Stabilization of PbS quantum dots by high molecular polyvinylpyrrolidone

The article describes the results of the investigations of optical and luminescent properties of PbS suspensions and composite coatings stabilized by high‐molecular polyvinylpyrrolidone. Experiments show strong dependence of optical properties and stability of the materials on the concentration ratio between PbS nanoparticles and polymer. Copyright © 2015 John Wiley & Sons, Ltd.     

Immersion film‐forming compositions based on high‐molecular polyvinylpyrrolidone

This work presents the results of experimental study of new immersion‐coating compositions based on high‐molecular polyvinylpyrrolidone and different inorganic additions. The formation of transparent polymer coating on the surface of tested optical element is new approach for visual control of optical materials. The film‐forming immersion compositions can be considered as the new and perspective field of the practical application of polymer materials. Copyright © 2016 John Wiley & Sons, Ltd.     

Synthesis and luminescence properties of Ag2S and PbS clusters in zeolite A

Zeolite A provides a suitable environment to host Ag2S and PbS clusters, so that spectroscopic investigations on very small particles are possible. The Ag2S monomer is colorless and shows photoluminescence at 490 nm with a lifetime of 300 micros, while the absorption and luminescence of Ag4S2 and larger clusters are red-shifted. The properties of these Ag2S/zeolite A materials depend on the co-cations. Results for Li+, Na+, K+, Rb+, Cs+, Mg2+, Ca2+, and Sr2+ are reported. Excitation energy transfer between Ag2S and Ag4S2 has been studied in materials containing Ca2+ co-cations. PbS particles can be prepared by the same method as Ag2S in the cavities of zeolite A. The PbS monomers obtained are yellow and show photoluminescence at 570 nm, with a lifetime of 700 ns.     

Nanosilicon stabilized with ligands: Effect of high-energy electron beam on luminescent properties

Silicon nanopowders with nitrogen heterocyclic carbene (NHC) and butyl as stabilizing ligands were synthesized by bottom up chemical methods. Transmission electron microscopy (TEM) was used to obtain nanoparticle size distribution with 1.8–2.5 mm average diameter. Optical characteristics (photoluminescence and infrared (IR) absorption spectra) of samples were investigated as fabricated and on different steps of irradiation by high-energy 7-MeV electrons. The photoluminescence (PL) spectral changes are slightly different for two cases, but in general, we can see a decrease in luminescence amplitude with fluence growth up to 1.2·10¹⁶ cm⁻², mainly for NHC stabilized nanosilicon. Main mechanisms of radiation-induced changes in nanosilicon sample optical properties are discussed by the joint use of PL and IR spectra analysis.     

Syntheses and properties of dumbbell‐shaped POSS derivatives linked by luminescent π‐conjugated units

Dumbbell‐shaped isobutyl‐substituted 1,2‐bis(4‐vinylphenyl)acetylene‐linked POSS (DA1), 9,10‐bis(4‐vinylphenyl)ethynyl)anthracene‐linked POSS (DA2), and 5,5″‐bis((4‐vinyl)phenyl)ethynyl)‐2,2′:5′2″‐terthiophene‐linked POSS (DA3), and corresponding model compounds were synthesized by cross metathesis and Sonogashira reaction, and their film formability, and thermal and optical properties were examined. The dumbbell structures of the obtained compounds were confirmed by ¹H‐, ¹³C‐, and ²⁹Si‐NMR and MALDI‐TOF‐MS analysis. The dumbbell‐shaped POSS compounds gave optically transparent films. All the model compounds, however, formed opaque films. All the films were emissive under UV irradiation. The dumbbell structures minimize longer wavelength shifts and improve emission efficiency of the luminescent π‐conjugated linker units in their solid states compared with the model compounds. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012.     

Synthesis and optoelectronic properties of luminescent poly(p‐phenylenevinylene) derivatives containing electron‐transporting 1,3,4‐oxadiazole groups

