Synthesis and characterization of a novel fluorene‐alt‐carbazole polymer to host green,blue, and red phosphorescence

A novel fluorene‐alt‐carbazole polymer host Poly(9,9‐dioctyl‐9H‐fluorene‐2,7‐diyl‐alt‐N‐tetrahydropyran‐3,6‐carbazole) (PFCz), composed of N‐tetrahydropyran‐3,6‐carbazole and 9,9‐dioctyl‐2,7‐fluorene in the polymer backbone, was synthesized by Suzuki coupling. The PFCz possesses good thermal stability and proper lowest unoccupied molecular orbital (LUMO)/highest occupied molecular orbital (HOMO) energy levels to facilitate the injection and transport of electrons and holes. Upon doping with blue, green, and red phosphors, red ‐ green ‐ blue (R‐G‐B) phosphorescent devices hosted by PFCz have been fabricated and investigated. In contrast to those of blue and green devices, the red devices give better performances with a maximum luminous efficiency of 4.88 cd/A and a maximum power efficiency of 1.85% at 149.84 cd/m², due to favorable triplet energy level (E_T) of PFCz for red phosphor, bis(2‐methyldibenzo[f,h]quinoxaline)(acetylacetonate)iridium(III) [Ir(MDQ)₂(acac)]. Additionally, with different doped concentrations of Ir(MDQ)₂(acac), the PFCz‐related red devices emit nearly pure red light with Commission Internationale de L'Eclairage (CIE) coordinates of (0.57, 0.38), (0.60, 0.38), (0.61, 0.38), and (0.62, 0.38), which were very close to the standard red (0.66, 0.34) by the National Television System Committee. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43234.     

First-principles density-functional investigation on the electronic properties and field emission of a hydrogenated nanodiamond

First-principles calculations using quantum-mechanical density functional theory (DFT) are carried out to investigate the geometrical structure and electronic properties for hydrogen terminated nanometer-sized diamonds. The results reveal that the size dependent feature in the electronic structures for nanodiamonds is different from that of Si clusters. The field emission properties for nanodiamonds are also explored, and it is found that under applied electric field Mulliken charges redistribute and accumulate on the emission side. Furthermore, the emission currents from the occupied orbitals for nanodiamond are calculated and it is revealed that the largest emission current comes from the third highest occupied molecular orbital.     

Attempting to prepare a plastic scintillator from a biobased polymer

A new plastic scintillator was prepared from a renewable polymer source. It is composed of the mighty 2,5-diphenyloxazole and 1, 4-bis(2-methylstyryl)benzene molecules (PPO and bis-MSB), acting as primary and secondary fluorophores, respectively, together dissolved in a polylactic acid matrix—PLA. This polymer is indeed considered as the biomass-based equivalent of petroleum-derived plastics in terms of mechanical and optical properties. Subsequent to the bis-MSB emission, the emission wavelength is centered around 424 nm and the fluorescence decay time is in the nanosecond range. The material was fully characterized, and its scintillation performances were compared to a commercial PVT-based plastic scintillator: EJ-200. Like polystyrene- or polyvinyltoluene-based scintillators, the material displayed a good response linearity with the energy of the incident gamma-ray. However, the observed scintillation yield was rather modest, with a reported 500 ph/MeV value when excited with a gamma-ray-emitting ⁶⁰Co source. This preliminary test could pave the way to new and renewable polymers for unexpected applications such as nuclear physics. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48724.     

Photoluminescence emission of a stable and well‐dispersed unsaturated polyester‐co‐rare‐earth complex

A series of unsaturated polyester (UPR)‐co‐rare‐earth complex (REX) photoluminescence materials with red and green luminescence were fabricated. REXs with double bonds, including complex of europium (Eu³⁺) (methacrylic acid)₃ and 1,10‐phenanthroline (Phen) [Eu(MAA)₃Phen], and complex of terbium (Tb³⁺)(methacrylic acid)₃ and Phen [Tb(MAA)₃Phen], and UPR acted as functional monomers and the polymer matrix, respectively. Fourier transform infrared and UV absorption spectroscopy confirmed the chemical structure of the resulting UPR‐co‐REX according to the free‐radical polymerization mechanism. The study of fluorescence distribution by means of laser scanning confocal microscopy indicated that the REX materials were uniformly dispersed in the UPR matrix. The effects of the type and dosage of REX on the fluorescence intensity and stability were examined via fluorescence spectrometry. We found that the optical/physical properties of the REX were improved by UPR molecular skeleton structures. The fluorescence intensity increased with increasing use of the REX and reached a maximum value when the REX content was 12 wt %. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45253.     

