Department of Materials Science and Engineering, National Taiwan University of Science and Technology, Taipei 10607, Taiwan.
Langmuir. 2011 Sep 20;27(18):11690-6. doi: 10.1021/la202661n. Epub 2011 Aug 26.
Nanohybrids of silver nanoparticles (AgNPs) supported on mica clay were synthesized by in situ reduction of silver nitrate in an aqueous solution. The required mica platelets of high aspect ratio were previously prepared by the exfoliation of mica clay stacks in a multilayered structure through an ionic exchange reaction with poly(oxypropylene)-amine-salt. The exfoliated nanoscale mica platelets (Mica) are polydispersed such that each platelet is 300-1000 nm in width and 1 nm in thickness. These platelets possess ionic charges in the form of ≡SiO(-)Na(+) at 120 mequiv/100 g and are suitable for supporting AgNPs in the process of in situ reduction of silver nitrate. Transmission electronic microscopy revealed the formation of AgNPs with a narrow size distribution of ca. 8 nm in diameter on the rim of individual Mica platelets. However, the pristine layered Mica structure without exfoliation failed to produce a fine AgNP distribution but instead generated particles larger than 30 nm and some precipitates. Characterization by differential scanning calorimetry and field emission scanning electron microscopy revealed that the fine AgNPs on Mica platelets exhibited a low melting temperature of 110 °C. The AgNP/Mica nanohybrid not containing an organic dispersant is considered to be a "naked" silver particle.
银纳米粒子（AgNPs）负载在云母薄片上的纳米复合材料是通过在水溶液中还原硝酸银原位合成的。所需的高纵横比云母薄片是通过云母粘土多层结构与聚（氧丙烯）-胺-盐的离子交换反应预先剥离制备的。剥离的纳米级云母薄片（云母）是多分散的，每个薄片的宽度为 300-1000nm，厚度为 1nm。这些薄片以 ≡SiO(-)Na(+) 的形式带有离子电荷，其含量为 120mequiv/100g，适合在原位还原硝酸银的过程中负载 AgNPs。透射电子显微镜显示，在单个云母薄片的边缘形成了直径约 8nm 的 AgNPs，其粒径分布较窄。然而，未经剥离的原始层状云母结构无法产生细小的 AgNP 分布，反而生成了大于 30nm 的颗粒和一些沉淀物。差示扫描量热法和场发射扫描电子显微镜的表征表明，云母片上的细小 AgNPs 的熔点低至 110°C。不含有机分散剂的 AgNP/云母纳米复合材料被认为是一种“裸露”的银颗粒。
