APPLIED CATALYSIS A-GENERAL
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2016
·
IF 4.012
Xianghai Song,Yuanfeng Wu,Fufeng Cai,Donghui Pan,Guomin Xiao
A series of efficient and low-cost Li/ZnO catalysts were prepared by a simple impregnation method and investigated for the synthesis of glycerol carbonate (GC) from the transesterification of glycerol with dimethyl carbonate (DMC). The Li/ZnO catalysts were characterized using XRD, SEM, FT-IR, TG-DSC, TPD and XPS. It was found that the basicity of the catalysts highly depended on the Li loading and calcination temperature. The weak and moderate basic sites on the catalyst surfaces originated from the ZnO and Li + interaction. The strong basic sites were attributed to the substitution of Zn 2+ by Li + in the ZnO lattice, which led to straining of Zn-O bonds and the formation of [Li + O − ] species. It was the strong basic sites rather than the weak and moderate basic sites that catalyzed the transesterification of glycerol with DMC. The highest catalytic activity was observed over the ZnO loaded with 1 wt.% LiNO 3 and calcined at 500 °C. Glycerol conversion of 97.40% and GC yield of 95.84% were obtained over this catalyst at 95 °C in 4 h.
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INORGANIC CHEMISTRY
·
2017
·
IF 4.857
Yi-Gang Chen,Mei-Ling Xing,Peng-Fei Liu,Yao Guo,Nan Yang,Xian-Ming Zhang
Two new phosphates—Cs6Mg6(PO3)18 (CMP) and Cs2MgZn2(P2O7)2 (CMZP)—have been obtained, using high-temperature molten methods. Crystals of CMP with the polar P21 space group display a new three-dimensional (3D) anionic framework possessing two one-dimensional (1D) [PO3]∞ chains that are interconnected by isolated MgO6 octahedra, while CMZP with centrosymmetric monoclinic space group P21/c possesses a new [MgZn2P4O20]14– structure unit consisting of two isolated P2O7 dimers, one ZnO4, and two disordered Mg/ZnO4 tetrahedral units. The polar phosphate CMP with deep-UV transparency (below 190 nm) shows weak second harmonic generation (SHG) response (0.1 × KDP), and the dipole moment analysis suggests that the weak SHG response mostly originates from much distorted CsOn polyhedron. Some related properties, such as optics, thermostability, and band structure derived from density functional theory, were explored.
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HIGH PERFORMANCE POLYMERS
·
2016
·
IF 1.045
Guangliang Song,Lina Wang,Dandan Liu,Jianan Yao,Yiming Cao
A series of polyimide (PI) membranes were prepared based on three triphenylamine-based diamines, namely 4,4′-diaminotriphenylamine, 4,4′-diamino-3′′,5′′-dimethyltriphenylamine, and 4,4′-diamino-3′′,5′′-ditrifluoromethyltriphenylamine, via thermal imidization procedure. The PI membranes displayed good thermal properties, with glass transition temperatures of 279–341°C and 5% weight loss temperatures above 515°C under a nitrogen atmosphere. The gas permeation properties of the membranes were investigated and interpreted from the viewpoint of the PI backbone structure. The gas permeation coefficients increased as the substituent pendant groups at the 3′′,5′′ positions of the triphenylamine varied from –H to –CH3 and –CF3, and the permselectivity of gas pairs (including hydrogen/nitrogen (N2), oxygen/N2, carbon dioxide (CO2)/N2, and CO2/methane) decreased in this order. The diffusion coefficients and solubility coefficients were calculated, and the results revealed the variation of the substituted triphenylamine units principally influenced the diffusion coefficients, indicating that the substituted triphenylamine affected the gas transport properties by “diffusivity-controlled” modification.
