Silver Nanocubes Coated in Ceria: Core/Shell Size Effects on Light-Induced Charge Transfer

In-situ surface-enhanced Raman scattering based on MTi20 nanoflowers: Monitoring and degradation of contaminants

Real-time and in-situ monitoring of chemical reactions has attracted great attention in many fields. In this work, we in-situ monitored the photodegradation reaction process of methylene blue (MB) by Surface enhanced Raman scattering (SERS) technique. An effective and versatile SERS platform assembled from MoS₂ nanoflowers (NFs) and TiO₂ nanoparticles (NPs) was prepared successfully. The optimized MoS₂/TiO₂ substrate (MTi₂₀) exhibits not only an ultra-high SERS response but also the excellent catalytic degradation performance to the contaminant MB, which provided a new material for real-time and in-situ monitoring the photodegradation process. Experiments prove that the detection limit is as low as 10^-13 M, and degradation rate is as high as 97.2% in 180 s, respectively. And the activity of the substrate kept in the air for 90 days is almost unchanged. Furthermore, as a practical SERS substrate, MTi₂₀ can also detect trace amounts of other harmful substances including malachite green (MG), bisphenol A (BPA) and endosulfan. Thus, this study come up with a new orientation at the real-time and in-situ monitoring of photocatalytic reaction and may be applied in environmental monitoring and food security fields in the future.

Surface Enhanced Raman Scattering Revealed by Interfacial Charge-Transfer Transitions

Surface enhanced Raman scattering (SERS) is a fingerprint spectral technique whose performance is highly dependent on the physicochemical properties of the substrate materials. In addition to the traditional plasmonic metal substrates that feature prominent electromagnetic enhancements, boosted SERS activities have been reported recently for various categories of non-metal materials, including graphene, MXenes, transition-metal chalcogens/oxides, and conjugated organic molecules. Although the structural compositions of these semiconducting substrates vary, chemical enhancements induced by interfacial charge transfer are often the major contributors to the overall SERS behavior, which is distinct from that of the traditional SERS based on plasmonic metals. Regarding charge-transfer-induced SERS enhancements, this short review introduces the basic concepts underlying the SERS enhancements, the most recent semiconducting substrates that use novel manipulation strategies, and the extended applications of these versatile substrates.

Defect Engineering Enhances the Charge Separation of CeO2 Nanorods toward Photocatalytic Methyl Blue Oxidation

Defect-rich photocatalytic materials with excellent charge transfer properties are very popular. Herein, Sm-doped CeO₂ nanorods were annealed in a N₂ atmosphere to obtain the defective Sm-doped CeO₂ photocatalysts (Vo–Sm–CeO₂). The morphology and structure of Vo–Sm–CeO₂ were systematically characterized. The Vo–Sm–CeO₂ nanorods demonstrated an excellent photodegradation performance of methyl blue under visible light irradiation compared to CeO₂ nanorods and Sm–CeO₂. Reactive oxygen species including OH, ·O₂⁻, and h⁺ were confirmed to play a pivotal role in the removal of pollutants via electron spin resonance spectroscopy. Doping Sm enhances the conductivity of CeO₂ nanorods, benefiting photogenerated electrons being removed from the surface reactive sites, resulting in the superior performance.