Hydrothermal Synthesis Of Transition-Metal Compounds

Transition-metal compounds have attracted much research interest due to their excellent optical,electronic,magnetic and catalytic properties and so on.With the increasing study,many synthesis methods were developed.Among them,the hydrothermal synthesis technique has been being extensively used owing to some virtues of the hydrothermal method. For example,employing the hydrothermal synthesis technique,the as-prepared products have high purity,good dispersion and crystallinity, and the synthesis process is controllable and low cost; Also,some special substances and phases,which cannot be synthesized by other methods, can be obtained by the hydrothermal route.In this thesis,several kinds of transition-metal compounds were successfully prepared by hydrothermal method in simple aqueous or/and microemulsion systems.The main works are summarized as follows;1.ZnO nanocapsules were successfully prepared by hydrothermal route in a simple aqueous solution with white phosphorus(WP); while keeping the other conditions constant,the penciMike ZnO microcrystals were obtained in the solution without WP.Researches showed that the properties of two kinds of ZnO crystals were distinctly different including UV-Vis and PL spectra,electrochemical respondence and photocatalytical degradation to organic molecules.Experiments indicated that some bivalent metal ions could weaken the intensities of PL peaks of ZnO nanocapsules and pencil-like ZnO microcrystals.However,the abilities were different.The above differences of properties should be attributed to the different shape and size between two ZnO crystals.2.The Ni₁₂P₅ hollow nanospheres were successfully synthesized in a W/O microemulsion system by hydrothermal method using NiSO₄·6H₂O and NaH₂PO₂ as the reactants.The microemulsion was comprised of water,CTAB,n-butanol and cyclohexane.X-ray powder diffraction (XRD)and Energy dispersive spectrum(EDS)were used to analyze the phase and component of the as-prepared product.TEM,SEM and HRTEM were employed for characterization of the morphology and size of the product.Under the same reaction conditions,the honeycomb-like nickel phosphides could be prepared in a simple aqueous system.The researches showed that Ni₁₂P₅ hollow nanospheres owned better photocatalytic degradation to organic dyes than honeycomb-like nickel phosphides.The electrochemical experiments proved Ni₁₂P₅ hollow nanospheres had stronger ability to accelerate the electron transfer between the adrenaline and electrode than honeycomb-like nickel phosphides.3.Novelty flower-like Co₁₁(HPO₃)₈(OH)₆ microcrystals were successfully synthesized by hydrothermal method or hydrothermal-microemulsion route at 150℃for 10h,respectively,using CoCl₂·6H₂O and NaH₂PO₂ as the starting reactants.Some influence factors on the morphology of the final product including reaction temperature,time and component were investigated.Researches showed that no obvious difference of morphologies was found from two products prepared from two systems.