Synthesis And Luminescence Properties Of Rare Earth Organic Complexes And Core-shell SiO₂@RE-DABA-Si-phen/bipy And Interraction With BSA

In this paper,3,5-N,N-bi?amidopropyltriethoxysilane?Benzoic acid(C₂₇H₅₀N₄O₁₀Si₂)was synthesized by the reaction of 3,5-diaminobenzoic acid with propyl triethoxysilane?TEPIC?,abbreviated as DABA-Si.DABA-Si was used as the first ligand,phen and dipy were used as the second ligand,which coordination with RE³⁺(RE=Sm³⁺,Eu³⁺,Tb³⁺,Dy³⁺)to form four binary rare earth complexes and eight ternary rare earth complexes.By elemental analysis,thermosgravimetry-differential scanning calorimetry,molar conductivity and rare earth titration TG-DSC analysis.The composition and characterization of the binary rare earth complexes were as follows:RE?DABA-Si?₂·?ClO₄?₃·5H₂O.The ternary compositions were RE?DABA-Si??phen?₂·2H₂O and RE?DABA-Si?·?dipy?₂?ClO₄?₃·2H₂O.The IR spectra of rare earth complexes show that the first ligand DABA-Si was coordinated with rare earth ions through two oxygen atoms of carboxyl groups,and phen/bipy were coordinated with rare earth ions by two nitrogen atoms.The results of molar conductivity explained that the binary and ternary rare earth complexes,electrolyte types were 1:2 type.That was one ClO_4- ions was participate in the coordination with rare earth ions.The phosphorescence spectrum measurement results showed that the triplet states of the ligands DABA-Si and bipy were higher than those of the excited energy of Sm³⁺?4G5/2,17900cm-1?,Eu³⁺?sD0,17260cm'1?,Tb³⁺?5D4,20454cm'1?,Dy³⁺?4F9/2,21100cm'1?,so that the ligand can be transfer energy to rare earth ion,which can be enhanced the luminescence of rare earth ions.Fluorescence spectra and fluorescence lifetimes also showed that the fluorescence intensity and fluorescence lifetime of the rare earth ions were improved by formed the core-shell composite.The rare earth core-shell composites were formed by hydrolysis of the alkoxy groups of the ligands DABA-Si and the siloxanes on the surface of the silica.The SEM and TEM showed that the size of the synthesized SiO₂ sphere was uniform,neat and the surface was smooth.Which the size was about 300 nm.When SiO₂ was bound with rare earth complexes to form rare earth core-shell composites,the surface of SiO₂ becomes rougher and the diameter was increases slightly.In the TEM picture,we can see the obvious core-shell structure,which the inner dark part was SiO₂,the outer gray part of the coated rare earth complexes.The fluorescence spectra and fluorescence lifetime of the rare earth core-shell composites were measured,which indicated that the fluorescence intensity and fluorescence lifetime of all the core-shell structures were enhanced than the corresponding rare earth complexes.The formation of rare earth core-shell composites,which was saved the amount of rare earth,improved the rare earth ions luminescence intensity.The binary core-shell composites of Sm³⁺,Eu³⁺,Tb³⁺ and Dy³⁺ were increased compared with the corresponding complexes of Sm³⁺,Eu³⁺,Tb³⁺,Dy³⁺,the ternary core-shell was stronger than their corresponding ternary complexes,Fluorescence life has also increased.The fluorescence quantum yield of Eu³⁺ binary/ternary core-shell complex was also determined.In this paper,rare earth binary and ternary complexes and the corresponding core-shell composite as the research object,the BSA as a target molecule for luminescence testing.The interaction mechanism between BSA molecules and these rare earth complexes and rare earth core-shell composites was investigated.By calculating the binding constants and binding sites between these rare earth complexes and rare earth core-shell composites and BSA molecules,The quenching mechanism of BSA molecules was static quenching,By comparing these rare earth complexes and rare earth core-shell composite interaction with BSA molecular of combination constant.It made senses to understand the protein in organism metabolism process in the body.