Efficient near-infrared pyroxene phosphor LiInGe2O6:Cr3+ for NIR spectroscopy application

Broadband near-infrared phosphors are essential to realize nondestructive analysis in food industry and biomedical areas. Efficient long-wavelength (>830 nm) phosphors are strongly desired for practical applications. Herein, we demonstrate an efficient broadband NIR phosphor LiInGe₂O₆:Cr³⁺, which exhibits a broad NIR emission peaking at ~880 nm with a full width at half maximum of 172 nm upon 460 nm excitation. The internal/external quantum efficiencies of LiInGe₂O₆:Cr³⁺ are measured to be 81.2% and 39.8%, respectively. The absorption of the phosphor matches well with commercial blue LEDs. Using the fabricated phosphor converted LED illuminating human palm, distribution of blood vessels can be clearly recognized under a NIR camera. These results indicate that LiInGe₂O₆:Cr³⁺ is a promising candidate to be used in future non-destructive biological applications.     

Broadband near-infrared emission enhancement in K2Ga2Sn6O16:Cr3+ phosphor by electron-lattice coupling regulation

Cr³⁺-doped phosphors have recently gained attention for their application in broadband near-infrared phosphor-converted light-emitting diodes (pc-LEDs), but generally exhibit low efficiency. In this work, K₂Ga₂Sn₆O₁₆:Cr³⁺ (KGSO:Cr) phosphor was designed and synthesized. The experimental results show that the Cr³⁺-doped phosphor exhibited broadband emissivity in the range 650-1300 nm, with a full width at half maximum (FWHM) of approximately 220-230 nm excited by a wavelength of 450 nm. With the co-doping of Gd³⁺ ions, the internal quantum efficiency (IQE) of the KGSO:Cr phosphor increased from 34% to 48%. The Gd³⁺ ions acted neither as activators nor sensitizers, but to justify the crystal field environment for efficient Cr³⁺ ions broad emission. The Huang-Rhys factor decreased as the co-doping of Gd³⁺ ions increased, demonstrating that the nonradiative transitions were suppressed. An efficient strategy for enhancing the luminescence properties of Cr³⁺ ions is proposed for the first time. The Gd³⁺–co-doped KGSO:Cr phosphor is a promising candidate for broadband NIR pc-LEDs.     

Novel double-perovskite Mg2InSbO6:Sm3+ phosphor with excellent heat-resistant performance and high color purity used in white LEDs

In this study, Sm³⁺-doped double-perovskite Mg₂InSbO₆ phosphors were synthesized via high-temperature solid-state reaction. Mg₂InSbO₆ belongs to the double-perovskite family with a space group of R (No.148). The photoluminescence (PL) spectrum illustrates that Mg₂InSbO₆:0.05Sm³⁺ phosphor can emit intense orange-red emission light at 607 nm due to the ⁴G_5/2→⁶H_7/2 transition. The optimum concentration of Mg₂InSbO₆:xSm³⁺ is confirmed to 0.05 mol. The asymmetric ratio (⁴G_5/2→⁶H_9/2/⁴G_5/2→⁶H_5/2) of Mg₂InSbO₆:0.05Sm³⁺ phosphor is 2.73. The quenching temperature exceeds 500 K, illustrating that Mg₂InSbO₆:Sm³⁺ sample has excellent heat resistance. The high color purity and correlated color temperature (CCT) of Mg₂InSbO₆:Sm³⁺ phosphors are obtained. Furthermore, a white light-emitting diode (w-LED) is successfully fabricated, possessing CCT of 6769 K and high color rendering index (R_a) of 89. Therefore, the orange-red-emitting Mg₂InSbO₆:Sm³⁺ phosphors exhibit great potential to apply in solid-state lighting fields.     

