Single-phase white light-emitting CaxBa(9–x)Lu2Si6O24:Eu2+/Mn2+ codoped phosphors were successfully synthesized, and their photoluminescence properties were experimentally determined. The analysis of the experimental results suggests that the partial substitution of Ba2+ ions by smaller Ca2+ ions alters the distribution of the Eu2+ luminescence center among the three available Ba2+ sites in the host lattice, which enables the emission to be efficiently tuned from blue to blue-green-yellow region. The incorporation of Mn2+ ions resulted in a red light emission at around 618 nm, through energy transfer from Eu2+ to Mn2+ ions via dipole–dipole interactions. The incorporation of Ca2+ and Mn2+ ions also resulted in improved thermal stability. The results qualify the produced CaxBa(9–x)Lu2Si6O24:Eu2+/Mn2+ composition as a potential ultraviolet-convertible white light-emitting phosphor.Topics: Crystal structure; Diffraction; Energy transfer; Luminescence; Luminescence; Optical materials; Optical properties; Plasmonic and Photonic Structures and Devices; Quantum transition; Reaction (Inorg.); Thermal properties;

•A novel method of fabricating an all-ceramic hydrophobic membrane is proposed.•The terminal Si-CH3 and high roughness in the surface lead to a high contact angle.•Covalent skeleton modifier and the tight coupling create the robust hydrophobicity.•Excellent long-term stability and good recovery ability was confirmed in MD process.A novel method of fabricating an all-ceramic hydrophobic membrane is proposed. First, porous β-Sialon planar ceramic membrane was prepared by a phase inversion and sintering method. Then, the β-Sialon ceramic membrane was coated with a uniform polydimethylsiloxane (PDMS) layer through a poly-condensation reaction. Finally, through post-heat treatment in N2 atmosphere, the polymer layer was transformed into a tough hydrophobic vesicular ceramic layer with strong covalent Si-O and Si-N skeleton and Si-CH3 terminal groups in the surface. High contact angles were measured between the water and the modified hydrophobic membrane, ~140°, attributed to the presence of terminal Si-CH3 groups, which were derived from the polymer, and the micro- and nano-hierarchical lotus leaf-like structure of the surface. The high hydrophobicity was perfectly maintained after a 24 h exposure of the produced membranes to humic acid, boiling water, aqueous solution of HCl, and benzene. Membrane distillation water desalination tests were also conducted. A water flux of 14.08 l/m2h was obtained at 90 °C, while the rejection rate was over 99% over the duration of the test that lasted for more than 70 h, which supports that the produced membrane had excellent long-term stability and good recovery ability.

•A feasible surface modification method is first applied on silicate phosphor.•A hydrophobic layer on Ba2SiO4:Eu2+ is formed via reaction with TEOS and PDMS.•The modified phosphor features superior stability in severe conditions at 150 °C.This paper proposes a simple and feasible surface modification method to suppress the moisture-induced degradation of the green-emitting phosphor Ba2SiO4:Eu2+ (BSO:Eu2+), which hits its reliability very hard and restricts its wide commercialization in WLEDs. A hydrophobic surface layer was formed on the surface of this phosphor via hydrolysis and polymerization of tetraethylorthosilicate (TEOS) and polydimethylsiloxane (PDMS). The produced surface layer consisted of an amorphous silicon dioxide with a thickness of ∼2 nm along with the presence of −CH3 groups on the surface. The modified phosphor featured superior stability in high-pressure water steam conditions at 150 °C.Download high-res image (148KB)Download full-size image

Novel single-phase full-color-emitting Ba9Lu2Si6O24:Ce3+/Mn2+/Tb3+ phosphors were successfully synthesized by a high-temperature solid-state reaction method. Analysis of the X-ray diffractograms of the produced phosphors suggests that all the luminescence doping cations preferably occupy the Ba2+ sites in the host lattice. Li+ were used according to Ce3+ and Tb3+ concentration as a charge compensation regent. Under UV excitation, the single Ce3+-doped phosphor exhibits an intense blue emission band that peaks at 424 nm. In the co-doped phosphors, the experimental results suggest that an efficient energy transfer mechanism from Ce3+ to Tb3+ and Mn2+ results in the generation of a green emission in the Tb3+-doped phosphors and a red emission in the Mn2+-doped ones. The triple-doped phosphors, which contained specific concentrations of Ce3+, Mn2+, and Tb3+ ions, generated a tunable (in a wide range) white light which had good color rendering index values. Thermal behavior of the present phosphors was investigated which shows better characteristics. This result qualifies the produced powders as potential single-phase trichromatic white light-emitting phosphors.

