Metallic phase molybdenum disulfide (1T-MoS 2 ), with its fast carrier mobility and highly abundant active sites, plays a vital role in the field of catalysis. However, the development of a simple and efficient strategy for the preparation of stabilized 1T-MoS 2 remains a great challenge. Herein, we report the spontaneous phase transformation of MoS 2 from the 2H to the 1T phase, caused by the strong metal−support interaction during iridium (Ir) adsorption. The resulting Ir/MoS 2 heterostructures show higher catalytic activity for overall water splitting than those of commercial Pt/C and IrO 2 in alkaline media. We believe that the spontaneous phase transformation of this material not only opens up a new perspective for developing advanced catalysts for alkaline water splitting but also presents an efficient and intriguing method for the phase engineering of two-dimensional materials.

Fabrication of multifunctional nanocatalysts with surface-enhanced Raman scattering (SERS) activity is of vital importance for monitoring catalytic courses in situ and studying the reaction mechanisms. Herein, SERS-active magnetic metal-organic framework (MOF)-based nanocatalysts were successfully prepared via a three-step method, including a solvothermal reaction, an Au seed-induced growth process, and a low-temperature cycling self-assembly technique. The as-synthesized magnetic MOF-based nanocatalysts not only exhibit outstanding peroxidase-like activity, but can also be applied as a SERS substrate. Owing to these features, they can be used for monitoring in situ catalytic oxidation of 3,3',5,5'-tetramethylbenzidine (TMB) by HO via a SERS technique, and the concentration of HO was determined. Owing to the intrinsic character of the Fe-based MOF material (MIL-100(Fe)), a novel photoinduced enhanced catalytic oxidation effect was demonstrated, in which the catalytic oxidation of TMB and o-phenylenediamine was accelerated. This study provides a versatile approach for the fabrication of functional MOF-based nanocomposites as a promising SERS substrate with a unique photoinduced enhanced peroxidase-like activity for potential applications in ultrasensitive monitoring, biomedical treatment, and environmental evaluation.

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Surface-enhanced Raman scattering (SERS) is a supersensitive technique for monitoring catalytic reactions. However, building a SERS-kinetics model to investigate catalytic efficiency on the surface or interface of the catalyst remains a great challenge. In the present study, we successfully obtained an excellent semiconducting SERS substrate, reduced MnCo2O4 (R-MnCo2O4) nanotubes, whose favorable SERS sensitivity is mainly related to the promoted interfacial charge transfer caused by the introduction of oxygen vacancies as well as the electromagnetic enhancement effect. Furthermore, the R-MnCo2O4 nanotubes showed a favorable oxidase-like activity toward oxidation with the aid of molecular oxygen. It was also showed the oxidase-like catalytic process could be monitored using the SERS technique. A new SERS-kinetics model to monitor the catalytic efficiency of the oxidase-like reaction was developed, and the results demonstrate that the V m values measured by the SERS-kinetics method are close to that obtained by the UV–vis approach, while the K m values measured by the SERS-kinetics method are much lower, demonstrating the better affinity between the enzyme and the substrate from SERS results and further confirming the high sensitivity of the SERS-kinetics approach and the actual enzyme-like reaction on the surface of nanozymes, which provides guidance in understanding the kinetics process and catalytic mechanism of natural enzymatic and other artificial enzymatic reactions. This work demonstrated the improved SERS sensitivity of defective semiconductors for the application of enzyme mimicking, providing a new frontier to construct highly sensitive biosensors.

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