International Commission On Illumination Research Articles

Synthesis and luminescence characterization of Dy3+/Sm3+ Co-doped Y2MgTiO6 double-perovskite phosphors for warm WLED

Y2MgTiO6:Dy3+/Sm3+ double-perovskite phosphors were synthesized using the high-temperature solid-state reaction method, and their luminescence properties were examined through various techniques, including Rietveld refinement, excitation and emission spectra, Commission Internationale de l'Eclairage (CIE) analysis, and band gap simulation. Ab initio calculations were performed to analyze the band gap and density of states, allowing for the prediction of the effect of Dy3+ and Sm3+ doping on emission intensity. The emission spectra of Y2MgTiO6 (YMTO) doped with Sm3+ and Dy3+ exhibited maximum peaks at 602 nm and 575 nm, respectively, when excited at 325 nm. Both YMTO:Sm3+ and YMTO:Dy3+ demonstrated excellent thermal stability. The CIE coordinates of YMTO doped with 1 mol% Dy3+ were determined to be (0.3771, 0.3804), with a correlated color temperature (CCT) of 4115 K, confirming its suitability for warm white light applications. Introducing 1 mol% and 3 mol% of Sm3+ ions into the Dy3+/Sm3+ co-doped YMTO allowed for adjustable CCT values of 3719 K and 3302 K, respectively, further enhancing their potential for use in warm white light-emitting diodes (WLEDs).

A high-efficiency double perovskite phosphor SrLaNaTeO6:Mn4+: Potential applications in w-LEDs and indoor plant growth lighting

A novel deep-red phosphor with Mn4+-doped double perovskites SrLaNaTeO6 (SLNTO) was synthesized by the conventional high-temperature solid-state method. SLNTO contains both [NaO6] and [TeO6] octahedra. The octahedral structure of double perovskites facilitates the doping of Mn4+. The band gap (Eg) of the direct semiconductor SLNTO is 2.88 eV. With an excitation wavelength of 322 nm, SLNTO:Mn4+ has a 700 nm deep-red wavelength emission assigned to the energy level transition from 2E1g to 4A2g of Mn4+ ions. Photoluminescence (PL) of the sample and phytochrome far-red light (PFR) absorption are satisfactory matches. According to the Tanabe-Sugano diagram, Mn4+ is located in the strong crystalline field for 2E1g. A 2.0 mol% concentration of Mn4+ is optimal; further high doping results in concentration quenching, ascribed to the neighbour ion interaction and dipole‒dipole (d-d) interactions. The internal quantum efficiency (IQE) is 87.84 %. Additionally, the electroluminescent (EL) spectrum of the encapsulated plant growth lamp overlaps with the chlorophyll a and b absorption spectra. Its Commission Internationale de l'Eclairage (CIE) coordinates of SLNTO:2.0 mol%Mn4+ phosphor with a near-ultraviolet (n-UV) chip are located in (0.720, 0.280). The phosphor-converted white light-emitting diode (pc-WLED) has a high colour rendering index (Ra = 96) with a suitable correlated colour temperature (CCT = 6240 K). The results are satisfactory for white light-emitting diodes (w-LEDs) and plant growth lamps.

Indolo[3,2-b]indole-based multi-resonance emitters for efficient narrowband pure-green organic light-emitting diodes.

Organic light-emitting diodes (OLEDs) utilizing multi-resonance (MR) emitters show great potential in ultrahigh-definition display benefitting from superior merits of MR emitters such as high color purity and photoluminescence quantum yields. However, the scarcity of narrowband pure-green MR emitters with novel backbones and facile synthesis has limited their further development. Herein, two novel pure-green MR emitters (IDIDBN and tBuIDIDBN) are demonstrated via replacing the carbazole subunits in the bluish-green BCzBN skeleton with new polycyclic aromatic hydrocarbon (PAH) units, 5-phenyl-5,10-dihydroindolo[3,2-b]indole (IDID) and 5-(4-(tert-butyl)phenyl)-5,10-dihydroindolo[3,2-b]indole (tBuIDID), to simultaneously enlarge the π-conjugation and enhance the electron-donating strength. Consequently, a successful red shift from aquamarine to pure-green is realized for IDIDBN and tBuIDIDBN with photoluminescence maxima peaking at 529 and 532 nm, along with Commission Internationale de l'Eclairage (CIE) coordinates of (0.25, 0.71) and (0.28, 0.70). Furthermore, both emitters revealed narrowband emission with small full width at half-maximum (FWHM) below 28 nm. Notably, the narrowband pure-green emission was effectively preserved in corresponding devices, which afford elevated maximum external quantum efficiencies of 16.3% and 18.3% for IDIDBN and tBuIDIDBN.

