The Preparation Of Sensor Based On Fe/Fe₃O₄ Nanoparticles And Its Application In The Detection Of Pb²⁺ And Cu²⁺

Magnetic nanoparticles(MNPs) are important nanomaterials with multiple fundamental properties, including superparamagnetism, high magnetization, high coercivity, and a macroscopic quantum tunneling effect and can be easily modified by other molecules due to the functionalized groups on their surface, so they have been widely used in food safety, environmental protection, and many other fields.MNPs-based magnetic sensors have many advantages over other sensors, for example,a significant improvement of sensitivity can be obtained by this method, different samples can be detected on the nuclear magnetic resonance instrument simultaneously,it dosen’t require expensive sophisticated instrumentation and complicated sample preparation processes and so on, they have been developed to detect metal ions, small molecules, molecular interactions, proteins, bacteria, viruses and nucleic acids.The experiments are divided into two parts, and we separately studied some applications of 3-(3,4-dihydroxyphenyl)propionic acid modified Fe/Fe3O4nanoparticles(DHCA-Fe/Fe3O4 NPs) and azide dopamine and mPEG-COOH modified Fe/Fe3O4 nanoparticles(N3-Fe/Fe3O4 NPs) in magnetic detection of Pb2+ and Cu2+. The first part is the synthesis and application in detection of Pb2+ of DHCA-Fe/Fe3O4 NPs. Firstly, synthesis Fe/Fe3O4 NPs through the high-temperature pyrolysis method, then DHCA was modified on the surface of nanoparticles by the ligand exchange method to obtain the water-soluble DHCA-Fe/Fe3O4 NPs. Because of the selective coordination interaction between DHCA and Pb2+, Pb2+ can induce the assembly of DHCA-Fe/Fe3O4 NPs accompanied by the decrease then increase in transverse relaxation time(T2) of surrounding water protons. With the concentration of Pb2+ from 40 to 100 ?M and from 130 to 200 ?M, the △ T2 has a linear relationship with Pb2+, respectively. The correlation coefficient were R2 = 0.99825 and R2 = 0.98765. Therefore, the quantitative detection of Pb2+ can be performed in the concentration range of Pb2+ from 40 to 100 ?M and from 130 to 200 ?M. Excellent selectivity was confirmed by the detection of other metal ions. A recovery test wasperformed in tap water and confirmed that this sensor is a powerful tool for the detection of Pb2+ in real samples.The second part is the synthesis and application in detection of Cu2+ of N3-Fe/Fe3O4 NPs. Firstly, synthesis Fe/Fe3O4 NPs through the high-temperature pyrolysis method, then azide dopamine and mPEG-COOH were modified on the surface of nanoparticles by the ligand exchange method to obtain the water-soluble N3-Fe/Fe3O4 NPs, and mixed with Alkyne-PEG-Alkyne to detect Cu2+. Cu+ was derived from the reduction of Cu2+ in the presence of sodium ascorbate and was used as a catalyst in click chemistry, so it can induce the assembly of N3-Fe/Fe3O4 NPs accompanied by the increase in transverse relaxation time(T2) of surrounding water protons. Excellent selectivity was confirmed by the detection of other metal ions.In this work, we detected metal ions by the change of magnetic singal, based on magnetic nanoparticles. This method exhibits a simple, rapid and efficient way for detection of substances, and can be widely applied to detect other species as a general technology based on functionalized magnetic nanoparticles. It enriched the method of detection of Pb2+ and Cu2+, as well as expanded the application range of magnetic nanoparticles.