Department of Chemistry, B.B.K. D.A.V. College for Women, Amritsar 143005, Punjab, India.
J Phys Chem B. 2013 Mar 14;117(10):3028-39. doi: 10.1021/jp310507m. Epub 2013 Mar 4.
Self-assembled gold (Au) nanoparticles (NPs) were synthesized in micelle surface cavities of a L121 block polymer in the presence of zwitterionic (viz. DPS, TPS, and HPS) and sugar surfactants (OG and DDM) in aqueous phase at 70 °C by using the surface cavities of L121 as reducing sites for converting Au(III) into Au(0). All reactions were monitored simultaneously by UV-visible spectroscopy to determine the growth kinetics in gold nucleating centers on the basis of surface plasmon resonance that also helped in tracing the structure micelle transitions over a wide temperature range of 10-70 °C. The surfactant/L121 mole ratio was changed systematically from 0.5 to 2.5 by keeping L121 and HAuCl4 concentrations constant at 10 and 0.25 mM, respectively, to determine the shape and size of the micelles and their relation to the self-assembled behavior of Au NPs. TEM studies were used to have a direct insight into the morphology of micelle templates and their shape and size for self-assembled NPs. L121 along with DPS (C12 carbon chain) produced well-defined micelles loaded with tiny NPs of 3-6 nm in the L121-rich region of the mixture, while large flower-like compound micelles with a clear core-shell morphology were produced in the DPS-rich region. TPS and HPS (C14 and C16 hydrocarbon chains, respectively) with stronger hydrophobicity than DPS also produced almost similar micelles loaded with tiny NPs in the L121-rich region, but they disappear in the surfactant-rich region. Replacement of zwitterionic with ionic surfactants did not yield micelle templates for self-assembled NPs. Results conclude that well-defined micelles of L121 are the fine templates for self-assembled NPs that can only be achieved in the presence of a neutral surfactant with low concentration and low hydrophobicity.
自组装金（Au）纳米粒子（NPs）在 70°C 下于水相中，在 L121 嵌段聚合物的胶束表面腔内，使用 L121 的表面腔作为还原位点，将 Au(III)转化为 Au(0)，在两性离子（即 DPS、TPS 和 HPS）和糖表面活性剂（OG 和 DDM）的存在下合成。所有反应均通过紫外-可见光谱同时监测，以根据表面等离子体共振确定金成核中心的生长动力学，该共振也有助于在 10-70°C 的宽温度范围内追踪胶束结构转变。通过保持 L121 和 HAuCl4 的浓度分别为 10 和 0.25mM 不变，系统地改变表面活性剂/L121 的摩尔比从 0.5 到 2.5，以确定胶束的形状和尺寸及其与 Au NPs 自组装行为的关系。TEM 研究用于直接了解胶束模板的形态及其对自组装 NPs 的形状和尺寸的影响。L121 与 DPS（C12 碳链）一起产生了具有良好定义的胶束，在混合物的 L121 丰富区域中负载有 3-6nm 的微小 NPs，而在 DPS 丰富区域中则产生了具有明显核壳形态的大花状复合胶束。TPS 和 HPS（分别为 C14 和 C16 烃链，疏水性强于 DPS）也在 L121 丰富区域中产生了负载有微小 NPs 的几乎相似的胶束，但它们在表面活性剂丰富区域中消失。用离子型表面活性剂代替两性离子表面活性剂不会产生用于自组装 NPs 的胶束模板。结果表明，L121 的良好定义胶束是自组装 NPs 的精细模板，只有在存在低浓度和低疏水性的中性表面活性剂时才能实现。
