Ultrasmall Au, Pd, and AuPd nanoparticles (NPs) stabilized by PVP were prepared in a microfluidic reactor with cyclone micromixers for rapid mixing of reactants. In this system, pulsation-free flow of reactants was achieved at a total flow rate of 2.6 L h^–1. A rapid homogeneous mixing within 2 ms was obtained with three cyclone micromixers. Controlled NP nucleation and growth occur in a following meandering microchannel. The resulting colloidal NPs were characterized thoroughly by various complementary techniques, e.g., high-resolution transmission electron microscopy (HRTEM), energy-dispersive X-ray spectroscopy (EDX), and ultraviolet–visible spectroscopy. The average NP diameter was about 1 nm with a narrow size distribution, and electron microscopy showed homogeneously alloyed NPs. Moreover, the particles were supported on TiO₂ for catalytic tests and further structural characterization. Electron microscopy showed a uniform distribution of NPs on the support with some aggregation. X-ray absorption spectroscopy (XAS) confirmed the formation of well-mixed AuPd alloys in NP cores with Pd-rich surfaces. Finally, 1 wt % metal-loaded supports showed catalytic activities in CO oxidation in the following order: Au/TiO₂ ≥ Au_xPd_y/TiO₂ ≥ Pd/TiO₂. Hence, the physical and chemical properties of these catalysts can be fine-tuned.

中文翻译：

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快速连续流动中用于催化应用的均相混合合金结构超小AuPd纳米粒子的微流体合成

在带有旋风分离器的微流体反应器中制备了通过PVP稳定的超小Au，Pd和AuPd纳米颗粒（NPs），用于快速混合反应物。在该系统中，以2.6 L h ^–1的总流速实现了反应物的无脉动流动。。使用三台旋风分离器在2毫秒内快速均匀混合。受控的NP成核和生长发生在随后蜿蜒的微通道中。通过各种辅助技术，例如高分辨率透射电子显微镜（HRTEM），能量色散X射线光谱（EDX）和紫外可见光谱，对得到的胶体NP进行了全面表征。NP的平均直径约为1 nm，尺寸分布较窄，电子显微镜显示NP均匀合金化。此外，颗粒被负载在TiO _2上用于催化测试和进一步的结构表征。电子显微镜显示NP在支持物上的均匀分布并有一些聚集。X射线吸收光谱法（XAS）证实在具有富Pd表面的NP核中形成了充分混合的AuPd合金。最后，1重量％的金属负载的载体显示出在CO氧化的催化活性按下列顺序：金/二氧化钛₂ ≥的Au _X钯_ý /二氧化钛₂ ≥的Pd /二氧化钛₂。因此，可以对这些催化剂的物理和化学性质进行微调。