MoS_(2) wrapped MOF-derived N-doped carbon nanocomposite with wideband electromagnetic wave absorption

Designing electromagnetic wave absorption(EMWA)materials with wide bandwidth,strong absorption,and light weight is still a great challenge for practical applications.Herein,the novel nitrogen doped carbon(NDC)/MoS_(2) composite with rationally designed composition and structure was developed.The NDC particles were introduced into MoS_(2) nanosheets through the calcination of ZIF-8 precursor and consequent hydrothermal process.A series of characterizations were carried out to investigate the physical properties of the as-prepared nanocomposites.The NDC particles exhibited the shape of rhombic dodecahedron with the size of about 500 nm,which were decorated on flower-shaped MoS_(2) with the size of about 3μm.With the increasing NDC content,the absorbing properties of NDC/MoS_(2) composites increased firstly and then decreased.The features of NDC/MoS_(2) composite including interconnected porous structure,nitrogen dopant,and appropriate electrical conductivity gave rise to the polarization,multiple reflection,multiple scattering,and impedance matching,resulting in the outstanding EMWA performance.With a filler loading ratio of 30 wt.%,the optimized EMWA property can be achieved when the mass ratio of NDC to MoS_(2) was adjusted to be 1:1.At a coating thickness of 3.0 mm,the effective EMWA bandwidth(<−10 dB)reached 6.08 GHz(8.56–14.64 GHz).These satisfactory achievements provide a way for the reasonable design of high-performance EMWA and new ideas for future research on wideband EMWA.

Stabilizing photo-induced vacancy defects in MOF matrix for highperformance SERS detection

Photo-induced vacancy defects are employed strategically to imbue semiconductors with enhanced performance characteristics for many important applications such as surface-enhanced Raman scattering(SERS)sensing,photocatalysis,and photovoltaic applications.However,the long-term maintenance and use of photo-induced vacancy defects remain elusive,because of their rapid self-healing upon air exposure.In this study,we demonstrate that photo-induced oxygen vacancy(PIVO)defects can be stabilized by the photoexcitation of metal–organic framework(MOF)materials,which is crucial for SERS analysis.The PIVO defects in MOF materials are stable for at least two weeks in the ambient atmosphere,owing to the combination of steric hindrance and electron delocalization around vacancy defects,which significantly contrasts the short lifetime(within minutes)of PIVO defects in metal-oxide semiconductors.With the formation of stable PIVO defects,a prominent SERS enhancement surpassing that of pristine MOFs is achieved,accompanied with a reduced limit of detection by three orders of magnitude.Moreover,the additional SERS enhancement rendered by PIVO defects can be stably retained and is effective for monitoring various small molecules,such as dopamine and bisphenol A.