| Stimuli-responsive materials are capable of exhibiting reversible or irreversiblechanges in physical properties and/or chemical structures to small changes inexternal environment. They can adapt to surrounding environments, regulatetransport of ions and molecules, change wettability and adhesion of different specieson external stimuli, or convert chemical and biochemical signals into optical,electrical, thermal and mechanical signals, and vice versa. In the recent studies, theresponsive polymer micro-system attracts extensive interests and has become aresearch highlight. As water-soluble and temperature-responsive polymers, PNIPAMand its copolymers have been extensively studied.As a sensitive and convenient analytic technique, fluorescence detection hasbeen widely used in molecular recognition, bio-labeling, cell imaging and otherfields, and becomes an essential detection mean in chemical and biological fields. Byintroducing fluorescent molecules with aggregation-induced emission (AIE) propertyand fluorescent carbon quantum dots into responsive polymers, we can construct aresponsive polymer micro-system and try to exhibit their potential application indetections for ions, pH, explosive and so on.In Chapter2, we design a dual emission polymer nanoparticles responsing topH and temperature. The core-shell polymer nanoparticles (PS/PNIPAM-co-PAA)are synthesized. Two kinds of photoluminescent molecules with similar excitationwavelengths, a rare earth complex with red emission and a quaternary ammoniumtetraphenylethylene derivative (d-TPE) with blue emission, are inserted intopolymeric core and shell, respectively. The PL intensities of the nanoparticles exhibita linear temperature response in the range of10and80oC with a change by a step ofa factor of5. Furthermore, blue emission from the shell exhibits a linear pH response between pH6.5and7.6with a resolution of0.1unit, as well as the red emission fromthe core is constant from pH-independance. Accordingly, the hydrogel nanoparticlesshow different purple and red coloration in neutral and acidic environments,enabling the discrimination of healthy (pH7.4) and cancer cells (pH6.5),respectively. These stimuli-responsive PL nanoparticles have potential application inbiology and chemistry, including bio-and chemo-sensors, biological imaging, cancerdiagnosis, and externally activated release of anticancer drugs.In Chapter3, in order to extend the study on responsive polymer micro-system,we improve a kind of nanoparticles with biocompatibility and cell targeting. Folicacid (FA) is brought to synthesize fluorescent carbon quantum dots for selectiveimaging of specific cancer cells. A simple, low-cost and one-step microwaveapproach has been demonstrated for the synthesis of water-soluble carbon dots(C-dots). The average size of the resulting C-dots is about4nm. From thephotoluminescence (PL) measurements, the C-dots exhibit good stability and intensePL with the high quantum yield (QY) at Ca.25%. Significantly, the C-dots haveexcellent biocompatibility and selective imaging for folate receptor (FR)-positivecancerous cells from normal cells. These exciting results indicate the as-preparedC-dots are promising biocompatible probe for cancer diagnosis and treatment.Further, gadolinium ions [Gd (III)] are interacted with the carboxyl of carbon dots toprepare a modified nanodot (Gd/C dot). Due to the magnetic properties from Gd (III)and fluorescent properties from carbon dots, the modified carbon dots withdual-function are obtained, which can be applied on dual-channel of fluorescenceand magnetic imaging.In Chapter4, we design to transfer our responsive polymer system into films tofabricate multi-functional sensitive devices. First, we prepared thethermo-responsive photoluminescent (PL) polymer brushes device as a platform forselective and sensitive detection of Cr (VI). As positive charged fluorescentmolecules of quaternary ammonium, tetraphenylethylene derivatives (d-TPE)molecules are immobilized in the thermo-responsive polymer brushes of PNIPAM-co-PAA by coloumb force, which leads to the observation of immobilizedinduced emission (IIE) phenomenon. The emission intensity is improved hundreds oftimes comparing with d-TPE aqueous solution. As a result, we obtain a novelthermo-responsive PL polymer brushes film device. The PL intensity of the deviceexhibits linear and reversible response in a large temperature range (4-60°C) andshows a highly PL quenching for sensitive and selective detection of Cr (VI) ratherthan Cr (III), the limit of detection can reach as low as0.05ppm, which indicates apromising sensor device of thermometer for environmental monitoring, laboratoryanalysis and other various applications.Moreover, we prepared the fluorescent polymer brushes film as a device forultrasensitive and selective detection of TNT. As positive charged fluorescentmolecules of quaternary ammonium tetraphenylethylene derivatives (d-TPE) wereself-assembled on the brushes of poly(acrylic acid)(PAAc) by coulomb force, weobtained a novel fluorescent polymer brushes film with excellent photoluminescenceproperties, and the emission intensity could be quantitatively and sensitivelyresponsive to2,4,6-trinitrotoluene (TNT) due to the electron transfer between d-TPEand TNT. The limit of detection of TNT was established to be0.1ppb in water. Thefluorescent device could also be used repeatedly for TNT detection, which indicateda promising application in trace explosive detection, environmental monitoring, andlaboratory analysis, etc. |
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