The Synthesis, Characterization And Application Of Fluorescent Nanomaterial

In the fields of biology and medicine, the fluorescence labeling technique hasbeen the essential tool for studying on the configuration of biological macromolecules,the interaction between biological molecules and the action mechanism of nanocarrierinto the cell in the systems of nano-drug delivery. It has been the third "eyes" forresearcher to observe biological phenomena. The synthesis of fluorescent materialspossessing excellent properties is crucial for promoting the development and progressof fluorescence labeling. Generally, the luminescent materials for biological labelinginclude organic dyes, semiconductor quantum dots, composite fluorescentnanoparticles and noble metal nanoclusters. The latter three, owing to their size innano-level, are well known as the novel luminescent nanomaterials. Owing to theexcellent photostability, the luminescent nanomaterials attract many researchers andbecome the next generation of luminescent makers. Here, we mainly discuss thepreparation and application of the dye doped polymer nanoparticles and noble metalnanoclusters. Composite strategies, concentration and mechanism among nano-matrices, dye molecules and the structure of prepared luminescent nanoparticles havegreat impact on the luminescent properties of composite luminescent nanoparticles. Itis significant for us to figure out how the above factors affect the luminescentproperties of composite luminescent nanoparticles. And it will helpful for people toprepare composite luminescent nanoparticles for more excellent properties. Noblemetal nanoclusters have great applicable prospect in the biological fields owing totheir predominant photostability, larger Stoke shift and good biocompatibility. Silvernanoclusters present stronger fluorescence than Au nanoclusters in aqueous solution.Due to the chemical instability and the high surface energy of silver nanoclusters, theytended to interact with each other and had a natural tendency to aggregate, forminglarger nanoparticles. Therefore, a proper stabilizing scaffold or template is thusindispensable. The choices of novel, functional template or stabilizing scaffold havegreat impact on the properties and the optional application areas of silvernanoclusters. According to the excellent luminescent properties and application prospects of the Ag nanoclusters embedded composite luminescent nanoparticles, themain research contents are summarized as follows:1, The studies on the preparation of dye doped PMMA nanoparticles and theirluminescent properties and applications.A dye, Ru(bpy)3Cl2, was combined with nano-matrices PMMA (polymethylmethacrylate) by two strategies as the embedding (Em-PMMA nanopartcles) and theadsorbing (Ad-PMMA nanoparticles) approaches to obtain the novel compositeluminescent nanoparticles. The fluorescence lifetime of two kinds of compositeparticles can tell us that both them have a core-shell structure. For the Em-PMMAnanopartcles,40%of dye molecules lied in the surface of nanoparticle and60%ofdye molecules located in the inner of nanoparticles; For Ad-PMMA nanoparticles,16%of dye molecules lied in the inner of nanoparticles and84%of dye molecules onthe surface of nanoparticles. The quantum yields of dye molecules increased after theycombining with PMMA nanoparticles. The luminescent intensity of the Em-PMMAnanopartcles was higher than that of Ad-PMMA nanoparticles when containing thesame amount of dye molecules. The resisting ability for outside adverse environmentshowed the Em-PMMA nanopartcles was much stronger than the Ad-PMMAnanoparticles. The surface potentials of PMMA nanoparticles can be adjusted bychoosing different initiators. We found that the positively charged Ru(bpy)3Cl2can beintegrated with the negatively charged PMMA nanoparticles while they can not becombined with the positively charged, which suggested that it was the electrostaticattraction that drove the combination of dye molecules and nano-matrices. For thenano-matrices of adjustable surface potentials, the options of dye molecules which canbe combined with nano-matrices have been expanded. The negatively chargedfluorescein sodium and negatively charged rhodamine6G were combined withPMMA nanoparticles with different surface potentials. Similarly, the mechanism fordye molecules encapsulating in the PMMA nano-matricesm was the electrostaticattraction. The composite strategies and the concentration of dye molecules wereoptimized. Finallymulticolored and high brightness dye@PMMA nanocompositeswere