Visible emission from Ce-doped ZnO nanorods grown by hydrothermal method without a post thermal annealing process

Visible light-emitting Ce-doped ZnO nanorods [NRs] without a post thermal annealing process were grown by hydrothermal method on a Si (100) substrate at a low temperature of 90°C. The structural investigations of Ce-doped ZnO NRs showed that the Ce³⁺ ions were successfully incorporated into the ZnO lattice sites without forming unwanted Ce-related compounds or precipitates. The optical investigation by photoluminescence spectra shows that the doped Ce³⁺ ions in the ZnO NRs act as an efficient luminescence center at 540 nm which corresponds to the optical transition of 5d → 4f orbitals in the Ce³⁺ ions. The photoluminescence intensity of the Ce-doped ZnO NRs increased with the increasing content of the Ce-doping agent because the energy transfer of the excited electrons in ZnO to the Ce³⁺ ions would be enhanced by increased Ce³⁺ ions.     

Recent advances on polymer‐stabilized blue phase liquid crystal materials and devices

Polymer‐stabilized blue phase liquid crystals (PS‐BPLC) have become an increasingly important technology trend for information display and photonics applications. BPLCs exhibit several attractive features, such as reasonably wide temperature range, submillisecond gray‐to‐gray response time, no need for alignment layer, optically isotropic voltage‐off state, and large cell gap tolerance. However, some bottlenecks such as high operation voltage, hysteresis, residual birefringence, charging issues due to the large capacitance, and relatively low transmittance remain to be overcome before their widespread applications can be realized. Recent progress on BPLC materials and devices has shown great promise. To realize the electro‐optic effect of PS‐BPLC, two driving modes: in‐plane switching and vertical field switching mode, have been developed. The material system of PS‐BPLC, including nematic LC host, chiral dopant, and polymer network, are discussed. Each component plays an essential role affecting the stability and electro‐optic properties of PS‐BPLC. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40556.     

Theoretical investigation of thermodynamic and optoelectronic properties of Ce4+ doped SrZrO3 ceramics: A DFT study

Theoretical insight into the thermodynamic, structural, electronic and optical properties of SrZr_1-xCe_xO₃ (x = 0, 0.037 and 0.125) ceramics is presented using DFT calculations for predicting their potential applications as photocatalysts. The stable incorporation of Ce⁴⁺ dopant at Zr site of SrZrO₃ is examined in terms of enthalpies of formation and defect formation energies using valid limits of atomic chemical potentials of the species involved in substitutional doping. Our results indicate expansion in the SrZrO₃ lattice and decrease of band gap with increasing cerium doping concentration. Significant differences are observed in the electronic and optical properties of SrZr_1-xCe_xO₃ ceramics due to different nature of unoccupied Ce-4f states above the Femi level when cerium doping concentration increases from x = 0.037 to x = 0.125. Inclusion of the spin-orbit coupling in our DFT calculations are found to cause splitting of the unoccupied Ce-4f states above Fermi level for high concentration of doping. The trends observed in the structural and electronic properties of SrZr_1-xCe_xO₃ ceramics with increasing cerium doping concentration are found to be qualitatively similar for calculations performed without and with the inclusion of spin-orbit coupling. We show that the near UV absorption of SrZrO₃ can be considerably enhanced by increasing cerium doping concentration beyond x = 0.037; making Ce⁴⁺ doped SrZrO₃ potential heterogeneous photocatalysts.     

Additive and free-volume effects on the refractive index of a thiol-ene polymer network

A series of hard, transparent, thermoset polymer samples containing tetravinylsilane (TVS) and 1,3-benzenedithiol (BDT) with varying loadings of zirconium oxide clusters Zr₆(OH)₄O₄(OMc)₁₂ (ZOC) were synthesized. Resulting polymers exhibited a higher refractive index (n) than the parent polymer containing only the monomers TVS and BDT. The refractive index reached a maximum value of 1.711 at a ZOC loading of 3 wt% and then decreased as the ZOC concentration in the polymer matrix increased. The refractive index of ZOC was determined to be 1.540 using the Becke line method. Because the refractive index of ZOC is lower than that of the TVS–BDT polymer matrix, the finding that the incorporation of small quantities of ZOC can increase the refractive index of the TVS–BDT polymer composite was unexpected and is accounted for by the effects of ZOC on the packing efficiency of the composite.     