•Both Ce3+ and Tb3+ ions occupy La3+ sites in CaLa4Si3O13 host.•The emission color shift from blue to green region in Ce3+/Tb3+ co – doped CaLa4Si3O13 phosphors.•The energy transfer efficiency is increase upto 93% with the increasing of Tb3+ concentration.•Energy transfer mechanism illustrate that dipole-dipole energy transfer are dominant from Ce3+ to Tb3+ ion.•The remaining intensity of green emission of Ce3+/Tb3+ co-doped CaLa4Si3O13 phosphors is 70% at 150 °C.Phosphors of CaLa4Si3O13 singly- and co-doped with Ce3+ and Tb3+, which are suitable for application in white LEDs, were successfully produced by using a high temperature solid state reaction method. Their apatite crystalline structure as well as their photoluminescent properties both at room temperature and at higher temperatures (up to 150 °C) were experimentally determined, which also allowed the determination of the energy transfer efficiency and mechanism in the host lattice from the sensitizer Ce3+ ions to the activator Tb3+ ions. The excitation spectra of the doped phosphors exhibited an intense, broad band from 200 to 420 nm, which is a good match for the UV and near-UV chip (350–420 nm). Under excitation with UV light, two distinct luminescence bands were recorded; a blue one centered at 433 nm, which is typical for Ce3+ emission, and a green one, which peaks at 552 nm, originated from 5D4 → 7F5 transition in Tb3+.

•A novel ceramic membrane covered by α-Si3N4 nanowires has been prepared.•Modified the membrane surface to superhydrophobic by inorganic SiNCO.•This membrane can be used in harsh environments (20 wt% NaCl solution, 90 °C).•The membrane has been used in membrane distillation for 500 h.The α-Si3N4 membrane was prepared by tape casting of silicon slurry, followed by calcination at 1300 °C in flowing NH3 gas. It comprised of α-Si3N4 nanowire of diameter 70 nm which were converted from silicon powder via the vapor–liquid–solid (VLS) growth mechanism. The surface of the obtained membrane was transformed from hydrophilic to superhydrophobic, with a high water contact angle of ~ 160°, by coating with a vesicular SiNCO nano-layer. The experimental results showed that nanowire structure also favored superhydrophobicity. Water desalination performance of the membrane was tested with a sweeping gas membrane distillation (SGMD) device. High water flux of 8.09 l m−2 h−1 was achieved for 20 wt% NaCl aqueous solution in the feed at 90 °C, which was maintained for more than 500 h.

Luminescent materials play an important role in making solid state white light-emitting diodes (w-LEDs) more affordable home lighting applications. To realize the next generation of solid-state w-LEDs with high color-rendering index (CRI), the discovery of broad band and long emission wavelength luminescent materials is an urgent mission. Regarding this, the oxonitridosilicate Y3Si5N9O with a high nitrogen concentration should be a suitable host material to achieve those promising luminescent properties. In this work, a phase-pure Ce3+-doped Y3Si5N9O was successfully synthesized through the carbothermal reduction and nitridation method. Y3Si5N9O:Ce3+ shows an emission maximum at 620 nm and an extremely broad emission band with a full-width at half-maximum (fwhm) of 178 nm. The electronic and crystal structure calculations indicate an indirect band gap of 2.6 eV (experimental value: 4.0 eV), and identify two Ce3+ sites with different local environments that determine the luminescence properties. The orange-emitting phosphor has the absorption, internal and external quantum efficiencies of 89.5, 17.2, and 15.6% under 450 nm excitation, respectively. The valence state of Ce, cathodoluminescence, decay time, and thermal quenching of the phosphor were also investigated to understand the structure–property relationships.

Nitrogen-doped γ-Ca2SiO4:Ce3+ phosphors were successfully produced by a solid state reaction method provided that the Ca/Si molar ratio was ≥2.05 and N-doping was simultaneously ≥0.75%. The factors that affect the β → γ phase transformation were also thoroughly investigated. Experimental results were obtained by XRD, FTIR, NMR, SEM, and TEM techniques, along with EDS and SAED analyses. First-principles theoretical calculations were also done. The results showed that the phosphors produced have high photoluminescence and thermal quenching properties, attributed to the covalent nature of the Si–N bond, and the optimum amount of nitrogen incorporation is 0.75%, whereas further increases in nitrogen content degrade the above properties, probably due to the increase in the formation of oxygen vacancies. It was also shown that γ-Ca2SiO4:Ce3+ is thermodynamically more stable than β-Ca2SiO4:Ce3+ after nitrogen doping. A dramatic shift in the emission from yellow to light-blue was recorded when the phosphors were heated to 800 °C. This was attributed to the migration of Ce3+ from Ca(1) to Ca(2) sites in the γ-phase, which is confirmed by 4f → 5d transition energy calculations.

