Defect engineering could provide new ideas for the design of transition metal disulfide electromagnetic wave(EMW)absorbers with high performance.Since the effects of dipoles on impedance matching and EMW absorption ar...Defect engineering could provide new ideas for the design of transition metal disulfide electromagnetic wave(EMW)absorbers with high performance.Since the effects of dipoles on impedance matching and EMW absorption are crucial for the development of novel absorbers,the polarization attenuation depen-dence on defect engineering should be understood at micro-and macro-scales.In this paper,it is found that the defect-rich WS2 nanoflowers synthesized by the cold plasma method possess excellent EMW absorption properties.Cold plasma treatment of materials is easy to perform and maintains the original shape of the material to a high degree.The formation of defects results in abundant electrochemically ac-tive sites,increased multiple reflection losses,improved dielectric properties and impedance matching in the materials.The RL_(min) of the defect-rich material with a thickness of 3.19 mm is as high as−54.36 dB at 8.16 GHz,and the effective absorption bandwidth is 4.72 GHz.The results reveal that the formation of defective vacancies enhances the effects of dipole polarization of the material on improving its EMW ab-sorption properties.Thus,this work provides not only a facile preparation route for novel EMW-absorbing materials,but also a new strategy for tunning defects in transition metal disulfides.展开更多
As electromagnetic technology advances and demand for electronic devices grows,concerns about electromagnetic pollution intensify.This has spurred focused research on innovative electromagnetic absorbers,particularly ...As electromagnetic technology advances and demand for electronic devices grows,concerns about electromagnetic pollution intensify.This has spurred focused research on innovative electromagnetic absorbers,particularly chalcogenides,noted for their superior absorption capabilities.In this study,we successfully synthesize 3R–TaS_(2)nanosheets using a straightforward calcination method for the first time.These nanosheets exhibit significant absorption capabilities in both the C-band(4–8 GHz)and Ku-band(12–18 GHz)frequency ranges.By optimizing the calcination process,the complex permittivity of TaS_(2)is enhanced,specifically for those synthesized at 1000℃for 24 h.The nanosheets possess dual-band absorption properties,with a notable minimum reflection loss(RLmin)of41.4 dB in the C-band,and an average absorption intensity exceeding 10 dB in C-and Ku-bands,in the absorbers with a thickness of 5.6 mm.Additionally,the 3R–TaS_(2)nanosheets are demonstrated to have an effective absorption bandwidth of 5.04 GHz(3.84–8.88 GHz)in the absorbers with thicknesses of 3.5–5.5 mm.The results highlight the multiple reflection effects in 3R–TaS_(2)as caused by their stacked structures,which could be promising low-frequency absorbers.展开更多
Homogeneous heterogeneous(heterophase)interfaces regulated with low energy barriers have a fast response to applied electric fields and could provide a unique interfacial polarization,which facilitate the transport of...Homogeneous heterogeneous(heterophase)interfaces regulated with low energy barriers have a fast response to applied electric fields and could provide a unique interfacial polarization,which facilitate the transport of electrons across the substrate.Such regulation on the interfaces is effective in modulating electromagnetic wave absorbing materials.Herein,we construct NbS_(2)–NiS_(2)heterostructures with NiS_(2)nanoparticles uniformly grown in NbS_(2)hollow nanospheres,and such particular structure enhances the interfacial polarization.The strong electron transfer at the interface promotes electron transport throughout the material,which results in less scattering,promotes conduct ion loss and dielectric polarization relaxation,improves dielectric loss,and results in a good impedance matching of the material.Consequently,the absorbing band may be successful tuned.By regulating the amount of NiS_(2),the heterogeneous interface is finely alternated so that the overall wave-absorbing performance is shifted to lower frequencies.With a NiS_(2)content of 15 wt%and an absorber thickness of 1.84 mm,the minimum reflection loss at 14.56 GHz is53.1 dB,and the effective absorption bandwidth is 5.04 GHz;more importantly,the minimum reflection loss in different bands is20 dB,and the microwave energy absorption rate reaches 99%when the thickness is about 1.5–4.5 mm.This work demonstrates the construction of homogeneous heterostructures is effective in improving the electromagnetic absorption properties,providing guideline for the synthesis of highly efficient electromagnetic absorbing materials.展开更多
Comprehensive Summary Isochromanone is the core structure of many bioactive compounds.Direct oxidation of isochromans is one of leading methods for the construction of isochromanones,while most established processes r...Comprehensive Summary Isochromanone is the core structure of many bioactive compounds.Direct oxidation of isochromans is one of leading methods for the construction of isochromanones,while most established processes remain suffering from the use of environmentally unfriendly metal oxidants,harsh reaction conditions,and the difficulty in catalyst recycling and product separation.Herein,we report a convenient,cost-effective,and green method for the synthesis of high-value added isochromanones via isochroman oxidations with O_(2) by a novel heterogeneous vanadium cluster catalyst(Cat.1)under mild conditions.This reaction protocol demonstrates high catalytic activity with good catalyst recyclability and reusability for a wide scope of substrates.展开更多
基金supported by the National Nat-ural Science Foundation of China(Nos.52372289,52102368,52072192 and 51977009)the Regional Joint Fund for Basic Re-search and Applied Basic Research of Guangdong Province(No.2020A1515110905)+1 种基金the Guangdong Special Fund for Key Areas(No.20237DZX3042)the Shenzhen Stable Support Project.
