Electrospun green-emitting La2O2CO3:Tb3+ nanofibers and La2O2CO3:Tb3+/Eu3+ nanofibers with white-light emission and color-tuned photoluminescence

Coordination-driven in-situ controlled synthesis of cellulose-based fluorescent composite with tunable color for decoration, anti-counterfeiting, and accurate color recognition

Fluorescent composites have widespread applications in many aspects. Wood-derived cellulose is a renewable, easily processed and biodegradable, and cellulose-based fluorescent composites are highly favored for in different fields. However, the existing cellulose-based fluorescent composites still have many urgent problems to be solved, such as unstable luminescence properties and easy shedding of luminescent substances, and the development of their practical applications is still a formidable challenge. Herein, a green and mild strategy for the in-situ controllable synthesis of cellulose-based fluorescent composites membrane (CFM) was developed. Firstly, delignified wood (DW) was modified with citric acid, and then lanthanide ions were introduced on modified DW through coordinated covalent bonds. Additionally, the luminescence mechanism of CFM is proposed. CFMs show adjustable color for decorative and light conversion and can be accurately identified for data protection, which increases the high value-added of cellulose-based composites. The stable luminescent properties were maintained after sonication for 30 min or solvent immersion for three months. Therefore, this work presents a new approach for the synthesis of CFM, which provides an environment-friendly strategy for manufacturing cellulose-based fluorescent materials, which is significant for the subsequent development of environment-friendly composites for anti-counterfeiting and decorative applications.

Novel green/red oxyfluoride phosphors with excellent optical properties for near-UV excited white light emitting diode

Novel eye-sensitive Ba3Nb2O2F12(H2O)2:Tb3+ green and Ba3Nb2O2F12(H2O)2:Mn4+ red oxyfluoride phosphors with extremely strong absorption in the UV region were designed and synthesized by simple co-precipitation strategy. Particularly, Tb3+ ions were doped in this matrix for the first time, which greatly improves their absorption efficiency in the near ultraviolet region (367 nm) and emits sharp green light (544 nm). In addition, the Ba3Nb2O2F12(H2O)2:Mn4+ red phosphors have strong zero phonon line (ZPL) emission at 625 nm, which is conducive to improving the sensitivity of human eye and color purity. Meanwhile, the optical properties of the red phosphor are significantly enhanced via doping K+ cations as charge compensators. Crystal field environment and nephelauxetic effect of the as-prepared phosphors before and after K+ cation doping were systematically analyzed. Moreover, these synthesized red/green phosphors have good thermal stability and moisture resistance. Remarkably, the as-prepared Ba3Nb2O2F12(H2O)2:5%Mn4+ or K0.9Ba2.1Nb2O2F12(H2O)2:5%Mn4+ red phosphors can be directly mixed with the as-synthesized Ba3Nb2O2F12(H2O)2:13%Tb3+ green phosphor coating on 365 nm near-ultraviolet LED chip to package WLED devices with excellent electroluminescence performance. These findings are conducive to opening an avenue for screening the unique structure of optical materials.

NaLuF4:RE3+ (Dy3+, Tb3+, Eu3+, Tm3+): controllable morphology, multicolor light

A series of emission-tunable NaLuF4:RE3+ (RE = Dy, Tb, Eu, Tm) phosphors were firstly synthesized by a glycine assisted one-step hydrothermal process. The structure and morphology were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results revealed that the samples were Na5Lu9F32, LuF3 and NaLuF4 and the size and shape of the products could be tuned just by adjusting the pH values of the initial reaction solutions or by adjusting the RE3+/NaF ratio or RE3+/NaBF4 ratio. The morphologies for the products include irregular particles, irregular blocks, octahedral shapes, hexagons, or micron sized hexagonal prisms. Furthermore, the photoluminescence properties of NaLuF4:Dy3+,Tb3+, NaLuF4:Tb3+,Eu3+, NaLuF4:Dy3+,Eu3+ and NaLuF4:Tm3+,Dy3+ were investigated in detail. Additionally, when co-doping Dy3+ with Tb3+ or Eu3+ or co-doping Tb3+with Eu3+ or co-doping Tm3+ with Dy3+ ions in the single component, colorful emission can be obtained by giving abundant blue, green, yellow, orange, and especially white-light-emission. All these properties indicate that the developed phosphor may potentially be used as single-component multicolor-emitting phosphors.

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.

Wire-in-tube nanofiber as one side to construct specific-shaped Janus nanofiber with improved upconversion luminescence and tunable magnetism

It is an important strategy to rationally design and construct specific-shaped microscopic nanostructures for developing poly-functional nanomaterials for different advanced applications. In this work, a novel technique combining a parallel electrospinning with a subsequent bi-crucible fluorination is advanced and utilized to facilely synthesize a brand-new peculiar one-dimensional (1D) wire-in-tube nanofiber//nanofiber shaped Janus nanofiber (WJNF) to refrain from usual complicated preparation procedures. Partition of four independent domains in the peculiar-structured Janus nanofiber is microscopically realized. The Janus nanofiber with four microscopic partitions can be applied to assemble various functions to avoid adverse mutual impacts among functions to realize multi-functionalization of the materials. As a case study, [YF3:Yb3+, Er3+@SiO2]//CoFe2O4 WJNFs with synchronous excellent upconversion luminescence and tunable magnetism are designed and constructed by the above technique. One side of the WJNF is composed of YF3:Yb3+, Er3+@SiO2 wire-in-tube nanofiber with YF3:Yb3+, Er3+ nanofiber as core layer and SiO2 as shell layer, and the other side is composed of CoFe2O4 magnetic nanofiber. YF3:Yb3+, Er3+ green upconversion luminescent nanofiber is completely separated from CoFe2O4 to fully avoid the weakening of luminescent intensity caused by the direct contact between luminescent and magnetic substances, and thus the luminescent intensity of [YF3:Yb3+, Er3+@SiO2]//CoFe2O4 WJNFs is apparently enhanced. Up-conversion luminescent intensity and magnetism of the WJNFs are modulated by tuning the contents of CoFe2O4. With the increase of CoFe2O4 content, the saturation magnetization of the WJNFs increases from 3.91 to 12.90 emu·g-1, revealing the tunable magnetism of the product. The formation mechanism of WJNFs is advanced, and a corresponding facile construction technique is established to shun complicated process, which provides theoretical guidance and technical support for the design and preparation of other poly-functional nanomaterials.