| In recent years, bio-labels have become an important and hot research area in the area of modern analytical chemistry. Among which nanometer makers are a new kind of labels, they have wide development prospect in chemistry, biology and so on. Currently, metal nanoparticles, upconversion luminescent nanoparticles and quantum dots are used commonly. In this paper, we mainly study the last two, includes the upconversion luminescent nanoparticles and quantum dots (QDs). As we all known, the ideal luminescent labels should possess some characteristics such as high luminous efficiency, stable physical and chemical properties, small molecular weight and easy to be modified by other chemical reagents. In order to obtain this goal, we have sought suitable substrate material and preparation methods to optimize synthesize small particle size, high upconversion luminescent efficiency nanoparticles and semiconductor QDs, and explore their morphology and luminescence properties and related mechanisms. The main research work includes the following:Er3+/Yb3+co-doped CaSc2O4nano-powders were prepared by combustion method with glycine as the fuel. The effects of contration of Yb3+/Er3+, ignition temperature and glycine to metal nitrate molar ratio on up-conversion emission intensity were investigated. It emits intense green and red up-conversion luminescence under a980nm semiconductor laser excitation at room temperature. The relation between luminescent intensity and pump power was also investigated. The results showed that the red emissions (652-674nm) and the green emissions (552nm), which were attributed to the transitions4F9/2â†'4I15/2,4S3/2â†'2I15/2respectively, originated from a two-photon mechanism. While the green emissions (525nm), which were attributed to the transition2H11/2â†'4I15/2, originated from a three-photon mechanism. The present Er3+/Yb3+co-doped CaSc2O4nano-powders had an orthorhombic CaFe2O4-type structure, with good dispersity and efficient UC emission, which benfit from lower ignition temperature, are promising in the application of biolabels.CdS QDs was synthesized with dihydro lipoic acid as stabilizer by aqueous phase method, which has good stability and strong fluorescence intensity, the average particle diameter is10-15nm, the effects of reaction temperature, pH value, Cd/S, Cd/DHLA ratio ratio, reactant concentration for the synthesis of CdS QDs were explored, the optimal synthesis conditions are room temperature, pH=8.0, Cd/S=1.2/1, Cd/DHLA=1/1,[S2-]=33mmol/L. We also investigated the effects of different synthesis conditions on the morphology and the fluorescence intensity influence. QDs synthesized with this method can be preserved in the refrigerator for a long period of time, which has good stability. They lay a good foundation for the follow-up test and application.CdS QDs sol was synthesized in aqueous solution using L-cysteine as stabilizer, the efforts of Cd2+/S2-ratio, Cd2+/Cys ratio, pH value and other factors on the fluorescence spectrum were studied, and the best synthesized scheme of QDs was determined. Using CdSO4to modify their surface in order to improve surface defect structure and enhance their fluorescence efficiency.UV-vis, FS and other characterization methods were used to confirm the formation of CdS/CdO·nH2O core-shell particle, the results show that their luminous intensity was significantly higher than that of single CdS QDs, and emission spectrum peaks and ultraviolet absorption peak position are red shifted.In order to further improve the surface defect, to enhance their fluorescence intensity of CdS QDs, inorganic oxides were coated on the surface of CdS QDs to make them to be nuclear shell structure. Through a simple ultrasound sedimentation method, ZnO and CdO were coated on the surface of CdS QDs. A number of synthesis conditions of core-shell structure were explored simply. Effects of package material quantity, reaction time, reaction temperature, pH and other conditions on the formation of core-shell QDs are discussed, and their ultrasonic formation mechanism was simply investigated. |
PDF Full Text Request