Quantum Yield In Solution Research Articles

Bipolar transport materials for electroluminescence applications

Benzofuranyl benzene incorporating naphthyl (phenothiazinyl or dimesitylboryl) entities via meta-conjugation have been synthesized. These compounds exhibit bipolar transport characteristic with mobilities in the range of 10−5 to 10−4 cm2/V s at an electric field of 4 × 105 V/cm. The compounds with two naphthyl or dimesitylboryl substituents emit in the violet region with good solution quantum yields. The OLEDs fabricated from the benzofuranyl/dimethylboryl, benzofuranyl/naphthyl and benzofuranyl/dimethylboryl/phenathiazine derivatives have maximum external efficiencies of 1.01%, 1.41% and 3.14%, respectively.

A homoleptic, all-alkynyl-stabilized highly luminescent Au8Ag8cluster with a single crystal X-ray structure

A homoleptic, all-alkynyl-stabilized [Au8Ag8(ArC[triple bond, length as m-dash]C)16] (1, Ar = 3,5-di-tert-butylphenyl) cluster was synthesized and characterized with a single crystal X-ray structure. Reactions of 3,5-di-tert-butyl-phenylacetylene with Ag(i) and Au(i) gave [Ag(ArC[triple bond, length as m-dash]C)]n and Au(PPh3)(ArC[triple bond, length as m-dash]C), respectively, where both have unusually high solubility in nonpolar organic solvents. In addition to drastically increased solubility, the two bulky tert-butyl substituents on the phenyl ring can confine the metal core to a certain size by preventing infinite aggregation of d(10) metals. This feature makes the isolation of an all-alkynyl-stabilized Au-Ag cluster possible. Complex 1 is intensely luminescent with a very high quantum yield of 0.67 in solution at room temperature. Theoretical studies offered valuable insights into the intriguing photophysical properties, and revealed the significant role of metal-alkynyl bond interactions and enhanced molecular rigidity provided by tert-butyl groups.

Preparation, characterization and spectroscopic properties of difluoroboron complexes with some fluoroquinolones

Abstract Six novel difluoroboron complexes with fluoroquinolones were prepared from fluoroquinolones via complexation with boron trifluoride etherate in DMF–CH2Cl2 solution. Their spectroscopic properties were investigated by UV–vis absorption, FTIR, 1H NMR and fluorescence spectroscopic techniques. The results showed that these difluoroboron complexes exhibited the intense fluorescence emission at 401–579 nm under UV visible illumination and possessed a relatively high quantum yield in DMSO solution and solid state. Especially, the difluoroboron complex of Levofloxacin displayed the strongest fluorescence and highest quantum yield (Φu = 0.63) in these difluoroboron complexes, due to its conjugated rigid plane system via four fused six-membered cyclic structures.

Lifetime of fluorescent dye molecules in dense aqueous suspensions of polystyrene nanoparticles.

We study the lifetime of two common fluorescent dye molecules from the Alexa Fluor NHS Ester family dissolved in water in an opaque aqueous dispersion of dielectric polystyrene nanoparticles. We investigate the role of the dispersion composition by varying the particle concentration and adding SDS (sodium dodecyl sulfate) surfactant molecules. The observed strong changes in lifetime of Alexa 430 can be attributed to the relative contribution of radiative and non-radiative decay channels while the lifetime of the Alexa 488 dye depends only weakly on the sample composition. For Alexa 430, a dye with a rather low quantum yield in aqueous solution, the addition of polystyrene nanoparticles leads to a significant enhancement in quantum yield and an associated increase of the fluorescent lifetime by up to 55 %. We speculate that the increased quantum yield can be attributed to the hydrophobic effect on the structure of water in the boundary layer around the polystyrene particles in suspension. Adding SDS acts as a quencher. Over a range of particle concentrations the particle induced increase of the lifetime can be completely compensated by adding SDS.

Synthesis and Properties of Substituted Polyacetylenes Containing Pyrene Moieties in the Side Group

Abstract A novel phenylacetylene derivative containing a pyrene group was synthesized and polymerized with various Rh complex catalysts. The obtained polymers were soluble in common organic solvents such as chloroform and THF. The Mw and Mw/Mn were estimated as ca. 12000–18000 and 1.3–1.7 respectively, and the polymer yields were estimated as around 57–72%. The characteristic absorptions of ≡C–H (3200 cm−1) and C≡C (2100 cm−1) stretchings seen in the monomer spectra have completely disappeared in the polymer spectra from IR spectrum. 1H NMR analysis confirmed that the acetylene triple bonds transformed to polyene double bonds. These polymers were found to be thermally stable based on TGA data. The synthesized polymers exhibited blue fluorescence. The fluorescence quantum yield in solution was high at 0.37–0.41. Furthermore, the obtained polymer had a long fluorescence lifetime.

