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To achieve a selective degradation of pollutants in a water body, 3D/1D magnetic molecularly imprinted fibers Fe3O4@TiO2/TC-TiO2/SiO2 were fabricated by an electrospinning method. The molecularly imprinted layer was successfully prepared by a direct imprinting method using TiO2 as a functional monomer. Fe3O4 facilitates the catalyst recovery and light utilization. The as-prepared fibrous photocatalyst has a large specific surface area of 132.4 m2/g. The successful generation of imprinted sites was proven by various characterizations. The weak interaction between the inorganic functional monomer and tetracycline (TC) was determined to be van der Waals force and hydrogen bonds by the IGMH isosurface theory. The construction of the 3D/1D homojunction of molecularly imprinted materials is beneficial to charge transfer. The as-prepared photocatalyst exhibits a high selectivity coefficient α = 737.38 competing with RhB. The TC removal efficiency reached 100% within only 20 min. In addition, the possible degradation pathway and the degradation mechanism are reasonably proposed. This work not only provides an in-depth mechanism of the weak interaction between the inorganic molecularly imprinted functional monomer and pollutant molecules but also offers new thoughts on the fabrication of photocatalysts for the effective and selective treatment of pollutants in water bodies.
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How to effectively improve energy transfer efficiency and luminous intensity inspired us to synthesize a series of SiO2:x%Tb3+@Gd2O3:y%Eu3+ samples, study their luminescence properties and interfacial energy transfer (IET), and compare with SiO2:x%Eu3+@Gd2O3:y%Tb3+. The results show that SiO2:x%Tb3+@Gd2O3:y%Eu3+ can exhibit adjustable multicolor luminescence from red to green at different concentrations of Eu3+ and Tb3+ or under different excitation wavelengths, and there exists efficient IET from Tb3+ to Eu3+ in SiO2:x%Tb3+@Gd2O3:y%Eu3+ and SiO2:x%Eu3+@Gd2O3:y%Tb3+, which improves the energy transfer efficiency and luminous intensity. In addition, the luminescence properties are different between SiO2:3%Tb3+@Gd2O3:3%Eu3+ and SiO2:3%Eu3+@Gd2O3:3%Tb3+, and the energy transfer efficiency of Tb3+ â Eu3+ in SiO2:3%Tb3+@Gd2O3:3%Eu3+ is obviously higher than that in SiO2:3%Eu3+@Gd2O3:3%Tb3+. The present study not only developed a kind of multicolor luminescent phosphor but also offered an important new strategy for improving the energy transfer efficiency and luminescent intensity.
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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.
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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.
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Optical pressure sensing by phosphors is a growing area of research. However, the main pressure measurement methods rely on the movement of the central peak position, which has significant drawbacks for practical applications. This paper demonstrates the feasibility of using the fluorescence intensity ratio (FIR) of different emission peaks for pressure sensing. The FIR (IBi3+/ILn3+) values of the synthesized YNbO4:Bi3+/Ln3+ (Ln = Eu or Sm) phosphors are all first-order exponentially related to pressure, and YNbO4:Bi3+/Ln3+ (Ln = Eu or Sm) phosphors have high pressure-sensing sensitivities (Sp and Spr), which are 6 times higher than those from our previously reported work. In addition, the changes in FIR values during the decompression process were also calculated, and the trend was similar to that during the compression process. The YNbO4:Bi3+,Eu3+ phosphor has better pressure recovery performance. In summary, the YNbO4:Bi3+/Ln3+ (Ln = Eu or Sm) phosphors reported in this paper are expected to be applied in the field of optical pressure sensing, and this study provides a new approach and perspective for designing new phosphors for pressure measurement.
