Bhand Ganesh R, Lakhe Manorama G, Rohom Ashwini B, Londhe Priyanka U, Kulkarni Sulabha K, Chaure Nandu B
Department of Physics, Savitribai Phule Pune University, Pune 411007, India.
Department of Physics, Indian Institute of Science Education and Research, Dr. Homi Bhaba Road, Pune 411008, India.
J Nanosci Nanotechnol. 2018 Apr 1;18(4):2695-2701. doi: 10.1166/jnn.2018.14329.
Monodispersed and highly luminescence cadmium selenide (CdSe) quantum dots (QDs) have been prepared in a single pot by colloidal reaction method. The QDs were characterized using X-ray diffraction (XRD), Raman Spectroscopy, transmission electron microscope (TEM), energy dispersive spectroscopy (EDS), UV-visible absorption spectroscopy and photoluminescence (PL) spectroscopy to study the structural, morphological, compositional and optical properties. The growth temperature played an important role to control the particle size. The optical wavelength was found to be shifted systematically from 460 nm to 575 nm upon increasing the reaction temperature from 110 °C to 260 °C. The size of CdSe QDs, ~2-4 nm was estimated from absorption data. The emission tail exhibited at higher wavelength in PL measurement for the QDs synthesized for lower reaction temperature revealed the presence of surface trap-states. A cubic crystal structure of CdSe QDs was revealed by XRD analysis. The spherical QDs of size 2 to 4.5 nm were observed from TEM analysis for the samples prepared at 140 °C, 200 °C and 260 °C. The sizes of QDs obtained by TEM are in good agreement with the results obtained from optical and XRD data. High resolution transmission electron microscopy (HRTEM) confirmed the cubic crystal structure of CdSe QDs. The Selected area diffraction (SAD) pattern exhibited diffused ring corresponds to (111), (220) and (311) reflections of cubic structure of CdSe. The compositional analysis studied by EDS revealed the growth of nearly stoichiometric CdSe QDs. The LO1 vibrational mode observed about 202-205 cm-1 decreases the broadening systematically upon increasing the reaction temperature.
通过胶体反应法在单锅中制备了单分散且高发光的硒化镉（CdSe）量子点（QDs）。使用X射线衍射（XRD）、拉曼光谱、透射电子显微镜（TEM）、能量色散光谱（EDS）、紫外可见吸收光谱和光致发光（PL）光谱对量子点进行了表征，以研究其结构、形态、组成和光学性质。生长温度在控制粒径方面起着重要作用。发现随着反应温度从110℃升高到260℃，光学波长系统地从460nm移至575nm。根据吸收数据估计CdSe量子点的尺寸约为2 - 4nm。在较低反应温度下合成的量子点的PL测量中，在较高波长处出现的发射尾表明存在表面陷阱态。XRD分析揭示了CdSe量子点的立方晶体结构。对于在140℃、200℃和260℃制备的样品，通过TEM分析观察到尺寸为2至4.5nm的球形量子点。通过TEM获得的量子点尺寸与从光学和XRD数据获得的结果高度一致。高分辨率透射电子显微镜（HRTEM）证实了CdSe量子点的立方晶体结构。选区衍射（SAD）图案显示出对应于CdSe立方结构的（111）、（220）和（311）反射的漫射环。通过EDS进行的成分分析表明形成了接近化学计量比的CdSe量子点。在约202 - 205cm-1处观察到的LO1振动模式随着反应温度的升高而系统地减小展宽。
