Preparation,Properties And Application Of Responsive Coordination Polymer Functionalized Graphene Oxide Fluorescent Hybrids

Graphene,as a newly discovered two-dimensional nanomaterial composed of sp2-bonded carbon atoms,is called as "the thinnest material in our universe".Due to its fascinating optical,electronic,thermal,and mechanical properties which arised from its honeycomb structure,graphene has attracted widespread attention of researchers from chemistry and material fields.Graphene oxide(GO),a derivative of graphene,has the similar honeycomb structure and fascinating properties with graphene.Moreover,there are lots of oxygen-containing functional groups as epoxide,alcohol and carboxylic acids on the surface of GO.These abundant oxygen-containing functional groups can be used as active sites in many chemical reactions,therefore,giving GO a lot of opportunities for further chemical modification.Taking using of the oxygen-containing functional groups to modify with some responsive polymer,small organic molecules or nanoparticles which have certain function in the surface of GO have extremely meaning in the functionalization and applications of GO.In this thesis,GO was chosen as scaffolds to be functionalized with thermo-responsive polymer using convent and non-convent methods,followed by the coordination between polymer and metal ions,metal nanoparticles or semiconductor quantum dots to construct GO based fluorescent hybrids.Four parts of works in this thesis were carried out as follows:1.The copolymer brushes of P(OEGMA-co-MQ)were grafted from the surface of GO by reversible addition-fragmentation chain transfer(RAFT)polymerization based on the monomers of oligo(ethylene glycol)monomethyl ether methacrylate(OEGMA)and 5-(2-methacryloyl-ethyloxymethyl)-8-quinolinol(MQ).Au NPs were generated via in situ reduction of Au3+ by alkali and the 8-hydroxyquinoline units in the copolymer brushes were used as capping agent to stabilize Au NPs.The obtained Au NPs-GO hybrids exhibited weak blue fluorescent emission at 475 nm and high catalytic activity in water for the reduction of 4-nitrophenol(4-NP).It was also found that the GO sheets could enhance the catalytic activity via a synergistic effect.2.Thermo-responsive block copolymer brushes of PNIPAM-b-P(MQ-co-GMA)were successfully grafted from graphene oxide(GO)by consecutive reversible addition-fragmentation chain transfer(RAFT)polymerization based on the monomers of N-isopropylacrylamide(NIPAM),5-(2-methacryloyl-ethyloxymethyl)-8-quinolinol(MQ)and glycidyl methacrylate(GMA).The 8-hydroxyquinoline units in the polymer brushes could coordinate with Al3+ to form the green luminescent copolymer brushes containing tris(8-hydroxyquinoline)aluminum(Alq3)side chains on the GO surface.The resulting fluorescent hybrid could be used as a nano-platform for the sensitive and robust detection of 2,4,6-trinitrophenol(TNP).The strong green fluorescence of the polymer brushes modified GO hybrid in aqueous solution could be quenched by TNP via charge transfer process and the observed linear fluorescence intensity change allowed the quantitative detection of TNP with a detection limit down to 2.38×10-9 M.The fluorescence nanohybrids exhibited the temperature-responsive behavior as a result of the conformation change in PNIPAM chains of polymer brushes.3.Thermo-responsive block copolymer brushes modified graphene oxide(GO)nanosheets were successfully prepared via non-covalent ?-? stacking interaction of GO and pyrene-terminated PNIPAM-b-P(OEGMA-co-MQ).The pyrene-terminated block copolymer was synthesized using reversible addition fragmentation chain transfer(RAFT)polymerization based on the monomers of N-isopropylacrylamide(NIPAM),5-(2-methacryloyl-ethyloxymethyl)-8-quinolinol(MQ),oligo(ethylene glycol)monomethyl ether methacrylate(OEGMA)and a pyrene functional RAFT agent.The MQ units in the block copolymer brushes could coordinate with amine groups functionalized ZnS nanoparticles(ZnS-NH2 NPs)to form a fluorescent sensing platform for the sensitive and robust detection of 2,4,6-trinitrotoluene(TNT).The resulting fluorescent hybrid could be quenched by TNT via a fluorescence resonance energy transfer(FRET)and the observed linear fluorescence intensity change allowed the quantitative detection of TNT with a detection limit down to 4.4 nM.In addition,the fluorescence nano-hybrids exhibited a robust temperature-responsive behavior as a result of the conformation change in PNIPAM chains of block copolymer brushes.4.?-Cyclodextrin modified GO nanohybrids were first prepared via the amidation between the amino-modified ?-cyclodextrin and the carboxyl group on the surface of GO.Secondly,azobenzene-terminated RAFT chain transfer agent was synthesized by esterification reaction,and then the azobenzene-terminated amphiphilic block copolymer P(NIPAM)-b-P(St-co-MQ)was synthesized via RAFT polymerization.At last,we prepared the fluorescent hybrid materials with independent double channel emission via the host-guest interaction between the azobenzene on the block copolymer and the ?-cyclodextrin on the surface of GO,followed by the coordination between the 8-hydroxyquinoline units of block copolymer brushes and CdSe/ZnS duantum dots with red-light emission.The results suggested that the block copolymer and duantum dots have been successfully functionalized on the surface on GO and the PL intensity of the rusulting hybrids changed step by step as a function of temperature.What's more,the change exhibited dual reversible PL properties.Other characterizations of the work are still in progress.