Luminescence properties of novel Eu3+-doped tantalate NaCaTiTaO6 red-emitting phosphors for solid-state lighting

A novel tantalate red-emitting phosphors NaCa_1-xEu_xTiTaO₆ (x = 0.02-0.50) is synthesized via the traditional solid-state reaction sintering. The photoluminescence properties, X-ray diffraction (XRD), scanning electron microscopy (SEM), and thermal stability are characterized in detail. Photoluminescence spectra show strong red emission monitored at 614 nm at λ_ex = 395 nm. The spectral properties exhibit excellent color purity and chromaticity coordinate (CIE) characteristics. White light-emitting diodes (w-LEDs) device are fabricated by the prepared phosphors and show high quality of color-rendering index. The investigated results suggest that the Eu³⁺-doped NaCaTiTaO₆ phosphors can be as potential substitute red phosphors for w-LEDs.     

Design of a defect-induced orange persistent luminescence phosphor BaZnGeO4:Bi3+

We report a novel bright orange persistent luminescence (PersL) phosphor BaZnGeO₄:Bi³⁺ with broad emission and PersL spectra. Its crystal structure, photoluminescence (PL) spectra, thermoluminescence (TL) spectra and PersL spectra were investigated in detail. The two emission bands at 440 nm and 595 nm originate from Bi³⁺ ions in normal Ba²⁺ sites (Bi1) and Ba²⁺ sites close to vacancy defects (Bi2), respectively. The introduction of and defects improves the emission intensity of Bi2 more than that of Bi1, demonstrating that Bi2 is related to the vacancy defects. The orange emission and PersL properties of BZGO:Bi³⁺ can be improved when a little and defects are introduced, because the introduction of and defects makes it easier for Bi³⁺ to enter in Ba²⁺ sites; and for PersL, and defects can perform as the effective trap centers to capture more charges, which is beneficial for PersL. BZGO:Bi³⁺ has quite good thermal stability, and the bright orange PersL can be observed by the naked eye for 1 h. Finally, a feasible PersL mechanism of BZGO:Bi³⁺ was proposed to clarify the PersL-generation process.     

Enhanced luminescence properties of Eu3+ in La2MoO6 by nonsensitization of Bi3+

It was unusual for Bi³⁺ ions to enhance the emission intensity of phosphors via nonsensitization. Here, La₂MoO₆:Eu³⁺, Bi³⁺ phosphors were successfully synthesized by a high temperature solid-state reaction method in air atmosphere. As the increase of doping concentration of Bi³⁺, the emission spectra of La₂MoO₆:Eu³⁺, Bi³⁺ phosphors had obvious shifts, splits and the enhancement of intensities, which indicated that the characteristics of the phosphors were modified. To analyze these phenomena, the crystal structure refinements, spectral characteristic analyze and Judd-Ofelt theoretical calculation were mainly performed. Bi³⁺ ions played the role of the nonsensitizer and affected the distortion of the crystal, the sites of Eu³⁺ ions, the field splitting energy and the internal quantum yield. Moreover the nephelauxetic effects of Bi³⁺ ions and the ET process caused synergistically the life times of La₂MoO₆:Eu³⁺, Bi³⁺ phosphors to increase and then gradually decrease. The CIE coordinates of phosphors changed within a small range. This study might be instrumental in promoting the further application of Bi³⁺ ions in rare earth luminescent materials.     

Controllable hydrothermal synthesis and photoluminescence properties of CaGd2(WO4)4:Eu3+ red-emitting phosphor

CaGd₂(WO₄)₄:Eu³⁺ phosphors with controllable morphology were synthesized via the hydrothermal method. The influences of pH value, reaction time and Eu³⁺ concentration on the crystal structure, morphology, and photoluminescence properties of CaGd₂(WO₄)₄:Eu³⁺ were studied. The pure tetragonal structure CaGd₂(WO₄)₄ is obtained when the pH value is 8 and 9. Furthermore, by altering the pH value of the reaction solution, the morphologies of the CaGd₂(WO₄)₄:Eu³⁺ phosphors evolve from spindle-shaped grains to tetragonal plate-like grains and finally to aggregated bulk particles. Under the 394 nm excitation, the phosphors display a bright red emission corresponding to the characteristic 4f-4f transitions of Eu³⁺, and the intensity of emission peaks depends mainly on the pH value, the reaction time, and the Eu³⁺ concentration. The optimum photoluminescence performance is achieved for CaGd_2-x(WO₄)₄:xEu³⁺ (x = 1) phosphor synthesized at pH = 8 under the reaction time of 16 h. Finally, the thermal stability of the phosphors is analyzed at different ambient temperatures.     

