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Silica‐Coated CaF 2 :Eu 3+ Nanoparticles Functionalized with Oxalic Acid for Bio‐conjugation to BSA Proteins
Author(s) -
Tian Yue,
Hua Ruinian,
Yu Jicheng,
Chen Baojiu,
Sun Jiashi,
Cheng Lihong
Publication year - 2010
Publication title -
chinese journal of chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.28
H-Index - 41
eISSN - 1614-7065
pISSN - 1001-604X
DOI - 10.1002/cjoc.201090172
Subject(s) - chemistry , oxalic acid , nanoparticle , bromide , bovine serum albumin , nuclear chemistry , scanning electron microscope , transmission electron microscopy , cyclohexane , photoluminescence , fourier transform infrared spectroscopy , analytical chemistry (journal) , inorganic chemistry , nanotechnology , chemical engineering , organic chemistry , materials science , chromatography , optoelectronics , engineering , composite material
A new method for silica‐coated CaF 2 :Eu 3+ core‐shell nanoparticles functionalized with oxalic acid for bio‐conjugation to bovine serum albumin (BSA) proteins has been developed. Moreover, CaF 2 :Eu 3+ /SiO 2 core‐shell nanoparticles modified with oxalic acid are biocompatible and can be dispersed in water. As an organic functional molecule, oxalic acid is able to react with hydroxyl groups existed on the surface of SiO 2 layer by esterification reaction to form carboxylic acid for further bio‐conjugation with BSA. The final products were characterized by means of X‐ray diffraction (XRD), transmission electron microscope (TEM), field‐emission scanning electron microscopy (FE‐SEM), ultraviolet (UV) spectrophotometer, infrared (IR) spectrophotometer and photoluminescence (PL) spectra. XRD result confirmed the phase purity of CaF 2 :10 mol% Eu 3+ and CaF 2 :10 mol% Eu 3+ /SiO 2 nanoparticles obtained from the quaternary reverse micelles of cetyltrimethylammonium bromide (CTAB), cyclohexane, n ‐pentanol and water. Images of TEM and FE‐SEM showed that the average grain sizes of CaF 2 :10 mol% Eu 3+ /SiO 2 and bio‐conjugation of CaF 2 :10 mol% Eu 3+ /SiO 2 nanoparticles with BSA were about 17 nm. The patterns of UV and IR spectra showed that BSA was linked to CaF 2 :10 mol% Eu 3+ /SiO 2 nanoparticles. In the emission spectrum of CaF 2 :10 mol% Eu 3+ /SiO 2 conjugated by BSA nanoparticles, characteristic emission peaks of Eu 3+ within the wavelength ranging from 500 to 700 nm were observed, which is corresponding to the transitions from the excited 5 D 0 levels to 7 F J levels. This confirmed that the Eu 3+ dopant ion is located in a Ca 2+ crystal site with T d symmetry. CaF 2 :10 mol% Eu 3+ /SiO 2 conjugated by BSA nanoparticles remain stable in aqueous media within 15 d with pH ranging from 2 to 9. Therefore, these luminescent colloidal nanoparticles can be potentially employed as targeted fluorescent labels in biomedical research applications.