Phosphor System Research Articles

Red luminescence Ca1-xLa2x/3TiO3:Eu3+ phosphor with high quantum efficiency for ultraviolet-based white light-emitting diodes

The photoluminescence properties and internal quantum efficiency (IQE) of Ca1-xLa2x/3TiO3:Eu3+ were investigated in this paper. In the excitation spectra of Ca1-xLa2x/3TiO3:Eu3+, several peaks were located from 360 to 535 nm which were attributed the 4f- 4f transitions of Eu3+. In the emission spectra, the strong emission peaks were located at 591 and 616 nm which were originated from the magnetic dipole and electric dipole transitions of Eu3+, respectively. Therefore, phosphor could be excited effectively in the near-ultraviolet light and emit a satisfactory red light. When the value of x was 0.1, the red emission intensity of Ca0.9La0.067TiO3:1 mol%Eu3+ was enhanced two times than that of CaTiO3:1 mol%Eu3+. For Ca0.9La0.067TiO3:Eu3+ (x = 0.1) phosphor, the optimal doping concentration was 5 mol%. The Ca0.9La0.067TiO3:5 mol%Eu3+ phosphor had a higher IQE compared with the Y2O2S:Eu3+ commercial phosphor (IQE: 35%) and reached as high as 83.7%. The CIE coordinates of Ca0.9La0.067TiO3:5 mol% Eu3+ were (0.636, 0.364). The electroluminescence spectrum showed the corresponding correlated color temperature (CCT) and color rendering index (Ra) values of white light-emitting diode (WLED) devices were 6295 K and 94.4, respectively. This result was much higher than the traditional WLED, which was coated with YAG:Ce3+ phosphors (CCT = 5716 K, Ra = 76). As a result, the Ca1-xLa2x/3TiO3:Eu3+ phosphor system was expected to become the red part of the WLED device.

Review—Mn4+-Activated Red and Deep Red-Emitting Phosphors

Mn4+-activated phosphors are a new class of non-rare earth phosphors and are alternative to commercial Eu2+-activated nitride/oxynitride phosphors with growing interest in various applications. In this review article, the structural and photoluminescence (PL) properties of various Mn4+-activated phosphors have been discussed. The host materials considered here can be roughly classified into five groups; fluorides, oxides, oxyfluorides, and two fluorine compounds. Phosphors of each group can also be classified into totally eleven subgroups from their different PL spectral features, e.g., whether an appearance of the zero-phonon line (ZPL) emission peak or not. The ZPL emission and absorption energies of the Mn4+ ions have been determined from the PL and PL excitation spectra using the Franck−Condon analysis method within the configurational-coordinate (CC) model. These results are used to obtain reliable phosphor parameters, i.e., the crystal-field (Dq) and Racah parameters (B and C), of the Mn4+ ions in the various host materials. The PL intensity vs temperature data, together with those of the luminescence lifetimes, are modeled on the basis of the CC model, and an excellent agreement has been achieved if not only the optical phonon but also the acoustic phonon contribution is taken into consideration in the conventional thermal quenching model. Effects of the hydrostatic pressure and dopant concentration on the PL spectral features are also discussed. Finally, key properties of the Mn4+-activated phosphors are discussed for use of such red and deep red-emitting phosphor systems in warm w-LED and indoor plant cultivation applications.

Bi(III)-Catalyzed Enantioselective Allylation Reactions of Ketimines

SummaryChiral homoallylic amines not only are found in pharmaceutically relevant compounds but also serve as versatile building blocks for chemical synthesis. However, catalytic allylation of ketimines with allylboronates, an attractive approach to synthesize chiral homoallylic amine scaffolds remain scarce. Herein, we develop a highly enantioselective allylation of isatin-derived ketimines with boron allylation reagents catalyzed by a Bi(OAc)3-chiral phosphoric acid catalyst system. The reactions are remarkably efficient and mild, most of which were completed in less than an hour at room temperature with only 1/2 mol% (Bi(OAc)3/CPA) catalyst loading. A wide range of chiral 3-allyl 3-aminooxindoles were obtained in excellent yields and enantioselectivities. The synthetic utility was demonstrated by efficient formal synthesis of (+)-AG-041R and (−)-psychotriasine. Preliminary mechanism was studied by control experiments and theoretical calculations.