Composition and property correlation of Nd3+ ion doped (Na0·5Bi0.5) TiO3 Lead-free ceramics

Physicochemical, optical, magnetic, and mechanical properties of ceramic compositions of Na0·5[Bi1-xNdx]0.5TiO3 (NBNdxT) (x = 0.0, 0.1, 0.3, and 0.5) were obtained from the solid-state reaction method. X-ray diffraction (XRD) confirmed the primary rhombohedral phase of perovskite belonging to the space group R3c. SEM analysis revealed the multi-grain morphology with induced porosity. The elemental composition of the prepared NBT ceramics was obtained by EDAX. The corresponding FTIR absorption peaks in NBT shifted due to Nd3+ ion doping. The diffuse reflectance spectroscopy (DRS) showed a decrease in the band gap due to the inhomogeneous spread out of the dopant in NBT. The photoluminescence spectroscopy reflected that the Commission International del’Eclairage (CIE) hue coordinates in neodymium-modified NBT appeared in the red region. The hysteresis loop at higher fields is symbolic of the ferromagnetic nature of the material. The ceramics that were examined exhibit low values of wear and friction coefficients.

A Breakthrough in Solution-Processed Ultra-Deep-Blue HLCT OLEDs: A Record External Quantum Efficiency Exceeding 10% Based on Novel V-Shaped Emitters.

It is always a great challenge to achieve high-efficiency solution-processed ultra-deep-blue organic light-emitting diodes (OLEDs) with the Commission Internationale de l'Eclairage (CIE) 1931 chromaticity coordinates matching the blue primary of Rec. International Telecommunication Union-Radiocommunication BT.2100, which specifies high dynamic range television image parameters. Inspired by hybrid local and charge transfer (HLCT) excited state emitters improving exciton utilization through high-lying reverse intersystem crossing, here, a series of high-performance blue emitters by a V-shaped symmetric donor (D)-π-acceptor (A)-π-D design strategy are developed. Here, the large torsions and unstable bonds of D-A structures can be improved through π bridges, and also the conjugation length and donor groups can be easily adjusted. The obtained emitters merit excellent photophysical and electrochemical properties, thermal stability, solution processibility, and HLCT excited state excellence. Results suggest that the OLEDs based on the obtained blue emitters all achieve high maximum external quantum efficiency (EQEmax ) of more than 8% with very low efficiency roll-off. In particular, the device based on 4',5'-bis(4-(9H-carbazol-9-yl)phenyl)spiro[fluorene-9,2'-imidazole] exhibits a satisfactory ultra-deep-blue emission (CIEx , y = 0.1579, 0.0387) and a record-high EQEmax (10.40%) among solution-processed HLCT OLEDs, which is very close to the record EQEmax of devices by vacuum vapor deposition technology.

