Nano-sheets And Quantum Dots With Special Luminescent Properties

Nanomaterials with luminescent properties have become a hot topic in nanomaterials fields and attract attention of many researchers due to their high luminescent efficiency,adjustable performance,structural modification and high biocompatibility that result from their unique structural characteristics such as quantum size effect and surface e:ffect.In this paper,a variety of luminescnt nanomaterials,such as Ag₂S quantum dots?QDs?,rare-earth oxides nanosheets and rare-earth hydroxide nanosheets,were designed and synthesized.Their structure and properties were systematically studied.The paper includes the following aspects:Ag₂S QDs with properties of near-infrared?NIR?luminescence were synthesized under the protection of thioglycolic acid in the n-butanol organic solvent.The best condition for the synthesis is 90?,8 h and the best ratio between the reactants of silver and sulfur is 1:40.The NIR luminescence near 830 nm was discovered when 808 nm is chosen as the excitation wavelength.The reason for choosing of 808 nm as excitation wavelength is the absorption peak of Ag₂S QDs at 804 nm.In addition,980 nm light source also be used to excite Ag₂S QDs due to the existence of absorption peak at 1040 nm and NIR luminescence near 830 nm was also be observed.In the process of the dilution,the position and the intensity of the emission peak of the sol of Ag₂S QDs changed and we establish a model for explaining the phenomenon after we discuss the relationship between the structure and luminescent properties of Ag₂S QDs based on the existing research.The oxide nanosheets materials with upconversion luminescent properties were obtained by calcining the layered gadolinium hydroxide materials doped with erbium or holmium which were synthesized by one step method.The thickness of the oxide nanosheets is about 27 nm,and the oxide nanosheets have a good upconversion luminescent performance.In order to well understand the mechanism of the upconversion luminescence,we changed the excitation power of the light source to get different intensity of emission peaks.Then we found that the mechanism of the oxide nanosheets with upconversion luminescence is a two-photon absorption process.Layered gadolinium oxide materials and layered gadolinium hydroxide materials were synthesized by microwave method and hydrothermal method respectively.In order to obtain nanosheets of doped gadolinium oxide and doped gadolinium hydroxide,the layered gadolinium oxide materials and the layered gadolinium hydroxide materials are exfoliated in different solvents using different methods?e.g.ultrasound,ball milling,stirring,etc.?.The thin nanosheets of the layered gadolinium oxide materials and the layered gadolinium hydroxide materials obtained by the mechanical ball milling of the layered materials in water have a strong relaxation signal even at low concentrations of gadolinium,and the toxicity of the nanosheets is low.The thin nanosheets can be used as a magnetic resonance contrast agent.At the same time,these two kinds of nanosheets have fine fluorescence properties and can be used as MRI-fluorescence dual mode probes.