The emission intensity of commercial red Sr2Si5N8:Eu2+ phosphor, which is used in white light-emitting diodes (LEDs), was enhanced by coupling with the localized surface plasmon (LSP) oscillation of nano-structured (nano-spheres and nano-rods) Ag particles produced by a seed growth method. Coatings of Ag nanoparticles mixed with phosphors on an epoxy substrate were prepared. The experimental results showed that spectral overlap occurs between the LSP resonance band of Ag nanoparticles and the excitation and emission spectra of the phosphor. The emission intensity was enhanced (∼25%) by the synergistic effect of Ag nano-spheres and nano-rods mixed in optimal proportions. The produced phosphors improved the quantum efficiency of red phosphors, which is a very important feature in white LED systems.

Novel microporous β-Sialon (Si6–zAlzOzN8–z, z = 1–4) ceramic hollow fiber membranes have been successfully prepared by a combined phase-inversion and sintering method. The influence of dispersant concentrations on the viscosity curve was first studied to obtain a stable precursor suspension. Different z value and sintering temperature were studied to get asymmetric hollow fibers with a good combination of high bending strength (369 MPa), suitable pore size (0.8 μm), large gas and water flux, which are suitable for membrane distillation (MD). The membranes also exhibited a much lower thermal conductivity. After modified to hydrophobic by grafting fluoroalkylsilane (FAS), the membranes were applied to vacuum membrane distillation (VMD) and direct contact membrane distillation (DCMD). They exhibited satisfactory water flux and a salt rejection rate of 99–100% for both methods. Most importantly, the permeate flux in DCMD reaches 63% of that in VMD due to the lower thermal conductivity, indicating their potential industrial applications.

Si–N co-doped Y3Al5O12:Ce3+ (YAG:Ce) phosphor was synthesized via a novel solid-state reaction method using CeSiO2N to simultaneously incorporate Si–N and Ce3+. The achieved phosphor exhibits increased red light component and better thermal quenching property. Additionally, an evident long afterglow luminescence was detected for the first time. The analysis of the experimental results (X-ray diffraction, photoluminescence, X-ray absorption near edge spectroscopy, infrared spectroscopy, and thermoluminescence) suggests that the Si–N was homogeneously incorporated into YAG host lattice and most of the Ce3+ ions were directly coordinated with nitrogen. The deeper trap depth and greater number of oxygen vacancies around Ce3+ are responsible for the significantly enhanced long afterglow in Si–N co-doped YAG:Ce phosphor.

Sr2SiO4:Eu2+ phosphors were synthesized by a conventional solid state reaction method. After a low amount of nitrogen (∼1 mol% of oxygen) was incorporated to modify the local coordination environment of Eu2+, the phosphor showed a single intense broad band emission centered at 625 nm under blue light (453 nm) excitation, and three emission bands (480, 555 and 625 nm) under ultraviolet irradiation. The incorporation of nitrogen was confirmed by X-ray photoelectron spectroscopy (XPS), Fourier-transform infrared spectroscopy (FT-IR) and absorption spectroscopy. 480 and 555 nm emissions originated from Eu2+ ions occupying the Sr(I) sites and Sr(II) sites in the Sr2SiO4 crystal, respectively, while 625 nm emission originated from the nitrogen coordinated Eu2+ ions. The local coordination structure around Eu2+ ions in the red phosphors was analyzed with the aid of density functional theory based first principles calculations. The analysis showed that nitrogen should preferentially substitute the O5′ sites around Eu2+ in Sr(II) sites, which agreed fairly well with the experimental results from the X-ray absorption fine structure (XAFS) and the electron paramagnetic resonance (EPR) spectra. The electronic structure analysis confirmed the lowered center of gravity of Eu 5d energy states and the broadened Eu 4f energy states, which are due to the tightened coordination environment and the hybridization of the 4f states of Eu and 2p states of nitrogen–oxygen, leading to a red emission. The novel nitrogen modified Sr2SiO4:Eu2+ could serve as a full color phosphor for near-UV LEDs or a red-emitting phosphor for blue LEDs.

