Preparation And Surface Functionalization Of Mg-doped ZnO Quantum Dots

Zinc oxide (ZnO) is a new II-VI photo-electric semiconductor material with wide bandgap. It also has a wide direct band-gap of 3.37eV and a large exciton binding energy of 60meV at room temperature. Moreover, Zinc oxide (ZnO) has high thermal stability, good bio-compatibility, adjustable optical properties as well as rich raw material, low price, non -pollution, strong radiation, good electrical and mechanical coupling, which is a kind of green environmental protection material. Based on the above characteristics, ZnO is considered to be a new kind of photo-electric semiconductor material in shortwave length with broad application prospects, and becomes a popular topic of scientific research domain.In this paper, we synthesized Mg doped ZnO Quantum dots with good fluorescence properties by the simple thermal growth method according to different molar ratios of Mg/ZnO(varied from 0 to 1.6) under different temperatures (110-180℃) . The results indicate that the PL spectra for the QDs with Mg2+ ions are significantly blue-shifted, and the PL peak is red-shifted with the increasing reaction temperature. Through adjusting synthetic conditions, we found the best reaction conditions when the molar ratio of Mg/Zn is 0.8 and synthetic temperature is 130℃. Then, we use 2-(2-Hydroxyphenyl)-benzoxazol and 2-(2-Hydroxyphenyl)benzothiazole with important optoelectric application as the ligands to functionalize the QDs surface via ligand exchange process, in order to endow QDs with controllable fluorescence properties. It was found that the QDs size did not change before and after functionalized with derivatives of benzothiazole and benzoxazol. However, the PL properties had major changes, in particular, the fluorescence intensity greatly enhanced. These results indicated that the fluorescent complex formed on the surface of the QDs probably have a cooperating interaction with the inherent emission of QDs, resulting in the change of optical properties of QDs. These surface-functionalized QDs can be potentially used to design photoelectric devices.