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Optical manometry is a highly promising method for measuring pressure. However, its wider application is limited by the lower sensitivity and influenced by environmental factors. Herein, multi‐mode optical pressure sensors based on Eu2+‐doped Li4SrCa(SiO4)2 phosphors suitable for a variety of complex pressure‐measuring environments are designed. The phosphors contain two separate luminescence centers at 443 nm (EuSr) and 584 nm (EuCa), respectively. In the lower pressure range, the emission peak undergoes a massive redshift of 5.19 nm GPa−1 of EuCa, which is 14× better than commercially available ruby sensors. In order to improve the pressure response range and the accuracy of pressure measurement, for the first time, a new approach in the pressure readout method in which single Eu2+ ions doping based on fluorescence intensity ratio (FIR) pressure measurement is realized in designed materials. Meanwhile, the measured full width at half maximum (FWHM) as an indicator of pressure sensor performance also reveals that the sensing performance is d FWHM/d P ≈ 1.23 nm GPa−1 and d FWHM/d P ≈ 0.84 nm GPa−1 for EuSr and EuCa positions, respectively. Additionally, the structural stability of the phosphor is confirmed by in situ Raman spectrum. The above results indicate that the Li4SrCa(SiO4)2:0.04Eu2+ phosphor is a good candidate for multi‐mode optical pressure sensors. [ABSTRACT FROM AUTHOR]

Whitlockite-type structure phosphors have been widely studied due to their adjustable chemical composition and abundant crystal location. Whitlockite-type phosphors can be doped with rare earth elements to achieve the emission of warm white light. White light-emitting diodes (w -LEDs) have become increasingly popular and play a significant role in many applications, such as Biosensing and fluorescent labeling. In this work, The Ca 2.6 K 0.2 La 0.2 (PO 4) 2 (CKLP) whitlockite-type phosphors co-doped with Dy3+ and Sm3+ were entered via a high-temperature solid-phase reaction. Their crystal structure, luminescence characteristics, and temperature sensitivity were explored in detail. Through doping Dy3+ and Sm3+, can obtain white light and warm white light. As the concentration of Sm3+ increased, their lifetime decreased from 0.483 ms to 0.059 ms, confirming interionic energy transfer in the host. The CKLP: 0.06Dy3+, 0.06Sm3+ phosphor prepared by Fluorescence Intensity Ratio (FIR) technology has suitable temperature sensing performance. Its relative sensitivity (Sr) and complete sensitivity (Sa) are high up to 4.48 × 10−3 k−1 and 1.021%K−1 at 298 K. The results show that CKLP: Dy3+ and Sm3+ phosphors used in w -LEDs and display devices will present excellent application potential in new optical thermometry. • The whitlockite-type structure phosphor realized white light emission. Obtained excellent color temperature coordinates, high sensitivity and realized the control of warm white light. • The whitlockite-type structure phosphors are a candidate material for non-contact optical temperature sensing and have potential anti-counterfeiting applications. [ABSTRACT FROM AUTHOR]

Following the rapid growth of lightning technology, the development of red-emitting phosphors is effective for improving color temperature and color rendering index for w-LEDs devices. Herein, a single phased garnet phosphor with cation and polyhedron substitution modification was firstly prepared. For Mg 3 Gd 2 Ge 3 O 12 : Bi3+, Eu3+, the intensity has been remarkably improved by about 16% compared to the one without Bi3+ sensitization. The energy transfer mechanism is identified in this work. Based on cation and polyhedron substitution strategies, novel phosphors with different compositions were obtained and further modified the PL properties. With Lu3+ substitution, the bond lengths between Bi3+ ion and anion ligands are decreased and the site symmetry has been strengthened, which leads to a 21 nm blue shift when Lu3+ totally replaced Gd3+ ions. In addition, Lu3+ and [SiO 4 ] substitution strategies both effectively increased symmetric rigid structure, which leads to a significant improvement in thermal stability, indicating the samples own great potential in optical applications This work provides a new insight to synthesis red-emitting phosphors for warm white-LEDs. [ABSTRACT FROM AUTHOR]

Ca9La(PO4)5(SiO4)F2:Tb3+,Dy3+ (CLPSF:Tb3+,Dy3+) phosphors were successfully prepared using the traditional solid‐state technique. The crystal structure was refined and the luminescence properties have been examined in detail. The band gap and electronic structure of Ca9La(PO4)5(SiO4)F2 were performed by the periodic density functional theory (DFT) calculation. The spectral and fluorescence decay dynamics of CLPSF:Tb3+,Dy3+ show that the energy transfer behavior between Tb3+ and Dy3+ ions is observed. The CLPSF:Tb3+,Dy3+ phosphors can be efficiently excitable at the wavelengths range from 300 to 500 nm. The emission spectrum covers the whole visible part of the spectra with the sharp emission bands in red, green, and blue regions. The correlated color temperature (CCT) and color rendering index (CRI) of white light emission could be improved by the fine‐tuning of the Tb3+ and Dy3+ ions ration in accordance with the energy transfer behavior. Thus, the CLPSF:Tb3+,Dy3+ phosphor could be used as a material for the near‐ultraviolet (n‐UV) and white light‐emitting diodes (w‐LEDs). [ABSTRACT FROM AUTHOR]

A novel orange-red emitting orthosilicate phosphor LiGd 9 (SiO 4) 6 :Mn2+ (LGS:Mn2+) belongs to hexagonal lattice with P 6 3 / m space group was synthesized via solid-state method and the phase composition, crystal structure as well as luminescence properties were examined for potential application in near ultraviolet (n -UV) pumped white light emitting diodes (w -LEDs). The as-prepared LGS:Mn2+ phosphor exhibits three excitation bands peaked at 273, 312 and 410 nm, which corresponds to the transitions of Gd3+ from ground state 8S 7/2 to 6I 7/2 , 6P 7/2 and Mn2+ from ground state 6A 1 (6S) to the individual components of the multiplets [4A 1 (4G), 4E(4G)], respectively. Upon excitation at 312 nm, the phosphors display an intense broad orange-red emission peaked around 594 nm, which ascribed to the typical spin-forbidden transition (4T 1 (4G)-6A 1 (6S)) of the Mn2+ ions. The concentration quenching mechanism and average separation distance in conjunction with fluorescence decay times of Mn2+ ions in LGS:Mn2+ phosphor were discussed. The indispensable parameters for application in n -UV high-powered w -LEDs, such as the thermal quenching of photoluminescence and internal quantum efficiency of LGS:Mn2+ phosphor, have also been investigated in detail. The above results indicate that LGS:Mn2+ could play a key role as an orange-red emission for potential application in n -UV-based w -LEDs. • LiGd 9 (SiO 4) 6 O 2 :Mn2+ luminescent materials were synthesized successfully. • This phosphor have excellent thermal stability and emission efficiency. • High energy transfer efficiency could be obtained between Gd3+ and Mn2+ ions. [ABSTRACT FROM AUTHOR]

Highlights • The ET mechanism has been confirmed by the luminescence spectra and fluorescence decay curves. • The ET interaction mechanism was determined to be dipole–quadrupole interaction. • The emission color of as-prepared phosphor could be adjusted from green to yellow. Abstract The Ca 9 La(PO 4) 5 (SiO 4)F 2 :Tb3+,Sm3+ phosphor with apatite structure has been successfully synthesized by high temperature solid-state reaction, and its luminescence properties as well as energy transfer mechanism has been investigated in detail. The energy transfer (ET) efficiency increases with increasing Sm3+ doping content, that was confirmed by the luminescence spectra and fluorescence decay curves of corresponding ions. The ET interaction mechanism was determined to be dipole–quadrupole interaction. The emission color of Ca 9 La(PO 4) 5 (SiO 4)F 2 :Tb3+,Sm3+ phosphor could be adjusted from green (0.272, 0.489) to yellow (0.363, 0.395) area through controlling the dopant ratio of Tb3+/Sm3+. The above results indicate that the Ca 9 La(PO 4) 5 (SiO 4)F 2 :Tb3+,Sm3+ phosphor has a great potential in white light-emitting diodes application. [ABSTRACT FROM AUTHOR]

