A white long-lasting phosphor Y_2O_2S:Tb^(3+), Sm^(3+): an improvement of Y_2O_2S:Tb^(3+)

As an improvement of reported Y2O2S：Tb^3＋, a white-light long-lasting phosphor： Y2O2S：Tb^3＋, Sm^3＋ was prepared by the solid-state reaction. The photo-luminescence spectra showed that the position and shape of Tb^3＋ and Sm^3＋ emissions under UV excitation were similar in this host, which ensured a stable white emission color （daylight standard of IEC） under different excitations. The decay curves of co-doped samples indicated that the decay times of emissions of the two ions were close. The thermo-luminescence measurement suggested that the traps created by the doped Sm^3＋ ions were helpful to postpone the white afterglow of co-doped samples. Therefore, the function of co-doped Sm^3＋ ions was confirmed as improving the white emission colors of samples and acting as new trap centers.

A Novel White Light Emitting Long-lasting Phosphor

A novel white light emitting long-lasting phosphor Cd1-xDyxSiO3 is reported in this letter. The Dy3+ doped CdSiO3 phosphor emits white light. The phosphorescence can be seen with the naked eye in the dark clearly even after the 254 nm UV irradiation have been removed for about 30 min. In the emission spectrum of 5% Dy3+ doped CdSiO3 phosphor, there are two emission peaks of Dy3+, 580 nm (4F9/26H13/2) and 486 nm (4F9/26H15/2), as well as a broad band emission located at about 410 nm. All the three emissions form a white light with CIE chromaticity coordinates x=0.3874, y=0.3760 and the color temperature is 4000 K under 254 nm excitation. It indicated that this phosphor is a promising new luminescent material for practice application.

Photo-luminescence properties and thermo-luminescence curve analysis of a new white long-lasting phosphor: Ca_2MgSi_2O_7:Dy^(3+)

A white long-lasting phosphor Ca2MgSi2O7:Dy3+ was prepared by the solid-state reaction. A strong band peaked at 260 nm was shown in the excitation spectrum of 578 nm emission, which might be attributed to the oxygen deficiency of the host. After irradiated with 254 nm for 4 min, the white afterglow of the sample could be seen for 3 h. Moreover, the depths and frequency factors of trap centers were calculated from the thermo-luminescence curve of the sample, which indicated that the trap centers corresponding to the 414 K band were more helpful to the long-lasting phosphorescence.

Characterization of Y_2O_2S∶Eu ^(3+), Mg^(2+), Ti^(4+) Long-Lasting Phosphor Synthesized by Flux Method

Long-lasting phosphor Y2O2S ： Eu^3＋ , Mg^2＋ , Ti^4＋ was synthesized by a flux method and their luminescence properties were investigated. The result indicates that the unit cell parameter c is linearly increased with the increase of Eu2O3 content in Y2O2S： Eu^3＋ （0.01 ≤ x ≤0.10）. On the other hand, the change of unit cell parameter a is not linear dependence. In the Y2O2S： Eu^3 ＋ crystal structure, Eu^3＋ ions only replaced Y^3 ＋ ions＇ places in which it posited center position of c axis. With the increase of Eu2O3 content, the position of the strongest emission peak changed from 540 nm （5D1→^ 7F2 transition） to 626 nm （^5Do→^7TF2 transition）, and the maximum intensity was obtained when x = 0.09 in Y2O2S： Eu^3＋ （0.01 ≤x ≤0.10）. This is due to the environment of trivalent europium in the crystal structure of Y2O2S. Doping with Mg^2＋ or Ti^4＋. ions alone cannot get the good long-lasting afterglow effect, whereas co-doping with Mg^2 ＋ and Ti^4 ＋ ions and excited with 365 nm ultraviolet light, a strong thermoluminesence peak appeared, red and orange long-lasting phosphorescence （LLP） was also observed and the phosphorescence lasted nearly 3 h in the light perception of the dark-adapted human eye （0.32 mcd·m^-2）. Thus the LLP mechanism was analyzed.

Preparation of Long-Lasting Phosphorescence (LLP) Glass-Ceramic Materials

Three kinds of glass-ceramics, i.e., Mn 2+ doped zinc borosilicate, Eu 2+, Dy 3+ co-doped strontium aluminoborate and Eu 2+, Nd 3+ co-doped calcium aluminoborate were prepared, whose phosphorescence emission band peaks at 525, 516 and 464 nm, respectively. In preparation of these glass-ceramics the base glasses were gained by heating the mixed starting materials at high temperature to get the transparent glasses; then those glasses were heat-treated and turned to opaque glass-ceramics. X-ray diffraction (XRD) shows that the crystallites are ZnSiO 4, SrAl 2O 4 and α-CaAl 2B 2O 7, respectively. It is a useful way to get new LLP materials by the method reported in this work that may be considered as “from glass to crystal”.