Three random copolymers ( P1–P3 ) comprising phenylenevinylene and electron‐transporting aromatic 1,3,4‐oxadiazole segments (11, 18, 28 mol %, respectively) were prepared by Gilch polymerization to investigate the influence of oxadiazole content on their photophysical, electrochemical, and electroluminescent properties. For comparative study, homopolymer poly[2‐methoxy‐5‐(2′‐ethylhexyloxy)‐1,4‐p‐phenylenevinylene] ( P0 ) was also prepared by the same process. The polymers ( P0–P3 ) are soluble in common organic solvents and thermally stable up to 410 °C under a nitrogen atmosphere. Their optical properties were investigated by absorption and photoluminescence spectroscopy. The optical results reveal that the aromatic 1,3,4‐oxadiazole chromophores in P1–P3 suppress the intermolecular interactions. The HOMO and LUMO levels of these polymers were estimated from their cyclic voltammograms. The HOMO levels of P0–P3 are very similar (?5.02 to ?5.03 eV), whereas their LUMO levels decrease readily with increasing oxadiazole content (?2.7, ?3.08, ?3.11, and ?3.19 eV, respectively). Therefore, the electron affinity of the poly(p‐phenylenevinylene) chain can be gradually enhanced by incorporating 1,3,4‐oxadiazole segments. Among the polymers, P1 (11 mol % 1,3,4‐oxadiazole) shows the best EL performance (maximal luminance: 3490 cd/m², maximal current efficiency: 0.1 cd/A). Further increase in oxadiazole content results in micro‐phase separation that leads to performance deterioration. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 4377–4388, 2007     

Synthesis,characterization and oxygen‐sensing properties of a novel luminescent Cu(I) complex

A novel luminescent copper(I) complex with formula [Cu(PPh₃)₂(PIP)]BF₄ (PPh₃ = triphenyl phosphine, PIP = 2‐phenyl‐1H‐imidazo[4,5‐f][1,10]phenanthroline) has been synthesized and characterized by ¹H NMR, IR, elemental analysis and X‐ray crystal structure analysis. In solid state, it displays broad band emission upon excitation at λ = 420 nm with the emission maximum locates at 551 nm. Its excited‐state lifetime is in the microsecond time scale (3.02 µs); as a result, its emission intensity is sensitive to oxygen concentration and shows oxygen‐sensing properties after being encapsulated into mesoporous silica MCM‐41. For the system with 60 mg/g loading level, a sensitivity (I₀/I) of 4.35, a fluorescence quenching time (t_Q) of 5 s and a recovery time (t_R) of 36 s were achieved. Even after aging for 5 months, the sensitivities of the three loading level systems can be retained, ignoring the measurement error, which indicates that they possess long‐term stability. Copyright © 2009 John Wiley & Sons, Ltd.     

PEGDA‐based luminescent polymers prepared by frontal polymerization

Frontal polymerization (FP) of poly(ethylene glycol) diacrylate (PEGDA) was carried out using benzoyl peroxide (BPO) as radical initiator. In addition, a pyrene containing monomer, 1‐pyrenebutyl acrylate (PyBuAc), was incorporated as a fluorescent probe in order to obtain luminescent materials with different chromophore contents. The resulting polymers were characterized by FT‐IR spectroscopy in the solid state and their thermal properties were determined by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). Moreover, the optical properties of these materials were studied by absorption and fluorescence spectroscopy. The maximum amount of the incorporated pyrene‐containing monomer into the polymer matrix was limited to 1 wt % by the polymerization process. The obtained labeled polymers poly(PEGDA‐co‐PyBuAc) exhibited a broad absorption band at 345 nm. The fluorescence spectra of these polymers exhibited mainly “monomer emission” so that no excimer emission was observed. It is possible to tune the color of the emitted light by varying the pyrene content in the samples. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 2890–2897     

Synthesis and electroluminescence properties of white‐light single polyfluorenes with high‐molecular weight by click reaction

We reported a new way to synthesize single‐chain white light‐emitting polyfluorene (WPF) with an increased molecular weight using azide‐alkyne click reaction. Four basic polymers with specific end‐capping, which exhibited high‐glass transition temperatures (T_g > 100 °C) and excellent thermal stability, were used as foundations of the WPF's synthesis; a blue‐light polymer (PFB2) end‐capped with azide groups can easily react with acetylene end‐capped polymers (PFB1, PFG1, and PFR1, which are emitting blue‐, green‐ and red‐light, respectively) to form triazole‐ring linkages in polar solvents such as N,N‐dimethylforamide/toluene co‐solvent at moderate temperature of 100 °C, even without metal‐catalyst. Several WPFs that consist of these four basic polymers in certain ratios were derived, and the polymer light‐emitting diode device based on the high‐molecular weight WPF was achieved and demonstrated a maximum brightness of 7551 cd/m² (at 12.5 V) and a maximum yield of 5.5 cd/A with Commission Internationale de l'Eclairage coordinates of (0.30, 0.33) using fine‐tuned WPF5 as emitting material. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Fabrication of high‐performance,gradient‐refractive‐index plastic rods with surfmer‐cluster‐stabilized nanoparticles

