Synthesis And Application Of Multi-water-soluble Quantum Dots

In the past years,quantum dots have received extensive attention due to their size and compositional adjustability,and there are many applications in many fields such as display devices,photovoltaic devices,and biological applications.The element types of quantum dots and the synthesis methods have also made great progress.Compared with the traditional II-VI quantum dots,the quaternary quantum dots have excellent adjustability and are more suitable for the environmentally friendly aqueous phase synthesis method.The work of this thesis focuses on the synthesis of quaternary selenide and sulfide semiconductor quantum dots.The main contents are as follows:1.The Cu-Cd-Zn-S/ZnS core/shell quantum dots were successfully synthesized in the aqueous phase by autothermal method using 3-mercaptopropionic acid as a single ligand.By changing the feed ratio of Cd or Zn,the obtained luminescent range of the core/shell quantum dots can cover the complete visible light region,and the highest fluorescence efficiency can reach 81.93%.In addition,Cu-Cd-Zn-S/ZnS quantum dots can cover all visible light species by adjusting the pH conditions during the synthesis by two ratios,which is rarely reported in other literatures.The feed ratio of the precursor,the pH condition during the synthesis,and the thickness of the ZnS shell can all affect the quantum dot fluorescence efficiency.Such water-soluble quantum dots have a long fluorescence decay lifetime,and have great potential application value in display devices and photovoltaic devices.2.Ag-In-Zn-Se/ZnS and Cu-In-Zn-Se/ZnS core/shell quantum dots were successfully synthesized in the aqueous phase by using 3-mercaptopropionic acid and inexpensive and environmentally friendly gelatin as dual ligands and commercial electric pressure cooker as reaction vessel.Compared with traditional organic synthesis,this method is closer to the environmentally friendly synthesis concept.The feed ratio of In/Zn,the thickness of the In/MPA and ZnS shells all affect the fluorescence efficiency of the quantum dots.The selenium-based quantum dots in this chapter cover the green to red in the visible region or even infrared,which is rarely reported in the same literature,and the water-soluble quantum dots also have a long fluorescence decay lifetime.In this paper,the Cu-In-Zn-Se system quantum dots were prepared into quantum dot films for white LED.The Ag-In-Zn-Se system quantum dots were used to degrade the Rhodamine B under sunlight,and the degradation efficiency was up to79.82% in one hour.3.By introducing 3-mercaptopropionic acid and gelatin as dual ligands,Ag-In-Se-S/ZnS and Cu-In-Se-S/ZnS core-shell quantum dots were successfully synthesized in the water phase of the electric pressure cooker.This method has high synthesis efficiency,good repetition rate,low cost and environmentally friendly.In addition to the traditional cation ratio and the number of ZnS shells,the optical properties of quantum dots can be effectively adjusted by changing the ratio of Se and S anions,which is attributed to the sulfide and selenide band gaps under the same cation difference.At the same time,such water-soluble quantum dots also have a long fluorescence decay lifetime.In this paper,the Cu-In-Se-S system quantum dots were prepared into quantum dot films for white LED.The Ag-In-Se-S system quantum dots were used to degrade Rhodamine B under sunlight,and the degradation efficiency was up to 90.01% in one hour.