文摘Defect engineering could provide new ideas for the design of transition metal disulfide electromagnetic wave(EMW)absorbers with high performance.Since the effects of dipoles on impedance matching and EMW absorption are crucial for the development of novel absorbers,the polarization attenuation depen-dence on defect engineering should be understood at micro-and macro-scales.In this paper,it is found that the defect-rich WS2 nanoflowers synthesized by the cold plasma method possess excellent EMW absorption properties.Cold plasma treatment of materials is easy to perform and maintains the original shape of the material to a high degree.The formation of defects results in abundant electrochemically ac-tive sites,increased multiple reflection losses,improved dielectric properties and impedance matching in the materials.The RL_(min) of the defect-rich material with a thickness of 3.19 mm is as high as−54.36 dB at 8.16 GHz,and the effective absorption bandwidth is 4.72 GHz.The results reveal that the formation of defective vacancies enhances the effects of dipole polarization of the material on improving its EMW ab-sorption properties.Thus,this work provides not only a facile preparation route for novel EMW-absorbing materials,but also a new strategy for tunning defects in transition metal disulfides.
基金supported by the National Natural Science Foundation of China(52372289,52102368,52072192 and 51977009)Regional Joint Fund for Basic Research and Applied Basic Research of Guangdong Province(No.2020A1515110905)+1 种基金Guangdong Special Fund for key Areas(20237DZX3042)Shenzhen Stable Support Project.
文摘As electromagnetic technology advances and demand for electronic devices grows,concerns about electromagnetic pollution intensify.This has spurred focused research on innovative electromagnetic absorbers,particularly chalcogenides,noted for their superior absorption capabilities.In this study,we successfully synthesize 3R–TaS_(2)nanosheets using a straightforward calcination method for the first time.These nanosheets exhibit significant absorption capabilities in both the C-band(4–8 GHz)and Ku-band(12–18 GHz)frequency ranges.By optimizing the calcination process,the complex permittivity of TaS_(2)is enhanced,specifically for those synthesized at 1000℃for 24 h.The nanosheets possess dual-band absorption properties,with a notable minimum reflection loss(RLmin)of41.4 dB in the C-band,and an average absorption intensity exceeding 10 dB in C-and Ku-bands,in the absorbers with a thickness of 5.6 mm.Additionally,the 3R–TaS_(2)nanosheets are demonstrated to have an effective absorption bandwidth of 5.04 GHz(3.84–8.88 GHz)in the absorbers with thicknesses of 3.5–5.5 mm.The results highlight the multiple reflection effects in 3R–TaS_(2)as caused by their stacked structures,which could be promising low-frequency absorbers.
基金supported by the National Natural Science Foundation of China(52372289,52102368,52072192 and 51977009)Regional Joint Fund for Basic Research and Applied Basic Research of Guangdong Province(No.2020A1515110905)+1 种基金Guangdong Special Fund for key Areas(20237DZX3042)Shenzhen Stable Support Project and the Fundamental Research Fund of Heilongjiang Provincial University(145309101)。
文摘Homogeneous heterogeneous(heterophase)interfaces regulated with low energy barriers have a fast response to applied electric fields and could provide a unique interfacial polarization,which facilitate the transport of electrons across the substrate.Such regulation on the interfaces is effective in modulating electromagnetic wave absorbing materials.Herein,we construct NbS_(2)–NiS_(2)heterostructures with NiS_(2)nanoparticles uniformly grown in NbS_(2)hollow nanospheres,and such particular structure enhances the interfacial polarization.The strong electron transfer at the interface promotes electron transport throughout the material,which results in less scattering,promotes conduct ion loss and dielectric polarization relaxation,improves dielectric loss,and results in a good impedance matching of the material.Consequently,the absorbing band may be successful tuned.By regulating the amount of NiS_(2),the heterogeneous interface is finely alternated so that the overall wave-absorbing performance is shifted to lower frequencies.With a NiS_(2)content of 15 wt%and an absorber thickness of 1.84 mm,the minimum reflection loss at 14.56 GHz is53.1 dB,and the effective absorption bandwidth is 5.04 GHz;more importantly,the minimum reflection loss in different bands is20 dB,and the microwave energy absorption rate reaches 99%when the thickness is about 1.5–4.5 mm.This work demonstrates the construction of homogeneous heterostructures is effective in improving the electromagnetic absorption properties,providing guideline for the synthesis of highly efficient electromagnetic absorbing materials.
基金the National Natural Science Foundation of China(22171122)the Liaoning Revitalization Talents Program(XLYC2007130)Talent Scientific Research Fund of Liaoning Petrochemical University(2016XJL-019).
文摘Comprehensive Summary Isochromanone is the core structure of many bioactive compounds.Direct oxidation of isochromans is one of leading methods for the construction of isochromanones,while most established processes remain suffering from the use of environmentally unfriendly metal oxidants,harsh reaction conditions,and the difficulty in catalyst recycling and product separation.Herein,we report a convenient,cost-effective,and green method for the synthesis of high-value added isochromanones via isochroman oxidations with O_(2) by a novel heterogeneous vanadium cluster catalyst(Cat.1)under mild conditions.This reaction protocol demonstrates high catalytic activity with good catalyst recyclability and reusability for a wide scope of substrates.