Abstract A series of novel luminescence phosphors Ca 9 La(PO 4) 5 (SiO 4)Cl 2 : x Eu2+ (CLPSCl:Eu2+) with apatite structure have been synthesized by a high temperature solid-state reaction. The phased purity of as-prepared phosphors was verified through XRD technique. For further discussion, a series of analysis were performed such as the photoluminescence emission and excitation spectrum and decay lifetime to identify the luminescent properties of CLPSCl:Eu2+ phosphors. The CLPSCl:Eu2+ displays broad excitation spectra ranging from 250 to 450 nm, and intends emission intensity at 461 nm under 345 nm. The optimum Eu2+ concentration of CLPSCl is 8 mol%. The luminescence decay lifetime of the optimum phosphors was measured to be 275 ns. All of the results obtained highly indicate that CLPSCl:Eu2+ is potentially blue-emitting phosphor for application in white LEDs. [ABSTRACT FROM AUTHOR]

Abstract The novel apatite-type phosphor Ca 9 Tb(PO 4) 5 (SiO 4)F 2 :Mn2+ (CTPSF:Mn2+) has been successfully synthesized and it demonstrated a potential for optical thermometry. The energy transfer process between Tb3+ and Mn2+ was of resonant type via a dipole-dipole mechanism based on the Inokuti–Hirayama theoretical model, and the energy transfer (ET) efficiency and ET rate were estimated. In view of the energy transfer behavior, a strategy, involving the use of Tb3+ and Mn2+ dual-emitting centers with different thermal quenching behavior, has been developed to achieve temperature sensitivity and good signal discrimination. The temperature dependence of the fluorescence intensity ratios (FIR) for the dual-emission bands peaking at 548 and 595 nm was studied in the range of 298–573 K under excitation of 377 nm ultraviolet light and the maximum relative sensitivity was approximately 1.92% K−1 at 423 K. It is expected that this preliminary study will provide an important advance in exploring novel ratiometric optical thermometry. Highlights • Novel apatite-type phosphor Ca 9 Tb(PO 4) 5 (SiO 4)F 2 was synthesized. • Energy transfer mechanism is estimated based on Inokuti–Hirayama model. • Non-contact thermometry was developed with a new inorganic material. • The maximum S r of the as-prepared phosphor was as high as 1.92% K−1. • This work provides an insight to design ratiometric optical thermometry. [ABSTRACT FROM AUTHOR]

Whitlockite-type structure phosphors have received extensive attention and research due to their adjustable chemical compositions in isomorphic compounds and providing rich crystal positions for doping activators. Ca 2.6 K 0.2 La 0.2 (PO 4) 2 whitlockite-type phosphors with Dy3+ singly doping and Dy3+, Eu3+ co-doping were prepared via high temperature solid-phase reaction, and the crystallographic characteristics, luminescence properties and temperature sensing performance were investigated in detail. The prepared phosphors are pure phase and both Dy3+ and Eu3+ enter into the matrix and produce blue, yellow and red emissions. The CCT values of the emitted light from Ca 2·6 K 0·2 La 0·2 (PO 4) 2 : Dy3+, Eu3+ phosphors increase with the Eu3+ concentration rises, changing from cold white light to warm white light. The integrated emission intensity of Dy3+ in the phosphor decreases with the change in the doping ratio of Dy3+ and Eu3+, causing by the energy transfer from Dy3+ to Eu3+. The Ca 2·6 K 0·2 La 0·13 (PO 4) 2 :0.06Dy3+, 0.01Eu3+ phosphor shows temperature sensing performance based on FIR technique, with the maximum relative sensitivity calculated to be 0.181% K−1. All the results reveal that the Ca 2·6 K 0·2 La 0·2 (PO 4) 2 : Dy3+, Eu3+ phosphors can be applied to w-LEDs and display devices, and can be used as a new type of optical thermometer. Dy3+/Eu3+ co-doped Ca 2·6 K 0·2 La 0·2 (PO 4) 2 phosphor applied for w-LEDS and temperature sensing. [Display omitted] • Single-phase luminescent materials Dy3+, Eu3+ co-doped Ca 2·6 K 0·2 La 0·2 (PO 4) 2 phosphor with whitlockite structure was synthesized for the first time. • The concentration quenching and energy transfer mechanisms were investigated. • The emission color of Ca 2·6 K 0·2 La 0·2 (PO 4) 2 : Dy3+, Eu3+phosphors changes from natural white light to warm white light with the increase of Eu3+ concentration. • The samples showed temperature sensing performance with maximum S a to be 2.06 × 10−3 K−1 and S r to be 0.181% K−1 under 303 K. [ABSTRACT FROM AUTHOR]

A novel apatite structure phosphor Ca 9 La(PO 4 ) 5 (GeO 4 )F 2 :Dy 3+ (CLPGF:Dy 3+ ) with a hexagonal lattice in the P 6 3 / m space group was synthesized via a facile solid state technique. The crystal and fine local structure as well as their photoluminescence properties were investigated in detail. The CLPGF:Dy 3+ phosphor can absorb in the UV-vis spectral region of 290–475 nm and exhibit two intense emission bands centered at 485 and 580 nm, which ascribes to 4 F 9/2 → 6 H 15/2 and 4 F 9/2 → 6 H 13/2 transitions of Dy 3+ , respectively. The concentration quenching of Dy 3+ emission occurs via the energy transfer among the nearest-neighbor ions and the corresponding quenching mechanism was verified to be the dipole-dipole interaction. The quantum efficiencies of the phosphors were examined to be 72.9% and its luminescence intensity at 150 °C decreases to 93.8% and 98.6% of the initial value at room temperature, which corresponds to 4 F 9/2 to 6 H 15/2 transition and 4 F 9/2 to 6 H 13/2 transition of Dy 3+ ions, respectively. Their interesting photoluminescence properties indicate that the CLPGF:Dy 3+ phosphor is a promising white-emitting candidate for w -LEDs applications. [ABSTRACT FROM AUTHOR]

The simple high-temperature solid-state route was adopted to synthesize a series of related Ba 3 LaK(PO 4 ) 3 F: x Eu 2+ (BLKPF: x Eu 2+ ) blue phosphors. The photoluminescence (PL) and diffuse reflection spectra have been investigated in detail. These phosphors which can be well excited by the 388 nm near ultraviolet light, produce the emitted blue light peaks located at about 460 nm. The critical Eu 2+ concentration quenching mechanism was ascribed to the dipole–dipole interaction, and the optimum concentration was eventually proved to be 0.1 mol. All above results indicate that Ba 3 LaK(PO 4 ) 3 F: x Eu 2+ phosphor can act as an appropriate candidate of the blue phosphor in the future. [ABSTRACT FROM AUTHOR]

A series of Dy3+-doped MGd 9 (SiO 4) 6 O 2 :Dy3+ (M = Li, Na, K) phosphors that generated white emission were prepared using the high temperature solid-state technique. Simultaneously, the phase composition, crystal structure, electronic structure, as well as the luminescence properties of the as-prepared phosphors were investigated in detail. The structural refinement showed that the MGd 9 (SiO 4) 6 O 2 crystallized with the hexagonal apatite-type structure. The unit cell parameters increased gradually and the main peaks of the samples in XRD patterns shifted towards high angles with the substitution of alkali-metal ions (from Li+ to K+). Under the excitation of 350 nm, the as-obtained MGd 9 (SiO 4) 6 O 2 :Dy3+ phosphors gave bright white emission with the major emission peaks centering at 454, 477 and 573 nm. And the R y/b , CIE chromaticity coordinate and the corrected color temperature (CCT) of the phosphors were adjusted from 0.96, (0.3256, 0.3625) and 4602 K to 1.13, (0.3369, 0.3582) and 4201 K attributing to the substitution in the crystal structure. The thermoluminescence study of MGd 8.90 (SiO 4) 6 O 2 :0.10Dy3+ (M = Li, Na, K) showed good stability and the decay lifetimes of the samples were estimated to be about 470 μs. All the results suggested that the luminescence properties could be modified by the substitution of alkali metal ions, and the MGd 9 (SiO 4) 6 O 2 :Dy3+ (M = Li, Na, K) phosphors have potential application as white emission candidate for w -LEDs. • Novel Dy3+ doped apatite structure phosphors were successfully synthesized. • The symmetrical environment could be modified to a certain extent owing to substitution of alkali metal ions. • The DFT calculation was used to check the electronic structure. [ABSTRACT FROM AUTHOR]