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A novel green-light-emitting silicon-based oxynitride phosphor Ca4Y3Si7O15N5:Eu2+ with low thermal quenching and ideal pressure sensitivity is reported. The Ca3.99Y3Si7O15N5:0.01Eu2+ phosphor can be efficiently excited by 345 nm ultraviolet light and shows very low thermal quenching (integrated and peak emission intensities at 373 and 423 K were 96.17, 95.86, and 92.73, 90.66% of those at 298 K, respectively). The correlation between high thermal stability and structural rigidity is investigated in detail. The white-light-emitting diode (W-LED) is assembled by depositing the obtained green-light-emitting phosphor Ca3.99Y3Si7O15N5:0.01Eu2+ and commercial phosphors on a ultraviolet (UV)-emitting chip (λ = 365 nm). The CIE color coordinates, color rendering index (Ra), and corrected color temperature (CCT) of the obtained W-LED are (0.3724, 0.4156), 92.9, and 4806 K, respectively. In addition, when subjected to in situ high-pressure fluorescence spectroscopy, the phosphor exhibits an evident red shift of 40 nm with an increase in pressure from 0.2 to 32.1 GPa. The phosphor has the advantage of high-pressure sensitivity (dλ/dP = 1.13 nm GPa-1) and visualization with pressure changes. The possible reasons and mechanisms are deeply discussed in detail. Based on the above advantages, Ca3.99Y3Si7O15N5:0.01Eu2+ phosphor is expected to have potential applications in W-LEDs and optical pressure sensing.
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Fructose 1, 6-diphosphate (FDP) is an endogenous intermediate in the glycolytic pathway, as well as an allosteric activator of phosphofructokinase (PFK). Based on the role in promoting glycolysis, FDP has been widely used as a therapeutic agent for mitigating the damage of endotoxemia and ischemia/reperfusion in clinical practice. However, the effect of exogenous FDP-induced glycolysis activation on insect carbohydrate metabolism and chitin synthesis remains largely unclear. Here, we investigated for the first time the effects of FDP-Na, an allosteric activator of PFK, on the growth and development of Hyphantria cunea larvae, a serious defoliator in agriculture and forestry, especially on glycolysis and chitin synthesis. The results showed that FDP-Na significantly restrained the growth and development of H. cunea larvae and resulted in larval lethality. After treatment with FDP-Na, hexokinase (HK), phosphofructokinase (PFK) and pyruvate kinase (PK) were significantly activated, and HcHK2, HcPFK, HcPK were dramatically upregulated, which suggested that FDP-Na enhanced glycolysis in H. cunea larvae. Meanwhile, FDP-Na also distinctly impacted chitin biosynthesis by disturbing transcriptions of genes in the chitin synthesis pathway, resulting in changes of chitin contents in the midgut and epidermis of H. cunea larvae. Therefore, we considered that FDP-Na caused the growth and development arrest, and impacted chitin biosynthesis, probably by disturbing in vivo glycolysis and carbohydrate metabolism in H. cunea larvae. The findings provide a new perspective on the mechanism by which glycolysis regulates insect growth and development, and lay the foundation for exploring the potential application of glycolysis activators in pest control as well.
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Difosfatos , Mariposas , Animais , Larva , Glicólise , Fosfofrutoquinases , Quitina/farmacologiaRESUMO
The upconversion (UC) emission intensity of Ln3+-doped CaF2 nanomaterials is not ideal, which limits their application in some advanced scientific fields. Hence, it is extremely imperative to enhance the emission intensity of UC nanocrystals. In this work, an ionic-liquid-assisted hydrothermal method based on an ethylene glycol (EG) and ionic liquid (IL) two-phase system was used to synthesize CaF2 doped with Yb3+ and Ho3+. The influence of the amount of IL and the reaction time as well as the concentration of Gd3+ doping on morphology and size was studied in detail, and the growth mechanism was proposed. Green UC luminescence materials were obtained through co-doping Yb3+ and Ho3+ ions. Furthermore, the luminescence of UC was increased monotonically with the introduction of Gd3+ ions. The effect mechanism of Gd3+ doping on the UC luminescence was put forward, which might provide a new method for the promotion of UC luminescence. In addition, the temperature sensing of CaF2: Yb3+/Ho3+/Gd3+ was investigated, which demonstrated that the phosphor has a potential application prospect in thermal sensing. Meanwhile, CaF2: Yb3+/Ho3+/Gd3+ also exhibited a paramagnetic property at room temperature. Therefore, these multifunctional nanocrystals may have prospective applications in optical bioimaging, magnetic resonance imaging, and temperature sensing.
