Framework titanium atoms in titanium-substituted silicalite (TS-1) can be identified by UV resonance Raman spectroscopy since the associated Raman bands at 1125, 530, and 490 cm(-1) (see figure) are observed only when the charge transfer transition associated with the framework Ti atoms is excited by a UV laser. Thus, framework Ti atoms can be distinguished from nonframework Ti atoms and other defect sites. This method can be applicable to identifying transition metal atoms in the frameworks of other molecular sieves.
Framework titanium atoms in titanium-substituted silicalite (TS-1) can be identified by UV resonance Raman spectroscopy since the associated Raman bands at 1125, 530, and 490 cm(-1) (see figure) are observed only when the charge transfer transition associated with the framework Ti atoms is excited by a UV laser. Thus, framework Ti atoms can be distinguished from nonframework Ti atoms and other defect sites. This method can be applicable to identifying transition metal atoms in the frameworks of other molecular sieves.
High-efficiency Pt/ZrO2 catalysts with a mixed phase were successfully prepared. The catalysts exhibited high activity and their interfacial structure can change the reaction pathway.
ABSTRACT:The Raman enhancing ability of noble metal nanoparticles (NPs) is an important factor for surface enhanced Raman scattering (SERS) substrate screening, which is generally evaluated by simply mixing as-prepared NPs with Raman reporters for Raman signal measurements. This method usually leads to incredible results because of the NP surface coverage nonuniformity and reporter-induced NP aggregation. Moreover, it cannot realize in situ, continuous SERS characterization. Herein, we proposed a dynamic SERS monitoring strategy for NPs with precisely tuned structures based on a simplified spatially confined NP growth method. Gold nanorod (AuNR) seed NPs were coated with a mesoporous silica (mSiO 2 ) shell. The permeability of mSiO 2 for both reactive species and Raman reporters rendered the silver overcoating reaction and SERS indication of NP growth. Additionally, the mSiO 2 coating ensured monodisperse NP growth in a Raman reporter-rich reaction system. Moreover, "elastic" features of mSiO 2 were observed for the first time, which is crucial for holding the growing NP without breakage. This feature makes the mSiO 2 coating adhere to metal NPs throughout the growing process, providing a stable Raman reporter distribution microenvironment near the NPs and ensuring that the substrate's SERS ability comparison is accurate. Three types of NPs, i.e., core−shell Au@AgNR@mSiO 2 , Au@AuNR@mSiO 2 , and yolk−shell Au@void@AuNR@mSiO 2 NPs, were synthesized via core−shell overgrowth and galvanic replacement methods, showing the versatility of the approach. The living cell SERS labeling ability of Au@AgNR@mSiO 2 -based tags was also demonstrated. This strategy addresses the problems of multiple batch NP preparation, aggregation, and surface adsorption differentiation, which is a breakthrough for the dynamic comparison of SERS ability of metal NPs with precisely tuned structures and optical properties.
In this work, Ni/Fe layered double oxide supported Pt nanoparticles (Pt/LDO(N)) were prepared using a hydrothermal and colloid-impregnation method. The catalyst exhibited remarkable HCHO oxidation ability and long-time stability.
SnS with high theoretical capacity is a promising anode material for lithium‐ion batteries. However, dramatic volume changes of SnS during repeated discharge/charge cycles result in fractures or even pulverization of electrode, leading to rapid capacity degradation. To solve this problem, we construct a dual‐carbon‐confined SnS nanostructure (denoted as SnS@C/rGO) by depositing semi‐graphitized carbon layers on reduced graphene oxide (rGO) supported SnS nanoplates during high‐temperature reduction. The dual carbon of rGO and in situ formed carbon coating confines growth of SnS during the high‐temperature calcination. Moreover, during the reversible Li+ storage the dual‐carbon modification enables good electronic conductivity, relieves the volume effect, and provides double insurance for the electrical contact of SnS even after repeated cycles. Benefiting from the dual‐carbon confinement, SnS@C/rGO exhibits significantly enhanced rate capability and cycling stability compared with the bare and single carbon modified SnS. SnS@C/rGO presents reversible capacity of 1029.8 mAh g−1 at 0.2 A g−1. Even at a high current density of 1 A g−1, it initially delivers reversible capacity of 934.0 mAh g−1 and retains 98.2% of the capacity (918.0 mAh g−1) after 330 cycles. This work demonstrates potential application of dual‐carbon modification in the development of electrode materials for high‐performance lithium‐ion batteries.
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