Single-crystalline Cd3P2 nanowires (NWs) have been synthesized via a solution–liquid–solid (SLS) mechanism. The lengths of the resulting nanowires can be effectively tuned in the range of 180 nm and 5 μm, and the photodetectors made of the Cd3P2 nanowires exhibited a pronounced photoresponse with high stability and reproducibility.

Pure BaMgSiO4:Eu2+ phosphor, prepared by a solid state reaction method under N2 atmosphere, exhibited a strong green emission at 500 nm and a weak emission at 405 nm. Heat treatment under NH3 atmosphere causes changes in the PL intensity: the green emission at 500 nm gradually decreases and completely disappears after heat treatment for 3 h, whereas a new blue emission peak, centered at 445 nm, appears and becomes very strong. The results of the analyses with electron paramagnetic resonance (EPR), X-ray photoelectron spectroscopy (XPS), and X-ray absorption fine structure (XAFS) spectroscopy suggest that the heat treatment causes the generation of a large amount of oxygen vacancies. This resulted in the aforementioned color changes of the BaMgSiO4:Eu phosphor, which are confirmed by the results of DFT+U calculations. In particular, these calculations showed that Eu prefers to occupy Ba(3) sites, which are six coordinated to oxygen atoms. The emission at 500 nm was attributed to the 4f–5d transition energy of Eu in Ba(3) site, calculated as 2.54 eV. It was also shown that Eu 4f energy level decreases when oxygen is removed from the oxygen position adjacent to Eu, which results in a larger Eu 4f–5d transition energy and shorter wavelengths of emission peaks.

A simple and cost-effective method was proposed to synthesize nano-crystallized pure anatase titanium dioxide (TiO2) photocatalysts with a high thermal stability. The initial TiCl4 was reacted with a NaOH aqueous solution to form an amorphous sodium titanate, which was then transformed into an amorphous titanium dioxide hydrate through the replacement of Na+ by H+ using a HCl aqueous solution. After annealing, the pure nano-crystallized anatase TiO2 particles possessed a high thermal stability up to 900 °C. The high concentration of NaOH aqueous solution played an important role in preventing the precipitation of rutile TiO2 during hydrolysis process and promoting the formation of the nano-crystallized anatase TiO2. Samples calcined at 800 °C exhibited a significantly higher repeatable photocatalytic activity compared to the standard commercial photocatalyst P25 for the degradation of Rhodamine B in an aqueous suspension. This could be attributed to the synergistic effect of high crystallinity and mesoporous structure. The method is very simple, template-free, and cost effective, which makes it potential for the large-scale production.

•Energy-transfer from Ce3+ to Tb3+ in Al5O6N phosphors is first studied.•The presence of Ce3+ increases the emission of Tb3+.•The maximum value of energy-transfer efficiency was calculated as 98.3%.•Energy-transfer is predominantly governed by a dipole–dipole interaction mechanism.This paper presents the production of novel green-emitting Al5O6N:Ce3+,Tb3+ phosphors by a solid-state reaction method. The phosphors produced were well crystallized and had very good photoluminescence properties. In particular, they had blue and green emission bands under excitation with near-ultraviolet light. The analysis of the experimental results (i.e. emission and excitation spectra and decay curves) suggests the occurrence of an effective energy transfer from Ce3+ to Tb3+, which is predominantly governed by a resonant type mechanism via dipole–dipole interactions.

A facile solution-phase route was developed to synthesize a family of monodisperse Cu2Ge(S3–xSex) alloyed nanocrystals (NCs) with controlled composition across the entire range (0 ≤ x ≤ 3). The band gaps of the resultant NCs can be engineered by tuning the compositions with a nearly linear relationship between them. The band structures of the NCs were studied by cyclic voltammetry and UV–vis absorption spectroscopy. The conducting behavior was revealed to be p-type for these NCs by photoelectrochemical measurements. Their photovoltaic applicability was finally assessed by fabricating solar cells with the Cu2Ge(S2Se) NCs as light harvester and CdS nanorods as electron conducting materials.