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JOURNAL OF PHYSICAL CHEMISTRY B
·
2017
·
IF 3.177
Minglun Li,Bilin Zhuang,Yuyuan Lu,Zhen-Gang Wang,Lijia An
We present a novel method for obtaining salt polarizabilities in aqueous solutions based on our recent theory for the refractive index of salt solutions, which predicts a linear relationship between the refractive index and the salt concentration at low concentrations, with a slope determined by the intrinsic values of the salt polarizability and the density of the solution. Here we apply this theory to determine the polarizabilities of 32 strong electrolyte salts in aqueous solutions from refractive index and density measurements. Setting Li+ as the standard ion, we then determine the polarizabilities of seven cations (Na+, K+, Rb+, Cs+, Ca2+, Ba2+, and Sr2+) and seven anions (F–, Cl–, Br–, I–, ClO4–, NO3–, and SO42–), which can be used as important reference data. We investigate the effect of temperature on salt polarizabilities, which decreases slightly with increasing temperature. The ion polarizability is found to be proportional to the cube of bare ionic radius (rbare3) for univalent ions, but the relationship does not hold for multivalent ions. Contrary to findings of Krishnamurti, we find no significant linear relationship between ion polarizability and the square of the atomic number (N2) for smaller ions.
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Journal of Materials Chemistry C
·
2016
·Vol. 4
·期 40
·9598-9607
·
IF 5.066
M. Wu,X. F. Jiang,E. H. Song,J. Su,Z. T. Chen,W. B. Dai,S. Ye,Q. Y. Zhang
Successful upconversion (UC) tuning from multi-bands to one single red band from Er3+ ions was realized in cubic perovskite ABF3:Yb3+/Er3+ (A = K, Cs; B = Zn, Cd) through Mn2+ doping. Based on UC emission spectra and decay kinetics of KZnF3:Yb3+/Er3+ with different Mn2+ contents, a bidirectional energy transfer process between Mn2+ and Er3+ ions was confirmed to explain the UC tuning mechanism. More importantly, we studied the influence of the Mn2+ energy level position on the UC properties for Er3+ in ABF3 hosts. Interestingly, great enhancement of green UC emissions was observed for Er3+ ions in KCdF3 and CsCdF3 hosts upon Mn2+ doping. Comparison of UC emissions and lifetimes of Er3+ ions in the three materials was carried out to probe the different UC processes in ABF3 (A = K, Cs; B = Zn, Cd) hosts. The different energy transfer mechanism between Mn2+ and Er3+, which is affected by the Mn2+ energy level position, was proposed to explain the UC difference in the three matrices. This research convincingly confirmed the occurrence of energy transfer between Er3+ and Mn2+ ions and provided deep insights into the importance of the Mn2+ energy level position in tuning the UC properties of Er3+ in diverse hosts, while allowing us to better control the UC properties through Mn2+ doping.
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INORGANIC CHEMISTRY
·
2017
·
IF 4.857
Pifu Gong,Siyang Luo,Ke Xiao,Qian Huang,Yi Yang,Hongwei Huang,Yicheng Wu,Chuangtian Chen,Zheshuai Lin
A new perovskite stoichiometric alkali tin dihalides compound, Cs3Sn3F2Cl7, is synthesized by a hydrothermal method. This compound belongs to the monoclinic space group of P21/c with cell parameters of a = 9.5645(4) Å, b = 14.2057(7) Å, c = 13.5828(6) Å, and β = 93.2450(10)°. Unlike the common perovskites in which octahedra are interconnected to be a three-dimensional network, Cs3Sn3F2Cl7 possesses a zero-dimensional structure consisting of Cs+ cations, isolated [SnCl3]− trigonal pyramids, and dimer structural units [Sn2F2Cl4]2–; the latter microscopic unit is found for the first time. The thermal stability and UV–vis–NIR diffuse reflectance spectroscopy in Cs3Sn3F2Cl7 are measured, and the electronic structure is calculated. Interestingly, the 5s2 lone-pair electrons on Sn2+ cations are stereochemically active, which results in a pretty good photocatalytic activity of the title compound.
