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1 at% Ce3+-doped Gd3Ga2Al3O12 (GGAG) single crystals were grown by an optical floating zone (OFZ) method and a traveling solvent floating zone (TSFZ) method. To reveal their structure and chemical composition homogeneity, X-ray diffraction (XRD) and high-resolution inductively coupled plasma atomic emission spectrometry (ICP-AES) were conducted on the as-grown Ce:GGAG crystals at 4 different positions along the growth direction. Compared with the Ce:GGAG crystals grown by the OFZ method (Ce:GGAG-OFZ), the Ce:GGAG crystals grown by the TSFZ method (Ce:GGAG-TSFZ) presented better Ce3+ distribution homogeneity which varied from 0.21 to 0.29 at%. However, the segregation coefficient of Ce3+ in Ce:GGAG-OFZ was found to be higher than that in Ce:GGAG-TSFZ, revealing a different solidification rate between them. The comparison study shows that the photoluminescence (PL) intensity of Ce:GGAG-TSFZ is about twice higher than that of Ce:GGAG-OFZ and the maximum light yield (LY) of 35 340 photons per MeV also occurs in the former. Trap depths were measured to be 0.70 eV and 0.98 eV by TL glow curves. The LY value of Ce:GGAG-TSFZ along the growth direction fluctuated to a lesser extent with respect to that of Ce:GGAG-OFZ; the latter decreases gradually along the growth direction. It is concluded that the TSFZ method helps to improve the homogeneity of crystal composition when growing crystals with multiple compositions or incongruent compounds. [ABSTRACT FROM AUTHOR]

Uniquely, thiourea dioxide not only can reduce carbonyl compounds but also generate an oxidant to trigger luminol chemiluminescence. Herein, derivatization-free carbonyl compound detection using bifunctional chemiluminescence coreactant thiourea dioxide has been developed for the first time with the second most crucial flavor benzaldehyde as a representative. [ABSTRACT FROM AUTHOR]

Ce0.03Gd2.97Ga2Al3O12 (Ce:GGAG) single crystals were successfully grown by the traveling solvent floating zone method (TSFZ). A series of compositions, where the mole ratio is Gd2O3 : Al2O3 = 25 : 75, 27 : 73, 29 : 71, were investigated as solvents. The 25 mol% Gd2O3-75 mol% Al2O3 solvent component was found to be the most effective in stabilizing the molten zone to obtain a crystal rod with uniform diameter. The crystal cracks were relieved clearly due to the improved molten zone stabilization during the crystal growth process. XRD patterns of the obtained crystals prove the garnet structure without any evident second phase. The characteristic Ce3+ emission located at around 540 nm was presented in the photoluminescence and X-ray excited luminescence spectra. The scintillation light yield reaches up to 34 132 pho MeV−1 and scintillation decay time was optimized to 64 ns with a high fast decay component of about 85%. The TSFZ method demonstrated the growth feasibility of Ce:GGAG crystals that have an incongruent-melting trend with lower Ga/Al ratio in the compositions. [ABSTRACT FROM AUTHOR]

Management of CO2 has been attracting great attention in this century. Reaction of CO2 with 2-haloanilines and isocyanides is an attractive way for both converting CO2 and producing quinazolinones, which are key intermediates for the synthesis of various biologically active products. However, the heterogeneous and relatively inert nature of CO2 with 2-haloaniline and isocyanide reactants limits the types of suitable catalysts. Herein, we use metal–organic frameworks (MOFs) as a "microreactor", in which Pd(PPh3)2Cl2 is well-dispersed as a single-molecular catalyst, and the reactants react in the molecular level through a "quasi-homogeneous" way to convert CO2 into quinazolinones under mild conditions with both promising yields over homogeneous catalysts and good recyclability as a heterogeneous reaction. The MOF-assisted single-molecular catalysis strategy should contribute to CO2 conversion, production of quinazolinone-type bioactive intermediates, and the epochal development of "homo-and-heterogeneous" catalysis. [ABSTRACT FROM AUTHOR]

