Ji Xiaojun, Wang Chengshan, Xu Jianmin, Zheng Jiayin, Gattás-Asfura Kerim M, Leblanc Roger M
Department of Chemistry, University of Miami, Coral Gables, Florida 33124-0431, USA.
Langmuir. 2005 Jun 7;21(12):5377-82. doi: 10.1021/la050327j.
Trioctylphosphine oxide- (TOPO-) capped (CdSe)ZnS quantum dots (QDs) were prepared through a stepwise synthesis. The surface chemistry behavior of the QDs at the air-water interface was carefully examined by various physical measurements. The surface pressure-area isotherm of the Langmuir film of the QDs gave an average diameter of 4.4 nm, which matched very well with the value determined by transmission electron microscopy (TEM) measurements if the thickness of the TOPO cap was counted. The stability of the Langmuir film of the QDs was tested by two different methods, compression/decompression cycling and kinetic measurements, both of which indicated that TOPO-capped (CdSe)ZnS QDs can form stable Langmuir films at the air-water interface. Epifluorescence microscopy revealed the two-dimensional aggregation of the QDs in Langmuir films during the early stage of the compression process. However, at high surface pressures, the Langmuir film of QDs was more homogeneous and was capable of being deposited on a hydrophobic quartz slide by the Langmuir-Blodgett (LB) film technique. Photoluminescence (PL) spectroscopy was utilized to characterize the LB films. The PL intensity of the LB film of QDs at the first emission maximum was found to increase linearly with increasing number of layers deposited onto the hydrophobic quartz slide, which implied a homogeneous deposition of the Langmuir film of QDs at surface pressures greater than 20 mN.m(-1).
通过逐步合成法制备了三辛基氧化膦（TOPO）包覆的（CdSe）ZnS量子点（QDs）。通过各种物理测量仔细研究了量子点在气-水界面的表面化学行为。量子点的Langmuir膜的表面压力-面积等温线给出的平均直径为4.4 nm，如果将TOPO包覆层的厚度计算在内，该值与通过透射电子显微镜（TEM）测量确定的值非常吻合。通过两种不同的方法测试了量子点Langmuir膜的稳定性，即压缩/减压循环和动力学测量，这两种方法均表明TOPO包覆的（CdSe）ZnS量子点可以在气-水界面形成稳定的Langmuir膜。落射荧光显微镜显示在压缩过程的早期阶段量子点在Langmuir膜中发生二维聚集。然而，在高表面压力下，量子点的Langmuir膜更加均匀，并且能够通过Langmuir-Blodgett（LB）膜技术沉积在疏水石英载玻片上。利用光致发光（PL）光谱对LB膜进行表征。发现量子点LB膜在第一个发射最大值处的PL强度随着沉积在疏水石英载玻片上的层数增加而线性增加，这意味着在表面压力大于20 mN·m⁻¹时量子点的Langmuir膜均匀沉积。