Asymmetric 1,2-Dicarbofunctionalization of Alkenes with Copper/Chiral Phosphoric Acid System

Asymmetric 1,2-Dicarbofunctionalization of Alkenes with Copper/Chiral Phosphoric Acid System

Cs2NaBiCl6:Mn2+—A New Orange-Red Halide Double Perovskite Phosphor

In this work, we report on the promising photoluminescent behavior of the cubic double perovskite Cs2NaBiCl6 doped with Mn2+ ions. Localized excitations centered on Bi3+ ions in the host lattice strongly absorb near-UV light. In the undoped host compound, only very weak photoluminescence is observed, but in manganese-doped samples, energy transfer from Bi3+ to Mn2+ leads to intense orange-red photoluminescence. A broad emission peak centered at 590 nm is assigned to the 4T1 → 6A1 transition of octahedrally coordinated Mn2+. The excitation spectrum contains peaks at 294 and 354 nm that arise from 6s2 → 6s16p1 excitations of Bi3+ ions. If the chloride ions are partially replaced by bromide ions, the strongest excitation peak red-shifts to 375 nm. The lack of expensive reagents and toxic elements and the ability to tune the excitation and emission spectra through chemical substitution make Cs2NaBiCl6–xBrx:Mn2+ a promising phosphor system.

Binaphthol-derived phosphoric acids as efficient organocatalysts for the controlled ring-opening polymerization of γ-benzyl-l-glutamate N-carboxyanhydrides

Despite great progress, it is still one attractive topic to explore new controlled ring-opening polymerization method to fabricate well-defined polypeptides. Considering the activation of organophosphates and the polymerization characteristics of N-carboxyanhydrides (NCA), we herein describe an effective (S)-1,1′-binaphthyl-based phosphoric acid catalytic system that mediates controlled ring-opening polymerization (ROP) of γ-benzyl-l-glutamate N-carboxy-anhydrides (BLG-NCA) with primary amines as initiator. In the presence of (S)-2,2′-dimethoxyl-1,1′-binaphthyl phosphoric acid ((S)-1e), ROP with various feeding ratios of BLG-NCA to initiator afforded poly(γ-benzyl-l-glutamate) (PBLG) with expected molecular weights (5.0–32.7 kg/mol) and relatively narrow dispersities (Mw/Mn = 1.05–1.16). The kinetics and chain extension experiments were conducted to identify that (S)-1e-catalyzed ROP of BLG-NCA in a controlled/living manner. A probable interaction between (S)-1e and the amine group of initiator/polymer chain-end was verified from 1H NMR, 31P NMR experiments. A plausible phosphate-ammonium mode catalyzing ROP of BLG-NCA was discussed.

Synthesis and catalytic activity of vanadium phosphorous oxides systems supported on silicon carbide for the selective oxidation of n-butane to maleic anhydride

VPO catalysts supported on silicon carbide were prepared using the solvothermal method. A decrease the reaction temperature by 70 °C under application of SiC, prepared from sucrose and fumed silica, as a support for an active VPO phase compared to a bulk VPO catalyst prepared under similar synthesis conditions was demonstrated. A twofold increase of the productivity towards maleic anhydride was reached. The higher specific reaction rate of n-butane oxidation over prepared supported VPO-SiC systems compared to the bulk VPO catalyst was shown. Use of an environmentally safe support allowed to reduce an amount of active vanadium-containing phase, and an application of the solvothermal method decreased the synthesis duration and an amount of organic solvent compared to the traditional approaches to the synthesis of VPO systems.