An activators lattice migration strategy was customized for developing tunable- luminescence phosphors in Ce doped β -Ca 3 (PO 4) 2 families. By dint of XAFS and DFT calculations, we predicted the local crystal environment of each lattices and migrated Ce3+ from M(3) to another strengthened site with a lower coordination number, shorter bonding bond length, and greater polyhedral distortion, M(5). Relevant parameters were identified for dealing with interference caused by the electronegativity change during structural modification and some applications emerged for display and information security. [Display omitted] • Activators lattice migration strategy was proposed for tunable-emission phosphors. • The specific occupation and 5 sites local crystal environment of Ce were predicted. • Ce3+ was migrated to another site with a strengthened crystal field by modification. • The relative intensity of ε CFS and ε NE determined an abnormal emitting mechanism. • Δ D (C e 3 +) were identified to deal with the interference of electronegativity difference. The luminescent properties of phosphors are determined by the electronic configuration of their activators and the crystal environment in which they are embedded. By manipulating the site-selective occupancy of activators, we can coordinately control the local crystal field and electron cloud distribution to master the movement of emission wavelength and obtain a color-tunable phosphor. The system of β -Ca 3 (PO 4) 2 is an excellent carrier for crystal-site engineering to modify luminescent performance. It has five distinct crystal sites and a strong photoluminescence response. However, due to low doping concentration and structural complexity, the specific occupation of Ce remains unknown. We discussed the specific position of Ce in this study and proposed a novel activators lattice migration strategy for controlling the relative strength of crystal field splitting (CFS) and the nephelauxetic effect (NE) to control luminescence properties. By combining X-ray Absorption Fine Structure (XAFS) with DFT calculation, we predicted the local environment of each crystal lattice and migrated Ce3+ from M(3) to a strengthened crystal field site with a lower coordination number, shorter bonding bond length, and greater polyhedral distortion, M(5) , resulting in phosphors with tunable luminescence emission. Relevant parameters Δ D (C e 3 +) were identified for dealing with interference caused by the electronegativity difference during a structural modification. Some potential applications emerged as a supplement and an intriguing QR-code and response program for epidemic prevention were demonstrated. This structure–activity relationship-based strategy provides new inspiration for designing luminescent materials with tunable emission and a broader range of applications. [ABSTRACT FROM AUTHOR]

An appropriate solid-state route was adopted to synthesize a series of related Ba 3 Sc(PO 4 ) 3 : x Sm 3+ red-orange phosphors. The Rietveld method was used to explore the structure of the phosphor. At present the PL, PLE, diffuse reflection and decay curves have been investigated in detail. These phosphors can be accurately excited by the 406 nm n-UV light and produce the emitted red-orange light whose peaks locate at about 566 nm, 603 nm and 650 nm. The quantum efficiency of Ba 3 Sc 0.95 (PO 4 ) 3 :0.05Sm 3+ was 53.5%. All above results indicate that Ba 3 Sc(PO 4 ) 3 :Sm 3+ phosphor can act as a suitable candidate of the warm components of n -UV w-LEDs. [ABSTRACT FROM AUTHOR]

Ba 3 Sc(PO 4 ) 3 :Eu 2+ ,Tb 3+ (BSP:Eu 2+ ,Tb 3+ ) phosphors were successfully prepared via conventional high-temperature solid-state reaction, their luminescence properties as well as energy transfer mechanism have been investigated in detail. The energy transfer mechanism was proposed to be the dipole–quadrupole mechanism, and the energy transfer efficiency was also estimated. BSP:Eu 2+ ,Tb 3+ phosphors showed a broad emitting band centered at 518 nm and several sharp emission peaks, which were assigned to the 5 d →4 f allowed transitions of Eu 2+ ions and characteristic optical 5 D 4 – 7 F J ( J =6, 5, 4, and 3) transitions of Tb 3+ ions, respectively. The emission color of BSP:Eu 2+ , y Tb 3+ exhibited a controlled luminescence evolution in the green area owing to the Eu 2+ –Tb 3+ energy transfer process. [ABSTRACT FROM AUTHOR]

Tm 3+ /Yb 3+ co-doped BaLa 2 ZnO 5 up-conversion (UC) phosphors were successfully synthesized by high temperature solid-state reaction method. The X-ray diffraction (XRD) results show that synthesized phosphor co-doped with 0.75% Tm/10% Yb has the optimum pure phase of BaLa 2 ZnO 5 among different co-doping concentrations. The structure of BaLa 2 ZnO 5 :0.75% Tm/10% Yb phosphor was refined by the Rietveld method and results show the decreased unit cell parameters and cell volume after doping Tm 3+ /Yb 3+ , indicating that Tm 3+ /Yb 3+ have successfully replaced La 3+ . Under excitation at 980 nm, Tm 3+ /Yb 3+ co-doped BaLa 2 ZnO 5 phosphors present bright blue emission near 478 nm generated by the 1 G 4 → 3 H 6 transition and weak red emissions around 653 nm and 692 nm generated by the 1 G 4 → 3 F 4 and 3 F 3 → 3 H 6 transitions of Tm 3+ , respectively. The UC luminescence properties of BaLa 2 ZnO 5 phosphors co-doped with different Tm 3+ /Yb 3+ concentrations were investigated, and the related UC mechanisms of Tm 3+ /Yb 3+ co-doped BaLa 2 ZnO 5 depending on pump power were studied in detail. [ABSTRACT FROM AUTHOR]

Montmorillonite (Mt) has high cation exchange capacity and thus has been studied extensively for its cation exchange interactions with other cations. However, molecular simulations for the forces governing the cation exchange on Mt surfaces or in the interlayer spaces were limited. In this study, Mt with K+ and Na+ in the interlayer spaces was tested for its cation exchange with Cd2+ in solution and the forces driving the cation exchange reaction were simulated by molecular simulations. The experimental results showed that Na+ in Na + Mt was completely exchanged by Cd2+, while only 50% of K+ in K + Mt was exchanged by Cd2+. A larger d-value was noticed for Na + Mt in comparison to K + Mt, suggesting that the interlayer space is more hydrated with Na+ as the interlayer space cation. Molecular dynamic simulations revealed a larger energy decrease when Cd2+ substitutes K+. However, the nice fit of the K+ into the 12-coordinated interlayer space sites may restrict its hydration and thus reduce its interlayer space cation exchange capability by Cd2+. [ABSTRACT FROM AUTHOR]

Up-conversion phosphors BaLa 2 ZnO 5 co-doped with Ho 3+ /Yb 3+ were synthesized by high temperature solid-state reaction method. The phase composition of the phosphors was characterized by X-ray diffraction (XRD). The structure of BaLa 2 ZnO 5 : 0.75% Ho/15% Yb phosphor was refined by the Rietveld method and results showed the decreased unit cell parameters and cell volume after doping Ho 3+ and Yb 3+ , indicating Ho 3+ and Yb 3+ have successfully replaced La 3+ . Under the excitation of 980 nm diode laser, the strong green and weak red up-conversion emissions centered at 548 nm, 664 nm and 758 nm were observed, which originating from 5 S 2 , 5 F 2 → 5 I 8 , 5 F 4 → 5 I 8 and 5 S 2 , 5 F 2 → 5 I 7 transitions of Ho 3+ ions, respectively. The optimum doping concentrations of Ho 3+ and Yb 3+ were determined to be 0.75% and 15%, and the corresponding Commission International de L'Eclairage (CIE) coordinates are calculated to be x =0.298 and y =0.692. The related UC mechanism of Ho 3+ /Yb 3+ co-doped BaLa 2 ZnO 5 depending on pump power was studied in detail. The results indicate that BaLa 2 ZnO 5 : Ho 3+ /Yb 3+ can be an effective candidate for up-conversion yellowish-green light emitter. [ABSTRACT FROM AUTHOR]

