| Summary: | 碩士 === 國立成功大學 === 化學工程學系碩博士班 === 93 === In order to obtain new materials with wide bandgap and high photoluminescence, CdSeTe nanoparticles have been synthesized by chemical wetness technique starting from the reaction of Cd(NO3)2 with NaHSe/NaHTe in aqueous solution. At first, the preparation of CdTe nanoparticles was investigated. Furthermore, three types of CdSeTe nanoparticles were obtained by different routes: Type I- CdTe(shell)/CdSe(core), Type II-CdSe(shell)/CdTe(core), and Type III-CdSe-CdTe. The characteristics of prepared particles including crystalline structure, particle size and size distribution, UV/Vis absorption and photoluminescence properties were also studied.
The experimental results show that by controlling the pH value (pH=10.5) and adding 3-mercaptopropionic acid (MPA) which 2.5 times of concentration of cadmium ion, the fcc-structured CdTe nanoparticles of photoluminescnece can be obtained without the presence of Cd(OH)2 impurities. Furthermore, it is found that the particle size decreases with reducing the pH value, the concentrations of precursors, and the amounts of MPA. However, at lower pH, e.g. pH<5.6, no photoluminescent property can be found for the resulting CdTe particles. Under the synthesis conditions of Cd:Se:Te = 2:1:1, 35oC, and pH10.5, the obtained particles for three types of CdSeTe, their particle sizes are all below 10nm. The absorption bandgap for Type I, II, and III particles are 2.40-2.61, 2.38-2.64, 2.53-2.68 eV respectively. Among three types of samples, Type III particles demonstrate the highest photoluminescence.
From this study, it is found that the CdSeTe nanoparticles can be synthesized in mild aqueous conditions. It is worth to note, the particle size, bandgap structure, and UV/PL properties of resulting nanoparticles can be modulated by adequately controlling the experimental conditions, such as pH value, precursor concentration, MPA concentration, and Cd/Se/Te ratio.
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