Organic/Inorganic Hybird Nanoparticles Modified Via Surface-Initiated Living Radical Polymerization

In this thesis, surface-initiated atom-transfer radical polymerization using activators generated by electron transfer (AGET ATRP) mediated by iron catalyst was used to synthesize fluorescent/magnetic hybrid nanoparticles and surface-initiated reversible addition-fragmentation chain-transfer (RAFT) polymerization were used to synthesize SiO₂-supported organic/inorganic hybrid noble metal nanomaterials. The work in this thesis can be summarized as follows:(1) System 1:Inorganic/organic hybrid nanoparticles with fluorescence and magnetism via surface-initiated atom transfer radical polymerization with activators generated by electron transfer (AGET ATRP) mediated by iron catalyst. Fluorescent/magnetic nanoparticles are of interest to many applications in biotechnology and nanomedicine. In this study, a novel method of surface modification of nanoparticles was used to modify a fluorescent monomer on the surfaces of magnetic nanoparticles directly via iron(III)-mediated AGET ATRP. A fluorescent monomer 9-(4-vinylbenzyl)-9H-carbazole (VBK) was synthesized and was grafted from magnetic nanoparticles--ferroferric oxide obtained by co-precipitation method in DMF via AGET ATRP using FeCl₃·6H₂O as the catalyst, tris(3,6-dioxaheptyl)amine (TDA-1) as the ligand and vitamin C (VC) as the reducing agent. The initiator for ATRP was modified onto magnetic nanopaticles with a diameter of 20 nm via a reported method: ligand exchange with 3-aminopropyltriethoxysilane (APTES) and then esterification with 2-bromoisobutyryl bromide. After polymerization, a well defined nanocomposite was yielded with a magnetic core and a fluorescent shell (PVBK). The chemical composite of magnetic nanoparticles surface at different surface modification stages was investigated with Fourier transform infrared (FT-IR) spectra and the magnetic and fluorescent properties also were validated by VSM and fluorophotometer. These magnetic/fluorescent nanocomposites exhibited good potential application in the field of biotechnology and nanomedicine. (2) System 2 : Grafting kinetics and application of SiO₂-supported organic/inorganic hybrid noble metal nanomaterials via surface RAFT polymerization. Benzyl 9H-carbazole-9-carbodithioate (BCBD) immobilized on the surfaces of SiO₂ nanoparticles was used as the RAFT agent to graft 4-vinylpyridine (4VP) via surface RAFT polymerization. The core-shell nanoparticles (SiO₂-P4VP) with P4VP shells were obtained, which can coordinate with various transition metal ions such as Au3+ or Ag+, and therefore stabilize the corresponding Au or Ag nanoparticles reduced in situ by sodium borohydride (NaBH4) or trisodium citrate. The grafting kinetics of 4VP polymerization was studied in the presence of free RAFT agent BCBD. The Au or Ag nanoparticles embedded in the P4VP shell layer were characterized by surface-enhanced Raman spectroscopy (SERS).