Search

To achieving high-quality white light emitting diodes (LED), a series of novel red-emitting phosphors NaMg3In1-zYz(Mo1-yWyO4-xFx)5: 0.10Eu3+ (x = 0–0.20, y = 0–0.05, z = 0–0.20) have been obtained via solid-state reaction process. The luminescent properties of NaMg3In(MoO4)5: 0.10Eu3+, and the effect of partial substituting Y3+/W6+/F− ions on the structure and properties of this phosphor were investigated on detailed. The crystal structure of these phosphors was characterized by X-ray diffraction, scanning electron microcopy, energy-dispersive spectra, and Raman spectra. The luminescence properties and decay properties of those samples were also studied. The luminescent intensity and internal quantum efficiency of NaMg3In(MoO4)5: 0.10Eu3+ phosphor partially substituted by Y3+/W6+/F− ions was 1.59 and 2.76 times than that of the sample without partial substitution, due to the distort of local crystal field surrounding the Eu3+ ions. By employed the as-synthesized NaMg3In0.85Y0.05 (Mo0.96W0.04O3.84F0.16)5: 0.10Eu3+ phosphor as red component, a high-performance white LED with a low 4543 K correlated color temperature and high color-rendering index Ra = 90.0 has been fabricated with a 395 nm near-UV chip, commercial green and blue phosphors. These results implied that NaMg3In(MoO4)5: 0.10Eu3+ phosphor partially substituted by Y3+/W6+/F− ions could be used as a potential red-emitting candidate for white light-emitting-diodes. [ABSTRACT FROM AUTHOR]

Vegetation restoration is the primary strategy employed for the purification and restoration of habitats in the Zhegao River wetlands. To investigate the changing characteristics of soil microbial biomass carbon/nitrogen (MBC/MBN) and soil enzyme activities in wetlands undergoing different vegetation restoration treatments, those involving reed and willow restoration were studied in 2014 (WR8) and 2021 (WR1), with a native vegetation wetland (NW) used as a control. This study examined changes in the MBC/MBN, sucrase (Suc), urease (Ure), and acid phosphatase (Acp) in these wetlands. The results indicated that during the restoration of Zhegao River wetlands, reed vegetation had a stronger positive effect on soil properties after one year of restoration than that of willow vegetation. After eight years, the effects of willow vegetation restoration were greater than those of reed vegetation restoration. The activities of MBC, MBN, Suc, Ure, and Acp in the reed and willow wetland soils for different years of vegetation restoration decreased with greater soil depth. Thus, reeds and willows have distinct contributions toward enhancing the ecological service functions of the Zhegao River wetlands for different restoration years, which provides a scientific basis for the selection and protection of ecological wetland restoration. [ABSTRACT FROM AUTHOR]

Novel red phosphors Sr7Sb2O12:Eu3+ and Sr7Sb2O12:Eu3+, M+ (M = Li, Na, K) were synthesized via a high temperature solid-state method and their luminescent properties were investigated to figure out the promising application in warm white light-emitting diodes (LED). The phase structure, crystal morphology, luminescence properties, luminescence decay lifetime, thermal stability and chromaticity coordinate of the as-synthesized phosphors were investigated in detail. Sr7Sb2O12:Eu3+ could be efficiently excited by the near-ultraviolet (UV) light and exhibited bright red emission around 612 nm. When co-doped with the charge compensation M+ (M = Li, Na, K) ions, the emission intensity of Eu3+ can be enhanced to some extent. The optimal Eu3+ doping concentration was determined to be about x = 0.2 and concentration quenching mechanism in Sr7Sb2O12:Eu3+ sample was attributed to the electric dipole–dipole interaction. The temperature-dependent spectra of Sr7Sb2O12:Eu3+ implied that this sample shows good thermal-stable properties. The decay lifetime of Sr7Sb2O12:0.2Eu3+ was about 1.44 ms. Combining with the red Sr7Sb2O12:0.20Eu3+, blue BaMgAl10O17:Eu2+, yellow (Ba,Sr)2SiO4:Eu2+ phosphor and a 395 nm near-UV LED chip, a white LED with low correlated color temperature (CCT = 4260 K) and high-color rendering index (Ra = 91.8) was fabricated. The overall work suggested that Sr7Sb2O12:Eu3+ phosphor is a promising red-emitting component applied in warm white LED. [ABSTRACT FROM AUTHOR]

Efficiently red-emitting Pr3+-doped LnNbO4 (Ln = La, Gd, and Y) phosphors have been successfully prepared by the traditional high-temperature solid-state method. Those phosphors were characterized by X-ray diffraction patterns, photoluminescence spectra, diffuse reflectance spectra, temperature-dependent luminescence spectra, and decay properties in detail. Among those LnNbO4 (Ln = La, Gd and Y) hosts, Pr3+-doped LaNbO4 was found to be the most suitable ones because of the relatively high luminescent efficiency and quenching concentration. The optimum doping concentration and critical energy transfer distance of Pr3+ ions in LnNbO4 (Ln = La, Gd, and Y) were determined. The good thermal stability of Pr3+-doped LaNbO4 was also illustrated by temperature-dependent spectra. These merits demonstrated that Pr3+-doped LnNbO4 (Ln = La, Gd and Y) could be a potential candidate as a red-emitting component in phosphor-converted warm LED. [ABSTRACT FROM AUTHOR]

