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        A blue and Red Bicolor Emission Phosphor Excited by a Single n‑UV and Its Self‑reduction of Eu3+ → Eu2+ in Na2Al2B2O7

        Jiachao Chen,Songsheng Zheng,Xing Yang,Ying Lv,Yang Li,Chao Chen 대한금속·재료학회 2020 ELECTRONIC MATERIALS LETTERS Vol.16 No.6

        It has great significance to find a path on generating multicolor with one n-UV chip coated with single phosphor. Herein, Eu doped Na2Al2B2O7 (NAB) phosphor is synthesized by solid state reaction in air atmosphere. Both 4f65d1 → 4f7 transitions of Eu2+ (445 nm) and f–f transitions as 5D0 → 7FJ (J = 0, 1, and 2) of Eu3+ (570–650 nm) have been observed. When increasing Eu doping concentration, both the luminescence intensity and lifetime of Eu3+ are increased and no obvious concentration quenching is observed, while the emission strength of Eu2+ does not change monotonically but with two remarkable peak values. The optimum doping concentration of Eu is 16%. Furthermore, Eu3+ is determined to be from Eu(BO3) matrix itself, and Eu2+ testified by ESR and XPS is created by self-reduction of Eu3+ to Eu2+ in NAB due to charge compensation. When x ≥ 0.16, the Eu3+ ion would rather bond with BO3 triangles in Eu(BO3) than stay as Eu2+ in AlO4 tetrahedral in NAB. Furthermore, the as prepared sample shows an excellent thermal stability and the PL quantum efficiencies of NAB: 0.16Eu sample excited by 341 nm and 393 nm are 11.99% and 9.39%, respectively. Additionally, the calculated CIE chromaticity coordinates signify that a couple of colors can be generated by adjusting the excitation wavelength owing to the strength changes between blue and red emissions. Therefore, this novel bicolor phosphor can serve as a potential candidate for w-LEDs applications.

      • KCI등재

        Do Analysts’ Cross-year Revisions Contain Information about Audit Adjustment? Evidence from the Chinese Capital Market

        Qingqing Liu,Songsheng Chen,Zhili Tian 한국증권학회 2021 Asia-Pacific Journal of Financial Studies Vol.50 No.4

        This study tests the information content of changes in analysts’ earnings forecasts. Using audit adjustment data from China, this study investigates whether changes in analysts’ crossyear forecast revisions reflect audit information. The results show that the cross-year revision of analysts’ earnings per share forecasts is positively related to the magnitude of audit adjustment, which may be mainly due to analysts’ communication with management. Furthermore, analysts who display higher forecast frequency, who issue their last forecast closer to the day the annual report is announced, or who show better forecast performance reflect a greater amount of audit information in their cross-year forecast revisions.

      • KCI등재

        Evaluation of the sp3/sp2 ratio of DLC films by RF-PECVD and its quantitative relationship with optical band gap

        Sheng Hongxun,Xiong Wenwen,Zheng Songsheng,Chen Chao,He Song,Cheng Qijin 한국탄소학회 2021 Carbon Letters Vol.31 No.5

        DLC has been attractive as semiconductor materials for solar cell due to its biological friendliness, fexible microstructures, and especially its tunable band gap. In order to fabricate high-efciency multiband gap solar cell, it is important to control the sp3 / sp2 bonds ratio of DLC flm corresponding to optical band gap (Eg). There are many references reporting the relations among the fabrication conditions, Eg, sp3 /sp2 , and ID/IG. However, a more comprehensive database is needed for controllable fabrication. Especially, the quantitative relationship of sp3 /sp2 ratio to Eg of DLC flm by PECVD is unclear. In this paper, 36 sets of DLC flms were fabricated by RF-PECVD. Characterization methods of XPS, Raman spectroscopy, and IR absorption have been used to determine the sp3 /sp2 ratio of DLC flms. UV/visible light absorption method has applied to evaluate Eg. The Eg obtained is in the range 1.45–3.0 eV. Our results agree well with the references. The XPS spectra gives a linear relationship as Eg=− 0.161 (±0.136)+26.095 (±1.704) · {sp3 (XPS)/sp2 }, the Raman spectra shows a linear function that Eg=1.327 (±0.046)+0.428 (±0.036) · (ID/IG), as well as the FTIR analysis demonstrates that Eg=− 0.492 (±0.093)+0.464 (±0.044) · {sp3 (FTIR)/sp2 }.

      • KCI등재

        β-Catenin promotes long-term survival and angiogenesis of peripheral blood mesenchymal stem cells via the Oct4 signaling pathway

        Wang Pengzhen,Deng Zhanyu,Li Aiguo,Li Rongsen,Huang Weiguang,Huang Weiguang,Chen Songsheng,Li Biao,Li Biao 생화학분자생물학회 2022 Experimental and molecular medicine Vol.54 No.-

        Stem cell therapy has been extensively studied to improve heart function following myocardial infarction; however, its therapeutic potency is limited by low rates of engraftment, survival, and differentiation. Here, we aimed to determine the roles of the β-catenin/Oct4 signaling axis in the regulation of long-term survival and angiogenesis of peripheral blood mesenchymal stem cells (PBMSCs). These cells were obtained from rat abdominal aortic blood. We showed that β-catenin promotes the self-renewal, antiapoptotic effects, and long-term survival of PBMSCs by activating the Oct4 pathway through upregulation of the expression of the antiapoptotic factors Bcl2 and survivin and the proangiogenic cytokine bFGF and suppression of the levels of the proapoptotic factors Bax and cleaved caspase-3. β-Catenin overexpression increased Oct4 expression. β-Catenin knockdown suppressed Oct4 expression in PBMSCs. However, β-catenin levels were not affected by Oct4 overexpression or knockdown. Chromatin immunoprecipitation assays proved that β-catenin directly regulates Oct4 transcription in PBMSCs. In vivo, PBMSCs overexpressing β-catenin showed high survival in infarcted hearts and resulted in better myocardial repair. Further functional analysis identified Oct4 as the direct upstream regulator of Ang1, bFGF, HGF, VEGF, Bcl2, and survivin, which cooperatively drive antiapoptosis and angiogenesis of engrafted PBMSCs. These findings revealed the regulation of β-catenin in PBMSCs by the Oct4-mediated antiapoptotic/proangiogenic signaling axis and provide a breakthrough point for improving the long-term survival and therapeutic effects of PBMSCs.

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