Tailoring oxygen disparity induced luminescence of Dy3+ incorporated WO3 thin films

Pure and Dy doped WO3 thin films have been prepared by the physical vapor deposition method of electron beam evaporation technique under a pressure of 1 × 10−5 mbar. Films start out amorphous and become crystalline when they are annealed at 350 °C. The diffraction peaks of the X-ray diffractogram are associated with mixed triclinic and monoclinic phases which is determined by performing Rietveld analysis and confirmed by Raman spectroscopy. X-ray photoelectron spectra of the prepared WO3 thin films confirm the presence of six valent tungsten (W+6) and trivalent Dysprosium (Dy+3) in the samples. The even and homogeneous distribution of the particles is visible in SEM pictures of the prepared WO3 thin films. The energy band gap values show a significant decrease on annealing and fall more with Dy doping as a result of the emergence of intermediate states. The annealed films have superior transmittance compared to the non-annealed films which are in amorphous state The prepared thin films' PL emission spectra at 410 nm excitation wavelength exhibit blue, green, and yellowish green emissions as a result of optical band-to-band transitions of oxygen vacancies. Due to the existence of defects like oxygen vacancies, strain, etc., amorphous system, or non-annealed films, have shown better photoluminescence at higher rare earth ion concentration than crystalline system, or annealed films. After annealing the thin films, the overall colour hue of the emitted light can be shown to change from cold white to warm white using the Commission International de l'Eclairage (CIE) diagram. These findings imply that numerous lighting applications can make use of the prepared thin films. According to magnetic experiments, Ferromagnetism (FM) increases with Dy doping due to disparity in oxygen vacancies which is consistent with the results of the Pl experiment. The BMP model was used to discuss these results. The magnetic parameters derived from the fitted data are in good accord with the literature, and the experimental results suit the BMP model well.

Synthesis, structural and optical properties of a novel double perovskite for LED applications

Amidst growing concerns for environmental sustainability and green ecology, the utilization of Light Emitting Diodes (LEDs) for indoor plant cultivation has emerged as an influential area of research. Nonetheless, the growth of indoor plants is often constrained by inadequate lighting. Consequently, designing novel LEDs to create an appropriate light environment has emerged as a focal point in research. As a new type of photocatalytic material with excellent optical properties and light stability, double perovskite has broad application prospects in LEDs manufacturing. In this context, this article aims to synthesize a new Ca2Lu(Nb,Mn)O6 double perovskite and study its optical properties in LEDs lighting for indoor plant growth. A new Ca2Lu(Nb,Mn)O6 double perovskite were synthesized using the traditional high-temperature solid-phase method. The crystal structure and luminescence properties of the double perovskite were characterized in detail using powder X-ray diffraction (XRD), Rietveld refinement, excitation and emission spectra, decay lifetimes, quantum efficiency (QE), electron paramagnetic resonance (EPR) spectra, temperature-dependent emission spectra, and the Commission International de l’Eclairage (CIE) color coordinates. The photoelectric properties of Ca2Lu(Nb,Mn)O6 and Ca2LuNbO6 double perovskite have been explored through first-principles investigations. The absorption spectra from 270 to 600 nm indicates that it can be effectively excited by ultraviolet (UV) light. The emission spectra show a strong broad red emission peak at 684 nm. The luminescence mechanism has been studied using the Tanabe-Sugano diagram. In addition, the internal UV emission ratio β1, crystal field strength Dq, and Racah parameters B and C were evaluated. The thermal stability of the sample was studied through emission spectra at heating temperatures from 303 to 573 K. The results indicate that Ca2Lu(Nb,Mn)O6 double perovskite provides a new solution for indoor plant growth.

High-quality reddish-orange-emitting Sr6Y2Al4O15:Eu3+ phosphors for solid-state lighting and anti-counterfeiting applications

