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2020 Volume 36 Issue 11
2020, 36(11): 2005-2013
doi: 10.11862/CJIC.2020.234
Abstract:
It is of great significance to produce C2 oxygenated compounds such as ethanol directly from CO hydrogenation via coal, natural gas or biomass that can replace the traditional oil and food routes. The supported promoted-Rh is the most effective catalyst to realize this transformation. The Rh-promoter (support) contact interfaces are the active sites for the formation of C2 oxygenates from syngas, thus the contact interface areas directly determines the performance of the catalyst. Therefore, recently many researchers have been working on various physical or chemical methods to improve the preparation process of Rh-based catalysts to maximize the metal-promoter interfaces. In this paper, the principle, process, advantages and disadvantages of these methods (coating, formation of composite oxide or alloy, strong electrostatic adsorption, controlled surface reaction method and atomic layer deposition) are briefly introduced and reviewed. Through the combination of the above synthesis methods, it is possible to prepare the catalysts with uniform distribution of well-defined active sites at the interface.
It is of great significance to produce C2 oxygenated compounds such as ethanol directly from CO hydrogenation via coal, natural gas or biomass that can replace the traditional oil and food routes. The supported promoted-Rh is the most effective catalyst to realize this transformation. The Rh-promoter (support) contact interfaces are the active sites for the formation of C2 oxygenates from syngas, thus the contact interface areas directly determines the performance of the catalyst. Therefore, recently many researchers have been working on various physical or chemical methods to improve the preparation process of Rh-based catalysts to maximize the metal-promoter interfaces. In this paper, the principle, process, advantages and disadvantages of these methods (coating, formation of composite oxide or alloy, strong electrostatic adsorption, controlled surface reaction method and atomic layer deposition) are briefly introduced and reviewed. Through the combination of the above synthesis methods, it is possible to prepare the catalysts with uniform distribution of well-defined active sites at the interface.
2020, 36(11): 2014-2022
doi: 10.11862/CJIC.2020.245
Abstract:
Three new coordination polymers with formulas[Zn(L1)(L2)0.5Cl]n (1), [Co(L1)(L2)0.5Cl]n (2) and {[Zn(L1) (L3)]ClO4·1.7H2O}n (3) have been prepared via the combination of zwitterionic carboxylic ligand with Zn(Ⅱ) and Co (Ⅱ) salts under the participation of two bridging imidazole-based isomers, where L1, L2 and L3 are 4-carboxy-1-(4-carboxybenzyl)-pyridinium, 1, 4-bis(imidazole-1-ylmethyl)benzene and 1, 3-bis(imidazole-1-ylmethyl)benzene, respectively. Complexes 1 and 2 are isostructural and feature an undulated 2D herringbone layer structure with (6, 3) topology, exhibiting a rare 2D→3D inclined polycatenated structure. Compared with 1 and 2, complex 3 displays 1D catenated chain structure, which are further assembled into 2D layer via abundant π-π interactions. It is noteworthy that 1~3 can all be considered as consisting of 1D[M(L1)]n chains and bridging bis-imidazole-based ligands. For 1 and 2, the 1D[M(L1)]n chains take helical form and bridging L2 ligands adopting Z-shape. In contrast, the 1D[M(L1)]n chains in 3 exhibit zigzag form and bridging L3 ligands having C-configuration. The results reveal that different N-donor ancillary ligands and anions have a subtle effect on the final structures. The study of optical band gaps showed that the band gaps of 1~3 were 2.96, 1.72 and 3.16 eV, respectively, which indicates that 1~3 have properties of potential wide-band-gap semiconductors.CCDC: 1973985, 1; 1973986, 2; 1973987, 3.
Three new coordination polymers with formulas[Zn(L1)(L2)0.5Cl]n (1), [Co(L1)(L2)0.5Cl]n (2) and {[Zn(L1) (L3)]ClO4·1.7H2O}n (3) have been prepared via the combination of zwitterionic carboxylic ligand with Zn(Ⅱ) and Co (Ⅱ) salts under the participation of two bridging imidazole-based isomers, where L1, L2 and L3 are 4-carboxy-1-(4-carboxybenzyl)-pyridinium, 1, 4-bis(imidazole-1-ylmethyl)benzene and 1, 3-bis(imidazole-1-ylmethyl)benzene, respectively. Complexes 1 and 2 are isostructural and feature an undulated 2D herringbone layer structure with (6, 3) topology, exhibiting a rare 2D→3D inclined polycatenated structure. Compared with 1 and 2, complex 3 displays 1D catenated chain structure, which are further assembled into 2D layer via abundant π-π interactions. It is noteworthy that 1~3 can all be considered as consisting of 1D[M(L1)]n chains and bridging bis-imidazole-based ligands. For 1 and 2, the 1D[M(L1)]n chains take helical form and bridging L2 ligands adopting Z-shape. In contrast, the 1D[M(L1)]n chains in 3 exhibit zigzag form and bridging L3 ligands having C-configuration. The results reveal that different N-donor ancillary ligands and anions have a subtle effect on the final structures. The study of optical band gaps showed that the band gaps of 1~3 were 2.96, 1.72 and 3.16 eV, respectively, which indicates that 1~3 have properties of potential wide-band-gap semiconductors.CCDC: 1973985, 1; 1973986, 2; 1973987, 3.
2020, 36(11): 2124-2134
doi: 10.11862/CJIC.2020.243
Abstract:
Two 2D coordination polymers, namely {[Cu3(μ4-dpna)2(2,2'-bipy)2]·4H2O}n (1) and {[Zn3(μ4-dpna)2(2,2'-bipy)2(H2O)2]·6H2O}n (2) as well as two 1D coordination polymers, namely {[M2(μ4-deta)(phen)2(H2O)]·3H2O}n (M=Mn (3), Zn (4)) have been constructed hydrothermally using H3dpna (H3dpna=5-(3',4'-dicarboxylphenoxy)nicotic acid) or H4deta (H4deta=2,3,2',3'-diphenyl ether tetracarboxylic acid) as a principal building block, 2,2'-bipy (2,2'-bipy=2,2'-bipyridine) or phen (phen=1,10-phenanthroline) as a auxiliary ligand, and copper, zinc or manganese chlorides. The products were isolated as stable crystalline solids and were characterized by IR spectra, elemental analyses, thermogravimetric analyses (TGA), and single-crystal X-ray diffraction analyses. Single-crystal X-ray diffraction analyses revealed that compounds 1 and 2 crystallize in the monoclinic system, space groups P21/c or C2/c. Compounds 1 and 2 disclose two different 2D sheet structures. The structural difference of compounds 1 and 2 is driven by the Cu(Ⅱ)/Zn(Ⅱ) nodes. Compounds 3 and 4 are isostructural and crystallize in the monoclinic system, space group P21/n. Both compounds show a 1D chain structure. The luminescent and photocatalytic properties of the compounds were investigated, showing that compounds 2 and 4 can effectively degrade methylene blue as a model organic dye pollutant.CCDC: 2004109, 1; 2004110, 2; 2004481, 3; 2004482, 4.
