Synthesis Design and Properties of Ca5(BO3)3F: Bi3+/Eu3+: Insight into Luminescence, Temperature, and Pressure Sensing

Nowadays, the utilization of noncontact temperature and pressure sensing is experiencing growing popularity. In this work, Bi3+, Eu3+-doped Ca5(BO3)3F (CBOF) phosphors were synthesized via an ionic liquid-assisted electrospinning approach. The effect of molecular weight of polyvinylpyrrolidone on the morphology of CBOF was investigated, and a comprehensive analysis of its formation mechanism was presented. The luminescence properties of CBOF: Bi3+, Eu3+ were studied systematically. The temperature-dependent emission of CBOF: Bi3+, Eu3+ phosphor was discussed, and it displayed thermal sensitivity, which can be attributed to the distinct thermal response emission behaviors of Bi3+ and Eu3+. The investigation of the pressure-dependent emission behavior of the CBOF: Bi3+ phosphor revealed an anomalous phenomenon: with the increase of pressure, the emission peak showed a trend of first a blue shift and then a red shift. This anomaly was discussed in detail. The phosphor exhibits visual color change (blue to cyan), remarkable pressure sensitivity (4.76 nm/GPa), and a high upper pressure limit (24.2 GPa), indicating its potential use as an optical pressure sensor. Consequently, this study presents an innovative synthetic approach for fabricating CBOF, presenting a bifunctional material with promising prospects in the fields of temperature and pressure sensing.

Ba3Lu(BO3)3:Ce3+,Tb3+/Mn2+: Dual-Functional Material for WLEDs and Optical Pressure Sensing

Ba3Lu(BO3)3(BLB):Ce3+,Tb3+/Mn2+ phosphors were designed to explore effective and multifunctional applications. Under the excitation of near-ultraviolet (n-UV) light, the BLB:Ce3+ phosphor showed broad-band blue emission. After codoping with Mn2+ ions, the single-phase white light phosphor is achieved through the energy transfer (ET) between Ce3+ and Mn2+. In addition, thermal stability is significantly enhanced by the addition of Tb3+ (BLB:0.02Ce3+,0.20Tb3+) compared to that codoped with Mn2+ (BLB:0.02Ce3+,0.10Mn2+). The light-emitting diode (LED) device with warm white light emission is fabricated with UV-chip-coated BLB:0.02Ce3+,0.05Tb3+ and Sr2Si5N8:Eu2+ phosphors, showing a good potential application value for LEDs. Additionally, the spectral properties of borate-based phosphors (BLB:0.02Ce3+) under high pressure were studied for the first time. Surprisingly, the change of pressure enabled the emission peak of BLB:0.02Ce3+ to be tuned from 485 to 552 nm, and dλ/dP is 3.51 nm GPa-1. The color changes from blue to yellow with an increase of pressure. Compared with the reported data, the pressure-sensing sensitivity based on the central peak shift in this work is the highest in all Ce3+ single-doped samples. In addition, the emitting color and intensity were gradually regained after decompression. The intensity can reach 80% of the initial intensity. All data demonstrate that the BLB:0.02Ce3+ phosphor has the potential to be utilized as an optical pressure sensor due to the high-pressure sensitivity and visible color tuning.

Pressure-Induced Remarkable Spectral Red-Shift in Mn2+ -Activated NaY9 (SiO4 )6 O2 Red-Emitting Phosphors for High-Sensitive Optical Manometry

To settle the low sensitivity of luminescent manometers, the Mn2+ -activated NaY9 (SiO4 )6 O2 red-emitting phosphors with splendid pressure sensing performances are developed. Excited by 408 nm, the resulting products emit bright red emission originating from 4 T1 (4 G) → 6 A1 transition of Mn2+ , in which the optimal concentration of the activator ion is ≈1 mol%. Moreover, the admirable thermal stability of the developed phosphors is studied and confirmed by the temperature-dependent emission spectra, based on which the activation energy is derived to be 0.275 eV. By analyzing the pressure-dependent Raman spectra, the structural stability of the synthesized compounds at extreme conditions is verified. Furthermore, the designed phosphors exhibit remarkable spectral red-shift at elevated pressure. Especially, as pressure increases from 0.75 to 7.16 GPa, the emission band centroid shifts from 617.2 to 663.4 nm, resulting in a high sensitivity (dλ/dP) of 7.00 nm GPa-1 , whereas the full width at half maximum (FWHM) increases from 83.0 to 110.6 nm, leading to the ultra-high sensitivity (dFWHM/dP) of 10.13 nm GPa-1 . These achievements manifest that the designed red-emitting phosphors are appropriate for ultrasensitive optical manometry. More importantly, the developed manometer is a current global leader in sensitivity, when operating in the band-width mode, that is, FWHM.