The reddish-orange emitting Sr6Y2Al4O15:Eu3+ phosphors were synthesized via a high-temperature solid-state reaction technique, and their luminescent properties were systematically studied. The dominant emission peak assigned to the electric dipole transition (5D0 → 7F2) was recorded at 612 nm owing to the non-inversion symmetry of the substituted sites of Eu3+ ions under the excitation of charge transfer band (∼261 nm). The emission of Sr6Y2Al4O15:Eu3+ revealed a Commission Internationale de l'Eclairage (CIE) chromaticity coordinate of (0.571, 0.368) and a color purity of 93.6 %. The thermal stability and photoluminescence quantum yield (PLQY) of Sr6Y2Al4O15: Eu3+ were analyzed, exhibiting a high thermal stability of 88.24 % at 423K and a good external PLQY of 36.24 %. Furthermore, the solid-state lighting (SSL) and flexible anti-counterfeiting applications of Sr6Y2Al4O15:Eu3+ were demonstrated. The red light-emitting diode (LED) was packaged with ∼260 nm ultraviolet LED chip, representing a CIE chromaticity coordinate of (0.5955, 0.3592) and a color purity of 86.53 %. The flexible anti-counterfeiting film was fabricated with polydimethylsiloxane polymer, and it showed tunable emission under different excitations. Moreover, the anti-counterfeiting ink was prepared and printed on various substrates. Consequently, the reddish-orange emitting Sr6Y2Al4O15: Eu3+ phosphors with high color purity, good thermal stability, and high quantum efficiency were introduced and potentially used in SSL and flexible anti-counterfeiting applications.

Influence of bleaching gels formulated with nano-sized sodium trimetaphosphate and fluoride on the physicochemical, mechanical, and morphological properties of dental enamel

ObjectivesTo evaluate in vitro the effects of sodium fluoride (F) and nano-sized sodium trimetaphosphate (TMPnano) added to a 35% hydrogen peroxide (H2O2) bleaching gel on the color alteration, enamel mechanical and morphological properties, and H2O2 transamelodentinal diffusion. Materials and MethodsBovine enamel/dentin discs (n = 180) were divided according to the bleaching gel: 35% H2O2 (HP); 35% H2O2 + 0.1% F (HP/F); 35% H2O2 + 1% TMPnano (HP/TMPnano); 35% H2O2 + 0.1% F + 1% TMPnano (HP/F/TMPnano) and 35% H2O2 + 2% calcium gluconate (HP/Ca). The gels were applied 3 times by 40 min; once each 7-day. The Commission Internationale de l'Eclairage (CIE) L*a*b* total color alteration (ΔE), color alteration by CIEDE2000 (ΔE00), whitening index (ΔWID), surface (SH) and cross-sectional hardness (ΔKHN), surface roughness (Ra), and transamelodentinal diffusion were determined. Enamel surfaces were evaluated by Scanning Electron Microscopy (SEM) and X-ray Dispersive Energy (EDX). Data were submitted to ANOVA, followed by the Student-Newman-Keuls test (p <0.05). ResultsΔE, ΔE00, and ΔWID were similar among the gels that promoted a bleaching effect after treatment (p <0.001). Mineral loss (SH and ΔKHN), Ra, and H2O2 diffusion were lower for HP/F/TMPnano; the HP and HP/Ca groups presented the highest values (p <0.001). For SEM/EDX, surface changes were observed in all bleached groups, but less intense with TMPnano. ConclusionsGels containing F/TMPnano do not interfere with the bleaching effect and reduce enamel demineralization, roughness, H2O2 diffusion, and morphological changes. Clinical RelevanceWhitening gels containing F/TMPnano can be used as a new strategy to increase safety and maintain clinical performance.

Improved aggregation-induced emission behavior in D-π-A architectures by modifying the donor units

With the development of aggregation-induced emission (AIE) in optoelectronic devices, stimulus-responsive sensors, optical storage and bioimaging, the design and synthesis of efficient AIE luminogens remains a challenge. Herein, a series of asymmetric pyrene derivatives were prepared by stepwise functionalization at the 1-, 3-positions using traditional reactions. The experimental results show that a promising white-light emitting material (Commission Internationale de L'Eclairage (CIE): x = 0.32, y = 0.31), namely TPxzPy, which has completely separated the highest occupied molecular orbital (HOMOs) and lowest unoccupied molecular orbital (LUMOs) distribution, was produced. Moreover, a new strategy was established to construct pyrene-based AIE luminogens along the short axis. All compounds exhibited higher emission efficiency in the solid or aggregated state versus in solution, especially for TTPaPy with a competitive photoluminescence quantum yield as high as 76.2 %. The present work provides a feasible strategy to construct pyrene-based AIE materials for optoelectronic devices.