Two 2D coordination polymers, namely {[Cu3(μ4-dpna)2(2,2'-bipy)2]·4H2O}n (1) and {[Zn3(μ4-dpna)2(2,2'-bipy)2(H2O)2]·6H2O}n (2) as well as two 1D coordination polymers, namely {[M2(μ4-deta)(phen)2(H2O)]·3H2O}n (M=Mn (3), Zn (4)) have been constructed hydrothermally using H3dpna (H3dpna=5-(3',4'-dicarboxylphenoxy)nicotic acid) or H4deta (H4deta=2,3,2',3'-diphenyl ether tetracarboxylic acid) as a principal building block, 2,2'-bipy (2,2'-bipy=2,2'-bipyridine) or phen (phen=1,10-phenanthroline) as a auxiliary ligand, and copper, zinc or manganese chlorides. The products were isolated as stable crystalline solids and were characterized by IR spectra, elemental analyses, thermogravimetric analyses (TGA), and single-crystal X-ray diffraction analyses. Single-crystal X-ray diffraction analyses revealed that compounds 1 and 2 crystallize in the monoclinic system, space groups P21/c or C2/c. Compounds 1 and 2 disclose two different 2D sheet structures. The structural difference of compounds 1 and 2 is driven by the Cu(Ⅱ)/Zn(Ⅱ) nodes. Compounds 3 and 4 are isostructural and crystallize in the monoclinic system, space group P21/n. Both compounds show a 1D chain structure. The luminescent and photocatalytic properties of the compounds were investigated, showing that compounds 2 and 4 can effectively degrade methylene blue as a model organic dye pollutant.CCDC: 2004109, 1; 2004110, 2; 2004481, 3; 2004482, 4.
2020, 36(11): 2135-2144
doi: 10.11862/CJIC.2020.242
Abstract:
Two new dinuclear Ru(Ⅱ) complexes of 2-substituted 4, 6-di(2-pyridyl)-1, 3, 5-triazine, [Ru2(OBPT)(bpy)4] (PF6)3·3H2O·0.5CH3CH2OH (1) and[Ru2(HABPT)(bpy)4](PF6)4·0.5H2O (2), where bpy=2, 2'-bipyridine, HOBPT=4, 6-bi(2-pyridyl)-1, 3, 5-triazin-2-ol, HABPT=2-amino-4, 6-bi(2-pyridyl)-1, 3, 5-triazine, were synthesized and characterized. The X-ray crystal structures of the complexes have been determined, which show that 1 crystallizes in the monoclinic C2/c space group and in the rac-(ΔΔ) stereoisomeric form, while 2 in the orthorhombic Pca21 space group and in the meso-(ΔΛ) stereoisomeric form. Single-crystal structures indicate that the bridging ligand HOBPT in 1 is deprotonated while the ligand HABPT in 2 is not. The electrochemical and spectral properties of two complexes are significantly different. All data indicate the presence of electronic coupling between the individual metal centers bridged by the ligands in the complexes.CCDC: 2026074, 1; 2026075, 2.
Two new dinuclear Ru(Ⅱ) complexes of 2-substituted 4, 6-di(2-pyridyl)-1, 3, 5-triazine, [Ru2(OBPT)(bpy)4] (PF6)3·3H2O·0.5CH3CH2OH (1) and[Ru2(HABPT)(bpy)4](PF6)4·0.5H2O (2), where bpy=2, 2'-bipyridine, HOBPT=4, 6-bi(2-pyridyl)-1, 3, 5-triazin-2-ol, HABPT=2-amino-4, 6-bi(2-pyridyl)-1, 3, 5-triazine, were synthesized and characterized. The X-ray crystal structures of the complexes have been determined, which show that 1 crystallizes in the monoclinic C2/c space group and in the rac-(ΔΔ) stereoisomeric form, while 2 in the orthorhombic Pca21 space group and in the meso-(ΔΛ) stereoisomeric form. Single-crystal structures indicate that the bridging ligand HOBPT in 1 is deprotonated while the ligand HABPT in 2 is not. The electrochemical and spectral properties of two complexes are significantly different. All data indicate the presence of electronic coupling between the individual metal centers bridged by the ligands in the complexes.CCDC: 2026074, 1; 2026075, 2.
2020, 36(11): 2145-2156
doi: 10.11862/CJIC.2020.227
Abstract:
High thermal stability Ce0.65Zr0.35O2(CeZr) was prepared by soft-hard template method. The influence of calcination temperature on properties of Ce0.65Zr0.35O2 and its corresponding Pd based three-way catalyst (TWC) was investigated. The samples were analyzed by X-ray diffraction, surface area analysis, Raman spectrum, X-ray photoelectron spectroscopy, oxygen storage capacity and H2-temperature-programmed reduction. The results indicate that the structure and redox properties are strongly influenced by calcination temperature. The structure properties, for instance, BET (Brunaner-Emmett-Teller) surface area declined along with the rise of temperature, but the BET surface area of the sample calcinated at 1 000℃ was 61 m2·g-1, which was significantly higher than that calcinated direct in air at the same temperature. The OSC and reduction property of Ce0.65Zr0.35O2 increased with the rise of calcination temperature because of phase rearrangement at high temperature. The redox property of their corresponding catalysts decreased due to descending of Pd dispersion, which results in decline of three-way catalytic activity at last. Although high temperature sintering led to decrease of catalytic performance, the catalyst prepared by soft-hard template method calcinated at 1 000℃ still had excellent activity. The light-off temperature for C3H8, CO and NO was 274, 175 and 133℃, respectively, which was significantly lower than catalyst calcined direct in air at the same temperature. Redox property and dispersity of Pd are significant factors affecting activity of catalyst.
