Preparaton And Fluorescence Properties Of Core Shell（SiO₂@AIPA-S-Si-RE-L） And Core Shell Shell Structure Nanocomposites（SiO₂@AIPA-S-Si-RE-L@SiO₂） And Their Interaction With BSA

In this paper,a novel bifunctional organic ligand（（HOOC）₂C₆H₃NHCONH（CH₂）₃Si（OCH₂CH₃）₃）was synthesized from5-aminoisophthalic acid（AIPA）and propyl isocyanate triethoxysilane（TEPIC）,defined as AIPA-S-Si.Secondly,silica microspheres with a diameter of about 180 nm were prepared by the classical St?ber method.Then,the first ligand was successfully grafted onto the surface of the SiO₂ microspheres through the hydrolysis condensation of the silicon hydroxyl groups on the surface of the silica microspheres and the alkoxy groups on the first ligand AIPA-S-Si.Then,the four rare earth ions of samarium,europium,terbium,and dysprosium coordinate with the two carboxyl oxygen atoms on the ligand（AIPA-S-Si）on the surface of the modified silica microsphere to form four binary SiO₂@AIPA-S-Si-RE（RE=Sm,Eu,Tb,Dy）core shell structure nanocomposites with good luminescence properties.Under the action of template CTAB,SiO₂ was deposited on the surface of the core shell structure nanocomposite by TEOS hydrolysis method,and four kinds of binary SiO₂@AIPA-S-Si-RE@SiO₂ core shell shell structure nanocomposites were prepared.In addition,the second ligands phen and dipy were added to the binary core shell structure nanocomposite to prepare ternary SiO₂@AIPA-S-Si-RE-L（L=phen/dipy）core shell structure nanocomposite with better light emission.Similarly,ternary core shell shell structure nanocomposites SiO₂@AIPA-S-Si-RE-L@SiO₂ were prepared by the method of hydrolytic deposition of TEOS.By Fourier transform infrared spectroscopy（FT-IR）,ultraviolet-visible spectroscopy（UV-Vis）,thermogravimetric analysis（TG）,X-ray powder diffraction（XRD）,scanning electron microscope（SEM）,transmission electron microscope（TEM）and energy Dispersive X-ray energy spectroscopy（EDX）and other characterization methods were used to analyze the composition and micro-morphology of the prepared nanocomposites.Among them,it can be seen through scanning and transmission electron microscopy that all the core shell and core shell shell structure nanocomposites exhibit uniform and well-dispersed spheres.Thermogravimetric analysis shows that the core shell and core shell shell structure nanocomposites have good thermal stability.In addition,the prepared nanocomposites were mainly tested by fluorescence spectroscopy.Fluorescence spectra show that all core shell and core shell shell structure nanocomposites have excellent luminous intensity and long fluorescence lifetime.Among them,the ternary core shell structure nanocomposite has better luminous intensity than the binary core shell structure nanocomposite.Specifically,compared with the binary core shell structure nanocomposites,due to the addition of the second ligand phen,the ternary core shell structure nanocomposites of Sm,Eu,Tb,and Dy increased by 2.05,1.48,1.25 and 1.40 times,respectively.Due to the addition of the second ligand bipy,the ternary core shell structure nanocomposites of Sm,Eu,Tb,and Dy are increased by 2.52,1.48,1.46 and 1.13 times,respectively.Since the addition of the second ligand phen and bipy can also synergistically sensitize the rare earth ion to emit light,the ternary nanocomposite has a higher fluorescence intensity than the binary nanocomposite.Moreover,the prepared binary and ternary core shell shell structure nanocomposites have stronger luminous intensity than the corresponding core shell structure nanocomposites.Among them,the Sm,Eu,Tb,Dy binary core shell shell structure nanocomposites were increased by 2.68,1.67,1.46,1.46 times compared with the corresponding core shell structure nanocomposites.The ternary phen core shell structure nanocomposites are 1.26,2.20,1.87 and 1.34 times higher than the corresponding core shell structure nanocomposites,respectively.The ternary dipy core shell structure nanocomposites were increased by 1.89,1.10,1.92,and 1.29times higher than the corresponding core shell structure nanocomposites,respectively.This further illustrates that the silica shell can reduce the energy loss when the organic ligand molecules vibrate,and protect the rare earth complexes from the external environment,thereby increasing the fluorescence intensity.In addition,the core shell shell structure nanocomposites with still showed good luminescence stability when they were left in aqueous solution for different time.This paper also explores the interaction of Eu,Tb,Dy binary and ternary core shell shell structure nanocomposites with bovine serum albumin（BSA）.The data show that BSA and core shell shell structure complexes have mutual quenching effect.Its emission spectrum has been reduced to varying degrees,but the position of the emission peak has not changed,further indicating that the core shell shell structure nanocomposite interacted with BSA.However,it was found from the BSA fluorescence spectrum that its characteristic peaks did not shift,indicating that the conformation of BSA did not change at all.This further indicates that the core shell shell nanocomposite has a good fluorescent labeling effect,which also provides new research ideas for the preparation of fluorescent probes.In addition,the thickness of the core shell and core shell shell nanocomposite light-emitting layers is only on the order of nanometers,which can save rare earth resources and reduce production costs in the actual production process.In addition,the surface of the core shell shell structure nanocomposite contains a large amount of Si-OH,which can attach many biological macromolecules.Therefore,core shell and core shell shell structure nanocomposites have potential applications in the fields of biology and luminescence.