Influence of Silver Nanoparticles on Color Stability of Room-Temperature-Vulcanizing Maxillofacial Silicone Subjected to Accelerated Artificial Aging

In this in vitro study, we assessed the color stability of an A-2186 room-temperature-vulcanizing (RTV) silicone elastomer by incorporating silver nanoparticles during accelerated artificial aging. Using five intrinsic silicone pigment types, including no pigment (colorless), red, blue, mocha, and a combination of the three, we created 160 disk-shaped specimens. These were evenly distributed across 20 experimental groups, each containing 8 samples (n = 8). The specimens underwent aging for 250 and 500 h in an artificial aging chamber. A colorimeter was used to measure the values of L*a*b* according to the Commission Internationale de L’Éclairage (CIE) standards. The 50:50% perceptibility threshold (∆E* = 1.1) and acceptability threshold (∆E* = 3.0) were used in the interpretation of the recorded color differences. At the 0.05 level of significance, the one-way analysis of variance (ANOVA) and Tukey post hoc test were used in the statistical analysis. Fourier-transform infrared spectroscopy with attenuated total reflectance (FTIR-ATR) showed that 0.2% AgNPs after 500 h of aging protected the silicone elastomer matrix and all characteristic bonds of the silicone elastomer. In contrast, silicone without AgNPs showed the distortion of all bonds after 500 h. Chromatic alterations (∆E* &gt; 0) were observed in all specimen groups, surpassing the perceptible threshold (1.1 units), except for mocha, with 0.2% AgNPs after 250 h of aging, which remained below the perceptible threshold (∆E* = 0.97). All groups demonstrated ∆E* values below the acceptable threshold, except for the red color, which exhibited a highly significant color change (p = 0.000). This study determined that all specimens, including colorless silicone, underwent color changes (∆E* &gt; 0), with red displaying a notably significant chromatic alteration. Additionally, AgNPs demonstrated substantial protection of the silicone and reduced the color change across all groups and colors, with enhanced efficacy corresponding to higher AgNP concentrations (0.2% AgNPs &gt; 0.15% AgNPs &gt; 0.1% AgNPs).

A double perovskite structure Ca2InTaO6:Sm3+ orange-red phosphor with high thermal stability for high CRI w-LEDs and plant growth lighting

A novel Sm3+-doped Ca2InTaO6 (CITO:Sm3+) phosphor was produced through a high-temperature solid-state reaction. The Rietveld refinement of the CITO:Sm3+ phosphors were carried out, and its successful synthesis was demonstrated. The phosphor is a member of the Pnma space group (No.62) and features a double perovskite structure. The excitation spectrum of CITO:5 mol%Sm3+ revealed a suitable excitation at 407 nm. The emission spectrum exhibited four distinct peaks. The most intense emission peak is at 601 nm, attributed to the 4G5/2-6H7/2 radiative transition of Sm3+ ions. The emission spectra at different doping concentrations indicated the optical doping concentration of 5 mol%. Dipole-dipole interactions are the reason for the concentration quenching. The internal and external quantum efficiency of CITO:5 mol%Sm3+ is 73.52 % and 38.73 %, respectively. In the range of 300–480 K, CITO:5 mol%Sm3+ phosphor demonstrated high thermal stability and had almost no thermal quenching phenomenon. The CITO:5 mol%Sm3+ phosphor has an activation energy (Ea) of 0.289 eV. The electroluminescence spectra of the fabricated orange-red light-emitting diode (LED) can match the absorption spectra of PR, PFR, chlorophyll b, phycocyanin, and allophycocyanin. The white LED (w-LED) prepared with this phosphor has Commission Internationale de l'Eclairage (CIE) chromaticity coordinates of (0.339, 0.331) and a correlated color temperature of 5184 K, as well as an excellent color rendering index (Ra = 94). These indicate the promising usage of CITO:Sm3+ in plant-growth and w-LED illumination.