Soft chemical synthesis and luminescence properties of red long-lasting phosphors Y_2O_2S:Sm^(3+)

Sm3＋-activated Y2028 red phosphors were prepared by the combustion method and microemulsion method at the first time. X-ray characterization and electron diffraction show that, Y202S：Sm3＋, Ti4＋, Mg2＋ samples prepared by these two methods are pure hexagonal crystals in structure with a trivial change due to dopants. Scanning electron microscopy （SEM） results show that the product presents an almond-like sheet in uniform size. Under the excitation of 269 nm ultraviolet light, Y202S：Sm3＋ samples fabricated by these two methods exhibit three main groups of red emission lines located at 564, 604, and 656 nm, respectively, which are attributed to the transitions of 4G5/2 →6H5/2, 4G~/2 →6H7/2, 4G5/2 →6H9/2, respectively. The samples prepared by microemulsion are seven times higher in fluorescent emission intensity and half time longer in afterglow time than that prepared by combustion.

Synthesis and luminescence properties of Eu^(3+),Sm^(3+) doped(Y_xGd_(1-x))_2O_3:Si^(4+),Mg^(2+) long-lasting phosphor

A novel red long-lasting phosphor, （YxGd1-x）2O3：Eu3＋, Sm3＋, Si4＋, Mg2＋, was synthesized by the co-precipitation method using oxalate precipitation as the precursor. X-ray diffraction （XRD）, scanning electronic microscopy （SEM）, integrated thermal analyzer （TG）, and photoluminescence spectra （PL） as well as the ST-900PM weak light photometer were used to study the synthesis conditions, morphology, luminescence properties, and the decay time of the phosphor. The XRD results show that the products synthesized at 1400~C for 4 h have good crystallization without any detectable impurity phases. Based on the PL spectra, the optimal conditions are as the following. The molar ratios of Y3＋ to Gd3＋ and Eu3＋ to Sm3＋ are 2：8 and 3：1, respectively, and the contents of Mg2＋ and SiO2 are 5mol% and 3mol%, respectively. The decay time monitored by the ST-900PM weak light photometer is 7200 s, increasing 44% and 100%, respectively, compared with the Eu3＋ and Sm3＋ single-doped phosphors. The results indicate that the energy transfer is from Sm3＋ to Eu3＋ ion, and Sm3＋ is a good sensitizer to Eu3＋.

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.

Long-lasting phosphorescence study on Y_3Al_5O_(12) doped with different concentrations of Ce^(3+)

Long-lasting phosphorescence （LLP） was observed in Ce-doped Y3Al5O12 phosphors synthesized in reducing atmosphere. The characteristic emission of the 2D–2F5/2 and 2D–2F7/2 transition of Ce3＋ in photoluminescence （PL） and LLP spectra was studied. It was interesting that the ratio between the peak areas of 2D–2F5/2 and 2D–2F 7/2 transitions in the PL spectrum was different from the ratio of that in LLP emission spectrum. And the ratios had different change regularities with increased Ce3＋ concentration. The possible reason was attributed to the defect in the YAG host,which was affected by increasing the Ce3＋ concentration. There were indications that the defect in the Ce3＋-doped YAG samples was strongly associated with oxygen vacancy. And the defect levels were studied through thermoluminescence （TL） experiment. The results showed that the trap depth was between 0.6 and 0.65 eV,and the kinetic order of the LLP was 2.

Luminescent properties of blue long-lasting phosphorescence phosphors Sr_6Al_(18)Si_2O_(37):Eu^(2+),RE^(3+)

A series of novel blue long-lasting phosphorescence phosphors Sr6A118Si2037：Eu^2＋,RE^3＋ （RE3＋=Ho^3＋, Gd^3＋, Dy^3＋ and Pr^3＋） were prepared by the conventional high-temperature solid-state reaction in a reductive atmosphere. Their properties were systemati- cally investigated utilizing X-ray diffraction （XRD）, photoluminescence, phosphorescence and thermoluminescence （TL） spectra. The phosphors emitted blue light that was related to the emission of E~＋ due to 5d-4f transition. Bright blue long-lasting phosphorescence （LLP） could be observed after the excitation source was switched off. For the optimized sample, the blue long-lasting phosphores- cence could last for nearly 4 h in the light perception of the dark-adapted human eye （0.32 mcd/m2）. The effects of RE3＋ ions on phosphorescence properties of the phosphors were studied, and the results showed that the co-doping of RE^3＋ ions greatly enhanced the intensity of the peak around 315 K which was related to the long lasting phosphorescence of the phosphors at room temperature and consequently improved the performance of the blue phosphorescence such as intensity and persistent time.