Experimental investigation on a C.I. engine using orange oil and orange oil with DEE

In the present work, the effect of using neat orange oil, optimum orange oil-diesel blend and the optimum flow rate of DEE with orange oil are evaluated for the performance, emissions and combustion characteristics of a single cylinder, diesel engine. The experimental results show that carbon monoxide (CO), hydrocarbon (HC) and smoke emissions decrease while oxides of nitrogen (NO_x) emissions increase for orange oil and its blends compared to diesel fuel and DEE with orange oil. The brake thermal efficiency in the case of DEE with orange oil is higher than that of orange oil, orange oil-diesel fuel blend and diesel fuel. The peak cylinder pressure and heat release rate for DEE with orange oil are higher than those of diesel fuel operation.     

The absorption and emission properties of highly transparent ZrO2-doped Yb3+: Y2O3 ceramics

Ultra-highly transparent ZrO₂-doped Yb³⁺: Y₂O₃ ceramics were prepared by slip casting and vacuum pressureless sintering and the transmittance reached the highest value of 80.9% for the sample doped with 8.0 at% Yb³⁺. There are three main absorption peaks at 905, 950, and 976 nm, corresponding to the transition from the lowest level of field splitting of ²F_7/2 crystal to every splitting energy levels of ²F_5/2 crystal field. We analyzed the absorption and emission spectra of transparent Yb³⁺: Y₂O₃ from the energy level structure of Yb³⁺, and the transmission, absorption, and emission spectra were systematically studied. There are three main absorption peaks at 905, 950, and 976 nm and four emission peaks at 1076, 1031, 1013, and 977 nm, respectively. The emission peaks at 977 and 1013 nm broaden and vanish for 8.0 and 10.0 at% Yb³⁺-doped Y₂O₃, which may be related to the change of Y₂O₃ crystal field caused by high concentration.     

Fluorene‐based copolymers with donor–acceptor units on the side chain and main chain: Synthesis and application in polymer solar cells

Two narrow band gap fluorene‐based copolymers with donor–acceptor (D–A) structure on the polymer side chain and/or main chain are synthesized by Pd‐catalyzed Stille coupling reactions. The two copolymers have excellent thermal stability. The effects of D–A structure on the main and side chains on the absorption and electrochemical properties are studied. The copolymer PF‐BTh‐DBT with D–A structure both on the main and side chains has broader and stronger absorption and narrower band gap than the copolymer PF‐BTh with only a pendent D–A structure. The power conversion efficiency of the assembled solar cell using PF‐BTh‐DBT as donor and PC₇₁BM as acceptor is 1.6% with open‐circuit voltage (V_oc) 0.84 V under simulated AM 1.5 G solar irradiation (100 mW/cm²). © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 3276–3281, 2013     

Structure,electrical, dielectric,and optical investigation on polyvinyl alcohol/metal chloride nanocomposites

Different concentrations of metal chlorides/polyvinyl alcohol nanocomposites have been prepared by the typical solvent cast technique. The prepared samples were investigated by different techniques such as X‐ray diffraction, differential scanning calorimetry, and scanning electron microscope. DC and AC conductivities are examined at different temperatures and frequencies. An activation process was found in the DC conductivity versus temperature relation and the activation energy was calculated. The AC conductivity obeyed the ω^S power law. The behavior of S with temperature was studied. Various dielectric parameters such as dielectric constant (ε′), dielectric loss (ε″) and loss tangent (tan δ) have been determined in the temperature range 303–443 K at different frequencies. The dielectric parameters were found to decrease with increasing frequency. The study of dielectric relaxation as a function of temperature at constant frequency shows two relaxation mechanisms. The optical band gaps and band tails were estimated from the measured absorption spectra. The applied photon energy found to affect the observed optical band gaps. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Metallopolymers based on a polyazomethine ligand containing rigid oxadiazole and flexible tetramethyldisiloxane units