乳状液膜法提取Cr3+内相界面反应的研究

文章对乳状液膜法提取Cr3+内相界面的反萃取反应进行了研究。选择NaOH为反萃剂,H2O2为氧化剂,研究了内水相pH值、反应温度、搅拌速率、原料配比对反萃反应的影响,同时研究了反萃反应的反应方程式、反应的热力学性质。实验表明,反萃反应达平衡时的分配比随内相水溶液pH值及搅拌速度的升高而降低,随反应温度的升高而升高,随NaOH与[CrHn-mL(O)]2+摩尔比的增加先降低后升高;通过斜率法确定反萃反应为氧化-还原反应,并得到了反应的表观平衡常数k;计算了反萃反应的热焓ΔH,自由能ΔG和熵变ΔS。     

Mn4+-related photoemission enhancement via energy transfer in La2MgGeO6:Dy3+, Mn4+ phosphor for plant growth light-emitting diodes

A double perovskite-type substrate of La₂MgGeO₆ (LMGO) was successfully synthesized via a high-temperature solid-state reaction method and was codoped with Mn⁴⁺ and Dy³⁺ to form a new deep-red phosphor (LMGO:Mn⁴⁺,Dy³⁺) for artificial plant growth light-emitting diodes (LEDs). This extraordinary phosphor can exhibit strong far-red emission with a maximum peak at 708 nm between 650 and 750 nm, which can be ascribed to the ²E_g → ²A_2 g spin-forbidden transition of Mn⁴⁺. The X-ray diffraction (XRD) patterns and high-resolution transmission electron microscopy (HRTEM) clarified that the La³⁺ sites in the host were partly replaced by Dy³⁺ ions. Moreover, we discovered energy transfers from Dy³⁺ to Mn⁴⁺ by directly observing the significant overlap of the excitation spectrum of Mn⁴⁺ and the emission spectrum of Dy³⁺ as well as the systematic relative decline and growth of the emission bands of Dy³⁺ and Mn⁴⁺, respectively. With the increase in the activator (Mn⁴⁺) concentration, the relationship between the luminescence decay time and the energy transfer efficiency of the sensitizer (Dy³⁺) was studied in detail. Finally, an LED device was fabricated using a 460 nm blue chip, and the as-obtained far-red emitting LMGO:Mn⁴⁺,Dy³⁺ phosphors for Wedelia chinensis cultivation. As expected, the as-fabricated plant growth LED-treated Wedelia chinensis cultured in the artificial climate box with overhead LEDs demonstrated that after 28 days of irradiation, the average plant growth rate and the total chlorophyll content were better than those of specimens cultured using the commercial R-B LED lamps, indicating that the as-prepared phosphor could have a potential application in the agricultural industry.     

Photoluminescence studies of Ce3+ ion-doped BiPO4 phosphor and its photocatalytic activity

Ce³⁺ ion doped BiPO₄ phosphors were synthesized by co-precipitation method using ethylene glycol as capping agent. The prepared phosphors were characterized by XRD, SEM, FT-IR, UV-Vis, and PL spectroscopy techniques. The formation of monoclinic phase was confirmed from XRD and FT-IR studies. SEM study revealed the rice shape morphology of BiPO₄:Ce³⁺ (7at.%). In the photoluminescence analysis, a broad emission band extending in a wide wavelengths range with maxima around 419 and 470 nm was observed under excitation at 370 and 417 nm, respectively. These emission bands are originated from the electronic transitions, viz., 5d → ²F_5/2, ²F_7/2 of Ce³⁺ ion. The emission intensity was accentuated with the increase of Ce³⁺ ion till 7at.% and subsequently attenuated with further increase of Ce³⁺ ion concentration; which is due to the concentration quenching effect. The BiPO₄:Ce³⁺ (7at.%) sample was characterized for the feasibility of photocatalytic degradation of methylene blue under UV light irradiation and degradation of 90% of the dye was degraded within 120 minutes was observed. From the results, it is believed that the prepared BiPO₄:Ce³⁺ may have potential applications in solid state lighting as well as in photocatalysis for the degradation of organic dyes.     

