Novel Fluorescence Sensing System Based On Self-assembled Polymer Micelles

Fluorescence sensing technology with high sensitivity, good selectivity, less samplerequirement, easy handling and short detection timehas established great potential ofapplication in the fields of materials science, life science and environmental science. Sensingmaterials used in fluorescence sensing technology mainly include inorganic luminescentnanomaterials, organic small molecular dyes and fluorescent conjugated polymers. Amongthem, amplifying fluorescent conjugated polymers and semiconductor quantum dots (QDs)have emerged as the most promising chemical sensing materials because of their distinctadvantages, such as good stability, adjustable emitting color, high quantum yields, et al.However, most commercial high-quality conjugated polymers and QDs are hydrophobic andcan only be dissolved in organic solvents, which limits their applications in the aqueousmedia. Amphiphilic polymerwith both hydrophobic and hydrophilic groups can self-assembleto form nanomicelles in aqueous solution. These self-assembled nanomicelles can be used asthe carrier of hydrophobicconjugated polymers and semiconductor QDs, thus expandingtheapplications of the luminescent sensing materials. The sensing systems based onpolymericnanomicelles show high sensitivity and good selectivity. In addition, the preparationof polymericnanomicelles based fluorescent probe is simple and easy handling.Therefore,they exhibit great potential in the fields of biology, materials,chemistry and medicine. In thisthesis, three novel fluorescent sensing systems based on self-assembled polymer nanomicelleswere developed, and their applications in the ultrasensitivedetection of nitrobenzeneexplosives, Sudan dye and metal ions were studied. A series of innovative researches werecarried out as follows:1. The common commercially available light-emitting conjugated polymers poly (9,9-dioctylfluorene)(PFO) and poly[2,7-(9,9-dihexylfluorene)-alt-4,4’-phenylether](PFPE)were easily dispersed into water by efficiently encapsulated them in the amphiphilic blockpolymer F127nanomicelles. A novel fluorescent sensing system based on F127nanomicelleswas constructed simply and conveniently. The PFO and PFPE-containing nanomicelles weresuccessfully used to detect nitroaromaticexplosives, such as2,4,6-trinitrophenol (picric acid, PA) and2,4-dinitrotoluene (DNT) in aqueous solution. The Stern-Volmer constants (Ksv) ofconjugated polymers in nanomicelles for PA and DNT were75048M-1and8305M-1(PFO),59984M-1and2845M-1(PFPE) respectively, much higher than that in organic solvent, whichmeans F127nanomicelles can improve the sensitivity of nitroaromaticexplosives detection. Itplays a significant role in developing novel chemical sensors.2. The novel amphiphilic chitosan-based copolymer with excellent biocompatible andbiodegradable properties was homogeneously prepared in the green solvent of ionic liquid bygrafting biocompatible and biodegradable polydioxanone (PPDO) onto the backbone ofchitosan water-soluble derivative carboxymethyl chitosan through the ring openingpolymerization. It was found that the amphiphilic chitosan-based copolymer canself-assemble into core-shell structured nanomicelles in aqueous solution.Conjugated polymerPFO was successfully encapsulated into the cores of carboxymethyl chitosan graftpolydioxanone (CMCs-g-PPDO) nanomicelles without any modification, and thus a new typeof chitosan-based polymer micelles fluorescence sensing system was built. The detection ofSudan I and natural pigments showed that the fluorescence sensing system can selectively andsensitively detect Sudan I. The Ksv value of PFO in nanomicelles for Sudan I was1.74×107M-1. The CMCs-g-PPDO/PFO functionalized indicator paper was further simplyprepared byadding CMCs-g-PPDO/PFO micelles solution on the surface of paper.The application regionof light-emitting conjugated polymers was extended by this way. Potentially, this methodproposed in this part may be applied in the food additives safety field.3. A novel fluorescent amphiphilic cellulose-based nanoaggregates were successfullyprepared by the encapsulation of hydrophobic inorganic quantumdots (QDs) into the cellulosegraft polydioxanone (MCC-g-PPDO) nanomicelles. The optical properties of the QDs werewell kept, and they were easily dispersed in water after encapsulation. The QDs encapsulatedMCC-g-PPDO nanomicelles were applied in sensing a variety of metal ions. It was found thatthe novel fluorescent sensing system can selectively detect Cu2+. The limit of detection forCu2+was1nM, which is promising to apply in the environmental field.