| Silver nanoparticles (AgNPs) have many unique properties compared to bulky silver becauseof its quantum size effect, large specific surface area and high surface energy, such as catalyticactivity for some reactions. Comparing with other metal nanoparticles with catalytic activity, suchas Pt nanoparticles and Pd nanoparticles, AgNPs can be prepared more readily and inexpensively,so they have an attractive application prospect as catalyzer. However, like other nanoparticles, Agnanoparticles are prone to aggregating due to their high surface energy, with loss of their catalyticactivity. If AgNPs are loaded into intelligent microgel, their aggregation can not only be avoided,but they can be reused through recycling. Moreover, their catalytic activity can be controlled byexternal stimuli, so the chemical reactions can proceed at an appropriate reaction rate. In thisthesis, AgNPs are loaded into light responsive microgels, their catalytic activity can be adjusted bylight irradiating on the formed hybrid microgels. Comparing to AgNPs loading temperatureresponsive hybrid microgels, the catalytic activity of the AgNPs within light responsive hybridmicrogels is easier to control, with faster switch between ‘on’ and ‘off’ and without the sidereaction coming from reaction temperature change. The major research works and obtained resultsof the thesis include the following three aspects.(1) The gold nonarods (AuNRs) with narrow monodispersity were synthesized by seedgrowth method using a binary surfactant mixture composed of hexadecyltrimethylammoniumbromide (CTAB) and sodium oleate (NaOL). Their aspect ratio is increased with the increase ofthe used amount of AgNO3or concentrated HCl acid in their synthesis recipe. The AuNRs werecharacterized by ultraviolet-visible-near infrared (UV-vis-NIR) absorption spectrum andtransmission electron microscopy (TEM), and their aspect ratio calculated from their longitudinallocalized surface plasmon resonance (LSPR) wavelength obtained by UV-vis-NIR is nearly inagreement with the statistical result from TEM measurment. In addition, by comparing thecharacterization results obtained by the two methods, it can be found that, the narrowerlongitudinal LSPR absorption peak of the AuNRs, the better their size monodispersity. Furthermore, their greater intensity ratio of longitudinal and transverse LSPR absorption peaksimplies less content of spherical Au nanoparticles in the syntheized AuNRs. The measurementresults from thermal infrared imager show that their photothermal effect is enhanced with thereducing difference between their longitudinal LSPR wavelength and the wavelength of the lightirradiating upon the AuNRs.(2) The hybrid microgels (AuNR@(AgNPs/PNIPAM) hybrid microgels) based on AuNR ascore and AgNPs loading poly(N-isopropylacrylamide)(PNIPAM) hydrogel as shell were preparedby seed precipitation polymerization, followed by in-situ reduction reaction. The result by TEMshows that the AuNR is located in the center of the microgel and AgNPs with the average particlesize in the range of7~11nm are evenly distributed within their shell. The results by dynamic laserlight scattering (DLS) indicate that the hybrid mirogels have not only temperature stimuliresponsiveness but light stimuli responsiveness. The AgNPs and AuNR inside the hybrid microgelhold their LSPR optical property, and the longitudinal LSPR wavelength of the AuNR is graduallyblue-shifted with the increase of their AgNPs content. The LSPR absorption peak intensity of theAgNPs and the longitudinal LSPR wavelength of the AuNR can reversibly be changed in responseto the environmental temperature change or near-infrared light irradiation.(3) The produced hybrid microgels can be used as the microreactor of the reduction reactionof4-nitrophenol by NaBH4. The reaction rate can be controlled by the power of near-infraredirradiation, that is to say, the catalytic activity of the AgNPs within the hybrid microgels can beadjusted by light stimulus. |
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