Department of Materials Science and Engineering and Laboratory for Research on the Structure of Matter, University of Pennsylvania, Philadelphia, Pennsylvania 19104-6272, United States.
ACS Nano. 2012 Feb 28;6(2):1578-88. doi: 10.1021/nn2045449. Epub 2012 Feb 9.
In this paper, polymer nanocomposite films containing gold nanorods (AuNRs) and poly(2-vinyl pyridine) (P2VP) have been investigated for their structure-optical property relationship. Using transmission electron microscopy (TEM), the assembly of AuNRs (7.9 nm × 28.4 nm) grafted with a P2VP brush in P2VP films is examined as a function of the AuNR volume fraction Ø(AuNRs) and film thickness h. For h ∼ 40 nm, AuNRs are confined to align parallel to the film and uniformly dispersed at low Ø(AuNRs). Upon increasing Ø(AuNRs), nanorods form discrete aggregates containing mainly side-by-side arrays due to depletion-attraction forces. For Ø(AuNRs) = 2.7%, AuNRs assemble into a 2D network where the discrete aggregates are connected by end-to-end linked nanorods. As Ø(AuNRs) further increases, the polymer-rich regions of the network fill in with nanorods and rod overlap is observed. Monte Carlo simulations capture the experimentally observed morphologies. The effect of film thickness is investigated at Ø(AuNRs) = 2.7%, where thicker films (40 and 70 nm) show a dense array of percolated nanorods and thinner films (20 nm) exhibit mainly isolated nanorods. Using Rutherford backscattering spectrometry (RBS), the AuNRs are observed to segregate near the substrate during spin-casting. Optically, the longitudinal surface plasmon resonance (LSPR) peaks are correlated with the local orientation of the AuNRs, where side-by-side and end-to-end alignments induce blue and red shifts, respectively. The LSPR undergoes a red shift up to 51 nm as Ø(AuNRs) increases from 1.6 to 2.7%. These studies indicate that the optical properties of polymer nanocomposite films containing gold nanorods can be fine-tuned by changing Ø(AuNRs) and h. These results are broadly applicable and provide guidelines for dispersing other functional nanoparticles, such as quantum dots and carbon nanotubes.
本文研究了含有金纳米棒（AuNRs）和聚（2-乙烯基吡啶）（P2VP）的聚合物纳米复合膜的结构-光学性质关系。通过透射电子显微镜（TEM），研究了接枝有 P2VP 刷的 AuNRs（7.9nm×28.4nm）在 P2VP 膜中的组装情况，作为 AuNRs 体积分数Ø（AuNRs）和膜厚 h 的函数。对于 h∼40nm，AuNRs 被限制在平行于膜的方向上，并在低Ø（AuNRs）下均匀分散。随着Ø（AuNRs）的增加，由于耗尽-吸引力的作用，纳米棒形成了主要由并排排列组成的离散聚集体。对于Ø（AuNRs）=2.7%，AuNRs 组装成 2D 网络，其中离散聚集体通过端到端连接的纳米棒连接。随着Ø（AuNRs）的进一步增加，网络的聚合物富区用纳米棒填充，并观察到棒重叠。蒙特卡罗模拟捕获了实验观察到的形态。在Ø（AuNRs）=2.7%的情况下，研究了膜厚的影响，其中较厚的膜（40nm 和 70nm）显示出密集排列的渗透纳米棒，而较薄的膜（20nm）主要显示出孤立的纳米棒。使用卢瑟福背散射光谱（RBS），在旋涂过程中观察到 AuNRs 在基底附近分离。在光学方面，纵向表面等离子体激元共振（LSPR）峰与 AuNRs 的局部取向相关联，其中并排和端到端的排列分别诱导蓝移和红移。随着Ø（AuNRs）从 1.6%增加到 2.7%，LSPR 发生了 51nm 的红移。这些研究表明，通过改变Ø（AuNRs）和 h，可以精细调整含有金纳米棒的聚合物纳米复合膜的光学性质。这些结果具有广泛的适用性，并为分散其他功能纳米粒子，如量子点和碳纳米管，提供了指导。