Er 3+ and/or Yb 3+ doped Sr 2 ScF 7 up-conversion (UC) phosphors were synthesized, and the optimum doping concentrations of Yb 3+ and Er 3+ in the Sr 2 ScF 7 host were found to be 20% mol and 7% mol, respectively. Under excitation of 980 nm laser, the UC spectra of the samples is composed of three green emission bands from 510 to 570 nm centered at 525, 543 and 551 nm and two red emission band from 640 to 690 nm with two peaks at 657 and 671 nm, which is attributed to the 2 H 11/2 , 4 S 3/2 → 4 I 15/2 and 4 F 9/2 → 4 I 15/2 transitions of Er 3+ , respectively. The UC emission color of Er 3+ can be tuned by adjusting the intensity ratio of red to green emission through manipulating the population of red and green emitting states. [ABSTRACT FROM AUTHOR]

BaLa2ZnO5:Er3+/Yb3+ has been synthesized via a high temperature solid-state method, and the tunable upconversion luminescence and energy transfer process between Yb3+ and Er3+ in this system have been demonstrated. Upon 980 nm laser excitation, the intense green and red emission around 527, 553, and 664 nm were observed for BaLa2ZnO5:Er3+/Yb3+, which can be assigned to the characteristic energy level transitions of 2H11/2 → 4I15/2, 4S3/2 → 4I15/2, and 4F9/2 → 4I15/2 of Er3+, respectively. The critical Er3+ quenching concentration (QC) was determined to be about 5 mol%, and the power studies indicated that mixture of 2- and 3-photon process was responsible for the green and red upconversion luminescence. [ABSTRACT FROM AUTHOR]

Alpha, beta, gamma, and delta hydroxyl ferric oxides (FeOOH), as the most common rust layers on iron surface, play different roles in iron preservation. Using modern surface analysis technologies such as X-ray diffraction (XRD), infrared spectra (IR), X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM), we studied the interactions between these four types of synthetic FeOOH and phosphoric and tannic acid of different concentrations and proportions. A 3% tannic acid + 10% phosphoric acid + FeOOH was the most suitable formula for rust stabilizer and its reaction products were made up of iron phosphate and chelate of iron and tannin. This research provided technical basis in distinguishing FeOOH and selecting rust layer stabilizer for the preservation of iron, especially iron cultural relics. [ABSTRACT FROM AUTHOR]

Emission-tunable phosphors Ca 9 La(PO 4 ) 5 (SiO 4 )F 2 :Ce 3+ ,Tb 3+ with apatite structure were synthesized by a solid-state reaction. The phase structure, photoluminescence (PL) properties, lifetimes and the PL thermal stability were investigated, respectively. The phosphor exhibited an asymmetric broad-band blue emission (Ce 3+ ) with peak at 403 nm and the line-type green emission with peak at 543 nm (Tb 3+ ). The varied color of the phosphors from blue to green can be achieved by properly tuning the relative ratio of Ce 3+ /Tb 3+ through the energy transfer from Ce 3+ to Tb 3+ ions. The critical distance was calculated to be 8.78 Å by using the concentration quenching method. When the temperature turned up to 150 °C, the emission intensity of Ca 9 La(PO 4 ) 5 (SiO 4 )F 2 :Ce 3+ ,Tb 3+ phosphor was 77% of its initial value at room temperature, which indicated the good thermal stability of the sample. All the properties indicate that the Ca 9 La(PO 4 ) 5 (SiO 4 )F 2 :Ce 3+ ,Tb 3+ phosphor has potential application of color-tunable w -LEDs. [ABSTRACT FROM AUTHOR]

An anti-defect engineering strategy, inspired by photocatalytic and photovoltaic materials, was proposed to develop high-efficiency phosphors in whitlockite families. Significant enhancement of photoluminescence intensity (2.46 times), thermal stability (87.92% at 150 °C), cathodoluminescence intensity (3.34 times), quantum efficiency (IQE sharply up to nearly 100%) were simultaneously realized by constructing a rigid structure and removing vacancy defects. The developed phosphors exhibited promising applications in the fields of warm-white LEDs, plant growth lighting and information security. [Display omitted] • Anti-defect engineering strategy is proposed to develop high-efficiency phosphors. • The internal quantum yield is sharply improved from 38.90% to 99.07%. • The mechanism of improvement is revealed by defect-related characterizations. • DFT calculation shows the positive role of Debye temperature and alkali metal ions. • Promising applications in warm-white LEDs / plant-growth lighting are demonstrated. Lacking an effective strategy to simultaneously address the challenges of quantum efficiency, luminescence intensity and thermal stability has become the key bottleneck for further development and large-scale application of solid-state lighting technology. Herein, inspired by the defect-engineering used in photoelectrocatalytic and photovoltaic materials, we acted in a diametrically opposite way and unprecedentedly proposed an anti-defect engineering strategy to develop high-efficiency phosphors. By constructing a rigid structure and introducing alkali metals M to remove cation vacancy defects, similar to building blocks and jigsaw puzzle, we developed three groups of whitlockite phosphors, namely Ca 3- x Sr x (PO 4) 2 :Ce3+, Ca 3 (PO 4) 2 :Ce3+, M and (Ca 0.5 Sr 0.5) 3 (PO 4) 2 :Ce3+,Na+,Mn2+, and synchronously realized the significant enhancement of photoluminescence intensity (2.46 times), thermal stability (87.92% at 150 °C), cathodoluminescence intensity (3.34 times), quantum yield (from 38.90% to 99.07%). We characterized the defect concentration by positron annihilation technique (PAT), and calculated Debye temperature (ΘD) and simulated the occupation of M according to DFT theory to reveal the improvement mechanism. Some advanced applications were also explored in this work, including warm-white LEDs, plant growth lighting and information security. The anti-defect engineering proposed in this work may contribute to the further development of high-efficiency phosphors for the next-generation smart solid-state lighting technologies. [ABSTRACT FROM AUTHOR]

Highlights: [•] Near-infrared emitting phosphors LaOCl:Nd3+/Yb3+ were prepared. [•] LaOCl:Nd3+/Yb3+ samples show strong near-infrared emission lines in the region of 1060–1150nm and 980–1050nm. [•] The possible energy transfer mechanism between Nd3+ and Yb3+ was discussed. [ABSTRACT FROM AUTHOR]

Novel reddish Mg 3 Gd 2 Ge 3 O 12 : RE3+ (RE = Sm, Eu) phosphors with high thermal stability have been designed and developed. In this work, Mg 3 Gd 2 Ge 3 O 12 was first synthesized for being used as the phosphor host. The X-ray diffraction and Rietveld refinement testified that the MGGO: Sm3+ and MGGO: Eu3+ crystallized in a cubic unit cell with space group I a-3d (230). The photoluminescence properties were studied in detail, MGGO: Sm3+ and MGGO: Eu3+ can be obviously excited at 403 and 395 nm, which could guarantee efficient absorption through commercial n -UV chip. Benefiting from the inverse garnet highly rigid framework, MGGO: 0.04Sm3+ and MGGO: 0.9Eu3+ phosphors had a favorable thermal resistance due to large activation energies (MGGO: 0.04Sm3+: 0.291 eV, MGGO: 0.9Eu3+: 0.238 eV). The emission intensity of MGGO: 0.04Sm3+ and MGGO: 0.9Eu3+ can still preserve about 97.85% and 91.58% at working temperature (423 K) compared to the initial intensity (298 K). All results indicated Mg 3 Gd 2 Ge 3 O 12 : RE3+ (RE = Sm, Eu) phosphors have potential usage for full-spectrum w-LED applications as red component. • Crystal structure of MGGO: 0.04Sm3+ and MGGO: 0.9Eu3+ phosphors are investigated in detail. • MGGO: 0.04Sm3+ and MGGO: 0.9Eu3+ phosphors have a favorable thermal resistance due to large activation energies. • MGGO: 0.04Sm3+ and MGGO: 0.9Eu3+ can be obviously excited at 403 and 395 nm. • CIE chromaticity coordinates of MGGO: 0.04Sm3+ and MGGO: 0.9Eu3+ are (0.5153, 0.4709) and (0.4937, 0.3765). [ABSTRACT FROM AUTHOR]

Abstract: A visible-light-active TiO2−x N x photocatalyst was synthesized in electric field. The N-doping TiO2 film had a thickness of about 70–80nm. The results of the photocatalytic experiments showed that the vis-activity rose largely. XPS and XRD analysis implied that the doping N substituted the oxygen-deficient in TiO2 film. The Einstein shift in optical absorption spectrum of the N-doped film was also observed by the UV–VIS with a cut wave length of about 550nm. Based on the experiment, it could be concluded that the N doping is effective to narrow the gap and enhance the photocatalysis. [Copyright &y& Elsevier]