•A facile method to synthesized high stable hollow spherical Sr2SiO4:Eu2+ green phosphor.•The Sr2SiO4:Eu2+ green phosphor shows strong emission intensity under UV and blue light excitation.•The h-BN protective film plays important roles in the formation of the spherical hollow structure of the phosphors.•This spherical phosphor could be used in white LED and other display techniques.The uniform hollow spherical Sr2SiO4:Eu2+ green emitting phosphors have been successfully synthesized using hollow silica spheres as templates by an h-BN protective method. The scanning electron microscopy (SEM) and transmission electron microscopy (TEM) results directly confirmed the existence of the hollow spherical structure with a narrow size distribution and a shell thickness of 15–25 nm. The h-BN protective film, observed by high resolution TEM, plays an important role in the formation of the hollow spherical morphology and the improvement of photoluminescence properties. Comparing with the Sr2SiO4:Eu2+ micron-phosphor prepared by the traditional solid state reaction method, the hollow spherical phosphor with nano-sized grains exhibits stronger green emission under ultraviolet–blue light excitation. This could be attributed to the elimination of surface defects by the h-BN coating. This research gives an economic and convenient way to synthesize uniform spherical phosphors with high quantum efficiency.

•The photoluminescence properties are sensitive to the host lattice.•Ba atoms have contribution to the emission intensity of the phosphor.•Ba atoms have larger contributions than other alkaline earth atoms.•5d states of Ba atoms provide extra states to that of Eu atoms.The photoluminescence properties are sensitive to the cations of the host lattice in many phosphors. We selected a typical oxonitridosilicate phosphor (Eu2+-doped Ba3Si6O12N2 green phosphor) to investigate this interesting phenomenon by using Cambridge Sequential Total Energy Package (CASTEP) based on density functional theory (DFT) under generalized gradient approximation (GGA). The effects of partial substitution of Ca atoms for Ba atoms in the Eu2+-doped Ba3Si6O12N2 phosphors were studied. Full geometry relaxation results indicated that both Ca and Eu atoms preferentially occupy the Ba1 sites in the Ba3Si6O12N2 crystal. According to the calculated total and atom resolved partial density of states, the densities of the upper and lower states related to the luminescence properties are mainly offered by Ba and Eu atoms, respectively. The 5d states of Ba atoms provide extra density of states to the upper states, resulting in enhanced luminescence intensity. The substituent Ca atoms dilute the upper states, leading to the degeneration of the luminescence intensity. The calculation results could also be used to explain that Ba atoms are superior than other alkaline atoms in many oxonitridosilicate phosphors.

The novel SiO2@SrSi2O2N2:Eu2+ core–shell structured oxynitride phosphors were synthesized by an interfacial reaction mechanism for the first time. First, SrCO3:Eu3+ layers were deposited on monodispersed and spherical SiO2 templates through the urea homogeneous precipitation methods to fabricate the SiO2@SrCO3:Eu3+ precursor particles; then the precursor particles were coated with H3BO3, which will be transformed to a protective h-BN film to prevent the agglomeration of the SiO2 templates at high temperature; at last, the SiO2@SrSi2O2N2:Eu2+ core–shell structured phosphors were synthesized through a gas reduction and nitridation method at 1350 °C under a NH3 gas flow. A uniform dense shell composed of nano-sized (∼20 nm) SrSi2O2N2:Eu2+ grains tightly adhered to the surface of the SiO2 cores. X-Ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy, field emission scanning electron microscopy (FE-SEM), high resolution transition electron microscopy (HR-TEM) as well as photoluminescence (PL) spectra were used to characterize the samples. The results indicate that the obtained submicron SiO2@SrSi2O2N2:Eu2+ phosphors consist of the outer h-BN film, the middle SrSi2O2N2:Eu2+ shell, and amorphous SiO2 cores and exhibit narrow particle size distribution, perfectly spherical morphology and non-aggregation. Under the excitation of UV and blue light, the phosphors show strong green emission due to the 4f65d–4f7 transition of Eu2+. This study opens new possibilities to facilely synthesize highly stable spherical (oxo)nitridosilicate phosphors with monodispersity and improved luminescence properties for display and lighting devices.