Phosphorescence properties and energy transfer of red long-lasting phosphorescent(LLP) material β-Zn_3(PO_4)_2:Mn^(2+),Pr^(3+)

The red long-lasting phosphorescent （LLP） of β-Zn3（POa）2：Mn2＋,pr3＋ material was prepared through combustion and conventional solid-state sintering methods. The influence of Pr3＋ ions on luminescence and LLP of Mn2＋ in 13-Zn3（POa）2：Mn2＋,pr3＋ phosphor was systematically investigated. The phosphor presented a strong photoluminescence peak at 620 nm attributed to the 4T1g→ 6A1 g transition of Mn2＋ ions in octahedral coordination. Red LLP was observed in β-Zn3（PO4）2：Mn2＋,Pr3＋ phosphors with persistence time for more than 2 h. It was found that the long persistent phosphorescent performance of Mn2＋ such as brightness and duration was improved by the energy transfer from Pr3＋ to Mn2＋ when Pr3＋ ions as sensitizers were doped into matrix. The fact that the TL peak at low temperature was largely enhanced in Mn2＋, Pr3＋ codoped ^-Zn3（PO4）2 phosphor showed the significant increase of defect concentration with suitable depth. There existed two factors working together to be responsible for the enhancement of LLP performance in β-Zn3（PO4）2：Mn2＋,Pr3＋.

Luminescence properties of a new yellow long-lasting phosphorescence phosphor NaAlSiO_4:Eu^(2+),Ho^(3+)

A new aluminosilicate long-lasting phosphor with composition of NaA1SiO4：Eu2＋,Ho3＋ was synthesized and investigated. Under UV light excitation, the phosphor emitted yellow light corresponding to the characteristic emission of Eu2＋ due to 5d-4f transi- tion. Bright yellow phosphorescence sustaining for more than 30 rain was observed after ceasing the excitation. The phosphorescence intensity decay obeyed a fl decay law, indicating a tunneling electron-hole recombination process in the phosphor. Four peaks ap- peared in the thermoluminescence curve and the ones at 322 and 370 K were thought to account for the long lasting phosphorescence at room temperature. The Ho3＋ ion incorporated into the phosphor did not give any light but dramatically increased the intensities of both photoluminescence and phosphorescence via promoting defect levels in the phosphor.

Long-Lasting Properties of Rare Earth-Doped Y_2O_2S Phosphors

The aim of this presentation is to report a new result of afterglow materials. The Y 2O 2S∶Ln 3+ (Ln=Sm, Tm) phosphors show bright reddish orange and orange-yellow colors when excited by UV or visible light. The main spectroscopic characterizations of Sm 3+ and Tm 3+ in yttrium oxysulfide and their long-lasting phosphorescence were measured and discussed in this presentation. Their long-lasting phosphorescence can be seen by the naked eyes clearly for about one hour in the dark room after the irradiation light sources were removed. XRD and photoluminescence (PL) spectra as well as the luminance decay were used to characterize these long-lasting phosphorescence phosphors. The results of XRD indicate that the products synthesized through the flux fusion method under 1050 ℃ for 6 h have a good crystallization without any detectable amount of impurity phase. Both the PL spectra and luminance decay results reveal that these phosphors have efficient luminescent and good long-lasting properties. We believe that the experimental data gathered in our present work will be useful in finding some new long-lasting phosphors with different colors.

Properties of Self-recoverable Mechanoluminescence Phosphor Ca_(5)Ga_(6)O_(14)∶Eu^(3+) and Its Information Encryption Application

A novel self-recoverable mechanoluminescent phosphor Ca_(5)Ga_(6)O_(14)∶Eu^(3+) was developed by the high-tem-perature solid-state reaction method,and its luminescence properties were investigated.Ca_(5)Ga_(6)O_(14)∶Eu^(3+)can produce red mechanoluminescence,and importantly,it shows good repeatability.The mechanoluminescence of Ca_(5)Ga_(6)O_(14)∶Eu^(3+) results from the piezoelectric field generated inside the material under stress,rather than the charge carriers stored in the traps,which can be confirmed by the multiple cycles of mechanoluminescence tests and heat treatment tests.The mechanoluminescence color can be turned from red to green by co-doping varied concentrations of Tb^(3+),which may be meaningful for encrypted letter writing.The encryption scheme for secure communication was devised by harnessing mechanoluminescence patterns in diverse shapes and ASCII codes,which shows good encryption performance.The results suggest that the mechanoluminescence phosphor Ca_(5)Ga_(6)O_(14)∶Eu^(3+),Tb^(3+)may be applied to the optical information encryption.