Influence of Cr3+ on yellowish-green UC emission and energy transfer of Er3+/Cr3+/Yb3+ tri-doped zinc silicate glasses

In this paper, we study the influence of Cr³⁺ on yellowish-green upconversion (UC) emission and the energy transfer (ET) of Er³⁺/Cr³⁺/Yb³⁺ tri-doped in SiO₂–ZnO–Na₂O–La₂O₃ (SZNL) zinc silicate glasses under excitation of the 980 nm laser diode (LD). The influence of Cr³⁺ on enhancing the red UC emission of Er³⁺/Cr³⁺/Yb³⁺ tri-doped in SiO₂–ZnO–Na₂O–La₂O₃ zinc silicate glasses under the excitation of 980nm LD was also investigated. The ET processes between Yb³⁺, Cr^3+, and Er³⁺, together with the combination of Yb³⁺-Cr³⁺-Er³⁺, which led to the green UC emission intensity of Er³⁺/Cr³⁺/Yb³⁺ tri-doped in SiO₂–ZnO–Na₂O–La₂O₃ zinc silicate glasses bands centered at ~546 nm have been significantly enhanced. By increasing the concentration of Cr³⁺ from 0 up to 5 mol.%, we can locate the Commission Internationale de l'éclairage (CIE) 1931 (x; y) chromaticity coordinates for UC emissions of Er³⁺/Cr³⁺/Yb³⁺ tri-doped in the central position of the yellowish-green color region of CIE 1931 chromaticity diagram. Besides, the ET processes between the Yb³⁺, Cr³⁺, and Er³⁺ are also proposed and discussed.     

镁、钐和锆对AlF_3催化剂的乙炔气相氢氟化反应性能的影响

研究了Mg、Sm和Zr助剂对AlF_3催化剂的乙炔气相氢氟化合成氟乙烯反应性能的影响。通过XRD、NH_3-TPD和拉曼光谱对催化剂进行了表征。结果表明,添加Zr既能保持C_2H_2的高转化率,提高氟乙烯选择性,同时能降低积炭选择性;加入Mg或Sm助剂,均使C_2H_2转化率下降,Mg大幅度降低积炭选择性,Sm提高了氟乙烯选择性。助剂的加入,改变了催化剂表面酸性位的数量和性能,是影响催化剂性能的主要因素。     

水热法制备Y2O3:Eu3+微米棒及其荧光性能表征

利用水热法制备了Y2O3和Y2O3:Eu3+,探讨了反应温度、反应时间及氢氧化钠溶液浓度对产物晶型的影响,确定了生成较好晶型的反应条件为：反应温度180℃,反应时间24 h,氢氧化钠溶液浓度2 mol/L. 研究了Y3+和Eu3+的配比对Y2O3:Eu3+荧光性能的影响. 结果表明,当n(Y3+):n(Eu3+)的比例为100:5时,其荧光强度最佳. TEM分析表明,Y2O3:Eu3+粉末具有直径约0.2~0.6 mm、长度为几到十几微米的棒状结构.     

A novel pale-yellow Ba2ZnGe2O7:Bi3+ phosphor with site-selected excitation and small thermal quenching

A novel pale-yellow Ba₂ZnGe₂O₇:Bi³⁺ phosphor with site-selected excitation and small thermal quenching was synthesized by conventional solid-state sintering. The crystal structure and luminescence properties have been investigated in detail for the first time using XRD patterns, photoluminescence spectra, diffuse reflection spectra, decay curves, and temperature-dependent emission spectra. The results reveal that the excitation spectrum of Ba₂ZnGe₂O₇:Bi³⁺ phosphor locates in the near-ultraviolet region of 300-400 nm, and its emission shows an obvious site-selective excitation phenomenon since Bi³⁺ ions occupy two different crystallographic sites in the Ba₂ZnGe₂O₇ host. When excited under 360 nm, the phosphors show a pale-yellow emission in the range of 400-700 nm with the maximum peaking at 520 nm, while when excited under 316 nm, the phosphors show a blue emission in the range of 400-700 nm with the maximum peaking at 480 nm. In addition, the emission of Ba₂ZnGe₂O₇:Bi³⁺ can also be easily controlled by changing the Bi³⁺ concentration. The Ba₂ZnGe₂O₇:Bi³⁺ phosphor has small thermal quenching, and its emission intensity only decreases by 2% at 200°C. The results indicate that this novel pale-yellow Ba₂ZnGe₂O₇:Bi³⁺ phosphor could be conducive to the development of white light-emitting diodes.     