Synthesis and characterization of solution-processible anthracene- based deep-blue fluorescent dendrimers

Anthracene has been intensively studied as an attractive building block for deep-blue fluorescent emitters due to its wide band gap and high photoluminescence quantum yield (PLQY) in dilute solution. In solid state, however, these anthracene derivatives seem to aggregate or crystallize, leading to the quenched fluorescence, red-shifted emission and poor device lifetime. Therefore, there are few reports about anthracene-based deep-blue emitters suitable for solution-processed undoped devices. To this end, herein we have designed and synthesized a series of solution-processible deep-blue fluorescent dendrimers (Ent1, Ent2 and Ent3) by using 9,10-diphenylanthracene (DPA) as the central core and 1st to 3rd generation oligocarbazole as the peripheral dendron. Unlike DPA that tends to crystallize in the solid state, Ent1~Ent3 are thermally stable, showing very high glass transition temperatures up to 194−371oC without any related signals from the crystallization or melting processes. As determined by atomic force microscopy (AFM), in addition, both the pristine and annealed films of Ent1~Ent3 have a fairly smooth surface with a root-mean-square roughness of 0.33-0.47 nm, indicative of their morphology stability. Meanwhile, the introduction of dendrons can effectively suppress the intermolecular interactions and thus enhance the film PLQY from 46% of Ent1 to 52% of Ent2 and 67% of Ent3. Correspondingly, as a result of the much richer electron-cloud density from the higher generation dendron, the highest occupied molecular orbital (HOMO) energy level is increased from −5.51 eV of Ent1 to −5.37 eV of Ent2 and −5.34 eV of Ent3, which is beneficial for the hole injection. Solution-processed undoped organic light-emitting diodes (OLEDs) are subsequently fabricated with a configuration of ITO\PEDOT:PSS(40 nm)\Ent1~Ent3(40 nm)\TPBI(55 nm)\LiF(1 nm)\Al(100 nm). All the dendrimers display a bright deep-blue emission with Commission International De L’Eclairge (CIE) coordinates of (0.16, 0.11), (0.16, 0.10) and (0.16, 0.09) for Ent1, Ent2 and Ent3, respectively. Noticeably, the turn-on voltage is firstly down from 4.2 V of Ent1 to 3.8 V of Ent2, and then up to 4.8 V of Ent3. This observation means that, albeit the facilitated hole injection, the electron injection would become more difficult in Ent3 owing to its shallow lowest unoccupied molecular orbital (LUMO) level. Therefore, among Ent1~Ent3, more balanced charge injection/transporting and efficient recombination could be expected for the 2nd generation dendrimer Ent2. Consequently, Ent2 obtains the best device performance, revealing a maximum luminous efficiency of 2.63 cd/A, a maximum power efficiency of 2.07 lm/W and a maximum external quantum efficiency of 2.48%. Our results demonstrate a promising approach to the development of solution processible deep-blue fluorescent emitters for undoped OLEDs applications.

A Two-Photon Excitation Based Fluorogenic Probe for Sialome Imaging in Living Systems.

Taking advantage of the fluorescence property of alkyne-modified naphthalimide, the two-photon excited fluorogenic probe Naph-yne is used for azide-tagged mannosyl glycoprotein imaging both at the cellular level and for vertebrate model organisms.

High quantum yield both in solution and solid state based on cyclohexyl modified triphenylamine derivatives for picric acid detection

Five triphenylamine derivatives containing cyclohexyl have been designed and synthesized with a solvent-free green procedure. The compounds possess high quantum yields both in solution and solid state. Our investigation shows that the steric effects of the chair conformation cyclohexyl and strong intramolecular hydrogen bond play a key role for the high emission. Moreover, a conjugated triphenylamine core and strong polar groups (pyridinyl and hydroxy) and their location in the molecule formed a typical non-planar push–pull electronic structure. This special chemical structure endows the molecules with solvatochromic effect and exhibit interesting fluorescent behavior in binary solvent systems of THF-H2O due to the strong intramolecular charge transfer (ICT), which has been confirmed by DFT calculation, absorption and fluorescence spectra of the compounds in different polar solvents. In addition, their high emission characters, both in solution and solid state are utilized for picric acid (PA) detection.

