A continuous microfluidic setup was developed to study colloidal synthesis of gold nanoparticles using tetrachloroauric acid as precursor, sodium borohydride as reducing agent and PVP as stabilizer. The setup consists of pressurized vessels that allow pulsation-free flow of reactants and a microfluidic chip with integrated micromixers essential for efficient mixing with small mixing time (2 ms) followed by a meandering microchannel. The microfluidic chip enables recording X-ray absorption spectra (XAS) in situ at different positions along the microchannel at high flow rates approaching turbulent mixing conditions and thus to correlate reaction time with changes in the nanoparticle structure. Significant contributions of oxidized gold could be observed after the first 6 ms of the reaction, whereas after 10 ms principally all gold appeared to be in a metallic state. The nanoparticles obtained were characterized ex situ by various complementary techniques. The resulting nanoparticles had average diameter of 1.0 nm and narrow size distributions compared with those produced in a batch reactor. Depositing the nanoparticles on TiO₂ resulted in catalysts with two different Au loadings (0.7 and 1.7 wt% Au/TiO₂) which exhibited good CO oxidation activity.

中文翻译：

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连续微流体合成胶体超小金纳米颗粒：早期反应阶段的原位研究及其催化应用

开发了一种连续的微流体装置，以四氯金酸为前体，硼氢化钠为还原剂，PVP为稳定剂来研究金纳米颗粒的胶体合成。该装置由允许反应物无脉动的加压容器和带有集成微混合器的微流控芯片组成，集成微混合器对于在短混合时间（2毫秒）后进行有效混合非常重要，随后是蜿蜒的微通道。微流控芯片可现场记录X射线吸收光谱（XAS）在接近湍流混合条件的高流速下沿微通道的不同位置处的反应，从而使反应时间与纳米颗粒结构的变化相关。在反应的前6毫秒后，可以观察到氧化金的显着贡献，而在10毫秒后，基本上所有的金似乎都处于金属态。通过各种互补技术对获得的纳米颗粒进行了非原位表征。与在间歇反应器中生产的纳米颗粒相比，所得纳米颗粒的平均直径为1.0nm并且尺寸分布窄。将纳米颗粒沉积在TiO _2上产生具有两种不同的Au负载量（0.7和1.7 wt％的Au / TiO ₂）的催化剂，其表现出良好的CO氧化活性。