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Líquidos Iônicos , Nanopartículas , Cristalização , Etilenoglicóis , Luminescência , Nanopartículas/química , TemperaturaRESUMO
This work proposes a new type of Eu2+, Ce3+, Mn2+ codoped strategy that can be adapted to both ultraviolet (UV) and blue chips to achieve high-quality white light illumination. Primarily, the target sample was confirmed by X-ray diffraction (XRD) and Rietveld refinement, and the surface morphology and element distribution were observed by scanning electron microscopy (SEM). Second, the energy transfer behavior and mechanism were determined by studying double-doped samples. Lu2Mg2Al2Si2O12: Eu2+,Ce3+ (LMAS: Eu2+,Ce3+) can realize an emission color adjustment from blue to yellow. The emission color of LMAS: Ce3+,Mn2+ can be adjusted from light yellow to orange yellow. Afterward, the triple-doped sample exhibits full-spectrum emission under the excitation at 365 nm, and yellow emission under the excitation at 450 nm. When combined with a 365 nm chip, the obtained light-emitting diode (LED) devices can achieve warm white light with a color rendering index (Ra) of 96.6, light emission (LE) of 1.79 lm/W, and correlated color temperature (CCT) of 4874 K. When this phosphor was combined with a 460 nm chip, cold white light with Ra = 70, LE = 13.57 lm/W, and CCT = 5782 K can be achieved. Finally, according to the properties of the phosphor, a conceptual diagram of a new type parallel device was designed, which can easily and effectively realize the conversion of cold and warm white light. This work provides a new idea for the design of single-substrate white light phosphor and proposes a new parallel device concept, which is expected to be applied in the field of lighting.
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In this work, GdOF:RE3+ (RE = Eu, Yb, and Er) phosphors with high thermally stable luminescence were reported, which were synthesized by an ionic liquid-assisted two-phase system and subsequent calcination technique for the first time. Nanodisks, nanorod aggregates, nanoneedles, and stubby nanorods were obtained by simply regulating the pH value. The luminescent properties of precursors and products were discussed in detail. By carefully adjusting the calcination temperature and the pH value of the initial system, pure red emission was achieved in both GdOF:Eu3+ and GdOF:Yb3+, Er3+ phosphors. The reason for distinct luminescent properties of different products was discussed from various perspectives. Moreover, the temperature-dependent spectra were measured and the GdOF:Eu3+ and GdOF:Yb3+, Er3+ products both exhibited outstanding thermal stability. In addition, the as-prepared nanomaterials presented paramagnetic properties, indicating their potential application in both field-emission displays and magnetic resonance imaging technology.
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Metformin, considered to be a potent AMPK activator, is widely used for clinical therapy of cancer and diabetes due to its distinct function in regulating cell energy balance and body metabolism. However, the effect of metformin-induced AMPK activation on the growth and development of insects remains largely unknown. In the present study, we focused on the role of metformin in regulating the growth and development of Hyphantria cunea, a notorious defoliator in the forestry. Firstly, we obtained the complete coding sequences of HcAMPKα2, HcAMPKß1, HcAMPKγ2 from H. cunea, which encoded a protein of 512, 281, and 680 amino acids respectively. Furthermore, the phylogenetic analysis revealed that these three subunits were highly homologous with the AMPK subunits from other lepidopteran species. According to the bioassay, we found metformin remarkably restrained the growth and development of H. cunea larvae, and caused molting delayed and body weight reduced. In addition, expressions of HcAMPKα2, HcAMPKß1, and HcAMPKγ2 were upregulated 3.30-, 5.93- and 5.92-folds at 24 h after treatment, confirming that metformin activated AMPK signaling at the transcriptional level in H. cunea larvae. Conversely, the expressions of two vital Halloween genes (HcCYP306A1 and HcCYP314A1) in the 20E synthesis pathway were remarkably suppressed by metformin. Thus, we presumed that metformin delayed larval molting probably by impeding 20E synthesis in the H. cunea larvae. Finally, we found that metformin accelerated glycogen breakdown, elevated in vivo trehalose level, promoted chitin synthesis, and upregulated transcriptions of the genes in chitin synthesis pathway. Taken together, the findings provide a new insight into the molecular mechanisms by which AMPK regulates carbohydrate metabolism and chitin synthesis in insects.
