Study On Hydrothermal/Solvothermal Synthesis And Luminescence Property Of NaGd?MoO₄?₂:Eu³⁺ Microcrystals

It is well known that the properties of nano/micro materials are affected by their dimensions,morphologies,sizes and other factors.Therefore,the topics on controlling and adjusting the morphology of nano/micro materials,exploring its basic principles and understanding the crystal growth mechanism have become research hotspots in the field of inorganic chemistry.As an important luminescent material,molybdate has drawn many researchers'attention in recent years.In this paper,four new kinds of sodium gadolinium molybdate(NaGd?MoO₄?₂:Eu³⁺)microcrystalswithdifferentmorphologiesweresynthesizedby hydrothermal/solvothermal method using the raw materials of Na₂MoO₄ and Gd₂O₃.The obtained product was characterized by X-ray diffraction,fluorescence spectrometer and scanning electron microscope.A series of studies were carried out on different conditions of pH values,types and amounts of the surfactant,reaction time,reaction temperature,alcohol-water volume ratios,etc.NaGd?MoO₄?₂:Eu³⁺light-converting materials with high fluorescence intensity and controllable morphology have been prepared.The main achievements are as follows:1.Hydrothermal synthesis of NaGd?MoO₄?₂:Eu³⁺microcrystalsWith the templating agent of citric acid and the Eu³⁺ion doping amount of 5%,the hydrothermal synthesis of spherical NaGd?MoO₄?₂:Eu³⁺microcrystals has been investigated by changing the pH value,reaction time,reaction temperature,surfactant dosage and other factors of the reaction system.The optimal synthesis condition of spherical NaGd?MoO₄?₂:Eu³⁺microspheres with diameters of 5.4⁶.0?m is as follows:pH=5,the mole ratio of n(Gd³⁺):n?H₃Cit?=1:2,the reaction temperature of 180?and the reaction time of 24 h.The obtained microspheres have a good dispersion and a smooth surface.Under the excitation number of 393nm,the product exhibits a strong emission at 616 nm.2.Solvothermal synthesis of NaGd?MoO₄?₂:Eu³⁺microcrystals?1?Solvothermal synthesis of octahedron-shaped NaGd?MoO₄?₂:Eu³⁺microcrystalsWith the n(Gd³⁺):n?CTAB?mole ratio of 1:1,the optimal synthesis condition for the diameter of 2.36².73?m octahedron-shaped NaGd?MoO₄?₂:Eu³⁺microcrystals is as follows:pH=5,the volume ratio of water:ethanol=1:0.4,the reaction temperature of 160?and the reaction time of 24 h.The octahedron-shaped NaGd?MoO₄?₂:Eu³⁺microcrystals prepared under this condition had a strong emission peak at 616 nm.?2?Solvothermal synthesis of small size porous spherical NaGd?MoO₄?₂:Eu³⁺microcrystalsWith the volume ratio of alcohol/water=1:1 and the surfactant of sodium citrate,the optimal synthesis condition of porous spherical NaGd?MoO₄?₂:Eu³⁺microcrystals with diameter of 0.65¹.1?m is as follows:pH=5,the mole ratio of n(Gd³⁺):n?Na₃Cit?=3:1,the reaction temperature of 180?and the reaction time of24 h.The NaGd?MoO₄?₂:Eu³⁺porous microspheres are small in size and have sparsely distributed pores on the surface.Finally,the microspheres exhibit high fluorescence intensity.?3?Solvothermal synthesis of rugby-shaped NaGd?MoO₄?_2:Eu³⁺microcrystalsWhen EDTA is adopted as the complexing agent and the volume ratio of alcohol and water is 1:1,the optimum synthesis condition for rugby-shaped NaGd?MoO₄?₂:Eu³⁺microcrystals with a diameter of 0.55⁰.68?m is as follows:pH=6,the mole ratio of n(Gd³⁺):n?EDTA?=1:1,the reaction temperature of 180?and the reaction time of 24 h.The rugby-shaped NaGd?MoO₄?₂:Eu³⁺ microcrystals have excellent luminescence performance with a strong emission peak at 616 nm under excitation of 393 nm.3.In comparison to NaGd?MoO₄?₂:Eu³⁺microcrystals with four new morphologies,the fluorescence intensities are in the following order:octahedron-shaped>spherical>small size porous microspherial>rugby-shaped.