Structural and Luminescent Properties of Mg_(0.25-x)Al_(2.57)O_(3.79)N_(0.21):xMn^(2+)Green-Emitting Transparent Ceramic Phosphor

A series of spinel-type Mg_(0.25-x)Al_(2.57)O_(3.79)N_(0.21):xMn^(2+)(MgAlON:xMn^(2+))phosphors were synthesized by the solid-state reaction route.The transparent ceramic phosphors were fabricated by pressureless sintering followed by hot-isostatic pressing(HIP).The crystal structure,luminescence and mechanical properties of the samples were systematically investigated.The transparent ceramic phosphors with tetrahedrally coordinated Mn^(2+)show strong green emission centered around 515 nm under blue light excitation.As the Mn^(2+)concentration increases,the crystal lattice expands slightly,resulting in a variation of crystal field and a slight red-shift of green emission peak.Six weak absorption peaks in the transmittance spectra originate from the spin-forbidden ^(4)T_(1)(^(4)G)→^(6)A_(1) transition of Mn^(2+).The decay time was found to decrease from 5.66 to 5.16 ms with the Mn^(2+)concentration.The present study contributes to the systematic understanding of crystal structure and properties of MgAlON:xMn^(2+)green-emitting transparent ceramic phosphor which has a potential application in high-power light-emitting diodes.

Pillar effect induced by ultrahigh phosphorous/nitrogen doping enables graphene/MXene film with excellent cycling stability for alkali metal ion storage

Graphene's large theoretical surface area and high conductivity make it an attractive anode material for potassium-ion batteries(PIBs).However,its practical application is hindered by small interlayer distance and long ion transfer distance.Herein,this paper aims to address the issue by introducing MXene through a simple and scalable method for assembling graphene and realizing ultrahigh P doping content.The findings reveal that MXene and P-C bonds have a "pillar effect" on the structure of graphene,and the P-C bond plays a primary role.In addition,N/P co-doping introduces abundant defects,providing more active sites for K^(+) storage and facilitating K^(+) adsorption.As expected,the developed ultrahigh phosphorous/nitrogen co-doped flexible reduced graphene oxide/MXene(NPrGM) electrode exhibits remarkable reversible discharge capacity(554 mA hg^(-1) at 0.05 A g^(-1)),impressive rate capability(178 mA h g^(-1) at 2 A g^(-1)),and robust cyclic stability(0.0005% decay per cycle after 10,000 cycles at 2 A g^(-1)).Furthermore,the assembled activated carbon‖NPrGM potassium-ion hybrid capacitor(PIHC) can deliver an impressive energy density of 131 W h kg^(-1) and stable cycling performance with 98.1% capacitance retention after5000 cycles at 1 A g^(-1).Such a new strategy will effectively promote the practical application of graphene materials in PIBs/PIHCs and open new avenues for the scalable development of flexible films based on two-dimensional materials for potential applications in energy storage,thermal interface,and electromagnetic shielding.

Achieving Narrowed Bandgaps and Blue-Light Excitability in Zero-Dimensional Hybrid Metal Halide Phosphors via Introducing Cation-Cation Bonding

Zero-dimensional(0D)hybrid metal halides,which consist of organic cations and isolated inorganic metal halide anions,have emerged as phosphors with efficient broadband emissions.However,these materials generally have too wide bandgaps and thus cannot be excited by blue light,which hinders their applications for efficient white light-emitting diodes(WLEDs).The key to achieving a blue-light-excitable 0D hybrid metal halide phosphor is to reduce the fundamental bandgap by rational chemical design.In this work,we report two designed hybrid copper(I)iodides,(Ph_(3)MeP)_(2)Cu_(4)I_(6)and(Cy_(3)MeP)_(2)Cu_(4)I_(6),as blue-light-excitable yellow phosphors with ultrabroadband emission.In these compounds,the[Cu_(4)I_(6)]^(2-)anion forms an I6 octahedron centered on a cationic Cu_(4)tetrahedron.The strong cation-cation bonding within the unique cationic Cu_(4)tetrahedra enables significantly lowered conduction band minimums and thus narrowed bandgaps,as compared to other reported hybrid copper(I)iodides.The ultrabroadband emission is attributed to the coexistence of free and self-trapped excitons.The WLED using the[Cu_(4)I_(6)]^(2-)anion-based single phosphor shows warm white light emission,with a high luminous efficiency of 65 Im W^(-1)and a high color rendering index of 88.This work provides strategies to design narrow-bandgap 0D hybrid metal halides and presents two first examples of blue-light-excitable 0D hybrid metal halide phosphors for efficient WLEDs.

