Synthesis And Properties Of Chalcogenide Semiconductor Nanocrystals

First of all, monodispersed PbSe nanocrystals with tunablemorphologies and sizes could be synthesized by using PbO and Pb(Ac)2aslead sources respectively. When we used PbO as the lead source,monodipersed truncated octahedral and spherical PbSe nanocrystals could besynthesized at different reaction temperature; but when Pb(Ac)2was used asthe lead source, PbSe nanoflowers and nanostars could be synthesized atdifferent reaction temperature. The remarkable difference of obtained PbSenanocrystals was attributed to introducing acetate, which can generatedifferent steric hindrance. The different steric hindrance between two typesof fatty acids drastically increased the rate of the oriented attachments ofindividual nanocrystals to form3D nanoflowers. However, no matter whatPbSe morphologies could be gained, they would become cubic-likenanocrystals via long reaction time. This is based on the crystal habit ofPbSe.Next, by the pyrolysis of Ag(DDTC), we synthesized Ag2S QuantumDots (QDs) with3.5nm size. The photoluminescence peak position of theseQDs is1200nm. And then the Ag2S QDs were compressed in a diamond anvil cell (DAC). When the pressure is up to5GPa, the emission wavelengthof Ag2S QDs changed from1200to1900nm, exhibiting a large tunablerange by employing high pressure technology. At the same time, the bandgap of Ag2S QDs became narrow with increasing pressure. CorrespondingEg decreased from~1.7to1.5eV by calculating the pressure dependentabsorption spectra. In addition, we predicted Ag2S QDs might transferredfrom monoclinic to orthorhombic structure at~5GPa because of disappearedphotoluminescence.Finally, we adopted the sol-gel solution route to synthesize the highmonodispersed orthorhombic CuAgS nanocrystals for the first time. Byanalyzing the experiment results, a reasonable reaction mechanism could beproposed: we used monodispersed Ag2S nanocrystals as templete, andfurther injected CuCl2/OLA solution. Some Ag+could be displaced by Cu2+and generated CuAgS nanocrystals eventually. In addition, we could tailorthe size of CuAgS nanocrystals (e.g.17.0nm,21.0nm,26.0nm) throughchanging size of Ag2S nanocrystals. Furthermore, when using Se to replacethe thioacetamide, monodispersed CuAgSe nanocrystals could also besynthesized by the similar approach. The properties and application of theseobtained nanocrystals will be studied in the future.