Design, synthesis, and properties of a novel red asymmetric luminescent material incorporating diphenylfumaronitrile, carbazole and acridine units

Herein, a deep red luminescent material BCZ-DBFN-AD containing asymmetric structure with both aggregation-induced emission (AIE) and hot exciton properties has been designed and synthesized through bilateral substitution molecular design strategy by introducing 9,9-dimethyl-9,10-dihydroacridine and carbazole electron donors with rotor effect on both sides of diphenylfumanitrile. The distorted molecular configuration and the introduction of larger rigid electron donors endow BCZ-DBFN-AD obvious AIE properties and high solid-state photoluminescence quantum yield (PLQY). Additionally, the distorted molecular configuration can also reduce the carrier injection barrier, activate the conversion channel from triplet exciton to singlet exciton, effectively take into account the locally excited (LE) state component and charge transfer (CT) state component in the hybrid excited state, and effectively improve the efficiency of the device. The PLQY of BCZ-DBFN-AD in the amorphous thin film is 31 %, and the maximum emission wavelength of the non-doped OLED prepared based on BCZ-DBFN-AD is 672 nm with Commission Internationale de L'Eclairage (CIE) coordinates of (0.64, 0.34). The Lmax, CEmax, PEmax, EQEmax are 2489 cd m−2, 1.01 cd A−1, 0.82 lm W−1, 1.83 %, respectively, the efficiency roll-off is only 3 %, and the exciton utilization rate is 29 %, which exceeds the upper limit of 25 % of traditional fluorescent materials.

Efficient non-doped sky-blue fluorescent organic light emitting devices based on cyanopyridine-containing anthracene derivatives

Two new cyanopyridine-containing anthracene derivatives with asymmetrical donor-π-acceptor (D-π-A) molecule structure have been successfully synthesized by Suzuki coupling reaction, namely 4-(10-(9-phenyl-9H-carbazol-3-yl)anthracen -9-yl)benzonitrile (3CzAnPyCN) and 4-(10-(4-(9H-carbazol-9-yl)phenyl)anthracen -9-yl)benzonitrile (pCzAnPyCN). The non-doped organic light emitting devices (OLEDs) using 3CzAnPyCN and pCzAnPyCN as emitters simultaneously achieved high efficiency stable sky-blue luminescence, corresponding to the maximum external quantum efficiency (EQE) of 8.07% and 8.13% with the Commission International de L'Eclairage (CIE) coordinates of (0.18, 0.35) and (0.16, 0.24), respectively. In addition, extremely low efficiency roll-offs were also evaluated in this work. The EQE values remained as high as 7.80% and 7.88% at the luminance of 1000 cd/m2, 7.31% and 6.95% at the luminance of 10000 cd/m2 for 3CzAnPyCN and pCzAnPyCN, respectively. It is found, by photophysical experiments and density functional theory analysis, that the excited state property of the luminogens revealed that the “hot excitons” induced reverse intersystem crossing (RISC) played a crucial role in improving efficiency. Such an excellent electroluminescence (EL) performance achieved in these non-doped OLEDs is among the highest values based on sky-blue fluorescent materials, potential for future optical applications.

Rational design of hybridized local and charge-transfer (HLCT) emitters towards blue OLEDs with high luminance and low efficiency roll-off

Organic blue emitters have been get more and more attention by scientists and industries in the field of organic light-emitting diodes (OLEDs). The design of efficient blue emitters, especially deep-blue ones, is still a challenge because of their intrinsic wide band-gaps and unbalanced carrier mobilities. Herein, two donor‒π‒acceptor (D‒π‒A) type molecules with phenanthro[9,10-d]imidazole (PI) as A and pyridinyl as π-bridge were designed and synthesized by fine-turning the D moieties, namely mPTPA and mP3PCZ, respectively. Theoretical calculation and single-crystal analysis showed that there exist intramolecular hydrogen bond (IHB) interactions inducing small torsion angles between pyridinyl and adjacent phenyls. The rigid 9-phenyl-9H-carbazole (PCZ) and IHB interactions makes mP3PCZ exhibiting planar configuration along the long-axis of the molecule, which could increase the orbital overlap and oscillator strength (fos). The solvatochromic effect manifested that both two emitters have hybridized local and charge-transfer (HLCT) characteristics, and the excited state of mP3PCZ exhibited LE-dominated HLCT state which is beneficial for high photoluminescence efficiency. Ultimately, the non-doped devices based on mPTPA and mP3PCZ achieved maximum luminance larger than 12000 cd m−2. Furthermore, the doped device based on mP3PCZ exhibited maximum external quantum efficiency of 5.14% with low efficiency roll-off, and with the corresponding deep-blue Commission international de l’éclairage (CIE) coordinate of (0.166, 0.085).