Oxynitride phosphor powders comprising of CaSi2O2N2 doped with Tb3+ were successfully synthesized using a high-temperature solid-state reaction method. The experimentally determined photoluminescence (PL) properties of the produced phosphors meet the requirements of 2D/3D plasma display panels (PDPs). In particular, under the excitation of vacuum ultraviolet (VUV) synchrotron radiation and ultraviolet (UV) irradiation, emission peaks corresponding to the 5D3→7FJ (J=6, 5, 4, 3) and 5D4→7FJ (J=6, 5, 4, 3) transitions of Tb3+ ions were recorded. Monitoring the 5D4→7F5 emission of Tb3+ at 545 nm, the excitation bands were assigned to the host-related absorption as well as the 4f–5d (fd) and the 4f–4f (ff) transitions of Tb3+. The produced phosphors can be efficiently excited at 147 nm, and have an adequately short decay time (τ1/10=1.14 ms).Highlights► Tb3+-doped CaSi2O2N2 was proved to be a candidate for plasma display panels (PDPs). ► PL and PLE spectra from VUV to visible range of the phosphor were analyzed. ► The phosphor has an adequately short decay time that is necessary for 3D displays.

Eu2+–Mg2+ co-doped alon phosphors were successfully prepared by carbothermal reaction at 1600 °C for 2 h and their structure and photoluminescence properties were studied. The lattice parameter increased with increasing Eu concentration, indicating the incorporation of Eu into alon crystal lattice. The pure alon phase was obtained when Eu concentration is below 0.2%. Compared with solid state reaction process, this method lead to less amounts of secondary phase, larger amounts of Eu2+ against Eu3+, smaller particle size, narrower particle size distribution and stronger luminescence intensity. The absolute emission intensity of obtained phosphor reached 82% relative to that of famous BAM: Eu2+ phosphor. The emission could be tuned widely from blue to green by varying carbon content.Highlights► We obtained AlON: Eu2+, Mg2+ phosphors by carbothermal reaction for the first time. ► Carbothermal reaction leads to less impurity and uniform particle size distribution. ► Phosphors reached 82% relative to that of famous BAM: Eu2+ phosphor. ► Luminescence color of the phosphors could be tuned by varying carbon content.

Novel Eu2+-doped Ca2AlSi3O2N5 phosphors with a general formula of EuxCa2−xAlSi3O2N5 were successfully prepared via a solid-state reaction method under a nitrogen atmosphere. The produced phosphors were effectively excited by UV–vis light in the wavelength range between 250 and 400 nm, and featured an intense green emission band which peaked at about 500 nm. The emission spectra featured a red-shift over increasing Eu2+ content and the temperature of heat treatment. The maximum intensity of emission was obtained for x = 0.014 and heat treatment at 1450 °C. The photoluminescence properties of the produced Ca2AlSi3O2N5:Eu2+ phosphors qualify them for consideration in potential use as green phosphors in UVLED-based white LED.Highlights► We successfully produced a novel Ca2AlSi3O2N5:Eu2+ phosphors. They have a single intense broad green band centered at c.a. 500 nm and the excitation spectra match well with the emission of UV LED chips (350–410 nm), these qualify them for consideration in potential use as green phosphors in UVLED-based white LED. ► The phosphors can be prepared in lower temperature than the other sialon-based materials, although they have excellent optical properties. ► We studied impact factors on the photoluminescence behavior of the produced phosphors, and found we could tune the intensity and the emission spectra with these characteristic.

The Eu2+-doped Ba3Si6O12N2 green phosphor (EuxBa3−xSi6O12N2) was synthesized by a conventional solid state reaction method. It could be efficiently excited by UV-blue light (250–470 nm) and shows a single intense broadband emission (480–580 nm). The phosphor has a concentration quenching effect at x=0.20 and a systematic red-shift in emission wavelength with increasing Eu2+ concentration. High quantum efficiency and suitable excitation range make it match well with the emission of near-UV LEDs or blue LEDs. First-principles calculations indicate that Ba3Si6O12N2:Eu2+ phosphor exhibits a direct band gap, and low band energy dispersion, leading to a high luminescence intensity. The origin of the experimental absorption peaks is clearly identified based on the analysis of the density of states (DOS) and absorption spectra. The photoluminescence properties are related to the transition between 4f levels of Eu and 5d levels of both Eu and Ba atoms. The 5d energy level of Ba plays an important role in the photoluminescence of Ba3Si6O12N2:Eu2+ phosphor. The high quantum efficiency and long-wavelength excitation are mainly attributed to the existence of Ba atoms. Our results give a new explanation of photoluminescence properties and could direct future designation of novel phosphors for white light LED.Research highlights► This manuscript reports an efficient green Ba3Si6O12N2:Eu2+ phosphor with high quantum efficiency and long-wavelength excitation, which could not be explained by the conventional crystal-field theory. ► Based on the theoretical simulation of its electric structure, it is pointed out for the first time that the Ba in the host lattice gives the main contributions to these excellent luminescent properties. ► These results have implications in the future designation of novel phosphors for white light LED. ► So we strongly believe that this manuscript will be interesting to general readers majoring in novel optical material and luminescence.