A Water‐soluble Conjugated Polymer for Thiol Detection Based on "Turn‐off" Effect

AbstractWe investigated a novel water‐soluble conjugated polymer (WSCP) for thiol detection based on "turn‐off" effect. This WSCP was modified with poly(ethylene glycol) (PEG) by disulfide linkages to achieve good solubility in aqueous solution (34 mg/mL) and high quantum yield (0.47). The separation of water‐soluble PEG chains from the conjugated backbone induced by the cleavage of the disulfide linkages would lead to a significant decrease of the water solubility and a dramatical fluorescence quenching of the probe. The combined intuitive images and fluorescence spectrophotometer further confirmed that decreased solubility produced an aggregation of the hydrophobic conjugated backbone. The fluorescence intensity of the probe showed a good linear relationship with glutathione (GSH) (1–200 nmol·L−1), and the detection limit was 16 nmol·L−1. This WSCP probe was confirmed to be a good sensing material with high selectivity to thiols by testing various biological molecules. And this WSCP probe exhibited good detection effect to intracellular thiols by testing Hela cells. Considering the good sensitivity and selectivity, the probe could be further used in vivo. In conclusion, this conjugated polymer probe made up for the drawbacks of the micromolecue probes and contributed to the development of new probes based on conjugated polymers.

Synthesis, structure and photophysical properties of regioisomeric sulfone-bridged pyrene–thienoacenes

Abstract Three regioisomeric sulfone-bridged phenyl-pyrene derivatives have been synthesized by post-oxidizing the corresponding sulfide-bridged phenyl-pyrene isomers. The photophysical properties and two crystal structures of these sulfones were investigated and compared with those of their parent compounds. These sulfones display all remarkable solid-state photoluminescence efficiencies as well as good fluorescence quantum yield in solutions.

Solution and Solid Hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) Ultraviolet (UV) 229 nm Photochemistry.

We measured the 229 nm deep-ultraviolet resonance Raman (DUVRR) spectra of solution and solid-state hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX). We also examined the photochemistry of RDX both in solution and solid states. RDX quickly photodegrades with a solution quantum yield of φ ~ 0.35 as measured by high-performance liquid chromatography (HPLC). New spectral features form over time during the photolysis of RDX, indicating photoproduct formation. The photoproduct(s) show stable DUVRR spectra at later irradiation times that allow standoff detection. In the solution-state photolysis, nitrate is a photoproduct that can be used as a signature for detection of RDX even after photolysis. We used high-performance liquid chromatography-high-resolution mass spectrometry (HPLC-HRMS) and gas chromatography mass spectrometry (GCMS) to determine some of the major solution-state photoproducts. X-ray photoelectron spectroscopy (XPS) was also used to determine photoproducts formed during solid-state RDX photolysis.

Reactive bay functionalized perylene monoimide-polyhedral oligomeric silsesquioxane organic electronic dye

Abstract Aggregation-induced quenching is particularly detrimental in perylene diimides, which are characterized by a near-unity fluorescence quantum yield in solution but are far less emissive in the solid state. Previously, perylene diimide has been improved by linking it to the inorganic cage of polyhedral oligomeric silsesquioxanes. As a further study on perylene diimidepolyhedral oligomeric silsesquioxanes, we report on a double functionalized molecular structure, which can be used for substitution at the bay area and as a side group in other materials. Typical solution absorption and emission features of the perylene diimide fragment have been observed in this new reactive perylene diimide-polyhedral oligomeric silsesquioxane. Moreover, reduced stacking during aggregation and spherical particles exhibiting solid fluorescence have been obtained. Organic semiconducting material with enhanced solid state photophysical properties, like solid fluorescence is a subject of great interest owing to its possible high-tech applications in optoelectronic devices.