High thermal stability Ce0.65Zr0.35O2(CeZr) was prepared by soft-hard template method. The influence of calcination temperature on properties of Ce0.65Zr0.35O2 and its corresponding Pd based three-way catalyst (TWC) was investigated. The samples were analyzed by X-ray diffraction, surface area analysis, Raman spectrum, X-ray photoelectron spectroscopy, oxygen storage capacity and H2-temperature-programmed reduction. The results indicate that the structure and redox properties are strongly influenced by calcination temperature. The structure properties, for instance, BET (Brunaner-Emmett-Teller) surface area declined along with the rise of temperature, but the BET surface area of the sample calcinated at 1 000℃ was 61 m2·g-1, which was significantly higher than that calcinated direct in air at the same temperature. The OSC and reduction property of Ce0.65Zr0.35O2 increased with the rise of calcination temperature because of phase rearrangement at high temperature. The redox property of their corresponding catalysts decreased due to descending of Pd dispersion, which results in decline of three-way catalytic activity at last. Although high temperature sintering led to decrease of catalytic performance, the catalyst prepared by soft-hard template method calcinated at 1 000℃ still had excellent activity. The light-off temperature for C3H8, CO and NO was 274, 175 and 133℃, respectively, which was significantly lower than catalyst calcined direct in air at the same temperature. Redox property and dispersity of Pd are significant factors affecting activity of catalyst.
2020, 36(11): 2157-2168
doi: 10.11862/CJIC.2020.236
Abstract:
NBO charges of[M(H2O)6]3+ (M=Sc~Co), [Co (Ⅲ) L6] (L=F-, H2O, NH3, CN-), Al3O(OH)7(H2O)5 (Al3) and Al6O6(OH)6(H2O)5 (Al6) created based on α-Al2O3 were calculated at B3LYP/6-31++G(d, p) level of density functional theory (DFT). Except for[Co(NH3)6]3+, they all violate the principle of electroneutrality (EN) by having charges out-side the range of +1 to -1. In addition, the charge for the central metal ion is drastically influenced by the type of the coordination atoms, which is not included in the current EN principle. The charges of Co3+ in[CoF6]3- and[Co(CN)6]3- were found to be 1.639 and -1.360, respectively. When the ionic potential of the central atom increases, its charge would decrease. Based on our calculation, we predict the charge of Al in α-Al2O3 is 2.1±0.1.
NBO charges of[M(H2O)6]3+ (M=Sc~Co), [Co (Ⅲ) L6] (L=F-, H2O, NH3, CN-), Al3O(OH)7(H2O)5 (Al3) and Al6O6(OH)6(H2O)5 (Al6) created based on α-Al2O3 were calculated at B3LYP/6-31++G(d, p) level of density functional theory (DFT). Except for[Co(NH3)6]3+, they all violate the principle of electroneutrality (EN) by having charges out-side the range of +1 to -1. In addition, the charge for the central metal ion is drastically influenced by the type of the coordination atoms, which is not included in the current EN principle. The charges of Co3+ in[CoF6]3- and[Co(CN)6]3- were found to be 1.639 and -1.360, respectively. When the ionic potential of the central atom increases, its charge would decrease. Based on our calculation, we predict the charge of Al in α-Al2O3 is 2.1±0.1.
2020, 36(11): 2169-2178
doi: 10.11862/CJIC.2020.235
Abstract:
N-acetyl-L-cysteine (NALC) functionalized ZnFe2O4@SiO2 (ZnFe2O4@SiO2-NALC) was synthesized and exhibited simplicity, rapidity and high selectivity in the separation of chiral tyrosine (Tyr) enantiomers. The chiral nanocomposite of ZnFe2O4@SiO2-NALC was characterized by X-ray powder diffraction (XRD), infrared spectroscopy (FT-IR), energy dispersive X-ray spectroscopy (EDS), scanning electron microscopy (SEM), high resolution transmission electron microscopy (HRTEM) and vibrating sample magnetometer (VSM). This is the first synthesis of ZnFe2O4@SiO2-NALC for chiral recognition. The proposed optical spectroscopic techniques (UV-Vis spectrum and fluorescence spectra) showed excellent enantiospecificity for Tyr enantiomers. Furthermore, the experimental parameters such as the Tyr concentration and the pH values were optimized.
N-acetyl-L-cysteine (NALC) functionalized ZnFe2O4@SiO2 (ZnFe2O4@SiO2-NALC) was synthesized and exhibited simplicity, rapidity and high selectivity in the separation of chiral tyrosine (Tyr) enantiomers. The chiral nanocomposite of ZnFe2O4@SiO2-NALC was characterized by X-ray powder diffraction (XRD), infrared spectroscopy (FT-IR), energy dispersive X-ray spectroscopy (EDS), scanning electron microscopy (SEM), high resolution transmission electron microscopy (HRTEM) and vibrating sample magnetometer (VSM). This is the first synthesis of ZnFe2O4@SiO2-NALC for chiral recognition. The proposed optical spectroscopic techniques (UV-Vis spectrum and fluorescence spectra) showed excellent enantiospecificity for Tyr enantiomers. Furthermore, the experimental parameters such as the Tyr concentration and the pH values were optimized.
2020, 36(11): 2179-2188
doi: 10.11862/CJIC.2020.240
Abstract:
In this study, single-crystal ZnIn2S4 nanosheet arrays (NSAs) were synthesized via a facile hydrothermal route for photoelectrochemical (PEC) N2 fixation under a visible light irradiation. The Au nanoparticles (NPs) with average size of 5 nm were deposited onto the edges of ZnIn2S4 nanosheets through a photodeposition method, leading to both the enhancements of visible light harvesting and carrier separation. After optimizing the Au loading amounts, the PEC N2 fixation activity was enhanced significantly from 1.09 to 2.26 μg·cm-2·h-1, which is attributed to the enhancements of visible light absorption and carrier separation. Furthermore, a schematic model was used to clarify the mechanism as had been demonstrated by the photoluminescence (PL) and PEC results, respectively.
In this study, single-crystal ZnIn2S4 nanosheet arrays (NSAs) were synthesized via a facile hydrothermal route for photoelectrochemical (PEC) N2 fixation under a visible light irradiation. The Au nanoparticles (NPs) with average size of 5 nm were deposited onto the edges of ZnIn2S4 nanosheets through a photodeposition method, leading to both the enhancements of visible light harvesting and carrier separation. After optimizing the Au loading amounts, the PEC N2 fixation activity was enhanced significantly from 1.09 to 2.26 μg·cm-2·h-1, which is attributed to the enhancements of visible light absorption and carrier separation. Furthermore, a schematic model was used to clarify the mechanism as had been demonstrated by the photoluminescence (PL) and PEC results, respectively.
