhibited much lower photoluminescence quantum yield (PLQY) than DMAC2PTO. The doped device of DMAC2PTO achieved a maximum external quantum efficiency (EQE max) of 15.2% with a deep-blue color coordinate (CIE x,y) of (0.154, 0.108), and showed a narrow emission spectra with a 52 nm full width at half maximum (FWHM). In addition, the non-doped device of DMAC2PTO reached the EQE max of 8.36% with CIE x,y of (0.158, 0.157). Image 1 • Two blue emitters based on diphenylsulfone-derivative acceptor were designed. • The maximum EQE of 15.2% and CIE coordinate of (0.154, 0.108) for doped device were obtained. • The non-doped OLED achieved a maximum EQE of 8.36% and CIE coordinate of (0.158, 0.157). [ABSTRACT FROM AUTHOR]