Constructing Highly Efficient Circularly Polarized Multiple Resonance Thermally Activated Delayed Fluorescence Materials with Intrinsically Helical Chirality.

Advanced circularly polarized multiple resonance thermally activated delayed fluorescence (CP-MR-TADF) materials synergize the advantages of circularly polarized luminescence (CPL), narrowband emission and TADF characteristic, which can be fabricated into highly efficient circularly polarized organic light-emitting diodes (CP-OLEDs) with high color purity, directly facing the urgent market strategic demand of ultra-high-definition and 3D displays. In this contribution, based on edge topology molecular engineering (ETME) strategy, a pair of high-performance CP-MR-TADF enantiomers, (P and M)-BN-Py, has been developed, which merges the intrinsically helical chirality into MR framework. The optimized CP-OLEDs with emitters (P and M)-BN-Py and the newly developed ambipolar transport host PhCbBCz exhibit pure green emission with sharp peaks of 532nm, full-width at half-maximums (FWHMs) of 37nm, and Commission Internationale de L'Eclairage (CIE) coordinates of (0.29, 0.68). Importantly, they achieve remarkable maximum external quantum efficiencies (EQEs) of 30.6% and 29.2%, and clear circularly polarized electroluminescence (CPEL) signals with electroluminescence dissymmetry factors (gEL s) of -4.37 × 10-4 and +4.35 × 10-4 for (P)-BN-Py and (M)-BN-Py, respectively. This article is protected by copyright. All rights reserved.

Rational design of soluble intrinsic black polyimide containing tetraphenylcyclopentadienone-based chromophore

Black polyimide shows growing demand in optoelectronic apparatus instead of yellow transparent polyimide. However, the most used black polyimide filled with carbon black suffers from the deterioration of electrical and mechanical properties. In this work, a soluble intrinsically black polyimide (TPCPPPPI) with exceptional electrical and mechanical performances was designed and prepared by the polycondensation of 4,4'-(hexafluoroisopropylidene) diphthalic anhydride (6FDA) and a new diamine (TPCPPPDA), which bears tetraphenylcyclopentadienone (TPCP) linked with four benzene rings. Introduction of TPCP-based chromophore into PI molecular chain greatly red-shifted the absorption scope, thus achieving absorption of whole visible light. The resulted TPCPPPPI exhibited highly opaque and black color, with a cut-off wavelength (λcut) up to 698 nm and CIE (Commission Internationale de l'Eclairage) color parameter L* low to 1.41. Simulation calculation suggested that the highly black color of TPCPPPPI was primarily ascribed to the electrons transitions from the highest occupied molecular orbital (HOMO) to lowest unoccupied molecular orbital (LUMO) in the chromophore-bearing diamines, in which the charges chiefly migrated from the 2,5-position aryl groups to the middle cyclopentadienone. Meanwhile, TPCPPPPI exhibited exceptional solubility, mechanical and electric performance. The intrinsically black PI accompanying with exceptional performance and organosoluble feature has attractive potential application in optoelectronic field.

Effect of propolis extract addition on some physicochemical, microbiological, and sensory properties of kefir drinks.