2020, 36(11): 2189-2196
doi: 10.11862/CJIC.2020.233
Abstract:
A complete amorphous and highly ordered Ce-Ti catalytic membrane was prepared for simultaneously removing the particulates and NOx. Results showed that the presence of Ce species suppressed the phase transformation of the anatase TiO2, consolidated the pore framework and well retained the ordered hexagonal pore structure. As a result, the highly ordered Ce0.2TiOx catalyst presented approximately 100% NO conversion in a wide temperature of 175~350℃ and satisfactory SO2 tolerance because of large surface and formation of the Ce-O-Ti species. Furthermore, the prepared Ce0.2TiOx catalytic membrane slightly enhanced the operating pressure drop and delivered an almost similar selective catalytic reduction (SCR) activity for NOx with the catalyst powder.
A complete amorphous and highly ordered Ce-Ti catalytic membrane was prepared for simultaneously removing the particulates and NOx. Results showed that the presence of Ce species suppressed the phase transformation of the anatase TiO2, consolidated the pore framework and well retained the ordered hexagonal pore structure. As a result, the highly ordered Ce0.2TiOx catalyst presented approximately 100% NO conversion in a wide temperature of 175~350℃ and satisfactory SO2 tolerance because of large surface and formation of the Ce-O-Ti species. Furthermore, the prepared Ce0.2TiOx catalytic membrane slightly enhanced the operating pressure drop and delivered an almost similar selective catalytic reduction (SCR) activity for NOx with the catalyst powder.
2020, 36(11): 2197-2204
doi: 10.11862/CJIC.2020.250
Abstract:
Hydrothermal assembly reactions of Zn(NO3)2·6H2O, 1, 5-bis-(2-methyl-imidazol)pentane (BMIP) and 5-hydroxyisophthalic acid (5-OHH2IP) or 5-bromoisophthalic acid (5-BrH2IP) ligands resulted in the formation of complexes[Zn(5-OHIP)(BMIP)]n (1) and[Zn(5-BrIP)(BMIP)]n (2), respectively. The resulting complexes were characterized by IR spectrum, elemental analysis and single-crystal X-ray diffraction. Crystal structure analysis shows that complex 1 crystallizes in the monoclinic system, space group P21/n with β=101.363(10)°. Complex 1 displays a two-dimensional layer net constructed by 5-hydroxyisophthalic acid and 1, 5-bis-(2-methyl-imidazol)pentane. For 2, 5-bromoisophthalic acid and 1, 5-bis-(2-methyl-imidazol)pentane link Zinc ion into a two-dimensional layers, which are pillared by the other BMIP ligands to result in the three-dimensional framework from another direction. Finally, it exhibits a fascinating three-fold interpenetrating net with dmp topology. Both complexes exhibit a strong photolu-minescence in the solid state at room temperature. Moreover, two complexes present good photocatalytic activities in methylene blue (MB) degradation reactions.CCDC: 1502156, 1; 1502157, 2.
Hydrothermal assembly reactions of Zn(NO3)2·6H2O, 1, 5-bis-(2-methyl-imidazol)pentane (BMIP) and 5-hydroxyisophthalic acid (5-OHH2IP) or 5-bromoisophthalic acid (5-BrH2IP) ligands resulted in the formation of complexes[Zn(5-OHIP)(BMIP)]n (1) and[Zn(5-BrIP)(BMIP)]n (2), respectively. The resulting complexes were characterized by IR spectrum, elemental analysis and single-crystal X-ray diffraction. Crystal structure analysis shows that complex 1 crystallizes in the monoclinic system, space group P21/n with β=101.363(10)°. Complex 1 displays a two-dimensional layer net constructed by 5-hydroxyisophthalic acid and 1, 5-bis-(2-methyl-imidazol)pentane. For 2, 5-bromoisophthalic acid and 1, 5-bis-(2-methyl-imidazol)pentane link Zinc ion into a two-dimensional layers, which are pillared by the other BMIP ligands to result in the three-dimensional framework from another direction. Finally, it exhibits a fascinating three-fold interpenetrating net with dmp topology. Both complexes exhibit a strong photolu-minescence in the solid state at room temperature. Moreover, two complexes present good photocatalytic activities in methylene blue (MB) degradation reactions.CCDC: 1502156, 1; 1502157, 2.
2020, 36(11): 2023-2030
doi: 10.11862/CJIC.2020.248
Abstract:
A series of novel bidentate ligands of fluoro phenanthrolines were designed and synthesized, which could formulate a series of heteroleptic copper photosensitizers CP1~CP4 with Cu(MeCN)4PF6 and Xantphos as P ligand. The photosensitive activities of this copper complex were researched in water reduction system, and the turnover number (TON) of hydrogen evolution was up to 896. The absorption spectrum and fluorescence emission spectrum of the copper complexes indicated the good stability in solution. The oxidation quenching is the main quenching pathway in water reduction system, which was confirmed by the fluorescence quenching experiments. Moreover, a preliminary explanation and discussion of the structure-activity relationship and the mechanism of photocatalytic hydrogen evolution from water were carried out.
A series of novel bidentate ligands of fluoro phenanthrolines were designed and synthesized, which could formulate a series of heteroleptic copper photosensitizers CP1~CP4 with Cu(MeCN)4PF6 and Xantphos as P ligand. The photosensitive activities of this copper complex were researched in water reduction system, and the turnover number (TON) of hydrogen evolution was up to 896. The absorption spectrum and fluorescence emission spectrum of the copper complexes indicated the good stability in solution. The oxidation quenching is the main quenching pathway in water reduction system, which was confirmed by the fluorescence quenching experiments. Moreover, a preliminary explanation and discussion of the structure-activity relationship and the mechanism of photocatalytic hydrogen evolution from water were carried out.
2020, 36(11): 2031-2040
doi: 10.11862/CJIC.2020.238
Abstract:
Using natural hydromagnesite as raw material, mesoporous reticular MgO with high specific surface area was prepared by the simple method of "calcination-hydration-calcination", and no reagent was added in the experimental process. The effects of MgO dosage, adsorption time, adsorption temperature and pH on the adsorption of lead ions in simulated wastewater by MgO were systematically studied, the adsorption mechanism was revealed, and the adsorption effect of MgO on various ions was investigated. The results showed that the MgO adsorbent had a high specific surface area of 188 m2·g-1 and a high pore volume of 0.85 cm3·g-1, with an average pore diameter of 12.33 nm. The adsorption kinetics and isotherm data are highly consistent with the pseudo-second-order model and Langmuir model, indicating the monolayer chemisorption of heavy metal ions. MgO mesoporous reticular structure exhibited high adsorption performance for Pb(Ⅱ), and the maximum adsorption capacity was up to 7 431.5 mg·g-1, which was far higher than other reported values based on MgO adsorbent, and the removal rate of Pb(Ⅱ) was over 99.8%. The adsorption mechanism is mainly due to hydroxyl functional groups and ion exchange between Mg and heavy metal ions on MgO surface. In addition, the MgO can adsorb various ions simultaneously, and has excellent adsorption performance on Cd, Cr, Ni, As, Co, P, Se, Be, Bi, Cu, Fe, Mn, Ⅴ, Zn and Al ions.
