Yusuf Huda, Kim Whan-Gi, Lee Dong Hoon, Aloshyna Marie, Brolo Alexandre G, Moffitt Matthew G
Department of Chemistry, University of Victoria, P.O. Box 3065, Victoria, British Columbia V8W 3V6, Canada.
Langmuir. 2007 May 8;23(10):5251-4. doi: 10.1021/la7002904. Epub 2007 Apr 17.
We demonstrate a new hierarchical self-assembly strategy for the formation of photonic arrays containing quantum dots (QDs), in which sequential self-assembly steps introduce organization on progressively longer length scales, ranging from the nanoscale to the microscale regimes. The first step in this approach is the self-assembly of diblock copolymers to form block ionomer reverse micelles (SA1); within each micelle core, a single CdS QD is synthesized to yield the hybrid building block BC-QD. Once SA1 is completed, the hydrophobic BD-QD building blocks are blended with amphiphilic block copolymer stabilizing chains in an organic solvent; water addition induces secondary self-assembly (SA2) to form quantum dot compound micelles (QDCMs). Finally, aqueous dispersions of QDCMs are slowly evaporated to induce the formation of three-dimensional (3D) close-packed arrays in a tertiary self-assembly step (SA3). The resulting hierarchical assemblies, consisting of a periodic array of hybrid spheres each containing multiple CdS QDs, exhibit the collective property of a photonic stop band, along with photoluminescence arising from the constituent QDs. A high degree of structural control is possible at each level of organization by judicious selection of experimental variables, allowing various parameters governing the collective optical properties, including QD size, nanoparticle spacing, and mesocale periodicity, to be independently tuned. The resulting control over optical properties via successive self-assembly steps should provide new opportunities for hierarchical materials for QD lasers and all-optical switching.
我们展示了一种用于形成包含量子点（QD）的光子阵列的新型分级自组装策略，其中连续的自组装步骤在从纳米尺度到微米尺度的逐渐更长的长度尺度上引入组织。该方法的第一步是双嵌段共聚物的自组装以形成嵌段离聚物反胶束（SA1）；在每个胶束核内，合成单个CdS量子点以产生混合构建块BC-QD。一旦SA1完成，将疏水性BD-QD构建块与两亲性嵌段共聚物稳定链在有机溶剂中混合；加水诱导二次自组装（SA2）以形成量子点复合胶束（QDCM）。最后，QDCM的水分散体缓慢蒸发以在三级自组装步骤（SA3）中诱导形成三维（3D）密堆积阵列。所得的分级组装体由每个包含多个CdS量子点的混合球体的周期性阵列组成，表现出光子禁带的集体性质以及由组成量子点产生的光致发光。通过明智地选择实验变量，可以在组织的每个层面实现高度的结构控制，从而允许独立调整控制集体光学性质的各种参数，包括量子点尺寸、纳米颗粒间距和中尺度周期性。通过连续的自组装步骤对光学性质进行的控制应为量子点激光器和全光开关的分级材料提供新的机会。
