Ujihara Masaki, Orbulescu Jhony, Imae Toyoko, Leblanc Roger M
Graduate School of Science, Nagoya University, Chikusa, Nagoya 464-8602, Japan.
Langmuir. 2005 Jul 19;21(15):6846-54. doi: 10.1021/la046817d.
Newly designed poly(amido amine) dendrimers, which have an azacrown core, hexyl spacers, and methyl ester terminals (aza-C6-PAMAM dendrimer), were spread at the air-water and air-silver nanoparticle suspension interfaces, and their film structures were examined by surface pressure-area (pi-A) and surface potential-area (DeltaV-A) isotherms and epifluorescence microscopy. It was revealed that generation (G) 1.5 aza-C6-PAMAM dendrimer on a water subphase formed homogeneous film with face-on configuration, and this configuration was maintained during compression. On the other hand, a G2.5 dendrimer film on the air-water interface took initially homogeneous and face-on configuration that was followed by the conformational change during compression. Using a silver nanoparticle suspension as subphase, G1.5 film was significantly reinforced, and the partial collapse (cracks) in the film appeared as network texture. For a G2.5 dendrimer film, the pi-A and DeltaV-A isotherm properties were similar to that on the water subphase except for the collapsed film; small spots instead of cracks were formed under the film after collapse. These effects of the silver nanoparticle may be due to the formation of a dendrimer/silver nanoparticle composite. The formation process of the nanocomposite film was verified by UV-vis spectroscopy. For the G1.5 dendrimer, silver clusters and nanoparticles adsorbed to the dendrimer film after spreading and formed a small amount of aggregates. During compression, the aggregation proceeded even at low surface pressure. For the G2.5 dendrimer, a dendrimer/nanoparticle composite was also formed after spreading. However, with the initial compression, the absorption bands of clusters, nanoparticles, and aggregate increased together. Upon further compression, while the bands of cluster and nanoparticles decreased, the bands of aggregate still increased. These results suggest that the G2.5 dendrimer covered the cluster and nanoparticles more efficiently than the G1.5 dendrimer did because of the larger molecular size.
新设计的具有氮杂冠醚核心、己基间隔基和甲酯端基的聚（酰胺胺）树枝状大分子（氮杂-C6-PAMAM树枝状大分子）被铺展在空气-水和空气-银纳米颗粒悬浮液界面上，并通过表面压力-面积（π-A）和表面电位-面积（ΔV-A）等温线以及落射荧光显微镜对其膜结构进行了研究。结果表明，在水亚相上的第1.5代（G）氮杂-C6-PAMAM树枝状大分子形成了具有面对面构型的均匀膜，并且这种构型在压缩过程中得以保持。另一方面，空气-水界面上的G2.5树枝状大分子膜最初呈均匀的面对面构型，随后在压缩过程中发生构象变化。以银纳米颗粒悬浮液作为亚相时，G1.5膜得到显著增强，并且膜中的部分塌陷（裂缝）呈现出网络纹理。对于G2.5树枝状大分子膜，除了塌陷的膜之外，π-A和ΔV-A等温线性质与在水亚相上的相似；塌陷后在膜下方形成的是小斑点而不是裂缝。银纳米颗粒的这些效应可能是由于形成了树枝状大分子/银纳米颗粒复合材料。通过紫外-可见光谱法验证了纳米复合膜的形成过程。对于G1.5树枝状大分子，铺展后银簇和纳米颗粒吸附到树枝状大分子膜上并形成少量聚集体。在压缩过程中，即使在低表面压力下聚集体化仍在进行。对于G2.5树枝状大分子，铺展后也形成了树枝状大分子/纳米颗粒复合材料。然而，在初始压缩时，簇、纳米颗粒和聚集体的吸收带一起增加。进一步压缩时，虽然簇和纳米颗粒的带减少，但聚集体的带仍在增加。这些结果表明，由于分子尺寸较大，G2.5树枝状大分子比G1.5树枝状大分子更有效地覆盖了簇和纳米颗粒。