QUANTITATIVE DETERMINATION OF PHENOL CARBOXYLIC ACIDS IN POMEGRANATE FRUIT PULP BY THE HIGH-PERFORMANCE LIQUID CHROMATOGRAPHY WITH ULTRAVIOLET DETECTION

Objective: Pomegranate (Punica granatum L.) is a broadly used plant possessing a wide range of medicinal properties. In this research, we have mainly focused on the investigation of phenolic compounds of pomegranate fruit pulp (PFP).Methods: Fresh fruits of “Çəhrayı Gülöyşə,” “Kizil-anor,” and pomegranate varietal mixture were used as samples. High-performance liquid chromatography-ultraviolet (HPLC-UV) analysis of phenol carboxylic acids was performed with metal column Kromasil® C18 (4.6×250 mm, particle size 5 μm) and the acetonitrile-water-concentrated acid phosphoric system (400:600:5) under isocratic elution conditions (flow rate of 0.5 ml/min). Detection was carried out using a UV detector “GILSTON” UV/Visible model 151 at a wavelength of 280 nm.Results and Discussion: As a result of our research, we proposed chromatographic conditions for the separation of phenolic compounds, the conditions for sample preparation of PFP. Procedure for determination of phenolic carboxylic acids total content in terms of gallic acid by HPLC-UV method was developed. According to the obtained data, the content of phenolic carboxylic acids should be at least 0.7%.Conclusion: Procedure for the quantitative determination of gallic acid using the HPLC-UV method was developed. This method which can be used in the standardization of new medicinal plant raw materials - PFP, as well as extract preparations based on it in the future.

QUANTITATIVE DETERMINATION OF PHENOL CARBOXYLIC ACIDS IN POMEGRANATE FRUIT PULP BY THE HIGH-PERFORMANCE LIQUID CHROMATOGRAPHY WITH ULTRAVIOLET DETECTION

Objective: Pomegranate (Punica granatum L.) is a broadly used plant possessing a wide range of medicinal properties. In this research, we have mainly focused on the investigation of phenolic compounds of pomegranate fruit pulp (PFP).Methods: Fresh fruits of “Çəhrayı Gülöyşə,” “Kizil-anor,” and pomegranate varietal mixture were used as samples. High-performance liquid chromatography-ultraviolet (HPLC-UV) analysis of phenol carboxylic acids was performed with metal column Kromasil® C18 (4.6×250 mm, particle size 5 μm) and the acetonitrile-water-concentrated acid phosphoric system (400:600:5) under isocratic elution conditions (flow rate of 0.5 ml/min). Detection was carried out using a UV detector “GILSTON” UV/Visible model 151 at a wavelength of 280 nm.Results and Discussion: As a result of our research, we proposed chromatographic conditions for the separation of phenolic compounds, the conditions for sample preparation of PFP. Procedure for determination of phenolic carboxylic acids total content in terms of gallic acid by HPLC-UV method was developed. According to the obtained data, the content of phenolic carboxylic acids should be at least 0.7%.Conclusion: Procedure for the quantitative determination of gallic acid using the HPLC-UV method was developed. This method which can be used in the standardization of new medicinal plant raw materials - PFP, as well as extract preparations based on it in the future.

Tetradic phosphor white light with variable CCT and superlative CRI through organolead halide perovskite nanocrystals.

In this work, the emission spectral range of halide perovskite nanocrystals is extended from violet to infrared, the widest emission range for halide perovskites to date. This range extension was made possible by a cost-effective solution-based synthesis process that only involves two halides [MAPb(BrxI1−x)3 and MA = CH3NH3]. Furthermore, the correlated-color temperature (CCT) of white light is tuned by blending an appropriate fraction of the as-synthesized blue, green, yellow, and red emitting nanocrystals. This represents one of the first applications of a tetradic phosphor system for maximizing the color rendering index (CRI) for this material. The CCT ranges from warm to cool white (2759–6398 K) and the CRI has a maximum value of 93.95. Thus, this fourfold phosphor approach demonstrates that halide perovskites are promising alternatives to conventional phosphors in the search for low-cost and high-quality white light sources in the next generation of white lighting technology.