Fabrication of YAG:Ce^(3+) and YAG:Ce^(3+),Sc^(3+) Phosphors by Spark Plasma Sintering Technique

In this study,a single-doped phosphors yttrium aluminum garnet(Y_(3)Al_(5)O_(12),YAG):Ce^(3+),single-doped YAG:Sc^(3+),and double-doped phosphors YAG:Ce^(3+),Sc^(3+) were prepared by spark plasma sintering(SPS)(lower than 1 200℃).The characteristics of synthesized phosphors were determined using scanning electron microscopy(SEM),X-ray diffraction(XRD),and fluorescence spectroscopy.During SPS,the lattice structure of YAG was maintained by the added Ce^(3+) and Sc^(3+).The emission wavelength of YAG:Ce^(3+) prepared from SPS(425-700 nm) was wider compared to that of YAG:Ce^(3+) prepared from high-temperature solid-state reaction(HSSR)(500-700 nm).The incorporation of low-dose Sc^(3+) in YAG:Ce^(3+) moved the emission peak towards the short wavelength.

Durable hierarchical phosphorus‐doped biphase MoS_(2)electrocatalysts with enhanced H^(*)adsorption

Phase engineering is an efficient strategy for enhancing the kinetics of electrocatalytic reactions.Herein,phase engineering was employed to prepare high‐performance phosphorous‐doped biphase(1T/2H)MoS_(2)(P‐BMS)nanoflakes for hydrogen evolution reaction(HER).The doping of MoS_(2)with P atoms modifies its electronic structure and optimizes its electrocatalytic reaction kinetics,which significantly enhances its electrical conductivity and structural stability,which are verified by various characterization tools,including X‐ray photoelectron spectroscopy,high‐resolution transmission electron microscopy,X‐ray absorption near‐edge spectroscopy,and extended X‐ray absorption fine structure.Moreover,the hierarchically formed flakes of P‐BMS provide numerous catalytic surface‐active sites,which remarkably enhance its HER activity.The optimized P‐BMS electrocatalysts exhibit low overpotentials(60 and 72 mV at 10 mA cm^(−2))in H_(2)SO_(4)(0.5 M)and KOH(1.0 M),respectively.The mechanism of improving the HER activity of the material was systematically studied using density functional theory calculations and various electrochemical characterization techniques.This study has shown that phase engineering is a promising strategy for enhancing the H*adsorption of metal sulfides.

The KEu(WO_(4))_(2)Red Phosphor Co-doped with Li^(+)and SO_(4)^(2-)for Synergistic Enhancement of High Efficiency and Thermal Stability

A series of tungstate red phosphors K_(1-x)Li_(x)Eu(WO_(4))_(2-y)(SO_(4))_(y)were successfully prepared by sol-gel method,and the effects of the introduction of Li~+and SO_(4)^(2-)on the fluorescence intensity and thermal quenching properties of the prepared K_(1-x)Li_(x)Eu(WO_(4))_(2-y)(SO_(4))_(y)phosphors were investigated.The X-ray diffraction data show that the prepared(Li^(+)and SO_(4)^(2-))-doped KEu(WO_(4))_(2)phosphors have a monoclinic tetragonal structure.In addition,the emission intensities of all the observed emission peaks change significantly with the increase of Li~+doping concentration,especially the intensity of the emission peaks at 615 nm fluctuated significantly and reached the maximum at x=0.3 and y=0.2.The K_(1-x)Li_(x)Eu(WO_(4))_(2-y)(SO_(4))_(y)phosphors are found to have the highest fluorescence intensity at x=0.3 and y=0.2.Moreover,the K_(0.7)Li_(0.3)Eu(WO_(4))_(1.8)(SO_(4))_(0.2)phosphor has better thermal quenching properties and luminescence efficiency,and the experimental results indicates that the fluorescence intensity and thermal burst performance of KEu(WO_(4))_(2)red phosphor could be effectively improved by using low-cost bionic doping of Li^(+)and SO_(4)^(2-).