Aqueous Synthesis Of Color-Tunable And Stable Mn-Doped ZnSe Quantum Dots

With its unique quantum confinement effect, macroscopic quantum tunneling, quantum size effect and surface effect, showing unique physical and chemical properties different from macro-materials (such as the full spectrum of visible light emission within the region and good chemical stability), fluorescent quantum dots has also been attracted more and more attention. Quantum dots not only in immune biology and clinical laboratory science and other research areas are excellent fluorescent markers of biological materials, but also show excellent advantages in the LED lighting area. Especially the doped quantum dots with white light emission have the opportunity to be the mainstream of a new generation of lighting materials energy-saving.For the problems of the inherent toxicity from quantum dots with Cd, and poor stability due to surface modification of quantum dot technology and cumbersome process of doped quantum dots (prepared by organic metal methods), aqueous controllable synthesis(or hydrophilic phase synthesis) of high crystalline, color tunable (especially orange or red emission), high quantum yields, and non-toxic or low toxic manganese doped zinc selenide quantum dots, are expected to become mainstream material of fluorescent markers used clinically. And through control of surface defect emission and unique 4T1-6A1 emission of Mn2+, with the blue and yellow emission combined into a white light emission, manganese doped zinc selenide quantum dots are also expected to be the mainstream of a new LED lighting materials.This experiment based on the idea of nuclear doping, combined with microfluidic reactors and microwave assisted synthesis techniques, adjusted the surface topography of quantum dot with thiol-stabilizer, multi-step injected the precursor into the reaction, obtained high-quality Mn:ZnSe quantum dots. The main work as follows:1) we primary focused on the controlling size, shape, and structure of d-dots and the formation of the mutually diffused core (Mn (Zn)Se core) and pure ZnSe shell to tailor the optical properties, and finally we successfully prepared highly quality Mn:ZnSe d-dots. Through adjusting experimental parameters, the photoluminescence (PL) peak position of as-prepared d-dots was controllably tuned from 572 nm to 602 nm, and the QY improved to 4.8%, and the chemical stability is much better than that of CdTe QDs via aqueous synthesis.2) With microfluidic synthesis technology as the core, and controllable adjusting of various experimental parameters, injecting Mn2+ and Zn2+ ions at a certain flow rate with a syringe pump into the reaction solution to form the desired size of the nucleus and Mn/ Zn interface, and controlling different cationic precursor solution velocity ratio, separate stages of nucleation and growth realized in two different oil bath temperature to regulate nanoparticles surface morphology and doping ions doping position, Mn:ZnSe quantum dots with defect Mn2+ blue emission and yellow luminescence combined into a white light were obtained successfully, white light emission quantum yield more than 10%, and good dispersion of the resulting Mn:ZnSe quantum dots. These results will contribute to the development of white LED fluorescent materials.3) Combined with microfluidics technology and microwave synthesizing technology, diethylene glycol as solvent,3-mercaptopropionic acid as the stabilizer, Manganese chloride tetrahydrate and zinc acetate dihydrate as the source of cations, diethanolamine adjusting the pH of solution, two-step synthesis of microwave heating at 180°C, Mn:ZnSe nano rods were obtained. The TEM showed that rod-like nano-particles have the size of 5nm-10nm, length of nanorods 70nm-80nm, and the X-ray diffraction (XRD) characterization results proved a cubic zinc blende structure, and the crystallinity of the nanoparticles has improved greatly compareing to that of aqueous synthesis. The results show that by choosing a suitable stabilizer, high quantum yield, fluorescence properties, and good stability high-temperature synthesis in the hydrophilic phase is expected to achieve.