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INTERNATIONAL JOURNAL OF HYDROGEN ENERGY
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2017
·
IF 3.582
Jiaqi Xu,Qilang Lin,Yan Yu,Dongyang Chen,Zhuoliang Ye
Linear fluorinated poly(arylene ether)s with and without pendent allyl groups (CFPAE and FPAE) were successfully polymerized from decafluorobiphenyl at room temperature . The subsequent SN 2 nucleophilic substitution of the remaining F atom on CFPAE and FPAE with sodium 4-hydroxybenzenesulfonate yielded SCFPAE and SFPAEs in one simple step under mild conditions. The chemical structures of the polymers were confirmed by 1 H NMR and FT-IR. The ion exchange capacity (IEC), inherent viscosity, water uptake, swelling ratio, proton conductivity , mechanical property, thermal stability, and oxidative stability of the SFPAEs were characterized. The experimental results revealed that the IEC of the SFPAEs can be facilely controlled by the loading amount of sodium 4-hydroxybenzenesulfonate in the reaction mixture. The SFPAE-20 with an IEC of 2.0 mmol g −1 exhibited an in-plane proton conductivity of 106 mS cm −1 at 30 °C, higher than that of Nafion N212. More importantly, the SFPAEs showed significantly enhanced oxidative stabilities compared to sulfonated non-fluorinated analogs in literature. While there was still a trade-off between proton conductivity and mechanical strength as often seen for homogeneous systems, the SFPAEs were demonstrated to be promising candidates for proton exchange membranes .
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GIANT
·
2024
·
IF 5.4
Hong Li,Weiyi Jin,Weiyu Zhang,Jie Li,Jiaqi Ji,Yi Tang,Tianqi Yang,Shujiang Zhang,Haixia Yang,Chenliang Gong
Low-dielectric, transparent, and high-heat-resistant polyimide (PI) films are vital for flexible electronics and high-frequency communication devices. However, balancing these properties within intrinsic polyimides remains a significant challenge. In this work, a nonplanar diamine monomer, 2,7-bis(3,5-bis(trifluoromethyl)phenyl)-9,9-bis(4-nitrophenyl)-9H-fluorene (BTFDA), containing a Cardo structure and four trifluoromethyl groups, was synthesized and copolymerized with commercial monomers to produce a series of polyimides (CPI-X). These CPI-X exhibit exceptional heat resistance, with glass transition temperatures ( T g ) exceeding 350 °C, decomposition temperatures ( T d5 % ) above 530 °C, and low thermal expansion coefficients (CTE < 20.8 ppm/K). Additionally, they have excellent optical properties with over 92 % transparency at 450 nm and low birefringence (Δ n = 0.00042). They also demonstrate good hydrophobicity with low water absorption ( M a % = 0.04 %) and high-water contact angles ( C a = 97.6°). Most importantly, the CPI-X films show excellent dielectric properties ( D k = 2.25, D f = 0.00365 at 1 MHz, D k = 2.13, D f = 0.0065 at 10 GHz). Such intrinsic PI films with low D k values may be ideal candidates for next-generation interlayer media.
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Advanced Optical Materials
·
2024
·Vol. 12
·期 19
·2400250
·
IF 8
Wenyu Tang,Yuanjing Wang,Yayun Zhou,Chuang Zhang,Zhen Chen,Fanquan He,Enhai Song,Qinyuan Zhang
Mn 4+ -activated red-light fluorides are widely used in high-quality displays, due to the narrow-spectral emission. However, achieving exceptional chromaticity coordinates and appropriate quantum efficiency (QE) at the same time is a great challenge. Herein, a Li substitution strategy is proposed for enhancing QE and improving the thermal stability of red-light Mn 4+ -activated Cs 2 NaGaF 6 (CNGF). The external quantum efficiency (EQE) of optimal Cs 2 NaGaF 6 : Mn 4+ , Li + (CNGF: Mn 4+ , Li + ) is improved from 15.79% to 33.61% and thermal stability increases from 68.4% to 85.5% (intensity at 150 °C relative to room temperature). EQE enhancement mechanism on the strategy is explored that Li substitution increases the local structural distortion of Mn 4+ for relieving the parity forbidden, and promotes Mn 4+ doping in the host lattice, which provides new insights for improving the QE of Mn 4+ non-equivalent doped fluorides. Moreover, with exceptional chromaticity coordinates of (0.7029, 0.2970), optimal sample CNGF: 4.8 mol% Mn 4+ ,0.9 mol% Li + can be used to fabricate white light-emitting diode (w-LED) backlight, which obtains wide color gamut of 110.68% National Television Standards Committee (NTSC) and high luminous efficacy of 110.57 lm W −1 , indicating that CNGF: Mn 4+ , Li + is a promising candidate for the next generation of wide gamut and efficient displays.
