Synthesis of M1-3xAl2O4:Eu2+x/Dy3+ 2x(M^2+= Sr^2+, Ca^2+ and Ba^2+) phosphors with long-lasting phosphorescence properties via co-precipitation method

The long afterglow fluorescent material of M1-3xAl2O4:Eu2+ x/Dy3+2x(M2+= Sr2+, Ca2+ and Ba2+) phosphors are successfully synthesized by calcining precursor obtained via co-precipitation method at 1300oC for 4 h with reducing atmosphere (20% H2 and 80% N2). The phase evolution, morphology and afterglow fluorescent properties are systematically studied by the various instruments of XRD, FE-SEM, PLE/PL spectroscopy and fluorescence decay analysis. The PL spectra shows that the Sr1-3xAl2O4:Eu2+x/Dy3+ 2x phosphors display vivid green emission at s519 nm (4f65d1!4f7 transition of Eu2+) with monitoring of the maximum excitation wavelength at s334 nm (8S7=2!6IJ transition of Eu2+), among which the optimal concentration of Eu2+ and Dy3+ is 15 at.% and 30 at.%, respectively. The color coordinates and temperature of Sr1-3xAl2O4:Eu2+ x/Dy3+ 2x phosphors are approximately at (s0.27, s0.57) and s6700 K, respectively. On the above basis, the M0:55Al2O4:Eu2+ 0:15/Dy3+ 0:3 (M2+= Ca2+ and Ba2+) phosphors is obtained by the same method. The PL spectra of these phosphors shows the strongest blue emission at s440 nm and cyan emission at s499 nm under s334 nm wavelength excitation, respectively, which are blue shifted comparing to Sr1??3xAl2O4:Eu2+ x/Dy3+ 2x phosphors. The color coordinates and temperatures of M0:55Al2O4:Eu2+ 0:15/Dy3+ 0:3 (M2+= Ca2+ and Ba2+) phosphors are approximately at (s0.18, s0.09), s2000 K and (s0.18, s0.42), s11600 K, respectively. In this work, long afterglow materials of green, blue and cyan aluminates phosphors with excellent properties have been prepared, in order to obtain wide application in the field of night automatic lighting and display.

Red color Sr_(2)NaMg_(2)V_(3)O_(12):Eu^(3+)phosphor with high thermal stability for w-LEDs

Sr_(2)NaMg_(2)V_(3)O_(12):xEu phosphors with uniform particle size/morphology and good dispersion can be synthesized via solid state reaction.Under the optimum excitation wavelength of ~340 nm,the Sr_(2)NaMg_(2)V_(3)O_(12):xEu phosphor displays the broad emission band at ~500 nm(blue-green emission,^(3)T_(1,2)→^(1)A_(1) transition of[VO_(4)]^(3-))and sharp emission peak at~610 nm(red emission,^(5)D_(0)→^(7)F_(2) transition of Eu^(3+)),respectively.With the Eu^(3+)content increasing,the emission intensity of[VO_(4)]^(3-)decreases gradually while the emission intensity of Eu^(3+)increases,which is ascribed to the energy transfer from[VO_(4)]^(3-)to Eu^(3+)ions.The decay time of[VO_(4)]^(3-)(-500 nm)increases gradually with the Eu^(3+)content increasing.The energy transfer efficiency and mechanism of[VO_(4)]^(3-)→Eu^(3+)ions were analyzed,respectively.The emission color of Sr_(2)NaMg_(2)V_(3)O_(12):xEu phosphor was regulated from green to red via altering the Eu^(3+)ions concentration.It is delightful for us that the white color emission can be just achieved when the Eu^(3+)content is 5 at%(x=0.05),and the w-LED can be assembled.By studying the luminescence temperature dependence and activation energy of Sr_(2)NaMg_(2)V_3O_(12):xEu phosphor,it is shown that the phosphor has good thermal stability.The Sr_(2)NaMg_(2)V_3O_(12):xEu powder is expected to be a new type of phosphor widely used in light and display areas.

