Thangadurai P, Balaji S, Manoharan P T
Nanotechnology. 2008 Oct 29;19(43):435708. doi: 10.1088/0957-4484/19/43/435708. Epub 2008 Sep 22.
This study is aimed at identifying a suitable organic thiol for CdS by studying its structural, thermal and photophysical characteristics. Quantum dots of the II-VI semiconductor CdS, in the size regime of 2.0-3.3 nm, were prepared in the cubic phase by a wet chemical method. Five organic thiols were used for capping: (i) 1,4-dithiothreitol (DTT), (ii) 2-mercaptoethanol (ME), (iii) cysteine (Cys), (iv) methionine (Meth), and (v) glutathione (GSH). Structural studies were carried out by x-ray diffraction (XRD) and transmission electron microscopy (TEM), which revealed the cubic phase of CdS. Optical properties were studied by FT-IR, UV-visible and fluorescence spectroscopic techniques, and a comparison was made between uncapped and capped CdS. FT-IR studies suggested two different bonding mechanisms of the capping agents with the CdS. GSH and DTT capped CdS showed significant decrease in absorption wavelengths. An increase in band gap was observed in two cases: when (i) capped and (ii) decreased in size. The band gap was increased from 2.50 eV for the uncapped to 2.77 eV for the DTT capped CdS. DTT was found to be the best capping agent for CdS among these five organic thiols in two aspects: (i) yielding lower grain size in cubic phase, and (ii) good fluorescence properties with efficient quenching of the surface traps.
本研究旨在通过研究其结构、热学和光物理特性来确定一种适合用于硫化镉（CdS）的有机硫醇。采用湿化学方法在立方相中制备了尺寸在2.0 - 3.3纳米范围内的II - VI族半导体硫化镉量子点。使用了五种有机硫醇进行包覆：（i）1,4 - 二硫苏糖醇（DTT），（ii）2 - 巯基乙醇（ME），（iii）半胱氨酸（Cys），（iv）甲硫氨酸（Meth），以及（v）谷胱甘肽（GSH）。通过X射线衍射（XRD）和透射电子显微镜（TEM）进行结构研究，结果表明硫化镉为立方相。通过傅里叶变换红外光谱（FT - IR）、紫外 - 可见光谱和荧光光谱技术研究光学性质，并对未包覆和包覆后的硫化镉进行了比较。FT - IR研究表明包覆剂与硫化镉存在两种不同的键合机制。GSH和DTT包覆的硫化镉吸收波长显著降低。在两种情况下观察到带隙增加：（i）包覆后，（ii）尺寸减小。带隙从未包覆时的2.50电子伏特增加到DTT包覆的硫化镉的2.77电子伏特。在这五种有机硫醇中，DTT在两个方面被发现是硫化镉的最佳包覆剂：（i）在立方相中产生较小的晶粒尺寸，（ii）具有良好的荧光性质且能有效猝灭表面陷阱。