Rare earth doped luminescent sensing materials as non-contact thermometers have attracted extensive research interests due to their wide applications in areas like military, medical care, aerospace, etc. How to expand the working temperature range and improve the sensitivity has become the focus. In this work, we synthesized a series of apatite-structured luminescent temperature sensors M 2 La 7.9 Ce 0.1 (SiO 4) 6 O 2 (M = Ca, Sr, Ba) via isomorphic substitution. By monitoring the differential changes of emission intensities from Ce3+ at the 7-coordinate and 9-coordinate site respectively when temperature varies, the real-time temperature can be determined. These materials were proven to possess the maximum absolute sensitivity up to 0.825 × 10−3 K−1, 2.63 × 10−3 K−1 and 4.33 × 10−3 K−1, respectively. Meanwhile interesting regular patterns were observed for their temperature sensitivities with the substitution of Ca, Sr and Ba. Furthermore, through studying the temperature sensitivity of Ba 2 La 8 (SiO 4) 6 O 2 : x Ce3+ samples with different concentrations, it was found that when the Ce3+ content was at the optimal doping concentration of 0.7, the absolute sensitivity of the sample reached 14.64 × 10−3 K−1 at 573 K. This finding has opened up a new avenue for designing fluorescent temperature sensors. Synopsis: In this work, Ce3+ were doped into a series of phosphor-structured matrices containing two cationic sites (7-coordinated Ce1 and 9-coordinated Ce2 sites) via the solid-state high-temperature method. Due to the different temperature dependencies of luminescence intensities between the two Ce3+ sites, their intensity ratio could be used for temperature calibration. [Display omitted] [ABSTRACT FROM AUTHOR]

Hydroxyapatite (HAP) commonly undergoes doping with various dopants, leading to the emergence of new properties. In this study, HAP is co-doped by terbium (Tb) and europium (Eu) to impart HAP with photoluminescent properties. By controlling the Tb3+ amount to 7.5 × 10−5 mol unchanged, it is observed that when the doping amount of Eu3+ reaches 4.0 × 10−5 mol, the band gap measures 3.919 eV, with maximum fluorescence intensity. Notably, a dipole-dipole energy transfer type from Tb3+ to Eu3 was identified during this process. Concentration quenching occurs when the Eu3+ amount exceeds 4.0 × 10−5 mol. In addition, the Tb3+ and Eu3+ co-doped HAP demonstrates excellent thermal stability and a more comprehensive emission wavelength range than Tb3+-doped HAP or Eu3+-doped HAP. Considering these properties, Tb3+ and Eu3+ co-doped HAP phosphor and aramid/polyphenylene sulfide (ACFs/PPS) fiber paper are organically compounded, resulting in functional fabrics with excellent low-temperature stability. These available fabrics are made of luminescent crystals and fibers can be applied in fields such as high-performance textile testing. Notably, when a specific laser irradiates the damaged area of the textile, fluorescence is not detected by the detector. Moreover, Tb3+ and Eu3+ co-doped HAP has also been shown to be used in the light-emitting diode (LED) to produce the HAP-LED that emits warm white light without commercial phosphors. That expands the application of HAP in anti-counterfeiting, flexible wearables, high-performance textile testing, and semiconductor devices. The color-tunable Tb3+ and Eu3+ co-doped HAP is prepared by hydrothermal synthesis co-precipitation. The energy transfer process between Tb3+ and Eu3+ is proved and the application possibility of Tb3+ and Eu3+ co-doped HAP in fluorescence anti-counterfeiting and LED is discovered. [Display omitted] • The energy transfer mechanism of Tb3+ and Eu3+ in HAP was studied. • By controlling the doping amount of Eu3+, the fluorescence color of Tb3+ and Eu3+ co-doped HAP was tunable. • It expands the application of hydroxyapatite in fluorescent anti-counterfeiting and LED. • HAP exhibited excellent stability when combined with fibers for anti-counterfeiting applications. • The LED emitting bright white light was prepared by using Tb3+ and Eu3+ co-doped HAP without commercial phosphor. [ABSTRACT FROM AUTHOR]

Cryolite-type materials have advantages of low phonon energy, easy rare-earth ion doping, and stable physicochemical properties, and they are considered ideal matrices for up-converting luminescent materials. In this paper, a series of K 3 LuF 6 :Er3+,Yb3+ up-converting materials with cryolite structure were prepared for the first time by high-temperature solid-phase method. The compositions, structures and luminescent properties were systematically characterized by X-ray powder diffractometry (XRD), field emission scanning electron microscopy (SEM) and fluorescence spectroscopy (PL). Under 980 nm excitation, the sample emission spectra mainly consisted of green and red emission bands with peaks at 525, 546 and 662 nm, corresponding to the 2H 11/2 -4I 15/2 , 4S 3/2 -4I 15/2 and 4F 9/2 -4I 15/2 electron transitions of Er3+, respectively. In addition, the temperature sensing characteristics of two thermally coupled energy levels (2H 2/11 and 4S 3/2) were studied based on the fluorescence intensity ratio (FIR) technique in the range of 79–579 K. All the results show that K 3 LuF 6 :Er3+/Yb3+ up-converting luminescent materials have excellent temperature sensing performance in the ultra-wide temperature range and have broad application prospects in the field of temperature sensing. [ABSTRACT FROM AUTHOR]

What ideal w-LED phosphors always aim to do is to achieve a single phase near-sunlight emission phosphor simultaneously with both high luminescence efficiency and high thermal stability at operation temperature. And It is well known that apatite compound phosphors are one of the most promising optical materials to realize those above because of their unique structure enhanced luminescence properties and thermal stability. Here, we synthesized a co-doped single phase apatite phosphors Ca2La8(SiO4)6O2:Dy3+/Sm3+ (CLSO:Dy3+/Sm3+) for white light emission, which was provided with excellent thermal stability and of which luminescence intensity at 150 °C still was 92 percentage of that at room temperature. Moreover, X-ray diffraction technique, Fourier transform infrared spectroscopy, scanning electron microscope were employed to characterization of phase structure and morphology, and consequently pure apatite structure and gravel-like morphology of phosphors were proved. Analysis of photoluminescence spectra indicated that concentration quenching effect exist in single-doped CLSO:Dy3+ phosphors owing to dipole-dipole interaction between Dy3+ ions. It is revealed that maybe exist Dy3+ ↔ Sm3+ bilateral non-radiative energy transfer processes in Dy3+/Sm3+ co-doped CLSO system by PL spectra and decay curves. And variation of Sm3+ ion concentration can control color emission, namely CIE chromaticity coordinates and correlated color temperature, finally to achieve white light emission (0.309,0.309) with CCT 6848 K, able to be a potential candidate for commercial lighting applications. [ABSTRACT FROM AUTHOR]

The combination of up-conversion materials and photocatalysts can produce the effect of "redshifting" of absorption spectrum, which is of great significance for improving the degradation efficiency of photocatalysts. To improve the utilization of CdS in near-infrared light, the up-conversion luminescent material K3ScF6:Tm3+,Yb3+ with cryolite structure was synthesized by high-temperature solid-phase reaction method, and a new photocatalytic composite material K3ScF6:Tm3+,Yb3 + /CdS was prepared by combining it with CdS by high-energy ball milling method. The composition, structure and properties were systematically characterized by X-ray powder diffractometer ( XRD), field emission scanning electron microscopy ( SEM), fluorescence spectroscopy (PL) and UV-Vis diffuse reflection absorption spectroscopy. Simultaneously, the photodegradation efficiency and mechanism of K3 ScF6: Tm3 +, Yb3 + /CdS to rhodamine B ( RhB) were studied. The results show that the optimal mass composition ratio of K3ScF6:Tm3+,Yb3 + and CdS is 3. 6:1, and the introduction of up-conversion luminescent materials K3ScF6:Tm3+,Yb3 + synergistically promots the photocatalytic efficiency of CdS. The • OH and • O²- participated in the degradation of RhB, and • OH plays a major role. In addition, under the optimal recombination ratio, the degradation rate of K3ScF6:Tm3+, Yb3 + /CdS samples reaches 99. 9%, which is nearly 50 times higher than that of uncompounded CdS after 80 min. All results show that K3 ScF6: Tm3 +, Yb3 + /CdS photocatalytic composites has potential application value in the field of photocatalysis. [ABSTRACT FROM AUTHOR]