Using natural hydromagnesite as raw material, mesoporous reticular MgO with high specific surface area was prepared by the simple method of "calcination-hydration-calcination", and no reagent was added in the experimental process. The effects of MgO dosage, adsorption time, adsorption temperature and pH on the adsorption of lead ions in simulated wastewater by MgO were systematically studied, the adsorption mechanism was revealed, and the adsorption effect of MgO on various ions was investigated. The results showed that the MgO adsorbent had a high specific surface area of 188 m2·g-1 and a high pore volume of 0.85 cm3·g-1, with an average pore diameter of 12.33 nm. The adsorption kinetics and isotherm data are highly consistent with the pseudo-second-order model and Langmuir model, indicating the monolayer chemisorption of heavy metal ions. MgO mesoporous reticular structure exhibited high adsorption performance for Pb(Ⅱ), and the maximum adsorption capacity was up to 7 431.5 mg·g-1, which was far higher than other reported values based on MgO adsorbent, and the removal rate of Pb(Ⅱ) was over 99.8%. The adsorption mechanism is mainly due to hydroxyl functional groups and ion exchange between Mg and heavy metal ions on MgO surface. In addition, the MgO can adsorb various ions simultaneously, and has excellent adsorption performance on Cd, Cr, Ni, As, Co, P, Se, Be, Bi, Cu, Fe, Mn, Ⅴ, Zn and Al ions.
2020, 36(11): 2041-2047
doi: 10.11862/CJIC.2020.210
Abstract:
Hydroxyapatite (HA), chitosan (CS), ZnO and SiO2 suspensions were distributed by zonal electrophoresis, and then HA/CS/ZnO/SiO2 composite coating material on the Ti-based surface was obtained by electrophoretic deposition in a reverse electric field subsequently. An HA/ZnO/SiO2 coating material (Z1) was fabricated by calcination at 710℃ for 2 h. At the same time, another HA/ZnO/SiO2 coating material (E1) was directly prepared only by electrophoretic deposition for comparison. Both Si and Zn elements with a gradient distribution in the radial direction of the coating was found by X-ray energy spectrum analysis, which indicates that Z1 has certain gradient properties. Then, scanning electron microscope, powder X-ray diffraction and Fourier transform infrared spectroscopy were used to characterize the two coating materials. It was found that Z1 has more excellent properties than E1, mainly manifested in the bonding strength of Z1 and Ti substrate up to 31.2 MPa, and the degree of carbonated apatite on the surface of Z1 was more complete after 14 days of culture in HEPES simulated body fluid. In addition, the bacteriostatic effect test of Z1 showed that the bacteriostatic rates of Z1 powder against E. coli and S. aureus were up to 81.7% and 89.4%, respectively.
Hydroxyapatite (HA), chitosan (CS), ZnO and SiO2 suspensions were distributed by zonal electrophoresis, and then HA/CS/ZnO/SiO2 composite coating material on the Ti-based surface was obtained by electrophoretic deposition in a reverse electric field subsequently. An HA/ZnO/SiO2 coating material (Z1) was fabricated by calcination at 710℃ for 2 h. At the same time, another HA/ZnO/SiO2 coating material (E1) was directly prepared only by electrophoretic deposition for comparison. Both Si and Zn elements with a gradient distribution in the radial direction of the coating was found by X-ray energy spectrum analysis, which indicates that Z1 has certain gradient properties. Then, scanning electron microscope, powder X-ray diffraction and Fourier transform infrared spectroscopy were used to characterize the two coating materials. It was found that Z1 has more excellent properties than E1, mainly manifested in the bonding strength of Z1 and Ti substrate up to 31.2 MPa, and the degree of carbonated apatite on the surface of Z1 was more complete after 14 days of culture in HEPES simulated body fluid. In addition, the bacteriostatic effect test of Z1 showed that the bacteriostatic rates of Z1 powder against E. coli and S. aureus were up to 81.7% and 89.4%, respectively.
2020, 36(11): 2048-2054
doi: 10.11862/CJIC.2020.228
Abstract:
An Ag-loaded KTa1-xNbxO3-BaTiO3 composite (Ag/KTN-BT) was prepared by light reduction method and then introduced into the P(VDF-TrFE-CTFE) matrix. The Ag/KTN-BT nanoparticles were uniformly dispersed in the polymer matrix without obvious pores and cracks, and the obtained nanocomposite film exhibited good flexibility. The introduction of Ag nanoparticles, on the one hand, introduces additional interfaces in the polymer matrix, leading to enhanced interface polarization and the dielectric constant of the composite; on the other hand, due to the quantum size effect and coulomb blockage effect of the silver nanoparticles, the composite maintains low dielectric loss. Typically, the dielectric constant of the composite filled with 20% (volume fraction) Ag/KTN-BT reached 125 at 100 Hz, in contrast to 37 for pristine P(VDF-TrFE-CTFE) polymer. Moreover, the composite remained low dielectric loss 0.12. Compared with the KTN-BT-based composite, Ag/KTN-BT-based composites also showed better dielectric properties.
An Ag-loaded KTa1-xNbxO3-BaTiO3 composite (Ag/KTN-BT) was prepared by light reduction method and then introduced into the P(VDF-TrFE-CTFE) matrix. The Ag/KTN-BT nanoparticles were uniformly dispersed in the polymer matrix without obvious pores and cracks, and the obtained nanocomposite film exhibited good flexibility. The introduction of Ag nanoparticles, on the one hand, introduces additional interfaces in the polymer matrix, leading to enhanced interface polarization and the dielectric constant of the composite; on the other hand, due to the quantum size effect and coulomb blockage effect of the silver nanoparticles, the composite maintains low dielectric loss. Typically, the dielectric constant of the composite filled with 20% (volume fraction) Ag/KTN-BT reached 125 at 100 Hz, in contrast to 37 for pristine P(VDF-TrFE-CTFE) polymer. Moreover, the composite remained low dielectric loss 0.12. Compared with the KTN-BT-based composite, Ag/KTN-BT-based composites also showed better dielectric properties.
