Study On Synthesis, Functionalization And Application Of Magnetic Nanoparticles

After magnetic nanoparticles were synthesized successfully in 1960s, the synthesis and application of magnetic nanoparticles have been obtained rapidly development in rescent years, especially the application of magnetic nanoparticles are of great interest for researchers in biomedicine and environmental separation and analysis. In the following ,we focus mainly on the synthesis, characterization and the environmental application of magnetic-fluorescent bifunctional nanocomposites based on surface modification by polyacrylic acid.Magnetic Fe₃O₄ nanoparticles of 7±2nm are prepared by chemical co-precipitation, and corresponding stability without agglomeration magnetic colloids are obtained via treatmeng by dilute hydrochloric acid. Magnetic Fe₃O₄ nanoparticles are superparamagnetic and have a saturated magnetization of 42.9 emu g^-1 at room temperature. The optimal condition for preparation of Fe₃O₄ nanoparticles as following : a) molar ratio of Fe(â…¡)/Fe(â…¢) is 1 : 2; b) precipitation agent is NaOH; c)dispered in the 20 mmol/L HCl.Carboxylated Magnetic Fe₃O₄ (Fe₃O₄@PAA) nanoparticles were synthesized by in-situ polymerized acrylic acid onto the surface of Fe₃O₄ nanoparticle,then Fe₃O₄-fluorescent bifunctional nanocomposites (Fe₃O₄@PAA-RB) were synthesized by covalently bound rhodamine B onto the carboxylated Magnetic Fe₃O₄ nanoparticles via ethanediamine as linker molecules.The carboxylated Fe₃O₄ nanoparticles and Fe₃O₄-fluorescent bifunctional nanocomposites have a typical diameter of 6-10 nm. Fe₃O₄@PAA and Fe₃O₄@PAA-RB are superparamagnetic, and their saturation magnetization was 40.6 emu g-1 and 39.2 emug-1 respectively. The optimal conditions for preparation of Fe₃O₄-fluorescent bifunctional nanocomposites as following: (1) molar ratio EDA/RB is 1:1, (2) the concentration of acrylic acid monomer is 150 mmol/L in the reaction system,(3) the concentration of EDC (NHS) is 75 mmol/L in the reaction system, (4) covalent binding times are 45 min between amide-RB and Fe₃O₄@PAA. Under optimal condition, polyacrylic acid and Fe₃O₄ ratio is 1:2 w/w, 10 RB molecules were bound onto per Fe₃O₄. Superparamagnetic/fluorescent nanocomposites were synthesized based on surface modification by polyacrylic acid, which have a good dispersity in solution and high fluorescent signal. The new magneto-fluorescent nanoagent has great practical applications for environment, biological and medical uses.The magneto-fluorescent nanocomposites have the properties of controllability, easy impurities and high fluorescent singal, which can be applied to detect anionic surfactants in aqueous solution and realized the high sensitive detection of anionic surfactants. Under optimal conditions, the detection limit is 0.051μmol/L for SDS. The relative standard deviation for the determination of 4.0μmol/L SDS is 3.32% and has a good reproducibility.