Scrolling bilayer WS2/MoS2 heterostructures for high-performance photo-detection

Recently,transition metal dichalcogenides(TMDCs)nanoscrolls have exhibited unique electronic and optical properties due to their spiral tubular structures,which are formed by rolling up monolayer TMDCs nanosheets.Inspired by the excellent physical and chemical properties of TMDCs van der Waals heterostructures(vdWHs),it is highly desirable to scroll TMDCs vdWHs for potential optoelectronic applications.In this work,WS2/MoS2 vdWHs nanoscrolls were massively prepared by dropping aqueous alkaline droplet on chemical vapor deposition(CVD)-grown bilayer WS2/MoS2 vdWHs,which were formed by growing monolayer WS2 islands on top of monolayer MoS2 nanosheets simultaneously.The optical microscopy(OM),atomic force microscopy(AFM),ultralow frequency(ULF)Raman spectroscopy and transmission electron microscopy(TEM)were utilized to characterize the WS2/MoS2 vdWHs nanoscrolls.As-obtained WS2/MoS2 vdWHs nanoscrolls exhibited new ULF breathing mode as well as shear mode peaks due to the strong interlayer interaction.Notably,the photosensitivities of WS2/MoS2 vdWHs nanoscrolls-based devices were about ten times higher than those of WS2/MoS2 vdWHs-based devices under blue,green and red lasers,respectively,which could be attributed to the ultrafast charge transfer at alternative WS2/MoS2 and MoS2/WS2 multi-interfaces in scrolled structure.Our work suggested that TMDCs vdWHs scrolls could be promising candidates for optoelectronic applications.

Optimized porous clay heterostructure for removal of acetaldehyde and toluene from indoor air

Adsorption is the most widely used technology for the removal of indoor volatile organic compounds （VOCs）. However, existing adsorbent-based technologies are inadequate to meet the regulatory requirement, due to their limited adsorption capacity and efficiency, especially under high relative humidity （RH） conditions. In this study, a series of new porous clay heterostructure （PCH） adsorbents with various ratios ofmicropores to mesopores were synthesized, characterized and tested for the adsorp- tion of acetaldehyde and toluene. Two of them, PCH25 and PCH50, exhibited markedly improved adsorption capabil- ity, especially for hydrophilic acetaldehyde. The improved adsorption was attributed to their large micropore areas and high micropore-to-mesopore volume ratios. The amount of acetaldehyde adsorbed onto PCH25 at equilibrium reached 62.7 mg. g-l, eight times as much as the amount adsorbed onto conventional activated carbon （AC）. Even at a high RH of 80%, PCH25 removed seven and four times more of the acetaldehyde than AC and the unmodified raw PCHs did, respectively. This new PCH optimized for their high adsorption and resistance to humidity has promising applications as a cost-effective adsorbent for indoor air purification.