Tuning the luminescence properties of blue and far-red dual emitting Gd2MgTiO6: Bi3+, Cr3+ phosphor for LED plant lamp

Blue and far-red light play a key role in plant growth, so it is necessary to develop blue and far-red dual emitting phosphors. However, the match between phosphors and plant pigments is not satisfactory. In this work, we synthesized a series of blue and far-red dual emission Gd₂MgTiO₆: Bi³⁺, Cr³⁺ (GMTO: Bi³⁺, Cr³⁺) phosphors and discussed the luminescence performance. The blue emission at 430 nm is ascribed to ³P₁ → ¹S₀ transition of Bi³⁺ and the far-red emission is ascribed to ⁴T₂ → ⁴A₂ and ²E → ⁴A₂ transitions of Cr³⁺. Notably, because of the energy competition between Cr³⁺ ions and host materials, the luminescence tuning realized with the content of Cr³⁺ doping. In addition, an energy-transfer performance occurred from Bi³⁺ ions to Cr³⁺ ions and the photoluminescence intensity of Cr³⁺ can be enhanced by Bi³⁺. The pc-LEDs devices were synthesized by GMTO: Bi³⁺, Cr³⁺ phosphor, and ultraviolet (UV) chips. Finally, the emission of GMTO: Bi³⁺, Cr³⁺ phosphor matched well with the absorption spectra of plant pigments which indicated the potential applications in LED plant lamp.     

Sm3+掺杂GdVO4荧光材料的制备及其上转换发光性能

以水热法制备GdVO4:Sm3+上转换发光材料,表征了其形貌,考察了Sm3+掺杂量、焙烧温度及乙二胺四乙酸二钠(EDTA)掺杂量对材料上转换发光性能的影响. 结果表明,所制材料为四方晶系,在816 nm近红外光激发下,Sm3+掺杂量1.5%(mol)、焙烧温度800℃、EDTA:Sm3+(摩尔比)为1:1时,其上转换发光性能最好,发射峰位于565, 604, 647和706 nm处,分别归属于Sm3+的4G5/2→6HJ (量子数J=5/2, 7/2, 9/2, 11/2)电子跃迁,材料有可能用作LED灯荧光粉.     

Facile synthesis of the desired red phosphor Li2Ca2Mg2Si2N6:Eu2+ for high CRI white LEDs and plant growth LED device

The red emission with suitable peak wavelength and narrow band is acutely required for high color rendering index (CRI) white LEDs without at the cost of the luminous efficacy. Herein, the Li₂Ca₂Mg₂Si₂N₆:Eu²⁺ red phosphor was prepared with facile solid-state method using Ca₃N₂, Mg₃N₂, Si₃N₄, Li₃N, and Eu₂O₃ as the safety raw materials under atmospheric pressure for the first time, which shows red emission peaking at 638 nm with full width at half maximum (FWHM) of 62 nm under blue light irradiation and becomes the desired red phosphor to realize the balance between luminous efficacy and high CRI in white LEDs. The morphology, structure, luminescence properties, thermal quenching behavior, and chromaticity stability of the Li₂Ca₂Mg₂Si₂N₆:Eu²⁺ phosphor are investigated in detail. Concentration quenching occurs when the Eu²⁺ content exceeds 1.0 mol%, whereas high-temperature photoluminescent measurements show a 32% drop from the room-temperature efficiency at 423 K. In view of the excellent luminescence performances of Li₂Ca₂Mg₂Si₂N₆:Eu²⁺ phosphor, a white LEDs with CRI of 91 as a proof-of-concept experiment was fabricated by coating the title phosphor with Y₃Al₅O₁₂:Ce³⁺ on a blue LED chip. In addition, the potential application of the title phosphor in plant growth LED device was also demonstrated. All the results indicate that Li₂Ca₂Mg₂Si₂N₆:Eu²⁺ is a promising red-emitting phosphor for blue LED-based high CRI white LEDs and plant growth lighting sources.     

