Defect-Rich Monolayer MoS2 as a Universally Enhanced Substrate for Surface-Enhanced Raman Scattering.

Monolayer 2H-MoS2 has been widely noticed as a typical transition metal dichalcogenides (TMDC) for surface-enhanced Raman scattering (SERS). However, monolayer MoS2 is limited to a narrow range of applications due to poor detection sensitivity caused by the combination of a lower density of states (DOS) near the Fermi energy level as well as a rich fluorescence background. Here, surfaced S and Mo atomic defects are fabricated on a monolayer MoS2 with a perfect lattice. Defects exhibit metallic properties. The presence of defects enhances the interaction between MoS2 and the detection molecule, and it increases the probability of photoinduced charge transfer (PICT), resulting in a significant improvement of Raman enhancement. Defect-containing monolayer MoS2 enables the fluorescence signal of many dyes to be effectively burst, making the SERS spectrum clearer and making the limits of detection (LODs) below 10-8 M. In conclusion, metallic defect-containing monolayer MoS2 becomes a promising and versatile substrate capable of detecting a wide range of dye molecules due to its abundant DOS and effective PICT resonance. In addition, the synergistic effect of surface defects and of the MoS2 main body presents a new perspective for plasma-free SERS based on the chemical mechanism (CM), which provides promising theoretical support for other TMDC studies.

A Novel 3D Hierarchical Plasmonic Functional Cu@Co3O4@Ag Array as Intelligent SERS Sensing Platform with Trace Droplet Rapid Detection Ability for Pesticide Residue Detection on Fruits and Vegetables.

Rapid and effective detection of pesticide residues from complex surfaces of fruits and vegetables has important significance. Herein, we report a novel three-dimensional (3D) hierarchical porous functional surface-enhanced Raman scattering (SERS) substrate, which is fabricated by successive two-step hydrothermal synthesis strategy of silver nanoparticles (Ag NPs) and cobalt oxide nanowires (Co3O4 NWs) on the 3D copper foam framework as Cu@Co3O4@Ag-H. The strategy offers a new avenue for localized plasmonic materials distribution and construction, which exhibits better morphology regulation ability and SERS activity (or hotspots engineering) than physical spurring obtained Cu@Co3O4@Ag-S. The developed Cu@Co3O4@Ag-H possesses large surface area and rich hotspots, which contributes to the excellent SERS performance, including homogeneity (RSD of 7.8%), sensitivity (enhancement factor, EF of 2.24 × 108) and stability. The Cu@Co3O4@Ag-H not only provides plenty of Electromagnetic enhancement (EM) hotspots but also the trace detection capability for droplet rapid sensing within 2 s. Cu@Co3O4@Ag-H substrate is further developed as an effective SERS sensing platform for pesticide residues detection on the surfaces of fruits and vegetables with excellent LOD of 0.1 ppm, which is lower than the most similar reported works. This work offers new potential for bioassay, disease POCT diagnosis, national security, wearable flexible devices, energy storage and other related fields.

Wood-Derived Bimetallic and Heteroatomic Hierarchically Porous Carbon Aerogel for Rechargeable Flow Zn-Air Batteries.

It is necessary to correctly research and synthesize efficient and inexpensive catalysts to achieve reversible oxygen reduction reaction (ORR) and oxygen evolution reaction (OER), which is also a prerequisite for zinc-air batteries (ZABs). However, it is still a huge challenge to manufacture electrocatalysts with durable and high electrocatalytic performance from biomass. Here, a convenient method of delignification was used to transform natural balsa wood into a layered porous carbon material, FeCo alloy supported on a N, S-doped wood-based carbon aerogel (FeCo@NS-CA) as the cathode in rechargeable flow ZAB. The obtained FeCo@NS-CA with the porous lamellar architecture exhibits superior bifunctional electrocatalysis, including excellent electrochemical activities and superior stabilities. For ORR, relative to the reversible hydrogen electrode, the onset potential of FeCo@NS-CA is 0.97 V, and the half-wave potential is 0.85 V, which is consistent with the potential of commercial Pt/C. For OER, FeCo@NS-CA obtained an overpotential of 450 mV, which is very similar to the overpotential of the benchmark RuO2. The superior performance could be owing to the alloy carrier interaction between the FeCo alloy and the wood-based carbon aerogel co-doped with N and S. Moreover, the bifunctional air cathode in a flow ZAB assembled with the FeCo@NS-CA catalyst at a current density of 10 mA cm-2; the power density is 140 mW cm-2, and the specific capacitance is 760 mA h gZn-1, with a remarkable long-term stability of 400 h better than ZAB of benchmark Pt/C + RuO2. This research lays the foundation for transforming abundant biomass resources into high environmental protection materials for energy-related applications.