Soluble, easily processable polymer–metal complexes with improved optical and dielectric properties for optoelectronic functional materials were obtained. For this, a new polyazomethine (PAZ2) was prepared by the reaction of a siloxane dialdehyde and bis(formyl‐p‐phenoxymethyl) tetramethyldisiloxane with 2,5‐bis(p‐aminophenyl)‐1,3,4‐oxadiazole, and it was used as a ligand for Cu(II), Co(II), and Zn(II) ions on the basis of the presence of the electron‐donor nitrogen atoms from the azomethine group and oxadiazole ring. The structure of the PAZ2 was determined by spectral [Fourier transform infrared (FTIR) and ¹H‐NMR spectroscopy] techniques. The metal complexation was proven by FTIR spectroscopy, and the silicon‐to‐metal ratios in the complexes were established by energy‐dispersive X‐ray fluorescence. The new materials were characterized by gel permeation chromatography, thermogravimetric analysis, and differential scanning calorimetry. The optical properties of PAZ2 and the derived metal complexes were studied by ultraviolet–visible and fluorescence spectroscopies. PAZ2 shows fluorescence emission, and it was significantly enhanced by metal complexation. The emission was enhanced by protonation; this behavior is useful, especially for sensors. The electrical properties were investigated by dielectric spectroscopy at various frequencies and temperatures, and this emphasized the existence of dipolar relaxations. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41631.     

Theoretical calculations of the structure and UV-vis absorption spectra of hydrated C60 fullerene

A combined Monte Carlo simulation with semiempirical quantum mechanics calculations has been performed to investigate the structure of hydrated fullerene (C₆₀HyFn) and the influence of hydration on its UV-vis spectra. The statistical information of the C₆₀ fullerene aqueous solution (C₆₀FAS) is obtained from NPT ensemble including one C₆₀ fullerene immerses in 898 water molecules. To obtain an efficient ensemble average, the auto-correlation function of the energy has been calculated. The analyzed center-of-mass pair-wise radial distribution function indicates that, on average, there are 65 and 151 water molecules around the first and second hydration shells, respectively, of a single C₆₀ molecule. To calculate the average UV-vis transition energies of C₆₀HyFn, only the statistically uncorrelated configurations are used in the quantum mechanical calculations (INDO/CIS). These involve hundreds of supramolecular structures containing one C₆₀ fullerene surrounded by the first hydration shell. The calculated average transitions at 268 and 350 nm are in very good agreement with the experimental prediction.     

Effect of chlorination and fluorination of benzothiadiazole on the performance of polymer solar cells

In order to explore the effects of chlorine and fluorine on photophysical properties and the differences, in this work, we synthesized five new polymers, P1 – P5 , in which benzo[1,2-b:4,5-b]dithiophene as the electron donating and benzothiadiazole as electron withdrawing. Analysis of these five polymers showed that the introduction of Cl and F atoms can deeper the highest occupied molecular orbital of these polymers and enhance the absorption of light by the species, thereby improving V_oc and J_sc. Chlorination has a stronger ability to reduce energy levels and broaden the absorption spectrum compared to fluorination. Among them, P2 showed an efficiency of 4.08% with J_sc of 11.28 mA/cm², V_oc of 0.79 V, and fill factor (FF) of 0.45. Since chlorination is easier than fluorination in terms of synthesis, it is advantageous for practical applications. Therefore, we think that chlorination should not be ignored when designing high efficiency photovoltaic materials, especially when their fluorinated counterparts have proven to have good properties.     

Conjugation of a phenanthrene-imidazole fluorophore with the chondroitin sulfate generated from Escherichia coli K4 polysaccharide

Escherichia coli K4 expressed a fructosylated chondroitin (K4), which had a chondroitin structure after the defructosylation treatment. Polysaccharide K4 as a preferred precursor was modified to produce chondroitin sulfate A (CSA). Here, glycosaminoglycans including K4, defructosylated K4, and CSA were conjugated with fluorophore A, which were optimized under three reaction conditions to give the maximum DS of 2.9, 6.5, and 8.5%, respectively. All of conjugates displayed luminescence response linearly to concentration. And they exhibited good storage stability in luminescence and dispersion within 24 h. The conjugate CSA-A with substituted degree of 6.4% was chosen for the bioimaging study in vitro. CSA-A showed nontoxic to astrocytes with concentrations lower than 100 μg/ml. It was internalized effectively by astrocytes after incubation for 24 h.     

