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Plasmonic nanocavities enable the manipulation of field polarization, thereby to selectively enhance the Raman modes of specific target molecules.

The implementation of plasmonic materials in heterogeneous catalysis was limited due to the lack of experimental access in managing the plasmonic hot carriers. Herein, we propose a liquid-state surface-enhanced Raman scattering (SERS) technique to manipulate and visualize heterogeneous photocatalysis with transparent plasmonic chips. The liquid-state measurement conquers the difficulties that arise from the plasmon-induced thermal effects, and thus the plasmon based strategies can be extended to investigate a wider range of catalytic reactions. We demonstrated the selection of reaction products by modulating the plasmonic hot carriers and explored the mechanisms in several typical C-C coupling reactions with 4-bromothiophenol (4-BTP) as reactants. The real-time experimental results suggest brand new mechanisms of the formation of C-C bonds on plasmonic metal nanoparticles (NPs): the residue of 4-BTP, but not thiophenol (TP), is responsible for the C-C coupling. Furthermore, this technique was extended to study the evolution of the Suzuki-Miyaura reaction on nonplasmonic palladium metals by establishing the charge transfer channels between palladium and Au NPs. The cleavage and formation of chemical bonds in each individual reaction step were discerned, and the corresponding working mechanisms were clarified.

Van der Waals heterojunctions (vdWHs) provide an excellent material system for the research of heterojunction-enhanced Raman scattering (HERS) due to their complexity and diversity. However, the traditional two-dimensional vdWHs are not conducive to the full utilization of near-field light due to the limitation of single dimension. Herein, we fabricate T-shaped mixed-dimensional SnSe2/ReS2 vdWHs via chemical vapor deposition and wetting transfer method, and demonstrate that the mixed-dimensional vdWHs can be used as ultrasensitive HERS chips based on the effective photo-induced charge transfer. Besides, the radiative energy transfer effect enhanced by near-field light further magnifies the HERS signals, improving the detection limit of rhodamine 6G (R6G) to femtomolar level. Furthermore, we demonstrate that the ultrasensitive screening of crystal violet in multicomponent solutions adsorbed on SnSe2/ReS2 vdWHs can be achieved by adjusting the laser wavelength, which has not been achieved by noble metal materials. This work provides new insights into the mixed-dimensional vdWHs and demonstrates the great application potential of T-shaped heterojunctions.

Multifunctional devices based on 2D organic/inorganic van der Waals heterostructures (2D OIHs) exhibit excellent properties due to extensive and flexible structural tunability. However, how to precisely regulate devices via in situ monitoring technique remains a great challenge, and corresponding development is still in its infancy. In this Letter, we show that Raman spectroscopy can serve as an effective in situ detection strategy to systematically observe the interfacial electron–phonon coupling (IEPC) between substrate and 2D OIHs. Combining non-adiabatic molecular dynamics simulations with ultrafast spectroscopy, we reveal that the different strengths of IEPC between substrates and 2D OIHs can directly modulate the photocarrier lifetimes of inorganic 2D materials, and therefore, indirectly modify the Raman-sensitive photo-induced charge transfer processes at the interface of 2D OIHs. Further in situ Raman evidence demonstrates the unique advantage of Raman spectroscopy with high sensitivity to monitor different substrate-induced IEPC under variable temperature.

Two-dimensional (2D) semiconductors are expected to replace noble metals to become the matrix materials of the next generation of commercial surface-enhanced Raman scattering (SERS) chips. Herein, we systematically studied the influence of the interlayer interaction on the SERS activity of 2D semiconductors from a brand-new perspective and comprehensively analyzed the physicochemical process of 2D semiconductor interlayer modulated SERS. Taking transition metal dichalcogenides as examples, we chose PtSe2 with strong interlayer interactions and ReS2 with weak interlayer interactions to analyze the physicochemical process of 2D semiconductor interlayer modulated SERS by first-principles calculations. PtSe2 and ReS2 samples with various thicknesses were prepared respectively, and the results of comparative experiments proved that the layer-dependent SERS tunability of 2D semiconductors is directly related to the interlayer interaction. This work provided a novel method for further improving the SERS detection limit of 2D semiconductors and a possible strategy for the industrial upgrading of commercial SERS chips.

Recent studies have found that some transition metal dichalcogenides (TMDs) with their own defects are difficult to store in the air for a long time. Worse stability of TMDs under extreme conditions has also been reported. Therefore, monitoring the oxidation and degradation processes of TMDs can directly guide the stability prediction of TMD-based devices and monitor TMDs quality. Herein, with the case of molybdenum disulfide, UV-ozone defect engineering is used to simulate the oxidation and degradation of TMDs under severe conditions. Surface-enhanced Raman scattering based on a chemical mechanism was first introduced to the dynamic monitoring of defect evolution in the oxidation and degradation of TMDs, and succeeds in tracking the TMDs oxidation state by the quantitative method. It is expected that this technology can be extended to the quantification and tracking of oxidation and degradation of other 2D materials.

Summary Topological surface-enhanced Raman scattering (T-SERS) is a phenomenon in which topological materials change the density of states (DOS) of the substrate through linear dispersion relation to boost photoinduced charge transfer and enhance Raman scattering. Through theoretical and experimental research, we show that the dispersion relation effect in topological materials is the main reason for T-SERS. In theory, the dispersion relation and dimension of the band structure will affect the distribution of DOS near the Fermi surface of substrates, and the change of DOS will lead to the different contribution of charge transfer for SERS. In experiments, the enhancement effect of topological insulators (Bi2Se3, Sb2Te3) and topological semimetal (PtSe2) on the Raman scattering of various molecules are compared. Among these materials, PtSe2 can achieve Raman enhancement of R6G molecules with the concentration of 10−9 M.

To realize fast detection of trace hazardous chemicals, a SERS substrate with the structure of a blackberry-like silver/graphene oxide nanoparticle cluster (Ag/GO NPC) has been designed and prepared through a quick capillarity-assistant self-assembly technology in this paper. Benefitting from the abundant "hot spots" and active oxygen sites brought by this Ag/GO NPC, the substrate shows good Raman performance for malachite green (MG), a common abusive germicide in aquaculture, with lowest limit of detection below 0.1 µg/L (3.48 × 10-10 mol/L). Detailed analyses are taken on both the formation process and enhancement mechanism of this SERS substrate, and the finite-difference time-domain simulations are utilized as well to prove our hypotheses. Further constructing this structure on polyethylene terephthalate (PET) film, a translucent flexible SERS substrate can be obtained, realizing a fast in situ detection of trace MG in the fishpond subsequently. In consideration of the facile preparation process, good SERS enhancement and affordable materials (PET, Cu, Ag and GO, etc.), this substrate presents high cost performance and a promising application prospect.

People have paid heavy price for the rapid development. The frequent haze in central plains is a very tough environmental problem face by people, because it not only affects people's health, but also affects the development of economy. This paper has analyzed the development, design principle and positive role of roof greening design in haze control starting from the causes of haze. Keywords—roof greening; central plains; haze control I. INTRODUCTION The problem of haze has been in existence for a long time, but it did not cause the attention of people, until it has caused a series of social problems with more and more serious affect, and caused traffic accidents affecting economic development and people's health, thus it has become a very tough environmental problem in central plains. As the core city in central plains, Zhengzhou has become the first interview object of Ministry of Environmental Protection because of its air quality deterioration, revealing the severity of the problem. II. CAUSES OF HAZE IN C E NTRAL PLAINS