The Application Of Magnetic/photoluminescence Nanohybrid Based On Fe₃O₄ Nanoparticles And Quantum Dots

Magnetic/photoluminescence nanohybrid is a new kind of nanomaterials.Magnetic/photoluminescence nanohybrid not only has good fluorescence,but also has excellent magnetic properties.It can be rapid response to external magnetic field and magnetic targeting migration.Compared to single nanoparticles,multi-function magnetic/photoluminescence nanohybrid caught more and more attention of researchers.In recent years,water-soluble semiconductor nanocrystals?often known as quantum dots?have gained increasing attention?This is because of their supreme characteristics compared to conventional fluorophores,including size-tunable,spectrally narrow light emission,broad excitation spectrum,and well biocompatibility.In chapter 1,we introduced the nanohybrid and its application.Also,we described the basic properties and the prepared methods of quantum dots.We introduced the basic properties,the prepared methods of Fe₃O₄ nanoparticles,and their application in many field.In chapter 2,we designed a novel ratiometric dual-emission fluorescence magnetic nanohybrid.The carbon coated magnetic composite nanoparticles?Fe₃O₄@C NPs?were prepared through the poly-condensation reaction of glucose under hydrothermal conditions.Under proper hydrothermal time,temperature and glucose concentration,the glucose was polymerization and carbonization.So,carbon dots were in situ synthesized in the carbon shell with blue fluorescence due to its surface energy trap emission.Furthermore,the surface of Fe₃O₄@C NPs was endowed with positive charges through modification with Poly?diallyldimethylammonium chloride??PDDA?,and the electrostatic forces could bind electronegative Cd Te quantum dots?QDs?on the Fe₃O₄@C NPs surface?Fe₃O₄@C@QDs?.Carbon shell can keep the stability of internal Fe₃O₄ NPs and inhibit the quenching of Cd Te QDs photoluminescence?PL?.To further demonstrate the performance of nanohybrid as an immunosensor,HIg G was employed as a model target.In a competitive immunoassay,Fe₃O₄@C@QDs was coated with anti-human Ig G.After binding HIg G,HIg G-Au NPs was captured by the restunreacted site of anti-human Ig G on the Fe₃O₄@C@QDs nanohybrid surface and quenched the fluorescenceof Cd Te QDs via fluorescence resonance energy transfer?FRET?.The proposed ratiometric dual-emission?carbon dots and QDs?fluorescence magneticnanohybrid displayed excellent analytical performance for the detection of HIg G in the range of 0.005–100ng/m L with a low detection limit of 0.0025ng/m L.In chapter 3,we have designed a novel kind of nanohybrid with magnetic andphotoluminescence?PL?property for trypsin detection.The modified magnetic Fe₃O₄nanoparticles?MNPs?with polydopamine?PDA?and human serum albumin?HSA?were prepared through a one step self-polymerization under mild condition.Thepolydopamine?PDA?coating on MNPs can improve the biocompatibility of the MNP-PDA-HAS composite due to its hydrophilicity and multifunctional groups.When MNP-PDA-HSA composite was added into the Anti-HSA modified Cd Te QDs?anti-HSA-QDs?,HSA on the MNP-PDA-HSA composite was captured by the site ofanti-HSA-QDs to form MNP-PDA-HSA/anti-HSA-QDs nanohybrid.Therefore,the PL of QDs can be quenched by Fe₃O₄ nanoparticles due to the electron transfer.In thepresence of trypsin,the protein?anti-HSA?was digested by trypsin and QDs wasseparated from the nanohybrid surface.As a result,the PL intensity of QDs wasrecovered.The magnetic/luminescent bifunctional nanohybrid displayed excellentanalytical performance for the detection of trypsin in the range of 0.5–30?g/m L with alow detection limit of 0.25?g/m L.