Kefir drinks with sugar (5%, w/v), strawberry flavor (0.15%, v/v), and propolis extract (PE) at different ratios (0.150%, 0.225%, and 0.300%, v/v) were produced and stored at 4°C, and their physicochemical, rheological, microbiological, and sensory properties were monitored during storage. The ratio of PE and storage time had an insignificant effect on the dry matter, protein, fat contents, Commission Internationale de l'Eclairage (CIE) L* and a* color values, apparent viscosity, consistency coefficient, flow behavior index, Lactobacillus spp., Lactococcus spp., and yeast counts of kefir drinks (p > .05). The CIE b* values of kefir drinks increased with an increase in PE ratio (p < .05). All kefir samples exhibited a pseudoplastic flow behavior. Initially, the total antioxidant capacity of kefir drinks was 2.19 μmol TE/100 mL, which increased to 2.51 μmol TE/100 mL for kefir drinks with 0.225% PE. The total phenolic content and antioxidant capacity of kefir drinks with PE decreased during storage. PE addition did not influence the sensory color and taste liking scores of kefir drinks adversely until the 8th day of storage. In terms of odor liking scores, kefir drinks with 0.225% and 0.300% PE had a similar score to control drinks. Additionally, kefir drinks with 0.150% and 0.225% PE received an overall liking score similar to control drinks. Results indicated that the incorporation of PE at a ratio of 0.225% was recommended for the production of strawberry-flavored kefir drinks with acceptable sensory characteristics and increased functional properties, and this product could be stored for up to 8 days.

The Optical Translucency, Opalescence, and Reflectance of Different As-Received Ceramic Brackets: A Spectrophotometer Study

Aim: To determine the difference in the reflected color coordinates and to compare the translucency and opacity of different as-received ceramic brackets using a spectrophotometer. Materials and Methods: Four types of ceramic brackets were investigated in this in vitro study. A total of 72 ceramic brackets were examined using a spectrophotometer. Reflected color coordinates of the labial side of bracket were measured according to the Commission Internationale de l’Eclairage (CIE) color scale. Color difference between brackets was calculated using the equation: Δ E*ab = [(Δ L*)2 + (Δ a*)2 + (Δ b*)2] 1/2. Translucency parameter (TP) and opalescence parameter (OP) were calculated to determine translucency and opacity of the brackets, respectively. Data was collected and analyzed using IBM SPSS V25. The significance level was set at p ≤ .05. One-way ANOVA and post hoc multiple comparison tests were utilized. Results: The range for CIE L* (lightness) was 62.69 to 58.83, for a* (red–green parameter) −0.33 to −2.9 and for b* (yellow–blue parameter) −2.19 to 2.29. All these color co-ordinates were influenced by bracket brand ( p &lt; .05). DISCREET™ showed the highest TP = 16.342 and Symetri™ Clear showed the lowest = 10.823. The OP values ranged between 1.783 and 3.781 and Symetri™ Clear showed the highest OP. Conclusion: Color coordinates, TP, and OP of esthetic brackets investigated with a spectrophotometer were significantly different and influenced by the material microstructure and/or manufacturing process.

Cyan luminescence from Bi ions-doped borosilicate glass induced by the gradual substitution of MO (M=Ca, Sr, Ba)

At present, amorphous glasses that can give blue light, green light, and yellow light emission upon ultraviolet excitation have achieved good commercial prospect, but lacking of the high-efficiency cyan luminescence is still a challenging problem. To fill the lack of cyan light emission in the current white light LED technology spectrum excited by ultraviolet light, the effect of the substitution of CaO for SrO and BaO, and that of SrO for BaO on the optical properties, structure, DSC, and CIE (Commission International de L'Eclairage) coordinates of Bi ions-doped borosilicate glasses were systematically studied in this work. The emission spectra results reveal that the emission position of Bi ions-doped borosilicated glasses is observed from 482 nm to 492 nm when CaO is gradually replaced by SrO, from 482 nm to 502 nm when CaO is gradually replaced by BaO. In one word, the luminescent peak position of the Bi ions-doped borosilicate glass can be easily tuned by altering the concentration of basicity-earth oxide modifier, and the cyan light emission can be finally achieved.