Department of Chemistry and Chemical Biology, Rutgers, The State University of New Jersey, 610 Taylor Road, Piscataway, NJ 08854, USA.
Chemistry. 2010 Sep 17;16(35):10735-43. doi: 10.1002/chem.201000354.
We report a solution-phase synthetic route to copper nanoparticles with controllable size and shape. The synthesis of the nanoparticles is achieved by the reduction of copper(II) salt in aqueous solution with hydrazine under air atmosphere in the presence of poly(acrylic acid) (PAA) as capping agent. The results suggest that the pH plays a key role for the formation of pure copper nanoparticles, whereas the concentration of PAA is important for controlling the size and geometric shape of the nanoparticles. The average size of the copper nanoparticles can be varied from 30 to 80 nm, depending on the concentration of PAA. With a moderate amount of PAA, faceted crystalline copper nanoparticles are obtained. The as-synthesized copper nanoparticles appear red in color and are stable for weeks, as confirmed by UV/Vis and X-ray photoemission (XPS) spectroscopy. The faceted crystalline copper nanoparticles serve as an effective catalyst for N-arylation of heterocycles, such as the C--N coupling reaction between p-nitrobenzyl chloride and morpholine producing 4-(4-nitrophenyl)morpholine in an excellent yield under mild reaction conditions. Furthermore, the nanoparticles are proven to be versatile as they also effectively catalyze the three-component, one-pot Mannich reaction between p-substituted benzaldehyde, aniline, and acetophenone affording a 100% conversion of the limiting reactant (aniline).
我们报告了一种通过溶液相合成法可控制备铜纳米粒子的方法，该方法使用水合肼在空气中还原铜(II)盐，同时使用聚丙烯酸（PAA）作为稳定剂。研究结果表明，pH 值对于形成纯铜纳米粒子起着关键作用，而 PAA 的浓度对于控制纳米粒子的尺寸和几何形状则至关重要。铜纳米粒子的平均尺寸可以从 30nm 到 80nm 之间变化，这取决于 PAA 的浓度。在适量的 PAA 存在下，得到具有面心立方晶体结构的铜纳米粒子。所合成的铜纳米粒子呈现红色，并通过紫外可见分光光度计（UV/Vis）和 X 射线光电子能谱（XPS）得到证实，其在数周内保持稳定。这些具有面心立方晶体结构的铜纳米粒子作为一种有效的催化剂，在温和的反应条件下，能够高效地催化杂环化合物的 N-芳基化反应，如 p-硝基苯氯和吗啉之间的 C-N 偶联反应，以高产率得到 4-(4-硝基苯基)吗啉。此外，纳米粒子还被证明具有多功能性，因为它们还可以有效地催化三组分一锅法 Mannich 反应，即 p-取代苯甲醛、苯胺和苯乙酮之间的反应，使限制反应物（苯胺）的转化率达到 100%。