Lanthanide-doped CaSi2O2N2 phosphors were synthesized by solid-state reaction. Their photoluminescence (PL) properties were investigated and analyzed systematically. Energy transitions attributed to electron transfers from 4f to 4f (ff), from 4f to 5d (fd), from 5d to 4f (df) and charge transfer (CT) transition were obtained and classified. Finally, an energy-level diagram of lanthanide-ions in CaSi2O2N2 was proposed. The diagram matches perfectly with the experimental results and explains the luminescence properties of lanthanide-doped CaSi2O2N2 phosphors. The electron-vibrational interaction in 4f–5d optical transitions of CaSi2O2N2:Eu2+ was also studied.Highlights► The PL properties of lanthanide-doped CaSi2O2N2 phosphors were systematically studied. ► CaSi2O2N2:Yb2+(Sm3+) can absorb light from UV to blue and may be used in LED light source. ► An energy-level diagram of lanthanide-ion in CaSi2O2N2 was proposed.

Cerium-doped Lu4Si2O7N2 green phosphors were synthesized by a high-temperature solid-state reaction method under nitrogen atmosphere. Compared with Ce-doped Y4Si2O7N2 phosphors, Ce-doped Lu4Si2O7N2 phosphors showed longer wavelengths of both excitation and emission, lower Stokes shift, and much stronger emission intensity. Based on the first-principles calculations of the two phosphors, the strong emission intensity originates from the large density of states. At last, the effects of Ce3+ concentration on photoluminescence were also examined.

Eu2+–Mg2+ co-doped AlON phosphors were prepared by a solid-state reaction route. Their structure and photoluminescence properties were studied. The substitution of Al by Mg favored the formation of pure spinel-type AlON phase and the incorporation of Eu into AlON crystal lattice. Second phase appeared in Eu containing powders. Under ultraviolet excitation at 310 nm, 3% Eu2+–10% Mg2+ co-doped phosphors exhibited a strong broad emission band in the wavelength range of 430–620 nm with a maximum at about 490 nm assigned to the typical 4f65d1–4f7 transition of the Eu2+ ion. Red shift of the emission peak is observed as the increase of Eu2+ concentration due to interaction between Eu2+ ions.

Mn2+–Ce3+ co-doped MgYSi2O5N phosphors were prepared by a solid-state reaction method. Their photoluminescence properties were studied in terms of absorption, excitation, and emission spectra. They could be effectively excited by ultraviolet light and showed intense blue and red emissions, making them attractive candidate phosphors for white light LED application. The luminescence of Ce3+ significantly increased with the incorporation of Mn2+ and an efficient energy transfer from Ce3+ to Mn2+ ions occurred. The blue band emission was attributed to the 5d1–4f1 transition of Ce3+ ions, and the double red band emission was attributed to the single Mn2+ ion and Mn2+ pairs or clusters. The effects of Ce3+ and Mn2+ concentrations on luminance have also been studied.

Eu2+–Mg2+ co-doped alon phosphors were successfully prepared by carbothermal reaction at 1600 °C for 2 h and their structure and photoluminescence properties were studied. The lattice parameter increased with increasing Eu concentration, indicating the incorporation of Eu into alon crystal lattice. The pure alon phase was obtained when Eu concentration is below 0.2%. Compared with solid state reaction process, this method lead to less amounts of secondary phase, larger amounts of Eu2+ against Eu3+, smaller particle size, narrower particle size distribution and stronger luminescence intensity. The absolute emission intensity of obtained phosphor reached 82% relative to that of famous BAM: Eu2+ phosphor. The emission could be tuned widely from blue to green by varying carbon content.Highlights► We obtained AlON: Eu2+, Mg2+ phosphors by carbothermal reaction for the first time. ► Carbothermal reaction leads to less impurity and uniform particle size distribution. ► Phosphors reached 82% relative to that of famous BAM: Eu2+ phosphor. ► Luminescence color of the phosphors could be tuned by varying carbon content.