2020, 36(11): 2055-2062
doi: 10.11862/CJIC.2020.232
Abstract:
Carbon nanodots (CDs) were prepared through a one-step pyrolysis procedure using cysteine as precursor. The as-prepared nanomaterials were characterized by transmission electron microscope (TEM), dynamic light scattering (DLS), X-ray photoelectron spectroscopy (XPS), ultraviolet-visible absorption spectrum (UV-Vis) and fluorescence spectrum (FL). It was turned out that the average size of as-prepared CDs was 3.12 nm and they showed good fluorescence property. Silver ions can bind to the CDs and effectively quench the fluorescence through photoinduced electron transfer (PET). Further, benefitting from its coordination with heavy metal ions, penicillamine combines with Ag+ and makes the latter leave the surface of the carbon dots to achieve fluorescence recovery. Based on this, an Ag+ assisted CDs fluorescent turn-on probe was established to recognize penicillamine. The linear range of this method was 8~500 μmol·L-1 with a detection limit of 5.62 μmol·L-1. The penicillamine content in urine sample was detected and the recovery was in the range of 97.17%~102.05%.
Carbon nanodots (CDs) were prepared through a one-step pyrolysis procedure using cysteine as precursor. The as-prepared nanomaterials were characterized by transmission electron microscope (TEM), dynamic light scattering (DLS), X-ray photoelectron spectroscopy (XPS), ultraviolet-visible absorption spectrum (UV-Vis) and fluorescence spectrum (FL). It was turned out that the average size of as-prepared CDs was 3.12 nm and they showed good fluorescence property. Silver ions can bind to the CDs and effectively quench the fluorescence through photoinduced electron transfer (PET). Further, benefitting from its coordination with heavy metal ions, penicillamine combines with Ag+ and makes the latter leave the surface of the carbon dots to achieve fluorescence recovery. Based on this, an Ag+ assisted CDs fluorescent turn-on probe was established to recognize penicillamine. The linear range of this method was 8~500 μmol·L-1 with a detection limit of 5.62 μmol·L-1. The penicillamine content in urine sample was detected and the recovery was in the range of 97.17%~102.05%.
2020, 36(11): 2063-2070
doi: 10.11862/CJIC.2020.247
Abstract:
Cadmium(Ⅱ) and lead(Ⅱ) based three-dimensional metal-organic frameworks (MOFs), namely {[Cd(L)(H2O)2]· 1.5H2O}n (1) and[Pb(L)·H2O]n (2), have been obtained through hydrothermal synthesis method using dimethyl 5-(2-hydroxyethoxy) isophthalic acid (Me2L) as a precursor and metal acetate. The crystal structures of two MOFs were revealed by single-crystal X-ray diffraction analysis and further confirmed by infrared spectrum (IR) and element analysis (EA). The XRD analysis of the MOFs ensured the single-crystal phase of the MOFs. The fluorescence emission property of two MOFs and H2L in the solid-state was investigated. Compared to the emission spectrum of Me2L, the emission maximum of compounds 1 and 2 all had red-shift but 2 shifted more severe.CCDC: 1986790, 1;1986793, 2.
Cadmium(Ⅱ) and lead(Ⅱ) based three-dimensional metal-organic frameworks (MOFs), namely {[Cd(L)(H2O)2]· 1.5H2O}n (1) and[Pb(L)·H2O]n (2), have been obtained through hydrothermal synthesis method using dimethyl 5-(2-hydroxyethoxy) isophthalic acid (Me2L) as a precursor and metal acetate. The crystal structures of two MOFs were revealed by single-crystal X-ray diffraction analysis and further confirmed by infrared spectrum (IR) and element analysis (EA). The XRD analysis of the MOFs ensured the single-crystal phase of the MOFs. The fluorescence emission property of two MOFs and H2L in the solid-state was investigated. Compared to the emission spectrum of Me2L, the emission maximum of compounds 1 and 2 all had red-shift but 2 shifted more severe.CCDC: 1986790, 1;1986793, 2.
2020, 36(11): 2071-2079
doi: 10.11862/CJIC.2020.229
Abstract:
We used density functional theory (DFT) to study the stable geometry structures and electronic structures of X-doped (X=B, Al and Ga) single-walled (14, 0) silicon nanotubes (SiNTs). The results show that the stable structure of SiNTs is a pucked tubular structure; the stability of SiNTs can be improved by doping with B, Al and Ga. Intrinsic (14, 0) SiNTs is a narrow band-gap metal materials. The band gaps of SiNTs become wider, and realizes the transition from metal to semiconductor by doping with B, Al and Ga. With the atomic number of group Ⅲ elements increases, the stability of its doping system continues to decrease, and the corresponding band gap also decreases. B, Al and Ga doped single-wall zigzag (14, 0) SiNTs have nearly uniform optical properties, which have strong optical absorption for ultraviolet light and a good improvement on infrared and visible light absorption.
We used density functional theory (DFT) to study the stable geometry structures and electronic structures of X-doped (X=B, Al and Ga) single-walled (14, 0) silicon nanotubes (SiNTs). The results show that the stable structure of SiNTs is a pucked tubular structure; the stability of SiNTs can be improved by doping with B, Al and Ga. Intrinsic (14, 0) SiNTs is a narrow band-gap metal materials. The band gaps of SiNTs become wider, and realizes the transition from metal to semiconductor by doping with B, Al and Ga. With the atomic number of group Ⅲ elements increases, the stability of its doping system continues to decrease, and the corresponding band gap also decreases. B, Al and Ga doped single-wall zigzag (14, 0) SiNTs have nearly uniform optical properties, which have strong optical absorption for ultraviolet light and a good improvement on infrared and visible light absorption.
2020, 36(11): 2080-2086
doi: 10.11862/CJIC.2020.231
Abstract:
Single crystal Ti4Eu2O4(OOCC6H5)14 (denoted as POTi4Eu2) was prepared by the solvothermal method, via the strategy of concurrently fully carboxylate-coordinating and the lanthanide-Eu(Ⅲ)-ion-doping. Characterizations of POTi4Eu2 have been performed by elemental analysis, thermogravimetric analysis, solid-state UV-Vis absorption spectroscopy and FT-IR, and its particular optical properties have been shown by liquid-state fluorescence spectra, and solid-state fluorescence lifetime. The structure of POTi4Eu2 contains four TiO6 octahedrons, two EuO8 dodeca-hedrons and 14 bridged bidentate benzoic acid ligands. The cluster core Ti4Eu2 is stabilized by 14 benzoic acid ligands. The 14 benzoic acid ligands are coordinated by bidentate bridges and are distributed around the core clusters of the titanium oxide cluster. The adjacent clusters are bridged by benzoic acid ligands to form a one-dimensional chain structure. Thermogravimetric analysis data show that the structure of single crystal POTi4Eu2 could remain stable within 256℃ in air. The average fluorescence lifetime of single crystal POTi4Eu2 was 1.63 ms.CCDC: 1997261.
