Design And Synthesis Of Novel Coordination Functional Polymers And Construction And Properties Of Their Nanohybrid-assembled Systems

Fluorescent nanoparticles in nanometer scale including metal nanoclusters（MNCs）,semiconductor quantum dots（QDs）,and perovskite quantum dots（PQDs）have special fluorescent properties,strong quantum size effects and surface effects.Compared to traditional fluorescent dyes,these fluorescent nanoparticles exhibit many special chemical and optical properties,such as high fluorescence quantum yield（QY）,narrow fluorescent emission peak,and size dependence of emission wavelength.In addition,these nanoparticles have high surface to volume ratio,and most of the atoms are located on the surface of the particles,which is easy to further surface functionalization.Hybrid assembly of polymers and nanoparticles has always been a research hotspot in nanoscience.In organic-inorganic hybrid system,coordination functional polymers not only can be used as ligands to control the size and morphology of in-situ formed nanoparticles,but also may endow the nanoparticles with new special functions,to realize the integration and enhancement of their functions,showing excellent properties in the fields of optoelectronic devices,detection and catalysis.And the coordination functional polymers can further regulate the distribution of nanoparticles in three-dimensional space,and then control the interaction between nanoparticles,and ultimately control the properties.In this thesis,a series of novel multifunctional polymers（including block copolymers,BCP）containing 8-hydroxyquinoline（HQ）ligands were designed and synthesized,and their coordination and assembly functions were used to prepare polymer-stabilized fluorescent silver nanoclusters（Ag NCs）,gold nanoparticles（Au NPs）,fluorescent semiconductor quantum dots（QDs）and perovskite quantum dots（PQDs）.It is intended to construct the multifunctional integrated inorganic nanoparticle/polymer hybrid assembly systems with controllable assembly morphology,adjustable fluorescence and thermo-responsive properties.The main research contents of this thesis are as follows:（1）A random copolymer ligand（RCPL）with HQ units and temperature-sensitive isopropylacrylamide（NIPAM）monomer units was synthesized and utilized to prepare RCPL-stabilized silver nanoclusters（Ag NCs）via in situ reduction route with the aim of the coordination function of HQ units.The effects of pH and the ratio between[Ag⁺],[RCPL],and[Vc]on the morphology and fluorescence properties of the assembly were systematically investigated.The results showed that the obtained silver nanoclusters exhibited single spherical and chain-like self-assembly structure,which is induced by the coordination of copolymer chains.In addition,we explored the fluorescence emission mechanism of RCPL-Ag NCs,revealing that the green light emission is related to silver ions adsorbed on the surface,and the fluorescent mechanism is the surface silver ion aggregation induced emission.The RCPL-Ag NCs exhibited a good response to temperature and pH,and this response is reversible.In the range of pH=3.04-5.25,the fluorescence intensity of RCPL-Ag NCs has a good linear relationship with pH and can be applied to pH fluorescence detection in this range.At the same time,the catalytic activity and temperature-sensitive catalytic properties of RCPL-Ag NCs were also investigated for the reduction of p-nitrophenol.（2）A series of novel well-defined 8-hydroxyquinoline（HQ）-containing thermoresponsive amphiphilic diblock copolymers P（St-co-MQ）-b-PNIPAm（P1,2）,P（NIPAm-co-MQ）-b-PSt（P3,4）and triblock copolymer PNIPAm-b-P（MMA-co-MQ）-b-PSt（P5）were prepared by reversible addition-fragmentation chain-transfer（RAFT）polymerization from the monomers of styrene（St）,N-isopropylacrylamide（NIPAm）,5-（2-methacryloylethyloxymethyl）-8-quinolinol（MQ）and methyl methacrylate（MMA）,and their self-assembly behaviors were studied.Block copolymer P1-P5-stabilized gold nanoparticles（Au@P1-Au@P5）with a small size and a narrow distribution were obtained through the in situ reduction of gold precursors in an aqueous solution of polymer micelles with HQ as the coordination groups.In particular,Au@P4 stabilized by P4 with a longer hydrophobic segment exhibited a nanowire structure.The resulting Au@P nanohybrids possessed excellent catalytic activity for the reduction of nitrophenols using NaBH₄.The size,morphology,and surface chemistry of Au NPs could be controlled by adjusting the structure of block polymers with HQ in different block positions,which plays an important role in the catalytic properties.It was found that longer chain lengths of hydrophilic or hydrophobic segments of block copolymers were beneficial to elevating the catalytic activity of Au NPs for the reduction of nitrophenols,and the catalytic performance of the triblock copolymer-stabilized spherical nanoparticles（Au@P5）was higher than that of the diblock copolymer-stabilized spherical nanoparticles Au@P1-Au@P3.Surprisingly,the gold nanowires（Au@P4）produced with P4 have the highest catalytic activity due to a large abundance of grain boundaries.Excellent thermoresponsive catalytic performance of the as-prepared Au@P hybrids makes them an environmentally responsive nano-catalytic material.（3）Using the characteristics of coordination function and coordination luminescence of HQ as well as different positions of the HQ coordination unit in the amphiphilic block copolymers（BCPs）synthesized in the previous chapter,the hydrophilic/hydrophobic QDs were precisely positioned in the core（CDMs）,shell（SDMs）and the interface between the core and the shell（IDMs）in the BCP micelles via a coordination-driven assembly process,resulting in a variety of assemblies,and the effect of the content of QDs on the self-assembly behaviors in the QDs/BCP assemblies was systematically studied.The QDs/BCP hybrid assemblies also possessed dual-emitting properties,namely the inherent emission of the QDs（red-emission,>600 nm）and the HQ–Zn complex emission on the surface of the QDs（green-emission at 517 nm）.The effect of temperature-sensitive polymers on the dual-emitting properties was investigated.The as-constructed SDMs hybrid with double channel emission can be applied to the selective ratiometric fluorescence detection of explosive picric acid（TNP）and Hg²⁺with detection limits of 1.27μM and 500 nM,respectively.（4）A new strategy for the preparation of stable and water-dispersible perovskite quantum dots（PQDs,CsPbBr₃）was developed by one-pot route.During the formation of PQDs,a hydrophobic protective shell layer of SiO₂ was formed in the outer layer of PQDs by co-hydrolysis and condensation of aminosilane coupling agent（APTES）and fluorocarbon silane coupling agent（PFMS）to improve stability of PQDs in water.At the same time,the hydrophilic polyethylene glycol（PEG-NH₂）was grafted onto the surface of PQDs by amino-terminal coordination,which gives PQDs good hydrophilicity and water dispersibility.The as-prepared PQDs exhibited a high absolute photoluminescence quantum yield（PLQY）of～43%,and narrow band emission（FHWM～26 nm）.Compared with the SiO₂-stabilized PQDs reported in the literature,our proposed method is very simple,and the obtained PQDs still retained76%of fluorescence after being stored in water for 162 h,and have good water dispersion stability.Further research and characterization for the PQDs is underway.