A novel method was developed with surfmer‐cluster‐stabilized silver nanoparticles to prepare high‐performance, gradient‐refractive‐index (GRIN) plastic rods based on methyl methacrylate. To fabricate the GRIN plastic rods, a novel polymerizable surfactant (surfmer) of 4‐(11‐acryloxyundecyloxy)benzoic acid (AUBA) was synthesized. Silver nanoparticles were prepared with a reverse micelle method in the presence of the novel surfmer. During the fabrication of the silver nanoparticles, the sodium salt of AUBA was formed. GRIN plastic rods were fabricated through centrifugal polymerization and then were heat‐treated at 100 °C under 0.1 Torr for 24 h to remove residual monomers and water. The distribution of the surfmer‐cluster‐stabilized nanoparticles inside the plastic rods was studied with transmission electron microscopy (TEM). The real‐image transmission through the fabricated rods was also confirmed. The results obtained in this investigation suggested that the control of the distribution of surfmer‐cluster‐stabilized nanoparticles could be used to fabricate GRIN rods. Furthermore, the existence of the crosslink‐like surfmers increased the thermal stability of the plastic rods. The GRIN distribution of the rods was established by the dispersion of nanoparticles inside the plastic rods through TEM analysis, refractive‐index analysis, and real‐image transmission. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 5933–5942, 2006     

Tuning luminescent properties of a metal organic framework by insertion of metal complexes

Abstract

We report the preparation and characterisation of new emissive materials based on the insertion of platinum(II) and iridium(III) complexes inside the Al(OH)(bipyridine dicarboxylate) metal organic framework (MOF-253). Guest incorporation is performed by coordination of a metal complex precursor, and provides increased robustness to the system compared to guest inclusion by its physical diffusion. Powder X-ray diffraction analysis highlights the high degree of crystallinity of the materials, with a complete change in the lattice parameters upon metal complex insertion. The photophysical properties of the resulting materials were thoroughly investigated. This synthetic approach is particularly attractive since, as we show, it is possible to tune the emission maxima of our materials over the entire visible range.     

Columnar liquid crystalline assembly of a U‐shaped molecular scaffold stabilized by covalent or noncovalent incorporation of aromatic molecules

We report on our serendipitous finding of the anomalous behavior of a novel liquid crystalline (LC) molecule U _H/H , containing a U‐shaped handle. While U _H/H itself shows a bicontinuous cubic (Cub_bi) phase, U _H/H in the presence of pyrene molecules as an external guest forms a hexagonal columnar (Col_h) phase without phase separation. Interestingly, even when the pyrene molecules were covalently attached to U _H/H ( U _Py/Py ), the molecule exhibited a Col_h phase, with a similar columnar geometry to that of U _H/H mixed with pyrene molecules (1–4 equiv.). This result means that no matter how the pyrene moieties are incorporated in the LC system, the resultant material exhibited a similar molecular assembly with a columnar geometry. This finding is interesting because U _H/H and pyrene molecules do not seem to have specific interactions or shape complementarity to form a columnar assembly, as in the case of U _Py/Py . © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019 , 57, 342–351     

苯并咪唑金属铼(I)配合物的合成及发光性质的研究

以过渡金属铼为中心金属离子,合成了2-(2-吡啶)苯并咪唑(HL1)和2,6-二(苯并咪唑)吡啶(HL2)配合物.该配合物荧光量子产率高、化学性质稳定,在固体状态下,最大发射峰分别是543 nm、577 nm,处在绿光和黄光区.其发光基理是基态金属离子电荷向激发态配体跃迁(MLCT),属于金属离子与配体间的dπ→π~*(L)的跃迁发光.     

Modification of ultra‐high‐molecular weight polyethylene by various fluorinating routes

Chemical–physical properties of ultra‐high‐molecular weight polyethylene (UHMWPE) treated by direct fluorination, direct fluorination accompanied with UV irradiation, by XeF₂ and by TbF₄, were tested by FTIR spectroscopy, visible spectroscopy, 19F and 13C NMR, scanning electron microscopy, XRD, and EPR. Surface energy measurements were carried out. The direct fluorination of UHMWPE is a diffusion‐controlled process, but treatment with XeF₂ is a kinetically controlled one. Direct fluorination and direct fluorination accompanied with UV irradiation results mainly in a formation of ? CF₂? groups. On the contrary, ? CHF? groups are prevailing in UHMWPE treated with XeF₂ and TbF₄. Surface texture of UHMWPE treated with XeF₂ and with F₂ is quite different. Direct fluorination results in a higher polarity of the polymer surface when compared with treatment with XeF₂. For the case of direct fluorination, both long‐lived peroxy and fluoroalkylradicals are formed. For the case of treatment with XeF₂, only fluoroalkylradicals were detected. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 49:3559–3573, 2011     