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Metformina , Mariposas , Proteínas Quinases Ativadas por AMP/genética , Proteínas Quinases Ativadas por AMP/metabolismo , Animais , Quitina/metabolismo , Larva/metabolismo , Metformina/metabolismo , Metformina/farmacologia , Muda , Mariposas/genética , FilogeniaRESUMO
Color-tunable phosphors can be obtained through codoping strategies and energy transfer regulation. Ce3+ and Eu2+ are the most common and effective activator ions used in phosphor materials. However, the energy transfer from Eu2+ to Ce3+ is rarely reported. In this work, Y2Mg2Al2Si2O12(YMAS):Eu2+,Ce3+ phosphors were successfully synthesized, which was confirmed by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Rietveld refinement, scanning electron microscopy (SEM) and element mapping images, and spectral information. The luminescent color of YMAS:Eu2+,Ce3+ phosphors could be tuned from blue to cyan to light green to yellow-green and finally to green-yellow, which was achieved by adjusting the energy transfer between different dopants. The energy transfer from Eu2+ to Ce3+ was confirmed by photoluminescence spectra and fluorescence decay curves. Within the experimental gradient, the energy transfer efficiency could reach up to 48%. At 373 K, the Y1.99Mg1.99Al2Si2O12:0.01Eu2+,0.01Ce3+ (YMAS:0.01Eu2+,0.01Ce3+) phosphor exhibited a total integral emission loss of only 8%, and the emission peak intensity decreased to 95%, indicating the excellent thermal stability. The white light-emitting diode (WLED) fabricated by the YMAS:0.01Eu2+,0.01Ce3+ phosphor has the same level correlated color temperature (CCT = 5841 K), greatly improved color rendering index (Ra = 87.8), and higher quality white light color (CIE = (0.3258, 0.3214)) than the WLED made by the YMAS:0.01Eu2+ phosphor, indicating that the performance of the phosphor was significantly improved by introducing Ce3+. This work provides an effective guide for the design and development of highly efficient color-tunable phosphors involving energy transfer from Eu2+ to Ce3+ in some specific materials, such as garnet structures.
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Uniform and well-dispersed SiO2:x%Tb3+@Lu2O3:y%Eu3+ core-shell spherical phosphors were synthesized via a solvothermal method followed by a subsequent calcination process. The structure, phase composition, and morphology of the samples were studied by X-ray diffraction (XRD), thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FT-IR), field emission scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The results showed that the Lu2O3:Eu3+ layer was evenly coated on the surface of SiO2:Tb3+ spheres and the shell thickness was about 45-65 nm. The PL spectra and fluorescence lifetimes of the samples were further studied. It was proved that the multicolor luminescence of the samples could be realized by changing the doping concentration ratio of Eu3+ or by changing the excitation wavelengths. Compared with SiO2@Lu2O3:3%Tb3+,6%Eu3+, SiO2:3%Tb3+@Lu2O3:6%Eu3+ showed stronger luminescence intensity, longer fluorescence lifetime, and higher energy transfer efficiency, which was attributed to the effective interfacial energy transfer, and the interfacial energy transfer mechanism from Tb3+ to Eu3+ was a dipole-dipole interaction mechanism. The XPS results indicated that the sample contained a high content of Si-O-Lu bonds, which proved that there was a strong interaction between the SiO2 core and the Lu2O3 shell, making the interfacial energy transfer possible. These results provided a new idea for luminescence enhancement and multicolor luminescence.
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The strategy of using a combination of scaffold-based physical and biochemical cues to repair spinal cord injury (SCI) has shown promising results. However, integrating conductivity and neurotrophins into a scaffold that recreates the electrophysiologic and nutritional microenvironment of the spinal cord (SC) remains challenging. In this study we investigated the therapeutic potential of a soft thermo-sensitive polymer electroactive hydrogel (TPEH) loaded with nerve growth factor (NGF) combined with functional electrical stimulation (ES) for the treatment of SCI. The developed hydrogel exhibits outstanding electrical conductance upon ES, with continuous release of NGF for at least 24 days. In cultured nerve cells, TPEH loaded with NGF promoted the neuronal differentiation of neural stem cells and axonal growth, an effect that was potentiated by ES. In a rat model of SCI, TPEH combined with NGF and ES stimulated endogenous neurogenesis and improved motor function. These results indicate that the TPEH scaffold that combines ES and biochemical cues can effectively promote SC tissue repair.