Abstract A set of Eu3+, Dy3+ and Tb3+ doped novel scheelite-type LiCaGd(WO 4) 3 (LCGW)-based phosphors was prepared via a conventional solid-state reaction method. The X-ray diffraction (XRD), transmission electron microscopy (TEM) analysis, characteristics of luminescence, PL thermostability, decay lifetimes, as well as CIE coordination were investigated to characterize the as-prepared samples in detail. The XRD analysis indicated that the Eu3+, Dy3+ and Tb3+ ions were incorporated into the LCGW host lattice. Under the ultraviolet radiation, the characteristic emission lines of Eu3+ (5D 0 –7F 2), Dy3+ (4F 9/2 –6H 13/2) and Tb3+ (5D 4 –7F 5) ions were observed. The Eu3+ and Tb3+ single-doped LCGW fluorescent powders showed bright red and green emissions, respectively, without concentration quenching. As well as the Dy3+ doped LCGW phosphors radiate a strong yellow light at optimal Dy3+ concentration 0.08 mol. The efficient energy transfer phenomenon was observed for the Eu3+/Dy3+ and Tb3+/Dy3+ ions. The emission color of the LCGW: x Tb3+/0.08Dy3+ samples was tuned from yellow (0.4074, 0.4727) to green (0.3604, 0.5521) via adjusting the Tb3+ concentration. The emission color of LCGW: y Eu3+/0.08Dy3+ can be tuned from yellow (0.491, 0.3856) to red (0.5694, 0.3512) by variation of the Eu3+/Dy3+ ratio. Additionally, the thermal stability of the luminescence in the LCGW phosphors doped by Eu3+, Tb3+, Dy3+ ions was studied. The results verified that the LCGW:Ln3+ (Ln = Tb, Eu, Dy) phosphors are promising for applications in white LEDs. [ABSTRACT FROM AUTHOR]

Abstract A series of reddish-emitting apatite-type phosphor LiGd 9 (SiO 4) 6 O 2 :Sm3+ was prepared by using an appropriate solid-state method. The photoluminescence (PL), photoluminescence excitation (PLE) spectra, and decay times of the samples were characterized to investigate the photoluminescence properties for application in white light-emitting diodes (w -LEDs). The photoluminescence investigations showed that LiGd 9 (SiO 4) 6 O 2 :Sm3+ phosphor emitted reddish emission, which ascribed to the transitions of the Sm3+ from the 4G 5/2 excited state to the 6H 5/2 , 6H 7/2 , and 6H 9/2 states, respectively. The critical quenching concentration of Sm3+ in LiGd 9 (SiO 4) 6 O 2 phosphors were determined to be about 3 mol%. Moreover, the spectroscopic data and fluorescence decay dynamics indicate that the energy transfer from Gd3+ to Sm3+ ions takes place in LiGd 9 (SiO 4) 6 O 2 : Sm3+ phosphor. All the results indicated that the LiGd 9 (SiO 4) 6 O 2 : Sm3+ phosphor could efficiently assimilate the near ultraviolet (n -UV) light and act as a suitable warm light candidate for n -UV w -LEDs. [ABSTRACT FROM AUTHOR]

We develop a facile and rapid cation exchange method for upconversion nanocrystals (UCNCs) without removing surface ligands. It avoids the tedious pretreatment of as-synthesized UCNCs, and the luminescent intensities of nanocrystals after Tb3+ exchange using the new method are much stronger than those of the nanocrystals obtained using conventional cation exchange in water. [ABSTRACT FROM AUTHOR]

The oxygen evolution reaction (OER) is one of the core reaction modules of important renewable energy technologies with applications in water splitting, metal-air (oxygen) cells and regenerative fuel cells. However, OER catalysts are forced to operate with a significant intrinsic overpotential and inefficient charge transfer due to the adsorption energy scaling balance between the reaction intermediates. It is critical to develop an understanding of structure-activity relationship of catalysts, determine the speed control steps and improve catalytic activity. In this work, cobalt pentlandite (Co , Ni , Fe) 9 S 8 (CNFS) electrocatalysts were successfully prepared by combining the earth-abundant transition metal elements Co, Ni and Fe into a single structure. Benefiting from the structure, nanoflower morphology, and the synergistic effect among the three elements, the optimized sample requires an overpotential of only 335 mV to drive a current density of 50 mA cm–2 under alkaline conditions. The experimental results establish a composition-structure-function relationship, and the density functional theory results further indicate that the Fe sites bind more moderately to the intermediates and the electron synergistic effect occurs dynamically during the OER cycle reaction. This work not only provides a very promising catalyst candidate for efficient OER processes but also highlights the superiority of the cobalt pentlandite structure in the rational design of efficient OER electrocatalysts. • We synthesized natural mineral structures of cobalt pentlandite (Co,Ni,Fe) 9 S 8 structured OER catalysts. • Synergistic effect among the Co, Ni and Fe accelerates charge transfer and results in superior catalytic activity. • DFT calculations illustrate that the cobalt pentlandite (Co,Ni,Fe) 9 S 8 have an active OER site at the interface Fe site. [ABSTRACT FROM AUTHOR]

In this work, a method for controllable regulation of crystal form was proposed for the first time and the effects of different crystal forms on the up‐conversion luminescence properties of Ho3+, Yb3+ co‐doped K3Sc0.5Lu0.5F6 (KSLF) phosphors was explored. KSLF:Ho3+, Yb3+ phosphors were synthesized by the high temperature solid‐state reaction method, and X‐ray diffraction (XRD) results illustrate that the compounds can obtain monoclinic phase and cubic phase at different synthesis temperatures. In addition, according to the power‐dependent up‐conversion luminescence (UCL) intensity, the UCL mechanism and the electronic transition process are discussed. Simultaneously, the temperature sensing behavior of the best samples with different crystal forms at different temperatures was studied by fluorescence intensity ratio technique. All the results show that KSLF:Ho3+, Yb3+ phosphors show great application potential in the field of temperature sensing, and the preparation of KSLF:Ho3+, Yb3+ in different crystal forms can provide a reference value for crystal design and growth. [ABSTRACT FROM AUTHOR]

A series of novel luminescent emission-tunable phosphors Mg 2 La 8 (SiO 4 ) 6 O 2 :Ce 3+ ,Tb 3+ (MLS:Ce 3+ ,Tb 3+ ) have been prepared by a solid-state reaction. The phase formation was firstly confirmed through X-ray diffraction technique and refined by the Rietveld method. The MLS:Ce 3+ ,Tb 3+ phosphors, which crystallized in apatite-type hexagonal phase, exhibited a broad excitation band ranging from 200 to 400 nm and several emission bands centered at 426 nm and 551 nm. Energy transfer from Ce 3+ to Tb 3+ ions via a dipole-dipole mechanism occurred in the as-synthesized phosphors upon ultraviolet (UV) excitation. The energy transfer efficiency increases with increasing doping content of Tb 3+ ions, which was confirmed by the luminescence spectra and fluorescence decay curves of corresponding ions simultaneously. The energy transfer critical distance was calculated and evaluated by both the concentration quenching and spectral overlap methods. The chromaticity of emission-tunable phosphors was also characterized by the Commission International de l'éclairage (CIE) chromaticity indexes, and the color tone can be tuned from blue (0.179, 0.122) to green (0.267, 0.408) by controlling the ratio of Ce 3+ /Tb 3+ . [ABSTRACT FROM AUTHOR]

A series of solid solution phosphors Ca 9 La(PO 4 ) 5 [(Si 1- x Ge x )O 4 ]F 2 :Ce 3+ with apatite structure in the P 6 3 / m space group have been prepared. The novel solid solution phosphors show continuously controlled violet-blue emission. It is found that both substantial spectra broadening (45 → 100 nm) and red-shift (404 → 422 nm) can be realized with the continuous introduction of [GeO 4 ] 4- into the crystal lattice which has been simulated by a crystal-field model. The above results indicate that the tetrahedral substitution is interesting to induce spectral tuning properties based on the chemical composition control of the iso-structural solid solutions. [ABSTRACT FROM AUTHOR]