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MATERIALS RESEARCH BULLETIN
·
2024
·
IF 5.3
Jun Zheng,Linglin Wang,Lei Feng,Yuhan Gao,Feiyao Ren,Siyu Liu,Ting Zhou,Xiaochun Wu,Xin Lai,Daojiang Gao
Recently, Mn 4+ -activated fluoride red phosphors have received intensive attention due to their excellent luminescence properties. However, poor moisture resistance hinders their commercial application. Herein, (K 1- x Cs x ) 2 NbF 7 :Mn 4+ phosphors were designed and synthesized. All the obtained samples are rod-like microcrystals with monoclinic phase structure, Cs + -doping concentration has little influence on the microstructure while significantly impacts their luminescence properties. Specially, the composition optimized (K 1- x Cs x ) 2 NbF 7 :Mn 4+ ( x = 0.3) phosphor has the color purity of 94.20 %, the quantum yield of 53.90 % and the decay lifetime of 3.59 ms. More importantly, the optimized phosphor can maintain 83.20 % of the initial emission intensity after being immersed in distilled water for 1440 min, showing the excellent moisture resistance. A warm WLED with high CRI of 85 and low CCT of 4362 K is achieved by coating the obtained optimized red phosphor in chip. Our work demonstrates that the (K 1- x Cs x ) 2 NbF 7 :Mn 4+ red phosphors possess a great potential application in warm WLEDs.
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CHEMICAL ENGINEERING JOURNAL
·
2024
·
IF 13.3
Lisha Liang,Yuxiang Zhao,Wuxin Zhang,Haokai Yan,Mengwei Chen,Yuan Chen,Jin Zhou,Tao Zhang
The sp 2 -carbon-conjugated porous polymers (sp 2 c-CPPs) that possess high porosity, chemical stability, and carrier mobility are potential for uranium extraction from seawater, which is tremendous meaningful for the rapidly growing demands of the nuclear industry due to the abundant uranium resources (4.5 billion tons) in ocean. Here, we report the synthesis of three sp 2 c-CPP films (DMPN-TFPT, BN-TFPT and TMTN-TFPT) directly on Cu substrate that can work as electrodes for electrochemical uranium extraction. Furthermore, we designed a photovoltaic-electrocatalysis (PV-EC) system to enhance the uranium extraction capacity, meanwhile, modified oxime groups on sp 2 c-CPPs film to enhance uranium ion selectivity. The DMPN-TFPT electrode shows ultra-high uranium extraction performance (1022.02 mg m −2 ) in 8 ppm uranyl-spiked simulated seawater, which is higher than that of BN-TFPT film (426.27 mg m −2 ) and TMTN-TFPT film (607.30 mg m −2 ) because of the higher in-plane electron delocalization. Additionally, in ultra-low concentration of simulated seawater (3.3 ppb), the DMPN-TFPT film also exhibited a high capacity up to 81.74 mg m −2 within 30 days. This work shows the great potential of sp 2 c-CPP films on solar-driven electrochemical uranium extraction.
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Energy Storage Materials
·
2024
·
IF 18.9
Wenxia Sima,Yuxiang Mai,Potao Sun,Ming Yang,Tao Yuan,Binghao Chen,Yuhang Yang
Polyimide, endowed with high thermal resistance due to its aromatic structure, is considered a potential candidate for high-temperature polymer dielectrics. However, the strong electron delocalization in the aromatic structure causes significant leakage current during high-temperature electron transport, impairing energy storage performance. This contradictory relationship presents a bottleneck in enhancing the high-temperature energy storage performance of PI. In this work, inspired by fish migration influenced by vortices, we propose inducing electron displacement through fluorine-modified aromatic structures, constructing an internal electric field in PI to affect electron transport. This approach cleverly resolves the conflict between thermal resistance and current loss caused by the aromatic main chain in PI, achieving a synergistic enhancement of thermal resistance and high-temperature energy storage performance. Experimental results show significant improvements in both the high heat-resistant quality and high-temperature energy storage performance of PI. The glass transition temperature increased from 257.32 °C to 264.07 °C, and the leakage current density decreased from 7.1 × 10 –7 A/cm 2 to 2.8 × 10 –8 A/cm². Simultaneously, with a charge-discharge efficiency of approximately 90 %, the discharge energy density increased from 0.36 J/cm 3 to 5.22 J/cm 3 , an improvement of 1345.98 %. This strategy validates the potential of aromatic structures as the main chain for high-temperature energy storage polymers.
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