Highly-efficient Eu2+-activated Sr8Si4O12Cl8 cyan-emitting phosphors with zero-thermal quenching luminescence for versatile applications

To settle the problem of phosphors with unsatisfactory luminescence efficiency and serious thermal quenching, Eu²⁺-activated Sr₈Si₄O₁₂Cl₈ cyan-emitting phosphors were designed. Excited at 387 nm, a dazzling cyan emission located at 492 nm is observed in the resultant phosphors and its maximum intensity is obtained when the Eu²⁺ content is 4 mol%. Moreover, the zero-thermal quenching luminescence, even when the temperature is 503 K, the integrated emission intensity still maintains 106% of its starting value at 303 K, is realized in resultant phosphors because of the efficient energy transfer from defect levels to Eu²⁺, which is confirmed by the thermoluminescence spectrum. The electroluminescence spectrum of the packaged white light-emitting diode (white-LED) is detected and it is found to possess a high color rendering index (91.0), low correlated color temperature (4875 K) and a superior luminous efficiency (68.7 lm W^-1), implying that the developed phosphors can be adopted as cyan-emitting components to fulfill the cyan gap and realize a full spectrum white-LED. Furthermore, the cathodoluminescence (CL) performance of samples is also studied, in which its CL emission intensity is greatly impacted by the accelerating voltage and the filament current. Additionally, using the synthesized phosphors, various types of patterns are designed for use in information encryption. These achievements reveal that the Eu²⁺-activated Sr₈Si₄O₁₂Cl₈ phosphors are multifunctional cyan-emitting candidates for full spectrum white-LED, field-emission display and anti-counterfeiting applications.

Visible-near-Infrared Light-Driven Photocatalytic Characteristics of Er3+/Yb3+-Codoped BiOBr Upconverting Microparticles for Tetracycline Degradation

To settle the unsatisfying efficiency and insufficient light harvesting ability of photocatalysts, we report on the development of Er³⁺/Yb³⁺-codoped BiOBr (BiOBr:Er³⁺/xYb³⁺) microparticles that were synthesized by a rational high-temperature solid-state reaction method. The prepared microcrystals exhibit high visible upconversion (UC) emissions with maximum intensities at x = 0.01 when excited by a 980 nm laser. Remarkably, the corresponding UC emission process is attributed to a two-photon absorption route. Furthermore, the photocatalytic activities of as-synthesized compounds were further evaluated through analyzing the visible-near-infrared light-triggered tetracycline degradation. Compared with BiOBr:Er³⁺ microparticles, BiOBr:Er³⁺/xYb³⁺ microparticles present superior photocatalytic properties and the optimal status is achieved when x = 0.05, in which h⁺, ·O₂^-, and ·OH active species contribute to the photocatalytic mechanism. Additionally, the designed microparticles exhibit better photocatalytic abilities than previously reported photocatalysts (i.e., TiO₂, SnO₂) upon full-spectrum light irradiation. These results reveal that Yb³⁺ codoping is able to not only enhance the UC emission properties of BiOBr:Er³⁺ microparticles but also reinforce their photocatalytic activities. Our findings may put forward a facile strategy to regulate the photodegradation capacity of photcatalysts.

Improving the luminescence property of the novel yellow-emitting phosphor SrLa2Sc2O7:Bi3+ with charge compensators (Li+, Na+, K+) and its application in NUV-based white LEDs

In this work, a novel yellow-emitting phosphor SrLa2Sc2O7:Bi3+ was synthesized by high temperature solid-state method, ranging from 400 nm to 800 nm under near-ultraviolet (NUV) excitation and the full width at half maximum (FWHM) of up to 180 nm.

Efficient violet-light-excitable blue-cyan phosphor for full-spectrum lighting

In order to realize the full-spectrum lighting, excellent blue-cyan phosphors which can be excited by violet LED chips are particularly important to compensate the spectral cyan gap. Herein, we report...