Bifunctional Magnetic-fluorescent Polymer-rare Earth Complex And Its Covalent Loading On Single-walled Carbon Nanotube

Magnetic-fluorescent material（MFM）, owing to its dual signal detectability, has great prospects in many hi-tech fields, such as fluorescence imaging, magnetic separation,target identification, and nuclear magnetic resonance imaging. Carbon nanotube（CNT）,owing to its super high specific surface area and excellent electrical/ thermal conductivity,biocompatibility, and chemical stability, has been widely used as nano-carrier. Therefore,it is highly promising to develop new target nanomaterials with more excellent performance and wider application fields by appropriate combination of MFM with CNT.In this work, a new polymer-based MFM（MFP） was developed with its chemical structure as polymer-rare earth complex, in which Dy³⁺ was chosen as the rare earth element. To validate the feasibility of such molecular design for development of MFP, the study on MFP-DB, which was prepared by complexing of Dy³⁺ with a bipolymer of1-vinylimidazole-co-polyethylene glycol monoacrylate, was firstly carried out.Subsequently, for clarifying the effect of molecular structure of polymer ligand on magnetic and fluorescent properties so that MFP with the expected performance could be prepared, MFP-TB was designed and prepared by complexing of Dy³⁺ with a terpolymer of 1-vinylimidazole-co-diisopropyl-p-vinylbenzyl phosphonate-co-polyethylene glycol monoacrylate. The studies performed on MFP-DB and MFP-TB demonstrated:1) Both MFPs possess the bifunctional magetic-flurescent performance.2) Both magnetic and fluorescent properties of these two MFPs exhibit the strong dependence on the Dy³⁺ content([Dy³⁺]). The magnetic response ability improves with the increase of [Dy³⁺], but the light response ability reaches the maximam at [Dy³⁺] = 13.7wt% for MFP-DB and [Dy³⁺] = 18.4 wt% for MFP-TB.3) After being excited at 510 nm, both MFPs exhibit the strong fluorescence withdistinct peaks at 575, 622, 768, and 830 nm. Among them, the intensities of the peaks centered at 622 and 830 nm are relatively weaker and have no dependence on [Dy³⁺].4) Both MFPs are of superparamagnetism with the magnetic susceptibility up to6.0×10-5 emu/g at [Dy³⁺] = 30.8 wt%.5) When [Dy³⁺] of MFP-DB is basically comparable to that of MFP-TB, MFP-DB shows the higher fluorescent emission intensity at 768 nm, while MFP-TB displays the higher intensity at 575 nm.Finally, taking MFP-DB as a typical example, MFP was covalently loaded on the surface of single-walled carbon nanotubes（SWNTs） through an esterification reaction.When [Dy³⁺] of MFP-DB（21.3 wt%） is comparable to that of MFP-DB-g-SWNT（20.9wt%）, both samples show the nearly identical fluorescent emission intensities at 575 nm,but the intensity at 768 nm of MFP-DB-g-SWNT is weaker than that of MFP-DB. The qualitative study suggests that MFP-DB-g-SWNT is more sensitive to external magnetic field（0.3 T） as compared with MFP-DB.In summary,this work presents a new type of MFP that was prepared by using cheap and commercially available chemicals through an ingenious molecular design,and has realized the covalent loading of MFP on the SWNT surface.As such,a new method for developing the multifunctional polymer-based nanomaterial is at hand.