Syntheses,Characterization And Properties Of Lanthanide-Transition Metal Clusters@SiO₂ And Lanthanide-titanium Oxo Clusters

Polynuclear metal cluster is a hot study in the field of inorganic materials in the nearly twenty years.They not only own beautiftul structures,but also show rich optical,electrical,magnetic and catalytic properties,which makes them in single molecule magnet,magnetic refrigeration,luminescence,catalysis,chiral recognition,ferroelectric and so possess a wide applications.However,polynuclear metal cluster is susceptible to oxidative decomposition and agglomeration in air,resulting in their unique physical and chemical properties difficult to achieve normally.According to the previous analysis,we studied the magnetic behavior of the high nuclear lanthanide-transition metal clusters by reverse microemulsion method.Moreover,Lanthanide-titanium oxo clusters,as a part of titanium oxo clusters,have attracted chemists and materials scientists’ widespread attention in recent years.Studies shown that lanthanide-titanium oxo clusters can be applied to light,electricity,magnetic properties due to existing lanthanide ions,and to catalytic performance because of the similar to the anatase titanium dioxide.Based on the above,we explored the synthesis conditions of lanthanide-titanium oxo clusters,and successfully synthesized a series of lanthanide-titanium oxo clusters and analyzed their structures,as well as probed their photocatalytic properties.The main results are as follows:Ⅰ:The monodisperse metal nanoclusters were synthesised by inverse microemulsion method.(1)Based on the isotropy of Gd,monodisperse Gd52Ni56@SiO2 with nano-size structure were obtained.Magnetic investigation suggests that the magnetic interaction in the clusters were disappeared and magnetic entropy increased by about 10.1%.To the best of our knowledge,the present study represents the first example of an experimental investigation of the magnetic interaction of the single-molecule high-nuclearity lanthanide-transition metal compound and the first theoretical study on the magnetic interaction of the single-molecule high-nuclearity lanthanide-transition metal compound.(2)Based on the anisotropy of Dy/Tb,the monodisperse Ln12Fei4@SiO2(Ln = Dy,Tb)nanoparticles were successfully synthesized.The magnetic properties show that the inter-cluster interactions in Ln12Fe14@SiO2 vanished,as well as magnetic anisotropy and effective energy barrier reduction.II:Nineteen lanthanide-titanium oxo clusters were synthesized by solvothermal method with pivalic acid as ligand,different rare earth salts of acetylacetone and n-butyl titanate as raw materials.They were LnTi9(4～9),Ln2Ti4(10～17),LnTi4(18～21)and Ce2Ti7(22),respectively.The study proves that the band gaps for Lanthanide-titanium oxo clusters(4～22)were between 2.6 and 2.8 eV.These values are substantially smaller than 3.2 eV for P25.It is the first time that these clusters work as a catalyst in photocatalytic H2 evolution experiment without adding any sensitizer as well as co-catalyst in 10%methanol aqueous solution.The photocatalytic properties of these clusters revealed that their photocatalytic effects are significantly better than that of P25.Especially cluster 14(Eu2Ti4),the photocatalytic amount of H2 of Eu2Ti4 is 830 μmol·mg-1·h-1.It is 9.2 times higher than that of P25.And all of these clusters own well repeatability and circularity in photocatalytic water splitting.