Phosphor-aluminosilicate CsPbX_(3) perovskite fluorescent glass with low formation temperature for photoluminescence display applications

All-inorganic perovskites are rapidly emerging as novel optoelectronic functional materials owing to their flu-orescence properties.However,the stability of these materials has always been the biggest challenge for their applications in photoelectric devices.Therefore,this study focuses on developing phosphor-aluminosilicate-based CsPbX_(3)(X=Cl,Br,and I)glass with a low reaction temperature by adding CsCO_(3),PbX_(2),and NaX to the raw materials in order to improve the stabilities.The glass network intermediates of SiO_(2) and Al_(2)O_(3) doping in the raw material enhanced the stability of the pure phosphate glass network structure and devitrification while decreas-ing the melting temperature.Full chromatographic CsPbX 3 quantum dots(QDs)encapsulated in phosphate-based glass were found to increase the fluorescence properties and quantum efficiency(>59%).Notably,the high water stability of CsPbX_(3) QDs glasses,with the maintenance of 90% luminous intensity,emerged when soaked in water.In addition,the excellent thermal stability and anti-ion exchange properties of the CsPbX_(3) QDs glasses were re-vealed.Benefiting from the above,multicolor light-emitting diode(LED)devices were assembled with a mixture of phosphors of CsPbX_(3) QDs glasses and commercial red-emission K 2 SiF 6:Mn 4+phosphor spread on an InGaN chip,demonstrating bright light with superior luminous properties.Phosphor-aluminosilicate-based CsPbX_(3) QDs glass with high stability and low formation temperature would provide new methods for applications in lighting and displays.

Synergistic effect of N- and F-codoping on the structure and photocatalytic performance of TiO_2

Three types of TiO2 nanostructures were synthesized via a facile hydrolysis method at195 °C. Effects of the preparation method and doping with N and F on the crystal structure and photocatalytic performance of TiO2 were investigated. The nanomaterials were characterized by X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy, Brunauer–Emmett–Teller porosimetry, ultraviolet–visible diffuse reflectance spectroscopy and fluorescent emission spectra. Their photo-catalytic activity was examined by the photodegradation of methylene blue in aqueous solution under both ultra-violet and visible light irradiation. The results show that nitrogen and fluorine co-doped anatase TiO2 had the characteristics of a smaller crystalline size, broader light absorption spectrum and lower charge recombination than pure TiO2. Most importantly, more efficient photocatalytic activity under both ultra-violet and visible light was observed. The obtained N–F-TiO2 nanomaterial shows considerable potential for water treatment under sunlight irradiation.

Synthesis and luminescent properties of BaGd_2O_4:Eu^(3+) phosphors with highly efficient red-emitting

The BaGd（2-2 x）Eu（2 x）O4（BG, x = 0.01-0.09） phosphors were successfully synthesized via the sol-gel method,and BaY（2-2 y）Eu（2 y）O4（BY, y = 0.005-0.07） phosphors were included for comparison. The pure phase BG phosphors with the ordered CaFe2 O4-type structure are obtained by annealing at 1300℃ for5 h. The phosphors with uniform particle size of 120 nm and good dispersion display typical Eu^3＋emission with the strongest peak at 613 nm（^5 D0→^7 F2 transition of Eu3＋） under optimal excitation band at 262 nm（CTB band）. The presence of Gd^3＋ excitation bands on the PLE spectra monitoring the Eu3＋emission directly proves an evidence of Gd^3＋-Eu^3＋ energy transfer. Owing to the concentration quenching, the optimum content of Eu3＋ addition is 5 at%（x = 0.05）, and the quenching mechanism is determined to be the exchange reaction between Eu3＋. All the BG samples have similar color coordinates and temperature of（0.64 ± 0.02, 0.36 ± 0.01） and 2000 ± 100 K,respectively. The lifetime value of BaGd（1.9）Eu（0.1）O4 for 613 nm is fitted to be 2.19 ± 0.01 ms, and the Eu^3＋ concentration does not change the lifetime significantly. Owing to the Gd^3＋-Eu^3＋ energy transfer, the luminescent intensity of the BaGd（1.9）Eu（0.1）O4 phosphor is better than BY system. The BG system served as a new type of phosphor is expected to be widely used in lighting and display areas.

