Preparaton And Fluorescence Properties Of ATPA-Si Rare Earth Core Shell (SiO₂@ATPA-Si-RE-L) And Core Shell Shell (SiO₂@ATPA-Si-RE-L@SiO₂) Structured Nanocomposites And Their Interaction With BSA

With the development of science and technology,the core shell shell structured nanocomposites have shown high application value in the fields of display,biological nanotechnology,electroluminescence and biological imaging due to their excellent luminescence properties and photostability,and have attracted widespread attention.SiO₂has the advantages of low price,low cytotoxicity and easy preparation,and its surface is rich in Si-OH,which provides a binding site with other functional materials,and is one of the frequently used core shell materials.Inthisthesis,anovelbifunctionalligand(HOOC)₂C₆H₃NHCONH(CH₂)₃Si(OCH₂CH₃)₃(ATPA-Si)was synthesized.The ligand ATPA-Si has two-COOH groups and-OC₂H₅group in structure,which provides coordination sites for rare earth ions Eu³⁺and Tb³⁺and can hydrolyze and condensation with Si-OH on the surface of SiO₂microspheres respectively.Then the core shell structured binary nanocomposites SiO₂@ATPA-Si-Tb and SiO₂@ATPA-Si-Eu were synthesized using SiO₂microspheres as the nucleus and ATPA-Si as ligand.And the core shell structured binary nanocomposites with codoped Eu³⁺and Tb³⁺SiO₂@ATPA-Si-Eu_(x)Tb_(1-x)(x=0.17,0.29,0.58 mmol)were synthesized.In addition,four core shell structured ternary nanocomposites SiO₂@ATPA-Si-RE-L(L=phen/dipy)were synthesized by adding the second ligand phen and dipy.Then,four core shell shell structured ternary nanocomposites SiO₂@ATPA-Si-RE-L@SiO₂were prepared by TEOS hydrolytic deposition method.The morphology and composition of the products were analyzed by transmission electron microscopy(TEM),scanning electron microscope(SEM),infrared spectroscopy(FT-IR),ultraviolet visible spectroscopy(UV-Vis),X-ray photoelectron spectroscopy(XPS),thermogravimetric differential scanning calorimetry(TGA)and X-ray energy spectroscopy(EDS).TEM images showed that all the core shell structured and core shell shell structured nanocomposites are monodispersed and spherical structure in uniform size.The diameter of the SiO₂core is about 125 nm,the thickness of the shell of the rare earth complex is about 2-5 nm,and the thickness of the outer SiO₂shell is about 15 nm.When synthesizing SiO₂@ATPA-Si,the p H value of the hydrolysis and condensation reaction system was 2,the shell layer thickness(the thickness of rare earth complex)of the core shell structured complex SiO₂@ATPA-Si-Tb and SiO₂@ATPA-Si-Eu was about 2 nm.When the p H of the system was 7,the shell layer thickness of the synthesized SiO₂@ATPA-Si-Tb and SiO₂@ATPA-Si-Eu was about 5 nm.Fluorescence spectra of core shell structured nanocomposites and core shell shell structured nanocomposites showed that all the core shell structured nanocomposites have good luminescence properties and long fluorescence lifetime.With the second ligand added,the fluorescence emission intensity of core shell structured ternary nanocomposites was stronger than that of the corresponding core shell structured binary nanocomposites.When the second ligand phen was added,the fluorescence emission intensity of the core shell structured ternary nanocomposites of Tb³⁺and Eu³⁺were increased by 1.16 and 1.70 times compared with those of core shell structured binary nanocomposites,respectively.When the second ligand dipy was added,the fluorescence emission intensity of core shell structured ternary nanocomposites of Tb³⁺and Eu³⁺were increased by 1.08 and1.65 times compared with those of core shell structured binary nanocomposites,respectively.In addition,the fluorescence emission intensity of core shell shell structured nanocomposites is stronger than that of core shell structured nanocomposites.The fluorescence emission intensity of core shell shell structured ternary phen nanocomposites of Tb³⁺and Eu³⁺is 1.38 and 1.24 times higher than that of the corresponding core shell structured ternary nanocomposites.The fluorescence emission intensity of core shell shell structured ternary dipy nanocomposites of Tb³⁺and Eu³⁺is 1.44 and 1.11 times higher than that of the corresponding core shell structured ternary nanocomposites.The enhancement of fluorescence emission intensity is mainly due to the outer silica shell can effectively reduce the energy loss of the organic ligand vibration,and also protect the rare earth complex from the influence of external conditions.The core shell structured complex SiO₂@ATPA-Si-Eu_(0.17)/Tb_(0.83)emitting warm white light region was obtained by adjusting the proportion and thickness of rare earth ions Eu and Tb.This paper,the fluorescence properties of the core shell shell structured ternary nanocomposites were also studied for the aqueous solution.It was found that the fluorescence emission intensity of the core shell shell structured ternary nanocomposites was stable in aqueous solution after a few days.Finally,the interaction of four core shell shell structured ternary nanocomposites with bovine serum albumin(BSA)was studied.The results showed that the core shell shell structured ternary nanocomposites all have a certain fluorescence quenching effect on BSA.And the quenching constants of the core shell shell structured ternary nanocomposites decrease with the increase of temperature.Combining with literature,the quenching mechanism is static quenching.The synchronous fluorescence spectra showed that core shell shell structured ternary nanocomposites have a quenching effect on the tryptophan and tyrosine residues of BSA.The binding site of core shell shell structured ternary nanocomposites and BSA is closer to tryptophan.It is showed that the core shell shell structured nanocomposites had the fluorescence labeling effect on BSA,which provides a reference for other applications in the field of biomedical labeling.