NaY(WO4)2:Dy3+荧光粉的制备及其上转换发光性能

利用水热法合成了NaY(WO4)2:Dy3+上转换荧光粉. 通过XRD、SEM表征该荧光粉结构和形貌. 探讨了Dy3+浓度、pH值、反应温度及焙烧温度对NaY(WO4)2:Dy3+晶体结构、形貌及发光性能的影响,得到在Dy3+浓度为0.5%,pH=8,反应温度180℃,800℃焙烧条件下的样品具有最佳上转换发光性能. 利用776 nm近红外光激发NaY(WO4)2:Dy3+,观察到480 nm处的蓝光发射峰以及577 nm处的黄光发射峰. 其中蓝光来自Dy3+离子的4F9/2→6H15/2跃迁,黄光由Dy3+离子4F9/2→6H13/2跃迁产生.     

Wide‐range thermometry based on green up‐conversion luminescence of K3LuF6:Yb3+/Er3+ bulk oxyfluoride glass ceramics

Yb³⁺/Er³⁺ ions codoped bulk glass ceramics (GC) with embedded monoclinic K₃LuF₆ nanocrystals are reported for potential temperature‐sensing application by using the fluorescence intensity ratio method. Such GC with good transparency and enhanced up‐conversion were prepared by the simple conversional melt‐quenching method and subsequent annealing process. Optical, structural, and temperature‐sensing up‐conversion properties were characterized systematically. Optical spectroscopy analysis confirms the incorporation of Yb³⁺/Er³⁺ into the K₃LuF₆ crystalline lattice, resulting in enhanced up‐conversion luminescence. Compared to other Er³⁺‐doped typical systems, Er³⁺ ions in K₃LuF₆ GC present large energy gap (870 cm^?1) and high relative sensitivity (37.6 × 10^?4 K^?1 at 625 K), revealing that K₃LuF₆:Yb³⁺/Er³⁺ GC can be excellent candidates for optical thermometers.     

Optimization of Ce3+ concentration and Y4MgSi3O13 phase in Mg2+-Si4+ Co-doped Ce: YAG ceramic phosphors

As a promising replacement for nitride red phosphors, Ce: Y₃(Mg_1.8Al_1.4Si_1.8)O₁₂ (Ce: YMASG) ceramic phosphors have attracted significant attention recently for their advantages in inorganic encapsulation and massive red-shifting of Ce³⁺ emission. In this work, Ce: YMASG with different doping concentrations of Ce³⁺ and Al₂O₃, was fabricated by vacuum sintering to investigate its effects on the elimination of the impurity phase and the enhancement of the luminescent properties of white light-emitting diodes (w-LEDs). It was discovered that the emission wavelength redshifts from 592 to 606 nm as the Ce³⁺ concentration increases, while at 450 K, the emission intensity deteriorates from 0.47 to 0.36 of its initial value. The Rietveld analysis revealed the presence of an impurity phase of Y₄MgSi₃O₁₃ with a concentration of 17.021 wt% in Ce: YMASG. With the introduction of Al₂O₃, the impurity phase was eliminated from the matrix completely, the emission peak shifted to a shorter wavelength, and the thermal stability was greatly improved. When the correlated color temperature was controlled at around 3000 K in the packaged w-LEDs, the commission international de l'éclairage (CIE) chromaticity coordinates shifted toward the bottom left corner of the diagram with increasing concentration of Ce³⁺. Conversely, the luminous efficiency (LE) increased from 36 lm/W to 58.6 lm/W as the concentration of Al₂O₃ increased from 0 to 10 wt%, which demonstrated the application prospect of the fabricated phosphor in warm w-LEDs.