Yixuan Ma,Jianqiang Liu,Longxiao Yang,Ying Ouyang,Mudi Xin,Enhui Xing,Yibin Luo,Xingtian Shu
Phosphorus modification has been extensively demonstrated as the most effective approach to enhance the hydrothermal stability of ZSM-5 (MFI) zeolites on both industrial and research scales with phosphoric acid (H 3 PO 4 ) and phosphates as precursors. However, the incorporation of H 3 PO 4 into FER zeolites exerts a detrimental impact on their crystallinities, acidity, microporous structure, and hydrothermal stability. This phenomenon arises from two key factors: Firstly, the larger precursor size of H 3 PO 4 hinders its migration into the narrow channels of FER zeolite during the impregnation process; Secondly, the abundant Si-OH groups on the FER zeolites’ external surface can trap H 3 PO 4 to prevent it from penetrating channels of FER zeolites. It was verified that hypophosphorous acid (H 3 PO 2 ), owing to its smaller precursor size and slight tendency to be trapped by external isolated Si-OH groups, tended to migrate into the channels and subsequently disperse homogeneously, thereby enhancing the accessibility to tetrahedrally coordinated framework aluminium (TFAl). Moreover, 29 Si, 27 Al, and 31 P MAS NMR results proved the fact that the FER zeolite modified with H 3 PO 2 effectively facilitated the formation of more Si-OH-Al-O-P active sites during hydrothermal aging, which subsequently improved the conversion and light olefins yield in the catalytic cracking of 1-octene.
Yuexiao Pan,Ying Qin,Haoshuai Wang,Tiantian Zhao,Weiyou Xu,Qian Mia,Jun Zou
The quest for lead-free materials capable of emitting white-light has been a focal point in the realm of luminescent materials due to their potential applications in lighting and display technologies. This study presents a novel approach to achieving broadband white-light emission through the doping of Ag+ in zero-dimensional (0D) lead-free perovskite Cs2InCl5·H2O (CICH), and the strategic addition of H3PO2 (HPA) to facilitate the substitution of Ag+ for In3+. The PL spectra revealed that the emission intensity and the corresponding lifetime of the Ag+-doped CICH samples increased with Ag+ concentration, reaching a maximum at 7% Ag+ doping. This enhancement is attributed to the suppression of non-radiative recombination and the enhancement of self-trapped excitons (STEs) emission, which is a direct result of the structural deformation induced by Ag+ substitution for In3+. The large Stokes shift of 255 nm and the long luminescence lifetime of 20.56 μs observed in the optimized sample S7-CICH:Ag+ underscore the high quality of the STEs emission. The thermal stability of the CICH:Ag+ was exceptional, with a decomposition temperature exceeding 600 °C, indicating their resilience in high-temperature environments. The significance of this research lies in the development of a new class of lead-free luminescent materials that combine high efficiency, broad emission, and thermal stability.
Luminescent metal halides doped with ns2-metal ions, such as 6s2-metal Bi3+, show excellent optoelectronic properties. However, the origin of the high photoluminescence quantum yield (PLQY) of Cs2SnCl6:Bi remains controversial and unclear. In this study, a series of Cs2SnCl6:Bi were synthesized by adopting different tin precursors of SnCl2/SnCl4. The samples from SnCl2 exhibited much higher PLQY than those from SnCl4, and the doping concentrations of Bi3+ had little effect on the high PLQY. When H3PO2 is added to the precursor of SnCl4 to reduce Sn4+ to Sn2+, the prepared Cs2SnCl6:Bi shows bright emission light and high PLQY. The high PLQY of Cs2SnCl6:Bi is attributed to the co-doping of Bi3+ and Sn2+. [SnCl4]2− and two VCl induce a large extra vibrational energy of the heavy localized excitons from [BiCl5]2− to enhance the efficiency of radiative recombination for high PLQY. This work deepens the understanding of the luminescence mechanism of Cs2SnCl6:Bi and supplies significant references for developing more perovskite materials with outstanding luminescence.
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