The constructed high-efficient cyan-emitting phosphors establish a bifunctional platform involving high-color-quality lighting and anti-counterfeiting application. [Display omitted] • Ca 8 ZnY(PO 4) 7 :Eu2+ phosphors exhibited a broad cyan-emitting spectra (FWHM = 78 nm). • The quantum yield of Ca 8 ZnY(PO 4) 7 :Eu2+ phosphor is as high as 72.11 %. • The CRI value of warm w -LED devices was greatly enhanced from 83.9 to 90.5. • The transparent anticounterfeiting film held great potentials in packaging field. Constructing the broad-band emitting luminescent materials with high quantum yield is of great significance towards their widespread applications. Herein, series of Eu2+ activated, whitlockite-type Ca 8 ZnY(PO 4) 7 phosphors are developed towards bifunctional platform involving the white LED and anti-counterfeiting field. Benefiting from the typical 5d-4f transitions among Eu2+ ions, the broad asymmetric cyan-emission spectra (FWHM = 78 nm) is generated under 365 nm excitation with a highest quantum yield of ∼72.11 %. The optimal doping concentration of Eu2+ ions in the Ca 8 ZnY(PO 4) 7 host is determined as 4 % and the concentration quenching mechanism is mainly attributed to a dipole–dipole interaction. Impressively, after exploiting the newly discovered cyan-emitting phosphors Ca 8 ZnY(PO 4) 7 :Eu2+, the CRI value of as-prepared warm w -LED devices is remarkably enhanced from 83.9 to 90.5. Moreover, the w -LED exhibits an applicable correlated color temperature (CCT = 4176 K) and good color stability. Additionally, the transparent anticounterfeiting film is fabricated based on the highly efficient phosphors and soluble PVA, which presents anticounterfeiting performances due to their bright cyan emission upon UV light. Notably, their sustainability, excellent flexibility and foldability provide more possibilities applied for anticounterfeiting field. These results suggest the highly efficient phosphors Ca 8 ZnY(PO 4) 7 :Eu2+ are promising bifunctional luminescent platforms, for both high-color-quality lighting and anticounterfeiting applications. [ABSTRACT FROM AUTHOR]

In this study, La 2 (MoO 4) 3 doped with Eu3+ was synthesized by the high-temperature solid-state method. The phase composition of the Eu3+-doped La 2 (MoO 4) 3 sample was confirmed by X-ray powder diffraction (XRD) analysis, and the microstructure was observed via the scanning electron microscopy (SEM). Under the excitation at 211 nm, the room temperature emission spectra of Eu3+ in the samples with different doping levels were recorded. In addition, the prepared La 2 (MoO 4) 3 : x Eu3+ (x = 0–0.25) phosphors were color tunable. A non-contact optical thermometer with high sensitivity and high-temperature resolution was fabricated based on the different thermal quenching behaviors of the Mo–O group and Eu3+ center. The fluorescence intensity ratio (FIR), temperature resolution (ΔT), maximum absolute and relative sensor sensitivity (Sa and Sr) of La 2 (MoO 4) 3 :Eu3+ were calculated according to different thermal quenching effects between room temperature (298K) and 573K of Eu3+ and Mo–O group. These results show that La 2 (MoO 4) 3 :Eu3+ has excellent sensitivity and temperature resolution, good reversibility and reliability, as Sa = 0.0525 K-1, Sr = 0.3724. % K−1, ΔT = 0.0806 K and the FIR error was only 0.62%. Therefore, the Eu3+-doped La 2 (MoO 4) 3 is a promising candidate material for high performance non-contact optical thermometers. [ABSTRACT FROM AUTHOR]

A series of novel green emission Whitlockite-type Ca8ZnLa(PO4)7:Eu2+ and color tunable Ca8ZnLa(PO4)7:Eu2+,Mn2+ phosphors were prepared by the solid-state reaction method in a reducing atmosphere. Its crystal structure and phase composition were identified by high-resolution transmission electron microscopy, selected area electronic diffraction, X-ray photoelectron spectroscopy, and X-ray powder diffraction Rietveld refinement, and it was found to be trigonal, belonging to R-3 c(161) space group. The luminescence properties of Eu2+ singly doped and Eu2+/Mn2+ codoped Ca8ZnLa(PO4)7 phosphors were revealed in detail. Ca8ZnLa(PO4)7:Eu2+ is excitable over a broad range from 200 to 450 nm with a prominent green emitting. With varied Eu2+/Mn2+ ratios, fine-tune emission under 365 nm excitation can be achieved from green (0.221, 0.468) to magenta (0.391, 0.276), especially the warm white light (0.392, 0.352), and CCT 3500 K can be obtained by the process of energy transfer between Eu2+ and Mn2+. The ET mechanism in this system is managed via the dipole-dipole interaction with the maximum energy-transfer efficiency 82.8% based on the decay lifetime data. These results suggest that as-prepared phosphors can serve as promising candidates of UV-pumped w- LEDs. [ABSTRACT FROM AUTHOR]

A series of blue-emitting La 5.90− x Ba 4+ x (SiO 4 ) 6− x (PO 4 ) x F 2 :0.10Ce 3+ ( x = 0, 1, 2, and 3) phosphors with apatite structure were synthesized by a solid-state reaction. The crystal structure and the photoluminescence properties were investigated in detail. The crystallographic occupancy of Ce 3+ in La 2.90 Ce 0.10 Ba 7 (SiO 4 ) 3 (PO 4 ) 3 F 2 and La 5.90 Ce 0.10 Ba 4 (SiO 4 ) 6 F 2 were studied based on Rietveld refinements results and the crystal chemistry rules. La 5.90− x Ba 4+ x (SiO 4 ) 6− x (PO 4 ) x F 2 :0.10Ce 3+ exhibited strong blue light emission in the range of 407–414 nm with high thermal stability upon excitation at 276 nm. Besides, the activation energy E of La 5.90 Ce 0.10 Ba 4 (SiO 4 ) 6 F 2 and La 2.90 Ce 0.10 Ba 7 (SiO 4 ) 3 (PO 4 ) 3 F 2 phosphors were calculated to be 0.152 and 0.177 eV. These results suggest that La 5.90− x Ba 4+ x (SiO 4 ) 6− x (PO 4 ) x F 2 :0.10Ce 3+ is a potential blue phosphor candidate for near-UV-pumped w -LEDs. [ABSTRACT FROM AUTHOR]

Single-phase Ba 10− x − y (PO 4 ) 6 O: x Eu 2+ , y Mn 2+ samples with apatite structure have been synthesized via a solid-state reaction method. The phase structure, luminescence properties, lifetime, PL thermal stability, as well as fluorescence decay curves of the samples were investigated. Effective energy transfer occurs from Eu 2+ to Mn 2+ in Ba 10 (PO 4 ) 6 O and a possible mechanism of the energy-transfer from Eu 2+ to Mn 2+ is proposed. The critical distances R c was calculated by concentration quenching and turned out to be about 0.817 nm ( x c =0.21). The CIE and thermally stable luminescence behaviors of Ba 9.94 (PO 4 ) 6 O:0.06Eu 2+ phosphor were also studied in detail. All the results indicate that Ba 10− x − y (PO 4 ) 6 O: x Eu 2+ , y Mn 2+ phosphors have potential applications as near UV-convertible phosphors for white light-emitting diodes. [ABSTRACT FROM AUTHOR]

Currently, the application potential of Cr3+ doped near-infrared (NIR) fluoride phosphors excited by blue light is promising. However, the development of near-infrared fluoride phosphors with wider emission bandwidth remains a challenge. Herein, we employed the hydrothermal method to prepare K 2 NaCrF 6 :Fe3+ phosphors. Upon excitation at 432 nm, the K 2 NaCrF 6 :xFe3+ phosphors exhibited broad near-infrared emission, with the main peak ranging from 752 nm to 780 nm. As the Fe3+ concentration increased, the luminescence intensity of the K 2 NaCrF 6 :xFe3+ phosphor decreased, accompanied by a redshift in the emission band and an increase in the full width of the emission spectrum half-peak. These changes can be attributed to the dipole-dipole interaction, specifically the energy transfer between Fe3+ and Cr3+, leading to the 4T 2 (4F) → 4A 2 (Cr3+) and 4T 1 (4G) → 6A 1 (6S) (Fe3+) transitions. • K 2 NaCrF 6 :Fe3+ phosphors display application potential for near-infrared (NIR) fluorescence when excited by blue light. • The developed phosphors exhibit a broad near-infrared emission bandwidth (752–780 nm) under 432 nm excitation. • Increasing Fe3+ concentration leads to redshift and broadening of the emission spectrum. • Luminescent changes are attributed to dipole-dipole interactions and efficient energy transfer. • Cr3+ and Fe3+ enables synchronous excitation processes, offering versatility for applications in spectroscopy. [ABSTRACT FROM AUTHOR]