Photoluminescence investigation of novel reddish-orange phosphor Li2NaBP2O8:Sm3+ with high CP and low CCT

The exploration of appropriate inorganic phosphors with high color purity (CP) and low correlated color temperature (CCT) has always been a hot issue for solid state light applications. In this work, we have developed series of Sm3+ doped Li2NaBP2O8 (abbreviated as: LNBP) phosphors by means of the solid state synthesis route. The crystalline phase compositions, micromorphology, valence state of elements as well as photoluminescence properties were systematically illustrated. Upon the excitation wavelength at 400 nm, emission peaks are located at 561，597，643 and 699 nm, corresponding to the 4G5/2 → 6H5/2, 6H7/2, 6H9/2 and 6H11/2 transitions of Sm3+ in the same order. The optimal doping amount of Sm3+ ions is 2 mol% for the reddish-orange photoluminescence of the LNBP:Sm3+ phosphor system. The critical energy transfer distance, mechanism of concentration quenching, CIE chromaticity coordinate, CP, CCT and internal quantum efficiency were extensively investigated. The title product might be considered as a promising candidate of phosphor in near UV-based warm white LEDs.

Coherence Properties of Shallow Donor Qubits in ZnO

Defects in crystals are leading candidates for photon-based quantum technologies, but progress in developing practical devices critically depends on improving defect optical and spin properties. Motivated by this need, we study a new defect qubit candidate, the shallow donor in ZnO. We demonstrate all-optical control of the electron spin state of the donor qubits and measure the spin coherence properties. We find a longitudinal relaxation time T$_1$ exceeding 100 ms, an inhomogeneous dephasing time T$_2^*$ of $17\pm2$ ns, and a Hahn spin-echo time T$_2$ of $50\pm13$ $\mu$s. The magnitude of T$_2^*$ is consistent with the inhomogeneity of the nuclear hyperfine field in natural ZnO. Possible mechanisms limiting T$_2$ include instantaneous diffusion and nuclear spin diffusion (spectral diffusion). These results are comparable to the phosphorous donor system in natural silicon, suggesting that with isotope and chemical purification long qubit coherence times can be obtained for donor spins in a direct band gap semiconductor. This work motivates further research on high-purity material growth, quantum device fabrication, and high-fidelity control of the donor:ZnO system for quantum technologies.

Status of the AMS system at Yamagata University

An accelerator mass spectrometry (AMS) system and an automated graphitization line were installed at Yamagata University (YU) in 2009. Approximately 2000 samples are measured per year using the YU-AMS system. The long-term stability of the system was assessed by measuring the standard sample IAEA-C7 graphitized by the automated graphitization line. In March 2014, a second automated graphitization line and an additional ion source for the YU-AMS system were installed to meet the requirement of 14C measurement for pharmacological and medical applications. A phosphoric acid treatment system was also developed for the radiocarbon dating of calcium carbonate (CaCO3) in shell and coral samples. Performance tests on the new YU-AMS system were carried out by measuring the C-series standard samples (C1-C9) and oxalic acid II (HOxII) obtained from IAEA and NIST, respectively. The results of the 14C concentration pMC are in good agreement with the consensus values. Performance tests for medical applications were also carried out by measuring the 14C concentration of 14C-glucose in human plasma.

