Porphyrin-based Metalllopolymers As Precursors For Synthesis Of Multifunctional Magnetic Nanoparticles And Their Applications

Metallic nanomaterials have many unique physical and chemical properties due to their nanometer size, and have attracted more and more research interest. Metallic nanoparticles(NPs) have already been widely used in many fields, for example, permanent magnets, ultra high-density magnetic information storage, magnetic resonance imaging, medicine transportation, biosensor, recyclable catalyst, etc. In recent years, researchers have also applied the metallic NPs in new arising areas through some novel methods, such as metal-containing polymers as precursors for the synthesis of nanopatterned metallic NPs via nanoimprint lithography and thermal or radiation treatment, which are desirable in the field of ultra-high-density information storage. Beside, due to the magnetic properties and surface plasmonic effect of metallic NPs, researchers have tried to dope these NPs into OLED and solar cells which can effectively improve the device performance. Metallic alloy NPs are of special properties due to their unique composition and structure, which is not existed in monometallic NPs. As far as the synthetic methods of metallic alloy nanoparticles are concerned, the alloy NPs are usually prepared by controlled pyrolysis of physically mixed precursors with different metal atoms. But the particle size of the as-prepared NPs in this way is uncontrollable and unstable. Moreover, some undesirable phenomena such as agglomeration and sintering, etc. are always concommitant. In this thesis, we designed and synthesized a series of heterobimetallic and monometallic polymers which can be used as single-source precursors for fabrication of bit patterrned medium by nanoimprint lithography for application in ultra high-density magnetic recording system. At the same time, we have also attempted to use the as-synthesized surface carbon-coated magnetic NPs to improve the performance of OLED devices. The main content of this thesis includes:(1) Design and synthesis of porphyrin-based metallopolymers. Here, we have synthesized a series of metalloporphyrin by taking advantage of the template effect of porphyrin compounds(DETPP-Fe, DETPP-Co and DETPP-Ni). Moreover, we also synthesized Pt-containing ligand and fluorenyl-based ligands. After coupling the metalloporphyrin with the above ligands, a series of heterobimetallic polymers(DETPP-PFePt, DETPP-P-CoPt and DETPP-P-NiPt) and monometallic polymers(DETPP-P-Fe, DETPP-P-Co and DETPP-P-Ni) were synthesized. The structure and properties of the above metallopolymers were well characterized by nuclear magnetic resonance(NMR), UV-Vis spectroscopy(UV-Vis), infrared spectroscopy(FT-IR) and thermogravimetric analysis(TGA).(2) The surface carbon-coated NPs(NP-Fe@C, NP-Co@C, NP-Ni@C, NP-FePt@C, NP-Co Pt@C and NP-NiPt@C) were prepared via controlled pyrolysis of the as-synthesized metallopolymers. The structure, composition and properties of the as-generated NPs were characterized by powder X-ray diffraction(PXRD), transmission electron microscopy(TEM), energy dispersive spectrometer(EDS) and vibrating sample magnetometer(VSM). The results indicate that NP-FePt@C and NP-Co Pt@C are L10 structured NPs, NP-Fe@C and NP-Co@C are fcc-structured NPs and NP-Ni@C is simple cubic-structured NP. According to the analysis of TEM measurements, we knew that the average particle diameters of NP-FePt@C, NP-Co Pt@C, NP-NiPt@C, NP-Fe@C, NP-Co@C and NP-Ni@C are 9.9 nm, 3.4 nm, 7.7 nm, 11.8 nm, 13.2 nm and 15.7 nm, respectively. And the size distributions of these NPs are relatively narrow. Through the VSM measurements, we found that the coercivities of NP-FePt@C are 0.54 T at 300 K and 1.12 T at 5 K. The coercivity of NP- Co Pt @C are 0.54 T at 300 K and 2.75 T at l5 K, which implies that, NP-FePt@C and NP-Co Pt@C have great application perspectives in ultra high-density information storage devices. However, the NP-Fe@C, NP-Co@C and NP-Ni@C are superparamagnetic.(3) Bit patterned medium based on ferromagnetic alloy nanoparticles were fabricated by nanoimprint lithography with the blend of as-synthesized metallopolymers DETPP-P-CoPt and PS as single-source precursor. Here, we used the hard AAO template and soft PDMS template pre-defined with nanostructures for nanoimprinting. The nanodot array with periods of 550 nm and 100 nm, and nanoline array with period of 550 nm were prepared, respectively. After pyrolysis of the above nanostructured arrays, we found that the patterns have no significantly change. Therefore, this method is hopeful to be applied in the ultra high-density magnetic information storage.(4) We have tentatively tried to dope NP-Co Pt@C into the hole transport layer of OLEDs to improve the performance of the devices by taking advantage of the surface plasmonic effect and magnetic effect of the NPs.