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Estimulação Elétrica/métodos , Hidrogéis/uso terapêutico , Traumatismos da Medula Espinal/terapia , Regeneração da Medula Espinal/efeitos dos fármacos , Animais , Diferenciação Celular/efeitos dos fármacos , Células Cultivadas , Hidrogéis/química , Fator de Crescimento Neural , Células-Tronco Neurais/efeitos dos fármacos , Neurogênese/efeitos dos fármacos , Ratos , Ratos Sprague-Dawley , Alicerces TeciduaisRESUMO
As a typical glycolytic inhibitor, 3-bromopyruvate (3-BrPA) has been extensively studied in cancer therapy in recent decades. However, few studies focused on 3-BrPA in regulating the growth and development of insects, and the relationship and regulatory mechanism between glycolysis and chitin biosynthesis remain largely unknown. The Hyphantria cunea, named fall webworm, is a notorious defoliator, which caused a huge economic loss to agriculture and forestry. Here, we investigated the effects of 3-BrPA on the growth and development, glycolysis, carbohydrate homeostasis, as well as chitin synthesis in H. cunea larvae. To elucidate the action mechanism of 3-BrPA on H. cunea will provide a new insight for the control of this pest. The results showed that 3-BrPA dramatically restrained the growth and development of H. cunea larvae and resulted in larval lethality. Meanwhile, we confirmed that 3-BrPA caused a significant decrease in carbohydrate, adenosine triphosphate (ATP), pyruvic acid (PA), and triglyceride (TG) levels by inhibiting glycolysis in H. cunea larvae. Further studies indicated that 3-BrPA significantly affected the activities of hexokinase (HK), phosphofructokinase (PFK), pyruvate kinase (PK), glucose 6-phosphate dehydrogenase (G6PDH) and trehalase, as well as expressions of the genes related to glycolysis, resulting in carbohydrate homeostasis disorder. Moreover, it was found that 3-BrPA enhanced 20-hydroxyecdysone (20E) signaling by upregulating HcCYP306A1 and HcCYP314A1, two critical genes in 20E synthesis pathway, and accelerated chitin synthesis by upregulating transcriptional levels of genes in the chitin synthesis pathway in H. cunea larvae. Taken together, our findings provide a novel insight into the mechanism of glycolytic inhibitor in regulating the growth and development of insects, and lay a foundation for the potential application of glycolytic inhibitors in pest control as well.
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Carboidratos , Glicólise , Animais , Homeostase , Larva , PiruvatosRESUMO
Here, the crystal structure, phase analysis, site occupancy, and luminescence properties of NCMP:Eu2+,Tb3+,Mn2+ have been studied for the first time. Under 335 nm ultraviolet excitation, the NCMP:Eu2+ phosphors show narrow-band blue emission. In addition, we discuss the reason for a continuous red shift for the emission spectra of NCMP:xEu2+ by raising the x value. The efficient ET processes of Eu2+ â Tb3+ and Eu2+ â Mn2+ were investigated by the luminescence spectra and decay curves. The ET efficiencies reach 92.58% at y = 0.15 for NCMP:0.01Eu2+,yTb3+ and 99.85% at z = 0.15 for NCMP:0.01Eu2+,zMn2+ phosphors, respectively. The efficient energy transfer processes greatly improve the quantum efficiency, luminous intensity, and thermal stability. Bright green and red emissions can be realized through changing the related ratio of Eu2+, Tb3+, and Mn2+. In addition, the excellent performance of the prepared white LED lamps utilizing a 385 nm chip combined with our prepared NCMP:Eu2+,Tb3+/Mn2+ phosphors indicates that NCMP:0.01Eu2+,yTb3+ and NCMP:0.01Eu2+,zMn2+ phosphors can be potential green and red phosphors for white LEDs.
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A modified structure Ca(Mg0.8Al0.2)(Si1.8Al0.2)O6 (denoted as CMASO) from the evolution of CaMgSi2O6 (denoted as CMSO) codoped with Ce3+ and Tb3+ ions was designed successfully by solid reaction method for application in phosphor-converted white-light-emitting diode (pc-wLED). The Rietveld refinement of these two structures verified the changes derived from the replacement of some of the Mg2+ and Si4+ ions by Al3+ ions. The band gaps were calculated by density-functional theory (DFT) calculation method to verify the change of Al3+ ions replacing further, and the diffuse reflectance spectra (DRS) proved the veracity of the calculation result. The phosphors CMASO:Ce3+ showed blue emission excited by a wider excitation wavelength from 280 nm to 370 nm. The change of structure lead to the absorbable range broaden and the emission peak shifted to longer wavelength, compared with CMSO:Ce3+, although the amount of emitting center was the same. The reason for these phenomena was discussed in detail. The codoped phosphors CMASO:Ce3+,Tb3+ exhibited different emission colors from blue to green as the concentration of Tb3+ ions increased. Combined with commercial red phosphor CaAlSiN3:Eu2+ and ultraviolet LED (UV-LED) chips, the selected appropriate samples achieved white emission. The correlated color temperature (CCT) was 6137 K and the color rendering index (Ra) was 80.5, indicating that they could act as potential phosphors for possible applications in pc-wLED.