Preparation of mullite ceramics with equiaxial grains from powders synthesized by the sol-gel method

Four different alumina content of mullite ceramics were fabricated by powders synthesized using the sol-gel method. The synthesis process of powders, microstructure evolution, mechanical and optical properties of the mullite ceramics were studied. The XRD results showed that the precursors transformed into aluminosilicate spinel phase at 1000 °C and mullite phase at 1200 °C. Equiaxial grains were easy to form in the alumina-rich mullite ceramics while elongated grains were easy to form in the alumina-poor mullite ceramics. With the increase of alumina content, the grain size of the samples firstly increased and then decreased, the number of elongated grains decreased while equiaxed grains increased. The flexural strength, compression strength, fracture toughness, and Vickers hardness all decreased firstly and then increased. While the infrared transmittance increased firstly and then decreased. The transmittance at 4 μm (thickness of 0.75 mm) of the ceramics containing 66mol% Al₂O₃ reached the highest (72%) when sintered at 1780 °C because of the equiaxial grains.     

An investigation of the synergistic effect between magnetite nanoparticles and polypyrrole in nanostructured layer-by-layer films

In this paper, we report the controlled fabrication of layer-by-layer (LbL) films deposited on gold substrates with three different supramolecular architectures using polypyrrole (Ppy) and magnetite nanoparticles (Fe₃O₄-np), besides conventional poly(allylamine hydrochloride) (PAH) e poly(vinyl sulfonic acid) (PVS) polyelectrolytes, demonstrating the synergistic effect between Ppy and Fe₃O₄-np such as a result of their interaction. Modified gold electrodes were analyzed by contact angle (wettability), surface plasmon resonance (SPR), raman spectroscopy, cyclic voltammetry, and electrochemical impedance spectroscopy. The (Fe₃O₄-np/Ppy)₃ architecture was also evaluated by scanning electron microscopy. The modified gold electrodes present more homogeneous covering, higher electron transfer and a decrease of resistance with the incorporation of the nanostructured materials such as Ppy and Fe₃O₄-np forming (Fe₃O₄-np/Ppy)₃ LbL film. The results carried out in this study suggest that the (Fe₃O₄-np/Ppy)₃ LbL film can be applied as a possible electrochemical or optical non-enzymatic sensor for analytical detection.     

Linear low‐density polyethylene colored with a nanoclay‐based pigment: Morphology and mechanical,thermal, and colorimetric properties

In this study, a novel kind of hybrid pigment based on nanoclays and dyes was synthesized and characterized. These nanoclay‐based pigments (NCPs) were prepared at the laboratory with sodium montmorillonite nanoclay (NC) and methylene blue (MB). The cation‐exchange capacity of NC exchanged with MB was varied to obtain a wide color gamut. The synthesized nanopigments were thoroughly characterized. The NCPs were melt‐mixed with linear low‐density polyethylene (PE) with an internal mixer. Furthermore, samples with conventional colorants were prepared in the same way. Then, the properties (mechanical, thermal, and colorimetric) of the mixtures were assessed. The PE–NCP samples developed better color properties than those containing conventional colorants and used as references, and their other properties were maintained or improved, even at lower contents of dye compared to that with the conventional colorants. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Photodegradation of methylene blue with a titanium dioxide/polyacrylamide photocatalyst under sunlight

Hydrogels containing TiO₂ nanoparticles (NPs) have photocatalytic properties and degrade pollutants under light. In this study, a polyacrylamide (PAAm) hydrogel was synthesized with TiO₂ P25 NPs as the initiator, acrylamide as a monomer, and N,N′‐methylene bisacrylamide as a crosslinker in aqueous media under sunlight. Fourier transform infrared spectroscopy, thermogravimetric analysis, scanning electron microscopy, and transmission electron microscopy were applied to characterize the TiO₂/PAAm hydrogel. The effects of different synthetic conditions, such as the initiator concentration, crosslinker, and dilution, on swelling were investigated. The maximum swelling of the TiO₂/PAAm hydrogel was 45 g/g in the hydrogel synthesized with optimum conditions by 0.2% TiO₂. The photocatalytic degradability of the hydrogel was investigated with methylene blue (MB) as the pollutant target. Also, the effects of the pH and MB concentration were studied. Under optimum conditions, 95.00% of the MB was degraded by the TiO₂/PAAm photocatalyst after 5 h of irradiation under sunlight. The comparison of the results with those of the TiO₂ P25 powder showed that the TiO₂ NPs had better activity than the hydrogel, but unlike the hydrogel, the activity of these NPs decreased in each recycling time because of the aggregation of NPs. Finally, the hydrogel was recycled seven times without a considerable reduction in the degradation efficiency. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43386.