The novel SiO2@SrSi2O2N2:Eu2+ core–shell structured oxynitride phosphors were synthesized by an interfacial reaction mechanism for the first time. First, SrCO3:Eu3+ layers were deposited on monodispersed and spherical SiO2 templates through the urea homogeneous precipitation methods to fabricate the SiO2@SrCO3:Eu3+ precursor particles; then the precursor particles were coated with H3BO3, which will be transformed to a protective h-BN film to prevent the agglomeration of the SiO2 templates at high temperature; at last, the SiO2@SrSi2O2N2:Eu2+ core–shell structured phosphors were synthesized through a gas reduction and nitridation method at 1350 °C under a NH3 gas flow. A uniform dense shell composed of nano-sized (∼20 nm) SrSi2O2N2:Eu2+ grains tightly adhered to the surface of the SiO2 cores. X-Ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy, field emission scanning electron microscopy (FE-SEM), high resolution transition electron microscopy (HR-TEM) as well as photoluminescence (PL) spectra were used to characterize the samples. The results indicate that the obtained submicron SiO2@SrSi2O2N2:Eu2+ phosphors consist of the outer h-BN film, the middle SrSi2O2N2:Eu2+ shell, and amorphous SiO2 cores and exhibit narrow particle size distribution, perfectly spherical morphology and non-aggregation. Under the excitation of UV and blue light, the phosphors show strong green emission due to the 4f65d–4f7 transition of Eu2+. This study opens new possibilities to facilely synthesize highly stable spherical (oxo)nitridosilicate phosphors with monodispersity and improved luminescence properties for display and lighting devices.

Single-crystalline Cd3P2 nanowires (NWs) have been synthesized via a solution–liquid–solid (SLS) mechanism. The lengths of the resulting nanowires can be effectively tuned in the range of 180 nm and 5 μm, and the photodetectors made of the Cd3P2 nanowires exhibited a pronounced photoresponse with high stability and reproducibility.

Nitrogen-doped γ-Ca2SiO4:Ce3+ phosphors were successfully produced by a solid state reaction method provided that the Ca/Si molar ratio was ≥2.05 and N-doping was simultaneously ≥0.75%. The factors that affect the β → γ phase transformation were also thoroughly investigated. Experimental results were obtained by XRD, FTIR, NMR, SEM, and TEM techniques, along with EDS and SAED analyses. First-principles theoretical calculations were also done. The results showed that the phosphors produced have high photoluminescence and thermal quenching properties, attributed to the covalent nature of the Si–N bond, and the optimum amount of nitrogen incorporation is 0.75%, whereas further increases in nitrogen content degrade the above properties, probably due to the increase in the formation of oxygen vacancies. It was also shown that γ-Ca2SiO4:Ce3+ is thermodynamically more stable than β-Ca2SiO4:Ce3+ after nitrogen doping. A dramatic shift in the emission from yellow to light-blue was recorded when the phosphors were heated to 800 °C. This was attributed to the migration of Ce3+ from Ca(1) to Ca(2) sites in the γ-phase, which is confirmed by 4f → 5d transition energy calculations.

Sr2SiO4:Eu2+ phosphors were synthesized by a conventional solid state reaction method. After a low amount of nitrogen (∼1 mol% of oxygen) was incorporated to modify the local coordination environment of Eu2+, the phosphor showed a single intense broad band emission centered at 625 nm under blue light (453 nm) excitation, and three emission bands (480, 555 and 625 nm) under ultraviolet irradiation. The incorporation of nitrogen was confirmed by X-ray photoelectron spectroscopy (XPS), Fourier-transform infrared spectroscopy (FT-IR) and absorption spectroscopy. 480 and 555 nm emissions originated from Eu2+ ions occupying the Sr(I) sites and Sr(II) sites in the Sr2SiO4 crystal, respectively, while 625 nm emission originated from the nitrogen coordinated Eu2+ ions. The local coordination structure around Eu2+ ions in the red phosphors was analyzed with the aid of density functional theory based first principles calculations. The analysis showed that nitrogen should preferentially substitute the O5′ sites around Eu2+ in Sr(II) sites, which agreed fairly well with the experimental results from the X-ray absorption fine structure (XAFS) and the electron paramagnetic resonance (EPR) spectra. The electronic structure analysis confirmed the lowered center of gravity of Eu 5d energy states and the broadened Eu 4f energy states, which are due to the tightened coordination environment and the hybridization of the 4f states of Eu and 2p states of nitrogen–oxygen, leading to a red emission. The novel nitrogen modified Sr2SiO4:Eu2+ could serve as a full color phosphor for near-UV LEDs or a red-emitting phosphor for blue LEDs.