Synthesis, Photophysical, and Morphological Properties of Azomethine‐Persylilated α‐Cyclodextrin Main‐Chain Polyrotaxane

The synthesis of 2‐rotaxane (3•TMS‐αCD) through a condensation reaction between 3,5–diamino‐1,2,4‐triazole encapsulated into hexakis(2,3,6‐trimethylsilyl) α‐cyclodextrin cavity (TMS‐αCD) and 1‐pyrenecarboxaldehyde is reported. The oxidative coupling of 3•TMS‐αCD afforded then pyrene‐triazole/TMS‐αCD PAMs polyrotaxane (4•TMS‐αCD) azomethine polyrotaxane. The optical, electrochemical, morphological, surface‐free energies, as well as transport properties of 3•TMS‐αCD and its corresponding 4•TMS‐αCD polyrotaxane have been investigated and compared with those of the reference polymer pyrene‐triazole azomethine. The polyrotaxane is soluble in toluene/dimethylformamide (DMF) 1:1, v/v, mixture and displays useful levels of thermal stability and higher fluorescence quantum yield (ΦPL) in DMF solutions. ΦPL improvement is further reflected in the fluorescence lifetime (τF), significantly longer than that of the starting monomer 3•TMS‐αCD (7.8 vs 0.89 ns). In addition, a smoother surface with the smaller grains uniformly distributed on the surface, as well as lower surface‐free energy, combined with energy gap (3.32 vs 3.76 eV) represent noticeable advantages of azomethine backbones encapsulation by TMS‐αCD. image

Degradation rates of benzotriazoles and benzothiazoles under UV-C irradiation and the advanced oxidation process UV/H2O2

Benzotriazoles (BTs) and benzothiazoles (BTHs) are extensively used chemicals found in a wide range of household and industrial products. They are chemically stable and are therefore ubiquitous in the aquatic environment. The present study focuses on the potential of ultraviolet (UV) irradiation, alone or in combination with hydrogen peroxide (H2O2), to remove BTs and BTHs from contaminated waters. Six compounds, three out of each chemical class, were investigated using a low-pressure mercury lamp (main emission at 254 nm) as the radiation source. Initially, the direct phototransformation kinetics and quantum yield in dilute aqueous solution was studied over the pH range of 4–12. All BTs and BTHs, except for benzothiazole, exhibited pH-dependent direct phototransformation rate constants and quantum yields in accordance to their acid−base speciation (7.1 < pKa < 8.9). The direct phototransformation quantum yields (9.0 × 10−4−3.0 × 10−2 mol einstein−1), as well as the photon fluence-based rate constants (1.2–48 m2 einstein−1) were quite low. This suggests that UV irradiation alone is not an efficient method to remove BTs and BTHs from impacted waters. The second-order rate constants for the reaction of selected BTs and BTHs with the hydroxyl radical were also determined, and found to fall in the range of 5.1–10.8 × 109 M−1 s−1, which is typical for aromatic contaminants. Finally, the removal of BTs and BTHs was measured in wastewater and river water during application of UV irradiation or the advanced oxidation process UV/H2O2. The latter process provided an efficient removal, mostly due to the effect of the hydroxyl radical, that was comparable to other aromatic aquatic contaminants, in terms of energy requirement or treatment costs.

Fluorescence enhancement of covalently linked 1-cyano-1,2-diphenylethene chromophores with naphthalene-1,8-diyl linker units: analysis based on kinetic constants.

The fluorescence enhancement effect of covalently fixed fluorescent chromophores has been investigated by means of kinetic analysis of decay rate constants and theoretical calculations. Derivatives of 1-cyano-1,2-diphenylethene dimer have a distorted cyclic structure when both ends are clipped with two naphthalene-1,8-diyl linker units. In contrast to the reference monomer derivative, which exhibits only slight fluorescence in solution (Φf < 0.01, τf < 0.1 ns), the dimer derivative shows high fluorescence quantum yield (Φf = 0.55) and long lifetime (τf = 20.6 ns) in dilute solution owing to suppression of the nonradiative decay process (knr = 0.022 ns(-1)). A V-shaped derivative with a covalent linker on one side showed moderate quantum yield and lifetime (Φf = 0.12, τf = 4.9 ns). According to the wavelength shifts of the absorption/fluorescence bands and theoretical calculations by time-dependent density functional theory (TD-DFT), we propose an H-aggregate-type excimer interaction.

BODIPY-based oligo(ethylene glycol) dendrons as fluorescence thermometers: when thermoresponsiveness meets intramolecular electron/charge transfer.