Improved photo-luminescence by co-doped lithium in the phosphor system CeO2:Eu3+

Li+ co-doping is used as a prevalent way to improve the luminescent intensity of CeO2:Eu3+ [25]. Here, we investigate the structural and luminescent properties of CeO2:Eu3+ by the different co-doping ways of Li+ ions, including the direct co-doping of Li+ by hydro-thermal co-precipitation and the indirect co-doping of Li+ by a post calcining of Li2CO3. The different co-doping ways of Li+ ions was found to cause different effect on structure and luminescence of CeO2:Eu3+ phosphor. The result showed opposite trend with conventional explanations [25] where the substitution of Ce4+ with doped Li+ ions are the prime reason for luminescence intensity enhancement. Oxygen vacancies should be formed due to the charge imbalance. It is found that the Li+ direct co-doped CeO2:Eu3+ didn’t improve the crystallization of the samples due to the increase of oxygen vacancies, as is supported by X-ray diffraction(XRD) patterns and Raman spectra. Meanwhile, the spectroscopic investigations reveal that the Li+ direct co-doped CeO2:Eu3+ lead to less asymmetry around Eu3+ and lower luminescence. However, results show that the indirect co-doping of Li+ lead to a increase of crystallinity and decrease in oxygen vacancies concentration. The luminescent intensity of CeO2:Eu3+ can be significantly enhanced by indirect co-doping of Li+. Consequently, we reason that the enhanced luminescence mainly results from a increase of crystallinity and decrease in oxygen vacancies concentration due to the flux effect of Li+ ions, instead of the substitution of Ce4+ with doped Li+ ions.

Water molecules on the liquid superlubricity interfaces achieved by phosphoric acid solution

The superlubricity mechanism of phospholipid molecules on biological surfaces and interfaces has been receiving much attention. Since the superlubricity can be achieved with a phosphoric acid aqueous solution, the interaction of the phosphate group with the water molecule is considered to be the key to bio-lubrication. However, no direct evidence has been offered to distinctly interpret the underlying mechanism of superlubricity, due to the limitations in the method for the detection of interfacial molecules, especially water molecules on the interface. By using sum-frequency generation (SFG) vibrational spectroscopy, which is extremely sensitive to interfacial molecules, the authors were able to explore the underlying microscopic mechanism for superlubricity in a phosphoric acid system, which might be related to interfacial water molecules. By trapping the phosphoric acid aqueous solution between silicon nitride and silica surfaces, they discovered that phosphoric acid could exercise a great influence on the ordered structure of interfacial water molecules, contributing to SFG spectral changes in the broad O–H bond stretching region. This work directly revealed the interfacial interaction between water and phosphoric acid molecules in liquid superlubricity interfaces, which could shed new light on the microscopic mechanism of liquid superlubricity.

The effect of ligand-to-Eu3+ charge-transfer transitions (LMCT) on the photoluminescence intensity of M2SiO4: Eu3+ (M = Ca, Zn) type phosphors

Abstract In this study, silicate systems, M2SiO4 (M = Ca, Zn) were produced by solid state reaction and doped with 1 mol% Eu3+ rare-earth ion. Their heat treatments, which were conducted at 1200 °C and above for minimum 3 hours under an open atmosphere, were applied according to the DTA/TG results. Powder X-ray diffraction XRD analyses were performed to determine the phase properties of the phosphor systems after the sintering process. It was proved that the structures of two of the phosphor systems were well formed in except that the Zn2SiO4 had some ZnO secondary phases. The expected photoluminescence (PL) results were presented and the transitions of the Eu3+ ions were observed for both phosphors.

Nutrient Dependent Cross-Kingdom Interactions: Fungi and Bacteria From an Oligotrophic Desert Oasis.

Microbial interactions play a key role in ecosystem functioning, with nutrient availability as an important determinant. Although phylogenetically distant bacteria and fungi commonly co-occur in nature, information on their cross-kingdom interactions under unstable, extreme environments remains poor. Hence, the aims of this work were to evaluate potential in vitro interactions among fungi and bacteria isolated from a phosphorous oligotrophic aquatic system in the Cuatro Ciénegas Basin, Mexico, and to test the nutrients-based shifts. We assessed growth changes in bacteria (Aeromonas and Vibrio) and fungi (Coprinellus micaceus, Cladosporium sp., and Aspergillus niger) on co-cultures in relation to monocultures under diverse nutrient scenarios on Petri dishes. Interactions were explored using a network analysis, and a metabolome profiling for specific taxa. We identified nutrient-dependent patterns, as beneficial interactions dominated in low-nutrients media and antagonistic interactions dominated in rich media. This suggests that cross-kingdom synergistic interactions might favor microbial colonization and growth under low nutrient conditions, representing an adaptive trait to oligotrophic environments. Moreover, our findings agree with the stress-gradient hypothesis, since microbial interactions shifted from competition to cooperation as environmental stress (expressed as low nutrients) increased. At a functional level consistent differences were detected in the production of secondary metabolites, agreeing with plate bioassays. Our results based on culture experiments, provides evidence to understand the complexity of microbial dynamics and survival in phosphorous-depleted environments.