The Y2Si4N6C:Ce3+ carbidonitride phosphor has been successfully synthesized via a novel acid-driven carbonization and carbothermal reduction nitridation method (ADC–CRN). This novel approach for Y2Si4N6C:Ce3+ promises lower heating temperature and shorter heating time than classical methods, indicative of a cost-effective and facile way to search for new silicon-based carbidonitrides. In contrast to Ce3+ activated (oxy)nitrides showing blue-green emissions, Y2Si4N6C:Ce3+ exhibits an individual green-yellowish emission band centered at 550 nm which is ascribed to the incorporation of highly covalent C4− into the host lattice. The sp3 hybrid C4− was identified through high resolution electron energy loss spectroscopy analysis (EELS). Direct evidence for sole substitution of Ce3+ for Y3+ in Y2Si4N6C is represented for the first time using electron paramagnetic resonance (EPR) spectra. The red shift induced by the increasing Ce3+ content in Y2Si4N6C is reasonably deduced by the energy transfer model of intra-Ce3+ and inter-Ce3+ ions. A pc-w-LED packaging was fabricated via a combination of the yellow Y2Si4N6C:Ce3+ and blue La2Si4N6C:Ce3+ phosphors prepared using a 365 nm n-UV chip. The w-LED device shows a good color rendering index (Ra), CIE chromaticity coordinates and correlated color temperature (CCT) of 83.8, (0.3258, 0.3314) and 5819 K, respectively. These results suggest that Y2Si4N6C:Ce3+ has great potential for use in UV-LED-driven white emitting diodes. [ABSTRACT FROM AUTHOR]

A new Eu2+ activated, G-type La2Si2O7 phosphor was synthesized successfully via a novel SiC-reduction route. The valence state of the Eu2+ ions was identified with XRD and XPS analysis and the luminescence spectrum presented Eu2+ broad bands. The G-La2Si2O7:Eu2+ (LPS:Eu2+) phosphor exhibited tunable emission colors depending on the excitation wavelength or the Eu concentration, enabling the production of white light. The color tunable property is ascribed to the component ratio of the two specific luminescent centers, Eu(1) and Eu(2). Eu2+ ions prefer to occupy the La3+ crystallographic sites selectively, which was identified by electron paramagnetic resonance (EPR) spectroscopy. Furthermore, the relative emission intensity of the phosphor at 100 °C and 160 °C can maintain 89% and 76% of the value measured at room temperature, which is much better than that of most of Eu2+ doped silicon oxides phosphors. The Eu(1) emission possesses a better fluorescence thermal stability than the Eu(2) emission, and an energy transition from Eu(1) to Eu(2) occurs. This better thermal stability and energy transition have been explained by the schematic configuration coordination. A w-LED device was fabricated by combining the prepared La2Si2O7:Eu2+ and commercial BaMgAl10O17:Eu2+ phosphors with a 365 nm n-UV chip. The w-LED device generates white light (color rendering index Ra = 93.9), and its CIE chromaticity coordinates and correlated color temperature (CCT) are (x, y) = (0.3429, 0.3523) and 5090 K, respectively. These results suggest that LPS:Eu2+ has a great potential for use in UV-LED-driven white emitting diodes. [ABSTRACT FROM AUTHOR]

Gd2Si2O7:Ce (GPS:Ce) and (Gd,La)2Si2O7:Ce (La-GPS:Ce) phosphors with different crystal structures, tetragonal, orthorhombic and triclinic, were synthesized via a sol–gel technique. The prepared samples have been systematically investigated using room temperature (RT) XRD, high temperature (HT) XRD, HRTEM, selected area electron diffraction (SAED) and EDS elemental analysis. The results show that the phase transition occurred at 1350–1450 °C and the tetragonal phase was a low-temperature metastable phase and the orthorhombic and triclinic structures were stable at high temperatures. It was observed that the three structures display completely different luminescence efficiencies under both UV lamp and X-ray excitation, but the decay time was not strongly dependent on the crystal structure. The luminescence thermo-stability and activation energy were also measured and calculated. The results indicate that the thermo-stability was strongly dependent on the crystal structure and the GPS:Ce-1500 °C sample showed the best thermo-stability. The three materials have potential application as a novel type of scintillator. [ABSTRACT FROM AUTHOR]

In the present study, the crystallization of commercial-grade isotactic polypropylene (iPP) was studied by optical microscopy, scanning electron microscopy (SEM) and wide-angle X-ray diffraction (WAXD). It was found that isothermal crystallization of used iPP at 135 °C leads to the formation of pure α-iPP crystals. During non-isothermal crystallization at a cooling rate of 10 °C min−1, growth transformation of α into β-iPP occurs at the growth front of α-iPP spherulites. This is not common and has only been found during crystallization in a temperature gradient. The observed αβ-iPP growth transformation is confirmed to be a result of the existence of some impurities, which exhibited their ability to nucleate β-iPP. The ability of the impurities to nucleate β-iPP is dependent on concentration and temperature. Therefore, interlamellar rejection of the impurities caused by fast cooling (40 °C min−1) cannot induce the αβ-iPP growth transformation. On the other hand, even though isothermal crystallization of iPP at 135 °C can result in the accumulation of impurities at the spherulite growth front, it still cannot induce the αβ-iPP growth transformation at a low concentration. [ABSTRACT FROM AUTHOR]