Evolution of the precipitation kinetics,morphologies, permeation performances,and crystallization behaviors of polyvinylidenefluoride (PVDF) hollow fiber membrane by adding different molecular weight polyvinylpyrrolidone (PVP)

Polyvinylidenefluoride (PVDF) hollow fiber membranes were fabricated by wet spinning (wet/wet) and dry‐jet wet spinning (dry/wet; 3 cm air gap) processes with four types of polyvinylpyrrolidone (PVP) of different molecular weight as additives. Evolution of the precipitation kinetics, morphologies, permeation performances, and crystallization behaviors of the as‐spun PVDF membranes were investigated. The PVDF membranes were well characterized by numerous state‐of‐the‐art analytical techniques: scanning electron microscopy (SEM), X‐ray diffraction (XRD), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and attenuated total reflectance fourier Transform Infrared (FTIR‐ATR) and elucidated accompanying with its precipitation kinetics obtained by light transmittance measurements. The precipitation kinetics results confirm that four PVDF/PVP/NMP dopes experience instantaneous demixing mechanism and the precipitation rate decreases as PVP molecular weight increases. Little peaks are found in the precipitation curves of the PVDF dopes containing PVP of low molecular weight. The SEM images indicate that the middle sponge‐like layer sandwiched by double finger‐like layers becomes thinner for the special precipitation behaviors. Visible large pores exist in the internal surfaces of the PVDF membranes spun by both wet/wet and dry/wet spinning processes. The increase in PVP molecular weight restricts the formation of large pores in the internal surfaces of the PVDF membranes for the increase in dope viscosity. The pure water permeability (PWP) of the as‐spun PVDF membranes increases initially and then decreases as PVP molecular weight increases. The largest PWP flux of 316.7 L m^?2 h^?1 bar^?1 is obtained for the PVDF membrane containing PVP K25 by wet/wet spinning process. The rejections for bovine serum albumin (BSA) by the as‐spun PVDF membranes range from 35.4 to 82.9%. It illustrates that typical PVDF ultrafiltration membranes were obtained in this research. The melting temperature(T_m) of the PVDF hollow fiber membranes decreases with the increase in the PVP molecular weight as a whole. IR spectra and XRD patterns verify the exclusive formation of β crystalline phase structure in the as‐spun PVDF membranes. Copyright © 2010 John Wiley & Sons, Ltd.     

Thermoplastic blend demixing by a high‐pressure,high‐temperature process

The analysis of a thermoplastic polymer blend requires a precise separation of the blend components, which is usually performed by selective solvent extraction. However, when the components are high‐molecular‐weight polymers, a complete separation is very difficult. The use of fluids in near critical and supercritical conditions becomes a promising alternative to reach a much more precise separation. In this work, a method to separate reactive and physical blends from high‐molecular‐weight commercial polymers is proposed. Polyethylene (PE)/polystyrene (PS) blends were separated into their components with n‐propane, n‐pentane, and n‐heptane at near critical and supercritical conditions. The selectivity of each solvent was experimentally studied over a wide range of temperatures for assessing the processing windows for the separation of pure components. The entire PE phase was solubilized by n‐pentane and n‐heptane at similar temperatures, whereas propane at supercritical conditions could not dissolve the fraction of high‐molecular‐weight PE. The influence of the blend morphology and composition on the efficiency of the polymer separation was studied. In reactive blends, the in situ copolymer formed was solubilized with the PE phase by chemical affinity. The method proposed for blend separation is easy, rapid, and selective and seems to be a promising tool for blend separation, particularly for reactive blends, for which the isolation of the copolymer is essential for characterization © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 2361–2369, 2005     

Supramolecular template‐directed synthesis of stable and high‐efficiency photoluminescence 9,10‐diphenylanthryl‐bridged ladder polysiloxane

A soluble well‐defined 9,10‐diphenylanthryl‐bridged ladder polysiloxane ( DPAnLP ) was prepared via supramolecular assembly‐directed condensation polymerization of silanols. The ladder superstructure ( LS ) was obtained via a synergistic interaction of H‐bonding and π–π stacking between polymerizable precursor 2‐tert‐butyl‐9,10‐bis(methyldihydroxylsilyl)anthracene in organic solvent. The resultant LS was then used as template to direct the condensation of silanol groups to obtain DPAnLP with high regularity. It was found that DPAnLP can emit blue light (430 nm) with great stability and high efficiency in both solution and solid film, which indicated a well organizing of fluorophore within confined environment (ladder structure). TGA and DSC measurements showed that DPAnLP had good thermal stability, and cyclic voltammetry detection gave a low‐lying highest occupied molecular orbital level. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 2491–2497, 2010     