Rare earth ion doped fluorescent powder, as a key material for the application of white light-emitting diodes (w-LEDs), green components often face the problem of poor thermal stability. Developing fluorescent powders with excellent thermal stability is of great significance. This article synthesized a series of Gd 5 Si 2 BO 13 :Tb3+ blue phosphors and non rare earth Bi3+ ion doped Gd 5 Si 2 BO 13 :Tb3+ green phosphors using a high-temperature solid-phase method. The phase structure and photoluminescence characteristics of the sample were analyzed in detail through XRD, excitation and emission spectra, as well as attenuation curves. The energy transfer from Bi3+ to Tb3+ was studied and confirmed through photoluminescence spectra and lifetime decay curves. Research has shown that the addition of Bi3+ significantly enhances the emission intensity of Tb3+ in the near ultraviolet range, and tunes the emission color of Gd 5 Si 2 BO 13 :Bi3+ and Tb3+ from blue to green, attributed to the energy transfer from Bi3+ to Tb3+. In addition, the addition of Bi3+ increased the thermal stability of single doped fluorescent powder Gd 5 Si 2 BO 13 :0.55Tb3+ from 88.21 % to 92.82 % at 150 °C, proving that the Gd 5 Si 2 BO 13 :Bi3+ and Tb3+ samples have good thermal stability. This study not only deepens our understanding of the new main material Gd 5 Si 2 BO 13 , but also provides a reference for the development of green phosphors with excellent thermal stability. [Display omitted] • A series of Gd 5 Si 2 BO 13 :Bi3+, Tb3+ phosphors were successfully synthesized. • The co-doped Gd 5 Si 2 BO 13 :Bi3+, Tb3+ phosphors have excellent emission intensity and thermal stability. • The Gd 5 Si 2 BO 13 :Bi3+, Tb3+ green phosphors is promising for use in high-power LED lighting devices and backlight displays. [ABSTRACT FROM AUTHOR]

A series of novel luminescent phosphors Sr 10 (PO 4 ) 6 O:Eu 2+ with apatite structure were synthesized via a high temperature solid-state reaction. The phase structure, photoluminescence (PL) properties, the PL thermal stability, as well as the fluorescence decay curves of the samples were investigated to characterize the resulting samples, and the selected Sr 9.97 (PO 4 ) 6 O:0.03Eu 2+ phosphor exhibits strong thermal quenching resistance, retaining the luminance of 88.73% at 150 °C. The quenching concentration of Eu 2+ in Sr 10 (PO 4 ) 6 O was about 0.03 attributing to the dipole–quadrupole interaction. The Sr 10 (PO 4 ) 6 O:Eu 2+ phosphor exhibited a broad-band blue emission at 439 nm upon excitation at 346 nm. The results indicate that Sr 10 (PO 4 ) 6 O:Eu 2+ phosphors have potential applications as near UV-convertible phosphors for white-light UV LEDs. [ABSTRACT FROM AUTHOR]

A series of new luminescent emission-tunable phosphors Sr 2 La 8 (SiO 4 ) 6 O 2 :Ce 3+ , Tb 3+ with apatite structure have been synthesized by a high temperature solid-state reaction. The phase structure, photoluminescence emission and excitation spectra, lifetime, as well as the effect of Tb 3+ concentration are investigated to characterize the resulting samples. The critical distance was calculated to be 8.26 Å by using the concentration quenching method. The intense green emission was observed in the Sr 2 La 8 (SiO 4 ) 6 O 2 :Ce 3+ , Tb 3+ phosphors on the basis of the efficient energy transfer from Ce 3+ to Tb 3+ with an efficiency of 68.55%. And a possible mechanism of the energy-transfer from Ce 3+ to Tb 3+ ion is also proposed. The results indicate that Sr 2 La 8 (SiO 4 ) 6 O 2 :Ce 3+ , Tb 3+ phosphors have potential applications to be used as near UV-convertible phosphors for white light-emitting diodes because of the broad excitation in the near-ultraviolet range and the efficient green emission light. [ABSTRACT FROM AUTHOR]

SrIn2O4, which shows lower phonon energy than CaIn2O4, is not only a good photocatalyst but also can be an excellent up-conversion (UC) host to exhibits UC luminescence. In this work, Yb3+ and/or Er3+ doped SrIn2O4 phosphors were synthesized, and their UC luminescence properties were studied and compared with those in the CaIn2O4 host. The structure of SrIn2O4: 0.01Er3+ and SrIn2O4: 0.1Yb3+/0.01Er3+ samples were refined by the Rietveld method and found to that SrIn2O4: 0.1Yb3+/0.01Er3+ showed increasing unit cell parameters and cell volume, indicating In3+ sites were substituted successfully by Yb3+ and/or Er3+ ions. From the UC luminescence spectra and diffuse reflection spectra, Er3+-doped SrIn2O4 showed very weak luminescence due to ground state absorption of Er3+; Yb3+/Er3+ codoped SrIn2O4 presented strong green (550 nm) and red (663 nm) UC emissions which were assigned to energy transfer from Yb3+ transition 2F7/2→2F5/2 to the Er3+ transition 4S3/2 → 4I15/2 and 4F9/2 → 4I15/2. Comparing with CaIn2O4, Yb3+/Er3+ codoped SrIn2O4 showed obvious advantages with higher UC luminescent intensity. The pumping powers study showed that UC emissions in Yb3+/Er3+ codoped SrIn2O4 were attributed to energy transfer of Yb3+→Er3+ with a two-photon process. The possible UC luminescent mechanism of Yb3+/Er3+-doped SrIn2O4 was discussed. [ABSTRACT FROM AUTHOR]

Near-infrared excited up-conversion phosphors of RE 3+ /Yb 3+ (RE = Ho, Tm) co-doped SrIn 2 O 4 were synthesized by a solid-state reaction method. X-ray diffraction analysis revealed the phase composition of those samples, and the up-conversion spectroscopic properties were studied in terms of up-conversion emission spectra. Under 980 nm near-infrared laser excitation, strong green emission with the peak at 546 nm was observed in SrIn 2 O 4 : Ho 3+ /Yb 3+ , which can be assigned to the characteristic 5 S 2 ( 5 F 4 ) → 5 I 8 transition of Ho 3+ . Furthermore, SrIn 2 O 4 : Tm 3+ /Yb 3+ showed bright blue emission with the peak at 486 nm, which is associated with the 1 G 4 → 3 H 6 transition of Tm 3+ . The UC power studies indicated that the luminescence of SrIn 2 O 4 : Ho 3+ /Yb 3+ and SrIn 2 O 4 : Tm 3+ /Yb 3+ are attributed to two-photon and three-photon process, respectively. The possible UC luminescence mechanism and energy transfer in SrIn 2 O 4 : RE 3+ /Yb 3+ were discussed. [ABSTRACT FROM AUTHOR]

This study employs molecular dynamics modeling to examine the interlayer microstructures of montmorillonite intercalated with different chains of C n mimCl montmorillonites with varying chain lengths, intercalation amount, arrangement and energy. C 4 mim + and C 8 mim + arrange themselves in monolayers, while C 12 mim + and C 16 mim + in parallel bilayers or tilt aligning. The basal spacing of montmorillonite and the corresponding energy increased as the chain length of organic cations is increased. It is indicated that no bond has been formed for N + O due to the minimum distances of no less than 3.1 Å and angles of 35°–45° between N + in C n mim + and silicon–oxygen tetrahedron. These modeling results provide insights into the understanding of synthesized C n mim + -montmorillonite microstructure and guidelines for relevant engineering applications. [ABSTRACT FROM AUTHOR]