Synthesis and photoluminescence characteristics of near white light emitting CaB2O4:Dy3+, Li+ phosphor

A series of Dy3+ doped CaB2O4 phosphors were synthesized by conventional solid state reaction method. XRD analysis reveals that the crystal structure of the sample was well matched with the orthorhombic CaB2O4. FTIR spectra characterize various vibrational bonds present in the samples. SEM images indicate that the prepared phosphor have microstructure nature with irregular morphology. UV-Vis-NIR optical absorption spectrum of CaB2O4:Dy3+, Li+ phosphor was analyzed on the basis of Judd-Ofelt theory and the J-O intensity parameters (Ωλ) were evaluated. The radiative properties such as transition probability (AR), stimulated emission cross-section (σe) etc. were calculated. Excitation spectra reveal strong transitions from the ground state 6H15/2 of Dy3+ ions. The prepared phosphor samples provide emission in blue (4F9/2 → 6H15/2), yellow (4F9/2 → 6H13/2) and red (4F9/2 → 6H11/2) regions under an excitation wavelength of 350 nm. The alkali metal Li+ was added to maintain the charge neutrality of the phosphor system which also enhances the luminescence intensity of Dy3+ ions. CIE chromaticity studies show that the prepared phosphor samples are exhibiting near white light emission and corresponding correlated color temperature (CCT) were appearance in cool region. The results suggest that as-synthesized phosphors have potential application in the field of NUV white light emitting diodes (W-LEDs).

Microphotographic Assessment of Enamel Surface using Self-Etching Primer and Conventional Phosphoric Acid: An In vitro Study.

Introduction:Conventional acid-etching method irreversibly removes several microns of enamel surface and also involves many steps. Hence, a simplified technique that minimizes enamel loss, improves adhesion procedures, prevents saliva contamination, and saves chair time, thereby producing clinically useful bond strength, would be valuable.Aim:To assess and compare the bonding mechanism of a self-etching primer (SEP) to that of phosphoric acid on enamel of the human permanent teeth by a scanning electron microscope (SEM).Materials and Methods:Thirty freshly extracted premolars were randomly divided into two groups of fifteen teeth each – the control group I (phosphoric acid) and experimental group II (self-etching primer). Brackets were bonded using Transbond XT adhesive on the buccal surfaces of the teeth after etching and priming according to their respective protocols. The teeth were then sectioned and the samples were subjected to a protocol of demineralization cycles. After complete dissolution of dental tissues, the specimens were gold sputter coated and evaluated under SEM.Results:A characteristically uniform etch pattern was seen in the resin samples of the phosphoric acid/Transbond XT primer group, which revealed increased roughness and resin tags penetrating the demineralized enamel surface, whereas with Transbond Plus SEP, a regular resin tag distribution was observed which showed less magnitude when compared with the control group.Conclusion:From the study, it was concluded that Transbond Plus SEP produced an etch pattern which was more conservative than conventional phosphoric acid system.

Starch Phosphate Microgels for Controlled Release of Biomacromolecules

Gel-forming starch phosphates with a content of acidic phosphate groups ranging from 2.1 to 3.8 mmol/g were obtained in a phosphoric acid-urea system. The rates of starch phosphate degradation in buffer solution in the absence of amylase and in the presence of this enzyme were investigated in vitro. Starch phosphate gels were shown to be prone to enzymatic degradation. However, the rate of biodegradation decreased gradually as the content of phosphate groups increased. The use of microgels with average particle sizes in the range of 7.8–60.1 μm for the production of controlled-release preparations of interferon-alpha 2b has been demonstrated to be possible in principle.