Mono‐ and tetranuclear copper(I) complexes with N‐heterocyclic chelating and triphenylphosphine ligands: Crystal structures,luminescent and heterogeneous catalytic properties

N‐heterocyclic chelating and triphenylphosphine ligands react with cuprous halide to form a variety of copper(I) complexes, namely, mononuclear [Cu(PBO)(PPh₃)Br]^.CH₂Cl₂ ( 1 ) and [Cu(PBM)(PPh₃)I] ( 2 ) (PBO = 2‐(2′‐Pyridyl)benzoxazole, PBM = 2‐(2′‐Pyridyl)benzimidazole, PPh₃ = triphenylphosphine) and tetranuclear [Cu₄(μ₂‐I)₂(μ₃‐I)₂(PPh₃)₄]^.2CH₂Cl₂ ( 3 ) have been synthesized and characterized. Complexes 1 and 2 are basically alike; both of them are mononuclear and four‐coordinated, possessing a slightly distorted trigonal pyramidal geometry. Complex 3 is tetranuclear and the coordination numbers of the two copper(I) atoms are three and four, Cu(1) forming an approximate trigonal planar coordination environment, while Cu(2) is a slightly distorted trigonal pyramidal geometry, resulting in a distorted chair‐like conformation. Complexes 1 and 2 are emissive in the solid state at ambient temperature, with the maxima at 552 and 602 nm, respectively, due to a MLCT excited state. Moreover, complex 3 manifests promising heterogeneous catalytic activities for the degradation of methylene blue (MB), with degradation efficiency of 99% under ambient light.     

Simultaneous quantification of catecholamines in rat brain by high‐performance liquid chromatography with on‐line gold nanoparticle‐catalyzed luminol chemiluminescence detection

A new method based on high‐performance liquid chromatography (HPLC) coupled with on‐line gold nanoparticle‐catalyzed luminol chemiluminescence (CL) detection was developed for the simultaneous quantitation of catecholamines in rat brain. In the present CL system, gold nanoparticles were produced by the on‐line reaction of H₂O₂, NaHCO₃?Na₂CO₃ (buffer solution of luminol) and HAuCl_4. Norepinephrine (NE), epinephrine (EP) and dopamine (DA) could strongly enhance the CL signal of the on‐line gold nanoparticle‐catalyzed luminol system. The UV?visible absorption spectra and transmission electron microscopy studies were carried out, and the CL enhancement mechanism was proposed. Catecholamines promoted the on‐line formation of more gold nanoparticles, which better catalyzed the luminol–H₂O₂ CL reaction. The good separation of NE, EP and DA was achieved with isocratic elution using a mixture of methanol and 0.2% aqueous phosphoric acid (5:95, v/v) within 8.5 min. Under the optimized conditions, the detection limits, defined as a signal‐to‐noise ratio of 3, were in the range of 1.32–1.90 ng/mL, corresponding to 26.4?38.0 pg for 20 μL sample injection. The recoveries of catecholamines added to rat brain sample were >94.6%, with the precisions <5.5%. The validated HPLC?CL method was successfully applied to determine NE and DA in rat brain without prior sample purification. Copyright © 2014 John Wiley & Sons, Ltd.     

Weak flocculation of aqueous kaolin suspensions initiating by NaCMC with different molecular weights

The present work is an investigation of the effect of NaCMC with different viscosities (molecular weights) on the stability of aqueous kaolin suspensions at pH 5-6. The stabilizing effect of polymers was characterized by measuring the sedimentation volumes (for 2.5% kaolin suspensions) and some important rheological parameters (for 40% and 50% kaolin suspensions). In certain cases the stability of suspensions was also studied in the presence of 0.5-1.0% NaCl. The additives were incorporated into the suspensions separately and simultaneously, as well. In certain cases the effect of mixing order of NaCMCs was also studied. The lower viscosity NaCMC was found to be a better stabilizing agent than its medium viscosity counterpart at the studied polymer concentrations (0.005-1.0%). This was manifested in smaller sedimentation volumes and lower rheological parameters (viscosity, yield stress, degree of thixotropy and elasticity). The lower and the medium viscosity polymer were simultaneously and consecutively added in a mass ratio of 50:1 and 10:1. The resulted observation of low viscosity and yield stress, and more importantly thixotropy and elasticity, can be interpreted in terms of a “site-blocking” type flocculation.