Ruthenium-based catalysts are widely used in ammonia (NH 3 ) synthesis because of a high affinity for N 2 activation, while confronting the challenge of facile deactivation due to sintering. Herein, for the first time, we develop a highly active and sintering-resistant Ru2.1-CC catalyst via colloid carbonization (CC) for NH 3 synthesis. It exhibits a superior NH 3 synthesis rate around 9.4-fold that of Ru catalyst synthesized by impregnation method, displaying extremely high stability without aggregation of Ru nanoparticle after 100 h stability test. Our studies show that Ru2.1-CC possesses the average Ru particle size of 2.1 nm with narrow size distribution and thus exposes more active sites for N 2 activation. Moreover, the formation of Ru-C interaction via colloid carbonization over Ru2.1-CC can stabilize Ru particle size to realize high stability, meanwhile reduce work function and upshift the d-band center of Ru metal to accelerate its electron transfer for N 2 activation and NH 3 synthesis. This study provides a new strategy for simple synthesis of noble metal-based catalysts that are highly active and stable for NH 3 synthesis.
Thiamethoxam is one of the top three neonicotinoids found in the environment and in food. The widespread use of thiamethoxam in medicinal and edible herbs threatens their safe use. Therefore, it is particularly important to develop a rapid and simple approach to detect thiamethoxam residues in herbal medicines. In this study, colloidal carbon-based immunochromatographic strip (CNP-ICS) and colloidal gold-based immunochromatographic test strip (GNP-ICS) methods were respectively developed for the determination of thiamethoxam . The cutoff value of CNP-ICS was 0.1 ng mL −1 , which is six times more sensitive than that of the GNP-ICS method (0.6 ng mL −1 ). The CNP-ICS method was applied to detect thiamethoxam in medicinal and edible Lonicerae Japonicae Flos (LJF) for the first time, with a limit of detection of 10 ng g −1 . The detection results of thiamethoxam in 26 batches of LJF samples by the CNP-ICS were consistent with those of the LC–MS/MS method. High residue levels (10.16–530.40 ng g −1 ) and high detection rates (69.23%) of thiamethoxam in LJF were observed. The CNP-ICS prepared in this study has the merits of low cost, simple preparation, non-toxicity, and high sensitivity, which can be utilized for rapid field screening of thiamethoxam residues in complex matrices such as herbal medicines. Graphical
Yilun Luo,Taotao Lu,Shi Jin,Kai Ye,Shaoming Yu,Xianlong Zhang,Xueping Wu,Peiyong Ma,Jefferson W. Tester,Kui Wang
This study explores the core-shell structure formation mechanisms of primary carbon nanospheres (PCNs) through hydrothermal carbonization (HTC) of glucose at 200 °C, focusing on key phase-change polymerization reactions. Colloidal carbon nanoparticles in the aqueous phase filtrate self-assembled into secondary carbon nanospheres (SCNs) with intrinsic hollow structures during room temperature storage. FTIR results revealed similar functional groups on the surfaces of PCNs and SCNs due to esterification reactions during HTC cooling. XPS and 13 C NMR analyses identified HMF aldol condensation and etherification as dominant reactions for PCNs, while esterification and aldol condensation with levulinic acid were dominant for SCNs. The hypothesis suggests that PCNs initially formed hollow microframeworks but collapsed due to consumption of encapsulated organics, resulting in hydrophobic cores. These cores grew through aggregation (linear) and surface reactions (exponential), internalizing hydrophilic surfaces into hydrophobic cores, forming the final core-shell structure of PCNs.
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