| Because of the unique structural features,Noble metal nanomaterials have physical and chemical properties that are not possessed by some conventional bulk metal materials,including optical,electrical,magnetic,and mechanical properties.They have been widely used in catalysis,electronics,photonics,and information storage,sensing,imaging,and biomedical applications.Metal nanoclusters are a new kind of luminescent nanomaterials,which are generally composed of only a few atoms.Compared with traditional fluorescent dyes such as organic dyes and quantum dots,Metal nanoclusters have such advantages as high stability,good biocompatibility,ultra-small size,low toxicity,and strong fluorescence emission.Metal-polymer nanocomposites have been successfully prepared and become a new generation of antibacterial material.Their synergy and complementarity can enhance the antibacterial activity of a single antibacterial agent and improve its antibacterial performance.In this study,fluorescence sensors based on two-dimensional noble metal nanomaterials and silver nanoclusters are utilized for the detection of biomolecules,and AgNPs-cationic UV waterborne polyurethane composite coating is prepared for antibacterial research.（1）The structure,morphology and size of noble metal nanomaterials have great influence on their performance.The two-dimensional noble metal nanomaterial Pd@Au nanoplates have uniform hexagonal morphology and strong near-infrared（NIR）absorption peak.Pd@Au nanoplates with tunable sizes were synthesized through a seeded regrowth method.These nanoplates not only possess good water solubility and large specific surface area,but also exhibit different affinity toward single-stranded DNA（ssDNA）and double-stranded DNA（dsDNA）.Furthermore,the fluorescence can be quenched by fluorescence resonance energy transfer（FR ET）.Moreover,Pd@Au nanoplates themselves exhibit no fluorescence emission,which makes no background interference.For this reason,Pd@Au nanoplates are considered to be promising nanomaterials for sensor design.Therefore,in Chapter 2,we constructed for the first time a fluorescence sensing platform for sensitive detection of DNA and small molecules using Pd@Au nanoplates.The feasibility and size-dependent sensing performance as well as the sensitivity and selectivity toward the target substance were discussed.Firstly,Pd@Au nanoplates showed different adsorption toward the dye-labeled ssDNA and the formed dsDNA after hybridization with target,and the remarkable fluorescence intensity change could be used as a basis.Based on quenching ability and dynamic process analysis,80 nm Pd@Au nanoplates were selected for the detection of DNA and small molecules.The sensor showed a good linear relationship with DNA in the range of 0.02 nM-50 nM,and the detection limit was 20 pM.At the same time,it also achieved good detection sensitivity for ATP and Hg2+.The method is simple in design and versatile,and provides a platform technology for rapid and sensitive detection of biomolecule s.（2）Biothiols play an important role in many physiological and metabolic processes.Quantitative detection of biothiols can serve as a reference in the diseases prevention and diagnosis,and it is of great significance in human life activities.In Chapter 3,we constructed a label-free ratiometric fluorescent probe for the detection of biothiols based on the superior biological properties of tetrahedral DNA nanostructures（TDNs）and silver nanoclusters（AgNCs）.The probe consisted of three parts:DNA tetrahedron as a delivery vehicle;cytosine-rich sequence as the synthetic template of AgNCs;intercalating dye Acridine Orange（AO）as a reference signal.In the presence of biothiols,biothiols would replace and quench the fluorescence of AgNCs due to the strong interaction of Ag-S bonds,while the fluorescence intensity of AO remained unchanged.The ratio of fluorescence intensity of AgNCs and AO could be used as a basis for the quantitative detection of biothiols.This sensor realized sensitive detection of biothiols with high selectivity.The sensor showed a good linear relationship with Glutathione（GSH）ranging from 0.5?M-7?M,and the detection limit could reach 59 nM.Furthermore,the detection limits of Cysteine（Cys）and Homocysteine（Hcy）were 47 nM and 28 nM,respectively.More importantly,ratiometric probes can avoid false positive signals and provide more real and reliable results.（3）In chapter 4,silver nanoparticles（AgNPs）-cationic UV waterborne polyurethane composite coating was prepared by one-step method,and its antibacterial properties were studied.AgNPs was a recognized inorganic antibacterial agent,and the quaternary ammonium salt in cationic waterborne polyurethane was a kind of organic antibacterial agent.In-situ formation of AgNPs and coating solidification was obtained through a simple UV irradiation.Both the organic and inorganic antibacterial sites would achieve enhanced antibacterial effect.The morphology and properties of composites were characterized by Transmission electron microscope（TEM）and Flourier transformation infrared spectrometer（FTIR）.The antimicrobial properties of the coating were tested by Minimum inhibitory concentration（MIC）,antibacterial efficiency-time curve and repeated antimicrobial activity.The results showed that the as-prepared composite coating exhibited remarkable antibacterial activity against Escherichia coil（E.coli）and Bacillus subtilis（B.S.）.The preparation method is simple,efficient and green,which can provide a new idea for the preparation of AgNPs-based antimicrobial nanocomposites. |