prepared. And these multicolored polymer nanoparticles can easily stain bloodcancer cells without further surface modification.2, In situ synthesis of silver nanoclusters templated by the carboxylated polymernanoparticles with the core-shell structure.The method of soapless seeded emulsion polymerization was applied for synthesizing the core-shell polymer nanoparticles. The core of these polymernanoparticles were PMMA (polymethyl methacrylate), PS (polystyrene) and SiO2(silicon dioxide) respectively and all of the composition of shell was made of PMAA(polymethacrylic acid). The water-soluble fluorescent Ag nanoclusters were preparedby the method of photochemical reduction using the template of these carboxylatedpolymer nanoparticles. The pH values of reaction solution and the ratios of carboxylgroups and AgNO3were proved to be important for the synthesis process of silvernanoclusters that. The quantum yield of Ag nanoclusters was6-12%. There was awide distribution of the number of Ag atoms consisting of Ag2-6. When using thecore-shell carboxylated polymer nanoparticles as the templates for in situ synthesis ofAg nanoclusters, the composition of Ag nanoclusters and polymer nanoparticles canbe realized in one-step reaction, which is helpful to extend the application ranges ofAg nanoclusters. And the stability of Ag nanoclusters was enhanced when combiningwith polymer nanoparticles. The Ag nanoclusters can maintain the originalfluorescence intensity even experiencing one year storage. Owing to the protecting ofpolymer nanoparticles, the ability of resisting outside adverse environment wasimproved. The prepared Ag nanoclusters@polymer nanoparticles had successfullybeen applied for bioimaging.3, Synthesis and characterization of Ag nanoclusters templated bycarboxymethyl-β-cyclodextrin (CM-β-CD)The CM-β-CD molecules with different degree of substitution of carboxylicgroups were synthesized and they were applied as the template for preparing Agnanoclusters. The experiment showed that the more degree of substitution ofcarboxylic groups, the better for formation of Ag nanoclusters. When the degree ofsubstitution of carboxylic groups on per β-cyclodextrin molecule was smaller than4,the prepared Ag nanoclusters was very instability, tending to aggregate and led to theformation of Ag nanoparticles. It played an important role during the synthesisprocess of silver nanoclusters that the pH of reaction solution and the ratio of carboxylgroups and AgNO3and these reaction conditions were optimized for obtaining higherbrightness. Although the quantum yield of Ag nanoclusters templated by smallmolecules was low, just2%, the natural properties of Ag nanoclusters were notaffected by CM-β-CD. The Ag nanoclusters templated by CM-β-CD was used as anew antibacterial reagent and found that the antibacterial ability of Ag nanoclusters was stronger than Ag ions and typical Ag nanoparticles owing to the high surfaceenergy of Ag nanoclusters.4, In situ synthesis of silver nanoclusters on modified silk via ultravioletlight-induced reductionThe silk modified by PAA was used as a template to prepare Ag nanoclusterssuccessfully. We developed a novel template for synthesizing Ag nanoclusters. It notonly realized the in situ synthesis of Ag nanoclusters but also finished the combinationof Ag nanoclusters and silk fibres and the completion of function of silk. This is a newsynthesis way for fluorescent silk. Since in China, silk has been used as a luxurytextile material over3000years owing to their excellent properties such as moistureabsorption, oxygen permeability, heat retention and outstanding mechanical properties.In addition, in many biomedical fields such as cell culture scaffolds, artificial bonematrices and controlled drug release, the silkworm silk has been proved to be asuitable candidate. However, this protein fiber has the potential to be a hospitable hostfor the generation and propagation of microorganisms, resulting in fiber damages andskin irritations. So the antimicrobial ability of silk fibers has been concerned. By thein situ growth of Ag nanoclusters on silk fibers modified by the polymer polyacrylicacid (PAA), we obtained a novel silk fibre with luminescence and antibacterialactivity. This method is also applicable for most natural and artificial fibres.Comparing with green fluorescent protein doped silk fibre, this is a easily handled,low-cost and less time-consuming method for preparing fluorescent silk fiber. Theproduced Ag nanoclusters@silk fibres were expected to exhibit good antibacterialproperty.