Efficient orange-emitting SmxY1−xSr2SbO6 phosphors, which can be excited by the UV light at 405 nm and hence emit bright orange light, have been successfully prepared by the traditional high-temperature solid-state method. The phosphors were characterized by X-ray diffraction patterns, SEM, photoluminescence spectra, diffuse reflectance spectra, temperature-dependent luminescence spectra and decay properties in detail. The optimum doping concentration and critical energy transfer distance of SmxY1−xSr2SbO6 were determined from the photoluminescence spectra of as-prepared samples with different Sm3+ ions. The good thermal stability of SmxY1−xSr2SbO6 was also illustrated by temperature-dependent spectra of the SmxY1−xSr2SbO6 phosphors at temperature from 293 to 453 K. These merits demonstrated that SmxY1−xSr2SbO6 could be a potential candidate as an orange-emitting component applied in phosphor-converted warm WLED. [ABSTRACT FROM AUTHOR]

Sm3+-doped LnNbO4 (Ln=La, Y) phosphors were obtained by high-temperature solid-state reaction. The crystal structure of LnNbO4:Sm3+ (Ln=La, Y) was characterized by X-ray diffraction. Luminescent properties of those phosphors were investigated by diffuse reflection spectra, excitation spectra, as well as emission spectra. The emission spectra of those phosphors consisted of several orangish-red emission bands around 550–670 nm upon the excitation at 405 nm, and the luminescent emission intensity of LaNbO4: Sm3+ was much stronger than that of YNbO4: Sm3+. The 87.0% energy transfer efficiency from the host to Sm3+ ions was observed in LaNbO4: Sm3+ phosphor. Furthermore, the critical transfer distance was calculated and the CIE chromaticity coordinates of LaNbO4: Sm3+ samples were in the range of orangish-red. The fluorescence lifetimes of as-prepared LaNbO4: Sm3+ samples were within the millisecond range and the temperature-dependent luminescence indicated LaNbO4: Sm3+ was highly thermal-stable. Our results indicated that novel orangish-red-emitting LnNbO4: Sm3+ (Ln=La, Y) phosphors were expected to have great potential in white LEDs. [ABSTRACT FROM AUTHOR]

A Pr3+-doped La2(WO4)3 crystal grown by the Czochralski method has been investigated as a promising laser material. The principal axes of the optical indicatrix and Pr3+ concentration of the crystal were determined. The polarized absorption, fluorescence spectra and fluorescence decay curves of the main emission multiplets of the crystal were measured at room temperature. The spectroscopic parameters were obtained by the modified Judd–Ofelt theory combined with the normalized method. The peak stimulated emission cross-sections of the major emission lines were estimated. The good spectroscopic properties imply that the Pr3+:La2(WO4)3 crystal is a potential laser gain medium for solid-state laser and self-stimulated Raman laser applications. [ABSTRACT FROM AUTHOR]

The polarized absorption spectra, polarized fluorescence spectra, and fluorescence decay curves of Pr3+ ions in anisotropic PbWO4 single crystal, which was grown by the modified Bridgman method, were measured at room temperature. The standard and modified Judd-Ofelt theories, extended to anisotropic crystal, have been applied to analyze the spectra. The spectroscopic parameters, including the Judd-Ofelt intensity parameters Ot?(t=2,4,6), spontaneous emission probabilities, fluorescence branching ratios, radiative lifetimes, stimulated emission cross sections, and fluorescence quantum efficiencies, were estimated. The good spectroscopic properties show the possible application of the Pr3+-doped PbWO4 crystal as solid-state and self-stimulated Raman laser materials. [ABSTRACT FROM AUTHOR]

Objective: To investigate the value of stool-based methylated SDC2 test in physical examination population for the screening of colorectal neoplasms. Methods: Using the prospective cohort study method, from December 2020 to November 2021, 2 107 participants from the First People's Hospital of Xiushui County, Jiangxi Province were enrolled, consisted of 1 012 males and 1 094 females, aged 20-90 years with the median age of 49 years old. Fresh stool samples were collected and SDC2 DNA methylation tests were carried out as the primary screening method. The participants with positive results were recommended to undergo colonoscopy, and those who were negative were followed up by telephone. The positive rate of screening, the compliance of colonoscopy, and the detection of colorectal lesions were analyzed by chi-square test. Combined the follow-up results of negative subjects, the value of SDC2 DNA methylation test for the screening of colorectal neoplasms was evaluated. Results: Among the 2 107 participants, 2 106 completed the SDC2 methylation test. 113 participants (5.4%) were positive. The positive rate of primary screening increased with age significantly (χ 2 =32.135, P <0.001). Out of 113 cases, 72 (63.7%) underwent colonoscopy examinations. Finally, 3 (4.2%) cases of colorectal cancer, 12 (16.7%) cases of advanced adenoma, 31 (43.1%) cases of non-advanced adenoma, and 16 (22.2%) cases of non-adenomatous polyp were detected. The positive predictive value (PPV) of stool-based SDC2 DNA methylation test for intestinal lesions and colorectal neoplasms were 86.1% and 63.9%, respectively. Among the 1 374 follow-up participants, the negative predictive value (NPV) of this test for intestinal lesions and colorectal neoplasms were 97.7% and 99.4%, respectively. Conclusion: Primary stool-based SDC2 DNA methylation test and subsequent colonoscopy examination can effectively find colorectal neoplasms. This strategy may be a potential tool for the screening of colorectal neoplasms in general risk population.