In this study, a simple method for directly synthesizing Ag nanoparticles on the inner wall of a microreactor was proposed to catalytically convert 4-NP to 4-AP. The proposed method employed silver ammonia as the precursor and polydopamine (PDA) to modify the surface of the microreactor. Because PDA contains numerous reducing agents of phenolic hydroxyl groups, the silver ions can be effectively reduced to Ag nanoparticles. Moreover, due to the zwitterionic nature of PDA, the use of silver ammonia as a precursor, which intrinsically has a high pH value, can allow for more silver ions to be adsorbed on the surface than the conventionally used AgNO₃ as a precursor. Accordingly, the precursor utilization could be greatly improved, leading to the increase of the catalyst loading and thereby boosting the catalytic conversion and durability. It was also found that an increase in the reduction time required for the catalyst preparation could lead to the increase of the catalyst loading and thereby the catalytic performance but a too long reduction time did not continue to make more contribution. Experimental results demonstrate that the microreactor prepared by this simple method is able to exhibit good catalytic activity and durability, providing a new approach for developing high-performance microreactors.

中文翻译：

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在微反应器中直接合成具有银氨和聚多巴胺的Ag纳米粒子的简单方法，可将4-NP转化为4-AP

在这项研究中，提出了一种直接在微反应器内壁上直接合成Ag纳米粒子的简单方法，将4-NP催化转化为4-AP。所提出的方法使用氨银作为前体，并使用聚多巴胺（PDA）修饰微反应器的表面。因为PDA包含许多酚羟基的还原剂，所以银离子可以有效地还原为Ag纳米颗粒。此外，由于PDA的两性离子性质，使用固有地具有高pH值的氨银作为前体可以比常规使用的AgNO ₃吸收更多的银离子在表面上。作为先驱。因此，可以大大提高前体的利用率，从而导致催化剂负载量的增加，从而提高催化转化率和耐久性。还发现增加催化剂制备所需的还原时间可导致催化剂载量的增加，从而导致催化性能的提高，但是还原时间过长并不能继续起到更大的作用。实验结果表明，采用这种简单方法制备的微反应器具有良好的催化活性和耐久性，为开发高性能微反应器提供了新途径。