Shiomi Shohei, Kawamori Makoto, Yagi Shunsuke, Matsubara Eiichiro
Department of Materials Science and Engineering, Kyoto University, Kyoto 606-8501, Japan.
Department of Materials Science and Engineering, Kyoto University, Kyoto 606-8501, Japan.
J Colloid Interface Sci. 2015 Dec 15;460:47-54. doi: 10.1016/j.jcis.2015.08.033. Epub 2015 Aug 20.
With the recent development of nanotechnology, enhancement of the stability of nanomaterials is becoming ever more important for their practical applications. We studied the silica-coating of Cu nanoparticles and the enhanced stability of silica-coated Cu nanoparticles to oxidation. The metallic nanoparticles are easily oxidized and agglomerated compared with the bulk metals because the nanoparticles possess large specific surfaces. The Cu nanoparticle is one of the most difficult nanoparticles to be handled due to its absence of the oxidation stability. In the synthesis of silica-coated Cu nanoparticles via a sol-gel process using tetraethyl orthosilicate, the addition of NH3 as a catalyst of sol-gel reaction yielded homogeneous silica-coating. However, a large amount of Cu nanoparticles is instantly dissolved by forming complex ions in a NH3 solution during and before the silica-coating process. This is the difficulty in the silica-coating of Cu nanoparticles. In the present work, the dissolution behavior of Cu nanoparticles was electrochemically examined. This electrochemistry-based optimization of reducing power of a reaction bath enabled us to synthesize the silica-coated Cu nanoparticle via a consecutive liquid-phase reaction which requires only basic equipment and involves no separate centrifuging or extraction step. Cu nanoparticles coated by silica shells had the remarkable stability even in the presence of a strong oxidizing agent. Furthermore, we demonstrated that the highly stable Cu nanoparticles can be applied to a red pigment using a unique red color of Cu nanoparticles because of its surface plasmon resonance.
随着纳米技术的最新发展，提高纳米材料的稳定性对于其实际应用变得越来越重要。我们研究了铜纳米颗粒的二氧化硅包覆以及二氧化硅包覆的铜纳米颗粒对氧化的增强稳定性。与块状金属相比，金属纳米颗粒由于具有大的比表面积，容易被氧化和团聚。铜纳米颗粒由于缺乏氧化稳定性，是最难处理的纳米颗粒之一。在通过使用原硅酸四乙酯的溶胶 - 凝胶法合成二氧化硅包覆的铜纳米颗粒时，添加氨作为溶胶 - 凝胶反应的催化剂可得到均匀覆盖的二氧化硅。然而，在二氧化硅包覆过程中和包覆之前，大量的铜纳米颗粒会在氨溶液中通过形成络合离子而立即溶解。这就是铜纳米颗粒二氧化硅包覆过程中的难点。在本工作中，对铜纳米颗粒的溶解行为进行了电化学研究。基于这种电化学对反应浴还原能力的优化，使我们能够通过连续的液相反应合成二氧化硅包覆的铜纳米颗粒，该反应仅需要基本设备，且无需单独的离心或萃取步骤。即使在存在强氧化剂的情况下，被二氧化硅壳包覆的铜纳米颗粒也具有显著的稳定性。此外，由于铜纳米颗粒独特的红色以及其表面等离子体共振，我们证明了这种高度稳定的铜纳米颗粒可应用于红色颜料。