The temperature-dependent photophysical properties of a series of 4,4-difluoro-4-bora-3a,4a-diaza-s-indacene (BODIPY) derivatives with different oligo(ethylene glycol) (OEG) dendrons were investigated. Weak fluorescence emission was observed for these BODIPY derivatives in dilute solution with low viscosity. BDP-G0 and BDP-G1-TEG exhibit a high quantum yield in viscous glycerol solutions, contrary to the moderate and little fluorescence enhancement for BDP-G1 and BDP-G2 under the same conditions. The photoinduced electron transfer (PET) may have quenched the fluorescence, as supported by calculation. Interestingly, the thermoresponsive BODIPY derivatives show heat-induced luminescence enhancement with a high signal-to-noise ratio and their emission maxima are dependent on the structures of branched tri(ethylene glycol) moieties. Finally, preliminary studies on the BODIPY derivatives as intracellular fluorescence indicators in living HeLa cells were carried out.

Dinuclear Cu(I) complexes prepared from 2-diphenylphosphino-6-methylpyridine

A series of reactions have been performed by mixing 2-diphenylphosphino-6-methyl-pyridine (dpPyMe) and [Cu(CH3CN)4]BF4 in different molar ratios. Starting from equimolar quantities of dpPyMe and Cu+, a dinuclear Cu(I) complex with two P,N binucleating bridging ligands has been obtained. This compound is stable in the solid state, however ligand exchange reactions leading to a mixture of species have been evidenced in solution. By increasing the amount of dpPyMe, the reaction of dpPyMe and [Cu(CH3CN)4]BF4 afforded the dinuclear Cu(I) complex [Cu2(μ-dpPyMe)3(CH3CN)](BF4)2 in which the three bridging dpPyMe ligands are in a head-to-head arrangement. This compound is remarkably stable in solution. It has been also shown that the axial CH3CN ligand of [Cu2(μ-dpPyMe)3(CH3CN)](BF4)2 can be suitably exchanged with other nitrile ligands [benzonitrile, 4-(dimethylamino)-benzonitrile, 4-nitrobenzonitrile and bromoacetonitrile] but also with triphenylphosphine oxide. The electrochemical and photophysical properties of the resulting complexes have been systematically investigated. The [Cu2(μ-dpPyMe)3(L)](BF4)2 derivatives are weak emitters in solution but remarkable emission quantum yields (6 to 46%) have been found in rigid matrices at room temperature. One complex was utilized as active material for preliminary tests in LEC devices.

Synthesis, crystal structure and photochromism of new diarylethenes with a benzene moiety

Three unsymmetrical diarylethenes with both thiophene and benzene moieties were synthesized. Their crystal structures and photochromic features were investigated systematically to elucidate the substituent effects of the terminal phenyl group on photochromism. Computational studies were performed to provide further insight into their frontier molecular orbitals and spatial distributions of electronic density. Each compound exhibited favorable photochromism in hexane and functioned as notable fluorescent photo-switches with fluorescence quenching efficiency of ∼96% induced by the intensity change of UV/vis light. Among the three diarylethenes, the cyano group on the terminal phenyl group significantly decreased the distance of the two reactive carbon atoms and strengthened the intermolecular hydrogen bond stacking interactions, resulting in improved stability in crystal state. Furthermore, it exhibited a red-shifted absorption maximum, an enhanced molar absorption coefficient, cyclization quantum yield, and fluorescence quantum yield in solution.

A carbazole–oxadiazole diad molecule for single-emitting-component white organic light-emitting devices (WOLEDs)

The synthesis is reported of a new molecule consisting of N-phenylcarbazole linked through a butadiyne bridge to 2,5-diphenyl-1,3,4-oxadiazole. The compound shows blue photoluminescence with positive solvatochromism: e.g., λmax 401 nm in cyclohexane, 461 nm in chloroform solution (quantum yield Φf 0.55) and 428 nm in thin film, with a low intensity band extending to ca. 700 nm in films. OLEDs with a device configuration of [ITO/PEDOT:PSS (50 nm)/molecule:PVK:OXD-7 (80 nm)/Bphen (20 nm)/LiF (0.8 nm)/Al (120 nm)] were fabricated. Pure white-light emission with Commission Internationale De L'Eclairage (CIE) coordinates of (0.313, 0.330) at 13 V and good colour stability with a very small offset of coordinates (0.034, 0.033) under biases of 9–15 V has been achieved.

BODIPY-based photosensitizers with intense visible light harvesting ability and high 1O2 quantum yield in aqueous solution

Introducing electron-withdrawing groups into BODIPY enhanced 1O2 sensitization properties, promoted intense light-harvesting ability and significantly improved the photostability of SOPs in aqueous solution.