Single crystal Ti4Eu2O4(OOCC6H5)14 (denoted as POTi4Eu2) was prepared by the solvothermal method, via the strategy of concurrently fully carboxylate-coordinating and the lanthanide-Eu(Ⅲ)-ion-doping. Characterizations of POTi4Eu2 have been performed by elemental analysis, thermogravimetric analysis, solid-state UV-Vis absorption spectroscopy and FT-IR, and its particular optical properties have been shown by liquid-state fluorescence spectra, and solid-state fluorescence lifetime. The structure of POTi4Eu2 contains four TiO6 octahedrons, two EuO8 dodeca-hedrons and 14 bridged bidentate benzoic acid ligands. The cluster core Ti4Eu2 is stabilized by 14 benzoic acid ligands. The 14 benzoic acid ligands are coordinated by bidentate bridges and are distributed around the core clusters of the titanium oxide cluster. The adjacent clusters are bridged by benzoic acid ligands to form a one-dimensional chain structure. Thermogravimetric analysis data show that the structure of single crystal POTi4Eu2 could remain stable within 256℃ in air. The average fluorescence lifetime of single crystal POTi4Eu2 was 1.63 ms.CCDC: 1997261.
2020, 36(11): 2087-2092
doi: 10.11862/CJIC.2020.230
Abstract:
Under solvothermal condition, 5-(hydroxymethyl) isophthalic acid (H2HIPA) and Zn(Ⅱ) ions reacted with 1, 4-bis(2-methyl-1H-imidazol-1-yl) benzene (1, 4-BMIB) and 1, 2-di(pyridin-4-yl)ethene (dpee) to obtain two coordination polymers[Zn(HIPA)(1, 4-BMIB)]n (1) and {[Zn(HIPA)(dpee)]·0.5dpee}n (2), respectively. Single crystal X-ray diffraction analyses reveal that Zn(Ⅱ) center adopts a slightly distorted tetrahedral geometry in complex 1. And then, Zn (Ⅱ) ions are further connected together by HIPA2- and 1, 4-BMIB ligands to form a 3D framework with nano-channels, which is up to 1.2 nm×2.0 nm. For such a very empty framework, structural interpenetration is difficult to avoid. Further analysis finds that the whole framework of complex 1 is a 4-fold interpenetration structure. From a topological viewpoint, the Zn(Ⅱ) ions are 4-connected nodes, whilst HIPA2- and 1, 4-BMIB ligands are simple linkers. So, the whole framework of 1 is topologically represented as a 4-connected dia net. Although the Zn(Ⅱ) center in complex 2 has a different pentagonal bipyramid model, the HIPA2- and dpee as simple linkers are connected by two Zn (Ⅱ) centers, respectively. Therefore, the final framework of 2 is still a 4-fold interpenetration dia net like 1. Furthermore, the dpee not only participates in constructing the framework as auxiliary ligand, but also exists in complex 2 as guest molecule. UV-Vis spectra showed that complexes 1 and 2 had strong absorption spectra in ultraviolet region, while solid fluorescence measurements revealed that they possessed blue fluorescence properties with emission peaks at about 414 and 440 nm, respectively.CCDC: 2000801, 1; 2000802, 2.
Under solvothermal condition, 5-(hydroxymethyl) isophthalic acid (H2HIPA) and Zn(Ⅱ) ions reacted with 1, 4-bis(2-methyl-1H-imidazol-1-yl) benzene (1, 4-BMIB) and 1, 2-di(pyridin-4-yl)ethene (dpee) to obtain two coordination polymers[Zn(HIPA)(1, 4-BMIB)]n (1) and {[Zn(HIPA)(dpee)]·0.5dpee}n (2), respectively. Single crystal X-ray diffraction analyses reveal that Zn(Ⅱ) center adopts a slightly distorted tetrahedral geometry in complex 1. And then, Zn (Ⅱ) ions are further connected together by HIPA2- and 1, 4-BMIB ligands to form a 3D framework with nano-channels, which is up to 1.2 nm×2.0 nm. For such a very empty framework, structural interpenetration is difficult to avoid. Further analysis finds that the whole framework of complex 1 is a 4-fold interpenetration structure. From a topological viewpoint, the Zn(Ⅱ) ions are 4-connected nodes, whilst HIPA2- and 1, 4-BMIB ligands are simple linkers. So, the whole framework of 1 is topologically represented as a 4-connected dia net. Although the Zn(Ⅱ) center in complex 2 has a different pentagonal bipyramid model, the HIPA2- and dpee as simple linkers are connected by two Zn (Ⅱ) centers, respectively. Therefore, the final framework of 2 is still a 4-fold interpenetration dia net like 1. Furthermore, the dpee not only participates in constructing the framework as auxiliary ligand, but also exists in complex 2 as guest molecule. UV-Vis spectra showed that complexes 1 and 2 had strong absorption spectra in ultraviolet region, while solid fluorescence measurements revealed that they possessed blue fluorescence properties with emission peaks at about 414 and 440 nm, respectively.CCDC: 2000801, 1; 2000802, 2.
2020, 36(11): 2093-2099
doi: 10.11862/CJIC.2020.225
Abstract:
CuInS2 quantum dots with semiconductor effect were prepared by improved thermal decomposition method, and the uniform size of quantum dots was 4.2 nm. The Au/CuInS2/FTO device exhibited typical bipolar resistance characteristics, with an ON/OFF switching ratio of about 103, an ON voltage of -3.8 V and an OFF voltage of 4 V. The resistance mechanism of the device was studied by linear fitting the I-V characteristic curve of the device. The device has space-limiter charge (SCLC) conduction mechanism in high resistance state and ohmic conduction mechanism in low resistance state. The resistance characteristic of the device is mainly caused by the charge being trapped by the potential well generated by the defect in the CuInS2 film. The charge is moved in the trap by adjusting the height of the trap barrier, which results in the generation and fracture of the conductive path, so that the device is in a high resistance state and a low resistance state.
CuInS2 quantum dots with semiconductor effect were prepared by improved thermal decomposition method, and the uniform size of quantum dots was 4.2 nm. The Au/CuInS2/FTO device exhibited typical bipolar resistance characteristics, with an ON/OFF switching ratio of about 103, an ON voltage of -3.8 V and an OFF voltage of 4 V. The resistance mechanism of the device was studied by linear fitting the I-V characteristic curve of the device. The device has space-limiter charge (SCLC) conduction mechanism in high resistance state and ohmic conduction mechanism in low resistance state. The resistance characteristic of the device is mainly caused by the charge being trapped by the potential well generated by the defect in the CuInS2 film. The charge is moved in the trap by adjusting the height of the trap barrier, which results in the generation and fracture of the conductive path, so that the device is in a high resistance state and a low resistance state.