Nanocomposites of CsPbBr_(3) perovskite quantum dots embedded in Gd_(2)O_(3):Eu^(3+) hollow spheres for LEDs application

Gd_(2)O_(3):Eu^(3+)@CsPbBr_(3) quantum dots(QDs)mesoporous hollow nanocomposites with good luminescent properties and high stability were built.Among which,the hollow Gd_(2)O_(3):Eu^(3+)spheres and CsPbBr_(3) QDs were prepared by urea homogeneous precipitation and hot-injection method,respectively.Finally,the Gd_(2)O_(3):Eu^(3+)@CsPbBr_(3) QDs shell-core compounds were constructed through mechanical stirring.The structure,morphology,stability and luminescent properties were studied by Fourier transform infrared spectroscopy(FT-IR),differential scanning calorimetry/thermogravity(DSC/TG),X-ray diffraction(XRD),field-emission scanning electron microscopy(FE-SEM),transmission electron microscopy(TEM),photoluminescence excitation/photoluminescence(PLE/PL)and life decay tools.Compared to the original CsPbBr_(3) QDs,Gd_(2)O_(3):Eu^(3+)@CsPbBr_(3) QDs display better photostability,thermal stability and current stability.The resulting Gd_(2)O_(3):Eu^(3+)@CsPbBr_(3) QDs composite exhibits good yellow emission.The Gd_(2)O_(3):Eu^(3+)@CsPbBr_(3) QDs mixed silicone resin was directly coated on the blue LED chip,then the w-LED device with the color coordinate of(0.31,0.32)was successfully assembled.The Gd_(2) O_(3):Eu^(3+)@CsPbBr_(3) QDs compounds with excellent luminescent properties and stability are expected to be widely used in lighting and display areas.

The Effects of Bio-inspired Electromagnetic Fields on Normal and Cancer Cells

The electromagnetic field(EMF)is one of many environmental factors,which earth creatures are exposed to.There are many reports on the effects of EMF on living organisms.However,since the mechanism has not yet been fiilly understood,the biological effects of EMF are still controversial.In order to explore the effects of bio-inspired EMF(BIEMF)on normal and cancer cells,various cultured cells have been exposed to BIEMF of different directions,i.e.vertical,parallel and inclined.Significantly reduced ATP production in Hela and A549 cancer cells is found for the parallel and vertical BIEMF.More careful examination on Hela cells has revealed a cell density dependent inhibition on colony formation.The morphological observation of BIEMF-exposed Hela cells has suggested that the retarded cell proli feration is probably caused by cell death via apoptosis.Together these results may afford new insights for cancer prevention and treatment.

Synthesis and luminescent properties of Ba_(3)Y_(3.88)Gd_(0.12)O_(9):Eu^(3+) phosphors with enhanced red emission

In this work,the Gd^(3+)/Eu^(3+) activated Ba_(3)Y_(4)O_(9)(BYO)phosphors were successfully synthesized via coprecipitation method at 1400℃.The precursor composition,crystal structure stability,microscopic morphology,photoluminescence(PL)/photoluminescence excitation(PLE)spectra and fluorescence attenuation analysis of the phosphors are discussed in detail.The chemical composition of the precursor was determined by Fourier transform infrared spectroscopy(FT-IR)and thermogravimetry(TG)analysis;According to field emission-scanning electron microscopy(FE-SEM)analysis,it is found that the particle size of phosphor is uniform and the agglomeration is few.According to PL/PLE spectra analysis,Ba_(3)Y_(3.28)Eu_(0.6)Gd_(0.12)O_(9) phosphors has the strongest excitation band at 260 nm and the strongest emission band at 614 nm,and the fluorescence intensity of Ba_(3)Y_(3.28)Eu_(0.6)Gd_(0.12)O_(9) is higher than that of Ba_(3)Y^(3.4)Eu^(0.6)O_(9).The quenching concentration of Eu^(3+)in Ba_(3)Y_(3.88–4x)Eu_(4x)Gd_(0.12)O_(9) phosphors is x=0.15 and the mechanism of quenching concentration of Eu^(3+)is electric dipole-quadrupole type interactions.The lifetime value of Ba_(3)Y_(3.88–4x)Eu_(4x)Gd_(0.12)O_(9)(x=0.15)phosphors is 0.686 ms and decreases with the increase of Eu^(3+)content.In addition,the CIE chromaticity diagram of Ba_(3)Y_(3.28)Eu_(0.6)Gd_(0.12)O_(9) phosphors is(0.66,0.34).Finally,the lamp beads assembled with Ba_(3)Y_(3.28)Eu_(0.6)Gd_(0.12)O_(9) phosphors have an ideal luminous effect.Therefore,the Ba_(3)Y_(3.88–4x)Eu_(4x)Gd_(0.12)O_(9) phosphors designed in this work may hopefully meet the requirements of various lighting and optical display applications.