Synthesis And Photoelectric Properties Of Sulfide Quantum Dots

As an excellent luminescent material,quantum dots are widely used in many fields,such as light-emitting diodes,solar cells,bioimaging,ion detection.Sulfide quantum dots are very promising quantum dots materials due to their adjustable band gap and convenient synthesis.In this thesis,we synthesized Cu-Ga-S/ZnS quantum dots and Ga2S3 quantum dots.On the basis,we investigated the photoelectric properties of Cu-Ga-S/ZnS quantum dots-based light-emitting diodes and the detection properties of heavy metal ions for Ga2S3 quantum dots.The main results were listed as follows:(1)Cu-Ga-S/ZnS quantum dots were prepared by hot injection method using 1-dodecanethiol as solvent,ligand,and reactant.We studied the optical properties of Cu-Ga-S/ZnS quantum dots and the results show that the luminescence can be adjusted from green to red by changing the Cu/Ga ratio.The quantum efficiency of Cu-Ga-S/ZnS quantum dots is up to 48%and the half width at half maximum of fluorescence spectra is about 75 nm.(2)Monochromatic light emitting diodes were fabricated based on Cu-Ga-S/ZnS quantum dots of different luminescent colors,and their luminescence can be adjusted from green to red.A white light-emitting diode based on the yellow-emitting CGS/ZnS quantum dots was also prepared and its photoelectric properties were studied.As the results showed,it exhibits a color rendering index of 66?67,a correlated color temperature of 5888-6291 K,and a luminous efficacy of 18.8?37.1 lm/W.Owing to adopting the yellow-emitting quantum dots which the eyes of people are more sensitive to,its luminous efficiency is higher than other white-emitting diodes based on the Cu-Ga-S/ZnS quantum dots.(3)The Ga2S3 quantum dots were prepared by one-pot method and its optical properties were researched.It is found that luminescence of the quantum dots can be tuned from blue to yellow by changing the Ga/S feed ratio.We propose a possible luminescence mechanism to explain the luminescence of such quantum dots and we believe that the luminescence of Ga2S3 quantum dots is related to the defect levels caused by sulfur vacancies and gallium vacancies.Furthermore,we verified the rationality of this mechanism by means of X-ray photoelectron spectroscopy and other experimental methods.(4)The Ga2S3 quantum dots synthesized in the oil phase were transferred to the aqueous phase to obtain a stable solution and the fluorescence detection performance of the quantum dots on the heavy metal ions was studied.The results show that the effects of different metal ions on the fluorescence of Ga2S3 quantum dots are different.We believe this is due to different quenching mechanisms.And Cu2+ and Pb2+ have a high quenching ability to the fluorescence of Ga2S3 quantum dots,and have the advantages of not being disturbed by other ions,linear change and rapid response.This is beneficial to the application of this Ga2S3 quantum dot in the actual detection on heavy metal ions.