2020, 36(11): 2100-2112
doi: 10.11862/CJIC.2020.207
Abstract:
Series of Ag-UiO-66-NH2 (X-Ag-UiO-66-NH2, X=irradiation time) composites were prepared by in-situ photochemical reduction deposition method with high power Xe lamp. The morphology and structure of X-Ag-UiO-66-NH2 were characterized by powder X-ray diffraction (PXRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), UV-visible diffuse-reflectance spectra (UV-Vis DRS) and X-ray photoelectron spectroscopy (XPS). The performances of X-Ag-UiO-66-NH2 toward photocatalytic Cr(Ⅵ) reduction were investigated under low power LED visible light. The reduction efficiency of Cr(Ⅵ) (initial concentration of 10 mg·L-1) over 30 min-Ag-UiO-66-NH 2 was 94% upon the irradiation low-power LED irradiation for 40 min, and Cr(Ⅵ) can be completely reduced after 60 min irradiation. The effects of different pH values (pH=2, 3, 4, 6 and 8), small organic acids (oxalic acid, citric acid and tartaric acid) and foreign ions (lake water, tap water and simulated seawater) on the photocatalytic reduction of Cr(Ⅵ) by 30 min-Ag-UiO-66-NH2 were studied. 30 min-Ag-UiO-66-NH2 can achieve 100% Cr(Ⅵ) reduction within 60 min after five running, indicating that it had good reusability and stability. The mechanism of photocatalytic Cr(Ⅵ) reduction was studied and verified by photoluminescence technology (PL), electrochemical test, electron spin resonance (ESR) and active species capture experiments. In all, the Ag nanoparticles formed by in-situ photochemical reduction deposition can improve the charge transfer at the interface of Ag-UiO-66-NH2 composite and promote the photocatalytic efficiency.
Series of Ag-UiO-66-NH2 (X-Ag-UiO-66-NH2, X=irradiation time) composites were prepared by in-situ photochemical reduction deposition method with high power Xe lamp. The morphology and structure of X-Ag-UiO-66-NH2 were characterized by powder X-ray diffraction (PXRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), UV-visible diffuse-reflectance spectra (UV-Vis DRS) and X-ray photoelectron spectroscopy (XPS). The performances of X-Ag-UiO-66-NH2 toward photocatalytic Cr(Ⅵ) reduction were investigated under low power LED visible light. The reduction efficiency of Cr(Ⅵ) (initial concentration of 10 mg·L-1) over 30 min-Ag-UiO-66-NH 2 was 94% upon the irradiation low-power LED irradiation for 40 min, and Cr(Ⅵ) can be completely reduced after 60 min irradiation. The effects of different pH values (pH=2, 3, 4, 6 and 8), small organic acids (oxalic acid, citric acid and tartaric acid) and foreign ions (lake water, tap water and simulated seawater) on the photocatalytic reduction of Cr(Ⅵ) by 30 min-Ag-UiO-66-NH2 were studied. 30 min-Ag-UiO-66-NH2 can achieve 100% Cr(Ⅵ) reduction within 60 min after five running, indicating that it had good reusability and stability. The mechanism of photocatalytic Cr(Ⅵ) reduction was studied and verified by photoluminescence technology (PL), electrochemical test, electron spin resonance (ESR) and active species capture experiments. In all, the Ag nanoparticles formed by in-situ photochemical reduction deposition can improve the charge transfer at the interface of Ag-UiO-66-NH2 composite and promote the photocatalytic efficiency.
2020, 36(11): 2113-2123
doi: 10.11862/CJIC.2020.226
Abstract:
ZnO nanoparticles anchored submicron-diameter carbon fibers (denoted as ZnO/SDCFs) composites were synthesized by electrospinning combined with hydrothermal method. The influences of pH value of the reaction solution on the structure, composition, electromagnetic (EM) characteristics and microwave absorption properties of the products are investigated in details. The results show that with increasing pH value of the solution, the complex permittivity, dielectric loss and EM attenuation ability of as-obtained ZnO/SDCFs composites decrease monotonously due to the increase of ZnO content in composites, in contrast, the EM impedance matching is improved gradually. Compared as the pure SDCFs, the microwave absorption capacities of ZnO/SDCFs composites are enhanced at different degrees. Among all the samples, the ZnO/SDCFs-8 composite prepared in solution with a pH value of 8 owns the best overall absorption properties, which is mainly attributed to the better balance between its EM attenuation capability and impedance matching. For the paraffin composites with only 2.5% (mass fraction) ZnO/SDCFs-8 as absorbent, the minimum reflection loss (RL) reached -44.1 dB at 17.7 GHz, and the effective absorption bandwidth with RL values less than -10 dB was as wide as 6.1 GHz ranging from 11.9 to 18 GHz at a relatively thin matching thickness of 1.7 mm. Moreover, the effective absorption bandwidth can be further increased to 11.8 GHz (6.2~18 GHz) when the absorber thickness was 3.0 mm.
ZnO nanoparticles anchored submicron-diameter carbon fibers (denoted as ZnO/SDCFs) composites were synthesized by electrospinning combined with hydrothermal method. The influences of pH value of the reaction solution on the structure, composition, electromagnetic (EM) characteristics and microwave absorption properties of the products are investigated in details. The results show that with increasing pH value of the solution, the complex permittivity, dielectric loss and EM attenuation ability of as-obtained ZnO/SDCFs composites decrease monotonously due to the increase of ZnO content in composites, in contrast, the EM impedance matching is improved gradually. Compared as the pure SDCFs, the microwave absorption capacities of ZnO/SDCFs composites are enhanced at different degrees. Among all the samples, the ZnO/SDCFs-8 composite prepared in solution with a pH value of 8 owns the best overall absorption properties, which is mainly attributed to the better balance between its EM attenuation capability and impedance matching. For the paraffin composites with only 2.5% (mass fraction) ZnO/SDCFs-8 as absorbent, the minimum reflection loss (RL) reached -44.1 dB at 17.7 GHz, and the effective absorption bandwidth with RL values less than -10 dB was as wide as 6.1 GHz ranging from 11.9 to 18 GHz at a relatively thin matching thickness of 1.7 mm. Moreover, the effective absorption bandwidth can be further increased to 11.8 GHz (6.2~18 GHz) when the absorber thickness was 3.0 mm.