The lack of efficient electrocatalysts for the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) has been a fatal issue for the development of metal–air batteries in large-scale commercialization. In this paper, spinel CoFe2O4 (CFO) nanoparticles were successfully in situ grown onto rod-like ordered mesoporous carbon (RC) by a facile, scalable hydrothermal method, followed by annealing at different temperatures. The as-acquired CFO/RC nanohybrid pyrolyzed at 400 °C (CFO/RC-400) has a high specific surface area (150.3 m2 g−1) and two sets of uniform mesopore systems (3.38 and 19.1 nm), all of which are favorable for the improvement of the electrocatalytic activity. The hybridization of CFO nanoparticles and the RC matrix results in increased ORR and OER electrocatalytic activity of the CFO/RC nanohybrids, which is significantly superior to that of unsupported CFO nanoparticles and pure RC. CFO/RC-400 shows better catalytic activity for the ORR with a direct four-electron reaction pathway than those prepared at other temperatures in terms of the onset potential and limiting current density. Furthermore, the CFO/RC-400 nanohybrid exhibits outstanding durability for both the ORR and OER, and can outperform commercial Pt/C. The excellent bifunctional electrocatalytic activities of the CFO/RC nanohybrids are mainly owing to the hierarchical mesoporous structures of the nanohybrids and strong coupling between the CFO nanoparticles and the RC matrix. [ABSTRACT FROM AUTHOR]

A series of (Ba,Sr)TiO 3 phosphors singly doped with Eu 3+ and Dy 3+ were successfully synthesized using the nitrate pyrolysis method at 750 °C. Eu 3+ or Dy 3+ single-doped BaTiO 3 retained the tetragonal crystal structure of the host, while the Sr 2+ -substituted (Ba,Sr)TiO 3 :RE 3+ (RE 3+ = Eu 3+ or Dy 3+ ) experienced a phase transformation from tetragonal to cubic phase with a unit cell shrinkage. For Eu 3+ doped phosphors, BaTiO 3 : x Eu 3+ ( x = 0.02-0.10) exhibited red photoluminescence and the highest intensity of emission belonged to the optimal-doped BaTiO 3 : x Eu 3+ ( x = 8 mol%). Moreover, the substitution of 30 mol% Sr 2+ for Ba 2+ (that is Ba 0.7 Sr 0.3 TiO 3 : x Eu 3+ , x = 8 mol%) further enhanced the emission intensity of BaTiO 3 : x Eu 3+ ( x = 8 mol%). For Dy 3+ doped phosphors, BaTiO 3 : x Dy 3+ ( x = 0.02-0.10) showed yellow photoluminescence and the highest light intensity was from the optimal-doped BaTiO 3 : x Dy 3+ ( x = 4 mol%). In addition, the substitution of 20 mol% Sr 2+ for Ba 2+ (the phosphor Ba 0.8 Sr 0.2 TiO 3 : x Dy 3+ , x = 4 mol%) induced further increase in emission intensity of BaTiO 3 : x Dy 3+ ( x = 4 mol%). The emission intensities at higher temperature of 100 °C retained about 70% and 90% of the initial values at room temperature (RT) for the optimal BaTiO 3 : x Eu 3+ ( x = 8 mol%) and BaTiO 3 : x Dy 3+ ( x = 4 mol%) phosphors, respectively, while the emission intensities at the temperature of 100 °C retained about 60% and 80% of the initial intensities at RT for the optimal Sr 2+ -substituted Ba 0.7 Sr 0.3 TiO 3 : x Eu 3+ ( x = 8 mol%) and Ba 0.8 Sr 0.2 TiO 3 : x Dy 3+ ( x = 4 mol%) phosphors, respectively. It is worth noting that on cooling down to RT again from 210 °C, the BaTiO 3 : x Dy 3+ ( x = 4 mol%) phosphor exhibited excellent luminescent thermal stability (with a high activation energy of 0.387 eV) and the strongest recovery (∼95%) of PL emission among the series of phosphors. The as-prepared phosphors with optimal compositions would be good candidates for the applications in lighting, display, and related fields., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)