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Structure determines properties, and properties determine applications, which is an important ideology of natural sciences. For optical materials, it is vital to lucubrate the corresponding relationship between the local crystal structure and luminescence properties for their design, synthesis, and application. This work reports a newly designed Y2Mg2Al2Si2O12(YMAS):Eu3+ red phosphor, in which difunctional Eu3+ ion is used as a red-light activator and spectroscopic probe. The qualitative and quantitative studies on the relationship between the local crystal structure and the luminescence properties of YMAS:Eu3+ are performed experimentally and computationally, using the Y3Al5O12 (YAG):Eu3+ as contrast. Moreover, compared with YAG:Eu3+, the newly designed YMAS:Eu3+ has stronger luminescence, superior Commission Internationale de L'Eclairage chromaticity coordinates, a lower optimal doping concentration, and equally excellent thermal stability. The satisfactory color-rendering index of packaged white-light-emitting diodes demonstrates its potential performance as a red phosphor. Briefly, this work provides not only a new case for the study of the local crystal structure and luminescence properties but also a new possibility for the application of a red phosphor in solid-state lighting.
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A series of emission-tunable Ce3+/Tb3+/Eu2+ doped Ca2(Mg0.75Al0.25)(Si1.75Al0.25)O7 (denoted as CMAS) phosphors have been synthesized via a high temperature solid-state reaction method. The luminescence properties, color tuning, quantum yields (QYs), energy transfer of Ce3+ to Tb3+/Eu2+, thermal stability, performance of LED devices and ratiometric temperature sensing application have been systematically investigated, respectively. Importantly, through the study of thermal stability, we found that Ce3+ and Tb3+ co-doped samples were suitable for WLED applications, while Ce3+ and Eu2+ co-doped samples were suitable for temperature sensing applications. Due to the energy transfer, Ce3+/Tb3+ co-doped samples had high luminous efficiency and the quantum efficiency of more than 80% could be achieved. Their emission colors can modulate from blue to green. In addition, on the basis of the evaluation of the as-fabricated white LED lamps via selecting the corresponding phosphors, the CCT can reach 4275 K and the CRI can increase to 86.8, indicating that this series of phosphors can act as potential color-tunable phosphors for possible applications in ultraviolet light based white LEDs. Importantly, it is found that the fluorescence intensity ratio of CMAS : 5%Ce3+,0.5%Eu2+ displays linear correlation with temperature in a wide range of 253-373 K with a high sensitivity of 2.49% K-1, indicating that it could be a good candidate for ratiometric optical thermometry.
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TiO2:Eu3+ nanofibers diameters can be tuned by changing the mixed solvent ratio are synthesized via the electrospinning technique. Concentration quenching phenomena and the relationship of the PL intensity ratio I(5D0-7F2)/I(5D0-7F1) with the Eu doping concentration are discussed. Notably, the luminescence intensity is enhanced by about 7.8 fold by coating SiO2 gel layer on the TiO2:Eu3+ nanofibers, which is successfully performed via a sol-gel process followed by calcination. Furthermore, these fibers are characterized systematically via X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), UV-vis diffuse reflectance spectroscopy (UV-vis DRS), Fourier transform infrared spectroscopy (FT-IR), and photoluminescence (PL) spectroscopy. Additionally, their Judd-Ofelt and spectral parameters are calculated to investigate their local structures. The relatively low Ω2 value of the coated samples reveals a decrease in covalency in the Eu-O bonds and an increase in the symmetric nature of Eu3+, which indicate that the perturbation effect of the crystal field in the solid system is larger than that of the uncoated samples. FT-IR analysis indicates the formation of Ti-O-Si bonds, which provide the ligand field in the interface between the TiO2:Eu3+ nanofibers and SiO2 layer and can repair the surface unsaturated bonds. This reduces the selection rules for radiative transitions, thereby the state of the Eu3+ ions is converted from dormant to activated. Moreover, the silica coating stabilizes the surface of the TiO2:Eu3+ nanofibers and eliminates the surface defects. Finally, a detailed mechanism is proposed to explain the luminescence enhancement behavior.