Plasmonic nanostructures have been proved effective not only in catalyzing chemical reactions, but also in improving the activity of non-plasmonic photocatalysts. It is essential to reveal the synergy between the plasmonic structure and the non-plasmonic metal photocatalyst for expounding the underlying mechanism of plasmon-enhanced catalysis. Herein, the enhancement of resazurin reduction at the heterostructure of silver nanowire (AgNW) and palladium nanoparticles (PdNPs) is observed in situ by single-molecule fluorescence microscopy. The catalysis mapping results around single AgNW suggest that the catalytic activity of PdNPs is enhanced for ~ 20 times due to the excitation of localized surface plasmon resonance (LSPR) in the vicinity of the AgNW. This catalysis enhancement is also highly related to the wavelength and polarization of the excitation light. In addition, the palladium catalysis is further enhanced by ~ 10 times in the vicinity of a roughened AgNW or a AgNW–AgNW nanogap because of the improvement of catalytic hotspots. These findings clarify the contribution of plasmon excitation in palladium catalysis at microscopic scale, which will help to deepen the understanding of the plasmon-enhanced photocatalysis and provide a guideline for developing highly efficient plasmon-based photocatalysts.

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.

Creating pores in suprastructures of two-dimensional (2D) materials while controlling the orientation of the 2D building blocks is important in achieving large specific surface areas and tuning the anisotropic properties of the obtained functional hierarchical structures. In this contribution, we report that arranging graphitic carbon nitride (g-C₃N₄) nanosheets into one-dimensional (1D) architectures with controlled orientation has been achieved by using 1D oriented melem hydrate fibers as the synthetic precursor via a polycondensation process, during which the removal of water molecules and release of ammonia gas led to the creation of pores without destroying the 1D morphology of the oriented structures. The resulting porous g-C₃N₄ fibers with both meso- and micro-sized pores and largely exposed edges exhibited good sensing sensitivity and selectivity towards NO₂. The sensing performance was further improved by hybridization of the porous fibers with Au nanoparticles (Au NPs), leading to a detection limit of 60 ppb under ambient conditions. Our results suggest that the highly porous g-C₃N₄ fibers and the related hybrid structures with largely exposed graphitic layer edges are excellent sensing platforms and may also show promise in other electronic and electrochemical applications.